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Intensity of photocurrent during water oxidation in BiVO4 is predominantly limited by charge transfer resistance (Rct), rather than semiconductor bulk resistance (Rbulk). Mo doping of BiVO4 can slightly reduce Rbulk but obviously decreases Rct.

Antibiotics such as sulfonamides are widely used in agriculture as growth promoters and medicine in treatment of infectious diseases. However, the release of these antibiotics has caused serious environmental problems. In this paper, photocatalytic oxidation technology was used to degrade sulfadiazine (SDZ), one of the typical sulfonamides antibiotics, in UV illuminated TiO2 suspensions. It was found that TiO2 nanosheets (TiO2-NSs) with exposed (001) facets exhibit much higher photoreactivity towards SDZ degradation compared to TiO2 nanoparticles (TiO2-NPs) with a rate constant increases from 0.017 min−1 to 0.035 min−1, improving by a factor of 2.1. Under the attacking of reactive oxygen species (ROSs) such as superoxide radicals ( O2–) and hydroxyl radicals ( OH), SDZ was steady degraded on the surface of TiO2-NSs. Based on the identification of the produced intermediates by LC–MS/MS, possible degradation pathways of SDZ, which include desulfonation, oxidation and cleavage, were put forwards. After UV irradiation for 4 h, nearly 90% of the total organic carbon (TOC) can be removed in suspensions of TiO2-NSs, indicating the mineralization of SDZ. TiO2-NSs also exhibits excellent stability in photocatalytic degradation of SDZ in wide range of pH. Even after recycling used for 7 times, more than 91.3% of the SDZ can be efficiently removed, indicating that they are promising to be practically used in treatment of wastewater containing antibiotics.

Photo-oxidation with semiconductor photocatalysts provides a sustainable and green solution for NO

The cell membrane-coated nanoparticles (MNPs) showed great potential in treating infectious disease due to their superior biofunctions in improving biocompatibility of nanoparticles and neutralization of pathogen or toxins. However, bone infection is accompanied with severe inflammation and bone loss, which also requires anti-inflammatory and osteoconductive treatment. The conventional membrane coating method has to undergo ultrasonication and extrusion procedures, which reduces the functionality of cell membrane and limits the choice of nanoparticles. In this study, we proposed an electroporation-based membrane coating strategy to facilitate the synthesis of MNPs to tackle those problems. Methods: Magnetic composite nanoparticles with osteoconductive Ca3(PO4)2 and bactericidal TiO2 were assembled into macrophages through phagocytosis and then collected to expose in electric field for obtaining macrophage membrane-coating nanoparticles. By using molecular dynamics simulation and materials characterizations, the cell membrane coating efficiency was confirmed. The in vitro anti-bacterial and anti-inflammatory abilities were tested by bacteria culturing and immune cells activation. Then drug-resistant bacteria induced bone infection model was established to verify its in vivo therapeutic effects. Results: The coated membrane prepared through electroporation reserved the integrality of membrane structure and right-sidedness, with more functional proteins. Those led to the superior properties of recognition and adsorption with bacteria, toxins and inflammatory cytokines. Owing to the benefits of electroporation, the MNPs exhibited significant better antibacterial and anti-inflammatory abilities for enhancing the tissue repair process. Conclusion: This study provides a novel self-assembly cell membrane coating strategy by electroporation to construct multifunctional membrane-coating nanoparticles for bone infection treatment. This strategy not only improves the functions of coated membrane, but is also proved to be universal for varies nanoparticles or cells, indicating a great potential for future applications in the bioengineering field.

We report the first visible light photocatalytic oxidation of NO on CdS nanorods (CdS-NRs), one of the typical reduction type semiconductor photocatalysts. The NO removal rate in a continuous reactor sharply increases from 44% to 58% after in situ deposition of Bi nanoplates on CdS-NRs. The LSPR effect of metallic Bi causes the dramatic production of superoxide radicals (˙O2-) and singlet oxygen (1O2) that are responsible for the oxidation of NO.

Photocatalysis has become a focal point in research as a clean and sustainable technology with the potential to solve environmental problems and energy crises. The loading of noble-metal co-catalysts can substantially improve the photocatalytic efficiency of semiconductors. Because the high cost and scarcity of noble metals markedly limit their large-scale applications, finding a noble-metal-alternative co-catalyst is crucial. MXene, a novel 2D transition metal material, has attracted considerable attention as a promising substitute for noble metal co-catalysts owing to its cost-efficiency, unique 2D layered structure, and excellent electrical, optical, and thermodynamic properties. This review focuses on the latest advancements in research on MXenes as co-catalysts in relatively popular photocatalytic applications (hydrogen production, CO2 reduction, nitrogen fixation, and organic pollutant oxidation). The synthesis methods and photocatalytic mechanisms of MXenes as co-catalysts are also summarized according to the type of MXene-based material. Finally, the crucial opportunities and challenges in the prospective development of MXene-based photocatalysts are outlined. We emphasize that modern techniques should be used to demonstrate the effects of MXenes on photocatalysis and that the photocatalytic activity of MXene-based photocatalysts can be further improved using defective engineering and recent phenomena such as the localized surface plasmon resonance effect and single-atom catalysis.

Hollow transition metal oxides have important applications in the degradation of organic pollutants by a photo-Fenton-like process. Herein, uniform, highly dispersible hollow CuFe2O4/C nanospheres (denoted as CFO/C-PNSs) were prepared by a one-pot approach. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images verified that the CFO/C-PNS catalyst mainly presents hollow nanosphere morphology with a diameter of 250 ± 30 nm. Surprisingly, the photodegradation test results revealed that CFO/C-PNSs had an excellent photocatalytic performance in the elimination of various organic contaminants under visible light through the efficient Fenton catalytic process. Due to the unique hollow structure formed by the assembly of ultra-small CFO/C subunits, the catalyst exposes more reaction sites, improving its photocatalytic activity. More importantly, the resulting magnetically separable CFO/C-PNSs exhibited excellent stability. Finally, the possible photocatalytic reaction mechanism of the CFO/C-PNSs was proposed, which enables us to have a clearer understanding of the photo-Fenton mechanism. Through a series of characterization and analysis of degradation behavior of CFO/C-PNS samples over antibiotic degradation and Cr(VI) reduction, •OH radicals generated from H2O2 decomposition played an essential role in enhancing the reaction efficiency. The present work offered a convenient method to fabricate hollow transition metal oxides, which provided impetus for further development in environmental and energy applications. Highlights: Novel hollow CuFe2O4/C nanospheres were prepared by a facile and cost-effective method. CuFe2O4/C exhibited excellent photo-Fenton-like performance for antibiotic degradation. Outstanding photocatalytic performance was attributed to the specific hollow cavity-porous structure. A possible mechanism for H2O2 activation over hollow CuFe2O4/C nanospheres was detailed and discussed.

2D organic g-C3N4 photocatalysts are low cost materials with facile fabrication, suitable bandgap, tunable functionalization, excellent thermal/chemical-physical stability and exceptional photocatalytic behavior, raising considerable interest in photocatalytic and redox research areas. The photocatalytic performance of g-C3N4 mostly relies on the separation/transfer of photo-generated carriers. The mobility properties of the carrier largely determine the formation of reactive species, which have a high impact on surface reactions in the photocatalytic systems based on g-C3N4. This review paper outlines the works carried out so far on the optimization of the carrier mobility dynamics of 2D g-C3N4 materials via the internal and external modification strategies. The peculiar layered planar structure of g-C3N4 allows charge carrier mobility at the interface, in-plane and interlayer, and mechanisms of the charge separation/transfer will also be discussed. Comprehensive conclusions and perspectives on the modification of g-C3N4 leading to satisfactory carrier mobility will be given as well.

Cd0.5Zn0.5S/g-C3N4 (CZS/CN) step-like heterojunction composites were facilely synthesized by annealing a sandwich of cadmium−zinc−thiourea precursors in one pot. The types of the used raw materials and the preparation procedure were simplified as much as possible in this work. The obtained hybrid exhibited enlarged specific surface area and higher separation/transfer efficiency of charge carriers compared to pure Cd0.5Zn0.5S and g-C3N4, thus exhibited much enhanced photocatalytic efficiency for dye degradation under visible-light irradiation. The interfacial charge-transfer mechanism of the formed step-scheme (S-scheme) heterojunction between Cd0.5Zn0.5S and g-C3N4 were carefully investigated and discussed. This work could widen the application prospect of the CdxZn1–xS/g-C3N4 composite and provide new ideas to the design and fabrication of novel heterojunctions with robust photocatalytic performance.

Tailoring the microstructure of pristine TiO2 is essential to narrow its band gap and prolong the charge lifetime. In particular, strategies involving fluorine have been used successfully to tune the surface chemistry, electronic structure, and morphology of TiO2 photocatalysts to improve their photocatalytic activity based on the strong complexation between fluoride ions and TiO2 and the high electronegativity of fluorine. In this review, we summarize the strategies involving fluorine to establish highly efficient TiO2 photocatalytic systems or fabricate highly efficient TiO2 photocatalysts. The main fluorine effects (i.e. the effects of fluorine on photocatalysis) include the following four aspects: (1) Surface effects of fluoride on TiO2 photocatalysis, (2) effects of fluorine doping on TiO2 photocatalysis, (3) fluoride-mediated tailoring of the morphology of TiO2 photocatalysts, and (4) the effects of fluorine on non-TiO2 photocatalysis. Additionally, the unique applications of these fluorine effects in photocatalysis, including selective degradation of pollutants, selective oxidation of chemicals, water-splitting to produce H2, reduction of CO2 to produce solar fuels, and improvement of the thermostability of TiO2 photocatalysts, are reviewed.

The improvement of catalytic efficiency of catalyst is a challenging topic especially for solid catalyst that has restrained surface to contact reactants. Herein, we reported an effective way to improve the catalytic efficiency by designing composites catalyst (to induce synergistic effect) and performing the reaction under united technologies (to make cooperative contribution). As a model case, La–Fe–O mixture (abbreviated as LFO) and graphitic carbon nitride (abbreviated as g-CN) composites (LFO@CN-n, where n means the molar ratio of the precursors of LFO to g-CN) were synthesized and used as photo-Fenton catalysts for oxidation removal of dyes in wastewater. Results showed that LFO@CN-16, with g-CN loading of 69%, has the properties of both LFO and g-CN, and exhibits high efficiency for dyes oxidation in the presence of H2O2 and light irradiation, with 98% rhodamine B conversion within 25 min, for example. Mechanistic studies suggested that •OH radicals produced from H2O2 are the reaction intermediates, which participate both in the Fenton- and the photo-catalytic processes. Moreover, the catalyst can be reused for at least 5 cycles with no appreciable loss of activity, and can be applied to various organic dyes containing benzene-like cyclic structures with high efficiency.

Three-dimensional (3D) TiO2 hollow structures have attracted much attention due to their unique properties. However, the large bandgap of (3.2 eV) results in the fact that anatase TiO2 photocatalyst can only be excited by UV light, which only accounts for 3–5% of the solar energy. On considering that nobel metallatic nanomaterials can harvest visible light due to surface plasmon resonance (SPR) effect, in this paper, three kinds of Au nanoparticles with different morphologies, namely Au nanospheres (Au-NSs), Au nanorods (Au-NRs) and Au nanopentogons (Au-NPs) were prepared and used as photosensitizers to modified TiO2 hollow nanoboxes (TiO2-HNBs), aiming to explore high efficient visible-light-responsive photocatalyst. The photoreacitivty of Au/TiO2-HNBs was evaluated by photoctalytic oxidation of Rhodamine B (RhB) and NO under visible irradiation (λ > 420 nm). It was found that the visible photoreactivity of TiO2-HNBs was greatly enhanced after modified with Au nanoparticles, and TiO2-HNBs loaded with Au-NRs exhibit the highest visible photocatalytic activity towards both RhB degradation and NO oxidation. Upon visible irradiation, SPR effect induces the production of hot electrons from the Au nanoparticles, which can further transfer to the conduction band of TiO2-HNBs to produce superoxide radicals (·O2−), resulting in an efficient separation of photo-generated electron-hole pairs. The photoreactivity of Au-NRs/TiO2-HNBs towards RhB degradation almost keeps unchanged even after recycling used for 5 times, indicating that it is promising to be use in practical applications. Keywords: Au, TiO2, Hollow nanobox, Surface plasmon resonance, Photocatalysis

A new conductive metal–organic-framework (MOF) photocatalyst, (WO4)2−-doped bismuth terephthalate (referred to as nNa2WO4BiBDC), was synthesized and characterized by varying the precursor molar ratio (n = 0.1, 0.3, 0.4, and 0.5) of Na2WO4/Bi(NO3)3 in the presence of terephthalic acid through a one-pot solvothermal process. This study found that doping (WO4)2− into BiBDC enhanced the separation of photo-generated carriers, improved the photocatalytic properties of bismuth terephthalate (BiBDC), and enabled the application in Cr(VI) reduction under UV light irradiation with the synergic effect from citric acid acting as a hole scavenger. Among all the precursor ratios of Na2WO4/Bi(NO3)3 used, 0.4Na2WO4BiBDC has the optimum performance, leading to triple gain in reduction efficiency for undoped BiBDC. The synthetic strategy to dope (WO4)2− into a layered MOF as a viable option for modification of MOFs was demonstrated in this study. Finally, the photoreduction of Cr(VI) by (WO4)2-doped bismuth terephthalate enables a new promising wastewater treatment option.

Single atomic Au (Au-SA) is firmly anchored on the surfaces of defective TiO2 (DT) hollow microspheres with oxygen vacancies (Ov), which sharply improves their light-harvesting ability, stimulates charge separation, and facilitates the adsorption and activation of acetone, thus dramatically enhancing their photoreactivity towards acetone oxidation.

Hierarchically structured nanomaterials have attracted much attention owing to their unique properties. In this study, TiO2 nanofibers assembled from nanosheets (TiO2-NFs-NSs) were fabricated through electrospinning technique, which was followed by hydrothermal treatment in NaOH solution. The effect of hydrothermal reaction time (0–3 h) on the structure and properties of TiO2 nanofibers (TiO2-NFs) was systematically studied, and TiO2-NFs was evaluated in terms of the photocatalytic activity toward photocatalytic oxidation of acetone and the photoelectric conversion efficiency of dye-sensitized solar cells. It was found that (1) hydrothermal treatment of TiO2-NFs in NaOH solution followed by acid washing and calcination results in the formation of TiO2-NFs-NSs; (2) upon extending the hydrothermal reaction time from 0 h to 3 h, the BET surface area of TiO2-NFs-NSs (T3.0 sample) increases 3.8 times (from 28 to 106 m2 g−1), while the pore volume increases 6.0 times (from 0.09 to 0.54 cm3 g−1); (3) when compared with those of pristine TiO2-NFs (T0 sample), the photoreactivity of the optimized TiO2-NFs-NSs toward acetone oxidation increases 3.1 times and the photoelectric conversion efficiency increases 2.3 times. The enhanced photoreactivity of TiO2-NFs-NSs is attributed to the enlarged BET surface area and increased pore volume, which facilitate the adsorption of substrate and penetration of gas, and the unique hollow structure of TiO2-NFs-NSs, which facilitates light harvesting through multiple optical reflections between the TiO2 nanosheets.

The separation efficiency and recombination rate of photogenerated electron–hole pairs play a vital role in photocatalytic activity. We report the incorporation of ultra-small subnano TiOx clusters as outstanding cocatalysts on the surface of plasmonic Ag/AgCl to boost the simulated sunlight photoreactivity. The formed structure is in favour of an efficient photoinduced electron–hole transfer process and suppressing the recombination rate, yielding an enhanced photocatalytic activity. The experimental results show that TiOx@Ag/AgCl exhibits an extraordinarily high activity in the photodegradation of tetracycline (TC) under simulated sunlight irradiation, which is about 21.7 times higher than that of bare Ag/AgCl. Their corresponding apparent quantum efficiency (AQE) is up to 0.917% at 435 nm and 17.459% at 350 nm during the photodegradation of TC, respectively. Moreover, TiOx@Ag/AgCl shows an outstanding long-term stability without obvious performance loss even after ten cycles of photodegradation. The possible enhancement mechanism of the reaction rate is proposed based on the compositional, structural, and optical property analysis. We found that h+ was the major reactive species in the photodegradation process of TC. Our findings on ultra-small TiOx cocatalysts would shed light on the design and development of highly efficient oxide cluster cocatalysts.

Deeply photocatalytic oxidation of nitrogen oxides is still difficult to achieve, mainly limited by few intrinsic active sites and inefficient carrier separation of photocatalysts. Accordingly, we develop a simple room temperature tactic to introduce oxygen vacancies (OVs) into Bi

Pickering emulsion (PE) stabilized by semiconductors for photocatalysis applications has received growing endorsement over the last decade due to its high interfacial activity. However, since most semiconductors inherently possess a strongly hydrophilic or hydrophobic surface and are unable to stabilize PE microcapsules by themselves, pretreating the surface of semiconductor powder with foreign modifier was usually unavoidable and inconvenient before the PE construction. Even worse, the added modifier inevitably limited the contact between the semiconductor and the reactant during the photocatalysis process. Herein, an oil-in-water PE was successfully obtained in one step without pretratment of the semiconductor, where the dye-contained wastewater and insoluble organic matter acted as the water and oil phases, respectively, and the dye molecules in water could directly assist TiO2 particles to become the stabilizer. The TiO2 powder in the formed PE system exhibited markedly enhanced photoactivity for dye degradation over that in traditional non-emulsified systems, and the PE microcapsules could be easily recovered for reuse and withstand long-term irradiation without severe demulsification. This work not only highlights a convenient and promising approach to build Pickering emulsion as a novel photocatalytic system with extremely high efficiency and recyclability, but also provides a new way of thinking on how to simplify the PE construction to meet more requirement in future practical applications.

Bi2WO6 is a typical visible-light-responsive semiconductor photocatalyst with a layered structure. However, the relatively large bandgap (2.6–2.8 eV) and quick recombination of photo-generated carriers result in its low quantum efficiency. In this paper, Bi-nanospheres-modified flower-like Bi2WO6 was successfully prepared by solvothermal treatment of Bi2WO6 powders in Bi(NO3)3 solution using ethylene glycol as reductant. The photoreactivity of this photocatalyst was evaluated by the oxidation of NO in a continuous-flow reactor under irradiation by a visible LED lamp (λ > 400 nm). It was found that both Bi nanospheres and flower-like Bi2WO6 precursor exhibit very poor photocatalytic activity with NO removal rates of only 7.7% and 8.6%, respectively. The photoreactivity of Bi/Bi2WO6 was found to steadily increase from 12.3% to 53.1% with increase in the amount of Bi nanospheres from 0 to 10 wt%. However, with further increase in the loading amount of Bi nanospheres, the photoreactivity of Bi/Bi2WO6 hybridized photocatalyst begins to decrease, possibly due to the light filtering by the Bi nanospheres. The enhanced visible photoreactivity of Bi/Bi2WO6 towards NO abatement was attributed to surface plasmon resonance driven interfacial charge separation. The excellent stability of Bi/Bi2WO6 hybridized photocatalyst towards NO oxidation demonstrates its potential for applications such as air purification.

As a typical visible-light-responsive organic semiconductor photocatalyst, graphitic carbon nitride (gCN) only exhibits moderate photoreactivity beacuse of its low specific area, limited light harvesting ability and quick recombination of photo-generated carriers. Herein, we report the fabrication of gCN nanosheets (gCN-NSs) with large BET surface area, excellent visible-light-absorptive property and efficient separation of carriers by direct polymerization of amidinourea, the product from the hydrolysis of dicyandiamine (DCDA). When compared with that of bulk gCN (S0) synthesized by direct polymerization of DCDA, the visible photocatalytic hydrogen evoluation rate of gCN-NSs (S2 sample) obtained by condensation of amidinourea improved 4.9 times, which is also 2.4 times higher than that of gCN-NSs (Su sample) which is prepared by polymerization of urea. The enhanced visible photocatalytic activity gCN-NSs (S2) toward hydrogen production can be ascribed to the combined effects of enlarged BET surface that provides more active sites for adsorption and photocatalytic reaction, compacted π-π layer stacking which facilitates the efficient separation of photo-generated carriers, negatively shifted CB potential and improved hydrophilic property that favor the electron transfer at the interfaces between gCN and water. In addition, the product yield of gCN-NSs (S2 sample) from the polymerization of amidinourea is 11.9%, which is 10.8 times higher than Su sample that prepared from urea (only 1.1%).

Due to its low cost and high efficiency, dye-sensitized solar cells have been widely studied. As all of known, nanoparticles are not conducive to the separation and transmission of electrons and holes. One-dimensional (1D) TiO2 nanofibers (NF), synthesized via electrospinning method, were used to replace the nanoparticles film. It offered a direct pathway and can absorb dyes to improve the efficiency, which had revealed distinct properties as a photoanode in DSSC. In addition, ZrO2, as a barrier layer on NF, enhanced the efficiency of dye sensitized solar cell. Moreover, the ZrO2 layer can availably enhance the efficiency by preventing recombination of electron-hole between TiO2 and the dye/electrolyte. Electrochemical Impedance Spectroscopy (EIS) measurements provided evidence that the coating ZrO2 reduced recombination losses at the photoanode-TiO2-dye|I3−/I− electrolyte interface, which passivated localized surface states. Results of photovoltaic measurements of the NP/NF/ZrO2 DSSC revealed that a barrier layer of ZrO2 could improve efficiency. The NP/NF/ZrO2-based devices exhibited a higher efficiency of 6.72% than that of NP/NF (6.14%). This work provides a novel approach for the rational design of the photoanodes in DSSC, which also implies the potential application of this structure in other type of solar cells.

Graphitic carbon nitride with plentiful nitrogen vacancies (NV-g-C3N4) was prepared through a treatment of melamine under a N2 flow, and used for constructing a system of sulfite activation under visible light toward the degradation of carbamazepine. In the presence of Na2SO3 (20 mmol L−1), the use of NV-g-C3N4 (1 g L−1) increased the apparent rate constant for the photodegradation of carbamazepine (42 μmol L−1) to 0.0187 min−1, with an increasing magnitude of 270% in comparison with that obtained by using the conventional g-C3N4 (Bulk-g-C3N4). The enhanced photodegradation of carbamazepine by NV-g-C3N4 was found to be attributed to the efficient trap of photo-generated electrons by nitrogen vacancies, which inhibited the recombination of photo-generated carriers. Therefore, more holes aggregating in the valence band were available for the activation of sulfite anions to produce sulfite radicals. Sulfite radicals were identified as the major reactive species in the investigated photocatalytic system for the degradation of carbamazepine. The degradation pathway of carbamazepine induced by sulfite radicals in the NV-g-C3N4/Na2SO3 system was clarified on the basis of the identification of intermediates by GC- and LC MS. The photocatalytic activation of sulfite by metal free NV-g-C3N4 may be a useful technique for purifying waste-water containing organic pollutants.

Considerable attention has been paid to promising applications of photoactive metal–organic frameworks (MOFs) in visible-light-enhanced hydrogen production. In this study, a pillared-paddlewheel type metal–organic framework [Zn2(BODIPY)(BPDC)2]·H2O (denoted as CCNU-1) featuring BODIPY struts, and capable of efficiently absorbing visible light from 200 to 800 nm, has been fabricated, which is thought to be the first BODIPY-based MOF decorated with Pt nanoparticles as the co-catalyst for efficient photocatalytic H2 generation under visible-light illumination. Impressively, Pt/CCNU-1 exhibited a remarkable H2 production rate as high as 4680 μmol g−1 h−1 with the use of L-ascorbic acid as a sacrificial reagent from an aqueous medium, and a high apparent quantum efficiency of 9.06% at 420 nm. To our knowledge, Pt/CCNU-1 is the most visible-light photoactive Pt/MOF composite for H2 generation from water hitherto, highlighting the promising future of MOF materials in solar-to-chemical energy conversion. This work provides significant insights into the development of MOF-based systems for visible-light-responsive photocatalysts for water reduction.

Much attention has been paid to g-C3N4 (gCN), a visible-light-responsive metal-free polymeric photocatalyst. However, bulk gCN suffers from the small BET surface area and quick recombination of carriers. The photocatalytic activity of bulk gCN still needs to be improved. Herein, we systematically studied the effect of post calcination times (PCT) on the visible photoreactivity of bulk gCN towards NO oxidation and hydrogen production. It was found that aggregated gCN nanosheets (gCN-NSs) were formed after repeated calcination of bulk gCN. The BET surface areas of gCN-NSs increased 6.6 times (from 9.1 to 60.5 m2 g−1) after repeated calcination of bulk gCN for 7 times. The exfoliation of bulk gCN by post calcination results in a reduced PL intensity, increased photocurrent, diminished arc radius of EIS Nynquist plot. DFT calculation confirms the enlarged bandgap of gCN after post calcination. After repeated calcination for 7 times, the visible photoreactivity of gCN-NSs towards NO oxidation increased from 20.6% to 35.8% in a continuous reactor, and the hydrogen production rate improved from 31.3 to 764.8 umol g−1 h−1 in a batch reactor, enhanced by a factor of 24.4. The post calcination induced enhancement on the visible photocatalytic activity of gCN-NSs can be attributed to the combined effects of (1) enlarged BET surface area, (2) improved crystallinity, (3) negatively shifted CB position, and (4) exposure of (0 0 2) and (1 0 0) facets for g-CN-NSs which retarded the recombination of electron and hole pairs.

ZnIn2S4 flower-like microspheres decorated with CeO2 as cocatalyst have been successfully fabricated through a microwave-assisted hydrothermal method for visible-light carbon dioxide (CO2) photoreduction to produce methanol (CH3OH). All the composite photocatalysts exhibited a more excellent photocatalytic performance than bare CeO2 and ZIS, and reached the highest with a CH3OH evolution rate of 0.542 µmol g−1 h−1 when the content of CeO2 was 5 wt%. In the composites, the CeO2 with oxygen vacancies acted as a significant cocatalyst to efficiently trap the photogenerated electrons from ZIS and thus boosted the separation of photoinduced charge carriers, while the unique 3D structure of ZIS made it with a relatively large specific area, which could provide abundant active reaction sites and render the reactants and products diffuse more easily. This study verified the CeO2 as one of the ideal cocatalyst candidates for ZnIn2S4 in the application of photocatalytic CO2 reduction, and gave rise to an increasing interest in expanding potential applications of ZnIn2S4 based materials in the field of energy conversion.