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The activation capacity of molecular oxygen is an important indicator to evaluate the photocatalytic efficiency of photocatalysts. In this paper, WS2 nanosheet was deposited on hyper-crosslinked CTF-1-G (obtained by molecular expansion from covalent triazine framework CTF-1) to form a C-GW heterojunction, which promoted the photodegradation of pollutants and the activation of molecular oxygen. This novel C-GW heterojunction exhibited excellent degradation property for organic pollutants (tetracycline (TC), rhodamine B (RhB)) and activating molecular oxygen under visible light irradiation. Among them, C-GW15 could degrade 98% of 20 ppm TC in 60 min and 99% of 30 ppm RhB in 30 min, and it had the highest hydrogen generation rate and hydrogen production amount in 4 hours, which were 8.74 mmol h−1 g−1 and 34.94 mmol g−1, respectively. Meanwhile, C-GW15 had the strongest 3,3′,5,5′-tetramethylbenzidine oxidation capacity and could generate 1.83 μmol of ˙O2− in 60 min and the production of H2O2 was 20.8 μmol L−1 in 40 min. The results of this study clearly indicated that the combination of WS2 and CTF-1-G can enhance the visible light absorption capacity and photogenerated carrier separation efficiency, thus promoting the photocatalytic performance. Finally, a Z-type photocatalytic mechanism was proposed based on radical capture, molecular oxygen activation experiments and electron spin resonance analysis. These findings will extend the fundamental understanding of the Z-type photocatalytic mechanism and provide new opportunities for the rational design of CTF heterojunctions for the treatment of environmental pollution and clean energy conversion. [ABSTRACT FROM AUTHOR]

In this paper, a novel pristine carbon nitride (np-CN) with hollow capsule-like morphology was facilely prepared by the thermal polymerization of melamine and cyanuric chloride at 550 1C in air for 4 h. Then, modified carbon nitride (CN-P4mg) micro-flakes with zigzag edges were synthesized by the copolymerization of melamine, cyanuric chloride, and triaminotriphenylamine with a mass fraction of 0.13%. Analysis of the microstructure, surface state, porosity, and optoelectronic properties of the two samples indicates that CN-P4mg has a larger specific surface area and a lower bandgap than np-CN. Under visible light, CN-P4mg displays enhanced photocatalytic performance for the generation of hydrogen compared to that of np-CN and bulk graphite carbon nitride (g-C3N4). The photocatalytic hydrogen evolution rate of CN-P4mg reaches 16897.3 mmol g-1 h-1, which is 1.84 times that of np-CN and 72 times that of bulk g-C3N4. The experimental results confirm that the addition of triaminotriphenylamine provides a modified design for developing metal-free carbon nitride derivatives and a new route to study efficient photocatalytic materials. [ABSTRACT FROM AUTHOR]

This study developed an efficient photocatalyst for hydrogen production, consisting of CdS nanorods and the CoTPPBr4 co-catalyst. The synthesized photocatalyst was characterized using a suite of techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), photoluminescence (PL) spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). Additionally, transient photocurrent response and electrochemical impedance spectroscopy (EIS) were carried out to further probe the material's properties. Our findings demonstrate that the CoTPPBr4 co-catalyst significantly enhances the photocatalytic H2 evolution efficiency under visible light irradiation. Notably, among the tested photocatalysts, a 12.5% CoTPPBr4/CdS composite exhibited the most superior photocatalytic performance, achieving a hydrogen production rate of 41.3 mmol g−1 h−1, which is 4.1 times higher than that of pristine CdS. The introduction of CoTPPBr4 effectively facilitates charge transfer within CdS, enhances the separation efficiency of light-induced electron–hole pairs, and boosts the surface H2-evolution kinetics. This research not only introduces a promising photocatalyst for visible light-driven hydrogen production but also provides a way for the development of highly efficient and stable CdS-based hybrid semiconductor nanocomposites suitable for diverse photocatalytic applications. [ABSTRACT FROM AUTHOR]

At present, the rational design and facile synthesis of highly active and low-cost photocatalysts are still facing great challenges. Herein, a series of Zn0.5Cd0.5S/NiS (x mol%) composite photocatalysts have been synthesized via a simple and mild one-pot hydrothermal method. Compared with pure Zn0.5Cd0.5S, the NiS-loaded samples exhibit enhanced photocatalytic hydrogen generation performance, in which the Zn0.5Cd0.5S/NiS-5% sample has the highest H2 production rate of 10 855 ± 461 μmol h−1 g−1 with a quantum yield of 11.82% at 365 nm, which is almost 6.3 times higher than that of pristine Zn0.5Cd0.5S. The high activity of the Zn0.5Cd0.5S/NiS nanosheets may be attributed to their distinct nanostructure, including a short transfer distance of photoinduced charge carriers, a large number of unsaturated surface atoms, and a large surface area. Moreover, the added NiS nanoparticles served as an effective cocatalyst to promote photoinduced electron transfer and enhance the surface kinetics of H2 evolution. Our work provides a simple and effective route for the preparation of sulphur-based photocatalysts, which can significantly improve the efficiency of hydrogen production from water. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have great potential for producing photoelectrocatalyzed hydrogen and degrading pollutants, owing to several factors such as high porosity and tunable semiconductor-like properties. Wide band gaps, which restrict their use to only UV light induced reactions, and low efficiencies for the separation of photogenerated charge carriers (electrons and holes) pose significant challenges to the widespread applications of MOFs. In this study, a hierarchical hollow Pt@H-UiO-66-NH2/CdS ternary catalyst was designed and synthesized. The immobilized CdS nanoparticles (NPs) in this catalyst endow the MOF H-UiO-66-NH2 with high visible light absorption ability and the Pt NPs serve as electron sinks to improve charge carrier separation. Furthermore, the hierarchical hollow structure of H-UiO-66-NH2 in the composite contributes to boosting light absorption and shortening the distance for charge transfer. As a proof of principle, Pt@H-UiO-66-NH2/CdS catalyzes methylene blue (MB) degradation with a high rate constant of 1.025 × 10−2 and hydrogen production with a rate of 12 810 μmol g−1 h−1, the latter of which is about 2.3, 11.7 and 173 times higher than those of Pt@UiO-66-NH2/CdS, H-UiO-66-NH2/CdS and Pt@H-UiO-66-NH2, respectively. [ABSTRACT FROM AUTHOR]

Photocatalytic splitting of water for hydrogen generation is a green and renewable solution for converting solar energy to chemical energy; thus, the development of high-performance and stable photocatalytic materials has emerged as a research hotspot recently. Herein, a heterostructure composite photocatalyst of octahedral CoO uniformly modified with novel nitrogen-doped MXene quantum dots (N-MQDs) is successfully designed using a typical solvothermal approach. The optimum photocatalytic hydrogen evolution efficiency of the prepared N-MQDs@CoO heterojunction composite is 82.54 μmol g−1 h−1 with visible light, which is 16.57 times higher compared to the pure CoO. A series of photoelectrochemical tests were further performed to elucidate the photocatalytic hydrogen evolution mechanism. The remarkable improvement of activity is primarily attributed to the synergistic interaction between the closely spaced interface contacts and energy level matching among high conductivity Ti3C2 MXene quantum dots with CoO octahedra, dramatically hastening the segregation and transfer of photo-generated carriers. This study provides new ideas for the construction of MXene quantum dot-based co-photocatalysts with highly efficient photocatalytic performance and stability toward solar energy conversion applications. [ABSTRACT FROM AUTHOR]

Solar-driven photocatalytic hydrogen generation via splitting water requires an efficient visible light active photocatalyst. In this work, Ni cocatalysts on a TiO2 composite photocatalyst with different graphene oxide (GO) contents were prepared using a hydrothermal method and characterized by TEM, XRD, UV-vis, Raman and PL spectra. The results show that the synthesized TiO2/GO/Ni nanosheet composites have a large specific surface area and can provide a large number of active sites for a photocatalytic hydrogen production reaction. GO can broaden the optical absorption range of TiO2 and absorb more visible light, thus stimulating more photogenerated electron–hole pairs. At the same time, GO can collect electrons and promote the separation of photogenerated electron–hole pairs. Ni, as a cocatalyst, can be used as an active site for hydrogen ion adsorption, which is conducive to promoting the migration of photogenerated electrons in the system and prolonging the life of photogenerated electrons and holes, thus ensuring the high efficiency of the photocatalytic reaction. [ABSTRACT FROM AUTHOR]

ZnIn2S4 is considered one of most promising green catalysts for visible light driven photocatalytic H2 generation, but it suffers from relatively low photocatalytic performance. Here, we for the first time report the design and preparation of an efficient ZnIn2S4-based catalyst using porous ZnWO4 as cocatalyst (denoted ZIS/PZW). ZIS/PZW consists of flower-like microspheres composed of ZnIn2S4 nanosheets embedded with porous ZnWO4 nanoflakelets. The as-synthesized ZIS/PZW showed excellent photocatalytic performance for H2 generation with an optimal hydrogen production rate of 8.86 mmol g−1 h−1. Further investigation revealed that the porous ZnWO4 cocatalyst could lead to the formation of dense contact sites with ZnIn2S4 nanosheets, thus benefiting electron migration. The hydrogen generation rate was found to be 2.15 times higher than that when solid ZnWO4 nanoparticles acted as cocatalyst. Our work highlights the importance of finely designing cocatalysts and provides a new route for the further development of high-efficiency ZnIn2S4-based photocatalysts for H2 generation. [ABSTRACT FROM AUTHOR]

The rapid recombination of photogenerated carriers and strong photocorrosion have considerably limited the practical application of CdS in the field of photocatalysis. Loading a cocatalyst has been widely utilized to largely enhance photocatalytic activity. In the present work, a WC@C cocatalyst was prepared by a novel molten salt method and explored as an efficient noble-metal-free cocatalyst to significantly enhance the photocatalytic hydrogen evolution rate of CdS nanorods. The WC@C/CdS composite photocatalyst with a 7 wt% content of WC@C showed the highest photocatalytic hydrogen evolution rate of 8.84 mmol g−1 h−1, which was about 21 and 31 times higher than those of CdS and 7 wt% Pt/CdS under visible light irradiation. A high apparent quantum efficiency (AQY) of 55.28% could be achieved under 420 nm monochromatic light. Furthermore, the photocatalytic activity of the 7 wt% WC@C/CdS photocatalyst exhibited good stability for 12 consecutive cycles of the photocatalytic experiment with a total reaction time of 42 h. The excellent photocatalytic performance of the photocatalyst was attributed to the formation of a Schottky junction and the loading cocatalyst, which not only accelerated the separation of the photogenerated carrier but also provided a reactive site for hydrogen evolution. This work revealed that WC@C could act as an excellent cocatalyst for enhancing the photocatalytic activity of CdS nanorods. [ABSTRACT FROM AUTHOR]

The study of environmentally friendly semiconductor photocatalysts has important practical significance for efficient photocatalytic hydrogen evolution. In this experiment, type II heterojunction NiCo-LDH/CeO2 was prepared by in situ loading, and the NiCo-LDH/CeO2 catalyst showed good activity under simulated sunlight irradiation. Under simulated visible light irradiation, its hydrogen production rate reached 2.7 mmol h−1 g−1, which was higher than that of NiCo-LDH (0.86 mmol h−1 g−1). Through a series of characterization data, it can be concluded that the heterojunction successfully constructed by the close contact between NiCo-LDH and CeO2 accelerates the separation of photogenerated electrons and holes and can effectively inhibit the recombination of the two so that more electrons are involved in the hydrogen evolution reaction. The material has good interfacial charge transfer performance, which improves the photocatalytic performance. This work can provide an effective method for the research and development of NiCo-LDH. [ABSTRACT FROM AUTHOR]

Herein we have demonstrated the synthesis of nitrogen vacancy enriched exfoliated B-doped g-C3N4 (e-BCN) through a facile thermal exfoliation method, characterized it using different analytical techniques and compared its photocatalytic activity with that of bulk B-doped g-C3N4 (BCN). The decrease in peak intensity and slight shift of the 2 value in the PXRD patterns confirmed the successful exfoliation of bulk BCN to an e-BCN nanosheet. FESEM and HRTEM images also indicated the formation of a thin layered nanosheet of e-BCN as compared to bulk BCN. The PL and EIS data suggested the reduced recombination rate and superior separation capability of the photo-generated charge carriers of e-BCN. The introduction of nitrogen vacancies on the surface of e-BCN is confirmed by the FTIR and XPS analyses. The increased photocurrent density of 524 μA cm−2 displayed by e-BCN indicated the better availability of photo-generated electrons due to the higher separation of charge carriers than in the bulk BCN. The as-prepared e-BCN nanosheet exhibited enhanced photocatalytic performance 1.2 and 3.7 fold greater than that of bulk BCN towards ciprofloxacin degradation and H2 generation, respectively, under visible light irradiation. The excellent photocatalytic behavior of e-BCN was ascribed to the augmented active sites with reduced recombination efficiency and increased separation ability of the photo-induced e−/h+ pairs of the e-BCN nanosheet. This work suggested the facile fabrication of e-BCN through the thermal exfoliation process and its photocatalytic activity towards pollutant degradation and hydrogen evolution. [ABSTRACT FROM AUTHOR]

Transition metal phosphides (TMPs), as an environmentally friendly non-noble metal cocatalyst, play a key role in promoting photocatalytic hydrogen evolution. In this work, three metal phosphating compounds (NiCoP, Ni2P, and Co2P) were synthesized by solvothermal method using red phosphorus as a phosphorus source. The three kinds of co-catalysts were individually loaded onto Zn0.5Cd0.5S by physical agitation method to form binary nanocomposites (ZnCdS/TMPs). The results showed that the three composite photocatalysts all showed excellent HER performance in the Na2S/Na2SO3 sacrifice solution. Among them, the hydrogen production rate of ZnCdS/NiCoP-5% reached 64 μmol at 5 h, which was significantly higher than that of pure Zn0.5Cd0.5S, ZnCdS/Ni2P-5%, and ZnCdS/Co2P-5%. According to the results of various characterization techniques, NiCoP nanoparticles provide more active sites for Zn0.5Cd0.5S and the composite photocatalytic materials exhibit excellent hydrogen evolution performance. Moreover, the Schottky barrier between Zn0.5Cd0.5S and NiCoP nanoparticles effectively enhances the charge separation rate, thus promoting the improvement of photocatalytic hydrogen evolution. Therefore, low-cost transition metal phosphide as a cocatalyst has broad prospects in the field of photocatalysis. [ABSTRACT FROM AUTHOR]

A heterojunction structure LaVO4/g-C3N4 composite with oxygen defects was successfully prepared. The characterization results show that the recombination of electron–hole pairs could be inhibited by the heterojunction structure. The LaVO4/g-C3N4 composite shows superior photocatalytic water splitting performance for the generation of hydrogen and oxygen under visible light irradiation. Experimental data show that under visible light irradiation, the hydrogen and oxygen evolution rates of the LVOCN1 composite are much higher than those of fresh carbon nitride. Moreover, the photocatalytic activity of LaVO4/g-C3N4 composites could be significantly enhanced by O defects. Mechanism studies display that the possible mechanism of the photocatalytic water splitting reaction is the Z scheme mechanism. [ABSTRACT FROM AUTHOR]

CdS/Ag2S/g-C3N4 ternary composites as photocatalysts with different amounts of Ag2S were successfully synthesized through a simple chemical deposition method. These photocatalysts were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) mapping and X-ray photoelectron spectroscopy (XPS) to obtain the information of the structure and composition. Compared with the pure samples and binary composites, CdS/Ag2S/g-C3N4 ternary composites showed enhanced hydrogen production activities, and the maximum hydrogen production rate of CdS/Ag2S(2%)/CN is about 1020.54 μmol g−1 h−1 in Na2S–Na2SO3 solution. Based on the photoluminescence and electrochemical results, the improved photocatalytic activity could be attributed not only to the synergic effect of ternary components in the composite, but also to the introduction of Ag2S that provided abundant active sites for H2 production. A possible mechanism was investigated in detail. [ABSTRACT FROM AUTHOR]

Typical non-metallic semiconductor carbon nitride (CN) has enormous potential in the field of photocatalysis, but the easy recombination of the photo-generated charges severely limits its practical applications. Herein, oxygen-doped and nitrogen vacancy co-modified carbon nitride (ODCN) was prepared by simple reduction and oxidation treatments. The experimental results show that the modified CN can effectively enhance the photocatalytic activity, indicating that there is a synergy between oxygen doping and nitrogen vacancy. The photocatalytic hydrogen generation rate of ODCN is 364 μmol g−1 h−1, which is higher than that of bulk CN, nitrogen vacancy-modified carbon nitride (DCN) and oxygen-doped modified carbon nitride (OCN). As a consequence, our work provides a neoteric idea for the co-modification of carbon nitride by a variety of methods, which can significantly improve the photocatalytic activity of carbon nitride and is expected to be applied in practical applications. [ABSTRACT FROM AUTHOR]

Photocatalysis is deemed as an appealing strategy to exploit solar energy for simultaneous fuel production and pollutant utilisation. However, current photocatalytic systems rarely couple both processes and commonly suffer from restricted scalability and sustainability as they use toxic or ultraviolet light harvesters, combined with noble-metal co-catalysts under corrosive conditions. Here, we show the synthesis of ultra-scalable and low-cost carbon nanodots from lignocellulosic waste, which when combined with a non-precious Ni-based co-catalyst, use visible light to drive H2 production in untreated river and sea water. Organic pollutants and chloride anions in these untreated media do not only allow unhindered photocatalytic activities, but also function as electron donors for the photoexcited carbon dots to enable proton reduction. This system combines Earth's most abundant resources (biomass, solar energy, untreated water) and functions at ambient temperature, pressure and benign pH, thereby creating perspectives for simultaneous fuel synthesis as well as sustainable and practical pollutant utilisation. [ABSTRACT FROM AUTHOR]

Considerable efforts have been directed towards constructing high-efficiency, earth-abundant and low-cost photocatalysts for hydrogen evolution under visible light irradiation. In this work, 2D ultrathin CoP-decorated bimetallic MnxCd1−xS photocatalysts were developed based on the combined strategies of controllable band structure and co-catalyst modification. An optimal H2 production rate of 65 324 μmol g−1 h−1 was obtained for the Mn0.5Cd0.5S/CoP-4% sample under visible light irradiation, which was 4.26 times higher than that of pure Mn0.5Cd0.5S as well as 38.7 times that of pure CdS. UV-vis and MS characterization results showed that the introduction of Mn into CdS could change the band potential towards a more negative direction, which would be beneficial for water reduction. Moreover, the added CoP could act as a co-catalyst to facilitate the electron transfer and restrain the recombination of photogenerated electron–hole pairs, which was testified by photocurrent, PL and EIS analyses. This work paves the way to offer a new direction towards designing efficient photocatalysts for hydrogen evolution. [ABSTRACT FROM AUTHOR]

Nanostructured semiconductor photocatalysts with high specific surface areas and unique structures are expected with high performance for the photo-degradation of organic pollutants. In this work, novel pine-branch-like ternary CuO/CuS/ZnO heterostructure catalysts have been designed and successfully synthesized on a Cu foam substrate. Effective electron–hole separation, improved visible light utilization and efficient light harvesting by novel pine-branch-like heterostructures have been realized. The photocatalytic rate constant of a pine-branch-like CuO/CuS/ZnO heterostructure is 0.0156 min−1, which is 2 times that of CuO/CuS (0.0078 min−1) and 4.6 times that of CuO nanowires (0.0034 min−1) in the degradation of RhB solution. The enhanced catalytic ability of the CuO/CuS/ZnO heterostructure is attributed to the unique heterostructure, which effectively enhances the absorption of sunlight and reduces the charge-carrier recombination. The stability and high efficiency of the novel cost-effective, non-toxic and easily-recyclable catalytic system can be extended to the photocatalytic field and solar water splitting for hydrogen generation. [ABSTRACT FROM AUTHOR]

Tantalate semiconductors are potential photocatalysts for hydrogen generation via photocatalytic water splitting reaction because the conduction band of tantalates is composed of the tantalum 5d orbital, which is located at a more negative potential than that of the H+/H2 half reaction, i.e., 0.0 V vs. NHE. Bi3TaO7 is a stable tantalate under acidic or alkaline conditions, with a band gap suitable for visible light absorption. However, the photocatalytic properties of Bi3TaO7 are only reported based on the dye degradation reactions, probably due to the fast electron/hole recombination losses. 2D crystal-like nanosheets with a thickness of a few nanometers show unique features such as high carrier mobility, the quantum Hall effect, high specific surface area, and excellent electrical/thermal conductivity. 2D structures can also enhance the photocatalytic properties because photo-generated charge carriers in nanosheets are less prone to fast recombinations as compared to their bulk counterparts. In this study, nanosheets of Bi3TaO7 are produced by a liquid exfoliation method and the photocatalytic hydrogen generation reaction is investigated for both the as-synthesized Bi3TaO7 nanoparticles and Bi3TaO7 nanosheets. [ABSTRACT FROM AUTHOR]

Improving the efficiency of charge separation is an important aspect in photocatalysis. In this work, the hybrid nanostructure of α-Ni(OH)2/Zn0.5Cd0.5S has been prepared by a simple two-step method for the first time. Here, designed/constructed with α-Ni(OH)2 over Zn–Cd–S, the catalyst efficiently boosts hydrogen evolution in photocatalytic hydrogen production. With a 25% content of α-Ni(OH)2 in the ZSN25 composite under visible light (λ≥ 420 nm) irradiation, remarkable hydrogen production of 22.45 mmol g−1 h−1 has been achieved. In addition, we found that the activities could be improved by means of controlling the formation of α-Ni(OH)2 species. The reason is that the interface between α-Ni(OH)2 and Zn0.5Cd0.5S provides a fast charge transfer channel to reduce the recombination of photogenerated carrier. Also, the formation of this interface is largely related to the content of α-Ni(OH)2. The Tafel slope, EIS and PL spectra support enhanced photocatalytic energy in the α-Ni(OH)2/Zn0.5Cd0.5S charge transfer state and faster hydrogen evolution kinetics. These nanocomposites of Zn0.5Cd0.5S modified by α-Ni(OH)2 are of great significance for renewable hydrogen generation technology. [ABSTRACT FROM AUTHOR]

Self-doping by Ti3+ is a useful method to expand the light response of TiO2 into the visible light region. However, to obtain a stable Ti3+-doped TiO2 seems to be a challenge due to the easy oxidation of Ti3+ during the heterogeneous reaction. Here, we propose a simple carbon coating route to stabilize the Ti3+-doped TiO2, in which both the Ti3+ and precursor of the carbon coating layer were in situ formed from the hydrothermal hydrolysis of titanium isopropoxide. The carbon coated Ti3+-doped TiO2 exhibited excellent stability for photocatalytic hydrogen production. Based on electron paramagnetic resonance (EPR) analysis, the proposed stabilizing mechanism is that the conductive carbon coating layer as a barrier layer prevents the H2O and O2 from diffusing into the surface of the photocatalyst, which can oxidize the surface O vacancies and Ti3+ in TiO2. Our findings offer a simple route to prepare a highly stable TiO2-based photocatalyst with visible light response. [ABSTRACT FROM AUTHOR]