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Potential Application of Metal–organic frameworks for Photocatalytic Water Splitting
摘要： These days, the environmental pollution and energy shortage are the crucial global issues. Therefore, replacing the renewable source of energy with the fossil fuels is the most promising approach to solve the aforementioned problems. Hydrogen is an attractive source energy because of its high energy density and its combustion by-product is only water. Hydrogen production through photosplitting of water over a semiconductor based photocatalyst is a desirable approach to diminish the global energy and environmental problems. However, its low solar conversion efficiency and finding suitable photocatalyst still remain as the main challenge for this system. Recently metal–organic frameworks (MOFs) have received great attention for the photocatalytic hydrogen production due to their large surface to volume ratio, design flexibility, and well-defined porosity. In this short review, we focus on the previous studies on the various types of MOFs based photocatalyst in the solar hydrogen production system. The main intention of review is to highlight the importance of coupling molecular approaches of catalyst design with materials science strategies in the improvement of MOFs based photocatalysts, which will undoubtedly lead to a very bright future for photocatalytic water.
关键词： Solar Energy,Photocatalytic Water Splitting,Metal–organic frameworks,Hydrogen Production,Renewable Energy
更新于2025-09-04 15:30:14
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Band structure tuning and charge separation of MNX monolayers and MNX/GaS van der Waals heterostructures
摘要： Efficient charge separation and band structure tuning are very important for application to photoelectric device. Here, based on first-principles calculations, we propose two-dimensional (2D) MNX (M=Zr, Hf; X=Cl, Br, I) monolayers which can be exfoliated from the corresponding layered bulk phase due to the low cleavage energy. The phonon band structure and the mechanical analysis indicate that 2D MNX monolayers can form free-standing membranes. The calculated results suggest that 2D MNX monolayers are indirect band gap semiconductors with band gaps in the range of 1.55-3.37 eV. Among them, MNI (M=Zr, Hf) monolayers with effective charge separation and moderate band gaps would have potential application to photocatalytic water splitting. In order to realize the effective charge separation for the other MNX monolayers, MNX/GaS (X=Cl, Br) heterostructures are investigated. Our calculations reveal that MNX/GaS heterostructures are typical type-II band alignment, facilitating the separation of photogenerated carriers where electrons and holes are localized in MNX and GaS monolayers, respectively. Furthermore, the band gaps of the MNX/GaS heterostructures are obviously narrowed compared to those of the isolated constituent monolayers. In addition, the band gaps and band edge positions of MNX/GaS heterostructures can further be tuned by biaxial strain to match better with the redox potentials of water. These findings in this study not only enrich the family of 2D materials, but also demonstrate that MNI (M=Zr, Hf) monolayers and MNX/GaS heterostructures are promising candidates for photocatalytic materials.
关键词： van der Waals heterostructures,photocatalytic water splitting,band structure tuning,MNX monolayers,charge separation
更新于2025-09-04 15:30:14
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<i>In situ</i> topotactic fabrication of direct Z-scheme 2D/2D ZnO/Zn <sub/>x</sub> Cd <sub/>1?x</sub> S single crystal nanosheet heterojunction for efficient photocatalytic water splitting
摘要： Direct Z-scheme heterojunction can effectively enhance the photocatalytic activity due to its low carrier recombination rate and high redox ability. In this study, a 2D/2D ZnO/ZnxCd1?xS single crystal nanosheet heterojunction is synthesized in situ by topotactic sulfurization/oxidization pyrolysis of Zn/Cd/Al layer double hydroxides (LDHs). Its unique structure provides not only numerous intimate interfaces but also a direct Z-scheme junction. The in situ topotactic fabrication of ZnO by the oxidation process causes some Zn ions to dissolve out from the Zn0.67Cd0.33S solid solution nanosheets with increase in annealing temperature and time. The longer the time for oxidation, the more ZnO is obtained. The formation of ZnO yields 2D/2D ZnO/ZnxCd1?xS single crystal nanosheet heterojunction, which increases the visible light absorption and boosts the separation of photogenerated carriers. The ZnO/ZnxCd1?xS-4 single crystal nanosheet heterojunction presents the highest photocatalytic activity under visible light irradiation (38.93 mmol h?1 g?1), which is nearly 16.93 times higher than that of Zn0.67Cd0.33S-300, and an external quantum efficiency of 40.97% at λ = 420 nm. The proposed synthetic route for the construction of 2D/2D ZnO/ZnxCd1?xS single crystal nanosheet provides a direct Z-scheme structure with highly efficient photocatalytic hydrogen evolution activity.
关键词： 2D/2D ZnO/ZnxCd1?xS,photocatalytic water splitting,Zn/Cd/Al layer double hydroxides,Direct Z-scheme heterojunction,topotactic sulfurization/oxidization pyrolysis
更新于2025-09-04 15:30:14
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Nanorods Array of SnO2 Quantum Dots Interspersed Multiphase TiO2 Heterojunctions with Highly Photocatalytic Water Splitting and Self-Rechargeable Battery-Like Applications
摘要： Facing an ever-growing demand for sustainable and renewable power sources, it has detonated the development of novel materials for photocatalytic water splitting, but how to enhance the photocatalytic efficiency remains a core problem. Herein, we reported a conceptual effective and experimental confirmed strategy in SnO2 quantum dots (QD) interspersed multiphase (Rutile, Anatase) TiO2 nanorods arrays (SnO2/RA@TiO2 NRs) to immensely enhance the carrier separation for highly efficient water splitting by merging simultaneously the QD, multiphase, and heterojunction approaches. Under this synergistic effect, a doping ratio of 25% SnO2 QD interspersed into multiphase TiO2 NRs exhibited a superior optical adsorption and excellent photocurrent density (2.45 mA/cm2 at 1.0 V), giving rise to a largely enhanced incident light to current efficiency (IPCE) in the UV region (45~50 %). More importantly, this material-based device can act as power supply with a voltage of ~2.8 V after illumination, which can automatically self-recharging by reacting with oxygen vacancy and water molecule to realize reusing. The current study provide a new paradigm about heightening the carrier separation extent of QD interspersed multiphase heterojunctions, fabricate a new solar energy converting material/device, and achieve a highly photocatalytic water splitting/self-charging battery-like application.
关键词： Photocatalytic,Water splitting,Titanium Dioxide,Heterojunction
更新于2025-09-04 15:30:14