H2 Generation Activity Research Articles

Fabrication of CoTiO3/MgIn2S4 S–scheme heterojunctions with efficient charge separation to enhance the photocatalytic activities of hydrogen generation and formaldehyde removal

The efficient separation of photoinduced charge carriers is a primary factor in the catalytic performance of photocatalysts. Constructing S-scheme heterojunctions is a prospective strategy to efficiently and spatially separate photoinduced charges while retaining strong oxidation and reduction capacities of the catalyst system. Herein, CoTiO3/MgIn2S4 (abbreviated x% CTO/MIS, where x% represents the mass ratio of CTO-to-MIS; x = 5, 10, 15, 20, and 25) heterojunctions were successfully synthesized using a hydrothermal method. These heterojunctions exhibited highly efficient and reusable visible-light photocatalytic properties for hydrogen (H2) generation and formaldehyde (HCHO) degradation. Notably, the 15 % CTO/MIS demonstrated an admirable H2 evolution activity of 631.77 μmol·g−1·h−1, with AQE = 2.25 % at λ = 420 nm, and an HCHO degradation rate of 67.18 %. The intermediate products generated during HCHO removal were identified applying in situ diffuse reflectance infrared Fourier transform spectroscopy. The exceptional catalytic performance of the synthesized materials was attributed to the boosted light absorption and utilization, rapidly separation, and transfer of photoproduced charge carriers, which resulted from the internal electric field of the S-scheme mechanism. Moreover, the S-scheme electron transfer pathway for the CTO/MIS catalyst system during the photocatalytic process was confirmed using electron spin resonance spectroscopy, free-radical capturing tests, density functional theory calculations, in situ X-ray photoelectron spectroscopy, and semiconductor energy band theory. The study offers an innovative perspective for establishing S-scheme heterojunctions with highly efficient and stable photocatalytic activity for H2 generation and HCHO removal.

Droplet microreactor continuous synthesis of hierarchical Rh on CdZnS snowflakes for enhanced photocatalytic hydrogen evolution

Promising droplet microreactor-cation exchange strategy is utilized to construct the unique Rh hierarchical structure (RhHS) and Rh nanoclusters (RhNCs) on CdZnS (CZS) snowflakes. The fabricated RhHS/RhNCs/CZS achieves an optimal hydrogen evolution activity of 926.0μmol h−1 g−1, which is 5.9 and 10.5 folds enhancement that of CZS and CdS, respectively. The enhanced activity for H2 generation can be attributed to the RhHS/RhNCs (accelerating electron transfer), as well as the hierarchical structure of RhHS and CZS, which enhances reflection–absorption of visible light. Theoretical calculations reveal that Rh species can serve as new H* generation-release sites, reducing the energy barrier for hydrogen evolution. Notably, in situ Raman confirmed the Rh (Rh-H) and S (S-H) two main active sites for proton reduction during hydrogen generation. This paper provides a novel approach to constructing hierarchical structure photocatalyst (RhHS/RhNCs/CZS) for enhanced photocatalytic H2 production.

Engineering of visible light-activated ZnIn2S4/N-rGO S-scheme heterojunction photocatalyst for H2 generation

The design of S-scheme heterojunction photocatalysts emerges as high-profile candidates for hydrogen (H2) generation. Herein, by integrating heterojunction creation and heteroatom-doping approaches, ZnIn2S4/N-rGO photocatalyst is synthesized using a hydrothermal process. Crystallinity, morphology, surface area, light absorption, interfacial interaction, and charge separation and migration properties of ZnI2S4/Nitrogen-doped reduced graphene oxide (ZnIn2S4/N-rGO) are analytically explored to authenticate its successful construction. Consequently, the H2 generation performance of ZnIn2S4/N-rGO reached 2847 µmolh-1g-1 under visible light illumination, which is about 9.7 and 1.6 times as high as that of ZnIn2S4 and ZnIn2S4/rGO, respectively, with efficient stability. ZnIn2S4/N-rGO exhibits enhancement in the optical response, promotes the surface area, and improves separation and transport of photoexcited electron/hole pairs, attributing to higher H2 generation activity. The S-scheme charge migration mechanism is authenticated through EPR spectra. The current study not only signifies that ZnIn2S4/N-rGO is an excellent photocatalyst for H2 generation but also offers a route to develop outstanding and stable photocatalysts by combining heterojunction creation and heteroatom-doping approaches.

Ultrathin Porous Carbon Nitride Anchored with Pt Nanoclusters for Synergistic Enhancement of Hydrogen Production in Alkaline Photocatalytic Polyester Reforming.

Photocatalytic reforming (PR) of polyester waste, fueled by renewable sources like solar energy, offers a sustainable method for producing clean H2 and valuable by-products under mild conditions. The design of high-performance photocatalyst plays a pivotal role in determining the efficacy of an alkaline polyester PR system, influencing H2 generation activity and selectivity. Here, ultrathin porous carbon nitride nanosheets (UP-CN) loaded with Pt nanoclusters (Pt NCs, average diameter of 1.7nm) with uniform Pt NCs distribution are introduced. The resulting Pt NCs/UP-CN catalyst can accelerate charge and mass transfer while providing additional active sites, achieving superior H2 generation rates of 11.69mmol gcat -1 h-1 and 2923mmol gPt -1 h-1 under AM 1.5 light, which nine times higher than that of Pt nanoparticles-bulk graphitic carbon nitride composite (1.29mmol gcat -1 h-1 and 258mmol gPt -1 h-1) as counterpart. This performance also surpasses that of previously reported carbon nitride-based and TiO2-based photocatalysts. Moreover, the density functional theory calculations reveal a significant reduction in the energy barrier for the water dissociation step (H2O + * → *H + OH) at the interface between UP-CN and anchored Pt NCs, showcasing the synergistic effect between Pt NCs and UP-CN. This catalytic system also exhibits universality across various polyester plastics.

Z-scheme promoted interfacial charge transfer on Cu/In-porphyrin MOFs/CdIn2S4 heterostructure for efficient photocatalytic H2 evolution

The rational modulation of charge transfer pathway within heterojunction is essential toward boosting photocatalytic activity for H2 production from water splitting Herein, the bimetallic-modified porphyrin MOFs (CuIn-PMOFs) crystals have been developed as a substrate for the epitaxial wrapping of CdIn2S4 (CIS) nanosheets via a facile solvothermal process to fabricate novel hierarchical CuIn-PMOFs@CdIn2S4 (CuIn-PMOFs@CIS) heterojunctions. The experimental results, combined with density-functional theory calculations, demonstrated that the CuIn-PMOFs have a more negative conduction band position and the electrons transfer pathway is inclined from CIS to CuIn-PMOFs, which leads to the formation of unique Z-scheme heterojunctions. Profiting from the special “O-In” charge transfer channel, extensive highly active photoinduced electrons areaggregated and depleted in the conduction band of CuIn-PMOFs, contributing to the improvement of H2 generation activity. Moreover, the heterojunction model also revealed the minimum Gibbs free energy for H* intermediate adsorption (ΔGH*). Concretely, the optimized composite displayed a maximum H2 evolution rate of 7527.54 μmol g–1h−1, which is around 13.12 and 6.63 times higher than that of pure CdIn2S4 and CuIn-PMOFs, respectively. This work aims to suggest that constructing distinctive Z-scheme modulated charge transfer mechanism is an advanced strategy for acquiring highly efficient photocatalysts.

Rational design of Z-scheme CoS@NC/CdS heterojunction with N doped carbon (NC) as an electron mediator for enhanced photocatalytic H2 evolution

Rational construction of Z-scheme heterojunction photocatalysts have been regarded as a promising approach for enhanced hydrogen generation performance from splitting water. Herein, a Z-scheme heterojunction CoS@NC/CdS using N doped carbon (NC) as an electron mediator bridge was fabricated by coupling CdS with CoS@NC prepared via solid-state self-sulfuring a novel cationic cobalt (Co) based metal–organic framework (namely PZH-42) under argon atmosphere. Notably, the H2 production activity could be optimized by regulating the sulfurization temperature and the content of CoS@NC. The 20-CoS@NC−700/CdS with sulfurization temperature of 700 ℃ and the content for CoS@NC−700 of approximately 20 wt% exhibited the highest H2 generation activity of 20.56 mmol h−1 g−1 with an apparent quantum efficiency (AQE) of 23.98 %, which was 70 and 10-folds as high as that of CdS and CdS/CoS. Such improvement might be attributed to the four synergisms of rapidly separating the electrons and holes by the NC electron mediator bridge in Z-scheme system, retaining electrons at the higher position conduction band (CB) of Z-scheme heterojunction more than that of the type-II heterojunction, increasing the specific surface area and enhancing light absorption range and intensity. More significantly, this rare idea can not only provide a promising strategy for designing highly efficient Z-scheme heterojunction photocatalysts, but also expand the photocatalytic H2 production applications of Co-based metal–organic framework.

Heterogeneous Oxidase-Type Catalysis for H2 Generation at Low Temperatures.

The long-term objective in the field of heterogeneous catalysis is to develop an enzyme-like catalytic pathway that can achieve exceptional catalytic performance even at low temperatures. Herein, we have demonstrated a heterogeneous oxidase-type catalysis on the ZnO-supported Ru clusters (Ru/ZnO) for efficient H2 generation from an aqueous solution of formaldehyde (HCHO) at low temperatures. Due to its unique reaction pathway, the Ru/ZnO catalysts exhibited a temperature-insensitive activity for H2 generation at the temperature of 15 to 45 °C. Remarkably, even at a low temperature of 5 °C, the Ru/ZnO catalysts still enabled an H2 generation rate of 13.8 mmol gcat-1 h-1 with a turnover frequency (TOF) of 1678 h-1. Additionally, instead of producing a CO2/CO molecule, the HCHO molecule underwent a transformation into formic acid and/or formate as the byproduct. This finding presents a novel class of heterogeneous catalysts to expand the potential application scenarios of liquid hydrogen storage and transportation systems.

Synthesis and application of Cu-CaTiO3-GO ternary composite: A new visible-light active multifunctional photocatalyst efficient towards antibiotic cefixime degradation and H2 evolution reaction

To combat the issues of energy scarcity and environmental pollution, a visible-light responsive, ternary photocatalyst (Cu-CaTiO3-GO) was fabricated, by photo-depositing Cu nanoparticles over a CaTiO3-GO binary composite. The physicochemical characteristics of Cu-CaTiO3-GO were investigated using XRD, HR-TEM, FE-SEM, EDS-mapping XPS, Raman, FT-IR, BET, EIS, UV–vis DRS, and PL techniques. In comparison with pristine CaTiO3, and binary composites (Cu-CaTiO3, CaTiO3-GO), the ternary hybrid exhibited superior photocatalytic activity for H2generation as well as antibiotic cefixime (CFX) degradation. Under LED light, the rate of H2 generation over Cu-CaTiO3-GO accumulated to 57.69 mmolh−1, while the photodegradation efficiency for CFX reached 94.1 % in 100 min with 53.4 % of TOC removal. The upgraded performance is credited to synergistic effects of Cu NPs (SPR effect), CaTiO3 (specialized cuboid-like morphology), and GO (high conductivity), co-existing in the trio-hybrid, which resulted in a greatly increased surface area, an expanded spectral response range, a stronger adsorption property, efficient charge migration and separation extent. Ternary catalyst performed well even in the 4 recycling tests (retaining 79.4 % CFX removal and 52.51 mmolh−1 H2 evolution efficiency). In Cu-CaTiO3-GO system, the electron transport channel (Cu → CaTiO3 → GO) with adequate band potentials effectively supports both photocatalytic oxidation and reduction. Photoelectrons are enriched and transferred by plasmonic Cu, and then captured by GO, an e- sink. This maximizes composite photo redox capability, rapidly generating active radicals (OH), and (O2-), degrading CFX to simpler molecules and reducing proton to H2. The effectiveness of Cu-CaTiO3-GO was even tested in the real water matrices. Besides, degradation intermediates of CFX were elucidated using LC-MS, and the decomposition pathway was suggested. Finally, the probable photocatalytic reaction mechanism was deduced for both the degradation and H2 generation processes. The current study proposes a non-noble transition metal-based perovskite-type photocatalytic material for both clean energy generation and wastewater treatment.

Tailoring of Visible to Near-Infrared Active 2D MXene with Defect-Enriched Titania-Based Heterojunction Photocatalyst for Green H2 Generation.

A wide solar light absorption window and its utilization, long-term stability, and improved interfacial charge transfer are the keys to scalable and superior solar photocatalytic performance. Based on this objective, a noble metal-free composite photocatalyst is developed with conducting MXene (Ti3C2) and semiconducting cauliflower-shaped CdS and porous Cu2O. XPS, HRTEM, and ESR analyses of TiOy@Ti3C2 confirm the formation of enough defect-enriched TiOy (where y is < 2) on the surface of Ti3C2 during hydrothermal treatment, thus creating a third semiconducting site with enough oxygen vacancy. The final material, TiOy@Ti3C2/CdS/Cu2O, shows a broad absorption window from 300 to 2000 nm, covering the visible to near-infrared (NIR) range of the solar spectrum. Photocatalytic H2 generation activity is found to be 12.23 and 16.26 mmol g-1 h-1 in the binary (TiOy@Ti3C2/CdS) and tertiary composite (TiOy@Ti3C2/CdS/Cu2O), respectively, with good repeatability under visible-NIR light using lactic acid as the hole scavenger. A clear increase of efficiency by 1.53 mmol g-1 h-1 in the tertiary composite due to NIR light absorption supports the intrinsic upconversion of electrons, which will open a new prospective of solar light utilization. Decreased charge-transfer resistance from the EIS plot and a decrease in PL intensity established the improved interfacial charge separation in the tertiary composite. Compared to pure CdS, H2 generation efficiency is 29.6 times higher on the noble metal-free tertiary composite with an apparent quantum efficiency of 12.34%. Synergistic effect of defect-enriched TiOy formation, creation of proper dual p-n junction on a Ti3C2 sheet as supported by the Mott-Schottky plot, significant NIR light absorption, increased electron mobility, and charge transfer on the conductive Ti3C2 layer facilitate the drastically increased hydrogen evolution rate even after several cycles of repetition. Expectantly, the 2D MXene-based heterostructure with defect-enriched dual p-n junctions of desired interface engineering will facilitate scalable photocatalytic water splitting over a broad range of the solar spectrum.

Highly intra- and inter-plane crystalline ReSx/g-C3N4: Facile synthesis and boosted photocatalytic H2 evolution

Improving the crystallinity of g-C3N4 is regarded as a desirable pathway to boost its photocatalytic activity. However, the current highly crystalline g-C3N4 photocatalysts are mainly emphasized on increasing their inter-plane crystallinity through ordered stacking layers while their intra-plane crystallinity has been seldomly concerned, causing the finitely enhanced photocatalytic performance. In this work, the high intra- and inter-plane crystallinity of g-C3N4 accompanied by the deposition of amorphous ReSx cocatalyst are simultaneously realized through a facile strategy, causing the successful formation of highly intra- and inter-plane crystalline ReSx/g-C3N4 (ReSx/c-CN) photocatalysts. In this case, the mixture of melamine and NaCl is initially calcined to prepare highly intra-plane crystalline g-C3N4 (i-CN). Subsequently, the i-CN is further treated by HCl to improve its inter-plane crystallinity, which can simultaneously realize the deposition of amorphous ReSx cocatalyst on g-C3N4 surface to finally produce ReSx/c-CN photocatalysts. Consequently, the high intra- and inter-plane crystallinity of g-C3N4 can effectively boost the separation and migration of photogenerated carriers, while the amorphous ReSx cocatalyst can supply abundant active sites for interfacial H2-evolution reaction. Thus, the optimized ReSx/c-CN(3.0 wt%) photocatalyst exhibit remarkably improved H2-generation activity (23.4 μmol h−1), which is about 8.4-fold of the ReSx/bulk g-C3N4(3.0 wt%) photocatalyst. This work may supply new ideas for exploring other highly efficient photocatalysts in various applications.

A multifunctional membrane based on TiO2/PCN-224 heterojunction with synergistic photocatalytic-photothermal activity under visible-light irradiation

Photocatalysis is widely recognized as a promising method for various clean applications, and membrane technology is emerging as a potential functional form of photocatalysts. In this paper, an organic–inorganic TiO2/PCN-224 (TP) core-shell hybrid was fabricated and loaded on a PVDF membrane using vacuum filtration technique. This integration enabled the creation of a multifunctional TP-constructed-membrane with synergistic photocatalytic-photothermal activity for H2 generation, tetracycline (TC) degradation and inactivation of Staphylococcus aureus (S. aureus). The high efficiency of the TP membrane under visible light can be attributed to the photothermal and photodynamic effects induced by PCN-224, as well as the role of TiO2 as the electron transfer platform. Moreover, the superhydrophilicity of the TP membrane facilitated enhanced rates of water-based catalytic reactions. As a result, under visible light, the optimal TP membrane demonstrated remarkable outcomes under visible light, including H2 generation at a rate of 1.88 mmol g−1 h−1, 86% degradation of TC (at a concentration of 50 mg/L) and 99.99% inactivation of S. aureus. These results exemplify the achievement of multiple objectives with a single catalyst, truly embodying the concept of "three birds, one stone".

Facile template-free fabrication of different micro/nanostructured In2O3 for photocatalytic H2 production from glucose solution

Indium oxide (In2O3) is a promising semiconductor used for various photocatalytic reactions, yet the green and template-free synthesizing the different micro/nanostructured In2O3 with tunable morphology is still full of challenge. In this study, the three morphological In2O3 with 3D micro-cubelike (In2O3-MC), 3D micro-ricelike (In2O3-MR), and 2D nano-platelike (In2O3-NP) were successfully fabricated through a facile hydrothermal strategy without any organic template additives. Owing to the enlarged specific surface area, promoted charge migration rate and suitable surface oxygen vacancies density, the unique 3D ricelike In2O3-MR exhibited the best photocatalytic H2 generation activity from biomass glucose solution, which was 1.9-fold and 1.7-fold higher than that of In2O3-MC and In2O3-NP under the same experimental conditions. In addition, the optimum photoactivity of In2O3-MR was achieved under the alkaline environment with pH = 11 and 1.0 wt% Pt cocatalyst loading, which was better than the most of previously reported In2O3-based photocatalysts. Simultaneously, the possible photocatalytic mechanism for solar H2 evolution from glucose solution was also discussed. Our work will bring about potential application in preparation of other photocatalysts with controlling morphology for renewable photocatalysis.

Spectroscopic Study on CdS/Ni/KNbO3: Confirming Ni Effect to Photocatalytic Activity.

Herein, we report the structural and photophysical properties of CdS/Ni/KNbO3 composites with a quantum yield for photocatalytic H2 generation that is CdS and Ni amount dependent. The nonstoichiometric KNbO3 (1:1.1) structure indicates the defect at the K site, which is Ni-occupied during its deposit process. It exhibits a tendency like a Ni-doped characteristic up to 0.1 wt % Ni and then forms a Ni cluster in case the Ni amount exceeds 0.1 wt %. The related structural and photophysical properties of CdS/Ni/KNbO3 are examined with Fourier transform infrared, X-ray diffraction, ultraviolet-visible absorption, and luminescence spectral analysis. It demonstrates the CdS/Ni/KNbO3 composites to be an efficient light conversion caused by efficient charge/electron transfer between KNbO3 and CdS via doped Ni. The photocatalytic activity of CdS/Ni/KNbO3 exhibits a CdS and Ni amount dependency. The best photocatalytic activity for H2 generation is obtained with 0.1 wt % Ni and 2.9 wt % CdS as it gradually declines with the excess Ni amount than 0.1 wt % caused by a formed Ni cluster.

Effective graphene incorporation of strontium niobate–doped titanium oxide for photocatalytic hydrogen production

To meet the increasing global demand for clean energy and mitigate the impact of CO2 emissions on climate change, the production of photocatalytic hydrogen through water splitting is a compelling scientific and technological objective. Despite considerable efforts, the establishment of a reliable and highly efficient system for hydrogen generation powered by visible light remains challenging. In this study, we developed a solar-active strontium niobate-doped titanium oxide incorporated with graphene (Sr2Nb2O7–rGO–TiO2), characterized by various analytical techniques such as optical, morphological, HR-TEM, XPS, and XRD. Sr2Nb2O7–rGO–TiO2 demonstrated enhanced photocatalytic H2 evolution under solar irradiation without requiring precious-metal doping. The maximum H2 production performance rate of 1769 μmol/g/h was attained with the Sr2Nb2O7–rGO–TiO2 composites, significantly surpassing those of the bare (TiO2: 210 μmol/g/h, Sr2Nb2O7: 88 μmol/g/h) and binary (TiO2–rGO: 430 μmol/g/h, Sr2Nb2O7–rGO: 176 μmol/g/h, and Sr2Nb2O7–TiO2: 880 μmol/g/h) photocatalysts. The enhanced performance of the Sr2Nb2O7–rGO–TiO2 composite is attributable to the synergistic effect of rGO acting as an electron-transfer bridge. Thus, with the integration of rGO, absorption is attainable in an extended range up to 445 nm (2.90 eV), suggesting that the composite material could enable the catalyst to absorb more visible light. Additionally, the composite exhibited minor degradation after five consecutive cycles, demonstrating its excellent stability and reusability for hydrogen generation. Based on a comprehensive evaluation of the ESR and transient photocurrent response, a potential Z-scheme mechanism for the photocatalytic H2 generation activity over Sr2Nb2O7–rGO–TiO2 was suggested. The Z-scheme processability allows more electrons to contribute to the H2 evolution reduction. In this study, we developed a non-toxic, cost-effective, highly efficient, and recyclable photocatalyst for H2 production.

Relationship between defect and strain in oxygen vacancy-engineered TiO2 towards photocatalytic H2 generation

Photocatalytic H2 generation is an effective approach to convert solar energy into renewable H2 energy and has drawn great attentions. To improve the catalytic activity, lots of attentions have been paid to developing advanced strategies, of which oxygen vacancy engineering is considered as a promising one. However, oxygen vacancy induced coexistence of defect and strain makes understanding the essential mechanism of enhanced photocatalytic performance elusive and challenging. Here, the classic photocatalyst TiO2 is selected as a paradigm to reveal the relationship between the accompanied defect and strain in boosting H2 generation activity. It is found that oxygen vacancy concentration almost shows a volcano-type trend, while strain exhibits a monotonic decrease with increasing the calcination temperature. An optimal photocatalytic H2 yield of 788 μmol g−1 h−1 is achieved over the TiO2 with high oxygen vacancy concentration but slight strain. This value is 2.5 times higher than the counterpart with low oxygen vacancy concentration and large strain, indicating that oxygen vacancy induced defect instead of strain plays the dominate role in enhancing photocatalytic H2 generation, which is further verified by theoretical calculations and experimental carrier dynamics analysis. This work uncovers the relationship between defect and strain in oxygen vacancy-engineered photocatalysts.

Construction of II-type and Z-scheme binding structure in P-doped graphitic carbon nitride loaded with ZnO and ZnTCPP boosting photocatalytic hydrogen evolution

A ternary heterostructure (ZnPPO) was constructed by loading ZnO and tetrakis (4-carboxyphenyl) zinc porphyrin (ZnTCPP) with P-doped g-C3N4 (PCN). In contrast to binary heterostructures (PCN-ZnO, ZnTCPP-ZnO and ZnTCPP-PCN) and single components (PCN, ZnTCPP and ZnO), ZnPPO has superior photocatalytic activity for H2 generation from water splitting. It is revealed that a binding structure of Ⅱ-type and Z-scheme has been constructed in ZnPPO, which plays a vital role in transferring photo-excited charge carriers. The significant enhancement of photocatalytic activity in ZnPPO is attributed to the effective transfer of photo-generated electrons and holes between the components of the ternary heterostructure.

Tailoring Morphology in Hydrothermally Synthesized CdS/ZnS Nanocomposites for Extraordinary Photocatalytic H2 Generation via Type-II Heterojunction

CdS@ZnS core shell nanocomposites were prepared by a one-pot hydrothermal route. The morphology of the composite was tuned by simply changing the Zn2+ precursor concentration. To characterize the samples prepared, various techniques were employed, including XRD, FESEM, TEM, XPS and UV-vis DRS. The band gaps of CdS and ZnS were measured to be 2.26 and 3.32 eV, respectively. Compared with pure CdS, the CdS@ZnS samples exhibited a slight blue shift, which indicated an increased band gap of 2.29 eV. The CdS@ZnS core shell composites exhibited efficient photocatalytic performance for H2 generation under simulated sunlight illumination in contrast to pure CdS and ZnS. Additionally, an optimized H2 generation rate (14.44 mmol·h−1·g−1cat) was acquired at CdS@ZnS-2, which was approximately 4.6 times greater than that of pure CdS (3.12 mmol·h−1·g−1cat). Moreover, CdS@ZnS heterojunction also showed good photocatalytic stability. The process of charge separation over the photocatalysts was investigated using photoelectrochemical analysis. The findings indicate that the CdS@ZnS nanocomposite has efficient charge separation efficiency. The higher H2 generation activity and stability for CdS@ZnS photocatalysts can be attributed to the intimate interface in the CdS@ZnS core–shell structure, which promoted the light absorption intensity and photoinduced charge separation efficiency. It is expected that this study will offer valuable insights into the development of efficient core shell composite photocatalysts.

Growth of tunable Au-BaO@TiO2/CdS heterostructures: Acceleration of hydrogen evolution from water splitting

The need for efficient and sustainable catalysts to generate clean energy through water splitting is a requirement of the current era. In this study, TiO2/CdS heterostructures were synthesized using hydrothermal reaction. To enhance the photocatalytic performances of TiO2/CdS, BaO and Au were in-situ deposited via chemical reduction and hydrothermal treatment at 165 °C for 6 h. Finally Au-BaO@TiO2/CdS catalysts were synthesized for photocatalytic hydrogen generation from water splitting. The optical and structural properties of catalysts were examined with FT-IR, XRD, Raman and UV–Vis-DRS techniques. The morphology and chemical properties of catalysts were obtained using EDX, AFM, XPS and SEM techniques. Photoreaction and H2 production activities were monitored at Pyrex reactor (150 mL) and GC-TCD (Shimadzu-2014). The tunable fabrication approach provides a novel strategy for tailoring the properties of TiO2/CdS heterostructures, allowing for optimization of their photocatalytic performance. The enhanced surface plasmon impact achieved through Au-NPs incorporation opens up new possibilities for improving the efficiency. The results demonstrate that Au-BaO@TiO2/CdS catalysts exhibit significantly higher H2 generation activity (13.54 mmol g−1h−1). This H2 evolution activity was found higher than other catalysts i.e. TiO2/CdS, BaO@TiO2/CdS and Au@TiO2/CdS. Higher catalytic activity in case of Au-BaO@TiO2/CdS was attributed to the co-existence of BaO and Au-NPs. The Au-NPs provide hot electrons (via SPR effect) that increase the electron pool over the surfaces of TiO2/CdS heterostructures. During photoreaction, BaO assists the transfer of photoexcited electrons from TiO2/CdS system to the active centers (i.e. Au cocatalysts). In addition, various factors that affect the H2 production rates (i.e. pH, temperature, catalyst dose and effect of light intensity) were evaluated and discussed.

Robust one-pot solvothermal incorporation of InVO4 with polymeric-C3N4 nanosheets with improved charge carrier separation and transfer: A highly efficient and stable photocatalyst for solar fuel (H2) generation

Polymeric-C3N4 is a photocatalyst with desirable properties for efficient solar fuel (H2) generation. However, p- C3N4 exhibits a low H2 evolution rate. Herein, InVO4 is successfully incorporated on the surface of p- C3N4 nanosheets via a one-pot solvothermal method to generate solar fuel (H2) effectively. The optical gap energy of p- C3N4 was red-shifted to 2.23 eV after incorporating InVO4. A small arc radius of the Nyquist plot and substantial quenching of PL was observed when InVO4 was added to p- C3N4. The optimized catalyst loading (15 wt%) shows a maximum H2 production activity of 8980 µmol/g/h. This outstanding performance is a nearly 56-fold enhancement in comparison with bare p-C3N4. Furthermore, the STH conversion efficiency of 1.87% is achieved with the optimized photocatalysts, which is higher than many g- C3N4 - based photocatalysts. Moreover, the H2 generation activity achieved in the present work is higher than the reported one using the same InVO4-g- C3N4 photocatalysts.

Construction of porous ZnS/TiO2 S-scheme heterostructure derived from MOF-on-MOF with boosting photocatalytic H2-generation activity

The development of photocatalysts with synergistic effects is a crucial step in improving the utilization of clean energy for hydrogen generation. In this study, a novel porous ZnS/TiO2 heterostructure was successfully fabricated through the sulfuration of ZIF-8/NH2-MIL-125(Ti) using a one-pot hydrothermal method. Under simulated solar light, the as-prepared ZnS/TiO2 (5:1) heterostructure exhibited enhanced photocatalytic hydrogen production with a rate of 1718 μmol h−1 g−1, which is 4.8 times of ZnS and 38.8 times of TiO2, respectively. The construction of a S-scheme heterojunction between ZnS and TiO2 can enhance electron transfer and suppress electron-hole recombination, which is crucial for efficient photocatalysis. The photoelectrochemical test results were analyzed in detail to understand the photoinduced electron transfer process and the proposed photocatalytic mechanism. This work has significant potential for enhancing the solar hydrogen production performance of MOFs-derived heterojunction photocatalysts, providing a promising approach for clean energy generation.