A novel photocatalyst CdWO4 was synthesized via a hydrothermal process, and its high photocatalytic activity was revealed. The influence of preparation conditions on crystal structure, optical properties, and photocatalytic activity of CdWO4 catalyst was investigated. The results showed that the sample was irregular short rods with a monoclinic wolframite structure. In photocatalytic performance, CdWO4 showed a good ability toward the photodegradation of methyl orange (MO) and Rhodamine B (RhB). The specimen prepared at pH = 4 through annealing process had the best activity in photodegradation of MO in aqueous solution under UV light irradiation. But there were no obvious differences in activity performance when annealing temperature was below 873 K, indicating that the temperature had little influence on photocatalytic activity of CdWO4.

ZnIn2S4 microspheres were successfully synthesized by a hydrothermal method. A series of synthesis temperatures from 80 to 200 °C was investigated. The samples were characterized by X-ray diffraction, UV−vis spectroscopy, nitrogen sorption analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy (SEM). The results indicated that the crystalloid structure and optical property of temperature series products were almost the same. The specific surface area (SBET) of ZnIn2S4 products declined with increasing synthesis temperature. The 80 °C sample had the largest SBET (85.53 m2 g−1). SEM images demonstrated that the morphology of ZnIn2S4 was marigold-like microspheres, and the 80 °C sample had a well-proportioned morphology. Several dyes (methyl orange, congo red, and rhodamine B) were applied in the ZnIn2S4 photocatalytic reactivity investigation. It showed efficient visible light photocatalytic degradation of dyes. A liquid chromatogram−mass spectrometer was used for identification of dyes and their degradation products. A large number of ·OH radicals, investigated by the method of photoluminescence with terephthalic acid, were generated in the photocatalyst system. The results indicated that the ·OH radicals played an important role in the superior visible photocatalytic activity of the ZnIn2S4 system. The mechanism related to the photocatalytic degradation was proposed and discussed.

ZnxCd1−xS nanorods were successfully synthesized by microwave method. Characterized by transmission electron microscopy, ZnxCd1−xS samples were composed of a large quantity of homogeneous rods with diameter about 10 nm. The photocatalytic degradation of methyl orange (MO) in the aqueous phase under visible light irradiation (420 nm < λ < 800 nm) was taken as a model reaction. The conversion of MO degradation using Zn0.28Cd0.72S as the photocatalyst was up to 96% after 6 h of irradiation. The separation and identification of degradation products were measured by liquid chromatography mass spectroscopy (LC-MS). After 6 h of irradiation, the intensity of the main absorption peak of MO (m/z = 304) descended in mass spectrum view, while some new peaks of degradation products showed up. From these results of LC-MS analysis, it can be concluded that it was really a photocatalytic degradation process.

•Amorphous MoSx cocatalyst was loaded on CdS NRs by a simple photodeposition.•MoSx/CdS NRs exhibited 6 times higher hydrogen evolution efficiency than Pt/CdS NRs.•The hydrogen evolution of MoSx/CdS NRs linearly increased with prolonging time.•Lower overpotential and efficient electron transfer were observed over MoSx/CdS NRs.Loading cocatalyst on semiconductors was crucially necessary for improving the photocatalytic hydrogen evolution. Amorphous MoSx as a novel and noble metal-free cocatalyst was loaded on CdS nanorods by a simple photodeposition method. Efficient hydrogen evolution with amount of 15 mmol h−1 g−1 was observed over the MoSx modified CdS nanorods, which was about 6 times higher than that by using Pt as cocatalyst. Meanwhile, with MoSx cocatalyst, the efficiency of CdS nanorods was superior to that of CdS nanoparticles and bulk CdS. No deactivation could be observed in the efficiency of MoSx modified CdS nanorods under irradiation for successive 10 h. Further experimental results indicated that the efficient electrons transfer, low overpotential of hydrogen evolution and active S atoms over the MoSx modified CdS nanorods were responsible for the higher efficiency. Our results provided guidance for synthesizing noble metal-free materials as cocatalyst for photocatalytic hydrogen evolution.Photodeposition of amorphous MoSx on CdS nanorods for highly efficient photocatalytic hydrogen evolution.

In the photocatalytic oxidation of benzene over BiVO4/TiO2, some deactivation was observed at 30 °C, while stable activity was maintained at higher temperatures. To further take advantage of the heating effect during photocatalysis, Pt was loaded onto the BiVO4/TiO2 sample, owing to its excellent performance in thermocatalysis. The results show that the Pt/BiVO4/TiO2 sample with a Pt loading amount of 1.0 wt% has the best activity in the oxidation of benzene, compared with others containing loading amounts of 0.2, 0.5 and 2.0 wt%. Benzene can be totally oxidized at 80 °C with an obvious photothermocatalytic synergetic effect, whose mechanism is discussed and summarized as three main paths. In this case, the heating effect of infrared light from a light source can be helpful in photocatalysis, which is an inspiration for increasing the availability of solar energy.

The pursuit for efficient conversion of methane under ambient conditions remains a challenge, and the photocatalytic splitting of water into H2 is a hot research topic since H2 is considered to be the cleanest energy. Here, the two reactions are introduced into one photocatalytic system, which achieves the simultaneous utilization of photo-induced electrons and holes. The mechanism results demonstrate that photo-induced electrons contribute to the production of H2, while holes contribute to the conversion of CH4. This work provides a new strategy for photocatalytic reactions, and provides considerable quantum efficiencies for electrons of 2.83% (without a sacrificial agent) and holes of 2.76%. In view of the closed values of the quantum efficiencies for the two original photo-induced species, it is believed that the separated electrons and holes are more effectively utilized.

The sample H1.23Sr0.45SbO3.48 crystallized in a pyrochlore structure is applied to photocatalytic oxidation of benzene in the gaseous phase. The pyrochlore structure is considered as the key factor for the effective oxygen adsorption, which makes the sample exhibit excellent photocatalytic activity.

Intensifying the light harvesting and promoting the separation of photoinduced charge carriers are effective strategies to boost photocatalyst performance. Inspired by these insights, a hybrid photocatalyst was fabricated in this work by the deposition of Au nanoparticles (NPs) on a ZnO photonic crystal (ZnO-PC). The photonic band-gap of the ZnO-PC was tuned experimentally by Bragg's law to couple the slow photon (SP) effect of the ZnO-PC with the surface plasmon resonance (SPR) of Au NPs. Transmission spectra results indicated that, when the SP effect of the ZnO-PC matched well with the SPR of Au NPs, the visible light absorption of Au NPs could be substantially amplified. The hybrid Au/ZnO-PC showed high photocatalytic activity for the degradation of RhB under visible light irradiation, and the degradation kinetic constant (1.42 h−1) is ca. 5.6-fold higher than that of the famous N doped TiO2 (TiO2−xNx, 0.22 h−1) and 24.8-fold higher than that of the commercial ZnO NPs (0.05 h−1). The synergistic effects of the SPR of Au, the SP effect of the ZnO-PC, and the heterostructures between ZnO and Au NPs account for the high photocatalytic performance, which can enhance the harvesting of visible light and promote the separation of charge carriers. A possible reaction mechanism was tentatively proposed based on the active species analysis result. The work not only provides an effective route to enhance photocatalytic efficiency, but also contributes to a better understanding of the role of PCs in the photocatalytic reaction.

Both theories and experiments show that surface hydroxyl radicals (OH) are the most important intermediate species in the photocatalytic process. As a source of OH, surface hydroxyl (OH) groups play an important role in its generation. In this paper, the OH groups were divided into surface acidic hydroxyl (OH(a)) and surface basic hydroxyl (OH(b)) groups. From the detection by a method of surface acid–base, ion-exchange reactions, the total surface density of OH groups was about 9.58 × 10−5 mol m−2. The results measured by Fourier transform infrared spectroscopy, 1H magnetic-angle spinning NMR and electron spin resonance techniques demonstrated that the role of OH(a) groups was greater than that of OH(b) groups on the generation of OH radicals. By degradation of methyl orange, rhodamine B and p-chlorophenol, the photocatalytic activities of the catalysts were directly influenced by the amount of OH groups.

A one-pot template-free hydrothermal method was developed for the fabrication of BiVO4 microspheres with tetragonal-monoclinic heterophase structures. XRD and HRTEM characterization confirmed the formation of the heterophase structure. It was found that the molar ratio of Bi/V and hydrothermal time were critical parameters in the yield of the spherical morphology and heterophase structure. Benefiting from the unique morphology and existence of the heterophase, the as-prepared BiVO4 microspheres exhibited improved efficiency for RhB degradation in comparison with pure monoclinic scheelite-type BiVO4 and tetragonal zircon-type BiVO4. EPR and TA-PL techniques proved that the photoinduced active species were involved in the photocatalytic degradation of RhB. The enhanced photocatalytic performance can be attributed to the more effective separation of photogenerated carriers generated in the heterophase BiVO4 system, as evidenced by electrochemical measurements.

Highly stable dispersions of nanosized copper (Cu) particles with an average size of (2.6 ± 0.5) nm were synthesized by in situ reduction of Cu(II) to immobilize Cu nanoparticles on the amino-enriched surface of chitosan (CTS). The synthetic process and stability of the l-ascorbic acid-stabilized Cu-CTS nanocomposites were investigated by X-ray photoelectron spectroscopy and Fourier transform Infrared spectroscopy. The antimicrobial efficiency and potency of the Cu-CTS nanocomposites were studied. The Cu-CTS nanocomposites were found to exhibit a broad antimicrobial spectrum and high antimicrobial activity against Gram-positive bacterial pathogen Staphylococcus aureus and fungal pathogen Monilia albican. The minimum inhibitory concentration of the Cu-CTS nanocomposites toward S. aureus was found to be 6.4 µg mL−1, much lower than those reported in the literature. Furthermore, the Cu-CTS nanocomposites were stable and maintained good disinfection potential even after 90-day shelf-time under ambient conditions.以抗坏血酸为稳定剂,通过原位还原络合于壳聚糖表面的铜离子,制备了平均粒径2.57 ± 0.5 nm的高稳定的纳米铜/壳聚糖复合物。利用X射线光电子谱(XPS)和傅里叶变换红外光谱(FT-IR)表征了复合物的合成过程及其稳定性, 同时采用最低抑菌浓度法(MIC)定量表征了复合物的抗菌性能。结果表明稳定结合于壳聚糖表面的纳米铜具备高效的广谱抗菌性能,特别针对革兰氏阳性菌如金色葡萄球菌以及真菌如白色念珠菌。纳米铜/壳聚糖复合物对金色葡萄球菌的MIC为6.4 µg mL−1,该数值优于已报道的其他纳米铜材料。常温常压存放90 d后,纳米铜/壳聚糖复合物仍具备稳定的结构和良好的抗菌性能。.

Photonic crystals of multiple metal oxides with highly ordered structures and unique photonic effects have presented a prospective application in designing of photocatalysts. In this study, a facile method was developed to prepare pure ZnGa2O4 photonic crystals with a highly ordered skeleton structure at a relatively low temperature (500 °C). Due to facilitated mass transport in a highly ordered channel, the as-prepared ZnGa2O4 photonic crystals exhibits better photocatalytic activity towards methyl orange degradation compared to those of porous ZnGa2O4 and ZnGa2O4 nanocrystals. By changing the pore diameters in the structure, a slow photon effect on the blue edge of photonic band gap could be observed, which consequently enhanced the electronic band absorption over ZnGa2O4 photonic crystals with a pore diameter of 180 nm, and further improved their corresponding photocatalytic activity. Furthermore, the degradation mechanism over ZnGa2O4 photonic crystals was discussed. The preparation of ZnGa2O4 photonic crystals in this study provides experimental guidance for developing ternary metal oxide photonic crystals with enhanced light absorption and photocatalytic activities.

A large-area smooth graphene film on a TiO2 nanotube array was directly fabricated using a simple, green and low-cost electrochemical process. The controllable formation mechanism of the graphene film is demonstrated in detail. The enhanced photoelectric and photocatalytic properties of the composite film imply great potential applications in various fields.

The most efficient solar energy utilization is achieved in natural photosynthesis through elaborate cell membrane with many types of molecules ingeniously transferring photogenerated electrons to reactants in a manner similar to the so-called Z-scheme mechanism. However, artificial photosynthetic systems based on semiconductor nanoparticles are inevitably accompanied by undesired non-Z-scheme electron transfer and back reactions, which adversely affect the photoactivity and photostability of the systems. Herein, we report on a novel Z-scheme system with an electrochemically converted graphene (GR) film as the electron mediator interlayer contacted with both TiO2 nanotube (TNT) array and CdS quantum dots (CdS QDs) on two sides. The obtained TiO2 nanotube array–graphene–CdS quantum dots (TNT-GR-CdS) composite film shows higher photoelectric response and photocatalytic activities than other bare TNT, TNT-CdS, TNT-GR, and TNT-CdS-GR. Moreover, compared to TNT-CdS, the activity stability is significantly improved, and the residual amount of Cd element in reaction solution is reduced ∼8 times over TNT-GR-CdS. Various measurements of photoelectrochemistry and radicals reveal that the enhanced photoactivity and photostabilities of TNT-GR-CdS are due to the efficient spatial separation of the photogenerated electron–hole pairs and the restricted photocorrosion of CdS via an efficient Z-scheme mechanism under simulated sunlight.Keywords: composite; nanotube; photocatalysis; photoelectrochemistry; Z-scheme

As the inverse-opal structure facilitates the separation of electron–hole pairs and electron transfer, it may generate many radical species with strong oxidation capability. When a low bias voltage was applied on the TiO2 electrodes with inverse-opal structure, they exhibited more excellent photoelectrochemical properties and photoelectrocatalytic activity than TiO2 film under simulated solar light irradiation. When different types of active species scavengers were added, the different performances of TiO2 photonic crystals in rhodamine B degradation showed that besides ˙OH and holes, which were the main active species in the photocatalysis, O2˙− played a vital role in the photoelectrocatalytic degradation process. Furthermore, the stronger signal of ˙OH-trapping photoluminescence and the variation in the concentration of nitroblue tetrazolium reflected that more ˙OH and O2˙− could be generated in the photoelectrocatalysis than that in the photocatalysis, and O2˙− was partially obtained from the cathode surface. At last, the roles active species played in the photoelectrocatalytic and photocatalytic processes were compared, and the possible degradation mechanisms of TiO2 photonic crystals in photoelectrocatalytic and photocatalytic systems were put forward, which could provide a good insight into the mechanism of photoelectrocatalytic degradation on TiO2 photonic crystals.

A novel CuO quantum dot (QD) sensitized In2O3 heterojunction was synthesized by a hydrothermal method and a post-calcination process. The as-prepared CuO-QD–In2O3 maintained its photocatalytic activity even under visible light irradiation at a long wavelength beyond 650 nm, which has been observed for the first time.

ZnO photonic crystals (ZnO-PCs) with large area and high quality were prepared by a facile auto-forced impregnation method. The resulting ZnO-PCs exhibited remarkable photocatalytic performance and photocorrosion inhibition compared with porous and commercial nanoparticle ZnO.

Coupling photocatalysts with photonic crystals structure is based on the unique property of photonic crystals in confining, controlling, and manipulating the incident photons. This combination enhances the light absorption in photocatalysts and thus greatly improves their photocatalytic performance. In this study, Ga2O3 photonic crystals with well-arranged skeleton structures were prepared via a dip-coating infiltration method. The positions of the electronic band absorption for Ga2O3 photonic crystals could be made to locate on the red edge, on the blue edge, and away from the edge of their photonic band gaps by changing the pore sizes of the samples, respectively. Particularly, the electronic band absorption of the Ga2O3 photonic crystal with a pore size of 135 nm was enhanced more than other samples by making it locate on the red edge of its photonic band gap, which was confirmed by the higher instantaneous photocurrent and photocatalytic activity for the degradation of various organic pollutants under ultraviolet light irradiation. Furthermore, the degradation mechanism over Ga2O3 photonic crystals was discussed. The design of Ga2O3 photonic crystals presents a prospective application of photonic crystals in photocatalysis to address light harvesting and quantum efficiency problems through manipulating photons or constructing photonic crystal structure as groundwork.

3D inverse opal ZnO photonic crystals (ZnO-PCs) with designed photonic bandgap (PBG) were prepared to study the pore size and slow photon effect on photocatalytic dye degradation. The PBGs of these ZnO-PC films were tuned experimentally by variation of the polystyrene sphere size of the opal templates. It was found that there is competition between the surface area and mass transport with increasing pore size during photocatalysis. ZnO-PCs exhibited higher photocatalytic activity under visible light irradiation, when the probe molecules were absorbed and well matched with the PBG. The enhancement could be attributed to intensified dye photosensitization as a result of the slow photon effect at the PBG edges, thus leading to a remarkable improvement in the light trapping. The present results provide useful information for developing high performance photocatalysts and photoanodes based on artificial photonic crystal design.

Photonic crystals have attracted extensive interest for the potential applications in manipulating light by nontraditional ways based on photonic band structure concepts. In this paper, 3D inverse-opal TiO2 photonic crystals (TiO2-PCs) with designed photonic band gaps are prepared. It is worth noting that when the photonic band gaps of the TiO2-PCs are matched with the absorption peaks of the dyes (methyl orange, rhodamine B, and methylene blue), the photocatalytic activity of the corresponding sample is improved under simulated solar light (320 nm < λ < 800 nm) and visible light (420 nm < λ < 800 nm) irradiation. The enhancement could be attributed to the intensified dye sensitization as a result of slow photon effect on the edges of the photonic band gaps. Furthermore, the TiO2-PCs exhibit much higher photocatalytic activity and stability than TiO2 nanoparticle film. It is believed that the presence of inverse opal structure plays an essential role in affecting the dye sensitization and photoreactivity, which could provide valuable information on the design of photocatalysts and set the foundation for the future environmental and energy technologies.

The rose-flower-like BaSb2O6 (R-BaSb2O6) and marigold-flower-like BaSb2O6 (M-BaSb2O6) have been successfully prepared by a simple hydrothermal method avoiding high temperature, templates, catalysts, surfactants, or organic solvents. Their structures and morphologies have been investigated by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and selected-area electron diffraction. Ba/Sb molar ratio and pH values in the precursor play significant roles in building two kinds of flower-like BaSb2O6. Time dependent experiments reveal the possible formation mechanisms of the BaSb2O6 microstructures. When used as a photocatalyst, the M-BaSb2O6 exhibits the best photocatalytic activity among R-BaSb2O6, M-BaSb2O6 and BaSb2O6 synthesized by solid state reaction. The morphology of M-BaSb2O6 results in the large BET specific surface area and unique light propagation mode, which greatly improve the interaction among photons, organic compounds and photocatalyst, and thus enhance photocatalytic activity. The photocatalytic stability experiments demonstrate the sufficient stability of M-BaSb2O6 during the photocatalytic process.

We report here a facile one-step strategy to prepare hollow ZnO core/ZnS shell structures by microwave irradiation. The growth mechanism of the hollow core/shell structures was investigated in detail. ZnO truncated hexagonal pyramids first form on as-grown precursor flakes and then evolve into ZnO hexagonal twin crystals, which subsequently grow up and dissolve internally. The hollowing progress is firstly controlled by the Kirkendall effect and then undergoes an Ostwald ripening process. Hollow structures and the formation of ZnO/ZnS heterostructure bring enhanced photocatalytic activities to ZnO core/ZnS shell structures. The formed ZnO/ZnS heterostructures also fill the surface defects of ZnO crystals and improve the stability of the photocatalysts by overcoming the photocorrosion effect of a single ZnO photocatalyst under UV light irradiation. Superoxide radicals (O˙−2) are the key active species in the photocatalytic system of degradation of p-chlorophenol over hollow ZnO core/ZnS shell structures. The photocatalysis process has been discussed and a possible mechanism also has been proposed. This work is helpful to controllably construct other hollow core/shell structures, develop ZnO-based photocatalysts without photocorrosion effect and further study the photocatalytic mechanism of similar systems.

The polyaniline (PANI)/TiO2 nanocomposites have been successfully synthesized via a hydrothermal method and followed by a low-temperature calcination treatment process. We find that such a PANI/TiO2 nanocomposite exhibits higher photocatalytic activity and stability than bare TiO2 and TiO2-xNx toward the liquid-phase degradation of methyl orange (MO) under both UV and visible light (420 nm < λ < 800 nm) irradiation. More noteworthy, the PANI/TiO2 photocatalyst still perform good activity toward MO and 4-chlorophenol (4-CP) under the longer wavelength of light (550 nm < λ < 800 nm). The total organic carbon (TOC) tests show that the mineralization rate of MO and 4-CP over PANI/TiO2 are apparently higher than bare TiO2 under the irradiation of both UV and visible light. The presence of synergic effect between PANI and TiO2 is believed to play an essential role in affecting the photoreactivity. At last, the roles of active species in the photocatalytic process are compared by using different types of active species scavengers. Meanwhile, the degradation mechanism of the photocatalysts is proposed. It is hoped that our work could provide valuable information on the design of polymer modified semiconductor with more excellent properties and set the foundation for the further industrial application.

Novel Ag3VO4/TiO2 nanocomposites photocatalysts with high efficiency and broad spectrum response were first prepared by a facile and low-cost coupling method. The samples performed high photocatalytic activity and stability in decomposing continuous-flow gaseous benzene with high toxicity and stability under both visible and simulated solar light irradiation. When the mass fraction of Ag3VO4 in nanocomposites was 0.5%, the sample possessed the highest photocatalytic activity among those Ag3VO4/TiO2 nanocomposites in different proportions. The conversion and mineralization rate reached about 40 and 60% respectively, which was nearly two times higher than that of nitrogen-doped TiO2 (TiO2–xNx), when it was used to degrade continuous-flow gaseous benzene photocatalytically at an inlet concentration of 280 ppm and a gas hourly space velocity of 876 h–1 under visible light irradiation for 10 h. Moreover, under simulated solar light irradiation, the benzene could be nearly completely conversed and mineralized on the sample. The photoelectrochemical measurement confirmed that the interface charge separation efficiency was improved by coupling TiO2 with Ag3VO4, which contributed to the enhancement of photocatalytic activity. A variety of merits of Ag3VO4/TiO2 nanocomposites make it possess promising application value in industry.

Active species such as holes, electrons, hydroxyl radicals (•OH), and superoxide radicals (O2•–) involved in the photodegradation process of methyl orange (MO) over TiO2 photocatalyst were detected by several techniques. Using different types of active species scavengers, the results showed that the MO oxidation was driven mainly by the participation of O2•–, holes and •OH radicals. Characterized by the liquid chromatography/mass spectrometry, the transversion of the degradation products with the light irradiation time was first analyzed. Combined with the measurement of oxidation reduction potential, dissolved oxygen, conductivity, and pH values, the degradation process of MO on TiO2 under the effect of the active species was revealed. This was the first time that electrodes were introduced to track the degradation process in situ, and these parameters would be helpful to explain the degradation processes of other organic pollutants.

In order to exploit efficient photosensitizers with appropriate electronic states to enhance the transfer of electrons, ZnxCd1-xS/TiO2 nanocomposites were first synthesized by a simple hydrothermal method. The samples were characterized by X-ray diffraction, transmission electron microscopy, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, electron spin resonance, and photoluminescence techniques. The results showed that the composite of the two inorganic semiconductors largely enhanced the photosensitized degradation of rhodamine B (RhB) under visible light irradiation (420 nm < λ < 800 nm). These photocatalytic reactions were driven mainly by the light absorption of RhB molecules and to a lesser extent by the excitation of ZnxCd1-xS. They were supposed to arise mainly from the electron transferred from the adsorbed dye in its singlet excited state to the conduction band of ZnxCd1-xS and TiO2. Such a heterogeneous photocatalytic reaction has much significance in the degradation of organic pollutants in ordinary photocatalysis.

AgIn5S8 powders were successfully synthesized by a microwave hydrothermal method for the first time. This method is a mild and highly efficient route involves no templates, catalysts, or surfactants. Therefore, it is very promising for the low-cost and large-scale industrial production. The samples were characterized by X-ray diffraction, UV–vis spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The photocatalytic activity of AgIn5S8 nanoparticles was investigated through the degradation of methyl orange under visible light irradiation. Compared with TiO2−xNx, AgIn5S8 has exhibited a superior activity under the same condition. A liquid chromatogram-mass spectrometer was used to separate and identify the dye and degradation products generated during the reaction. According to the experiment results, a possible mechanism for the degradation of organic pollutant over AgIn5S8 was proposed.Graphical abstractCompared with TiO2−xNx, AgIn5S8 has exhibited a superior activity under the same condition.

As different light-driven photocatalysts, Zn0.28Cd0.72S and TiO2 showed different properties in the photocatalytic process. In this paper, the comparison was carried out among the properties of Zn0.28Cd0.72S-visible, Zn0.28Cd0.72S-UV, and TiO2-UV light systems in the degradation of methyl orange. After the addition of different types of active species quenchers and the results detected by electron spin resonance, a photoluminescence technique, and a photometric method, it was found that, in the Zn0.28Cd0.72S-UV system, O2, •OH, and holes played a bigger role, whereas in the TiO2-UV system, •OH and holes predominated; in the Zn0.28Cd0.72S-visible light system, O2 and holes contributed to the degradation. The differences between the two catalysts lead us to realize the active species and the degradation mechanism in photocatalytic process.

A nanocrystal heterojunction LaVO4/TiO2 visible light photocatalyst has been successfully prepared by a simple coupled method. The catalyst was characterized by powder X-ray diffraction, nitrogen adsorption−desorption, transmission electron microscopy, UV−vis diffuse reflectance spectroscopy, X-ray photoelectron spectra, photoluminescence, and electrochemistry technology. The results showed that the prepared nanocomposite catalysts exhibited strong photocatalytic activity for decomposition of benzene under visible light irradiation with high photochemical stability. The enhanced photocatalytic performance of LaVO4/TiO2 may be attributed to not only the matched band potentials but also interconnected heterojunction of LaVO4 and TiO2 nanoparticles.

A nanocrystalline CaSb2O5(OH)2 photocatalyst synthesized from CaCl2 and K2H2Sb2O7 was used to degrade benzene in the gas phase for the first time. The obtained sample was characterized by X-ray diffraction, N2 sorption−desorption, UV−vis diffuse reflectance spectroscopy, transmission electron microscopy, electron spin resonance, and X-ray photoelectron spectroscopy. The CaSb2O5(OH)2 sample had an average particle size of approximately 8 nm, a specific surface area of 101.8 m2 g−1, and a band gap of 4.6 eV. Photocatalytic activity of the sample was mainly evaluated by the degradation of benzene in an O2 gas stream under ultraviolet light irradiation. The results demonstrated that the photoactivity of CaSb2O5(OH)2 was higher than that of commercial TiO2 (P25, Degussa Co.). In the photocatalytic degradation of benzene, it finally reached a steady conversion ratio of 29%. CaSb2O5(OH)2 has also exhibited activity toward other aromatic organic compounds. A possible mechanism of photocatalysis over CaSb2O5(OH)2 nanocrystals was proposed.

The nanocrystal In2S3 (nc-In2S3) has been used as a visible light active photocatalyst. The optical absorption indicated a narrow band gap (Eg =1.9 eV) for nc-In2S3. Compared with TiO2−xNx, the decomposition of methyl orange using nc-In2S3 revealed enormously enhanced visible light activity. The ·OH during the photocatalytic degradation process was detected by terephthalic acid photoluminescence probing technique (TA-PL). The organic intermediate products were successfully separated by liquid chromatogram and subsequently identified by an electrospray ionization (ESI) mass spectral technique. The possible photocatalytic mechanism is presented.

A Pb(Zr0.52Ti0.48)O3/TiO2 composite photocatalyst with nanostructured heterojunction was prepared by a simple sol−gel method. The catalyst was characterized by powder X-ray diffraction, nitrogen adsorption−desorption, transmission electron microscopy, UV−vis diffuse reflectance spectroscopy, electrochemistry technology, and spin-trapping electron paramagnetic resonance. The visible light-induced photocatalytic activities were evaluated by decomposing ethylene in gas phase. The result showed that the prepared composite catalyst exhibited efficient photocatalytic activities with high photochemical stability under visible light irradiation. Moreover, it also showed excellent photocatalytic performance under UV light or simulated sunlight irradiation. On the basis of the measurement of flatband potentials of the samples and the detection of active oxygen species (such as O2•− and OH•), a visible light-induced photocatalytic degradation mechanism of ethylene on PZT/TiO2 was proposed.

A nanocrystalline Cd2Sb2O6.8 photocatalyst was synthesized from Cd(Ac)2 and K2H2Sb2O7 via a facile hydrothermal method for the first time. The obtained sample was characterized by X-ray diffraction, N2 sorption−desorption, UV−vis diffuse reflectance spectroscopy, transmission electron microscopy, electron spin resonance, X-ray photoelectron spectroscopy, and Fourier transformation infrared spectroscopy. The photocatalytic activity of the sample was evaluated by the degradation of benzene in an O2 gas stream and dyes in aqueous solution under ultraviolet (UV) light illumination. The results demonstrated that Cd2Sb2O6.8 had exhibited a higher photocatalytic activity than that of P25 (Degussa Co.) in the degradation of benzene. For a longtime (40 h) reaction test, Cd2Sb2O6.8 maintained a high activity, and no obvious deactivation was observed. In the liquid phase, degradation of methyl orange; salicylic acid; and Rhodamine B, Cd2Sb2O6.8, also exhibited high photoactivity. A possible mechanism of the photocatalysis over Cd2Sb2O6.8 is proposed.

CaSb2O5(OH)2 nanocrystals were synthesized via a facile microwave-hydrothermal method. The physicochemical properties of the as-synthesized CaSb2O5(OH)2 photocatalyst were characterized by X-ray diffraction, UV−vis diffuse reflectance spectroscopy, transmission electron microscopy, electron spin resonance, and X-ray photoelectron spectroscopy. The photocatalytic activity was evaluated by the decomposition of rhodamine B, methyl orange, and methylene blue in aqueous solution under UV irradiation. For comparison purposes, we have also investigated the activity of TiO2 (P25, Degussa Co.) under the same condition. The results revealed that the sample had a much higher photocatalytic activity than that of P25. The high activity and long-term stability of CaSb2O5(OH)2 were mainly attributed to its stronger oxidative capability and larger specific surface area in comparison with P25. This article presents a detailed analysis of the intermediates produced in the photocatalytic reactions using the liquid chromatography−mass spectrometry technique. The possible photocatalytic reaction pathways as to how CaSb2O5(OH)2 nanocrystals degrade organic dyes have also been proposed.

Eu3+-doped CdWO4 was prepared for the first time by a hydrothermal method. The structure, morphology, and luminescence of the Eu3+-doped CdWO4 were characterized. TEM results revealed that the pure CdWO4 was a nanorod with a width of about 50 nm. The photoluminescent properties of Eu3+-doped CdWO4 complexes indicated energy transfer from WO42− groups to Eu3+ and suggested effective doping of Eu3+ into the lattice of CdWO4. The photocatalytic activity of CdWO4 and Eu3+-doped CdWO4 was investigated by the photodegradation of methyl orange (MO). Eu3+-doped CdWO4 had enhanced photocatalytic activity in the photodegradation of MO. The hydroxyl radical was detected by the terephthalic acid photoluminescence (TA-PL) method, and the regular change revealed that the hydroxyl radical may be the active species.

Porous ZnIn2S4 microspheres have been successfully synthesized by means of a facile thermal solution method at 353 K. This method was a simple route that involved low temperature, no templates, no catalysts, no surfactants, or organic solvents. Scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, nitrogen sorption analysis, and a UV−vis spectrophotometer were used to characterize the products. The results demonstrated that the microspheres, which were composed of many ZnIn2S4 single crystal nanosheets, underwent the Oswald ripening and self-assembly processes. A morphology formation mechanism has been proposed and discussed. The porous ZnIn2S4 product showed an enhancing visible-light photocatalytic activity for methyl orange degradation. The as-grown architectures may have potential applications in solar energy conversion, environmental remediation, and advanced optical/electric nanodevices.

The bifunctional photocatalyst Pt/TiO2−xNx has been successfully prepared by wet impregnation. The properties of Pt/TiO2−xNx have been investigated by diffuse reflectance spectra, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, a photoluminescence technique with terephthalic acid, and electric field induced surface photovoltage spectra. The photocatalytic activity of the sample was evaluated by the decomposition of volatile organic pollutants (VOCs) in a H2−O2 atmosphere under visible light irradiation. The results demonstrated that nitrogen-doped and platinum-modified TiO2 in a H2−O2 atmosphere could enormously increase the quantum efficiency of the photocatalytic system with excellent photocatalytic activity and high catalytic stability. The increased quantum efficiency can be explained by enhanced separation efficiency of photogenerated electron–hole pairs, higher interface electron transfer rate, and an increased number of surface hydroxyl radicals in the photocatalytic process. A mechanism was proposed to elucidate the degradation of VOCs over Pt/TiO2−xNx in a H2−O2 atmosphere under visible light irradiation.

Nanocrystal ZnxCd1−xS solid solutions were successfully and simply prepared by hydrothermal processes using stable, less toxic, inorganic salts Cd(Ac)2, Zn(Ac)2, and Na2S as the reactants. The band gap of the solid solutions can be tuned by changing constituent stoichiometries of Cd and Zn. With the increase of Cd molar fraction, the X-ray diffraction peaks of the ZnxCd1−xS nanocrystals gradually shifted to small angle. Using photocatalytic degradation of methyl orange as model reactions in the aqueous phase under visible light irradiation (λ > 420 nm), the samples prepared at the condition (Cd/Zn = 3:1, 160 °C, 16 h) possessed the best activity. The diameter of the particles was about 15 nm. Transmission electron microscopy showed the particles were spherical and homogeneous. The photocatalytic conversion was up to 96% and was obviously superior to CdS and TiO2−xNx degradation under identical conditions. Liquid chromatogram/mass spectrometery was used to test the degradation products. X-ray photoelectron spectroscopy detected the valence state of elements in the samples before and after the degradation. At the same time, their degradation of p-hydroxyazobenzene, rhodamine B, and congo red also achieved good effect.

A novel visible-light photocatalyst, Sb2S3, was synthesized with a simple method. The specimen was characterized by X-ray diffraction, transmission electron microscopy, Brunauer−Emmett−Teller (BET) surface area analysis, and UV−vis diffuse reflectance spectroscopy. The results revealed that the as-synthesized sample was orthorhombic phase and consisted of rodlike particles. It possessed a surface area of 15.1 m2·g−1, and the band gap was about 1.66 eV. The photocatalytic activity of Sb2S3 nanorods was evaluated by the decomposition of methyl orange in aqueous solution under visible-light irradiation. The results demonstrated that the photodegradation ratio of methyl orange was up to 97% after 30 min of irradiation, which was much better than that of CdS and TiO2−xNx under the same condition. Meanwhile, the possible mechanism of the photocatalytic reaction had also been studied by liquid chromatography−mass spectrometry, and the •OH had been detected also by terephthalic acid photoluminescence probing technique.

Nanocrystalline titanium dioxide (TiO2) was prepared by sol–gel method and studied at eight different thermal treatment temperatures ranging from 373 to 1073 K. The resulting material was characterized by transient surface photoconductivity, XRD, photoluminescence, liquid-phase photocatalytic activity and other characters. The photocatalytic activity of these catalysts was estimated by measuring the decomposition rate of Rhodamine B. The quantum yield of OH production during TiO2 photocatalytic process was estimated in aqueous solution using terephthalic acid as a fluorescent probe. Analysis of the photoconductive spectrum of samples has revealed the existence of carriers with two different lifetimes (τ1 and τ2), which varied with the sample thermal treatment temperature in the same peculiar fashion. Both of the photoconductive carrier lifetime τ1, τ2 of titanium dioxide and liquid-phase photocatalytic activity were top at temperature 673 K, and bottom at temperature 473 K. The resistance of the samples was also found to be maximal at thermally treatment temperature 673 K.The high photoactivity of titanium dioxide at temperature 673 K can be explained by interfacial charge-transference between anatase and rutile, which can promote the separation of electrons and holes, finally leading to long carrier lifetime and large resistance. The study of relationship between them shows carrier lifetimes may be used as a new way to measure the photoactivity of different photocatalysts.

An excellent visible-light-responsive (from 400 to 550 nm) TiO2−xNx photocatalyst was prepared by a simple wet method. Hydrazine was used as a new nitrogen resource in this paper. Self-made amorphous titanium dioxide precursor powders were dipped into hydrazine hydrate, and calcined at low temperature (110 °C) in the air. The TiO2−xNx was successfully synthesized, following by spontaneous combustion. The photocatalyst was characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), transmission electron microscope (TEM), UV–Vis diffuse reflectance spectrometer (DRS), and X-ray photoelectron spectroscopy (XPS). Analysis of XPS indicated that N atoms were incorporated into the lattice of the titania crystal during the combustion of hydrazine on the surface of TiO2. Ethylene was selected as a target pollutant under visible-light excitation to evaluate the activity of this photocatalyst. The newly prepared TiO2−xNx photocatalyst with strong photocatalytic activity and high photochemical stability under visible-light irradiation was firstly demonstrated in the experiment.The excellent visible-light-responsive (from 400 to 550 nm) TiO2−xNx photocatalyst was prepared by a simple wet method. Hydrazine was used as a new nitrogen resource in this paper. In the experiment, a strong photocatalytic activity with high photochemical stability under visible-light irradiation was demonstrated.

An unprecedented material synthesized using lead zirconate titanate (PZT) coupled with TiO2 nanoparticles shows strong photocatalytic activity for degradation of Rhodamine B with high photochemical stability under visible light irradiation.

TiO2 nanoparticles were directly coupled with porous silicon and this novel composite material shows very strong photocatalytic activity for the degradation of Rhodamine B with high photochemical stability under visible light irradiation.

In the present paper, we propose a new type of catalyst, Pt/LaVO4/TiO2 (PLVT), which combines the use of UV and visible light for photocatalysis on LaVO4/TiO2 (LVT) and the heating effect of infrared light for low-temperature thermocatalysis on Pt. Under simulated solar light, benzene as an objective pollutant can be 100% eliminated and converted into CO2 and H2O on PLVT at 70 °C with an obvious synergetic effect of photocatalysis and thermocatalysis. The photothermocatalytic activity at 70 °C is about three times the sum of the photocatalytic activity and thermocatalytic activity. The stable performance of PLVT in a 60 hour durability test also indicates its applicable potential. The roles of Pt and LVT in the synergetic effect are discussed by comparing PLVT with control samples regarding the interaction between Pt and LVT under photothermocatalytic conditions. On the basis of the above experimental results, a possible mechanism of the synergetic effect is proposed.

The pursuit for efficient conversion of methane under ambient conditions remains a challenge, and the photocatalytic splitting of water into H2 is a hot research topic since H2 is considered to be the cleanest energy. Here, the two reactions are introduced into one photocatalytic system, which achieves the simultaneous utilization of photo-induced electrons and holes. The mechanism results demonstrate that photo-induced electrons contribute to the production of H2, while holes contribute to the conversion of CH4. This work provides a new strategy for photocatalytic reactions, and provides considerable quantum efficiencies for electrons of 2.83% (without a sacrificial agent) and holes of 2.76%. In view of the closed values of the quantum efficiencies for the two original photo-induced species, it is believed that the separated electrons and holes are more effectively utilized.

In the photocatalytic oxidation of benzene over BiVO4/TiO2, some deactivation was observed at 30 °C, while stable activity was maintained at higher temperatures. To further take advantage of the heating effect during photocatalysis, Pt was loaded onto the BiVO4/TiO2 sample, owing to its excellent performance in thermocatalysis. The results show that the Pt/BiVO4/TiO2 sample with a Pt loading amount of 1.0 wt% has the best activity in the oxidation of benzene, compared with others containing loading amounts of 0.2, 0.5 and 2.0 wt%. Benzene can be totally oxidized at 80 °C with an obvious photothermocatalytic synergetic effect, whose mechanism is discussed and summarized as three main paths. In this case, the heating effect of infrared light from a light source can be helpful in photocatalysis, which is an inspiration for increasing the availability of solar energy.

A large-area smooth graphene film on a TiO2 nanotube array was directly fabricated using a simple, green and low-cost electrochemical process. The controllable formation mechanism of the graphene film is demonstrated in detail. The enhanced photoelectric and photocatalytic properties of the composite film imply great potential applications in various fields.

Photonic crystals of multiple metal oxides with highly ordered structures and unique photonic effects have presented a prospective application in designing of photocatalysts. In this study, a facile method was developed to prepare pure ZnGa2O4 photonic crystals with a highly ordered skeleton structure at a relatively low temperature (500 °C). Due to facilitated mass transport in a highly ordered channel, the as-prepared ZnGa2O4 photonic crystals exhibits better photocatalytic activity towards methyl orange degradation compared to those of porous ZnGa2O4 and ZnGa2O4 nanocrystals. By changing the pore diameters in the structure, a slow photon effect on the blue edge of photonic band gap could be observed, which consequently enhanced the electronic band absorption over ZnGa2O4 photonic crystals with a pore diameter of 180 nm, and further improved their corresponding photocatalytic activity. Furthermore, the degradation mechanism over ZnGa2O4 photonic crystals was discussed. The preparation of ZnGa2O4 photonic crystals in this study provides experimental guidance for developing ternary metal oxide photonic crystals with enhanced light absorption and photocatalytic activities.

A novel CuO quantum dot (QD) sensitized In2O3 heterojunction was synthesized by a hydrothermal method and a post-calcination process. The as-prepared CuO-QD–In2O3 maintained its photocatalytic activity even under visible light irradiation at a long wavelength beyond 650 nm, which has been observed for the first time.

As the inverse-opal structure facilitates the separation of electron–hole pairs and electron transfer, it may generate many radical species with strong oxidation capability. When a low bias voltage was applied on the TiO2 electrodes with inverse-opal structure, they exhibited more excellent photoelectrochemical properties and photoelectrocatalytic activity than TiO2 film under simulated solar light irradiation. When different types of active species scavengers were added, the different performances of TiO2 photonic crystals in rhodamine B degradation showed that besides ˙OH and holes, which were the main active species in the photocatalysis, O2˙− played a vital role in the photoelectrocatalytic degradation process. Furthermore, the stronger signal of ˙OH-trapping photoluminescence and the variation in the concentration of nitroblue tetrazolium reflected that more ˙OH and O2˙− could be generated in the photoelectrocatalysis than that in the photocatalysis, and O2˙− was partially obtained from the cathode surface. At last, the roles active species played in the photoelectrocatalytic and photocatalytic processes were compared, and the possible degradation mechanisms of TiO2 photonic crystals in photoelectrocatalytic and photocatalytic systems were put forward, which could provide a good insight into the mechanism of photoelectrocatalytic degradation on TiO2 photonic crystals.

ZnO photonic crystals (ZnO-PCs) with large area and high quality were prepared by a facile auto-forced impregnation method. The resulting ZnO-PCs exhibited remarkable photocatalytic performance and photocorrosion inhibition compared with porous and commercial nanoparticle ZnO.

Intensifying the light harvesting and promoting the separation of photoinduced charge carriers are effective strategies to boost photocatalyst performance. Inspired by these insights, a hybrid photocatalyst was fabricated in this work by the deposition of Au nanoparticles (NPs) on a ZnO photonic crystal (ZnO-PC). The photonic band-gap of the ZnO-PC was tuned experimentally by Bragg's law to couple the slow photon (SP) effect of the ZnO-PC with the surface plasmon resonance (SPR) of Au NPs. Transmission spectra results indicated that, when the SP effect of the ZnO-PC matched well with the SPR of Au NPs, the visible light absorption of Au NPs could be substantially amplified. The hybrid Au/ZnO-PC showed high photocatalytic activity for the degradation of RhB under visible light irradiation, and the degradation kinetic constant (1.42 h−1) is ca. 5.6-fold higher than that of the famous N doped TiO2 (TiO2−xNx, 0.22 h−1) and 24.8-fold higher than that of the commercial ZnO NPs (0.05 h−1). The synergistic effects of the SPR of Au, the SP effect of the ZnO-PC, and the heterostructures between ZnO and Au NPs account for the high photocatalytic performance, which can enhance the harvesting of visible light and promote the separation of charge carriers. A possible reaction mechanism was tentatively proposed based on the active species analysis result. The work not only provides an effective route to enhance photocatalytic efficiency, but also contributes to a better understanding of the role of PCs in the photocatalytic reaction.

The sample H1.23Sr0.45SbO3.48 crystallized in a pyrochlore structure is applied to photocatalytic oxidation of benzene in the gaseous phase. The pyrochlore structure is considered as the key factor for the effective oxygen adsorption, which makes the sample exhibit excellent photocatalytic activity.

Efficient light harvesting was observed over CdS photodeposited on In2O3 photonic crystals during the photocatalytic hydrogenation of 4-nitroaniline to p-phenylenediamine. The highest conversion of 4-nitroaniline and selectivity of p-phenylenediamine over the In2O3 photonic crystal supported CdS were ∼93% and ∼99%, respectively, which were better than that achieved for commercial hexagonal CdS. The existence of the photonic crystal structure was responsible for the higher efficiency of In2O3 photonic crystal supported CdS. The ordered structure facilitated the mass transport. The elaborate tuning of the photonic band gap activated the slow photon enhancement effect on the blue edge for intensifying the light harvesting efficiency of CdS. Moreover, CdS supported on In2O3 photonic crystals exhibited higher photocatalytic stability than that on the In2O3 nanocrystals. The mechanism of photocatalytic hydrogenation over In2O3 photonic crystal supported CdS was discussed. Our results provided guidance for efficiently utilizing light for photocatalysis by applying photonic crystals as support.