Photocatalytic H2 Production Rate Research Articles

Nanostructured defects-rich black-ZnO/biowaste-derived carbon composites for efficient visible light-driven hydrogen generation: A study on the role of C–Zn@C–O–Zn interface

The use of a highly efficient and noble-metal-free cocatalyst, which is being pursued to create hydrogen (H2) via photocatalysis, has been the subject of many studies. In this work, a unique ultrasonication-assisted laser beam irradiation process is employed to synthesize a new carbon material generated from pineapple peel biowaste (ppC) and mix it with oxygen-deficient black zinc oxide (b-ZnOvac) nanoparticles. In the ppCx@b-ZnOvac nanostructures, the XPS analysis verified the presence of surface oxygen (O2) defects and vacancies as well as chemical interactions between carbon and zinc via carbon-zinc (C–Zn) and carbon-oxygen-zinc (C–O–Zn) connection interfaces. Following optimization, the visible light active photocatalytic H2 production rate of the ppC10@b-ZnOvac nanostructures reached 215.92 μmol h−1 g−1, which was the highest. The positive synergistic interaction between b-ZnOvac and ppC is responsible for the significant increase in the rate of H2 generation. Furthermore, the significant chemical bond between ppC and b-ZnOvac via the C–Zn/C–O–Zn interface, as well as the development of surface O2 vacancy defects in b-ZnOvac, improve the efficient transfer of energetic electrons and make visible active photocatalytic H2 production from methanol in the ppCx@b-ZnOvac nanostructures easier. Our work presents a new strategy for chemically generating affordable carbon materials through the use of metal oxide-based photocatalysts with surface O2 vacancy defects and bio-waste. Applications such as water splitting, energy production, and environmental remediation show promise for these advanced materials for large-scale field applications.

A novel hexagonal prism of Zr-based MOF@ZnIn2S4 core−shell nanorod as an efficient photocatalyst for hydrogen evolution

Photocatalytic water splitting is a commonly used pathway for hydrogen (H2) production, and it is crucial to develop highly active ZnIn2S4 (ZIS)-based photocatalytic systems. In recent years, metal-organic frameworks (MOFs) are also of great interest in the fields of energy production and environmental remediation. Therefore, this study primarily focuses on the fabrication of a series of heterojunction hexagonal prism-shaped Zr-based MOF@ZIS core-shell nanorods through a simple solvothermal method, in which ZIS nanosheets are highly distributed on the surface of the Zr-based MOF (NU-1000). The photocatalytic activities of the resulting materials were evaluated under visible light illumination (λ ≥ 400 nm) by combining different contents of NU-1000 with ZIS. The H2 evolution results demonstrate that the optimal content of NU-1000 corresponds to a photocatalytic H2 production rate of 8.53 mmol g−1 h−1, which is 5.3 times higher than that of pure ZIS. The enhanced photocatalytic activity of the NU-1000@ZIS (NUZ) heterojunction can be attributed to the incorporation of the NU-1000, which provides abundant active sites due to its larger specific surface area. Additionally, the well-matched band structure between the NU-1000 and ZIS is beneficial to efficiently transfer and separate the photogenerated charge carriers. Furthermore, the NUZ core-shell nanorods exhibit excellent stability, offering a new approach for the fabrication of composite photocatalysts by combining MOF-based and ZIS in the field of photocatalytic H2 production.

Cu2WS4 with high-exposure {0 0 1} surfaces promotes efficient charge separation in ZnIn2S4

The spatial segmentation of photogenerated carriers is crucial for achieving efficient photocatalytic H2 production (PHP) rates in photocatalyst. Design studies of crystalline catalyst facets and selective morphology control can facilitate the development of catalysts that expose more advantageous active facets. Herein, Cu2WS4/ZnIn2S4 composites are constructed by growing ZnIn2S4 nanosheets in situ on Cu2WS4 with largely exposed {001} surface. Experiments and density functional theory calculations demonstrate that the electrons of ZnIn2S4 flowed to the {001} surface of Cu2WS4, and the holes vectorially migrated to the {101} surface, during the reaction process, resulting in efficient spatial separation of the photogenerated carriers. The Cu2WS4/ZnIn2S4 achieves a PHP rate of 23.67 mmol g−1 h−1, 13.44-fold increase compared with pure ZnIn2S4. This report combines the advantages of the high-energy activity of the Cu2WS4 {001} surface to morphologically control the ratio of the {001}/{101} surfaces so that ZnIn2S4 can contact a larger area of the {001} surface. Furthermore, under the influence of crystallographic effects on the {001} and {101} surfaces, electrons and holes of ZnIn2S4 are transferred to different crystalline facets, promoting the redox reaction. This paper provides effective ideas for the rational design of photocatalysts with efficient carrier space separation.

Modulating the Microenvironments of Robust Metal Hydrogen-Bonded Organic Frameworks for Boosting Photocatalytic Hydrogen Evolution.

Hydrogen-bonded organic frameworks (HOFs) are outstanding candidates for photocatalytic hydrogen evolution. However, most of reported HOFs suffer from poor stability and photocatalytic activity in the absence of Pt cocatalyst. Herein, a series of metal HOFs (Co2-HOF-X, X=COOMe, Br, tBu and OMe) have been rationally constructed based on dinuclear cobalt complexes, which exhibit exceptional stability in the presence of strong acid (12 M HCl) and strong base (5 M NaOH) for at least 10 days. More impressively, by varying the -X groups of the dinuclear cobalt complexes, the microenvironment of Co2-HOF-X can be modulated, giving rise to obviously different photocatalytic H2 production rates, following the -X group sequence of -COOMe>-Br>-tBu>-OMe. The optimized Co2-HOF-COOMe shows H2 generation rate up to 12.8 mmol g-1 h-1 in the absence of any additional noble-metal photosensitizers and cocatalysts, which is superior to most reported Pt-assisted photocatalytic systems. Experiments and theoretical calculations reveal that the -X groups grafted on Co2-HOF-X possess different electron-withdrawing ability, thus regulating the electronic structures of Co catalytic centres and proton activation barrier for H2 production, and leading to the distinctly different photocatalytic activity.

Oxygen doping induced intramolecular electron acceptor system in red g-C3N4 nanosheets with remarkably enhanced photocatalytic performance

The enhancement of the photocatalytic activity of graphitic carbon nitride (g-C3N4) depends on the rational design of its visible-light harvesting and charge separation/migration properties. Herein, an oxygen doping-induced intramolecular electron acceptor system enabling n→π* electronic transitions in red g-C3N4 nanosheets (Eg ∼ 1.89 eV) was prepared via copolymerization with nitrilotriacetic acid (NTA) and urea. The n→π* electronic transition can be controllably tuned, thus broadening the absorption spectrum of the system to ∼750 nm. Simultaneously, doping with oxygen which acts as an electron acceptor, accelerates in-plane charge separation and migration. Moreover, this strategy was confirmed experimentally to be scalable for industrial mass production. Experiments and theoretical calculations demonstrated that the oxygen doping could continuously modulate the band gap (from ∼2.65 eV to ∼1.32 eV), resulting in the formation of an intramolecular electron acceptor system which enhances charge separation/migration kinetics. The optimized sample exhibited remarkable photocatalytic H2 and H2O2 production rates of ∼144.8 μmol/h and ∼539.76 μM/h, respectively, which are higher than those for currently available g-C3N4-based photocatalysts. Significantly, the sample exhibited H2 and H2O2 photocatalytic yields ∼37.3 and ∼30.1 times those of pristine g-C3N4 under long-wavelength excitation (λ = 520 nm). This study developed an effective and scalable strategy for the design and synthesis of full-spectrum photocatalysts for a broad range of applications.

Modulating the Microenvironments of Robust Metal Hydrogen‐Bonded Organic Frameworks for Boosting Photocatalytic Hydrogen Evolution

AbstractHydrogen‐bonded organic frameworks (HOFs) are outstanding candidates for photocatalytic hydrogen evolution. However, most of reported HOFs suffer from poor stability and photocatalytic activity in the absence of Pt cocatalyst. Herein, a series of metal HOFs (Co2‐HOF‐X, X=COOMe, Br, tBu and OMe) have been rationally constructed based on dinuclear cobalt complexes, which exhibit exceptional stability in the presence of strong acid (12 M HCl) and strong base (5 M NaOH) for at least 10 days. More impressively, by varying the ‐X groups of the dinuclear cobalt complexes, the microenvironment of Co2‐HOF‐X can be modulated, giving rise to obviously different photocatalytic H2 production rates, following the −X group sequence of −COOMe>−Br>−tBu>−OMe. The optimized Co2‐HOF‐COOMe shows H2 generation rate up to 12.8 mmol g−1 h−1 in the absence of any additional noble‐metal photosensitizers and cocatalysts, which is superior to most reported Pt‐assisted photocatalytic systems. Experiments and theoretical calculations reveal that the −X groups grafted on Co2‐HOF‐X possess different electron‐withdrawing ability, thus regulating the electronic structures of Co catalytic centres and proton activation barrier for H2 production, and leading to the distinctly different photocatalytic activity.

A Schottky/Z-Scheme Hybrid for Augmented Photocatalytic H2 and H2O2 Production.

The prodigious employment of fossil fuels to conquer the global energy demand is becoming a dreadful threat to the human society. This predicament is appealing for a potent photocatalyst that can generate alternate energy sources via solar to chemical energy conversion. With this interest, we have fabricated a ternary heterostructure of Ti3C2 nanosheet modified g-C3N4/Bi2O3 (MCNRBO) Z-scheme photocatalyst through self-assembly process. The morphological analysis clearly evidenced the close interfacial interaction between g-C3N4 nanorod, Bi2O3 and Ti3C2 nanosheets. The oxygen vacancy created on Bi2O3 surface, as suggested by XPS and EPR analysis, supported the Z-scheme heterojunction formation between g-C3N4 nanorod and Bi2O3 nanosheets. The collaborative effect of Z-scheme and Schottky junction significantly reduced charge transfer resistance promoting separation efficiency of excitons as indicated from PL and EIS analysis. The potential of MCNRBO towards photocatalytic application was investigated by H2O2 and H2 evolution reaction. A superior photocatalytic H2O2 and H2 production rate for MCNRBO is observed, which are respectively around 5 and 18 folds higher as compared to pristine CNR nanorod. The present work encourages for the development of a noble, eco-benign and immensely efficient dual heterojunction based photocatalyst, which can acts as saviour of human society from energy crisis.

Constructing GO films/CdS nanoparticles/MoS2 nanosheets ternary nanojunction with enhanced photocatalytic hydrogen evolution activity

CdS, as a visible-light responsible photocatalyst, has gained considerable attentions for its relatively narrow bandgap and negative conduction band edge. However, its photocatalytic activity is hindered by challenges such as severe charge recombination, insufficient active sites and poor stability. In this work, a robust strategy is proposed to optimize the transfer channel for charge carriers and enhance the active sites by heterojunction and cocatalyst engineering. The well-designed GO/CdS/MoS2 shows remarkable durability (20 h without significant loss of H2 production rate) with a high photocatalytic H2 production rate of 1.45 mmol h−1g−1 (about 6.6-fold enhancement compared with CdS) at GO content of 0.1 wt% and MoS2 loading amount of 5.0 wt%. The bolstered H2 production rate is attributed to the augmented transfer channels of mass owing to the holey structure of GO, the enhanced active sites since the introduction of MoS2, and the unidirectional transfer of electrons from CdS to MoS2, which is ascribed to the built-in electric field in the CdS/MoS2 interface. Thanks to the directional transfer of holes from CdS to GO in the GO/CdS interface, the assemblage of holes in CdS is prevented, thus contributing to the amplified stability GO/CdS/MoS2. Our findings offer insights for the enhanced photocatalytic activity of CdS based photocatalysts, which may inspire the development of the heterostructure photocatalysts for solar-to-fuel conversion.

Facile fabrication of S-scheme MnCo2S4/ZnIn2S4 heterojunction for photocatalytic H2 evolution

In this work, MnCo2S4 nano-particle and ZnIn2S4 nano-flower were synthesized via a facile hydrothermal method, respectively. The MnCo2S4/ZnIn2S4 heterojunction was subsequently fabricated using a physical solvent evaporation method. The photocatalytic H2 production rate over 10 wt. % MnCo2S4/ZnIn2S4 can reach 17.5 mmol·g−1·h−1 under the irradiation of a 300 W Xe lamp, with 20 % triethanolamine (TEOA) used as a sacrificial agent, which is 3.4 times and 54.6 times that of pure ZnIn2S4 (5.2 mmol·g−1·h−1) and MnCo2S4 (0.3 mmol·g−1·h−1). The improved performance can be attributed to the establishment of an S-scheme charge transfer pathway between MnCo2S4 and ZnIn2S4, which not only enhances charge separation but also preserves active electrons and holes. The formed heterojunction facilitates the broadening of the light absorption spectrum, enhance carriers generation, reduce charge transfer impedance, increase electrochemical activity surface area, and lower H2 evolution overpotential compared to individual components. The work offers a promising way for the development of stable and efficient sulfide heterojunction achieve efficent photocatalytic H2 evolution.

Dual S-scheme MoS2/ZnIn2S4/Graphene quantum dots ternary heterojunctions for highly efficient photocatalytic hydrogen evolution

The layered chalcogenide ZnIn2S4 (ZIS) exhibits photo-stability and a tunable band gap but is limited in photocatalytic applications, such as hydrogen (H2) production, due to rapid carrier recombination and slow charge separation. To overcome these limitations, we have synthesized a ternary MoS2/ZIS/graphene quantum dots (GQDs) heterojunction, wherein MoS2 and GQDs are strategically attached to ZIS interlaced nanoflakes, enhancing light absorption across the 500–1500 nm range. This heterojunction benefits from dual S-scheme interfaces between MoS2-ZIS and ZIS-GQDs, establishing directed internal electric fields (IEFs). These IEFs accelerate the transfer of photoinduced electrons from the conduction bands of MoS2 and GQDs to the valence band of ZIS, promoting rapid recombination with holes and facilitating efficient catalytic reactions with plentiful photoinduced electrons stemmed from the conduction band of ZIS. As a result, the photocatalytic H2 production rate of the MoS2/ZIS/GQDs heterojunction is measured at 21.63 mmol h−1 g−1, marking an increase of 36.7 times over pure ZIS. This research provides valuable insights into designing novel heterojunctions for improved charge separation and transfer for solar energy conversion applications.

Thienyl-fused dibenzothiophene-S,S-dioxide based conjugated polymer toward highly efficient photocatalytic hydrogen production

Dibenzothiophene-S,S-dioxide (BTDO) is one of the cutting-edge electron-acceptor monomers for designing conjugated polymer based organic materials toward photocatalytic H2 production from water. Normally, structure design of BTDO containing donor-acceptor (D-A) polymer photocatalyst mainly focuses on screening electron-donor motifs, the importance of modification on BTDO molecular toward improving charge carrier separation and photocatalytic performance is always ignored. Herein, a novel thienyl-fused BTDO building block (BTDO-DT) is prepared and utilized to synthesize B-BTDO-DT polymer photocatalyst by Sonogashira-Hagihara cross-coupling polycondensation using 1,4-Diethynylbenzene (B) and BTDO-DT as monomers. Experimental and density functional theory (DFT) calculation results demonstrate that modification of BTDO by thiophene not only enlarges light absorption region and promotes photogenerated e−/h+ separation, but also decreases H atom adsorption free energy (ΔGH*) on oxygen atom in the OSO group. As a result, B-BTDO-DT exhibits an outstanding visible light induced photocatalytic H2 production rate of 156.6 μmol h−1 using 30 mg catalyst without Pt cocatalyst, which is 4.5 times higher than that of B-BTDO. And the H2 production rate of B-BTDO-DT is further improved to be 259.8 μmol h−1 with 2.0 wt% Pt as co-catalyst. The present work may open a new direction for the design of conjugated polymer based photocatalysts with high photocatalytic activities.

Magnetic-field-induced activation of S-scheme heterojunction with core–shell structure for boosted photothermal-assisted photocatalytic H2 production

Photocatalytic H2 production through water splitting using semiconductor photocatalysts offers an economical and efficient approach to generate H2 with minimal environmental pollution to alleviate the energy crisis. Maximizing the utilization of the solar spectrum and essentially accelerating the separation and transfer of photo-generated electrons are crucial for enhancing the activity of the photocatalytic H2 production systems. Herein, Mn3O4@ZnIn2S4 (MO@ZIS) core–shell heterojunction photocatalysts were meticulously designed using a convenient water bath method to obtain a system that can achieve highly efficient photothermal-assisted photocatalytic H2 production induced by a magnetic field (MF). Remarkably, the optimal photocatalytic H2 production rate up to 33.29 mmol h−1 g−1 under the effect of applied MF with an apparent quantum efficiency (AQE) of 19.93 % at 420 nm were obtained over the optimal MO@ZIS-30 photocatalyst. The substantial enhancement of the photocatalytic activity in the MO@ZIS system was attributed to the synergy of magneto-thermal effect induced by the magnetic field and the strong photo-thermal effect exhibited by MO, which significantly increases the heterojunction surface temperature of the photocatalyst and promotes the separation and transfer of photo-induced electron hole pairs, thus accelerating the surface hydrogen evolution dynamics. Furthermore, the S-scheme heterojunction formed between MO and ZIS in MO@ZIS core–shell heterojunction optimizes the carrier transfer path. This study presents an effective approach for the effective utilization of the multi-field synergistic enhancement of photocatalytic activity.

Decorating ZnIn2S4 with earth-abundant Co9S8 and Ni2P dual cocatalysts for boosting photocatalytic hydrogen evolution

Due to the synergistic effect of the rapid transfer of photo-generated electrons and enrichment of reactive active sites, reasonably assembling dual cocatalysts with semiconductor is considered as an excellent method to enhance the photocatalytic properties of semiconductors. Herein, earth-abundant Co9S8 and Ni2P dual cocatalysts modified-ZnIn2S4 (ZIS/CS/NP) composite photocatalyst has been constructed by the low-temperature solvothermal and in-situ photodeposition methods. A series of characterizations indicate the hollow structure of Co9S8 can reduce the charge transfer distance and enhance the migration of photo-generated electrons, while Ni2P acts as an electron collector and provides sufficient active sites for H2 release in this dual cocatalysts system. Because of the synergistic effect of dual cocatalysts, ZIS/CS/NP composites exhibit superior activity in the photocatalytic H2 production compared to blank ZIS, ZIS/CS and ZIS/NP. Notably, the optimal photocatalytic H2 production rate of ZIS/CS/NP reaches 6823.64 μmol g−1 h−1, which is approximately 86 times higher that of blank ZIS. This work is expected to provide useful reference for the construction of high-performance dual-cocatalyst modified semiconductor composite for photocatalytic H2 evolution.

Design and fabrication of a novel 2D/3D ZnIn2S4@Ni1/UiO-66-NH2 heterojunction for highly efficient visible-light photocatalytic H2 evolution coupled with benzyl alcohol valorization

Making full use of photogenerated charge carriers by careful design multifunctional photocatalysts to achieving bi-value-added production with high-efficiency is highly desirable and extremely challenge. Herein, a novel 2D/3D ZnIn2S4@Ni1/UiO-66-NH2 (ZIS@Ni1/UN) heterojunction with spatially separated and precise redox sites was designed and fabricated for both photocatalytic H2 production and benzyl alcohol (BA) valorization. By precise structural regulation and modification of UiO-66 integrated with -NH2, ZnIn2S4 (ZIS) and Ni single-atom, the spatial separation of redox sites and directional electron transfer has been achieved. This realizes collaborative and efficient solar energy to chemical energy conversion. The optimal sample 5ZIS@Ni1/UN-6 shows high photocatalytic H2 and benzaldehyde (BAD) production rates of 11.44 mmol∙g−1∙h−1 and 10.02 mmol∙g−1∙h−1 under visible light. This work highlights the importance of rational construction for the engineering of charge behavior in heterogeneous photocatalysts with spatial separation and identifies their crucial role in promoting the photocatalytic redox coupling reactions.

Selenium doping to improve internal electric field for excellent photocatalytic efficiency of g-C3N4 nanosheets

Graphitic carbon nitride is a promising photocatalyst to address environmental issues and energy applications. Herein, we develop an efficient defect-containing functionalized system of 2D selenium doped g-C3N4 porous nanosheets via one pot with two-step temperature for the first time. During heat treatment, Se-infused g-C3N4 nanosheets loosen stacking and form thinner nanosheets, which could effectively shorten the electronic path of charge migration. The introduction of nitrogen vacancies creates a midgap energy state below the CB, which improves the light-harvesting efficiency. Moreover, the dual effect of N vacancy and Se doping provides a driving force for the dissociation of excitons and achieves an effective spatial charge separation. High specific surface area (104.1 m2/g), suitable bandgap (2.65 eV), and good photocurrent response (0.45 µA cm−2) help to enhance the photocatalytic efficiency of 1-SeCN remarkably. Henceforth, high photocatalytic H2 production rate of 5441 µmol g−1 h−1 and CO evolution rate of 31.5 µmol g−1 h−1 verifies the effective Se doping enhances the photocatalytic efficiency of g-C3N4. Furthermore, DFT calculations are consistent with experimental results and this facile engineering strategy provides a scalable way to develop a novel, efficient g-C3N4-based photocatalyst for H2 production and CO2 reduction.

The enhancement of photocatalytic hydrogen production over Ag2WO4 modified g-C3N4 with Pt as cocatalyst

ABSTRACT The construction of heterojunction photocatalyst is an effective mean to improve the photoexcited electron–hole pair separation. The Ag2WO4-doped graphitic carbon nitride (g-C3N4, C3N4 for short) composite photocatalysts were fabricated by a simple calcination and in-situ depositing strategy. The composites were characterized by different techniques. The effects of Ag2WO4 content, type of scavengers, pH value of reaction solution and dose of scavenger on photocatalytic hydrogen (H2) generation were studied. It was found that the Ag2WO4 micro-nano particles were highly dispersed on the C3N4 surface. After doping Ag2WO4, the light absorption range of Ag2WO4-C3N4 material was broadened effectively from 440 nm to 448 nm, and the BET surface area of C3N4 was increased from 35.63 to 40.73 cm2·g−1, indicating that Ag2WO4 loading could provide some new BET surface areas. The binding energy of all elements in Ag2WO4-4/C3N4 was clearly shifted due to the charge transfer from C3N4 to Ag2WO4, implying a strong interaction between C3N4 and Ag2WO4. The photocatalytic H2 production rate of the optimized Ag2WO4-4/C3N4 was 6047.4 μmol·g−1·h−1, which was 2.04 and 171.8 times that of C3N4 and Ag2WO4, respectively. While Ag2WO4-4/C3N4 exhibited a poor H2 production performance in the absence of Pt co-catalyst (309.3 μmol·g−1·h−1), indicating the formation of heterojunction among Ag2WO4, C3N4 and Pt.

Optimization of Schottky barrier height and LSPR effect by dual defect induced work function changes for efficient solar-driven hydrogen production

Photocatalytic water splitting for hydrogen evolution provides a desired approach for sustainable clean energy. However, increasing the effective electron density for proton reduction remains a huge challenge due to the fast charge recombination kinetic. Herein, we propose an efficient strategy, based on manipulating the Schottky barrier height (SBH) and localized surface plasmonic resonances (LSPR) effect of Co-MoO2-x via dual defect (Co doping and oxygen vacancies) induced work function change, to achieve higher electrons density in plasmonic CdS/Co-MoO2-x@C Schottky junction photocatalyst for the first time. Through varying the Co heteroatom doping and oxygen vacancies in our Co-MoO2-x@C cocatalyst, we show adjustable SBH at the interface and tunable photothermal effect in CdS/Co-MoO2-x@C, which leads to inhibited energetic electrons backflow in metallic Co-MoO2-x to improve the electron density. Moreover, optimized electronic structure gives rise to a zero-approaching Gibbs free energy for intermediate state, enabling CdS/Co-MoO2-x@C with promoted intrinsic H2 evolution kinetics.Furthermore, the extended light absorption and elevated reaction temperature stemming from strong LSPR effect of Co-MoO2-x contribute to the decrease of apparent activation energy from 13.824 to 6.579 kJ/mol for H2 evolution. To this end, CdS/Co-MoO2-x@C-7 photocatalyst yields a full-spectrum driven photocatalytic H2 production rate of 89.95 mmol g−1h−1, surpassing most reported CdS-based photocatalyst. This study opens a new avenue toward construction of efficient broad-spectrum active photocatalyst.

Modulating the Primary and Secondary Coordination Spheres of Single Ni(II) Sites in Metal-Organic Frameworks for Boosting Photocatalysis.

Though the coordination environment of single metal sites has been recognized to be of great importance in promoting catalysis, the influence of simultaneous precise modulation of primary and secondary coordination spheres on catalysis remains largely unknown. Herein, a series of single Ni(II) sites with altered primary and secondary coordination spheres have been installed onto metal-organic frameworks (MOFs) with UiO-67 skeleton, affording UiO-Ni-X-Y (X = S, O; Y = H, Cl, CF3) with X and Y on the primary and secondary coordination spheres, respectively. Upon deposition with CdS nanoparticles, the resulting composites present high photocatalytic H2 production rates, in which the optimized CdS/UiO-Ni-S-CF3 exhibits an excellent activity of 13.44 mmol g-1, ∼500 folds of the pristine catalyst (29.6 μmol g-1 for CdS/UiO), in 8 h, highlighting the key role of microenvironment modulation around Ni sites. Charge kinetic analysis and theoretical calculation results demonstrate that the charge transfer dynamics and reaction energy barrier are closely correlated with their coordination spheres. This work manifests the advantages of MOFs in the fabrication of structurally precise catalysts and the elucidation of particular influences of microenvironment modulation around single metal sites on the catalytic performance.

Visible light-induced H2 production and pollutant degradation by copper oxide nanosphere embedded zinc-cadmium-sulfide composite

Green hydrogen production using solar water splitting and solving water pollution issues are intricately intertwined global goals which are hindered by the scarcity of highly active photocatalytic materials. Herein, we have presented a simple strategy to couple two semiconductors (Cu2O and ZnCdS) to form a type-I heterojunction with high visible light response. The as-synthesized heterojunction was well characterized by the battery techniques, such as TEM, HAADF-STEM elemental mapping, XRD and XPS. The visible light response was higher for composite than individual components, as was also supported by UV–vis DRS. The Cu2O-ZnCdS composite showed a higher visible light-driven photocatalytic H2 production rate (78.5 µmol g–1 h–1). The catalyst was also active for photocatalytic degradation of a model dye-methylene blue (MB)-with a degradation rate constant of 0.079 min−1. The enhanced performance of the Cu2O-loaded ZnCdS catalysts can be ascribed to both factors, such as enhancement of the visible light absorption and the growth of Cu2O-ZnCdS heterojunction. The heterojunction formation facilitates efficient charge separation with smaller charge resistance, as evidenced by transient photocurrent response and electrochemical impedance spectroscopy (EIS) studies. This study strongly indicates that the photocatalytic reactions with this catalyst material are kinetically favoured by coupling the two semiconductors.Graphical abstract

Photocatalytic Hydrogen Production from Pure Water Using a IEF-11/g-C3N4 S-Scheme Heterojunction.

Construction of S-scheme heterojunction offers a promising way to enhance the photocatalytic performance of photocatalysts for converting solar energy into chemical energy. However, the photocatalytic H2 production in pure water without sacrificial agents is still a challenge. Herein, the IEF-11 with the best photocatalytic H2 production performance in MOFs and suitable band structure was selected and firstly constructed with g-C3N4 to obtain a S-scheme heterojunction for photocatalytic H2 production from pure water. As a result, the novel IEF-11/g-C3N4 heterojunction photocatalysts exhibited significantly improved photocatalytic H2 production performance in pure water without any sacrificial agent, with a rate of 576 μmol/g/h, which is about 8 times than that of g-C3N4 and 23 times of IEF-11. The novel IEF-11/g-C3N4 photocatalysts also had a photocatalytic H2 production rate of up to 92 μmol/g/h under visible light and a good photocatalytic stability. The improved performance can be attributed to the efficient separation of photogenerated charge carriers, faster charge transfer efficiency and longer photogenerated carrier lifetimes, which comes from the forming of S-scheme heterojunction in the IEF-11/g-C3N4 photocatalyst. This work is a promising guideline for obtaining MOF-based or g-C3N4-based photocatalysts with great photocatalytic water splitting performance.