In our work, we have successfully synthesized WO3 nanosheets via a simple, fast, and organic additives-free hydrothermal method. The obtained products are 200–500 nm-sized with square corners and high crystallinity. A possible formation mechanism of WO3 nanosheets is discussed in this study based on the experimental results and our understanding. WO3 nanosheets modified with Pt exhibit enhanced photocatalytic activity of tetracycline compared with bare WO3 nanosheets under visible-light irradiation (λ > 420 nm). Furthermore, the effects of Pt as cocatalyst can be clearly drawn, and the degradation ratio of 2% Pt/WO3 nanosheets is over 3 times that of bare WO3 nanosheets, which is reasonable to expect the obvious Pt-dependent activity. The addition of 10 mL of iso-propanol leads to a considerable decreased degradation ratio (DR) of tetracycline (TC) on 2% Pt/WO3 photocatalysts, further indicating the ·OH radicals do exist in the process of the photocatalytic oxidation (PCO) of TC.

Spatial separation of photogenerated electron-hole pairs is one of the most important factors that determine the efficiency of a photocatalyst. It is well acknowledged that the fabrication of heterogeneous photocatalysts with two different inorganic semiconductors is a good strategy to effectively improve the charge separation of electrons and holes. This study describes a novel visible light-induced g-C3N4/Bi3TaO7 composite photocatalyst with superior photocatalytic properties toward the degradation of tetracycline (TC) by visible light irradiation. The formation of heterojunctions significantly improves the separation efficiency of photogenerated carriers, which is confirmed by the photocurrent density and electrochemical impedance spectroscopy. Electron spin resonance examination and trapping experiments confirm that the photoinduced active species (˙OH and ˙O2−) are responsible for the degradation of tetracycline. Based on the experimental results, a possible Z-scheme system reaction mechanism for the g-C3N4/Bi3TaO7 composite towards the degradation of TC under visible light was proposed.

This paper presents for the first time a novel method of depositing plasmonic Bi nanoparticles on BiOCl nanosheets (Bi/BiOCl) via insitu photoelectroreduction, and Bi/BiOCl as the photocathode enabled solar water splitting in a TiO2–Bi/BiOCl photoelectrochemical (PEC) system. It is one of the challenges to understand the relationship between the PEC performance and the composite ratio of Bi/BiOCl, and the density functional theory calculation results show that charges obviously transfer from the Bi cluster to the BiOCl (001) surface. The structure of Bi/BiOCl photocathode has been successfully optimized, according to the current–potential curves and charge injection efficiency. The highly enhanced PEC activity could be attributed to the dual roles of Bi nanoparticles in enhancing the charge transfer and surface plasmon resonance (SPR) effect. More importantly, the optimal Bi/BiOCl photocathode achieved a solar hydrogen evolution rate of 2.4 µmol h−1 under full spectrum illumination (100 mW cm−2).

It is well known that bimetallic nanomaterials usually exhibit unique catalytic, optical, electric and magnetic properties due to the synergistic effect between different metals. In this work, we reported on a scalable method to fabricate an AuPt bimetallic core–shell nanoparticles loaded hematite (α-Fe2O3) photoanode for solar-driven photoelectrochemical water oxidation. Compared to single metal-modified α-Fe2O3 photoanodes, the AuPt bimetallic core–shell nanoparticles loaded α-Fe2O3 photoanodes exhibited a synergistic effect for photoelectrochemical water oxidation. The photocurrent density of AuPt0.2/α-Fe2O3 was boosted to 0.83 mA cm−2 at 1.23 V versus a reversible hydrogen electrode in a neutral electrolyte (0.5 M Na2SO4 aqueous solution) under 45 W xenon lamp irradiation. The incident photon-to-photocurrent efficiency value of optimum AuPt0.2/α-Fe2O3 was estimated to be 58%, which was significantly higher than the single metal-modified α-Fe2O3 and pristine α-Fe2O3 photoanodes (<10%). Electrochemical impedance spectroscopy and Mott–Schottky analysis confirmed that the Schottky junction formed by the AuPt bimetallic nanoparticles and α-Fe2O3 led to enhanced charge separation and band bending, resulting in a negative shift of onset potential. Based on the experimental and characterized results, a possible mechanism was proposed. This work provides an important reference for the design of other bimetallic-modified photoanodes for application in energy conversion.

This paper presents a facile one-step approach for the syntheses of MoS2/GC (GC = graphitic carbon) with sodium alginate as the biomass carbon source. The MoS2/GC composites showed enhanced photocatalytic activity for degradation of methylene blue under visible light irradiation. The MoS2/GC (2 : 1) composite shows the best performance and 99.2% methylene blue can be removed in 100 minutes. GC plays an important role in the fast separation and transfer of photogenerated charges across interfaces. The activity and stability performances suggest that the MoS2/GC composite has great potential for practical industrial wastewater treatment.

In this work, novel hierarchical cobalt sulfide@nickel hydroxide [Co9S8@Ni(OH)2] core–shell nanotube arrays supported on carbon fibers have been designed logically and synthesized for use as supercapacitors. The one-dimensional Co9S8 nanotubes (NTs) serve as an ideal backbone to improve the electrical conductivity of Ni(OH)2 nanosheets, whereas the ultrathin and redox active Ni(OH)2 nanosheets electrodeposited on the Co9S8 NTs greatly enhance the surface area and provide more electroactive sites for faradaic reaction. The optimized Co9S8@Ni(OH)2 electrode shows high specific capacitances of 149.44 mA h g−1 at the current density of 1 A g−1 and 75 mA h g−1 even at 10 A g−1. An asymmetric supercapacitor was successfully assembled with this unique hybrid nanostructure as the anode and an active carbon film as the cathode. The as-fabricated device shows high energy density (31.35 W h kg−1 at 252.8 W kg−1), high power density (2500 W kg−1 at 12.5 W h kg−1), as well as a long-term cycle stability (97.3% retention of its initial capacitance after 5000 cycles). The as-prepared hierarchical nanostructure shows great potential as a promising electrode material for energy storage applications.

Graphitic carbon nitride (GCN) nanosheets with unique physicochemical properties have received increasing attention in the area of photocatalysis, yet tunable thickness for the straightforward production of this graphite-like two-dimensional (2D) nanomaterial remains a challenge. In this work, GCN nanosheets with different thicknesses were firstly prepared by a direct calcination of melamine supramolecular aggregates (MSA) obtained from a hydrochloric acid (HCl)-induced hydrothermal assembly approach. The resultant nanosheets over nanometer scale thickness could be precisely controlled via simply adjusting the HCl concentration. Compared to the bulk GCN (BGCN), the thinner nanosheets possessed a high specific surface area, a large electronic-band structure, and fast charge separation ability. The thinnest nanosheets with a thickness of approximately 4 nm exhibited excellent visible-light-driven photocatalytic water splitting performance in hydrogen evolution (524 μmol h−1 g−1), which is over 9-fold higher than the BGCN powder. This work provides a thickness-dependent strategy for the preparation of metal-free GCN nanosheets and develops a promising 2D photocatalyst for application in solar energy conversion.

In TiO2 both advantages (stability and low cost) and disadvantages (large bandgap) coexist, so how to optimize a bare TiO2 electrode is a continuous hot topic for the construction of suitable photoelectrochemical (PEC) devices based on TiO2 for water splitting. This paper reports a facile and simple fabrication of a TiO2/RGO/C3N4 photoelectrode for PEC splitting of water. Its heterostructure configuration has been characterized and confirmed by XRD, Raman spectroscopy, XPS, TEM and STEM. The introduction of both RGO and C3N4 film onto the surface of TiO2 is mainly due to the fact that C3N4 has a strong photoelectric ability to respond to visible light and RGO plays an important role in the fast transfer of photogenerated charges across interfaces. Photocurrent and monochromatic incident photon-to-photocurrent efficiency (IPCE) of the titled heterostructure have been obviously improved, and the IPCE value (0.5 V vs. AgCl/Ag) of TiO2/RGO/C3N4 was estimated to be up to 28% at a wavelength of 400 nm.

Novel Z-scheme InVO4/CdS heterojunction photocatalysts have been successfully synthesized for the first time via a microwave-assisted process, followed by a mild hydrothermal method. The crystal structures, morphologies and sizes, chemical compositions and optical properties of the prepared photocatalysts were characterized via X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), and photocurrent measurements. Results showed that the prepared InVO4/CdS heterojunctions were composed of about 15 nm InVO4 nanoparticles and 1.5 μm CdS microspheres, and all heterojunctions exhibited good photoabsorption in the visible light region. The photocatalytic activity of the obtained samples was carefully evaluated via the degradation of rhodamine B (RhB) and ciprofloxacin (CIP) under visible light irradiation (λ > 420 nm). Compared to that of bare InVO4 and CdS, the InVO4/CdS heterojunctions exhibited significantly enhanced photocatalytic activity for RhB and CIP degradation. Moreover, the 40 wt% InVO4-coupled CdS composite displayed the highest catalytic efficiency for RhB photodegradation, which is about 59.4 and 4.8 times higher than that of pure InVO4 and CdS, respectively. In addition, the active species trapping experiment and electron spin resonance (ESR) measurement demonstrated that h+ and ˙O2− radicals were the predominant active species in the photocatalytic reaction process. Furthermore, the possible enhanced photocatalytic mechanism of InVO4/CdS heterojunctions was also proposed based on the band position measurements and ESR analysis.

Heterojunction photocatalysts composed of CdIn2S4 (CIS) nanocrystals and graphitic carbon nitride (g-C3N4) nanosheets (CN) have been synthesized using a simple two-step wet chemistry method. In this system, CN nanosheets not only act as a substrate for the growth and uniform distribution of CIS nanocrystals but also play a key role in the photocatalytic degradation of organic pollutants with high efficiency. The CdIn2S4/g-C3N4 (CIS/CN) heterojunction photocatalysts exhibited better photocatalytic activity than that of pristine CIS and CN in photocatalytic degradation of both an organic dye (methyl orange) and an antibiotic (tetracycline hydrochloride). The enhanced photocatalytic performance might be ascribed to the formation of a heterojunction structure with strong interface interaction, which is beneficial to the photoinduced charge transfer between CIS and CN and efficient to accelerate the seperation of photogenerated electrons and holes. The as-synthesized heterojunction photocatalysts also showed good photocatalytic stability. After four cycles, the photocatalytic activity almost remains unchanged. The heterojunction photocatalysts with excellent photocatalytic performance and reusability may provide a new sight in the development of a photocatalyst with high efficiency for practical application of water purification.

Hierarchical Bi2S3 nanoflowers consisting of one-dimensional nanorods have been successfully synthesized via a topotactic transformation process. In this fabrication route, hierarchical Bi2WO6 nanoflowers composed of two-dimensional nanosheets were used as the precursor template. Investigated by a time-dependent experiment, the possible formation mechanism of hierarchical Bi2S3 nanoflowers has been proposed. Furthermore, the key role played by thioacetamide (TAA) in the formation of hierarchical structures has also been investigated by controlling its content. In addition, the as-fabricated hierarchical Bi2S3 nanoflowers exhibited high specific capacitance and electrochemical stability, and the intriguing capacitive behavior might be ascribed to their special three-dimensional hierarchical structure.

We presented the fabrication of N doped NiS2 nanoarrays using NH3·H2O as the dopant precursor for the electrocatalytic OER. N doping primarily affects the configuration of electrons and the density of d-states near the Fermi level, together with the adsorption of the OER intermediate, thus overcoming the intrinsic limits of reaction kinetics.

Graphitic carbon nitride (g-C3N4) nanosheets with unique structural and electronic properties have received much attention in photocatalysis, yet the direct synthesis of ultrathin g-C3N4 is still a big challenge. Herein, high-performance g-C3N4 nanosheets were firstly prepared by directly thermal calcination of the hydrothermally pretreated melamine as precursor. Multiple techniques were carried out to characterize the as-prepared samples. Results shown that the morphologies, microstructures, and physicochemical properties of as-synthesized samples are strongly depended on the hydrothermal temperature. The desired g-C3N4 nanosheets with a thickness of around 3 nm could be synthesized through an optimized 200 °C hydrothermal pretreatment. Compared to the bulk g-C3N4, the ultrathin g-C3N4 nanosheets possessed high specific surface area, large electronic band structure, and fast photoinduced electron-hole separation capability. As a consequence, the resultant nanosheets exhibited excellent visible-light-driven photocatalytic water splitting performance for hydrogen evolution (503 μmol h−1 g−1), which is over 6 times higher than the bulk powder. This work highlights a feasible but simple strategy for the production of ultrathin graphite-like nanosheets and develops an efficient metal-free nanomaterial for application in energy conversion.Download high-res image (216KB)Download full-size image

•Nanosheets of Co3O4 nanomaterials were synthesized in mediates of EG and water.•Co3O4 nanosheets showed higher performance for oxidations of CO and methane.•The more active oxygen species in the Co3O4 nanosheets were contributed to the higher performance.Co3O4 nanomaterials were synthesized by hydrothermal method and were applied for low temperature CO oxidation and methane combustion. The addition of ethylene glycol and its concentration significantly influenced the size and shape of the Co3O4 oxides. Nanosheets of Co3O4 were synthesized in ethylene glycol solution and nanospheres were formed in water. The activity of oxygen species in the nanosheets and nanospheres were characterized by hydrogen/methane programmed reduction, oxygen programmed desorption and XPS. The results showed that the Co3O4 nanosheets exhibited more active oxygen species than the Co3O4 nanospheres, leading to the higher activity in the oxidative reactions. The study demonstrated the importance of active oxygen species in Co3O4 catalysts to achieve high catalytic performance towards the carbon monoxide and methane elimination at low temperatures.Download high-res image (189KB)Download full-size image

•CuS/g-C3N4 photocatalysts were synthesized by in-situ growth method.•The catalysts showed excellent H2-production activity.•The enhanced photocatalytic mechanism was based on interfacial charge transfer.In this work, novel CuS/g-C3N4 composite photocatalysts were successfully prepared via a simple in-situ growth method. CuS nanoparticles, with an average diameter of ca.10 nm, were well dispersed on the surface of g-C3N4, revealing that g-C3N4 nanosheets were promising support for in-situ growth of nanosize materials. The CuS/g-C3N4 composites exhibited highly enhanced visible light photocatalytic H2 evolution from water-splitting compared to pure g-C3N4. The optimum photocatalytic activity of 2 wt% CuS/g-C3N4 composite photocatalytic H2 evolution was about 13.76 times higher than pure g-C3N4. The enhanced photocatalytic activity is attributed to the interfacial charge transfer (IFCT). In this system, electrons in the valence band (VB) of g-C3N4 can transfer directly to CuS clusters, causing the reduction of partial CuS to Cu2S, which can act as an electron sink and co-catalyst to promote the separation and transfer of photo-generated electrons. The accumulated photoinduced electrons in CuS/Cu2S clusters could effectively reduce H+ to produce H2. This work provides a possibility for constructing low-cost CuS as a substitute for noble metals in the photocatalytic production of H2 via a facile method based on g-C3N4.

•Ta2O5 modified g-C3N4 heterojunction were prepared by a one-step heating strategy.•The heterojunction can greatly enhance visible-light hydrogen evolution activity.•The 7.5%TO/CN exhibited best photoactivity and high photochemical stability.•The heterojunction can use as a promising candidate in solar energy conversion.The photocatalytic water splitting for generation of clean hydrogen energy has received increasingly attention in the field of photocatalysis. In this study, the Ta2O5/g-C3N4 heterojunctions were successfully fabricated via a simple one-step heating strategy. The photocatalytic activity of as-prepared photocatalysts were evaluated by water splitting for hydrogen evolution under visible-light irradiation (λ > 420 nm). Compared to the pristine g-C3N4, the obtained heterojunctions exhibited remarkably improved hydrogen production performance. It was found that the 7.5%TO/CN heterojunction presented the best photocatalytic hydrogen evolution efficiency, which was about 4.2 times higher than that of pure g-C3N4. Moreover, the 7.5%TO/CN sample also displayed excellent photochemical stability even after 20 h photocatalytic test. By further experimental study, the enhanced photocatalytic activity is mainly attributed to the significantly improve the interfacial charge separation in the heterojunction between g-C3N4 and Ta2O5. This work provides a facile approach to design g-C3N4-based photocatalyst and develops an efficient visible-light-driven heterojunction for application in solar energy conversion.Download high-res image (170KB)Download full-size image

•ACZ samples were prepared by a hydrothermal method and deposition-precipitation technique.•ACZ samples were characterized by various characterization technologies.•ACZ samples showed outstanding photocatalytic activity for degradation of TC.The increasing environmental deterioration poses a severe threat to human health and ecosystems, and the photocatalytic degradation of environmental pollutions has gained intensive interest in recent years. In this study, we prepared a novel ternary Ag3PO4/g-C3N4/Znln2S4 (ACZ) photocatalyst by a hydrothermal method and deposition-precipitation technique. The ACZ composites exhibited much higher photocatalytic activities for the degradation of tetracycline (TC) than the sum of g-C3N4, Znln2S4, Ag3PO4/g-C3N4, Ag3PO4/Znln2S4 or g-C3N4/Znln2S4 under visible light irradiation (λ > 420 nm) in the photocatalytic tests. Especially, when the content of Ag3PO4 reached 3 wt% (ACZ-3), the ACZ-3 displayed the highest photocatalytic activity, which can degrade 83% TC (20 mg/L) within 60 min. The improvement in photocatalytic performance of the ternary photocatalyst is mainly attributed to the extended absorption in the visible light region and the effective separation of photogenerated electron-hole pairs between the Ag3PO4 and g-C3N4/Znln2S4.

•The Bi2S3/BiOBr photocatalysts were prepared by an anion exchange strategy.•The heterojunction showed excellent photoactivity for degradation of ciprofloxacin.•The nanocomposites are cost-saving, high-efficiency, and good photostability.•The Bi-based heterojunction can be used for the antibiotic pollutant purification.A nanoplate-like Bi-based heterojunction was firstly prepared through in situ formation of Bi2S3 nanocrystals on the surface of BiOBr nanoplates via a facile anion exchange strategy. The as-prepared Bi2S3/BiOBr heterojunctions were carefully characterized by multiple physicochemical techniques. The photocatalytic activity of as-synthesized samples were evaluated by the photodegradation of ciprofloxacin (CIP) under visible-light irradiation (λ > 420 nm). Compared to the pristine BiOBr, the Bi-based heterojunctions exhibited dramatically enhanced photocatalytic activity towards the CIP degradation in aqueous solution. Moreover, it is found that the 4% Bi2S3 coupled BiOBr heterojunction showed the superior photoreactivity for removal of CIP, which is about 2.8-folds higher than that of pure BiOBr. The significantly improved photoactivity was ascribed to the effective separation of photogenerated electron-hole pair’s between the Bi2S3 and BiOBr. This work highlights a simple approach to design the Bi-based nanocomposites and develops an efficient visible-light-driven heterojunction material for application in antibiotic pollutant purification.Download high-res image (159KB)Download full-size image

•The NGQDs-ZnNb2O6/g-C3N4 catalysts were prepared by hydrothermal reaction.•The photocatalytic performance was measured by H2 production from water splitting.•The optimum H2 evolution rate of 5%NGQDs-ZnNb2O6/g-C3N4 is 340.9 μmol h−1 g−1.•The enhanced catalytic activity can be attributed to the heterojunction and NGQDs.The development of efficient visible-light-driven photocatalysts for water splitting has drawn much attention. Herein, we demonstrated a novel H2-producing photocatalytic system that employed nitrogen doped graphene quantum dots (NGQDs)-ZnNb2O6/g-C3N4 heterostructures as the hydrogen evolving catalysts. The as-prepared NGQDs-ZnNb2O6/g-C3N4 heterostructures were favorable for light harvesting and charge separation, and showed highly efficient photocatalytic performance for water splitting into hydrogen. Results showed that both the ZnNb2O6/g-C3N4 (Zn/CN) mole ratio and the amount of NGQDs displayed important influence for H2 production. Moreover, the optimum synthesis conditions of the Zn/CN mole ratio (1/7) and the amount of NGQDs (5%) were both obtained, and the corresponding 5%NGQDs-Zn/7CN sample performed a much higher hydrogen-evolution rate of 340.9 μmol h−1 g−1. By the further studies, the enhanced photocatalytic activity could be ascribed to the crucial roles of NGQDs and heterojunction photocatalytic system, which resulted in an efficient charge separation and the largely enhanced photocatalytic activity. Meanwhile, the possible photocatalytic mechanism of NGQDs-ZnNb2O6/g-C3N4 was also proposed. We envision that this work creates new opportunities for constructing and designing efficient visible-light-driven photocatalysts for hydrogen evolution reaction.Download high-res image (343KB)Download full-size image

•A new plasmonic Ag/AgCl/Ag2O heterostructures was synthesized via a facile in-situ growth strategy for the first time.•The optimum photocatalytic efficiency of 50% Ag/AgCl/Ag2O heterostructures for the degradation of CIP was about 2.9 and 3.73 times higher than that of individual Ag2O and Ag/AgCl, respectively.•The photocatalytic mechanism was elucidated in this paper, and a possible plasmonic Z-scheme mechanism was proposed.Ciprofloxacin (CIP) has caused serious environmental problems because of its high resistance to conventional wastewater treatments methods. To improve the photodegradation efficiency for CIP, a new system of Ag/AgCl/Ag2O is developed by growth of Ag/AgCl on the surface of Ag2O nonoparticles at room temperature. The stable Ag/AgCl nanoshells could efficiently protect inner Ag2O from photocorrosion during the photocatalytic process and enhance the separation and transfer efficiency of photo-induced electron–hole pairs. The optimum photocatalytic efficiency of 50% Ag/AgCl/Ag2O heterostructures for the degradation of CIP under visible light irradiation (λ > 420 nm) was about 2.9 and 3.73 times higher than that of individual Ag2O and Ag/AgCl, respectively. The radical trap experiments showed that the degradation of CIP was driven mainly by the participation of superoxide radical (O2−) and the action of holes (h+). From the experimental results and the relative band gap position of these semiconductors, a possible Z-scheme photocatalytic mechanism was proposed. The system has greatly overcome the drawbacks of single component Ag2O and realized the strong redox ability and long-term stability.Download high-res image (86KB)Download full-size image

•Series of environment-friendly Ag:Zn-In-S QDs with widely tunable bandgap.•A volcano-type variation of photocatalytic H2 production rate with increase of Ag.•Synergistic bandgap narrowing and carrier lifetime elongation by suitable Ag-doping.Visible-light-driven photocatalytic hydrogen production has been an ongoing hot topic for clean and renewable energy, for which I–III–VI multinary metal sulfides play an important role owning to their unique ability of bandgap manipulation by composition. In this work, we present the controlled synthesis and hydrogen evolution property of a series of Ag:Zn-In-S quantum dots (QDs) in an effort to a more comprehensive understanding of Ag doping. With increasing ratio of Ag, the UV–vis absorption and photoluminescence wavelength was observed to be tuned in a wide range from light green to dark red. With increased Ag doping, dramatic increase (over 70 times) of the photocatalytic activity was observed (maximized with Ag:In:Zn ratio of 1.5:10:5). More importantly, time-resolved photoluminescence study reveals that this synergistic enhancement effect of the photocatalytic activity by controllable Ag doping was correlated with the simultaneous bandgap narrowing and carrier lifetime elongation, which contribute to the enhanced visible light absorption and charge separation, repectively. The enhanced charge separation upon Ag doping were further proved by photocurrent and electrochemical impedance spectra measurements. A mechanism is proposed for this synergistic effect of photocatalysis by suitable Ag doping, where the long-lived deep donor-acceptor pair states play an important role. Our results provide an interesting view and useful guideline for photocatalyst design using the narrow bandgap multinary sulfides.Download high-res image (278KB)Download full-size image

•The RGO-Cu2O/Bi2O3 composite was developed by solvent thermal method.•RGO-Cu2O/Bi2O3 exhibited enhanced photocatalytic performance for TC than RGO-Cu2O and RGO-Bi2O.•RGO played an important role in Z-scheme electron transfer.A series of RGO-Cu2O/Bi2O3 composite photocatalysts was developed by depositing Cu2O and Bi2O3 nanocrystals on the surface of RGO via an in situ precipitation method. The Cu2O and Bi2O3 nanocrystals distributed uniformly and separately on RGO, which favored the transfer of photogenerated electrons and holes towards an effective path. Compared with RGO-Cu2O and RGO-Bi2O3, the three-component RGO-Cu2O/Bi2O3 composites presented a further improvement on the photodegradation of tetracycline (TC) under visible light irradiation, which can be attributed to the construction of a Z-scheme photocatalytic system where the RGO served as a solid-state medium for the transfer of the photogenerated electrons from the conduction band of Bi2O3 to the valence band of Cu2O.

•RGO-Cu2O/Fe2O3 composites were prepared by one-step solvothermal synthesis.•RGO-Cu2O/Fe2O3 exhibited the better photocatalytic performance than RGO-Cu2O or RGO-Fe2O3.•It is the first time that TC was used as the scavenger to consume the holes during H2 production.•H2 production and tetracycline degradation were successfully concentrated in a system.The Cu2O and Fe2O3 semiconductors were employed to construct a series of composite photocatalysts by one-step solvothermal synthesis. The reduced graphene oxide (RGO) was used as a solid-state medium to efficiently transport photogenerated electrons from the conduction band of Fe2O3 to valence band of Cu2O, which played a key role in the introduction of tetracycline (TC) degradation during H2 production. The RGO-Cu2O/Fe2O3 composites exhibited the more excellent photocatalytic performance than the single Cu2O or Fe2O3 on the H2 production and TC degradation. Moreover, it is the first time that TC was used as a scavenger to consume the holes during H2 production, resulting in a higher H2 production efficiency than that using methanol (equal mass). The H2 production from TC solution with the G50-7/3 composite was about eight times higher than that in pure water and five times higher than that from methanol solution. This work successfully concentrated H2 production and TC degradation in a system and TC in wastewater showed a huge development potential in the field of sacrificial agents for H2 production.Cu2O and Fe2O3 were used to construct a Z-scheme photocatalytic system with RGO. RGO was used to transport electrons efficiently from the CB of Fe2O3 to VB of Cu2O and played a key role in the introduction of TC degradation during H2 production. This work successfully concentrated H2 production and TC degradation in a systemDownload high-res image (305KB)Download full-size image

Novel visible-light-driven Bi24O31Cl10 nanosheets were firstly prepared via a facile solvothermal method followed a thermal treatment. The physicochemical properties of as-synthesized sample was characterized by X-ray diffraction, X-rays photoelectron spectroscopy, scanning electronic microscopy, transmission electron microscopy, and UV–Vis spectroscopy. The photocatalytic activity of the photocatalyst was evaluated by degradation of tetracycline hydrochloride (TC-HCl) under visible-light irradiation. Results shown that the Bi24O31Cl10 nanosheets exhibited dramatically enhanced photocatalytic activity towards TC-HCl degradation in comparison with the traditional BiOCl and TiO2 (P25). The nanosheets also displayed excellent photochemical stability for efficient removal of TC-HCl. This work provides a simple approach to fabricate the novel Bi-based nanomaterial and will bring about potential application in treatment of antibiotic pollutant.

•We have prepared the NGQDs-BiOI/MnNb2O6 photocatalysts by hydrothermal method.•Antibiotics pollutants were chosen to explore the photocatalytic performance.•The highest TC degradation activity was 87.2% within 1 h by 5%NGQDs-Bi/Mn sample.•The enhanced activity due to the NGQDs and the p-n junction photocatalytic systems.Novel p-n junction photocatalysts nitrogen doped graphene quantum dots (NGQDs)-BiOI/MnNb2O6 have been prepared via hydrothermal method for the environmental remediation. The photocatalytic activity of as-prepared photocatalysts was evaluated by the degradation of different antibiotics such as tetracycline (TC), oxytetracyline, ciprofloxacin and doxycycline. Compared with single MnNb2O6 and BiOI, the hybrid materials (NGQDs-BiOI/MnNb2O6) could significantly enhance photocatalytic activity. Meanwhile, both the BiOI/MnNb2O6 ratio (Bi/Mn ratio) and the amount of NGQDs displayed important influence on the antibiotics degradation. In addition, the 5%NGQDs-Bi/Mn sample performed the optimum photocatalytic degradation toward TC (87.2%) within 60 min. By further studies based on the electron spin resonance (ESR) and active species trapping experiments, this enhanced photocatalytic property could be ascribed to high charge carrier mobility of NGQDs and the p-n junction photocatalytic systems, which greatly promoted efficient separation of charge carriers.Nitrogen doped graphene quantum dots-BiOI/MnNb2O6 p-n junction photocatalyst with enhanced visible light efficiency in photocatalytic degradation of antibiotics.Download high-res image (137KB)Download full-size image

Uniform nitrogen-doped C/Ni/TiO2 hollow spindles were successfully prepared with Ni nanoparticles encapsulated into the hollow N-doped TiO2/C matrix. This intriguing architecture not only exhibits favorable conductivity, but also provides a large quantity of accessible active sites for lithium ion insertion, thus contributing to superior lithium storage properties.

Free-standing two-dimensional MnO2/carbon sphere/graphene (MCG) films are rationally designed and used as efficient electrode materials for supercapacitor. Carbon sphere/graphene (CG) films are firstly constructed through a simple vacuum filtration method, then MCG electrodes are prepared by simply floating CGs on KMnO4 solution at room temperature. CG films act as the reducing agents as well as freestanding substrates. Birnessite-type MnO2 in situ grow on the surface of carbon spheres and graphene nanosheets. In the unique structure, carbon spheres spaced sandwich-like porous structures can provide plenty of paths for electrolyte-ion penetration. After decorating with high performance MnO2, MCG films can deliver a gravimetric capacitance of 319.3 F g−1 and a volumetric capacitance of 277.8 F cm−3, much higher than graphene and CG films. More importantly, the electrodes also exhibits high gravimetric and volumetric energy densities of 29.4 Wh kg−1 and 25.6 Wh L−1, respectively, as well as excellent cycling stability with 94.1% of its initial capacitance after 5000 charge-discharge cycles at a current density of 5 A g−1.

Novel visible light responsive g-C3N4/CdWO4 photocatalysts were formed by an in situ growth mechanism and employed in the degradation of a tetracycline (TC) antibiotic. The as-prepared composites were studied by several characterization techniques. Results revealed that the interface interaction between CdWO4 and g-C3N4 was recognized via CdWO4 nanorod loading on the surface of the layered g-C3N4, improving the separation and transfer of the photoexcited hole and electron pairs and restraining the recombination rate of photoinduced charge carriers. As a result, the photocatalytic activity of the g-C3N4/CdWO4 was enhanced in comparison with pure g-C3N4 and CdWO4 for TC degradation under visible light irradiation. Among the as-synthesized samples, the 80 wt% g-C3N4/CdWO4 photocatalyst showed optimal photocatalytic efficiency, which was about 4.0 and 20.0 times higher than that of bare g-C3N4 and CdWO4 under visible light irradiation, respectively. Significantly, the g-C3N4/CdWO4 composites exhibited better stability even after four successive cycles for TC degradation under visible light irradiation. Based on the active radical trapping and electron spin resonance (ESR) experiments, the possible mechanism of enhancing photocatalytic activity under visible light irradiation (λ > 420 nm) was proposed, to lead to further improvement in environmental remediation.

A novel BiOI/WO3 heterostructure was successfully synthesized using a facile ultrasonic process and used for the photocatalytic degradation of organic pollutants. The different BiOI loadings were investigated at the same time in this study. The heterostructure of BW-1.0 exhibited improved photocatalytic activity in comparison with pristine BiOI and WO3 with a 10.3- and 12.6-fold increase for Rhodamine B (RhB) degradation under visible light, respectively. The BiOI/WO3 heterostructured catalysts all exhibit the highest photocatalytic activity for degradation tetracycline (TC) under visible light. The excellent photocatalytic performance can be ascribed to the BiOI in close contact with WO3, which forms a heterojunction structure. This heterostructure composite photocatalyst results in an efficient charge separation at the interface, which is confirmed by photoelectron and photoluminescence spectroscopy. Moreover, trapping experiments indicated that h+ and ˙O2− were the main active species, with DMPO–˙O2− and DMPO–˙OH both being investigated. Moreover, the prepared sample shows good stability and recyclability, which are beneficial for its practical applications.

Cu/g-C3N4 photocatalysts have been synthesized using a facile method. The composition and morphology of the prepared samples were characterized by a variety of analytical methods. The results indicate that the Cu nanoparticles were uniformly loaded onto the surface of g-C3N4. In addition, photocatalytic activity experiments were carried out by investigating H2 production under visible light irradiation. The results reveal that the composites exhibited excellent performance for H2 evolution in the absence of a cocatalyst, which demonstrates that Cu nanoparticles could trap photogenerated electrons and act as a cocatalyst effectively. Thus, it was effective in transferring the interfacial photogenerated charge carriers and efficiently enhanced the photocatalytic activity.

Carbon quantum dot (CQDs) decorated hollow In2S3 microspheres were firstly synthesized by a facile hydrothermal method. CQDs with an average size of 5 nm were attached on the surfaces of hollow In2S3 microspheres. The photocatalytic activities of the as-prepared samples were investigated by the photocatalytic degradation of methyl orange under visible light, and the 3 wt% CQDs/In2S3 sample presented the most efficient photocatalytic activity which was almost 3 times the pure In2S3 sample. On the basis of the active species trapping experiment and ESR analysis, holes and superoxide radicals were proved to be the main active species in the photocatalytic degradation process, and a possible reaction mechanism was proposed.

•Ag QDs/g-C3N4photocatalysts were synthesized by one-stepmethod.•The catalysts showed excellent photoactivity and great stability.•The catalyst can be a good candidate for hydrogen production.•The enhanced mechanism was Fermi level equilibration and SPR effect.Ag quantum dots/g-C3N4 (Ag QDs/g-C3N4) photocatalysts were directly obtained via a novel one-step method. The photocatalysts were composed of Ag quantum dots with an average diameter of ca.5 nm, which were dispersed uniformly on the surface of g-C3N4 nanosheets. By using methanol as sacrificial reagent, the Ag QDs/g-C3N4 photocatalysts exhibited higher photoactivity for hydrogen production than the AX = 0 photocatalyst under visible-light irradiation (λ > 420 nm). Among various photocatalysts prepared, the AX = 0.5% photocatalyst showed maximum hydrogen production efficiency, which was enhanced by 4.6 times compared to AX = 0 photocatalyst. Our findings demonstrated that the coupled Ag QDs could enhance the visible light absorption and serve as g-C3N4 electron acceptor for effective charge separation, and further increased it’s photocatalytic activity.

•CQDs/g-C3N4 heterojunctions were synthesized by a facile low temperature method.•The catalysts exhibited good visible-light activity for RhB and TC-HCl degradation.•The catalysts showed excellent photocatalytic stability and recyclability.•The catalysts can be a good candidate for application in environmental purification.Novel carbon quantum dots (CQDs)/graphitic-like carbon nitride (g-C3N4) metal-free heterojunctions were firstly synthesized via a facile low temperature process. Multiple physicochemical techniques were carried out to characterize the samples. The CQDs with the average size of about 5 nm are attached to the surfaces of g-C3N4 nanosheets. The photocatalytic activity of as-prepared samples was carefully evaluated by the degradation of rhodamine B (RhB) and tetracycline hydrochloride (TC-HCl) under visible light irradiation. Photocatalysis result displayed that the CQDs/g-C3N4 heterojunctions can significantly enhance visible-light photocatalytic activity in compared to that of pristine g-C3N4. The reaction rate constant of the optimum active C0.50%/CN heterojunction for the photodegradation of RhB and TC-HCl were about 3.7-fold and 1.9-fold higher than that of bare g-C3N4, respectively. The efficiently enhanced photoactivity was attributed to the CQDs not only can improve the photogenerated electron–hole pair’s separation, but also can increase light harvesting by the up-conversion photoluminescence behavior. Moreover, the as-prepared C0.50%/CN sample also exhibited excellent photostability and recyclability for both photodegradation of RhB and TC-HCl. In addition, the possible enhanced photocatalytic mechanism was proposed and analyzed by the active species trapping experiments. This work will bring about potential for application in environmental purification and useful for designing other CQDs-based photocatalyst in energy conversion.

In our study, a new visible light-driven photocatalyst SrTiO3/Fe2O3 was first prepared via a simple two-step process using a hydrothermal process and electrospinning technique. The photocatalysts, composed of Fe2O3 nanowires (about 200 nm in diameter), were modified with SrTiO3 nanocube (about 50 nm) photocatalysts based on photoinduced interfacial charge transfer (IFCT). The as-prepared SrTiO3/Fe2O3 photocatalysts exhibit enhanced photocatalytic activity in degrading tetracycline (TC) over their corresponding single component under visible light irradiation. The efficient photocatalytic performance of the composites could be ascribed to the enhancement in visible light absorption efficiency and the efficient electron transfer from the valence band of the SrTiO3 nanoparticles to the Fe2O3 nanowires. This study shows their potential application in purifying TC pollution in environmental wastewater because of their high efficiency and stability.

In this work, a series of novel BiOI/CdWO4 p–n junction photocatalysts were successfully fabricated via a facile ultrasonic and stirring process. The photodegradation tests showed that the BiOI/CdWO4 p–n junction photocatalysts show enhanced efficiencies compared to pure BiOI and CdWO4. The best photocatalytic performance was obtained for the BC-2.0 sample, and the as prepared samples were studied by XRD, TEM, HRTEM, XPS, UV-vis DRS and photoluminescence (PL) spectroscopy. This enhancement may be predominantly attributed to the improvement of the photogenerated electron–hole separation and migration efficiency of the synergy impact between BiOI and CdWO4. The efficient separation of electron–hole pairs because of the synergy impact between BiOI and CdWO4. Radical scavenger experiments and ESR indicated that holes (h+) and superoxide radicals (˙O2−) were the main active species in the photocatalytic process.

•Fe2O3/MgFe2O4 heterostructure nanofibers were synthesized by a ficile electrospinning method.•Fe2O3/MgFe2O4 heterostructure nanofibers showed excellent photocatalytic performance.•The possible mechanism was proposed for the better photocatalytic activity.Fe2O3/MgFe2O4 nanofibers with heterostructure had been successfully synthesized by electrospinning method. The obtained samples were systematically characterized by scanning electron microscopy (SEM), X-Ray diffraction (XRD), UV–vis diffuse reflectance spectra (UV–vis DR). The novel Fe2O3/MgFe2O4 nanofibers exhibit an enhanced photocatalytic activity for degrading of tetracycline (TC) under visible light. Compared with bare Fe2O3 or MgFe2O4 samples, the prepared Fe2O3/MgFe2O4 (Fe:Mg=0.4:2.6) composited nanofibers show the best photocatalytic performance with a degradation efficiency of 48.7% after 2 h reaction time. This enhancement is attributed to the heterostructure of Fe2O3/MgFe2O4 nanofibers, which effectively repress the recombination of photogenerated electrons and holes.

A novel one-dimensional MgFe2O4/MoS2 heterostructure has been successfully designed and fabricated. The bare MgFe2O4 was obtained as uniform nanowires through electrospinning, and MoS2 thin film appeared on the surface of MgFe2O4 after further chemical vapor deposition. The structure of the MgFe2O4/MoS2 heterostructure was systematic investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectrometry (XPS), and Raman spectra. According to electrochemical impedance spectroscopy (EIS) results, the MgFe2O4/MoS2 heterostructure showed a lower charge-transfer resistance compared with bare MgFe2O4, which indicated that the MoS2 played an important role in the enhancement of electron/hole mobility. MgFe2O4/MoS2 heterostructure can efficiently degrade tetracycline (TC), since the superoxide free-radical can be produced by sample under illumination due to the active species trapping and electron spin resonance (ESR) measurement, and the optimal photoelectrochemical degradation rate of TC can be achieved up to 92% (radiation intensity: 47 mW/cm2, 2 h). Taking account of its unique semiconductor band gap structure, MgFe2O4/MoS2 can also be used as an photoelectrochemical anode for hydrogen production by water splitting, and the hydrogen production rate of MgFe2O4/MoS2 was 5.8 mmol/h·m2 (radiation intensity: 47 mW/cm2), which is about 1.7 times that of MgFe2O4.

Plasmonic heteronanostructures in semiconductor type display extraordinary photocatalytic efficiency induced by the plasmonic energy that operates in the Ag@CdSe-rGO hybrid ternary composites. The obtained plasmonic photocatalysts in nanoscale were fabricated by using a one-step hydrothermal method, during which the in situ nucleation of Ag@CdSe core–shell nanoparticles and the reduction of GO to rGO occurred simultaneously. Three different roles of Ag core and the junction of synergistic properties arising from the introduced rGO jointly enhanced the optical properties of CdSe. Localized plasmon resonance (LPR) effects of plasmonic Ag contribute to the separation of photogenerated e–/h+ pairs via the electrons and resonant energy transfer. Electrochemical investigations have further confirmed the enhanced separation of the photogenerated e–/h+ pairs. From comparative photocatalytic experiments of Ag@CdSe-rGO and Ag/CdSe-rGO, the plasmonic effect of the Ag core in the Ag@CdSe-rGO nanostructure serves to prolong the charge separation under visible light beyond common attached trimers.Keywords: CdSe; electron and resonant energy transfer; photocatalysts; plasmonic Ag; reduced graphene oxide

We synthesized g-C3N4/nano-InVO4 heterojunction-type photocatalyts by in situ growth of InVO4 nanoparticles onto the surface of g-C3N4 sheets via a hydrothermal process. The results of SEM and TEM showed that the obtained InVO4 nanoparticles 20 nm in size dispersed uniformly on the surface of g-C3N4 sheets, which revealed that g-C3N4 sheets was probably a promising support for in situ growth of nanosize materials. The achieved intimate interface promoted the charge transfer and inhibited the recombination rate of photogenerated electron–hole pairs, which significantly improved the photocatalytic activity. A possible growth process of g-C3N4/nano-InVO4 nanocomposites was proposed based on different mass fraction of g-C3N4 content. The obtained g-C3N4/nano-InVO4 nanocomposites could achieve effective separation of charge-hole pairs and stronger reducing power, which caused enhanced H2 evolution from water-splitting compared with bare g-C3N4 sheets and g-C3N4/micro-InVO4 composites, respectively. As a result, the g-C3N4/nano-InVO4 nanocomposite with a mass ratio of 80:20 possessed the maximum photocatalytic activity for hydrogen production under visible-light irradiation.Keywords: g-C3N4; H2 production from water splitting; heterojunction; interface; InVO4; nanocomposites

In this work, a Ag/Bi3.84W0.16O6.24 nanooctahedron composite photocatalyst was successfully synthesized via a green method at room temperature using silver nitrate (AgNO3) as the silver source. Furthermore, the photocatalytic degradation of TC under visible light was conducted to investigate the effect of Ag. In particular, the Ag/Bi3.84W0.16O6.24 nanooctahedron composite photocatalyst showed the highest photocatalytic activity when the content of Ag was 10% (molar ratio R = 0.1). Electron spin resonance examination confirmed that photoinduced active species (˙OH and O2˙−) were involved in the photocatalytic degradation of TC. The high-efficiency photocatalytic activity of the as-prepared Ag/Bi3.84W0.16O6.24 photocatalyst could be ascribed to the SPR absorption of silver nanoparticles as well as fast generation, separation and transportation of photogenerated carriers.

Novel mix-phase TiO2 nanosheets were successfully synthesized by a facile sol–gel method using graphene oxide (GO) as the sacrifice template for the first time. The SEM, TEM and AFM images revealed that the thickness of mix-phase TiO2 nanosheets was ca. 66 nm, and the TiO2 nanosheets were in a polycrystalline phase and made up of nanoparticles with the diameters of 15–25 nm. In addition, we observed that the proportion of rutile and anatase changed with the amount of tetrabutyltitanate (TBT). The results showed that the sample with 4 mL tetrabutyltitanate (TBT-4) exhibited the highest hydrogen production rate (339 μmol h−1) in all samples, which was 47% higher compared to the bulk sample. It was attributed mainly to the surface phase junction of anatase and rutile and the special morphology of the samples.

In this paper, well-defined 3D flower-like porous rhombohedral In2O3 (rh-In2O3) nanostructures were successfully synthesized via the hydrothermal method combined with post-thermal treatments. Interestingly, 3D flower-like c-In2O3 nanostructures could also be obtained by simply adjusting the annealing temperature according to this reaction route. The possible growth mechanism of the obtained flower-like In2O3 nanostructures was proposed based on a series of contrasting experimental observations depending on the different reaction conditions as well as our understanding. What's more, we also investigated the photocatalytic activities of bulk In2O3, 3D flower-like rh-In2O3, and c-In2O3 nanostructures for the degradation of tetracycline (TC) under visible light. Photocatalytic degradation results indicated that 3D flower-like porous rh-In2O3 nanostructures exhibited the highest photocatalytic activities. The possible photocatalytic mechanism for the degradation of TC in 3D flower-like porous rh-In2O3 nanostructures was also discussed.

The increasing need for efficient materials capable of solar fuel generation is primary to the development of a green energy economy. In this contribution, we demonstrate that La–Cr co-doped SrTiO3 (STO) nano-particles obtained through a one-pot microwave-assisted method exhibit visible light absorption. We fine-tune the content from cation substitution in the structure of the STO to develop high-efficiency visible-light-driven water splitting photocatalysts considering the discrete impurity levels created by dopants. In our study, we draw the conclusion from the experiments that the photocatalytic hydrogen production performance was optimum when the doping molar amount of La–Cr was 5%. Rational explanations for the high-performance of the photocatalysts of La–Cr co-doped STO materials are described.

Highly efficient visible-light-driven Ag3PO4/WO3 photocatalysts with different mole fractions of Ag3PO4 nanocrystals have been synthesized via an in situ precipitation method. Characterization results showed the in situ growth of finely distributed Ag3PO4 nanocrystals on the surface of the WO3 nanosheets. Under visible light irradiation, the Ag3PO4/WO3 photocatalysts exhibited enhanced photocatalytic activity compared with bare Ag3PO4 or WO3 for the degradation of methyl blue, and the highest activity was reached by the Ag3PO4/WO3 hybrid photocatalyst with 20 at% of Ag3PO4. The observed improvement in photocatalytic activity is associated with the extended absorption in the visible light region resulting from the attached Ag3PO4 nanocrystals, and the effective separation of photo-induced carriers at the Ag3PO4/WO3 interfaces. In addition, on the basis of the quenching effects of different scavengers and estimated energy band positions, the mechanism of enhanced photocatalytic activity is proposed.

The removal of tetracyclines (TC), the extensively used antibiotics, from the environment has become an important issue. Recently, photocatalytic oxidation on the surface of semiconductors has been found to provide a good tool for the degradation of TC; however, most of these reactions are UV-light driven rather than visible-light driven. Here, Cr doping of SrTiO3 results in a large decrease in the band gap energy, making Cr3+ doped SrTiO3 (Cr-STO) an attractive material for use as a visible-light-driven photocatalyst for tetracycline (TC) degradation. The photoactivity is improved when the Cr/Sr weight ratio changes from 0.5% to 2%, and decreases when the Cr/Sr weight ratio changes from 3% to 10%. In this paper, we also explain the relationship between the doping and the photocatalytic activity. The existence of ˙OH radicals and holes was studied by the electron spin resonance (ESR) spin-trap technique and trapping experiments.

In our study, a new visible-light-driven photocatalyst Cu2O/SrTiO3 (C/S) heterojunction was firstly prepared by a simple, facile and effective deposition–precipitation technique. The particle size of the Cu2O nanoparticle is only about 5 nm and the SrTiO3 (STO) nanocube is about 50 nm when modified by Cu2O nanoparticles. The samples are used as photocatalysts for photodegrading tetracycline (TC) under visible light irradiation. The 9-Cu2O/SrTiO3 (9-C/S) sample heterojunction shows the highest TC degradation ratio (77.65%), which is caused by the photogenerated electrons of the Cu2O nanoparticles moving from the conduction band of Cu2O to that of SrTiO3, resulting in the separation of electrons and holes. This study not only shows a possibility for substituting noble metals with low-cost Cu2O nanoparticles in photocatalytic degradation but also exhibits a facile deposition–precipitation technique for synthesizing narrow/wide band gap photocatalysts.

The photocatalytic activity of Cu2O/NaNbO3 (CNO) heterostructures for the first time is reported in this work. Pure NaNbO3 photocatalyst was synthesized via a facile hydrothermal reaction using Nb2O5 and NaOH as the precursors. A series of Cu2O nanoparticle-modified NaNbO3 was prepared via the chemical reduction of a Cu salt. The composition and morphology of the prepared CNO samples were characterized using variety of analytical methods. The results showed that the Cu2O nanoparticles were well distributed over the surface of the cube NaNbO3 microstructure. The photocatalytic performance of the prepared samples was evaluated by the degradation of methyl orange (MO) under visible light irradiation. The effects of MO degradation showed that the Cu2O nanoparticles could act as a sensitizer for improving the visible light absorption of NaNbO3 cubes. We proposed a heterostructure between Cu2O and NaNbO3, by which the recombination of electrons and holes is efficiently inhibited and the photocatalytic activity is enhanced.

•BiYO3 was prepared by a combination of the hydrothermal method and annealing treatment.•The as-prepared BiYO3 was predominantly rod in shape.•BiYO3 nanorods displayed visible-light photocatalytic activity towards TC degradation.•Possible mechanism for the tetracycline degradation over BiYO3 was discussed in detail.BiYO3 nanorods were successfully synthesized via the hydrothermal method combined with annealing treatment for the first time. The structure, morphology and optical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy spectra (FT-IR), and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The results show that the as-prepared BiYO3 exhibits the rod-like morphology and also exhibits visible absorbing ability with the band gap of 2.36 eV. Finally, the photocatalytic activity and mechanism of BiYO3 toward the degradation of tetracycline (TC) under visible light are discussed in detail.

Tantalate semiconductor nanocrystals have been at the forefront of the photocatalytic conversion of solar energy to supply hydrogen owing to their favorable and tunable optical and electronic properties as well as advances in their synthesis. However, a narrow band gap is required for response to improve the efficiency of the photocatalysts. Here we propose an efficient enhancement of the H2 generation under simulated sunlight and visible light irradiation by a dispersion of Ag-decorated KTaO3 and NaTaO3 nanocubes. X-ray diffraction and UV–vis diffuse reflectance spectra are used to characterize the products. Transmission electron microscope (TEM) and high-resolution high-angle annular dark-field scanning TEM (HAADF-STEM) images show that the Ag nanoparticles (NPs) are uniformly loaded on the surfaces of KTaO3 and NaTaO3. The photocatalytic water-splitting results over Ag-decorated KTaO3 and NaTaO3 show that the rate for H2 evolution from aqueous CH3OH solutions is up to 185.60 and 3.54 μmol/h·g under simulated sunlight and the rate for H2 evolution is more than 2 times than that of pure NaTaO3 and KTaO3 materials. However, under purely visible light illumination the highest H2 evolution of 25.94 and 0.83 μmol/h·g is observed in the case of Ag-decorated KTaO3 and NaTaO3 nanocubes. To the best of our knowledge, this is the first time that the photocatalytic water-splitting activity of the prepared Ag-decorated KTaO3 and NaTaO3 nanocubes has been reported.

•A facile one-step solvothermal approach to synthesize BiPO4–RGO nanocomposites.•The BiPO4–RGO nanocomposites exhibited enhanced photocatalytic activity.•Reasons for the enhanced photocatalytic activity were discussed.•Good interaction between BiPO4 and graphene for effective charge pairs separation.A facile one-step solvothermal approach was developed to synthesize BiPO4–graphene (BP–RGO) nanocomposites using ethylene glycol/water as the solvent and reducing agent. During the solvothermal reaction, both the effective reduction of graphene oxide (GO) and the growth of rod-shaped BiPO4 as well as its deposition on graphene occurred simultaneously. The as-obtained BP–2%RGO nanocomposite showed the highest photocatalytic activity toward the photodegradation of methyl orange (MO), which was about 2.0 and 1.5 times as high as that of pure BiPO4 and physical mixture of BiPO4 and graphene, respectively. The enhanced photocatalytic activity of BP–2%RGO nanocomposite is attributed to a larger surface area, much increased adsorption capacity, and more effective charge transportations and separations arisen from the introduction of graphene along with the intimate interfacial contact between BiPO4 and graphene. This work highlights the significant effect of solvothermal method and introduction of graphene on the photoactivity of graphene-based nanocomposites. It is expected that this method could aid to fabricate more efficient graphene-based photocatalysts with improved interfacial contact and photocatalytic performance for environmental remediation.Graphical abstract

A novel and efficient photocatalyst comprising 3D (three dimensional) flower-like MnNb2O6 nanostructures was synthesized via an inorganic salt-assisted hydrothermal method. The morphology and structure of the nanostructures consisted of elegant flower-like nanostructures which were composed of nanosheets. K2SO4 played a crucial role in the formation of the nanostructures and the crystal growth process was proposed based on Ostwald ripening. The photocatalytic mechanism and photocatalytic activity of the 3D MnNb2O6 flower-like nanostructures were investigated for the photocatalytic degradation of organic methylene blue (MB) under visible light irradiation. The 3D MnNb2O6 flower-like nanostructures exhibited the highest degradation ratio for MB among different structures of MnNb2O6.

In this paper, Fe-doped SrTiO3 (FSTO) photocatalysts were successfully prepared via a facile solvothermal method, and their photocatalytic activities for degrading tetracycline (TC) under visible light irradiation were examined. It was found that doping Fe3+ into the lattice of SrTiO3 resulted in the formation of new absorption bands in the visible light region, and the energy band gap decreased from 3.2 eV to 2.6 eV with Fe3+ doping amounts of 0 to 5 wt%. The photocatalytic experimental results indicated that the as-prepared FSTO photocatalysts generate an extremely high enhancement in the TC degradation ratio compared to the pure SrTiO3 under visible light irradiation. In particular, the FSTO sample doped with 3% Fe exhibited the highest TC degradation ratio (71.6%) in 80 min, which is mainly attributed to the narrowed gap generated by the appropriate level of Fe3+ doping. This work suggests that this doping method should be applicable for exploiting other efficient visible light-driven photocatalysts with wide band gap semiconductors.

•Well-dispersed t-Se microspheres are prepared via a green and low-cost hydrothermal route.•The possible growth mechanism of the as-synthesized t-Se microspheres was proposed in this letter.•PL spectrum indicates that the as-obtained t-Se microspheres with an average diameter of 1 µm show a strong red-emitting peak at 675 nm.A green and economical hydrothermal route was developed to synthesize uniform trigonal selenium (t-Se) microspheres with an average diameter of 1 µm by using ascorbic acid (Vc) as a mild reducing agent and Se powder as the selenium source. The as-prepared products were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Experimental results reveal that the morphology of t-Se microspheres is strongly dependent on the reaction conditions such as the amount of Vc, reaction temperature and reaction time. The tentative growth mechanism of t-Se microspheres is also discussed in this letter. Photoluminescence spectrum indicates that the t-Se microspheres with an average diameter of 1 µm exhibit a strong red-emitting peak at 675 nm.

•Ni2+ doped InVO4 nanocrystals were prepared by a one-pot microwave-assisted method.•The band gap energy of samples can be precisely controlled.•Doped samples show higher O2 production rate under visible-light.In this letter, Ni2+ doped InVO4 nanocrystals were successfully synthesized by a simple one-pot microwave-assisted method. The energy bandgap of obtained samples can be precisely controlled by varying the Ni2+ doping amount. The O2 production rate of obtained Ni–InVO4 nanocrystals is higher than that of pure InVO4 nanocrystals under visible-light, which can be ascribed to the narrowed band gaps. The corresponding 1% doped sample N1 has the highest O2 production rate (394 μmol/h) in all samples, which is 66% higher than the undoped sample N0.

The construction of heterojunction photocatalysts has received much attention in the field of photocatalytic H2 production from water splitting. The surface phase junction of semiconductors is very important to the activity of heterojunction photocatalysts. In this study, an effective anatase–graphene–rutile heterojunction structure was designed and fabricated by using graphene as the surface phase junction between anatase and rutile particles. Results show that both the anatase/rutile ratio (A/R ratio) and graphene amount represent important influence on H2 production activities of anatase–graphene–rutile heterojunction photocatalysts. Under our experimental condition, the optimum A/R ratio is 7/3 and graphene addition amount is 2 wt %, the corresponding AR7/3–2%G sample has the highest H2 production rate of 1.714 mmol/h. By further experimental study, we think the high H2 production activity of anatase–graphene–rutile heterojunction photocatalyst is from the enhanced charge separation rather than other effect. This work values the expanding of surface phase junction and provides a feasible strategy to develop high-performance photocatalysts by designing and expanding the surface phase junction.

Sb2Te3–Te barbell-like heterogeneous nanostructures (HNs) composed of single-crystalline Sb2Te3 nanoplates and Te nanorods have been fabricated via a facile hydrothermal approach. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning TEM (STEM). The barbell-like heterogeneous nanostructures can be synthesized by properly tuning the reaction time, temperature and the molar ratio of the reactants. Based on a series of contrast experiments, the probable epitaxial growth process that Sb2Te3 nanoplates grow perpendicular to the axis of the central of the Te nanorods is proposed. The obtained Sb2Te3–Te heterogeneous nanostructures have a room-temperature electrical conductivity and Seebeck coefficient of 150.2 S cm−1 and 148.1 μV K−1, respectively, and a maximum power factor of 1.02 mW K−2 m−1 can be obtained at 550 K.

A new inorganic–organic hybrid In2Se3(en) was synthesized as hollow nanospheres via a facile and controllable hydrothermal method in a system containing ethylenediamine (en) and hydrazine hydrate. These as-obtained hybrid hollow nanospheres with an average diameter of 200 nm were assembled by irregularly small-sized (ca. 20 nm) nanoparticles. These hollow nanospheres were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The surface chemical composition of the In2Se3(en) hollow nanospheres were studied by X-ray photoelectron spectroscopy (XPS). The possible gas bubble-template growth mechanism is proposed to understand the formation of In2Se3(en) hollow nanospheres. Room-temperature UV-vis diffuse reflection spectra and photoluminescence (PL) spectra indicate that the as-obtained hybrid nanospheres possess a maximum absorption at 470 nm and single strong near-infrared emission peak centered at 1092 nm. The near-infrared luminescence endows the hybrid nanospheres with potential application in telecommunications, biolabeling and biomedical imaging, etc.

•Porous NiSe hollow nanospheres are prepared by a hydrothermal route.•The possible growth mechanism of NiSe sample is proposed.•The obtained NiSe simple has excellent hydrogen storage capacities.•Our study is significant and works as the blocks for the study of NiSe.We have successfully fabricated the uniform porous hollow NiSe nanospheres composed of nanoparticles via a mild hydrothermal method. The growth mechanism of these hollow nanospheres was proposed based on a series of contrast experimental observations depending on different reaction conditions (including time, temperature, reactant ratio and the amount of ammonia water) as well as our understandings. We also investigated the Raman stretching modes of NiSe hollow nanospheres. Meanwhile, we have also studied the properties of magnetism and electrochemical hydrogen storage of the NiSe nanospheres. The method in our report might provide alternative synthetic approach for other metal selenides with hollow structures in the future.

Recently, the controlled synthesis of semiconductor photocatalysts has attracted intense attention. In this report, we first report the controlled synthesis of Bi2WO6 nanostructures via the soluble inorganic salt Na2SO4-assisted hydrothermal method by simply adjusting the reaction time and pH value. Four typical Bi2WO6 nanostructures were obtained, namely nestlike nanostructures assembled by nanoplates (NNS-ANPs), rodlike nanostructures assembled by nanoplates (RNS-ANPs), quantum dots-modified nanoplates (QDs-NPs), and smooth-surfaced nanoplates (SSNPs). Tentative formation mechanisms of the different morphologies based on our observations are discussed. Photocatalytic degradation results show that the degradation ratios (DRs) of three-dimensional structures are higher than those of two-dimensional structures, and surface QDs play key roles in enhancing the DR of QDs-NPs. Morphology-dependent photocatalytic activities of different Bi2WO6 nanostructures are possibly due to different charge-separation abilities, which has been demonstrated by photoluminescence analyses.

Effective solar energy harvesting and charge carrier separation are two key factors of the photocatalysis system. In this work, the heterojunction photocatalyst of CdS/CoWO4 was fabricated by a facile hydrothermal method. Compared with the pristine CdS and CoWO4, the CdS/CoWO4 heterojunction photocatalyst showed enhanced photocatalytic activity for the methylene blue (MB) degradation under visible light irradiation. Particularly, the sample with molar ratio of CdS:CoWO4 (sample C2) controlled at 3:5 showed the highest MB degradation ratio (83%) in 1 h among all samples, which is about 3 times over the pure CdS and 8 times over pure CoWO4, respectively. The greatly enhanced photocatalytic activity (3–8 times) of CdS/CoWO4 is due to the efficient separation of electron-hole pairs by the heterojunction structure and strong visible light absorption of CdS. This work provides a new insight into the application of tungstate-based heterojunction photocatalysts in environmental remediation.

•Ni@SiO2 catalysts were synthesized by microemulsion method.•Ni@SiO2 catalysts displayed more stable performance for CO2 reforming than Ni/SiO2.•Ni sintering was not occurred due to the core-shell structure of the Ni@SiO2 catalysts.•Carbon deposits were minimized in the Ni@SiO2 catalysts.Ni@SiO2 catalysts with core-shell structure were successfully synthesized by water-in-oil (w/o) micromulsion method. The Ni nanoparticles with diameters around 5 nm were obtained after hydrogen reduction at 750 °C. The core-shell Ni@SiO2 catalysts exhibited higher catalytic performance and stability for CO2 reforming with methane reaction than the conventional supported Ni/SiO2 catalysts, which were attributed to the confinement effect of the core-shell structure in limiting the sintering of Ni nanoparticles, the stronger metal-support interaction in stabilizing the catalyst structure and the small Ni nanoparticles in minimizing the carbon deposition on the Ni@SiO2 catalysts.Download high-res image (189KB)Download full-size image

This paper presents for the first time a novel method of depositing plasmonic Bi nanoparticles on BiOCl nanosheets (Bi/BiOCl) via insitu photoelectroreduction, and Bi/BiOCl as the photocathode enabled solar water splitting in a TiO2–Bi/BiOCl photoelectrochemical (PEC) system. It is one of the challenges to understand the relationship between the PEC performance and the composite ratio of Bi/BiOCl, and the density functional theory calculation results show that charges obviously transfer from the Bi cluster to the BiOCl (001) surface. The structure of Bi/BiOCl photocathode has been successfully optimized, according to the current–potential curves and charge injection efficiency. The highly enhanced PEC activity could be attributed to the dual roles of Bi nanoparticles in enhancing the charge transfer and surface plasmon resonance (SPR) effect. More importantly, the optimal Bi/BiOCl photocathode achieved a solar hydrogen evolution rate of 2.4 µmol h−1 under full spectrum illumination (100 mW cm−2).

Spatial separation of photogenerated electron-hole pairs is one of the most important factors that determine the efficiency of a photocatalyst. It is well acknowledged that the fabrication of heterogeneous photocatalysts with two different inorganic semiconductors is a good strategy to effectively improve the charge separation of electrons and holes. This study describes a novel visible light-induced g-C3N4/Bi3TaO7 composite photocatalyst with superior photocatalytic properties toward the degradation of tetracycline (TC) by visible light irradiation. The formation of heterojunctions significantly improves the separation efficiency of photogenerated carriers, which is confirmed by the photocurrent density and electrochemical impedance spectroscopy. Electron spin resonance examination and trapping experiments confirm that the photoinduced active species (˙OH and ˙O2−) are responsible for the degradation of tetracycline. Based on the experimental results, a possible Z-scheme system reaction mechanism for the g-C3N4/Bi3TaO7 composite towards the degradation of TC under visible light was proposed.

Uniform nitrogen-doped C/Ni/TiO2 hollow spindles were successfully prepared with Ni nanoparticles encapsulated into the hollow N-doped TiO2/C matrix. This intriguing architecture not only exhibits favorable conductivity, but also provides a large quantity of accessible active sites for lithium ion insertion, thus contributing to superior lithium storage properties.

A new inorganic–organic hybrid In2Se3(en) was synthesized as hollow nanospheres via a facile and controllable hydrothermal method in a system containing ethylenediamine (en) and hydrazine hydrate. These as-obtained hybrid hollow nanospheres with an average diameter of 200 nm were assembled by irregularly small-sized (ca. 20 nm) nanoparticles. These hollow nanospheres were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The surface chemical composition of the In2Se3(en) hollow nanospheres were studied by X-ray photoelectron spectroscopy (XPS). The possible gas bubble-template growth mechanism is proposed to understand the formation of In2Se3(en) hollow nanospheres. Room-temperature UV-vis diffuse reflection spectra and photoluminescence (PL) spectra indicate that the as-obtained hybrid nanospheres possess a maximum absorption at 470 nm and single strong near-infrared emission peak centered at 1092 nm. The near-infrared luminescence endows the hybrid nanospheres with potential application in telecommunications, biolabeling and biomedical imaging, etc.