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Role of Surface States in Photocatalytic Oxygen Evolution with CuWO <sub/>4</sub> Particles
摘要： CuWO4 is a medium bandgap (2.3 eV) n-type semiconductor capable of photoelectrochemical water oxidation under applied electrical bias. Here, we show for the ?rst time that suspended microcrystals CuWO4 evolve oxygen photocatalytically under visible illumination from solutions of 0.05 M AgNO3 (10.8 μmol/hour; AQE of 0.56% at 400 nm) and 0.0002 M FeCl3 (1.5 μmol/hour). No oxygen is detected with 0.002 M [Fe(CN)6]3? as sacri?cial agent. The activity dependence on the redox potential of the acceptors is due to the presence of Cu2+ based electron trap states in CuWO4. According to surface photovoltage spectroscopy and electrochemistry, these states are located on the particle surface, 1.8 eV above the valence band edge of the material. Controlling the chemistry of these states will be key to uses of CuWO4 particles in tandem catalysts for overall water splitting.
关键词： water splitting,CuWO4,sacrificial electron acceptors,photocatalytic oxygen evolution,surface states
更新于2025-09-10 09:29:36
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TiO2 nanoparticles modified with 2D MoSe2 for enhanced photocatalytic activity on hydrogen evolution
摘要： As an emerging two-dimensional (2D) nanomaterial, 2D MoSe2 nanosheets has the advantages of wide light response and rapid charge migration ability. In this work, 2D MoSe2/TiO2 nanocomposites were successfully synthesized through a simple hydrothermal method. The microstructure and photocatalytic activity of the nanocomposites were systematically investigated and determined. The corresponding Raman peaks and crystal planes of MoSe2 were analysed by Raman spectroscopy and transmission electron microscopy respectively, demonstrating the successful combination of the MoSe2 nanosheets and TiO2 nanoparticles. UV-vis diffused re?ectance spectra demonstrated that the introduction of MoSe2 did increase the light absorption ability of the nanocomposites. A lower recombination of electrons and holes was demonstrated for the MoSe2/TiO2 heterojunction from photoluminescence results. The photocatalytic hydrogen evolution test showed that the hydrogen production rate was 4.9 mmol h?1 for the sample with 0.1 wt.% MoSe2, 2 times higher than that of bare TiO2. This work provides a novel strategy for improving the photocatalytic properties of semiconductor photocatalyst.
关键词： Water splitting,MoSe2 nanosheets,Two dimensional,Photocatalysis,TiO2
更新于2025-09-10 09:29:36
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Construction of direct Z-Scheme photocatalysts for overall water splitting using two-dimensional van der waals heterojunctions of metal dichalcogenides
摘要： The direct Z-scheme system constructed by two-dimensional (2D) materials is an efficient route for hydrogen production from photocatalytic water splitting. In the present work, the 2D van der Waals (vdW) heterojunctions of MoSe2/SnS2, MoSe2/SnSe2, MoSe2/CrS2, MoTe2/SnS2, MoTe2/SnSe2, and MoTe2/CrS2 are proposed to be promising candidates for direct Z-scheme photocatalysts and verified by first principles calculations. Perpendicular electric field is induced in these 2D vdW heterojunctions, which enhances the efficiency of solar energy utilization. Replacing MoSe2 with MoTe2 not only facilitates the interlayer carrier migration, but also improves the optical absorption properties for these heterojunctions. Excitingly, the 2D vdW MoTe2/CrS2 heterojunction is demonstrated, for the first time, to be 2D near-infrared-light driven photocatalyst for direct Z-scheme water splitting.
关键词： photocatalysis,direct Z-scheme systems,water splitting,two-dimensional van der Waals heterojunctions
更新于2025-09-10 09:29:36
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Plasma Hydrogenated TiO2/Nickel Foam as an Efficient Bifunctional Electrocatalyst for Overall Water Splitting
摘要： Electrochemical water splitting is one of the most efficient technologies for hydrogen production, and fabrication of low-cost, robust, and high active electrocatalysts to replace the noble metal-based materials is one of the key issues. By using H2 plasma treatment, the TiO2/nickel foam composite is converted to be an efficient bifunctional electrocatalysts towards both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in the alkaline electrolyte. The investigation reveals the existence of abundant oxygen vacancies of TiO2, which might lead to the dramatic improvement of the electrical conductivity and faster charge transfer rate; also, density function theory (DFT) calculations suggest the oxygen vacancies activate surrounding surface lattice oxygen to induce the favorable reactive-intermediate adsorption energy of TiO2 for hydrogen evolution; and adjusts the strength of the chemical bonds between the TiO2 surface and reactive-intermediates to more favorable values, inducing the lower energy barrier for oxygen evolution. The finding confers a unique function to TiO2 that is different from its widely accepted role as an electrocatalytically inert semiconductor material, suggesting the H2 plasma treated TiO2/nickel foam could be bifunctional electrocatalyst for overall water splitting.
关键词： Electrocatalysis,Titanium dioxides,Water splitting,Plasma treatment,Defects
更新于2025-09-10 09:29:36
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Photoelectrochemical water splitting properties of CdS/TiO2 nanofibers-based photoanode
摘要： CdS-sensitized TiO2 nanofibers (CdS/TiO2 NFs) structures were fabricated on the indium tin oxide (ITO) conducting substrate that acts as a working electrode in photoelectrochemical (PEC) cell for the generation of hydrogen by water splitting. TiO2 NFs on ITO conducting substrate were synthesized by electrospinning technique using Titanium tetraisopropoxide as the precursor, followed by a calcination process in air at 500 °C for 2 h. CdS deposition on TiO2 NFs structures was carried out by the dip coating method with different dipping times to optimize the water splitting efficiency. The morphologies and crystalline structures of fabricated samples were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The PEC properties of the electrodes were measured using a potentiostat instrument in a mixture of 0.25 M Na2S and 0.35 M Na2SO3 aqueous solutions for CdS/TiO2 photoanodes and in 0.5 M Na2SO4 electrolyte for uncoated TiO2 photoanode under the illumination of simulated sunlight (100 mW/cm2 from 150 W xenon lamp). It was found that an optimized TiO2 NFs structure sensitized by CdS layer yields a photoconversion efficiency of 3.2% at 0.0 V (vs. Ag/AgCl). The value of photocurrent density for CdS/TiO2 NFs samples were more than 20 times higher than that of the uncoated TiO2 NFs sample at 0.0 V (vs. Ag/AgCl) under a simulated sunlight irradiation.
关键词： photoelectrochemical water splitting,electrospinning,dip coating,hydrogen generation,CdS/TiO2 nanofibers
更新于2025-09-10 09:29:36
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(TiO <sub/>2</sub> ) <sub/>1?x</sub> (TaON) <sub/>x</sub> Solid Solution for Band Engineering of Anatase TiO <sub/>2</sub>
摘要： Band engineering of anatase TiO2 was achieved by means of an anatase (TiO2)1?x(TaON)x (TTON) solid solution. Epitaxial thin films of TTON (0.1 ≤ x ≤ 0.9) were synthesized by nitrogen plasma-assisted pulsed laser deposition on (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 substrates. Epitaxial growth of anatase TTON was confirmed by X-ray diffraction. The lattice constants of the TTON thin films increased with TaON content in accordance with Vegard’s law, indicating formation of a complete solid solution. The bandgaps, band alignment, and refractive indices of the TTON thin films were investigated by combination of spectroscopic ellipsometry and X-ray photoelectron spectroscopy. The bandgap of the anatase TTON systematically decreased with increasing x, mainly because of an upward shift in the valence band maximum caused by broadening of the valence band as a result of hybridization of the shallow N 2p orbital. The position of the conduction band minimum was rather insensitive to chemical composition, which makes the band alignment of anatase TTON suitable for photocatalytic water splitting with visible light. The refractive index of anatase TTON monotonically increased with an increase in x.
关键词： Epitaxial thin films,Vegard’s law,X-ray photoelectron spectroscopy,TTON solid solution,Band engineering,Photocatalytic water splitting,Spectroscopic ellipsometry,Nitrogen plasma-assisted pulsed laser deposition,Anatase TiO2
更新于2025-09-10 09:29:36
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A nanostructured CuWO4/Mn3O4 with p/n heterojunction as photoanode toward enhanced water oxidation
摘要： In this paper, we report a novel photoanode fabricated by spin-coating n-type CuWO4 nano-ovoids on the surface of fluorine-doped tin oxide (FTO) glass and then modified with p-type Mn3O4 nanospheres using a deposition-annealing method. A novel nanocomposite (CuWO4/Mn3O4) with p/n heterojunction formed on the surface of FTO glass. The characterazation results of the nanocomposite indicate that the two moieties of the nanocomposite intimately contact with each other. The photoelectrochemical tests of the prepared CuWO4/Mn3O4 photoanode reveal that the electrode can produce larger anodic photocurrent and show enhanced incident photon-to-current efficiency (IPCE) than the bare CuWO4 photoanode does. Moreover, the PEC tandem cell assembled by using the CuWO4/Mn3O4 electrode as photoanode and Pt plate as counter electrode demonstrates enhanced photocatalytic activity and stability for photoeletrochemical (PEC) water splitting. The amount of hydrogen and oxygen, collected from the counter chamber and the photoanode chamber, separately, reached to 5.0 μmol and 2.3 μmol, respectively, under 2 h simulated sunlight irradiation at 1.20V vs. RHE bias without any sacrificial agent. The remarkable performance of the nanocomposite anode owe to the formed heterojunction structure in the nanocomposite, leading to high photoexcited charge transfer and separation.
关键词： Mn3O4,CuWO4,Water splitting,Hydrogen and oxygen production,Photoelectrochemical cell
更新于2025-09-10 09:29:36
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Fabricating Cu, Cu<sub>2</sub>O and Hybrid Cu-Cu<sub>2</sub>O nanoparticles in carbon matrix and exploring catalytic activity of oxygen and hydrogen evolution and green A<sup>3</sup>-coupling reaction
摘要： Hybrid Cu-Cu2O as well as Cu and Cu2O@C nanoparticles (NPs) encapsulated by carbon matrix have been synthesized and bifunctional electrocatalytic activity (OER and HER) and A3 coupling (three components reaction) were explored. Powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), and high resolution transmission electron microscopy (HR-TEM) studies were performed to analyse structure, chemical state, and size of the nanocatalysts. Hybrid Cu-Cu2O@C materials exhibited stronger electrocatalytic activity compared to pure phases whereas pure Cu and Cu2O@C NPs displayed better catalytic activity for A3 coupling reaction. Oxygen and hydrogen evolution reaction (OER and HER) showed enhanced current response (57.8 mA/cm2 and -172 mA/cm2) for hybrid NPs with higher Cu2O ratio. Thus, the present work investigated the role of Cu and Cu2O ratio for fabricating earth abundant cost effective nanocatalysts for OER, HER, and organic chemical transformation.
关键词： Water splitting,A3 coupling,Oxygen evolution reaction,Hydrogen evolution reaction,Cu-Cu2O nanoparticles,Electrocatalyst
更新于2025-09-10 09:29:36
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Design and Comparative Studies of Z-Scheme and Type II Based Heterostructures of NaNbO <sub/>3</sub> /CuInS <sub/>2</sub> /In <sub/>2</sub> S <sub/>3</sub> for Efficient Photoelectrochemical Applications
摘要： Here, we report the fabrication of a new Z-scheme based core/shell/shell heterostructure of NaNbO3/CuInS2/In2S3 (core/shell/shell) for photoelectrochemical (PEC) water splitting and also for degradation of organic pollutants. We have also performed a comparative study with a modified heterostructure of NaNbO3/In2S3/CuInS2 having Type II band alignment. The PEC measurements under visible light irradiation show increased photocatalytic performance for the NaNbO3/CuInS2/In2S3 heterostructures as revealed by a high current density of ～6.72 mA/cm2 at ?1.0 V versus Ag/AgCl and low photocurrent onset potential of ～?110 mV in comparison to the Type II system (～1.63 mA/cm2 and ?180 mV vs Ag/AgCl). Mott?Schottky plots confirmed the n?p?n type heterojunction formation in the NaNbO3/CuInS2/In2S3 heterostructure which reduces the charge carrier recombination (revealed by PL intensity and short lifetime). The Z-scheme based system also exhibits excellent degradation efficiency (～99.6%) of organic pollutants. This work shows that the Z-scheme charge separation mechanism in NaNbO3/CuInS2/In2S3 nanostructures is more efficient than the Type II based on NaNbO3/In2S3/CuInS2.
关键词： core/shell/shell heterostructure,photoelectrochemical water splitting,Type II band alignment,organic pollutants degradation,Z-scheme,NaNbO3/CuInS2/In2S3
更新于2025-09-09 09:28:46
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Recent Advances and Emerging Trends in Photo-Electrochemical Solar Energy Conversion
摘要： Photo-electrochemical (PEC) solar energy conversion offers the promise of low-cost renewable fuel generation from abundant sunlight and water. In this Review, recent developments in photo-electrochemical water splitting are discussed with respect to this promise. State-of-the-art photo-electrochemical device performance is put in context with the current understanding of the necessary requirements for cost-effective solar hydrogen generation (in terms of solar-to-hydrogen conversion efficiency and system durability, in particular). Several important studies of photo-electrochemical hydrogen generation at p-type photocathodes are highlighted, mostly with protection layers (for enhanced durability), but also a few recent examples where protective layers are not needed. Recent work with the widely studied n-type BiVO4 photoanode is detailed, which highlights the needs and necessities for the next big photoanode material yet to be discovered. The emerging new research direction of photo-electrocatalytic upgrading of biomass substrates toward value-added chemicals is then discussed, before closing with a commentary on how research on PEC materials remains a worthwhile endeavor.
关键词： value-added chemicals,hydrogen,photo-electrochemical,water splitting
更新于2025-09-09 09:28:46