Composite Photocatalytic System Research Articles

Preparation, characterization and photocatalytic studies of defect pyrochlore, KMn0·33Te1·67O6 and its composite with g-C3N4

Skeletal materials belonging to the defect pyrochlore family have been the subject of considerable interest due to their remarkable properties. In this work, a highly efficient, stable and visible light active composite photocatalytic system consisting of defect pyrochlore of composition KMn0·33Te1·67O6 (KMnTeO) and g-C3N4 (g-CN) has been successfully prepared by simple physical mixing of pre-prepared KMnTeO and g-CN components synthesized in solid state and thermal treatment of low-cost melamine, respectively. Structural, morphological and optical properties of as-prepared catalysts were deduced from powder X-ray Diffraction (XRD), Fourier Transform Infrared (FT-IR), Raman, Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (FESEM-EDX), Transmission Electron Microscopy-High Resolution Transmission Electron Microscopy (TEM-HRTEM), Ultraviolet–Visible Diffuse Reflectance Spectroscopy (UV–Vis DRS), X-ray Photoelectron Spectroscopy (XPS) and Photoluminescence (PL) measurements. The lattice parameter “a” of parent KMnTeO was obtained from Rietveld refinement of its powder XRD pattern. The FT-IR and Raman spectra of KMnTeO gave characteristic bands belonging to the defect pyrochlore structure. The photocatalytic activities of KMnTeO and composite KMnTeO-g-CN were evaluated by the degradation of methylene blue (MB). Scavenger experiments were carried out to identify the reactive species responsible for the degradation of MB. Furthermore, the reusability and stability of the photocatalysts were explored. The probable photocatalytic mechanism for MB degradation over the composite KMnTeO-g-CN was surmised according to the scavenger experiments. The work provides a new approach for the development of novel defect pyrochlore based composite photocatalysts to treat industrial wastewater containing organic pollutants.

Unraveling charge transfer dynamics in AgBr/Bi4Ti3O12/Bi2Sn2O7 ternary S-scheme heterojunction photocatalyst

In this study, AgBr/Bi4Ti3O12/Bi2Sn2O7 (ABr/BTO/BSO) composites were successfully synthesized to facilitate multi-channel fast charge transfer. This directs the charge carriers to travel along multichannel pathways and suppresses carrier recombination. The mechanisms underlying charge transfer in the dual S-scheme heterojunction composites were elucidated using density functional theory (DFT) and in situ irradiated X-ray photoelectron spectroscopy (ISI-XPS). Furthermore, electron spin resonance (ESR) and burst experiments verified h+, ·O2 -, and ·OH as the primary active species in the catalytic process. The ABr/BTO/BSO composites demonstrated exceptional photocatalytic redox capabilities, completely degrading rhodamine B (RhB) and achieving degradation rates of 77.21% for tetracycline (TC) and 81.04% for Cr (VI). Both experimental and theoretical analyses confirmed the intrinsic efficacy of photo-induced electron movement within the composites. This research introduces innovative design concepts and strategies for the advanced exploration of electron channel transfer in ABr/BTO/BSO ternary composites and the development of novel composite photocatalytic systems.

Efficient and stable immobilization of TiO2-based composite photocatalytic system for separation and purification of organic pollutants in wastewater under solar light

Photocatalytic removal of organic pollutants emerging from untreated industrial and aquaculture wastewater are still limited by catalytic efficiency and stability in practical application. In this study, we report the development of a silicone-immobilized, PEG-assisted Ag-doped TiO2 composite for efficient and sustainable removal of organic pollutants under solar irradiation. Firstly, a silicone-immobilized pristine TiO2 (S-TiO2) photocatalytic system was developed, demonstrating superior and stable removal of the organic pollutant Rhodamine B (Rh B) compared to PVA-TiO2 and dip-coated TiO2. Subsequently, pristine TiO2 was modified with the surfactant PEG, Ag species (Ag2O, Ag3PO4), and synthesized using the hydrothermal method, immobilized on silicone (S-H-PEG/PAgT). The S-H-PEG/PAgT, characterized by SEM, XRD, UV–Vis, and WCA revealed surface roughness, crystalline phase, excellent light absorption in the visible region, a narrow band gap, and hydrophobicity. The S-H-PEG/PAgT showed enhanced catalytic performance than S-TiO2 (Control) in the removal of tetracycline, a representative emerging organic contaminant. Furthermore, it displayed remarkable stability over 10 cycles and practicability in environmental conditions. Mechanism analysis revealed •O2– and h+ as the dominant active species involved in the catalytic reaction. Notably, a synergistic effect of surface hydrophobicity, roughness, and photocatalytic activity contributed to the reduction of pollutants. Therefore, the developed novel solar light driven S-H-PEG/PAgT photocatalytic system shows great promise for practical purification of organics pollutants in wastewater.

Reduced and modified graphene oxide with Ag/V2O5 as a ternary composite visible light photocatalyst against dyes and pesticides

Water pollution by dyes and pesticides poses significant threats to our ecosystem. In this research, a visible-light ternary composite photocatalytic system was fabricated using graphene oxide (GO) by reducing with N2H4, modifying with KOH, and decorating with Ag/V2O5. The fabricated photocatalysts were characterized through FTIR, SEM, XRD, BET, PL, EDX, ESR, UV–vis spectroscopy, TGA, ESI-MS, and Raman spectroscopy. The point zero charge of the reduced and modified GO (RMGO/Ag/V2O5) was measured to be 6.7 by the pH drift method. This ternary composite was able to achieve complete removal of methyl orange (MO) and chlorpyrifos (CP) in solutions in 80 min under the optimum operation conditions (e.g., in terms of pollutant/catalyst concentrations, pH effects, and contact time). The role of active species responsible for photocatalytic activity was confirmed by scavenger analysis and ESR investigations. The potential mechanism for photocatalytic activity was studied through a fragmentation process carried out by MS analysis. Through nonlinear fitting of the experimental data, MO and CP exhibited the best fit results with the pseudo 1st-order kinetics (quantum yields of 1.07 × 10−3 and 2.16 × 10−3 molecules photon−1 and space-time yields of 1.53 × 10−5 and 2.7 × 10−5 molecules photon−1 mg−1, respectively). The structure of the nanomaterials remained mostly intact to support increased stability and reusability of the prepared photocatalysts even after 10 successive regeneration cycles.

Surface Modification of ZnO with Sn(IV)-Porphyrin for Enhanced Visible Light Photocatalytic Degradation of Amaranth Dye.

Two hybrid composite photocatalysts, denoted as SnP/AA@ZnO and SnP@ZnO, were fabricated by a reaction of trans-dihydroxo[5,10,15,20-tetrakis(4-pyridyl)porphyrinato]tin(IV) (SnP) and ZnO with and without pretreatment of adipic acid (AA), respectively. In SnP@ZnO, SnP and ZnO are likely held together by a coordinative interaction between the pyridyl N atoms of SnP and the Zn atoms on the surface of ZnO. In the case of SnP/AA@ZnO, the SnP centers were robustly coupled with ZnO nanoparticles through the AA anchors. SnP/AA@ZnO exhibited largely enhanced photocatalytic activities for the degradation of anionic amaranth (AM) dye under a visible light irradiation, compared to SnP, ZnO, and SnP@ZnO. The degradation efficiency of AM by SnP/AA@ZnO was 95% within 60 min at a rate constant of 0.048 min-1. The remarkable photocatalytic oxidation performance of SnP/AA@ZnO was mainly attributed to the synergistic effect between SnP and ZnO. This study is valuable for the development of highly effective composite photocatalytic systems in advanced oxidation processes and is of importance for the treatment of wastewater containing dyes.

Facile fabrication of SnO2 modified hierarchical BiOI S-scheme heterojunction photocatalyst with efficient activity for carbon dioxide reduction

The use of photocatalysts on semiconductor substrates is a promising strategy for multiple use of solar energy and environmental improvement to convert CO2 to CH3OH. In this paper, a series of SnO2-modified BiOI (SnO2/BiOI) novel s-scheme heterojunction microsphere catalysts were synthesized, and the effect of temperature on the photocatalytic CO2 reduction reactivity of SnO2 grown on pure BiOI surface was systematically investigated by adjusting the calcination reaction temperature. Among all SnO2/BiOI composite photocatalytic systems, the highest CH3OH yield (1183 μmol/gcat, 4 h) was achieved when SnO2/BiOI was synthesized at 400 °C, which was 2.7 times higher than that of BiOI alone (437 μmol/gcat, 4 h). The SnO2/BiOI microspheres with s-scheme heterojunction exhibited surprising photocatalytic performance for CH3OH formation due to the formation of an internal eletricfield between SnO2 and BiOI also facilitated the separation of the photogenerated electron-hole pairs.

ZnO/Fe-thioporphyrazine composites as efficient photocatalysts for oxidation of glycerol to value-added C3 products in water

Photocatalytic selective oxidation of glycerol to value-added C3 products is a promising strategy for the valorization of glycerol. In this work, an inorganic/organic composite material by integrating zinc oxide (ZnO) with iron thioporphyrazine (FePz) was prepared to act as photocatalyst for photocatalytic oxidation of glycerol in water. The effects of FePz surface modification on the physicochemical properties and photocatalytic performance of ZnO were systemically studied. More importantly, the integration of ZnO with FePz could markedly improve the visible light absorption ability and effectively promote the separation of photogenerated charges. Meanwhile, introducing FePz onto the ZnO surface was beneficial to the adsorption capacity of glycerol. Just because of this, ZnO/FePz composite exhibited excellent photocatalytic activity for oxidizing glycerol in water, C3 products including glyceraldehyde and dihydroxyacetone were obtained from this composite photocatalytic system. Additionally, the active species responsible for glycerol oxidation were also determined.

Construction of Multi-Defective ZnMn2O4/Carbon Nitride Three-Dimensional System for Highly Efficient Photocatalytic Sulfamethoxazole Degradation

Rational design of composite nanostructured photocatalytic systems with good sunlight absorption capacity and efficient charge separation and transfer ability is an urgent problem to be solved in photocatalysis research. Here, a ZnMn2O4 decorated three-dimensional carbon nitride with O, C co-doping, and nitrogen defect composite photocatalytic system was prepared using a simple hydrothermal method and subsequent calcination method. For the photocatalytic reactions, the presence of heterostructures, C, O co-doping, and nitrogen defects greatly promotes the separation and transfer of charges at the semiconductor/semiconductor interface under the local electric field, thereby extending its service life. The photocatalytic degradation efficiency of sulfamethoxazole in water is as high as 94.3% under the synergistic effects, which is also suitable for the complex water environment. In addition, the synthesized photocatalyst has good chemical stability and recyclability. This study provides a new opportunity to solve the problem of environmental pollution.

Graphite carbon nitride loaded nitrogen-doped carbon and cobalt nanoparticles ternary photocatalyst for enhanced solar-driven hydrogen evolution

In this paper, we designed a composite photocatalytic system in which cobalt nanoparticles (Co NPs) are attached to nitrogen-doped carbon (N-d-C) and co-bonded to the surface of the noted photocatalyst graphite carbon nitride (g-C3N4), showing an excellent photocatalytic hydrogen production. The bulk g-C3N4 was formed in the first thermal treatment in air using melamine as a precursor. Subsequently, the secondary calcination under N2 led to the synchronous fabrication of N-d-C/Co NPs and their combination with g-C3N4 to form a novel ternary photocatalyst (g-C3N4/N-d-C/Co NPs). Co NPs exposed on the surface of the nanomaterials endowed much more reaction sites than g-C3N4 for photocatalytic hydrogen production. Meanwhile, the embedded N-d-C provided an additional transfer approach for photocarriers. The as-prepared composite nanomaterials own a relatively high specific surface area of 97.45 m2 g−1 with an average pore size of 3.83 nm. As a result, compared with pristine g-C3N4 (∼25.35 μmol g−1 h−1), the photocatalytic performance was increased by over 10 times (∼270.05 μmol g−1 h−1). Our work gives a novel approach for highly active g–C3N4–based photocatalysts in the field of photocatalysis.

Evolutionary mechanism of Ni-ZIF/CdS calcination for efficient photocatalytic hydrogen evolution

In this work, we develop Ni/Ni3S2/CdS composite photocatalytic system from annealing of CdS nanosphere coated Ni-ZIF by simple solvothermal method. The Ni/Ni3S2/CdS synthesized after calcination at 700 °C exhibits the best hydrogen evolution performance with an average hydrogen evolution rate of 2104.02 μmol/g/h, which is 152 times higher than that of pure CdS, and external quantum efficiency is 41.9% (λ = 420 nm). Using a series of characterization methods, we revealed that CdS is the photosensitizer, Ni is the catalytic active species, and Ni3S2 formed between Ni and CdS formation plays an important role in charge separation as confirmed by time resolved emission spectroscopy. In addition, the regulation of Ni loading is achieved by changing the annealing time and the molar ratio of Ni salt to CdS. These results demonstrate that Ni/Ni3S2/CdS is a favorable photocatalyst for efficient photocatalytic hydrogen evolution.

One-Dimensional CdS/SrTiO3/Carbon Fiber Core–Shell Photocatalysts for Enhanced Photocatalytic Hydrogen Evolution

The photocatalytic hydrogen production efficiency of a single SrTiO3 photocatalytic catalyst is often low, which is mainly due to the serious combination of electrons and holes produced by photocatalysis as well as the mismatch of the redox capacity and light absorption range. Construction of semiconductor heterojunctions can solve these problems. CdS has a narrow band gap, which can effectively utilize visible light, and it has a band structure matched with that of SrTiO3. Therefore, CdS is considered as an ideal candidate for constructing heterojunctions with SrTiO3. In this paper, bamboo pulp fibers were used as the substrate, and SrTiO3 was coated on the substrate through the solvothermal process. CF/SrTiO3 rich in oxygen vacancies was formed by high temperature carbonization, and heterojunctions were formed by loading CdS on the surface of the CF/SrTiO3 composite material through the hydrothermal method, thus obtaining one-dimensional CF/SrTiO3/CdS core–shell photocatalysts. The structure and photocatalytic hydrogen production performance of the CF/SrTiO3/CdS core–shell photocatalysts were mainly studied. The photocatalytic hydrogen production experiment showed that the hydrogen production rate of the CF/SrTiO3/CdS-2 sample under the optimized process was as high as 577.39 μmol/g·h, which was about 11 times that of the CF/SrTiO3 sample. In this composite photocatalytic material system, the loading of the CdS nanospheres could enhance the visible light absorption capacity of the composite catalyst, promote the rapid separation and high-speed migration of photocarriers, and significantly improve the photocatalytic activity.

Construction of g-C3N4/Ag/TiO2 Z-scheme photocatalyst and Its improved photocatalytic U(VI) reduction application in water.

The reduction of soluble U(VI) to insoluble U(IV) by photocatalytic technology is considered to be a valid method to remove U(VI) from water. Herein, g-C3N4/Ag/TiO2 Z-scheme heterojunction was synthesized for photocatalytic U(VI) reduction application. The SEM, XRD and XPS characterization results showed that a ternary g-C3N4/Ag/TiO2 composite photocatalyst was synthesized successfully. g-C3N4/Ag/TiO2 exhibited excellent photocatalytic reduction performance for U(VI) under visible light irradiation. After 30 min irradiation, the removal rate of U(VI) was above 99%. XPS indicated that the majority of U(VI) on the surface of g-C3N4/Ag/TiO2 was reduced to U(IV). In addition, the photocatalytic activity of g-C3N4/Ag/TiO2 has been kept significantly after five rounds of experiments, indicating good stability. g-C3N4/Ag/TiO2 exhibited better photocatalytic reduction of U(VI) under visible light irradiation, which is mainly ascribed to Z-scheme photocatalytic mechanism assisted by the LSPR effect (Local Surface Plasmon Resonance). Ag with plasmon resonance effect on the loading has a strong absorption of photon energy. In addition, an intermediate charge transfer channel is formed between Ag and the semiconductor to inhibit the combination of photogenerated electrons and holes, resulting in a significant increase in the photocatalytic activity of the photocatalyst. This idea has some significance in design of other composite photocatalytic systems.

A composite photocatalytic system based on spent alkaline Zn–Mn batteries for toluene removal under multiple conditions

The resource utilization of spent alkaline Zn–Mn batteries (S-AZMB) has always been a hot issue in the field of energy regeneration and environmental protection. The cumbersome and complicated purification process is the reason for their limited recycling. Not long ago, we proved that unpurified S-AZMB can be used directly: construct a Z-scheme photocatalytic system by combining with commercial TiO2 through high-temperature calcination. In order for this finding to be truly adopted by the application market, the high energy consumption calcination process needs to be improved urgently. In this work, we explore the temperature dependence of performance for the composite photocatalyst (TiO2@S-AZMB). A series of experimental results confirm that lowering the calcination temperature not only conducive to improving the separation efficiency of photogenerated electron-hole pairs, but also can significantly improve the environmental adaptability of the catalyst. Specifically, the catalyst synthesized by calcination temperature at 200 °C exhibits higher toluene removal efficiency than that at 500 °C under different initial concentration of pollutants, relative humidity, light intensity and oxygen content. This study not only further improves the photocatalytic performance of the composite catalyst, but also accords with the idea of energy saving and emission reduction, which provides more space for the possibility of recycling S-AZMB.

LED-driven photocatalysis of toluene, trichloroethylene and formaldehyde by cuprous oxide modified titanate nanotube arrays

In this study, cuprous oxide modified titanate nanotube arrays photocatalyst (Cu2O/TNAs), a p-n type hetero-structure, was successfully synthesized by square wave voltammetry electrodeposition method (SWVE) with copper (II) acetate monohydrate as precursor. Cu2O/TNAs photocatalysts were characterized by SEM, XRD, XPS, and UV–vis DRS to investigate the physical and chemical properties such as surface structure, light absorption, and element composition. Results of characterization indicated that the Cu2O nanoparticles (Cu2O NPs) were firmly deposited on the surface of TNAs without significant morphological change. The enhanced photocatalytic (PC) performance of as-synthesized materials was exemplified by the test of photocurrent, which revealing that the average photocurrent density of Cu2O/TNAs (0.95 μA cm−2) was 1.38 times higher than TNAs (0.69 μA cm−2) under 24.2 mW cm−2 LED irradiation. Three VOCs (volatile organic compounds), namely, Toluene, Formaldehyde and Trichloroethylene can be completely removed in the Cu2O/TNAs PC process with rate constants (kobs) of 2.08 × 10−2, 3.11 × 10−2, and 6.58 × 10−2 min−1, respectively, with the effort of the synergism of the photo-generated holes and hydroxyl radicals. Detail mechanism of hetero-junction Cu2O/TNAs composite PC system was proposed to clarify the redox reaction.

Recent Advances in TiO2-Based Heterojunctions for Photocatalytic CO2 Reduction With Water Oxidation: A Review.

Photocatalytic conversion of CO2 into solar fuels has gained increasing attention due to its great potential for alleviating the energy and environmental crisis at the same time. The low-cost TiO2 with suitable band structure and high resistibility to light corrosion has proven to be very promising for photoreduction of CO2 using water as the source of electrons and protons. However, the narrow spectral response range (ultraviolet region only) as well as the rapid recombination of photo-induced electron-hole pairs within pristine TiO2 results in the low utilization of solar energy and limited photocatalytic efficiency. Besides, its low selectivity toward photoreduction products of CO2 should also be improved. Combination of TiO2 with other photoelectric active materials, such as metal oxide/sulfide semiconductors, metal nanoparticles and carbon-based nanostructures, for the construction of well-defined heterostructures can enhance the quantum efficiency significantly by promoting visible light adsorption, facilitating charge transfer and suppressing the recombination of charge carriers, resulting in the enhanced photocatalytic performance of the composite photocatalytic system. In addition, the adsorption and activation of CO2 on these heterojunctions are also promoted, therefore enhancing the turnover frequency (TOF) of CO2 molecules, so as to the improved selectivity of photoreduction products. This review focus on the recent advances of photocatalytic CO2 reduction via TiO2-based heterojunctions with water oxidation. The rational design, fabrication, photocatalytic performance and CO2 photoreduction mechanisms of typical TiO2-based heterojunctions, including semiconductor-semiconductor (S-S), semiconductor-metal (S-M), semiconductor-carbon group (S-C) and multicomponent heterojunction are reviewed and discussed. Moreover, the TiO2-based phase heterojunction and facet heterojunction are also summarized and analyzed. In the end, the current challenges and future prospects of the TiO2-based heterostructures for photoreduction of CO2 with high efficiency, even for practical application are discussed.

Fullerene modified CsPbBr3 perovskite nanocrystals for efficient charge separation and photocatalytic CO2 reduction

Halide perovskite nanocrystals (NCs) are regarded as potential candidates for photocatalytic CO2 reduction owing to their appropriate band structure and outstanding visible-light harvesting abilities. Nevertheless, the intrinsic radiative recombination and the structural instability of these materials have always been the obstacles to their practical applications in CO2 photoreduction. Herein, we demonstrate the design and fabrication of a fullerenes C60/CsPbBr3 composite, which is applied as an efficient and stable photocatalyst for visible-light-driven CO2 reduction. C60 with highly delocalized π bond structure serves as electron acceptors to acquire photo-generated electrons from CsPbBr3, thus facilitating the charge separation in this composite photocatalytic system. Consequently, largely improved CO2 photoreduction activity is achieved for the C60/CsPbBr3 catalytic system, with an average electron consumption rate 1.9 times that of the pristine counterpart. Our work has provided an effective strategy for the construction of halide perovskite-based composite systems with enhanced photocatalytic performance, which have potential applications in artificial photosynthesis.

Bio-waste-derived few-layered graphene/SrTiO3/PAN as efficient photocatalytic system for water splitting

Bio-waste-derived few-layered graphene/SrTiO3/PAN photocatalytic systems obtained via electrospinning technique have been investigated as promising, inexpensive and efficient photoelectrochemical materials for hydrogen production through the solar water-splitting. For the first time, a few-layered graphene synthesized from biologically waste materials such as a rice husk and walnut shell was used as a co-catalyst in a composite photocatalytic system. Results obtained in this work showed that the presence of the graphene is not only promoting the decrease of the band gap of the photocatalytic system, but also positively alter the effective separation of photoinduced charges. At the same time, those composite photocatalytic systems demonstrated a higher rate of the hydrogen release during the water splitting reaction when compared with the pure SrTiO3. Performance of the bio-waste-derived few-layered graphene/SrTiO3/PAN as a photocatalyst in the water-splitting reaction under the UV has been investigated. The developed photocatalytic systems based on few-layered graphene derived from bio-wastes, SrTiO3 and PAN are perspective candidates for production of hydrogen under splitting water-alcohol mixtures.

A short review on recent progress of Bi/semiconductor photocatalysts: The role of Bi metal

Bi/semiconductor photocatalysts have extensively been applied in the production of hydrogen, CO2 reduction and environmental remediation in recent years. This short review summarizes the role of Bi metal as a plasma photocatalyst and cocatalyst. As a cocatalyst, Bi metal can be electron/hole trappers, charge transfer mediators, or oxygen vacancy coordinators. In addition, the preparation methods of the Bi/semiconductor photocatalysts are also reviewed. Challenges and future research directions related to Bi/semiconductor photocatalysts are discussed and summarized, including the use of advanced characterization techniques to refine the reaction mechanism, the difficulties of preparing Bi single atom catalyst, and the improvement of the reduction ability of Bi-based photocatalysts. This review helps understand the reaction mechanisms of the composite photocatalytic systems containing Bi metal and proposes new perspectives for designing the photocatalysts which can control air pollution via a reductive process.

Investigation of visible-light-driven photocatalytic tetracycline degradation via carbon dots modified porous ZnSnO3 cubes: Mechanism and degradation pathway

It is highly desired to enhance the photocatalytic activity of ZnSnO3 owing to its potential application prospects in the photocatalytic degradation of antibiotics in water, such as the low cost, non-toxicity, simple preparation, although ZnSnO3 possesses wide band gap (~3.2 eV). Herein, a novel carbon dots (CDs) modified porous ZnSnO3 cubic photocatalyst was designed and synthesized using a simple precipitation-calcination method, which was to utilize the up-conversion photoluminescence performance and the ability of electronic transfer of CDs, further broadening the visible light absorption range of the photocatalyst and accelerating the separation of the electron-hole pairs. The experimental results indicate that with the optimal CDs loading (3 wt%), the CDs modified ZnSnO3 exhibits 21 times higher degradation kinetic towards tetracycline (TC) than pure ZnSnO3. The enhanced photocatalytic activity of CDs-ZnSnO3 composites may be attributed to the increased absorption of visible light as well as the improved separation of interface charge carrier. The possible mechanism of antibiotic photodegradation in the CDs-ZnSnO3 composite photocatalytic system was proposed by active species capture experiment and electron spin resonance (ESR) technique. Furthermore, the possible photodegradation pathway of TC was proposed on the basis of the intermediates detected by liquid chromatography-mass spectrometry (LC-MS) technology. This work provides a feasible strategy for effectively applying ZnSnO3-based photocatalyst to photocatalytic degradation of antibiotics.

Fabrication of g-C3N4/TiO2 photocatalysts with a special bilayer structure for visible light photocatalytic application

Photocatalytic technology is a new technique for environmental purification and solar energy conversions. The development of new and efficient photocatalysts has been a research hotspot for several years and the fabrication of composite photocatalyst has attracted wide attention. Herein, g-C3N4/TiO2 photocatalyst with a special bilayer structure has been synthesized under mild solvothermal conditions with TiO2 flake as the substrate material. The combination of TiO2 and g-C3N4 effectively increased the specific surface area of the composite and was conducive to the synergistic effect. The time of solvothermal reaction influences the binding mode of g-C3N4 and TiO2, which in turn affects the photocatalytic activity. The photodegradation rate of methylene blue (MB) by g-C3N4/TiO2 composite reached 97.61 % under visible light irradiation, which was 1.46 and 1.98 times higher than those of pure g-C3N4 and TiO2, respectively. The improvement of photocatalytic performance is mainly attributed to the enhanced separation efficiency of photogenerated electron-hole pairs caused by the construction of heterojunctions, which has been confirmed by electrochemical impedance spectroscopy and optical transient current spectrum. Furthermore, the main active species in photocatalytic system were determined by radical trapping experiments and the photocatalytic mechanism of the composite photocatalytic system was further speculated.