Photocatalytic H2 Evolution Performance Research Articles

Enhanced Photocatalytic Hydrogen Evolution of In2S3 by Decorating In2O3 with Rich Oxygen Vacancies.

The hydrogen (H2) evolution rates of photocatalysts suffer from weak oxidation and reduction ability and low photogenerated charge carrier separation efficiency. Herein, by combining band-gap structure optimization and vacancy modulation through a one-step hydrothermal method, In2O3 containing oxygen vacancy (Ov/In2O3) is simply introduced into In2S3 to promote photocatalytic hydrogen evolution. Specifically, the change in the sulfur source ratio can induce the coexistence of Ov/In2O3 and In2S3 in a high-temperature hydrothermal process. Under light irradiation, In2S3@Ov/In2O3-0.1 nanosheets hold a remarkable average H2 evolution rate up to 4.04 mmol g-1 h-1, which is 32.14, 11.91, and 2.25-fold better than those of pristine In2S3, In2S3@Ov/In2O3-0.02, and In2S3@Ov/In2O3-0.25 nanosheets, respectively. The ultraviolet-visible (UV-vis) diffuse reflectance and photoluminescence (PL) spectra reveal that the formation of Ov/In2O3 in In2S3 optimizes the band-gap structure and accelerates the migration of the photogenerated charge carrier of In2S3@Ov/In2O3-x nanosheets, respectively. Both the enhancement of oxidation and reduction ability and photogenerated charge carrier separation ability are responsible for the remarkable improvement in photocatalytic H2 evolution performance. This work provides a new strategy to prepare a composite of metal sulfide and metal oxide through a one-step hydrothermal method.

Surface cyano groups optimize the charge transfer of poly heptazine imide for enhanced photocatalytic H2 evolution

Surface functionalization has been considered as an effective strategy to manipulate charge separation of carbon nitride and therefore to largely improve the photocatalytic H2 evolution efficiency. Poly heptazine imide (PHI) is a new class of crystalline carbon nitride frameworks that exhibits remarkable photocatalytic performance for hydrogen evolution. To further improve the H2 evolution performance of PHI and explore the reaction mechanism, ammonium thiocyanate was used as a precursor for the synthesis of poly heptazine imide at elevated temperatures under molten salt conditions. The optimized PHI with an abundance of surface cyano groups shows a significantly enhanced photocatalytic performance for H2 evolution, which is 4.3 times that on pristine PCN. Most importantly, the surface cyano group adjusts the electron intensity of the polymeric framework, enhances the light absorbance, reduces the bandgap, and improves the charge separation efficiency. The synthetic technique also could be applied to other sulfur-containing precursors for the synthesis of PHI frameworks with excellent hydrogen evolution production performance.

1T/2H MoSe2 modified ZnIn2S4 with modulating internal electric field to boost efficient performance of photocatalytic H2 evolution and epoxide alcoholysis

Herein, the extended layer spacing 1T MoSe2 coupled with ZnIn2S4 nanosheets through in-situ growth, and ultimately obtained 1T /2H MoSe2/ZnIn2S4 photocatalysts with S-scheme heterojunction. This rational structure enables photogenerated carriers to rapidly transfer to MoSe2 via Mo-S bond. In order to further address the problem of wasted oxidative half-reaction, we rely on the dehydrogenation of benzyl alcohol as a carrier for hole depletion. Notably, optimized 1T/2H MoSe2/ZnIn2S4 has superior H2 evolution ability, reaching up to 11.271 mmol·g−1·h−1 and the apparent quantum efficiency at 420 nm is 10.3 %. Meanwhile, the conversion rate of benzyl alcohol to high value-added benzaldehyde is 60.60 %. In addition, the Zn acidic sites can achieve polarization of epoxides and precise cleavage C-O bond. Thus, it also has the ability to high selectivity and efficient photocatalytic epoxide alcoholysis. This work proposes a new insight for enhancing photocatalytic properties via regulating IEF to fabricate S-scheme heterostructure.

High-performance heterometallic photocatalysts afforded by polyoxometalate synthons for efficient H2 production

MoS2-based materials have emerged as photoelectric semiconductors characterized by a narrow band gap, high capacity for absorbing visible light, and reduced H2 adsorption energy comparable to Pt. These attributes render them appealing for application in photocatalytic hydrogen production. Despite these advantages, the widespread adoption of MoS2-based materials remains hindered by challenges associated with limited exposure to active sites and suboptimal catalytic hydrogen production efficiency. To address these issues, we have designed and synthesized a new class of highly dispersed bimetallic/trimetallic sulfide materials. This was achieved by developing polyoxometalate synthons containing Ni-Mo elements, which were subsequently reacted with thiourea and CdS. The resulting Ni3S2-MoS2 and Ni3S2-MoS2-CdS materials achieve photocatalytic hydrogen production rates of 2770 and 2873 μmol g–1h−1, respectively. Notably, the rate of 2873 μmol g–1h−1 for Ni3S2-MoS2-CdS surpassed triple (3.23 times) the performance of CdS and nearly sextuple (5.77 times) that of single MoS2. These materials outperformed the majority of MoS2-based photocatalysts. Overall, this study introduces a straightforward methodology for synthesizing bimetallic/trimetallic sulfides with enhanced photocatalytic H2 evolution performance. Our findings underscore the potential of transition metal sulfide semiconductors in the realm of photocatalysis and pave the way for the development of more sustainable energy production systems.

Oxygen vacancy-rich CoMoO4/Carbon nitride S-scheme heterojunction for boosted photocatalytic H2 production: Microstructure regulation and charge transfer mechanism

Developing highly efficient S-scheme photocatalysts is a subject of immense interest for harnessing solar energy towards sustainable hydrogen production. Herein, a novel S-scheme heterojunction of oxygen vacancy-rich CoMoO4/CN (CMO/CN) photocatalyst was rationally constructed through loading CoMoO4 nanorods on carbon nitride (CN) nanosheets via a direct one-pot calcination method. The CMO/CN S-scheme heterojunction exhibited enhanced surface area, fine CN dispersion, rich oxygen vacancies, and accelerated charge separation/transfer efficiency, which were conducive to improving photocatalytic H2 evolution performance. Of note, the optimal 3 %CMO/CN sample displayed the highest H2 production rate of 8.35 mmol g−1 h−1, which is 4.6 folds that of pristine CN. In situ irradiated X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) characterizations confirmed the S-scheme charge transfer path between CN and CMO, which greatly promoted spatial charge separation. Density functional theory (DFT) calculations together with contact angle tests revealed the reduced activation energies for H2O dissociation and enhanced hydrophilicity of the CMO/CN. The CMO/CN photocatalysts also presented high stability and fine reusability. This work may provide insights into the combination of defect engineering and heterojunction designing for high-efficiency solar-to-chemical energy conversion.

Synergizing copolymerization and thermal induction for carbon nitride: Reinforcing photocatalytic performance and mechanism insight

Structure optimization of photocatalyst graphitic carbon nitride (CN) is still a key endeavor. CN nanosheets were prepared via a facile one-pot copolymerization process, incorporating electron-withdrawing groups 5-cyanopyrimidine (CPM) and melamine under calcination. The synergistic effect of molecular doping and thermal induction effectively modulates the intrinsic electronic and band structure of CN. The post-optimized sample (CNMCPM0.03–700) exhibits a higher reduction potential, reduced nanosheet thickness, stronger crystallinity, and enhanced electron-holes separation efficiency, compared to pristine CN (CNM). Notably, significant morphological and textural alterations were observed in the modified CNMCPMX-T samples. Consequently, a remarkable enhancement in visible-light photocatalytic H2 evolution and CO2 reduction performance was achieved. Specifically, the CNMCPM0.03–700 retained an H2 evolution rate of 166.4 µmol·h−1, which was 14.8-fold higher than that of CNM (11.3 µmol·h−1), along with a 31.6-fold increase in CO evolution efficiency. Molecular and textural engineering demonstrate their universal applicability for different comonomers. This study showcases the feasibility of synergizing thermal induction and copolymerization strategies for synthesizing high-efficiency CN-based photocatalysts with unique topology and structural precision.

Construction of 1D/3D Co9S8/Mn0.3Cd0.7S Schottky heterojunction for dramatically boosted photocatalytic H2 evolution performance

One of the most crucial strategies for transforming solar energy into sustainable hydrogen energy is photocatalytic H2 evolution, and constructing an effective and durable photocatalyst remains a difficult task. Herein, a 1D/3D Co9S8/Mn0.3Cd0.7S Schottky heterojunctions were successfully fabricated by three-step hydrothermal procedure, in which 3D Mn0.3Cd0.7S solid solution particles were immobilized on the 1D tube-like Co9S8 surface, allowing for extremely effective charge separation and transfer. Through coupling Co9S8 with Mn0.3Cd0.7S, the photocatalytic H2 evolution activity and stability were significantly boosted. The 7 % Co9S8/Mn0.3Cd0.7S heterojunction possessed the highest photocatalytic activity with the H2 evolution rate of 1586.4 μmol⋅h−1, which was 3.73 times larger than that of pristine Mn0.3Cd0.7S, corresponding to 21.8 % apparent quantum efficiency (AQE) at 420 nm monochromatic light. The Schottky heterojunction mechanism between Co9S8 and Mn0.3Cd0.7S could plausibly explain the enhanced photocatalytic H2 evolution performance, according to density functional theory (DFT) calculations and ultraviolet photoelectron spectroscopy (UPS) measurements. This investigation would offer the useful insights to develop Co9S8 cocatalyst for application in photocatalytic H2 evolution.

Enhanced performance of a Na3.5Co4[Bi2Co2W19.75O70(H2O)6]/porous graphitic carbon nitride heterojunction based photocatalyst realized by the addition of copper sulfide nanoparticles.

Photocatalytic hydrogen (H2) evolution can effectively solve the global energy problem, in which the key factor is the synthesis of efficient photocatalytic materials. In this study, we successfully synthesized a novel photocatalyst, BiWCo/CuS/PGCN, by functionalizing porous graphitic carbon nitride (PGCN) with sandwich-type polyoxometalate Na3.5Co4[Bi2Co2W19.75O70(H2O)6]·39.5H2O (BiWCo) and introducing copper sulfide (CuS) nanoparticles as a cocatalyst. This approach was aimed at enhancing the built inner electric field between interfaces, resulting in a significant improvement in photocatalytic H2 evolution performance. This research adopts a step-by-step method to synthesize BiWCo/CuS/PGCN composites with p-n heterojunctions, which has high visible light absorption and a synergistic effect of multiple elements. PGCN with a high specific surface area contributes to the uniform distribution of active sites. In addition, the nano-CuS cocatalyst provides abundant active sites and more electron transfer pathways for photocatalysis. Therefore, the H2 production efficiency of BiWCo/CuS/PGCN is 6.3 times that of PGCN, 4.5 times that of BiWCo and 2.5 times that of BiWCo/PGCN under visible light. The H2 production rate of BiWCo/CuS/PGCN reaches 3477.58 μmol g-1 h-1. At the same time, the ternary photocatalyst shows high stability after 30 hours and 5 cycles. This work demonstrates that BiWCo/CuS/PGCN has good application prospects in H2 evolution, and provides a new strategy for the design of efficient ternary photocatalytic materials.

Critical role of hydrogen bonding between microcrystalline cellulose and g-C3N4 enables highly efficient photocatalysis.

Developing a highly efficient photocatalyst for energy and environmental applications is urgently required. Herein, graphitic carbon nitride (CN) coupled with microcrystalline cellulose (MCC) (denoted as MCC-X/CN) shows excellent photocatalytic performance for tetracycline (TC) degradation and H2 evolution. And the optimized MCC-0.05/CN shows an improved TC degradation rate (Kapp = 0.019 min-1) and H2 evolution rate (642.71 μmol g-1 h-1), which are 1.9 and 22 times higher than those of pure CN, respectively. This improvement primarily results from hydrogen bonding (H-bonding) between CN and MCC, which enables excellent charge separation and migration, leading to the outstanding photoelectrochemical properties of MCC-0.05/CN.

Fabrication of visible-light-responsive ZnIn2S4 nanosheets wrapped onto MIL-125(Ti) hybrid structure with improved photocatalytic H2-evolution performance

Fabrication of visible-light-responsive ZnIn2S4 nanosheets wrapped onto MIL-125(Ti) hybrid structure with improved photocatalytic H2-evolution performance

Efficient spatial separation of charge carriers over Sv-ZnIn2S4/NH2-MIL-88B(Fe) S-scheme heterojunctions for enhanced photocatalytic H2 evolution and antibiotics removal performance

The exploration of highly efficient sunlight-assisted photocatalyst for photodegradation of organic contaminants or energy conversion is strongly encouraged. In this work, we designed a novel three-dimensional spindle-like Sv-ZIS@NMFe heterojunction made of amino functionalized NH2-MIL-88B(Fe) (NMFe) and ZnIn2S4 nanosheets with abundant sulfur vacancies (Sv-ZIS). The structural properties of NMFe materials, such as a clearly defined system of pores and cavities, were retained by the Sv-ZIS@NMFe composites. Additionally, the incorporation of sulfur vacancies, –NH2 functional groups, and well-matched energy level positions led to various synergistic effects that considerably enhanced internal electron transformation and migration, as well as improved adsorption performance. Consequently, under visible light irradiation, the optimized sample exhibited superior hydrogen production activity and tetracycline hydrochloride photodegradation performance. At last, density functional theory calculations was used to further elucidated the possible photoreactivity mechanism. This study demonstrates that the Sv-ZIS@NMFe heterojunction materials formed by ZnIn2S4 with suitable sulfur vacancies and amino functionalized Fe-MOFs have promising applications in photocatalysis.

Piezoelectric effect achieves efficient carriers’ spatial separation and enhanced photocatalytic H2 evolution of UiO-66-NH2@CdS by transforming charge transfer mechanism

The internal electric field induced by piezoelectric effect can optimize the transport pathway of photogenerated charge in photocatalysis. We constructed an effcient piezoelectric photocatalytic heterojunction UiO-66-NH2@CdS and achieved a shift in the charge transfer mechanism through the piezoelectric effect, resulting in excellent photocatalytic H2 evolution performance. The optimal heterojunction under the ultrasonic environment exhibited 2028.48 μmol·g−1·h−1 photocatalytic H2 evolution performance, roughly four times better than no-ultrasound condition. Because of the piezoelectric polarization of UiO-66-NH2, the photogenerated carrier transport mechanism was changed from type Ⅱ to the more favorable Z-scheme for charge separation. Meanwhile, the built-in electric field caused by the piezoelectric effect can act as a powerful driving force for charge separation, achieving high charge separation efficiency and promoting the utilization of photogenerated electrons. This work would provide a fresh perspective for MOF-based piezoelectric photocatalysts and have implications for the design of efficient Z-scheme heterojunctions.

Role of H-beta zeolite on photocatalytic pollutant degradation and H2 production enhancement of g-C3N4/H-Beta composite

Limited by low surface area and insufficient photoelectric conversion efficiency, bulk g-C3N4 showed unsatisfactory photocatalytic pollutant degradation and H2 evolution performance. Herein, hydrophilic and porous H-Beta zeolite was employed to prepare g-C3N4/H-Beta composite via facile in-situ polymerization method. The role of H-Beta zeolite manifested in increased surface area, improved hydrophilicity and facilitated separation and transportation of photoexcited charge carriers. Hence, the obtained g-C3N4/H-Beta photocatalyst with an optimal content of H-Beta zeolite showed highest photocatalytic pollutant degradation efficiency and H2 generation rate, which were 7.31- and 6.32-fold greater than that of bulk g-C3N4.

Facile Construction of 2D/2D ZnIn2S4-Based Bifunctional Photocatalysts for H2 Production and Simultaneous Degradation of Rhodamine B and Tetracycline.

A two-dimensional/two-dimensional (2D/2D) TiO2/ZnIn2S4 photocatalyst was reasonably proposed and constructed by a two-step oil bath-hydrothermal method. TiO2 nanosheets uniformly grown on the surface of ZnIn2S4 nanosheets and a synergetic effect between the TiO2 and ZnIn2S4 could highly contribute to improving the specific surface area and hydrophilicity of ZnIn2S4 as well as accelerating the separation and transfer of photon-generated e--h+ pairs, and thus enhancing the visible-light photocatalytic degradation and H2 evolution performance of ZnIn2S4. Rhodamine B (RhB) and tetracycline (TC) were simultaneously selected as the target pollutants for degradation in the work. The optimum photocatalytic RhB and TC degradation properties of TiO2/ZnIn2S4-10 wt% were almost 3.11- and 8.61-fold higher than that of pure ZnIn2S4, separately, while the highest photocatalytic hydrogen evolution rate was also observed in the presence of TiO2/ZnIn2S4-10wt% and 4.28-fold higher than that of ZnIn2S4. Moreover, the possible photocatalytic mechanisms for enhanced visible-light photocatalytic degradation and H2 evolution were investigated and proposed in detail. Our research results open an easy pathway for developing efficient bifunctional photocatalysts.

Enhanced photocatalytic hydrogen evolution over Ce–TiO2/graphite/g-C3N4 ternary S-scheme heterojunction

Efficient charge separation is of great significance for achieving high-efficient photocatalytic H2 evolution (PHE) performance. However, charge separation remains a big challenge owing to serious charge recombination in a single photocatalyst material. In this study, we engineered a composited material composed of one-dimensional (1D) cerium (Ce)-doped TiO2/graphite/g-C3N4 (TC/GR/CN) S-scheme ternary heterojunction by using an in-situ tri-coaxial electrospinning method for efficient solar-driven H2 generation. Experimental and theoretical investigations confirmed that the polarization effect of the conductive graphite could strengthen the internal electric field (IEF) to improve the interfacial charge transfer between Ce-doped TiO2 to g-C3N4. The close-contact heterointerfaces and S-scheme charge transfer pathway in the Ce-doped TiO2/graphite/g-C3N4 hybrid could accelerate the separation of photoexcited charge carriers and optimize H* adsorption/desorption properties. Consequently, the Ce-doped TiO2/graphite/g-C3N4 exhibited a superior photocatalytic H2 generation rate of 3.05 mmol·g−1·h−1, which was 38.7 folds higher than those of conventional single g-C3N4 catalyst. This work proposes a facile and controllable electrospinning strategy for designing ideal hydrogen evolution photocatalysts, which may stimulate further studies on developing the advanced catalyst systems.

Carbazole‐Based Donor‐Acceptor Conjugated Microporous Polymers for Efficient Visible‐Light‐Driven Photocatalytic H2 Evolution†

Comprehensive SummaryConjugated microporous polymers (CMPs) featuring extended π‐structures, large specific surface area and tailor‐made functionalities are a class of promising organic photocatalysts for hydrogen evolution reaction (HER) from water. However, the photocatalytic activities of most CMPs are severely hindered by slow charge transfer rate and fast charge recombination process. Herein, we develop a strategy for the synthesis of donor‐acceptor CMPs through nickel(0)‐catalyzed Yamamoto cross‐coupling of 3,6‐dibromo‐9‐(4‐bromophenyl)carbazole (CZ) with 5,5'‐dibromo‐2,2'‐bipyridine (DBPy) for efficient HER from water. The PCZN‐4 prepared with a 2 : 3 stoichiometric ratio of CZ to DBPy exhibited the highest photocatalytic hydrogen evolution rate of 7160 μmol·g–1·h–1, which was nearly equal to 179 times and 143 times that of PCZN‐1 (40 μmol·g–1·h–1) and PCZN‐6 (50 μmol·g–1·h–1) obtained by Yamamoto homocoupling of CZ and DBPy, respectively. Compared to the homocoupling counterparts, the enhanced photocatalytic activity of PCZN‐4 results from improved separation efficiency of charge carriers. Interestingly, the photocatalytic H2 evolution performance of PCZN‐4 could be further improved up to 17080 μmol·g–1·h–1 by adjusting pH of the aqueous solution. This work offers a novel approach for improving photocatalytic efficiency by tuning the chemical structures and surrounding microenvironment of the polymer backbone.

Al–SrTiO3/Au/CdS Z-schemes for the efficient photocatalytic H2 production under visible light

Development of sustainable solar fuels to meet the continued increase in the energy need worldwide is of particular importance. In addition, reducing carbon emissions could be the last hope to solve global challenges such as global warming and climate change. For this endeavor, different Al–SrTiO 3/Au/CdS Z-Scheme samples were developed by changing the weight percentage (wt. %) of gold nanoparticles (Au NPs) and the wt% ratio of Al–SrTiO3 to CdS NPs using post annealing of mixed powders method. The prepared samples were characterized using several physicochemical techniques to reveal their properties, then their photocatalytic H2 evolution performance was evaluated under visible light using photodeposited RhCr2O3 as H2 evolution cocatalyst. Our results showed that, Al–SrTiO3 particles possessed high crystallinity and cubic perovskite phase, Au NPs exhibited face-centered cubic (FCC) structure, and CdS NPs had cubic Zinc Blende phase as confirmed by XRD analysis. Our UV–Vis. diffuse reflectance analysis revealed that all prepared Z-scheme samples obtained a strong absorption in both UV and visible regions. SEM analysis confirmed the cubic morphology of the perovskite Al–SrTiO3 particles which were randomly deposited by Au NPs of relatively smaller size. While CdS NPs showed semi-spherical shape and were conjugated with Al–SrTiO3 directly to form the proposed Z-Schemes as proposed by our STEM mapping analysis. The highest amount of H2 (656.7 μ mole) was evolved by Al–SrTiO3/4 wt% Au/CdS (1:1) Z-scheme sample after 3 h of visible light irradiation. This sample had 4 wt % of Au NPs and equimolar ratio of Al–SrTiO3 and CdS NPs. This relatively higher activity might be because of the efficient light absorption, prolonged lifetime of the photogenerated charge carriers and improved charge separation as revealed by the PL analysis. Our study can promote the ongoing efforts toward more carbon neutral societies.

Hydrochloric‐acid‐induced hydrothermally pretreated ultrathin C3N4 nanosheets for efficient photocatalytic H2 evolution

AbstractBACKGROUNDC3N4 nanosheets with a layered structure have attracted significant interest in the field of photocatalysis. However, direct preparation of these nanosheets remains a significant challenge.RESULTSIn this study, highly active C3N4 nanosheets were fabricated via the direct thermal polymerization of melamine supramolecular aggregates obtained using hydrochloric‐acid‐induced hydrothermal pretreatment. Various methods were adopted to characterize the photocatalytic materials obtained and density functional theory calculations were performed to understand the highly efficient nature of C3N4. The structures and photochemistry of the photocatalytic materials depend on the hydrochloric‐acid‐induced hydrothermal pretreatment method. It was found that C3N4‐180‐H nanosheets have numerous (C)2N–H that are conducive to photogenerated electron–hole separation. In addition, the C3N4‐180‐H nanosheets have a large surface area and a short charge‐carrier diffusion distance. Furthermore, the C3N4‐180‐H nanosheets exhibited a longer excitation‐state charge‐carrier lifetime than bulk C3N4. The as‐prepared C3N4‐180‐H nanosheets with unique structural advantages showed superior photocatalytic H2 evolution performance (413 μmol h−1 g−1) compared to that of bulk C3N4 (90.5 μmol h−1 g−1).CONCLUSIONThis study offers a feasible and simple method for synthesizing C3N4 nanosheets and developing an excellent 2D photocatalyst for superior solar‐to‐H2 production. © 2023 Society of Chemical Industry (SCI).

Construction of S-scheme CdS/g-C3N4 heterojunctions with enhanced photocatalytic H2 evolution and Cr(VI) reduction performance

Construction of heterojunctions is one of the most attractive approaches to synthesize highly active photocatalysts. In this work, we prepared CdS/g-C3N4 (CSCN) heterojunctions with different molar ratio of CdS/g-C3N4 via ball milling for photocatalytic hydrogen production and removal of Cr(VI). The successful construction of CSCN heterojunctions was proved by the various characterization methods. Formation of CSCN heterojunctions not only generates more vacancies to act as active site, but also accelerates the separation of photoinduced charge carriers, endowing with more electrons to participate in the photocatalytic reduction reaction. 2%CSCN sample was confirmed to hold the highest separation and transfer performance of photoinduced e−/h+ pairs by photoelectric tests. 2%CSCN samples exhibit the highest photocatalytic H2 evolution rate (680.04 μmol/g/h), which is 3.63-fold higher than that of the bare g-C3N4 (146.83 μmol/g/h). The activity of photocatalyst was further examined by removal of Cr(VI) experiment. The results show that the reduction efficiency of Cr(VI) on 2%CSCN is 2.46-fold of that of on the single g-C3N4, and the elimination rate of Cr(VI) on 2%CSCN can reach 64% after 1 h under simulated sunlight illumination. The improved photocatalytic performance can be ascribed to the creation of appropriate C vacancies and the widened light absorption range induced by CdS. A rational mechanism for enhanced photocatalytic activity was proposed to further understand the separation and transfer of photogenerated carriers produced by heterojunctions.

Construction of novel NH2-MIL-125(Ti)@ZnIn2S4 Z-scheme heterojunction and its photocatalytic performance regulation

In this work, a series of ZnIn2S4 nanosheets encapsulated NH2-MIL-125(Ti) heterostructures (NM-125(Ti)@ZIS) have been rationally designed and established through a facile oil bath method. The photocatalytic Cr(VI) reduction and H2 evolution performance on NM-125(Ti)@ZIS were elaborately modulated by adjusting the mass ratio of two components, introducing S vacancy and loading cocatalysts. The experimental results demonstrate that the optimized NM-125(Ti)@ZIS heterostructure with mass ratio 3:1 of NM-125(Ti) to ZIS has an excellent Cr(VI) reduction performance in neutral solution, giving 98% reduction efficiency within 60 min. Moreover, the NM-125(Ti)@ZIS heterostructure, following the introduction of sulfur vacancies and the incorporation of Pt nanoclusters, demonstrates an optimal visible light (λ > 420 nm) hydrogen evolution rate of 4.708 mmol/g/h, which is 5.82 times greater than that of pristine ZIS. A thorough investigation of the microstructures and photoelectrochemical properties of the NM-125(Ti)@ZIS heterostructures reveals that the intimate contact interface, sulfur vacancy, and Pt nanocluster serve to effectively enhance charge separation efficiency, thereby improving the photocatalytic performance. Further analysis on the charges behavior at the interface verifies that a novel Z-scheme heterojunction has been constructed between ZnIn2S4 and NH2-MIL-125(Ti).