Heterojunction fabrication and noble metal deposition serving as efficacious means for promoting photocatalytic activity attract huge interests. Here, a series of ternary Ag/AgBr/BiOIO3 composite photocatalysts that integrate the above two aspects are prepared by in situ crystallization of Ag/AgBr on BiOIO3. The photocatalytic performance is first investigated by degrading MO with visible light and UV light irradiation. The results indicate that Ag/AgBr/BiOIO3 composites present strengthened photocatalytic activity compared with BiOIO3 and Ag/AgBr under both light sources. Distinct activity enhancement levels corresponding to different mechanisms with UV and visible light illumination are uncovered, which are closely related to the applied light source. The universal catalytic activity of Ag/AgBr/BiOIO3 is surveyed by decomposition of diverse antibiotics and phenols, including tetracycline hydrochloride, chlortetracycline hydrochloride, bisphenol A, phenol, and 2,4-dichlorophenol which discloses that this ternary heterojunction photocatalyst demonstrates unselective catalytic activity with universality. Importantly, Ag/AgBr/BiOIO3 displays a strong mineralization ability, completely decomposing BPA into CO2 and H2O. This work affords a new reference for designing heterojunction photocatalyst with multiple advantageous effect and powerful capability for environmental purification.Keywords: AgBr; Antibiotics; BiOIO3; Phenols; Photocatalysis; SPR;

Monolayered photocatalytic materials have attracted huge research interests in terms of their large specific surface area and ample active sites. Sillén-structured layered BiOX (X = Cl, Br, I) casts great prospects owing to their strong photo-oxidation ability and high stability. Fabrication of monolayered BiOX by a facile, low-cost, and scalable approach is highly challenging and anticipated. Herein, we describe the large-scale preparation of monolayered BiOBr nanosheets with a thickness of ∼0.85 nm via a readily achievable liquid-phase exfoliation strategy with assistance of formamide at ambient conditions. The as-obtained monolayered BiOBr nanosheets are allowed diverse superiorities, such as enhanced specific surface area, promoted band structure, and strengthened charge separation. Profiting from these benefits, the advanced BiOBr monolayers not only show excellent adsorption and photodegradation performance for treating contaminants, but also demonstrate a greatly promoted photocatalytic activity for CO2 reduction into CO and CH4. Additionally, monolayered BiOI nanosheets have also been obtained by the same synthetic approach. Our work offers a mild and general approach for preparation of monolayered BiOX, and may have huge potential to be extended to the synthesis of other single-layer two-dimensional materials.Keywords: BiOBr; CO2 reduction; Liquid-phase exfoliation; Monolayered nanosheets; Photodegradation;

A series of novel heterojunctional photocatalysts BiOBr0.75I0.25/BiOIO3 were synthesized by a facile deposition–precipitation method for the first time. In contrast to pristine BiOIO3, the photoabsorption of BiOBr0.75I0.25/BiOIO3 composites in visible light region is greatly promoted. All the BiOBr0.75I0.25/BiOIO3 composite photocatalysts exhibit highly enhanced photocatalytic activity in decomposing bisphenol A under visible light (λ > 420 nm) illumination, and the 20% BiOIO3-BiOBr0.75I0.25 sample possesses the optimal photoreactivity, which is 7.4, and 3.3 times higher than those of pure BiOIO3 and BiOBr0.75I0.25. Moreover, the 20% BiOIO3-BiOBr0.75I0.25 sample displays superior photocatalytic performance against diverse industrial contaminants and pharmaceuticals, including methyl orange, phenol, 2,4-dichlorophenol, chlortetracycline hydrochloride, and tetracycline hydrochloride. The enhancement of phototcatalytic activity is ascribed to the profoundly promoted transfer and separation of photoexcited charge carriers, which is verified by transient photocurrent response and photoluminescence emission. In addition, the photocatalytic mechanism over composite photocatalyst under visible light irradiation is systematically investigated by active species trapping experiment and •OH quantification experiment. This work may provide a new hint for fabrication of high-performance heterojunctions by combining the narrow-band gap and wide-band gap semiconductors.Keywords: BiOBr0.75I0.25; BiOIO3; Diverse industrial pollutants; Heterostrucure photocatalyst; Visible-light;

Different samples of gadolinium (Gd)-doped Bi2WO6 were obtained by hydrothermal means, and their photocatalytic activities for degradation of rhodamine B (RhB) under visible-light irradiation were researched. The successful incorporation of Gd3+ ions into Bi2WO6 was detected by XRD and XPS, and the prepared samples have also been characteriazed by SEM, TEM, HRTEM, DRS, and PL. The results suggested that Gd doping has great influences on the visible-light photocatalytic activity as well as the microstructure. Appropriate doping content greatly improve photocatalytic activity due to the electron shallow-trapping mechanism for the efficient separation of electron and hole pairs, and the 1% Gd–Bi2WO6 sample with flower-like structure exhibited the highest photocatalytic activity. It has already been confirmed by photocurrent generation and electrochemical impedance spectra. The present research provides a simple and valid method for improving the visible-light-responding photocatalytic activity and fabricating hierarchical architectures of Bi2WO6.

Photocatalytic CO2 reduction into solar fuels illustrates huge charm for simultaneously settling energy and environmental issues. The photoreduction ability of a semiconductor is closely correlated to its conduction band (CB) position. A homogeneous-phase solid-solution with the same crystal system always has a monotonously changed CB position, and the high CB level has to be sacrificed to achieve a benign photoabsorption. Herein, we report the fabrication of heterogeneous-phase solid-solution ZnXCa1–XIn2S4 between trigonal ZnIn2S4 and cubic CaIn2S4. The ZnXCa1–XIn2S4 solid solutions with orderly tuned photoresponsive range from 540 to 640 nm present a more negative CB level and highly enhanced charge-separation efficiency. Profiting from these merits, all of these ZnXCa1–XIn2S4 solid solutions exhibit remarkably strengthened photocatalytic CO2 reduction performance under visible light (λ > 420 nm) irradiation. Zn0.4Ca0.6In2S4, bearing the most negative CB position and highest charge-separation efficiency, casts the optimal photocatalytic CH4 and CO evolution rates, which reach 16.7 and 6.8 times higher than that of ZnIn2S4 and 7.2 and 3.9 times higher than that of CaIn2S4, respectively. To verify the crucial role of the heterogeneous-phase solid solution in promoting the band structure and photocatalytic performance, another heterogeneous-phase solid-solution ZnXCd1–XIn2S4 has been synthesized. It also displays an upshifted CB level and promoted charge separation. This work may provide a new perspective into the development of an efficient visible-light driven photocatalyst for CO2 reduction and other photoreduction reactions.Keywords: band structure; charge separation; crystal system; photocatalytic CO2 reduction; ZnXCa1−XIn2S4;

•Cl intercalated g-C3N4 is obtained via pyrolysis of melamine and excessive NH4Cl.•Cl intercalation endows g-C3N4 with multiple superiorities.•It shows significantly enhanced photoreduction and photooxidation performance.•The Cl intercalation advantages are confirmed by experiments and DFT calculations.Metal-free graphitic carbon nitride (g-C3N4) shows tremendous potentials in energy and environmental domains. Nonetheless, amelioration on the crystal configuration, electronic structure and microstructure of g-C3N4 for high-performing visible-light photocatalysis is still challenging and anticipated. Here we report the development of chlorine (Cl) intercalated g-C3N4 via co-pyrolysis of melamine and excessive ammonium chloride (excessive is very pivotal). This protocol renders not only Cl intercalation in the interlayer of g-C3N4, but also a homogeneous porous structure, thereby endowing g-C3N4 with multiple superiority effects, including significantly promoted charge migration by establishing interlayer pathway, up-shifted conduction-band level, narrowed band gap as well as enhanced surface area. The as-prepared Cl intercalated mesoporous g-C3N4 parades outstanding photocatalytic performance for water splitting into H2, CO2 reduction, liquid and air contaminants removal. The most enhanced photocatalytic performance was obtained at Cl-C3N4-3 for H2 evolution activity, which shows a 19.2-fold increase in contrast to pristine g-C3N4, accompanying with a high apparent quantum efficiency of 11.9% at 420 ± 15 nm. Experimental and DFT calculations results co-disclose that the aforementioned advantageous factors account for the profoundly boosted photooxidation and photoreduction capabilities of g-C3N4 under visible light. The present work may furnish a bottom-up tactic for integrally advancing g-C3N4, and also hold huge promise to be extended to other layered materials for photochemical or photoelectrochemical applications.Download high-res image (140KB)Download full-size image

•Polyurethane foam (PUF) based bismuth oxyhalides photocatalysts are synthesized.•BiOX/PUF shows enhanced photodegradation activity for dye, phenol and antibiotic.•BiOX/PUF foams also show improved photocatalytic H2 evolution rate.•BiOX/PUF foams display easy recovery, good recycling and excellent controllability.Photocatalysis currently remains a series of key challenges, such as difficult recovery of powder, low efficiency, etc, which grievously impede the practical application of powdery photocatalysts in environmental remediation and renewable energy generation. In this work, we integrate a flexible and porous organic matrix polyurethane foam (PUF) with nanosheet-array-like bismuth oxyhalides (BiOX) as efficient and stable photocatalysts via a facile dipping-hydrolysis means. The BiOX/PUF foam photocatalysts uncover profoundly promoted photocatalytic performance for treating multiform organic contaminants ranging from azo dye, phenol to antibiotic, in comparison with the powdery counterparts. These foam photocatalysts also display enhanced photocatalytic activity toward water splitting into H2 evolution. Significantly, they show absorbing performance in many aspects, including high stability, easy recovery, good recycling and excellent controllability and adaptability, strongly boding for their promising practical prospect. The study may not only advance a series of practical photocatalysts for environmental control and renewable energy generation, but also have the potential to be extended to development of other high-performance photocatalytic materials.Download high-res image (183KB)Download full-size image

•Ag-AgI-AgIO3 multiplex heterostructural photocatalysts are fabricated.•The composite photocatalysts exhibit strong absorption in visible region.•The composites show outstanding photocatalytic activity against diverse pollutants.•Ag-AgI-AgIO3 can effectively convert CO2 to CO.Utilizing self-sacrificed transformation of the dual redox couples Ag/Ag+ and I−/(IO3)−, we developed a multiplex heterostructure Ag-AgI-AgIO3 by using a simple in-situ reduction strategy and AgIO3 as the sacrificed template. The reaction extent can be easily controlled via adjusting the reductant NaBH4 concentration. Benefiting from both Ag SPR and heterojunctional effects, the photoabsorption in the UV–vis region of Ag-AgI-AgIO3 is monotonously enhanced with increasing reductant concentration. The composite photocatalysts all exhibit highly enhanced photocatalytic activity in degrading methyl orange (MO) under both UV light and visible light irradiation, and Ag-AgI-AgIO3-5 sample shows the optimal photoreactivity, which is 15.2 times that of pure AgIO3. Notably, it also possesses unsurpassed photocatalytic activity against diverse industrial contaminants, pharmaceuticals, and gaseous NO. Besides, Ag-AgI-AgIO3-5 also displays better photocatalytic performance in converting CO2 to CO than AgIO3. Particularly, we explore the reduction products of AgIO3 by other different reductants. It is fascinating that the introduction of sodium citrate, thiourea and hydrazine hydrate results in the products Ag-AgIO3, AgI-AgIO3, Ag-AgI-AgIO3 composites, respectively. This work may not only offer a universally powerful and stable photocatalyst for environmental and energy applications, but also open up a new avenue to develop component-adjustable polynary heterostructural photocatalysts in a facile way.Download high-res image (125KB)Download full-size image

AbstractEfficient photo- and piezoelectric-induced molecular oxygen activation are both achieved by macroscopic polarization enhancement on a noncentrosymmetric piezoelectric semiconductor BiOIO3. The replacement of V5+ ions for I5+ in IO3 polyhedra gives rise to strengthened macroscopic polarization of BiOIO3, which facilitates the charge separation in the photocatalytic and piezoelectric catalytic process, and renders largely promoted photo- and piezoelectric induced reactive oxygen species (ROS) evolution, such as superoxide radicals (.O2−) and hydroxyl radicals (.OH). This work advances piezoelectricity as a new route to efficient ROS generation, and also discloses macroscopic polarization engineering on improvement of multi-responsive catalysis.

AbstractEfficient photo- and piezoelectric-induced molecular oxygen activation are both achieved by macroscopic polarization enhancement on a noncentrosymmetric piezoelectric semiconductor BiOIO3. The replacement of V5+ ions for I5+ in IO3 polyhedra gives rise to strengthened macroscopic polarization of BiOIO3, which facilitates the charge separation in the photocatalytic and piezoelectric catalytic process, and renders largely promoted photo- and piezoelectric induced reactive oxygen species (ROS) evolution, such as superoxide radicals (.O2−) and hydroxyl radicals (.OH). This work advances piezoelectricity as a new route to efficient ROS generation, and also discloses macroscopic polarization engineering on improvement of multi-responsive catalysis.

•Bi4Ti3O12 was synthesized by a one-pot hydrothermal process and sol-gel method.•Diverse morphologies are obtained by manipulating the mineralizer concentration.•Bi4Ti3O12 shows universal photoreactivity for removing contaminants and antibiotics.•It shows ultrasonic-assisted piezoelectric-catalysis for MO degradation.•Superoxide and hydroxyl radicals take effects in the piezoelectric-catalytic process.Development of multi-responsive catalytic materials is a highly meaningful and challenging subject for forwarding the understanding on catalysis mechanism. In this work, we for the first time disclose the piezoelectric-catalytic performance and morphology-dependent photocatalytic activity of Bi4Ti3O12. Via introducing and manipulating the mineralizer sodium hydroxide, we developed a series of Bi4Ti3O12 catalysts with diverse morphologies, including nanorods, slice-assembled microspheres, nest-like hollow microspheres, and cube assembly. The photocatalytic activity of these hydrothermally-yielded Bi4Ti3O12 as well as sol-gel derived Bi4Ti3O12 is investigated by degradation of phenol, and the photocatalytic mechanism is explored. The Bi4Ti3O12 microsphere exhibits the most efficient degradation activity, and also presents universal photoreactivity for removing multiform contaminants and antibiotics, like bisphenol A, rhodamine B, chlorotetracycline and tetracycline hydrochloride, boding for its promising practical applications. Significantly, Bi4Ti3O12 demonstrates a high piezoelectric-catalytic performance for ultrasonic-assisted decomposition of methyl orange, bisphenol A and tetracycline hydrochloride. It is uncovered that both powerful superoxide (O2−) and hydroxyl (OH) radicals are generated with production rates of 6.4 and 2.4 μmol g−1 h−1, respectively, which take crucial roles in the piezoelectric-catalytic process. The corresponding mechanism is tentatively speculated. This work may push forward to the development of multi-responsive catalytic materials, and provide insights into piezoelectric-catalysis for environmental applications.Download high-res image (174KB)Download full-size image

•Single-unit-cell layer established 3D Bi2WO6 by SDBS-assisted assembled strategy.•It shows a strong selectivity for adsorption on positively-charged organic dyes.•It presents highly enhanced photocatalytic activity for degradation and H2 evolution.•Systematic photoelectrochemical experiments confirm the promoted charge separation.•Single-unit-cell 3D Bi2WO6 is a promising dye-sensitized photoanode for ORR.Single-layer catalysis sparks huge interests and gains widespread attention owing to its high activity. Simultaneously, three-dimensional (3D) hierarchical structure can afford large surface area and abundant reactive sites, contributing to high efficiency. Herein, we report an absorbing single-unit-cell layer established Bi2WO6 3D hierarchical architecture fabricated by a sodium dodecyl benzene sulfonate (SDBS)-assisted assembled strategy. The DBS− long chains can adsorb on the (Bi2O2)2+ layers and hence impede stacking of the layers, resulting in the single-unit-cell layer. We also uncovered that SDS with a shorter chain is less effective than SDBS. Due to the sufficient exposure of surface O atoms, single-unit-cell layer 3D Bi2WO6 shows strong selectivity for adsorption on multiform organic dyes with different charges. Remarkably, the single-unit-cell layer 3D Bi2WO6 casts profoundly enhanced photodegradation activity and especially a superior photocatalytic H2 evolution rate, which is 14-fold increase in contrast to the bulk Bi2WO6. Systematic photoelectrochemical characterizations disclose that the substantially elevated carrier density and charge separation efficiency take responsibility for the strengthened photocatalytic performance. Additionally, the possibility of single-unit-cell layer 3D Bi2WO6 as dye-sensitized solar cells (DSSC) has also been attempted and it was manifested to be a promising dye-sensitized photoanode for oxygen evolution reaction (ORR). Our work not only furnish an insight into designing single-layer assembled 3D hierarchical architecture, but also offer a multi-functional material for environmental and energy applications.Download high-res image (194KB)Download full-size image

•A precursor-recrystallization strategy was first employed to obtain advanced g-C3N4.•It shows 3D mesoporous structure established by ultrathin N self-doped nanosheets.•It shows enhancement on surface area, photoabsorption and charge separation.•A superior photocatalytic H2 evolution rate of 3579 μmol h−1 g−1 was achieved.•The apparent quantum efficiency is as high as 27.8% at 420 nm.Graphitic carbon nitride (g-C3N4) has attracted enormous research attention as a promising low cost, visible-light driven semiconductor photocatalyst. However, low photoabsorption efficiencies and unsatisfactory charge separation limit the potential of g-C3N4 in many applications, motivating attempts to manipulate the structure and electronic properties of g-C3N4 to achieve improved performance. Here we describe a novel precursor-reforming strategy that ultimately affords 3D mesoporous ultrathin g-C3N4 with superior photocatalytic performance compared to conventional calcination-derived g-C3N4. We demonstrate that during hydrothermal treatment of melamine and urea, melamine undergoes an irreversible monoclinic to orthorhombic phase transformation, and the additive urea (excess typically 3-fold) serves as an additional N source and porogen. Calcination of the orthorhombic melamine yields mesoporous g-C3N4 with enhanced photoabsorption properties and an outstanding photoactivity. A 23-fold increased hydrogen evolution rate of 3579 μmol h−1 g−1 (λ > 420 nm) was achieved with an apparent quantum efficiency (AQE) of 27.8% at 420 ± 15 nm, a level of performance far beyond any AQE previously reported for ultrathin/porous/doped g-C3N4 photocatalyst. Our work conclusively demonstrates a new synthetic strategy towards high performance g-C3N4-based photocatalytic materials for energy applications.An unprecedented precursor phase-transformation and recrystallization protocol was reported for the first time to yield mesoporous g-C3N4 with an outstanding photoactivity. A 23-fold increased hydrogen evolution rate of 3579 μmol h−1 g−1 (λ > 420 nm) was achieved with an apparent quantum efficiency (AQE) of 27.8% at 420 ± 15 nm.Download high-res image (228KB)Download full-size image

•Horn-like hollow mesoporous ultrathin g-C3N4 tube was first developed.•It shows an efficient spatial anisotropic charge separation between tube shells.•Greatly boosted carrier density and surface charge transfer efficiency are achieved.•A superior photocatalytic H2 evolution rate of 1353.6 μmol h−1 g−1 was obtained.•The apparent quantum efficiency is as high as 14.3% at 420 nm.Metal-free graphitic carbon nitride (g-C3N4) has triggered huge interests for converting solar energy into fuels. However, direct-calcination derived bulk g-C3N4 always suffers from low surface area and high recombination of charge carriers, prompting attempts to foster g-C3N4 nano/microstructures to achieve high performance. Conventional routes, like templating method, always yields g-C3N4 with tedious morphology and requires post-treatment. Here we release the first report on development of horn-like hollow mesoporous ultrathin (HHMU) g-C3N4 tubes via first forming a horn-like Br-containing intermediate followed by further decomposition transformation under co-pyrolysis of melamine and substantial NH4Br. The multiple-superiorities achieved here (hollow/mesoporous/ultrathin/horn-like) allows g-C3N4 high surface area, drastically boosted bulk charge separation, carrier density and surface charge transfer efficiency. This advanced g-C3N4 thus casts outstanding photocatalytic performance for H2 evolution with an apparent quantum efficiency (AQE) of 14.3% at 420 ± 15 nm, far exceeding most of reported g-C3N4. HHMU g-C3N4 also delivers a strengthened photocatalytic CO2 reduction activity into CO and CH4. Selective photo-deposition results provide an in-depth insight into charge movement behavior and high photo-reactivity that the photo-generated electrons migrate to the outer shell and holes prefer to transfer onto the inner shell of HHMU g-C3N4 tubes, thus achieving efficient spatial anisotropic charge separation. The current study may furnish a reference towards developing efficient tactics for integrally advancing g-C3N4 for renewable energy generation, and disclose a new perspective into promoting charge separation via microstructure design.Horn-like hollow mesoporous ultrathin g-C3N4 tubes are developed via an intermediate-mediated strategy, which are allowed high surface area and efficient spatial anisotropic charge separation between outer and inner shells of g-C3N4 tubes, thus demonstrating outstanding photocatalytic H2 evolution with an AQE of 14.3% at 420 ± 15 nm and efficient CO2 reduction activity.Download high-res image (301KB)Download full-size image

A novel fluoro-apatite-type compound, Ba3TbK(PO4)3F was developed via a high-temperature solid-state reaction route for the first time. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and high-resolution TEM (HRTEM) were used to investigate the component element and microstructure of the phosphor was systematically investigated. The luminescence properties of Ba3TbK(PO4)3F:Sm3+ were investigated systemically. The results revealed that the Ba3TbK(PO4)3F:Sm3+ phosphor could be efficiently excited in a broad wavelength region ranging from 200 to 400 nm, which matched perfectly with the ultraviolet (UV) light-emitting diode (LED) chips. Based on the energy transfer (ET) between Tb3+ and Sm3+, the color hue of Ba3Tb1–nK(PO4)3F:nSm3+ (n=0–0.03) was modulated from green (0.305, 0.591) to yellow (0.486, 0.437) area by controlling the Sm3+ doping concentration. The critical distance between Tb3+ and Sm3+ ions in Ba3TbK(PO4)3F:Sm3+ was calculated and the corresponding energy quenching mechanism was identified. Fascinatingly, both the Ba3TbK(PO4)3F and Ba3Tb0.995K(PO4)3F: 0.005Sm3+ phosphors exhibited very high thermal stability from room temperature (25 °C) to 300 °C, which is extremely important for practical application. In addition, the activation energy for thermal quenching of the Ba3Tb0.995K(PO4)3F:0.005Sm3+ sample was estimated to be as high as 0.312 eV. These findings demonstrated that as-prepared phosphor may serve as a high-performance candidate for the application in w-LEDs.PLE (left side) and PL (right side) of Ba3TbK(PO4)3F(a) and Ba3TbK(PO4)3F:0.005Sm3+(b) phosphorsDownload high-res image (151KB)Download full-size image

A central issue in understanding photo-redox catalysis is the facet-dependent charge movement behaviors that include bulk charge separation, surface charge transfer and interfacial charge migration. To get in-depth insight into these complicated processes steered by different exposing facets, herein BiOCl with exposed (0 0 1) and (0 1 0) facets engaged as the model are investigated. The BiOCl-(0 1 0) and BiOCl-(0 0 1) single-crystalline sheets are separately synthesized via hydrothermal and hydrolysis routes. In contrast to BiOCl-(0 1 0), BiOCl-(0 0 1) demonstrates highly promoted photo-redox performance for H2 generation and degradation of pollutants. The facet-dependent charge movement behaviors were surveyed by surface photovoltage spectroscopy (SPV), transient photocurrent, linear sweep voltammetry, continuous wavelength photocurrent, and electrochemical impedance spectrum (EIS). All the photoelectrochemical and photoelectric measurement results reflect that BiOCl-(0 0 1) exhibits superior charge separation and migration efficiencies in the whole charge movement process than the BiOCl-(0 1 0). Besides, a higher charge carrier density (3.1-fold enhancement) was also observed for BiOCl-(0 0 1) compared to BiOCl-(0 1 0). Our current work is expected to further our understanding on facet-dependent charge movement behaviors and offer new insight into design of high-performance photocatalytic/photoelectrochemical materials.Download high-res image (133KB)Download full-size image

A conducting polymer polypyrrole (Ppy) was first employed to decorate BiOI for fabricating an organic-inorganic hybridized Ppy-BiOI nanocomposite photocatalyst via a facile in situ precipitation strategy at room temperature. The composite and intimate interface was confirmed by FTIR, XPS, SEM, HRTEM and TEM-mapping. In comparison with pristine BiOI, the Ppy-BiOI hybrids present significantly enhanced photocatalytic activity for degradation of Rhodamine B (RhB) under visible light (λ > 420 nm). Particularly, the Ppy-BiOI composite exhibits an universal photocatalytic performance for removing diverse industrial pollutants and antibiotics, including bisphenol A, 2,4-dichlorophenol, tetracycline hydrochloride and chlortetracycline hydrochloride. The enhanced photocatalytic activity of Ppy-BiOI composite is found attributable to the bifunctional role that Ppy takes. Ppy-BiOI composite has an enhanced specific surface area, which benefits adsorption and generation of more active sites. Notably, high separation and transfer of the photogenerated charge carriers was achieved on the interface between Ppy and BiOI, and the photogenerated hole transfer action of Ppy is demonstrated. Therefore, synergistic effect of adsorption-enrichment and photocatalytic degradation is realized. Our work may offer a guideline to manipulate high-performance Bi-based composite photocatalyst by coupling conducting polymers.Download high-res image (146KB)Download full-size image

•Iodine doped BiOIO3 was synthesized by a facile hydrothermal process.•Photo-responsive range of BiOIO3 is extended from UV to visible light.•Iodine doped BiOIO3 shows much higher photocatalytic activity than BiOIO3.•Superoxide radicals and hydroxyl radicals are generated under visible light.Visible-light active photocatalytic performance of a layered bismuth-based photocatalyst BiOIO3 was achieved by iodine ion doping through a facile hydrothermal process. Compared to pure BiOIO3, the light responsive range of BiOIO3 is drastically extended from UV to visible light, and the adjustable band gap is also achieved. The photocatalytic experiments revealed that I-doped BiOIO3 displays significantly enhanced photocatalytic activity (over 6-fold increase) toward degradation of two types of azo dyes methyl orange (MO) and Rhodamine B (RhB) with visible light illumination (λ > 420 nm). The photoelectrochemical measurement also confirms the greatly promoted photo-activity of modified BiOIO3. The band structure evolution and visible-light induced photocatalytic mechanism are investigated in detail. It is demonstrated that the visible-light response of I-doped BiOIO3 mainly originates from a larger down-shift of the conduction band than valence band. Additionally, two powerful radicals superoxide radicals (O2−) and hydroxyl radicals (OH) are produced in the photodegradation process, which are responsible for the high visible-light photocatalytic activity.I-doped BiOIO3 displays significantly enhanced photocatalytic activity (over 6-fold increase) toward degradation of methyl orange (MO) and Rhodamine B (RhB) with visible light illumination (λ > 420 nm).Download high-res image (201KB)Download full-size image

Heterostructure photocatalyst fabrication is of great significance for promoting the photoreactivity and solar-energy utilization efficiencies. In this work, AgI/BiOIO3 heterostructure photocatalysts are synthesized by a facile in-situ crystallization of AgI on BiOIO3. The photocatalytic performance is first surveyed by decomposition of model dye methyl orange (MO) separately with illumination of UV light and visible-light (λ > 420 nm). It indicates that AgI/BiOIO3 shows highly improved photocatalytic activity regardless of the light source, which should be attributed to the matchable band energy levels between AgI and BiOIO3, benefiting the efficient charge separation. Notably, AgI/BiOIO3 shows a universal photocatalytic activity for treating diverse antibiotics and phenols, including tetracycline hydrochloride, chlortetracycline hydrochloride, 2,4-dichlorophenol (2,4-DCP), phenol and bisphenol A (BPA), and the strong mineralization ability of AgI/BiOIO3 was also demonstrated. Additionally, the different mechanisms under UV and visible light irradiation are investigated in detail. This work provides a new reference for design and manipulation of high-performance nonselective heterostructure photocatalyst for environmental purification.Download high-res image (232KB)Download full-size imageAgI/BiOIO3 heterostructure shows enhanced UV and visible-lightphotocatalytic activity enhancement, and can decompose many antibiotics and industrial contaminants with high mineralizationability.

•BiOCl/Bi12O17Cl2 phasesjunctions are obtained by an one-pot hydrothermal process.•BiOCl/Bi12O17Cl2 shows higher degradation activity than BiOCl and Bi12O17Cl2.•It shows an universal photocatalytic activity for diverse contaminants degradation.•Enhanced charge separation is responsible for the enhanced degradation activity.Fabrication of homo/hetero-junctions by coupling of wide-band gap semiconductor and narrow-band gap semiconductor is desirable as they can achieve a decent balance between photoabsorption and photo-redox ability. Herein, a n-n type bismuth oxychloride homogeneous phasejunction BiOCl/Bi12O17Cl2 was developed by facilely manipulating the basicity in a one-pot hydrothermal process. Compared with BiOCl which only responds to UV light, the photo-responsive range is remarkably extended to visible region. The BiOCl/Bi12O17Cl2 phasejunctions show much higher photocatalytic activity than the single BiOCl and Bi12O17Cl2 toward degradation of methyl orange (MO) under simulated solar light. In particular, it presented a high photo-oxidation ability in degrading diverse industrial contaminants including 2,4-dichlorophenol (2,4-DCP), phenol, bisphenol A (BPA) and tetracycline hydrochloride. Based on a series of photoelectrochemical and photoluminescence measurements, the fortified photocatalytic performance of BiOCl/Bi12O17Cl2 phasejunctions was manifested to be attributed to the efficient separation and transfer efficiencies of photoinduced electron-hole pairs because of the junctional interface formed between BiOCl and Bi12O17Cl2. The study may not only furnish a high-effective photocatalyst in the application of environment purification, but also pave a path to fabricate agnate phase-junctional photocatalyst.BiOCl/Bi12O17Cl2 phasejunctions show much higher photodegradation activity than the single BiOCl and Bi12O17Cl2 and universal photocatalytic activity for treating diverse c ontaminants.Download high-res image (129KB)Download full-size image

Metal-free graphitic carbon nitride (g-C3N4) has sparked considerable interest due to its efficient photocatalytic activity in many fields. Development of new tactics toward improving the photocatalytic performance of g-C3N4 remains active and challenging. In this study, we uncover an unprecedented template-free precursor (melamine) pre-treatment protocol to achieve porous g-C3N4 nanosheets for efficient photocatalytic reduction and oxidation reaction. The introduction of thiourea solution in the hydrothermal pre-treatment process etches the surface of melamine, thus yielding the porous, thin g-C3N4 nanosheets. The microstructure and porosity of g-C3N4 can be adjusted only by controlling the thiourea amount. The as-obtained porous g-C3N4 nanosheets are found to be endowed with not only increased specific surface area, but also enhanced photoabsorption in the visible light region. Systematic characterizations of the charge movement behavior (transient photocurrent, linear sweep voltammetry, electrochemical impedance spectra, photoluminescence and surface photovoltage spectroscopy) disclose that the separation of photogenerated charge carriers is remarkably boosted by fabricating such a porous nanosheet structure. Benefiting from these advantages, porous g-C3N4 nanosheets present profoundly enhanced visible-light photocatalytic performance for H2 evolution (3.3-fold increase) and NO removal from the gaseous phase (5.5 times increase) in contrast to the pristine bulk g-C3N4. Our current study may offer an alternative approach to designing high-performance g-C3N4 nanomaterials for energy and environmental applications.

•A series of 3D hierarchical bismuth oxyiodides were fabricated.•These bismuth oxyiodides include BiOI, Bi4O5I2, Bi4O5I2-Bi5O7I junction and Bi5O7I.•They exhibit different microstructures and photoactivity against diverse pollutants.•Charge separation efficiency is mainly responsible for their photocatalytic activity.Design of three-dimensional (3D) hierarchical architectures and nano-phase-junctions are of huge significance for semiconductor photocatalysis. Herein, we report the fabrication of a series of 3D hierarchical bismuth oxyiodides via in situ phase transformation and phase-junction construction utilizing BiOI microspheres as self-sacrificed template through a facile calcination strategy. The multiform bismuth oxyiodides obtained at different temperatures include hierarchical BiOI, Bi4O5I2, Bi4O5I2-Bi5O7I phase-junction and Bi5O7I. These bismuth oxyiodides exhibit very distinct microstructure and band structure, and their photoabsorption was orderly tuned from 700 to 400 nm, rendering the adjustable oxidation and reduction ability of band energy levels. The photocatalytic activity of the bismuth oxyiodide series is systematically assessed by degradation of diverse antibiotic and contaminants, such as tetracycline hydrochloride, bisphenol A (BPA) and azo dye Rhodamine B (RhB). It disclosed that they present discrepant photocatalytic performance with activity order of Bi4O5I2-Bi5O7I > Bi4O5I2 > Bi5O7I > BiOI, which is closely associated with the charge separation efficiency, band structure and surface area. Additionally, the photocatalytic mechanism and degradation pathway are also surveyed. The study may furnish new insights into development of novel 3D hierarchical architectures and nano-phase-junctions for heterogeneous photocatalysis.Download high-res image (219KB)Download full-size image

We herein describe the coupling of solid-solution and heterojunction in a 2D-1D BiOCl0.5I0.5/Bi5O7I hierarchical architecture for optimizing photoabsorption, energy band levels and charge separation, thereby promoting the photo-oxidation and molecular oxygen activation performance. BiOCl0.5I0.5/Bi5O7I shows a core-shell-like structure with BiOCl0.5I0.5 thin nanoflakes (∼3 to 8 layers) homogeneously vertical coating on the surface of Bi5O7I strips. The photo-responsive range of BiOCl0.5I0.5/Bi5O7I can be orderly tuned from 450 nm to 650 nm by increasing the BiOCl0.5I0.5 content. Regardless of visible light (λ > 420 nm) or UV light (365 nm) irradiation, BiOCl0.5I0.5/Bi5O7I casts highly promoted photocatalytic activity in decomposing methyl orange (MO) compared to the BiOCl0.5I0.5 and Bi5O7I. This enhancement on full-spectrum photoreactivity is attributable to the facilitated charge separation derived from BiOCl0.5I0.5/Bi5O7I heterojunction with intimate interfacial interaction, which is approved by transient photocurrent response under visible and UV–vis light. To probe the photocatalytic mechanism, active species trapping tests are performed over BiOCl0.5I0.5, Bi5O7I and BiOCl0.5I0.5/Bi5O7I, which reveal superoxide radical (O2-) and hole (h+) take dominant roles in photo-oxidation reaction. BiOCl0.5I0.5/Bi5O7I was also found possessing a stronger ability in molecular oxygen activation with a O2- production rate of 2.22 × 10−7 mol L−1 h−1, which far outperforms Bi5O7I (1.35 × 10−7 mol L−1 h−1) and BiOCl0.5I0.5 (1.54 × 10−7 mol L−1 h−1). It further corroborates the efficient band charge transfer between BiOCl0.5I0.5 and Bi5O7I. This work may furnish a new concept on smart design of high-performance photocatalytic materials via manipulating multiple strategies.Download high-res image (199KB)Download full-size image

We herein report a facile and general approach to modulating the band energy level of semiconductors for visible-light photocatalysis via iodide surface decoration. This strategy enables the wide-band-gap Bi2O2CO3 to possess a continuously tunable band gap and profoundly boosted visible-light photocatalytic performance for dye degradation and NO removal.

Three series of ternary hierarchical architecture photocatalysts Ag/AgX (X = Cl, Br, I)/AgIO3 were fabricated for the first time by a facile in situ ion-exchange route. The novel ternary architectures are confirmed by XRD, XPS, SEM, TEM, EDX, and EDX mapping. In contrast to pristine AgIO3, the Ag/AgX (X = Cl, Br, I)/AgIO3 composites show extended absorption edges and highly boosted photoabsorption in the visible region, which are separately ascribed to the intrinsic absorption of AgX and the surface plasmon resonance (SPR) effect of Ag species. The photocatalysis activity of Ag/AgX (X = Cl, Br, I)/AgIO3 composites is studied and compared via photodegradation of methyl orange (MO) under visible-light (λ > 420 nm) irradiation. It is interesting to find that the activity enhancement levels are different for Ag/AgX (X = Cl, Br, I)/AgIO3 with four types of photocatalytic mechanism, which are closely related to the type of AgX or the component content in Ag/AgX (X = Cl, Br, I)/AgIO3. The separation behaviors of charge carrier were also systematically investigated by the PL and EIS. The study may furnish new perspective into controllable fabrication of hierarchical architecture photocatalysts with multiform photocatalytic mechanism.Keywords: Ag; AgIO3; AgX (X = Cl; Br; I); Photocatalyst; Visible-light

The homogeneous BiOBr/Bi heterojunctions photocatalyst was synthesized from {001} facet dominated BiOBr flakes via a PVP-assisted in situ reduction reaction at room temperature. The high {001} facet exposure of BiOBr could induce the homogeneous distribution of metallic Bi on the surface of BiOBr. The introduction of PVP not only effectively protected the uniform structure but also largely promoted the photocatalysis properties. Compared to the bare BiOBr, an obviously enhanced photochemical performance was achieved over the homogeneous BiOBr/Bi pertaining to methyl orange (MO) degradation and photocurrent generation. The highly enhanced photocatalytic activity can be attributed not only to the surface plasmon resonance effect and efficient separation of electron–hole pairs by the metallic Bi but also to its uniform and regular structure. The present work provided a new approach to the development of attractive bismuth-based-photocatalysts/metallic Bi heterostructures with controllable structures and photocatalytic performance.Keywords: BiOBr; In situ reduction; Metallic Bi; Photocatalyst; Plasmon resonance effect; PVP-assisted;

The development of high-performance visible-light photocatalysts with a tunable band gap has great significance for enabling wide-band-gap (WBG) semiconductors visible-light sensitive activity and precisely tailoring their optical properties and photocatalytic performance. In this work we demonstrate the continuously adjustable band gap and visible-light photocatalysis activation of WBG BiOIO3via iodine surface modification. The iodine modified BiOIO3 was developed through a facile in situ reduction route by applying BiOIO3 as the self-sacrifice template and glucose as the reducing agent. By manipulating the glucose concentration, the band gap of the as-prepared modified BiOIO3 could be orderly narrowed by generation of the impurity or defect energy level close to the conduction band, thus endowing it with a visible light activity. The photocatalytic assessments uncovered that, in contrast to pristine BiOIO3, the modified BiOIO3 presents significantly boosted photocatalytic properties for the degradation of both liquid and gaseous contaminants, including Rhodamine B (RhB), methyl orange (MO), and ppb-level NO under visible light. Additionally, the band structure evolution as well as photocatalysis mechanism triggered by the iodine surface modification is investigated in detail. This study not only provides a novel iodine surface-modified BiOIO3 for environmental application, but also provides a facile and general way to develop highly efficient visible-light photocatalysts.

We for the first time disclose the integrated effects of a semiconductor p–n heterojunction and dominantly exposed reactive facets that are enabled in a facile way. Unlike most of the reported semiconductor heterojunctions that are constructed by compositing the individual components, in this work, we report the composition–transformation fabricating BiOI/BiOIO3 heterostructure via an in situ reduction route by using thiourea as the reducing agent. This reducing process enables BiOIO3 dominant exposure of the {010} reactive facet, and the exposed percentage can be effectively tuned by monocontrolling the thiourea concentration. The photocatalysis and photoelectrochemical properties of samples are assessed by surveying the decomposition of methyl blue (MB) and photocurrent generation under simulated solar light or visible light illumination. The heterostructured BiOI/BiOIO3 nanocomposites unfold drastically strengthened photoreactivity, in which the MB degradation rate is over 85% for 1 h irradiation, and the photocurrent density rises more than 3 times higher than the pristine sample. This enhancement should be ascribed to the formation of a steady p–n junction between the n-type BiOIO3 and p-type BiOI as well as dominantly exposed reactive facets. Separation and transfer of photoinduced charges are thereby greatly boosted as verified by the electrochemical and photoelectrochemical results. This work paves a novel way for fabrication of semiconductor p–n junction via composition transformation and furnishes a new perspective into the designing of crystal reactive facet.

We disclose the fabrication of 2D–2D heterojunctional nanosheets g-C3N4/Bi4O5I2 photocatalyst by using a mixed-calcination method. This synthetic method enables intimate interfacial interaction between g-C3N4 and Bi4O5I2, which is beneficial for charge transfer at the interface. The photocatalysis properties of g-C3N4/Bi4O5I2 composites were studied by photodegradation of Rhodamine B (RhB) and NO removal under visible-light (λ > 420 nm) irradiation. The results revealed that the g-C3N4/Bi4O5I2 composites show enhanced photocatalytic activity compared to the pristine g-C3N4 and Bi4O5I2 samples. Investigations on the behaviours of charge carriers via photoluminescence (PL) spectra and transient photocurrent responses suggest that the g-C3N4/Bi4O5I2 heterostructure is responsible for the efficient separation and transfer of photogenerated electron–hole pairs, thus giving rise to the higher photocatalytic activity. The formation of 2D–2D heterostructured n–n type g-C3N4/Bi4O5I2 composites as well as photocatalytic mechanism was verified by a series of combined techniques, including the active species trapping experiments and Mott–Schottky plots. The present work furthered our understanding on fabrication of homogeneous heterojunction photocatalyst.

⿢Bi2MoO6/g-C3N4 composites were synthesized by a mixed-calcination method.⿢The Bi2MoO6/g-C3N4 photocatalyst exhibits much better photocatalytic performance.⿢The enhanced photocatalytic activity is attributed to the hetrojunction structure.⿢Holes (h+) and superoxide radicals (O2⿿) serve as the two main active species.Organic-inorganic hybrid photocatalyst Bi2MoO6/g-C3N4 was synthesized via a mixed-calcination route based on intimate interfacial interaction. The successful combination of g-C3N4 and Bi2MoO6 was verified by X-ray diffraction (XRD), Fourier-transform infrared spectra (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) mapping. The optical property of the as-prepared photocatalysts was characterized by UV⿿vis diffuse reflectance spectra (DRS). The photocatalytic activities were investigated by degradation of Rhodamine B (RhB) and photocurrent generation under visible-light (λ > 420 nm). The results demonstrated that the Bi2MoO6/g-C3N4 composite exhibits highly enhanced photoreactivity compared to the pristine samples. It should be attributed to the fabrication of a Bi2MoO6/g-C3N4 heterojunction, thus resulting in the high separation and transfer efficiency of photogenerated charge carriers, as confirmed by the photoluminescence (PL) and electrochemical impedance spectra (EIS). The active species trapping experiments indicated that holes (h+) and superoxide radicals (O2⿿) are the main active species in the degradation process.

•A layered Bi-based compound LiBi3O4Cl2 is researched as new photocatalysts.•It is synthesized by a simple solid-state reaction.•It can effectively degrade azo dye and phenol under light irradiation.•OH and h+ as active species play important roles in degradation process.Developing new photocatalysts is of significant importance for their potential environmental and energetic applications. Herein, a novel layered bismuth-based photocatalytic material LiBi3O4Cl2 was developed by a simple solid-state reaction. The morphology, microstructures and optical properties were investigated by XRD, SEM, TEM and DRS. The band gap of LiBi3O4Cl2 has been determined to be 3.35 eV, and its ECB and EVB were also estimated. The photocatalytic property of LiBi3O4Cl2 is surveyed by oxidative decomposition of rhodamine B (RhB), methyl orange (MO), methylene blue (MB) and phenol in aqueous solution. The results demonstrated that LiBi3O4Cl2 is an efficient UV light active photocatalyst, which can destroy the contaminants with irradiation. It is also more effective in degrading pollutants than the related layered bismuth-based photocatalyst Bi4NbO8Br. The photocatalysis mechanism is detailedly investigated by active species trapping measurement and terephthalic acid photoluminescence probing technique (TA-PL). It revealed that powerful hydroxyl radicals (OH) and photogenerated holes (h+) are the two main active species and are responsible for the efficient degradation process. This study provides a new layered bismuth-based photocatalytic material for environmental and energetic applications.A novel layered photocatalyst LiBi3O4Cl2 has been developed for efficient photodecomposition of contaminants. The photocatalytic mechanism was also investigated.

Two novel visible-light-responsive bismuth oxychloride photocatalysts Bi2EuO4Cl and Bi2NdO4Cl have been successfully developed via a solid-state reaction route. Their crystal structures and optical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), diffuse reflectance spectra (DRS), and photoluminescence (PL) spectra. Fascinatingly, both the compounds possess considerable optical absorption in a broad region ranging from UV light to visible light. The indirect-transition optical band gaps of Bi2EuO4Cl and Bi2NdO4Cl are estimated to be 2.21 and 1.89 eV, respectively. For the first time, their photocatalytic activities were determined by photodecomposition of methylene blue (MB) in aqueous solution under visible light (λ>420 nm). The results revealed that both Bi2EuO4Cl and Bi2NdO4Cl can be used as effective visible-light-driven photocatalysts. In addition, theoretical calculations on the electronic structure, orbital constitutions and optical absorption of Bi2NdO4Cl were also performed. These findings shed light on the exploration of new photocatalytic materials activated by visible light.

•(CO3)2− self-doped Bi2O2CO3/g-C3N4 composites are synthesized.•Due to charge attraction, 2D-2D Bi2O2CO3/g-C3N4 heterostructure is formed.•The composites show highly enhanced photocatalytic activity for RhB degradation.•High charge transfer efficiency is responsible for the photoactivity enhancement.The (CO3)2− self-doped Bi2O2CO3/g-C3N4 (C-BOC/g-C3N4) unique 2D-2D heterostructure has been developed via a mixed-calcination method. This heterostructure is confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), SEM-mapping, and diffuse reflection spectroscopy (DRS). Due to the charge interaction, it is interesting to observe that C-BOC nanosheets are assembled on g-C3N4 in a surface–surface coupling way, which enables an intimate interfacial interaction between the two components. The photocatalytic activity is evaluated by photodegradation of Rhodamine B (RhB) under visible light (λ > 420 nm). It is found that all the C-BOC/g-C3N4 composites showed highly enhanced photocatalytic activity. Electrochemical impedance spectra (EIS) measurement revealed that the largely promoted charge transfer derived from the well matchable band structure and intimate interfacial interactions between the two visible-light active components is responsible for the photoactivity enhancement. Besides, the active species trapping and O2− quantitation experiments are conducted to disclose the photocatalytic mechanism.(CO3)2− self-doped Bi2O2CO3/g-C3N4 2D-2D heterostructure is synthesized and its shows highly enhanced visible-light photocatalytic activity.

Metal-free graphitic carbon nitride (g-C3N4) shows benign photocatalytic abilities concerning contaminant decomposition and hydrogen evolution under visible light irradiation. Developing facile modification tactics for promoted activity of g-C3N4 has always been desirable and worth pursuing. Herein, we report the integration of multiple (three-in-one) advantageous effects in g-C3N4 photocatalyst by a simple co-pyrolyzation of co-precursors melamine and NH4HCO3. This strategy utilizing NH4HCO3 as a bubble soft template not only endows g-C3N4 with porous structure with enhanced specific surface area, but also renders highly promoted separation and transfer of charge carriers and up-shifted conduction band. Given these benefits, the modified g-C3N4 unfolds remarkably improved photocatalytic performance toward RhB degradation, NO removal, and hydrogen evolution. Additionally, the exploration on active radicals has also corroborated the ameliorated band structure and illustrates the photocatalytic mechanism. Our present work may open up a new avenue for ameliorating the photocatalytic property of g-C3N4 and also further our understanding of design of high-performance photoelectric materials.

We herein demonstrate self-doping of the CO32– anionic group into a wide bandgap semiconductor Bi2O2CO3 realized by a one-pot hydrothermal technique. The photoresponsive range of the self-doped Bi2O2CO3 can be extended from UV to visible light and the band gap can be continuously tuned. Density functional theory (DFT) calculation results demonstrate that the foreign CO32– ions are doped in the caves constructed by the four adjacent CO32– ions and the CO32– self-doping can effectively narrow the band gap of Bi2O2CO3 by lowering the conduction band position and meanwhile generating impurity level. The photocatalytic performance is evaluated by monitoring NO removal from the gas phase, photodegradation of a colorless contaminant (bisphenol A, BPA) in an aqueous solution, and photocurrent generation. In comparison with the pristine Bi2O2CO3 which is not sensitive to visible light, the self-doped Bi2O2CO3 exhibits drastically enhanced visible-light photoreactivity, which is also superior to that of many other well-known photocatalysts such as P25, C3N4, and BiOBr. The highly enhanced photocatalytic performance is attributed to combination of both efficient visible light absorption and separation of photogenerated electron–hole pairs. The self-doped Bi2O2CO3 also shows decent photochemical stability, which is of especial importance for its practical applications. This work demonstrates that self-doping with an anionic group enables the band gap engineering and the design of high-performance photocatalysts sensitive to visible light.Keywords: band gap; Bi2O2CO3; charge separation; photocatalysis; self-doping

We demonstrate the fabrication of a core–satellite structured BiOBr–CdS photocatalyst with highly efficient photocatalytic reactivity via a facile in situ crystallization approach at room temperature. The transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HR-TEM) results reveal that the BiOBr flakes are surrounded by CdS particles. The coverage of the satellites on the surface of the BiOBr nanosheets could be controlled by changing the content of the CdS, which contributes to the enhanced level of photocatalytic performance. The UV–vis diffuse reflection spectra demonstrate that the visible light absorption of the BiOBr–CdS photocatalyst is also enhanced by the CdS loaded. The excellent structural and spectral properties endow the BiOBr–CdS heterojunctions with improved photocatalytic performance pertaining to bisphenol A (BPA) degradation and photocurrent generation. Under visible light irradiation, the optimum photocatalytic activity of BiOBr–CdS at a molar ratio of 1:5 (CdS/BiOBr) is almost 2.8 times and 24.6 times as high as that of pure BiOBr and CdS. The remarkably enhanced photoreactivity should be attributed to the match in the energy levels and close core–satellite structural coupling between the CdS and BiOBr, which greatly facilitates the separation and transfer of photoinduced electron–hole pairs, as confirmed by photoluminescence (PL) and electrochemical impedance spectra (EIS). The present work sheds new light on the construction of highly efficient core–satellite heterojunctional photocatalysts for practical applications.

Development of efficient photocatalysts with both photoinduced oxidation and reduction properties is of great importance for environmental and energy applications. Herein, we report the fabrication of CeO2/g-C3N4 hybrid materials by a simple in situ co-pyrolysis method using Ce(IO3)3 and melamine as precursors. The CeO2/g-C3N4 composite catalysts possess outstanding photocatalytic activity for phenol degradation and NO removal under visible light irradiation. The degradation efficiency reaches up to 68.5 and 17.3 times higher than that of pure CeO2 and g-C3N4, respectively. Significantly, it simultaneously exhibits an enhanced hydrogen production rate, which is 1.5 times that of the pure g-C3N4. The highly enhanced photo-induced oxidation and reduction activity could be attributed to the construction of a CeO2/g-C3N4 n–n type heterojunction established by our in situ co-pyrolysis route, which enables intimate interaction across the phase interfaces; this facilitates separation and transfer of photoexcited charge carriers. This study could not only provide a facile and general approach to the fabrication of high-performance carbon-nitride-based photocatalytic materials, but also increase our understanding further on designing new hybrid composite photocatalysts for multi-functional applications.

Developing high-performance photocatalytic materials is of huge significance and highly desirable for fulfilling the pressing need in environmental remediation. In this work, we demonstrate the use of bismuth nitrate Bi2O2(OH)(NO3) as an absorbing photocatalyst, which integrates multiple superiorities, like a [Bi2O2]2+ layered configuration, a non-centrosymmetric (NCS) polar structure and highly reactive {001} facets. Bi2O2(OH)(NO3) nanosheets are obtained by a facile one-pot hydrothermal route using Bi(NO3)3·5H2O as the sole raw material. Photocatalysis assessment revealed that Bi2O2(OH)(NO3) holds an unprecedented photooxidation ability in contaminant decomposition, far out-performing the well-known photocatalysts BiPO4, Bi2O2CO3, BiOCl and P25 (commercial TiO2). Particularly, it displays a universally powerful catalytic activity against various stubborn industrial contaminants and pharmaceuticals, including phenol, bisphenol A, 2,4-dichlorophenol and tetracycline hydrochloride. In-depth experimental and density functional theory (DFT) investigations co-uncovered that the manifold advantages, such as large polarizability and rational band structure, as well as exposed {001} active facets, induced robust generation of strong oxidating superoxide radicals (˙O2−) in the conduction band and hydroxyl radicals (˙OH) in the valence band, thus enabling Bi2O2(OH)(NO3) to have a powerful and durable photooxidation capability. Bi2O2(OH)(NO3) also presents high photochemical stability. This work not only rendered a highly active and stable photocatalyst for practical applications, but also laid a solid foundation for future initiatives aimed at designing new photoelectronic materials by manipulating multiple advantageous factors.

A high-performance visible-light-active photocatalyst is prepared using the polyelectrolyte/exfoliated titania nanosheet/graphene oxide (GO) precursor by flocculation followed by calcination. The polyelectrolyte poly(diallyl-dimethyl-ammonium chloride) serves not only as an effective binder to precipitate GO and titania nanosheets, but also boosts the overall performance of the catalyst significantly. Unlike most titania nanosheet-based catalysts reported in the literature, the composite absorbs light in the UV-Vis-NIR range. Its decomposition rate of methylene blue is 98% under visible light. This novel strategy of using a polymer to enhance the catalytic performance of titania nanosheet-based catalysts affords immense potential in designing and fabricating next-generation photocatalysts with high efficiency.

Herein, we uncover simultaneously achieving plasmonic Bi metal deposition and I– doping by employing wide-band-gap BiOIO3 as the self-sacrificing template. It was synthesized via a facile NaBH4-assisted in situ reduction route under ambient conditions. The reducing extent as well as photocatalytic levels can be easily modulated by controlling the concentration of NaBH4 solution. It is interesting that the band gap of BiOIO3 can be continuously narrowed by the modification, and the photoresponse range is drastically extended to cover the whole visible region. Bi/I– codecorated BiOIO3 not only exhibits profoundly upgraded photoreactivity in comparison with pristine BiOIO3 but also shows universally strong photooxidation properties toward decomposition of multiple industrial contaminants and pharmaceutical, including phenol, 2,4-Dichlorophenol (2,4-DCP), bisphenol A (BPA), dye model Rhodamine (RhB), tetracycline hydrochloride, and gaseous NO under visible light (λ ≥ 420 nm) or simulated solar light irradiation. It also outperforms the well-known and important photocatalysts C3N4, BiOBr, and Bi2WO6 for NO removal. The cooperative effects from Bi SPR and I– doping endow BiOIO3 with a narrowed band gap and highly boosted separation of charge carriers, thus responsible for the outstanding catalytic activity. The present study provides an absorbing candidate for practical environmental applications and also furthers our understanding of developing high-performance photocatalysts by manipulating manifold strategies in a facile way.Keywords: Bi deposition; I doping; in situ reduction; photoabsorption; photocatalysis

The fabrication of multiple heterojunctions with tunable photocatalytic reactivity in full-range BiOBr–BiOI composites based on microstructure modulation and band structures is demonstrated. The multiple heterojunctions are constructed by precipitation at room temperature and characterized systematically. Photocatalytic experiments indicate that there are two types of heterostructures with distinct photocatalytic mechanisms, both of which can greatly enhance the visible-light photocatalytic performance for the decomposition of organic pollutants and generation of photocurrent. The large separation and inhibited recombination of electron–hole pairs rendered by the heterostructures are confirmed by electrochemical impedance spectra (EIS) and photoluminescence (PL). Reactive species trapping, nitroblue tetrazolium (NBT, detection agent of •O2–) transformation, and terephthalic acid photoluminescence (TA-PL) experiments verify the charge-transfer mechanism derived from the two types of heterostructures, as well as different enhancements of the photocatalytic activity. This article provides insights into heterostructure photocatalysis and describes a novel way to design and fabricate high-performance semiconductor composites.Keywords: BiOBr; BiOI; crystal structure; electronic structure; photocatalytic mechanism

Development of core/shell heterostructures and semiconductor p–n junctions is of great concern for environmental and energy applications. Herein, we develop a facile in situ deposition route for fabrication of a BiVO4/BiOI composite integrating both the core/shell heterostructure and semiconductor p–n junction at room temperature. In the BiVO4/BiOI core/shell heterostructure, the BiOI nanosheets are evenly assembled on the surface of the BiVO4 cores. The photocatalytic performance is evaluated by monitoring the degradation of the dye model Rhodamine B (RhB), colorless contaminant phenol, and photocurrent generation under visible-light irradiation. The heterostructured BiVO4/BiOI core/shell photocatalyst shows drastically enhanced photocatalysis properties compared to the pristine BiVO4 and BiOI. This remarkable enhancement is attributed to the intimate interfacial interactions derived from the core/shell heterostructure and formation of the p–n junction between the p-type BiOI and n-type BiVO4. Separation and transfer of photogenerated electron–hole pairs are hence greatly facilitated, thereby resulting in the improved photocatalytic performance as confirmed by electrochemical, photoelectrochemical, radicals trapping, and superoxide radical (•O2–) quantification results. Moreover, the core/shell BiVO4/BiOI also displays high photochemical stability. This work sheds new light on the construction of high-performance photocatalysts with core/shell heterostructures and matchable band structures in a simple and efficient way.Keywords: BiOI; BiVO4; Core/shell heterostructures; Photocatalysis; p−n junction

We disclose the fabrication of a mediator-free direct Z-scheme photocatalyst system BiVO4/g-C3N4 using a mixed-calcination method based on the more reliable interfacial interaction. The facet coupling occurred between the g-C3N4 (002) and BiVO4 (121), and it was revealed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM). The crystal structure and optical properties of the as-prepared samples have also been characterized by Fourier-transform infrared (FTIR), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectra (DRS) in details. The photocatalytic experiments indicated that the BiVO4/g-C3N4 composite photocatalysts display a significantly enhanced photocatalytic activity pertaining to RhB degradation and photocurrent generation (PC) compared to the pristine BiVO4 and g-C3N4. This remarkably improved photocatalytic performance should be attributed to the fabrication of a direct Z-scheme system of BiVO4/g-C3N4, which can result in a more efficient separation of photoinduced charge carriers than band–band transfer, thus endowing it with the much more powerful oxidation and reduction capability, as confirmed by the photoluminescence (PL) spectra and electrochemical impedance spectra (EIS). The Z-scheme mechanism of BiVO4/g-C3N4 heterostructure was verified by a series of combined techniques, including the active species trapping experiments, NBT transformation and terephthalic acid photoluminescence probing technique (TA-PL) over BiVO4/g-C3N4 composites and the pristine samples. The present work not only furthered the understanding of mediator-free Z-scheme photocatalysis, but also shed new light on the design of heterostructural photocatalysts with high-performance.

Herein we report the Bi2O2CO3 single-crystal nanoplates with dominant {001} exposing facets fabricated via a controllable hydrothermal means. Exposed {001} reactive facets enable BOC-001 nanoplates efficient separation and migration of photoinduced electron–hole pairs, thereby resulting in highly enhanced photoreactivity pertaining to rhodamine B degradation, NO removal, and photocurrent generation. The present work provides a new reference for manipulation of facet-dependent photocatalytic activity of semiconductors.

We, for the first time, demonstrate band-gap-broadening as a new approach to remarkably enhance the photocatalytic activity of Br− substituted BiOI photocatalysts, which were fabricated via a facile chemical precipitation route. The successful incorporation of Br− ions into the crystal lattice of BiOI was confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The photocatalytic experiments demonstrated that all of the Br–BiOI samples exhibited highly improved photocatalytic performances pertaining to rhodamine B (RhB) and phenol degradation under visible light (λ > 420 nm). The active species trapping and electron spin resonance (ESR) experiments also suggested that more superoxide radicals (˙O2−), serving as the main active species, were generated over Br–BiOI than pristine BiOI in the photooxidation process. Based on the results from experiments and theoretical calculations, the enhancement of photocatalytic activity should be attributed to the lowered valence band (VB) potential and enlarged band gap induced by the Br− replacement, which greatly facilitated the high separation of photoinduced electron–hole pairs, as verified by the photoluminescence (PL) experiments, electrochemical impedance spectra (EIS) and Bode-phase spectra. This work sheds light on a new method to improve the photocatalytic performance of photocatalysts.

Plasmon induced Au nanoparticle and surface oxidation induced co-decorated BiOIO3 heterostructured nanocomposites have been developed via a facile in situ photosynthesis route. The structural and optical properties of the as-prepared photocatalysts were systematically characterized by XRD, XPS, TEM, SEM, UV-Vis DRS and PL. Fascinatingly, the introduction of Au nanoparticles induced not only an enhanced photoabsorption in the visible region, but also the microstructural variation of BiOIO3. The oxidative effect of HAuCl4 resulted in the formation of Bi4+/Bi5+, which led to the increased specific surface area of the products. The photocatalysis and photoelectrochemical properties of the samples were investigated by monitoring the photodecomposition of Rhodamine B (RhB) and photocurrent generation under UV-visible light illumination. The results revealed that Au@BiOIO3 presents drastically enhanced photoreactivity compared with the pristine BiOIO3. The highly improved photochemical properties are ascribed to the synergic contribution of the highly promoted generation and separation of charge carriers induced by the surface plasmon resonance (SPR) effect of Au particles, surface chemical state change, as well as the significantly high surface area that provides more reactive sites. These results are corroborated by the electrochemical impedance spectra (EIS), bode-phase spectra, PL spectra, active trapping and DMPO-assisted ESR measurements. This study not only provides evidence for the feasibility of metallic Au as a SPR co-catalyst of bismuth-based materials, but also furnishes new insights into the multiple effects for enhancing the photochemical properties.

A Ba3GdK(PO4)3F:Tb3+, Eu3+ phosphor with fluoro-apatite-structure has been fabricated by a conventional high-temperature solid-state reaction. The crystal structure, component element and microstructure of the phosphor have been systematically investigated by X-ray diffraction refinement, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM), respectively. The Ba3GdK(PO4)3F:Tb3+ phosphor shows a blue-greenish emission peak at 547 nm under excitation of 276 nm, while Ba3GdK(PO4)3F:Eu3+ displays a red emission peak near 620 nm with excitation at 396 nm. Efficient energy transfer from Tb3+ to Eu3+ ions takes place in the Ba3GdK(PO4)3F host, and the energy transfer critical distance between Tb3+ and Eu3+ ions along with the resonant energy-transfer mechanism are determined. By tuning the Tb3+/Eu3+ ratio, the emission hue can be modulated from blue-green (0.238, 0.311) to white (0.341, 0.318) and eventually to orange (0.521, 0.335). Moreover, the thermal quenching property of the as-prepared samples was studied in detail, which discloses the high thermal stability.

A novel BiIO4/BiVO4 heterojunction photocatalyst has been successfully developed by a facile hydrothermal route for the first time. X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectra (DRS) were utilized to characterize the crystal structures, morphologies and optical properties of the as-prepared products. Under visible light irradiation (λ > 420 nm), the BiIO4/BiVO4 composite exhibits much better photoelectrochemical performance for rhodamine B (RhB) degradation and photocurrent (PC) generation compared to pure BiIO4 and BiVO4. This significant enhancement on visible-light-driven photocatalytic activity should be ascribed to the formation of the BiIO4/BiVO4 heterojunction, which can result in the high separation and transfer efficiency of photogenerated charge carriers. It was verified by electrochemical impedance spectra (EIS). The active species trapping experiment demonstrated that h+ play a critical role during the photocatalytic process, which is consistent with the supposed photocatalytic mechanism.

•AgIO3 as a novel photocatalyst was synthesized by a facile hydrothermal method.•It exhibits excellent photocatalytic activity both under UV and visible light.•The high photocatalytic activity is attributed to the non-centrosymmetric structure.•AgIO3 also shows high stability resistant to photocorrosion.AgIO3 as a novel photocatalyst was prepared via a facile hydrothermal route. The microstructure, electronic structure, optical and nonlinear optical (NLO) properties of AgIO3 were investigated by a series of experimental and theoretical methods, including X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM), Brunauer–Emmett–Teller (BET), UV–vis diffuse reflectance spectra (DRS), second harmonic generation (SHG) measurements and the first principle calculation. The results revealed that AgIO3 exhibits a strong SHG response and excellent photocatalytic performance with high stability under both UV and visible light irradiation. The advantages of this material, such as large polarizability resulted from the NCS structure, polar IO3− anion and layered structure should be responsible for the high photocatalytic activity of AgIO3. The present work may shed new light on the design of multifunctional materials.

•Bi-based hydroxyl oxalate Bi(C2O4)OH was explored as a novel photocatalyst.•It was successfully synthesized via a facile aqueous precipitation route.•Bi(C2O4)OH can effectively degrade RhB under UV light irradiation.•Hydroxyl radicals (OH) are the main active species for RhB photodegradation.•Its electronic structure was calculated by density functional calculations.A novel Bi-based hydroxyl oxalate Bi(C2O4)OH has been successfully synthesized via a facile aqueous precipitation route, and its photocatalytic activity was investigated for the first time. The as-prepared Bi(C2O4)OH nanorods were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectra (DRS) and photoluminescence (PL) spectra. It possesses an indirect-transition optical band gap of 3.73 eV. The electronic structure, density of states as well as light absorption of Bi(C2O4)OH were studied by the first principle calculations. The photocatalytic performance of the samples was determined by photodegradation of Rhodamine B (RhB) in aqueous solution. The results revealed that RhB can be effectively decomposed by Bi(C2O4)OH, and the sample with reactant molar ratio of 1:2 exhibits the highest photocatalytic activity. The active species trapping experiments over Bi(C2O4)OH indicated that the hydroxyl radicals (OH) are the most important active species in the process of RhB photodegradation.A novel Bi-based hydroxyl oxalate Bi(C2O4)OH has been successfully synthesized via a facile aqueous precipitation route, and its photocatalytic activity was investigated for the first time.

•Sn2SiS4 has been synthesized for the first time.•The SnS6 and SiS4 polyhedra are connected to generate a three-dimensional framework.•Sn2SiS4 has an indirect band gap of 2.00 eV.•Sn2SiS4 exhibits a high visible-light-induced photocatalytic reactivity.The new ternary sulfide Sn2SiS4 has been synthesized via high-temperature solid state reaction. It crystallizes in the centrosymmetric space group P21/c of the monoclinic system. In the structure, the Sn2+ cations are coordinated to a heavily-distorted octahedron of six S atoms or a pentagonal pyramid of six S atoms, both geometries clearly demonstrating the effect of the stereo-chemically active electron lone pair on the Sn coordination environment. These SnS6 polyhedra and the SiS4 tetrahedra are connected to each other via corner and edge-sharing to generate a three-dimensional framework. Based on the diffuse reflectance measurement and the electronic structure calculation, Sn2SiS4 has an indirect band gap of 2.00 eV. Interestingly, Sn2SiS4 exhibits an efficient visible-light-driven photocatalytic activity pertaining to Rhodamine B (RhB) degradation, which is superior to the important photocatalyst C3N4. Moreover, the photocatalytic mechanism was also elucidated based on the active species trapping experiments.Sn2SiS4 contains a three-dimensional framework built by the SnS6 and SiS4 polyhedra and exhibits interesting photocatalytic property.

We developed for the first time an in situ co-crystallization route for fabrication of a heterojunctional photocatalyst g-C3N4/Bi5O7I by adopting melamine and BiOI as coprecursors. This synthetic method enables intimate interfacial interaction with chemical bonding between g-C3N4 and Bi5O7I, which is beneficial for charge transfer at the interface. The photocatalysis properties of g-C3N4/Bi5O7I composites were studied by photodegradation of Rhodamine B (RhB) and phenol and generation of transient photocurrent with illumination of visible-light (λ > 420 nm), The results revealed that the g-C3N4/Bi5O7I composite shows enhanced photocatalytic reactivity compared to the pristine g-C3N4 and Bi5O7I samples. Investigations on the behaviors of charge carriers via electrochemical impedance spectra (EIS) and photoluminescence (PL) spectra suggests that the g-C3N4/Bi5O7I heterojunctional structure constructed of the in situ co-thermolysis approach is responsible for the efficient separation and transfer of photogenerated electrons (e–) and holes (h+), thus giving rise to the higher photocatalytic activity. The present work opens a new avenue for manipulation of high-performance semiconductor heterojunction for photocatalytic and photoelectrochemical application.

•g-C3N4/Ag2CO3 composites were synthesized by a facile in situ precipitation route.•The 1:12 g-C3N4/Ag2CO3 sample shows the most improved photocatalytic performance.•The enhanced photocatalytic activity was attributed to a heterojunction mechanism.•The active species h+ and OH were detected by species trapping experiment.Novel g-C3N4/Ag2CO3 organic–inorganic hybrid photocatalysts have been prepared by a facile in situ precipitation route. The crystal structure and optical property of the as-prepared samples have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and diffuse reflection spectroscopy (DRS). The photocatalytic experiments indicated that the as-prepared g-C3N4/Ag2CO3 photocatalyst exhibited significantly enhanced photocatalytic activity than the pure g-C3N4 and Ag2CO3 samples toward degrading methyl orange (MO) under visible light irradiation (λ > 420 nm). A possible photocatalytic mechanism was proposed based on the photoluminescence (PL) spectra, photocurrent spectra and a series of radical trapping experiments. The remarkably improved photocatalytic performance should be ascribed to the heterostructure between Ag2CO3 and g-C3N4, which greatly promoted the photoinduced charge transfer and inhibited the recombination of electrons and holes.The efficient charge transfer at the interface of g-C3N4/Ag2CO3 heterojunction leads to an effective photoexcited electron–hole separation and promote the photocatalytic activity.

•BaBiO2Br was first explored as a novel photocatalyst.•BaBiO2Br has been successfully synthesized by a solid state reaction.•We systematically synthesized BaBiO2Br in different temperature.•Pure BaBiO2Br can only be obtained at 800 °C and 900 °C.•BaBiO2Br calcinated at 700 °C exhibited the highest photocatalytic activity.A novel Bi-based layered photocatalyst BaBiO2Br was successfully prepared by a solid-state reaction. The as-prepared samples were characterized by XRD, SEM, DRS, PL and FT-IR. The calcination temperature was found to play an important role in controlling synthesis of BaBiO2Br, and pure BaBiO2Br can only be obtained at 800–900 °C. BaBiO2Br with an indirect optical band-gap of 2.93 eV possess photoabsorption ability in both ultraviolet (UV) and visible light regions. The valence band (VB) were mainly occupied by O 2p and Br 4p orbitals, and the conduction band (CB) was composed of Bi 6p orbital. The photodecomposition of rhodamine-B (RhB) experiments revealed that BaBiO2Br can be used as an effective photocatalyst under UV light and visible light irradiation (λ > 400 nm). The sample calcinated at 700 °C exhibited the highest photocatalytic activity among the obtained BaBiO2Br samples, which may be due to the formation of a heterostructure. Among the obtained pure BaBiO2Br, the sample calcinated at 900 °C possesses higher photocatalytic activity than that prepared at 800 °C for its more surface hydroxyl groups at 900 °C.A novel Bi-based layered BaBiO2Br was successfully prepared by a solid state reaction at different temperature. BaBiO2Br has an indirect-transition optical band-gap of 2.93 eV and showed photodegradation of RhB under UV light and visible light irradiation.

Nonbonding layer-structured Y(IO3)3 was successfully prepared by a simple hydrothermal route and investigated as a novel photocatalyst for the first time. Its crystal structure was characterized by X-ray diffraction, high-resolution transmission electron microscopy, and scanning electron microscopy. The optical absorption edge and band gap of Y(IO3)3 have been determined by UV–vis diffuse reflectance spectra. Theoretical calculations of the electronic structure of Y(IO3)3 confirmed its direct optical transition property near the absorption edge region, and the orbital components of the conduction band and valence band (VB) were also analyzed. The photocatalytic performance of Y(IO3)3 was evaluated by photooxidative decomposition of rhodamine B under ultraviolet light irradiation. It demonstrated that Y(IO3)3 exhibits highly efficient photocatalytic activity, which is much better than those of commercial TiO2 (P25) and important UV photocatalysts BiOCl and BiIO4. The origin of the excellent photocatalytic performance of Y(IO3)3 was investigated by electron spin resonance and terephthalic acid photoluminescence techniques. The results revealed that the highly strong photooxidation ability that resulted from its very positive VB position should be responsible for the excellent photocatalytic performance.

Novel 3D hierarchical graphene–BiOI (GR–BiOI) nanoarchitectures have been successfully fabricated via an in situ self-assembly approach for the first time. More attractively, the hierarchical nanoarchitectures can be adjusted by simply controlling the amount of graphene oxide, which determines the improved level of photocatalytic performance. Photochemical measurements reveal that the as-obtained 5% GR–BiOI composite exhibits the most significantly enhanced photocatalytic activities for the degradation of Rhodamine B (RhB) and photocurrent (PC) generation under visible light irradiation (λ > 420 nm). This remarkably improved photocatalytic performance of GR–BiOI could be attributed to the well-established interfacial interaction between graphene and BiOI, which can greatly facilitate the separation and easy transfer of photogenerated electrons and holes to generate abundant ˙O2− and ˙OH active species with powerful oxidability. This was verified by the photoluminescence (PL) spectra, electrochemical impedance spectra (EIS), active species trapping, and ˙O2− and ˙OH quantification experiments. Our work provides a new strategy for the construction of hierarchical nanoarchitectures of high-performance composite photocatalysts and paves an alternative way to the design and synthesis of graphene-based composites for special applications.

The g-C3N4/BiIO4 composite photocatalysts were successfully synthesized using a simple-mixed-calcinations method, and their photocatalytic activities for degradation of rhodamine B (RhB) under visible-light (λ > 420 nm) were investigated for the first time. The crystal structure and optical property of the as-synthesized samples were characterized by XRD, FTIR, SEM, TEM, HRTEM and DRS spectroscopy. The photodegradation experiments indicated that the g-C3N4/BiIO4 composite photocatalyst displays a higher photocatalytic activity than the two individuals, which was also confirmed by the PL spectra and photoelectrochemical experiments. This remarkably improved photocatalytic performance can be attributed to the heterojunction structure of g-C3N4/BiIO4 composites, which possess stronger oxidation and reduction capability, thus resulting in the efficient separation of photoinduced charge carriers as demonstrated in the active species experiments. The present study will be beneficial for the design of high performance photocatalysts.

Through the introduction of a new Bi-based semiconductor BiIO4, the novel BiIO4/Bi2WO6 heterojunctions composed of two layered structures were successfully fabricated by a one-step hydrothermal method. The as-prepared samples were thoroughly characterized by XRD, SEM, TEM, HRTEM, XPS, ICP, DRS and PL spectra technologies. The photodegradation experiments indicated that the BiIO4/Bi2WO6 composites showed much higher visible-light-driven (VLD) photocatalytic activity than those of either individual BiIO4 and Bi2WO6 for rhodamine B (RhB) degradation, which are attributed to the high separation of photogenerated electron–hole pairs resulted by the BiIO4/Bi2WO6 heterojunctions. This is the first report of the photocatalytic activity of the new Bi-based compound BiIO4 and BiIO4/Bi2WO6 composites under visible light. Moreover, our research provided a new layered semiconductor, which can be applied in the future for heterojunction construction and energy band structure design.

Energy-levels well-matched Mg1−xCuxWO4 (0.1 < x < 0.5)/Bi2WO6 heterojunctions with Type II staggered conduction bands and valence bands have been successfully constructed by band gap engineering based on solid-solution design and synthesized by a facile one-step hydrothermal method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectra (DRS) were utilized to characterize the crystal structures, morphologies and optical properties of the as-prepared products. The as-designed Mg0.7Cu0.3WO4/Bi2WO6 heterojunctions consisting of nanocube and nanoplate structures exhibit much higher visible-light-driven (VLD) photocatalytic activity than the two individual components for the degradation of RhB and photocurrent generation. The photoluminescence (PL) spectra, photoelectrochemical measurement, active-species trapping and quantification experiments all indicated that the fabrication of energy-levels well-matched overlapping band structures can greatly facilitate the separation and easy transfer of photogenerated electrons and holes, thus resulting in remarkably enhanced photocatalytic activity. This work provides a novel strategy for semiconductor heterojunction construction and energy band structure regulation.

•New borate–malate crystals NaB(DL-C4H4O5)2 and CsB(DL-C4H4O5)2⋅H2O have been grown.•They display diverse framework geometries attributable to the size of the cations.•NaB(DL-C4H4O5)2 crystallizes in the noncentrosymmetric monoclinic space group P2.•Both crystals have absorption edges about 220 nm in the UV region.•NaB(DL-C4H4O5)2 exhibits a NLO efficiency of 2 times that of KDP (KH2PO4) standard.Two new alkali-metal bidenate borate–malate NaB(DL-C4H4O5)2 and CsB(DL-C4H4O5)2⋅H2O have been grown by the facile slow evaporation method through the introduction of acetone as solvent. The crystal structures were determined by single crystal X-ray diffraction. The stoichiometrically equivalent materials crystallize in three-dimensional framework structures and have the same structural unit [B(C4H4O5)2]−. However, both crystals exhibit very diverse framework geometries attributable to the size of the alkali-metal cations, which also leads to the different space groups and macroscopic centricities as proven by SHG test. The noncentrosymmetric NaB(DL-C4H4O5)2 was found to exhibit phase-matchable NLO intensity as high as two times that of KDP standard and a short-wavelength absorption onset at 220 nm. Moreover, both crystals have also been characterized by Infrared spectroscopy and thermogravimetric analysis.Graphical abstractTwo novel semiorganic borates NaB(DL-C4H4O5)2 and CsB(DL-C4H4O5)2H2O display different framework geometries attributable to the size of the alkali-metal cations. NaB(DL-C4H4O5)2 exhibits SHG intensity as high as two times that of KDP.

•Bi-based phosphates Na3Bi2(PO4)3 and Na3Bi(PO4)2 were explored as photocatalysts.•They were successfully synthesized by a solid-state reaction.•The band gaps of Na3Bi2(PO4)3 and Na3Bi(PO4)2 are smaller than that of BiPO4.•MB can be photodecomposed by Na3Bi2(PO4)3 and Na3Bi(PO4)2 under UV light.•Na3Bi(PO4)2 exhibits a higher photocatalytic activity than BiPO4.Two Bi-based phosphate photocatalytic materials Na3Bi2(PO4)3 and Na3Bi(PO4)2 have been successfully synthesized by a solid-state reaction. Compared to BiPO4 with band gap 3.77 eV, the introduction of Na3PO4 resulted in smaller band gaps of 3.6 and 3.01 eV for Na3Bi2(PO4)3 and Na3Bi(PO4)2, respectively. The photocatalytic activities of the samples were determined by photooxidative decomposition of methylene blue (MB) in aqueous solution. The results revealed that both Na3Bi(PO4)2 and Na3Bi2(PO4)3 can be used as effective photocatalysts under UV irradiation, and the former exhibits a higher photocatalytic activity compared to BiPO4, which may be attributed to more light absorption in the UV range. It is a novel way to regulate the band-gaps of semiconductors and explore new photocatalytic materials.Two novel Bi-based phosphate photocatalysts Na3Bi2(PO4)3 and Na3Bi(PO4)2 were successfully developed. The design for Bi-based phosphates with narrow band gaps has been realized.

•Bi4NbO8Br was explored as a novel photocatalyst with visible light response.•Bi4NbO8Br has been successfully synthesized by a solid state reaction.•We systematically synthesized Bi4NbO8Br in different temperatures.•Pure Bi4NbO8Br can only be obtained at 700 °C, 750 °C and 800 °C.•Bi4NbO8Br calcinated at 750 °C exhibited the highest photocatalytic activity.A novel visible-light-driven Bi-based layered photocatalyst Bi4NbO8Br was successfully prepared by a solid state reaction. The calcination temperature was found to play an important role in controlling synthesis of Bi4NbO8Br, and pure Bi4NbO8Br can only be obtained at 700 °C–800 °C. The as-prepared samples were characterized by XRD, SEM, DRS and PL. Bi4NbO8Br has an indirect-transition optical band-gap of 2.34 eV, and the ECB and EVB are estimated to be 0.63 eV and 2.97 eV, respectively. The photocatalytic activities of the samples were determined by decomposition of rhodamine-B (RhB) in aqueous solution under visible light illumination. The results revealed that the sample calcinated at 750 °C exhibited the highest photocatalytic activity among the pure Bi4NbO8Br samples. The sample calcinated at 850 °C, composed of BiNbO4 and Bi4NbO8Br, showed higher photocatalytic activity than that calcinated at 750 °C, which may be due to the formation of heterostructure.Bi4NbO8Br was successfully prepared by a solid state reaction at different temperatures. Bi4NbO8Br has an indirect-transition optical band-gap of 2.34 eV and showed photodegradation of RhB under visible-light irradiation.

The novel Ce and F codoped Bi2WO6 samples have been successfully obtained by a facile one-step hydrothermal reaction for the first time. They were characterized by X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectra (DRS) and photoluminescence (PL) spectra. The presence of Ce3+, Ce4+, and F– dopants in Bi2WO6 was confirmed by XPS. The change of microstructure and optical band gap has also been observed after the doping of Ce and F. Under visible light, the as-synthesized plate-like F–Ce–Bi2WO6 sample exhibits a much better visible-light-responsive photocatalytic performance than pure Bi2WO6 for the degradation of RhB and photocurrent (PC) generation. The mechanism of high photcatalytic activity was also suggested on the basis of the PL spectra, electrochemical impedance spectra (EIS), and active species trapping measurements. The results indicated that the synergistic effect of the Ce and F dopants is responsible for the efficient separation and migration of photoinduced charge carriers, thus resulting in the remarkably improved photocatalytic activity.

Deep-UV coherent light generated by nonlinear optical (NLO) materials possesses highly important applications in photonic technologies. Beryllium borates comprising anionic planar layers have been shown to be the most promising deep UV NLO materials. Here, two novel NLO beryllium borates Na2Be4B4O11 and LiNa5Be12B12O33 have been developed through cationic structural engineering. The most closely arranged [Be2BO5]∞ planar layers, connected by the flexible [B2O5] groups, have been found in their structures. This structural regulation strategy successfully resulted in the largest second harmonic generation (SHG) effects in the layered beryllium borates, which is ∼1.3 and 1.4 times that of KDP for Na2Be4B4O11 and LiNa5Be12B12O33, respectively. The deep-UV optical transmittance spectra based on single crystals indicated their short-wavelength cut-offs are down to ∼170 nm. These results demonstrated that Na2Be4B4O11 and LiNa5Be12B12O33 possess very promising application as deep-UV NLO crystals.

A novel fluorine beryllium borate crystal Sr0.23Ca0.77Na2Be2B2O6F2 has been grown by high temperature solution method from its self-flux system for the first time. Crystal structure of this compound was determined by single crystal X-ray diffraction. It crystallizes in the trigonal space group R3¯ (No. 148) with lattice parameters a=4.6608(6) Å, c= 27.516(5) Å, Z=3, V= 517.65(13) Å3. The crystal displays a sandwich-like layered configuration along c axis with the infinite (Be6B6O12F3)∞ non-bonding double layer formed by two (Be3B3O6F3)∞ single layers in the a-b plane. The single layer was composed of BO3 triangle and BeO3F tetrahedron, both of which are the most favorable anionic groups in deep ultraviolet (UV) region. The structural relationship between the title compound and related fluorine beryllium borate was discussed. Optical transmittance spectrum reveals this compound has a very wide transmission range (190nm – 8μm). The IR spectrum and thermal behavior of Sr0.23Ca0.77Na2Be2B2O6F2 were also reported.Graphical abstractThe crystal displays a sandwich-like layered configuration along c axis with the infinite (Be3B3O6F3)∞ layers in the a-b plane.Highlights► A new beryllium borate Sr0.23Ca0.77Na2Be2B2O6F2 was synthesized. ► It exhibits a sandwich-like layered structure formed by (Be6B6O12F3)∞ double layers. ► The (Be3B3O6F3)∞ single layer were composed of BO3 triangles and BeO3F tetrahedrons. ► This compound has a very wide transparency range of wavelengths from 190 nm to 8 μm.

A novel beryllium borate CsBe4(BO3)3 has been grown in crystals by high-temperature flux method using spontaneous nucleation technique for the first time. The crystal structure of this compound was determined by single crystal X-ray diffraction analysis. It crystallizes in the orthorhombic space group Pnma with lattice parameters a = 8.3914(5) Å, b = 13.3674(7) Å, c = 6.4391(3) Å, Z = 4, V = 722.28(7) Å3. The crystal takes the same structure type as Rb analog based on the units of BO3 triangles and BeO4 tetrahedrons, displaying a three-dimensional tunnel structure with Cs atoms filling in the cages. The IR spectrum confirms the presence of BO3 groups and the UV–vis–IR diffuse reflectance spectrum exhibits this compound has a short UV cut-off edge below 200 nm. Band structures and density of states were calculated.Graphical abstractHighlights► A new beryllium borate CsBe4(BO3)3 was synthesized and crystals were obtained by flux method. ► CsBe4(BO3)3 crystallizes in a new structure type. ► It exhibits a three-dimensional zeolite-like structure with Cs atoms filling in the cages. ► The basic structural units are [Be2BO4]− groups composed of BO3 and BeO4. ► The UV cut-off edge is below 200 nm.

Through the combination of Bi3+ and a large negative charge ion (BO3)3–, two novel Bi-based borate photocatalysts Bi4B2O9 and Bi2O2[BO2(OH)] with layered structure have been successfully developed. For the first time, the borates were investigated as photocatalysts. They were synthesized by solid-state reaction and hydrothermal method, respectively, and further characterized by XRD, SEM, TEM, HRTEM, and DRS. Bi4B2O9 and Bi2O2[BO2(OH)] possess direct and indirect transition optical band gaps of 3.02 and 2.85 eV, respectively. Density functional calculations revealed that the valence band (VB) and conduction band (CB) of both borates were composed of hybridized states of the O 2p and Bi 6p or 6s orbitals, and a large dispersion was observed in the energy band of Bi2O2[BO2(OH)]. The photodecomposition experiments demonstrated that Bi4B2O9 and Bi2O2[BO2(OH)] can be used as effective photocatalysts under simulated solar irradiation, and Bi2O2[BO2(OH)] exhibits the high photocatalytic activity, which is 2.5 and 3.2 times compared with that of P25 and Bi2O2CO3, respectively. Moreover, the photocurrent conversion further confirmed that Bi4B2O9 and Bi2O2[BO2(OH)] were potential photofunctional materials. The layered structure with (Bi2O2)2+ layer, hybridized and dispersion energy band, and large negative charge of (BO3)3– ion should be responsible for the high photocatalytic activity of Bi2O2[BO2(OH)].

•Tb3+/Eu3+ co-doped BiPO4 nanoparticles have been obtained by a hydrothermal route.•Tunable PL emission from green to red is realized in Tb3+/Eu3+–BiPO4 phosphor.•A warmwhite color is obtained in the codoped sample by tuning the Tb3+/Eu3+ ratio.•Doped BiPO4 exhibit highly enhanced photocatalytic activity for RhB degradation.We demonstrated for first time the tunable photoluminescence (PL) properties and photocatalytic activity of the Tb3+ and Eu3+ co-doped BiPO4 assemblies. They are fabricated via a facile hydrothermal approach. Through co-doping of Eu3+ and Tb3+ ions and changing the doping ratio, the emission color of the co-doped BiPO4 phosphors can be tuned precisely from green to yellow and red. Meanwhile, a very efficient energy transfer from Tb3+ to Eu3+ can be observed. Fascinatingly, a warmwhite color has been realized in the co-doped sample by tuning the ratio of Tb3+/Eu3+ to a certain value as displayed in the CIE chromaticity diagram. The doped BiPO4 samples also exhibit significantly enhanced photocatalytic activity compared to the pristine BiPO4 pertaining to Rhodamine (RhB) degradation under UV light. This enhancement should be attributed to the trapping electron effect induced by ion doping that endows BiPO4 with high separation of photoinduced electron–hole pairs, thereby greatly promoting the photocatalytic reactivity. It was corroborated by the electrochemical impedance spectra (EIS). Moreover, the crystal structure, microstructure and optical properties of as-prepared samples were investigated in details.

The development of high-performance visible-light photocatalysts with a tunable band gap has great significance for enabling wide-band-gap (WBG) semiconductors visible-light sensitive activity and precisely tailoring their optical properties and photocatalytic performance. In this work we demonstrate the continuously adjustable band gap and visible-light photocatalysis activation of WBG BiOIO3via iodine surface modification. The iodine modified BiOIO3 was developed through a facile in situ reduction route by applying BiOIO3 as the self-sacrifice template and glucose as the reducing agent. By manipulating the glucose concentration, the band gap of the as-prepared modified BiOIO3 could be orderly narrowed by generation of the impurity or defect energy level close to the conduction band, thus endowing it with a visible light activity. The photocatalytic assessments uncovered that, in contrast to pristine BiOIO3, the modified BiOIO3 presents significantly boosted photocatalytic properties for the degradation of both liquid and gaseous contaminants, including Rhodamine B (RhB), methyl orange (MO), and ppb-level NO under visible light. Additionally, the band structure evolution as well as photocatalysis mechanism triggered by the iodine surface modification is investigated in detail. This study not only provides a novel iodine surface-modified BiOIO3 for environmental application, but also provides a facile and general way to develop highly efficient visible-light photocatalysts.

We disclose the fabrication of a mediator-free direct Z-scheme photocatalyst system BiVO4/g-C3N4 using a mixed-calcination method based on the more reliable interfacial interaction. The facet coupling occurred between the g-C3N4 (002) and BiVO4 (121), and it was revealed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM). The crystal structure and optical properties of the as-prepared samples have also been characterized by Fourier-transform infrared (FTIR), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectra (DRS) in details. The photocatalytic experiments indicated that the BiVO4/g-C3N4 composite photocatalysts display a significantly enhanced photocatalytic activity pertaining to RhB degradation and photocurrent generation (PC) compared to the pristine BiVO4 and g-C3N4. This remarkably improved photocatalytic performance should be attributed to the fabrication of a direct Z-scheme system of BiVO4/g-C3N4, which can result in a more efficient separation of photoinduced charge carriers than band–band transfer, thus endowing it with the much more powerful oxidation and reduction capability, as confirmed by the photoluminescence (PL) spectra and electrochemical impedance spectra (EIS). The Z-scheme mechanism of BiVO4/g-C3N4 heterostructure was verified by a series of combined techniques, including the active species trapping experiments, NBT transformation and terephthalic acid photoluminescence probing technique (TA-PL) over BiVO4/g-C3N4 composites and the pristine samples. The present work not only furthered the understanding of mediator-free Z-scheme photocatalysis, but also shed new light on the design of heterostructural photocatalysts with high-performance.

Different samples of gadolinium (Gd)-doped Bi2WO6 were obtained by hydrothermal means, and their photocatalytic activities for degradation of rhodamine B (RhB) under visible-light irradiation were researched. The successful incorporation of Gd3+ ions into Bi2WO6 was detected by XRD and XPS, and the prepared samples have also been characteriazed by SEM, TEM, HRTEM, DRS, and PL. The results suggested that Gd doping has great influences on the visible-light photocatalytic activity as well as the microstructure. Appropriate doping content greatly improve photocatalytic activity due to the electron shallow-trapping mechanism for the efficient separation of electron and hole pairs, and the 1% Gd–Bi2WO6 sample with flower-like structure exhibited the highest photocatalytic activity. It has already been confirmed by photocurrent generation and electrochemical impedance spectra. The present research provides a simple and valid method for improving the visible-light-responding photocatalytic activity and fabricating hierarchical architectures of Bi2WO6.

Developing high-performance photocatalytic materials is of huge significance and highly desirable for fulfilling the pressing need in environmental remediation. In this work, we demonstrate the use of bismuth nitrate Bi2O2(OH)(NO3) as an absorbing photocatalyst, which integrates multiple superiorities, like a [Bi2O2]2+ layered configuration, a non-centrosymmetric (NCS) polar structure and highly reactive {001} facets. Bi2O2(OH)(NO3) nanosheets are obtained by a facile one-pot hydrothermal route using Bi(NO3)3·5H2O as the sole raw material. Photocatalysis assessment revealed that Bi2O2(OH)(NO3) holds an unprecedented photooxidation ability in contaminant decomposition, far out-performing the well-known photocatalysts BiPO4, Bi2O2CO3, BiOCl and P25 (commercial TiO2). Particularly, it displays a universally powerful catalytic activity against various stubborn industrial contaminants and pharmaceuticals, including phenol, bisphenol A, 2,4-dichlorophenol and tetracycline hydrochloride. In-depth experimental and density functional theory (DFT) investigations co-uncovered that the manifold advantages, such as large polarizability and rational band structure, as well as exposed {001} active facets, induced robust generation of strong oxidating superoxide radicals (˙O2−) in the conduction band and hydroxyl radicals (˙OH) in the valence band, thus enabling Bi2O2(OH)(NO3) to have a powerful and durable photooxidation capability. Bi2O2(OH)(NO3) also presents high photochemical stability. This work not only rendered a highly active and stable photocatalyst for practical applications, but also laid a solid foundation for future initiatives aimed at designing new photoelectronic materials by manipulating multiple advantageous factors.

Development of efficient photocatalysts with both photoinduced oxidation and reduction properties is of great importance for environmental and energy applications. Herein, we report the fabrication of CeO2/g-C3N4 hybrid materials by a simple in situ co-pyrolysis method using Ce(IO3)3 and melamine as precursors. The CeO2/g-C3N4 composite catalysts possess outstanding photocatalytic activity for phenol degradation and NO removal under visible light irradiation. The degradation efficiency reaches up to 68.5 and 17.3 times higher than that of pure CeO2 and g-C3N4, respectively. Significantly, it simultaneously exhibits an enhanced hydrogen production rate, which is 1.5 times that of the pure g-C3N4. The highly enhanced photo-induced oxidation and reduction activity could be attributed to the construction of a CeO2/g-C3N4 n–n type heterojunction established by our in situ co-pyrolysis route, which enables intimate interaction across the phase interfaces; this facilitates separation and transfer of photoexcited charge carriers. This study could not only provide a facile and general approach to the fabrication of high-performance carbon-nitride-based photocatalytic materials, but also increase our understanding further on designing new hybrid composite photocatalysts for multi-functional applications.

We herein report a facile and general approach to modulating the band energy level of semiconductors for visible-light photocatalysis via iodide surface decoration. This strategy enables the wide-band-gap Bi2O2CO3 to possess a continuously tunable band gap and profoundly boosted visible-light photocatalytic performance for dye degradation and NO removal.

We, for the first time, demonstrate band-gap-broadening as a new approach to remarkably enhance the photocatalytic activity of Br− substituted BiOI photocatalysts, which were fabricated via a facile chemical precipitation route. The successful incorporation of Br− ions into the crystal lattice of BiOI was confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The photocatalytic experiments demonstrated that all of the Br–BiOI samples exhibited highly improved photocatalytic performances pertaining to rhodamine B (RhB) and phenol degradation under visible light (λ > 420 nm). The active species trapping and electron spin resonance (ESR) experiments also suggested that more superoxide radicals (˙O2−), serving as the main active species, were generated over Br–BiOI than pristine BiOI in the photooxidation process. Based on the results from experiments and theoretical calculations, the enhancement of photocatalytic activity should be attributed to the lowered valence band (VB) potential and enlarged band gap induced by the Br− replacement, which greatly facilitated the high separation of photoinduced electron–hole pairs, as verified by the photoluminescence (PL) experiments, electrochemical impedance spectra (EIS) and Bode-phase spectra. This work sheds light on a new method to improve the photocatalytic performance of photocatalysts.