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Self-constructed facet junctions on hexagonal CdS single crystals with high photoactivity and photostability for water splitting
摘要： Crystal facets engineering of semiconductor catalysts with different exposed facets has been proven as a versatile approach to enhance their photocatalytic performance. Herein, for the first time, a facet-junction engineered hexagonal CdS single crystal with exposing {0001} and {10 0} facets was synthesized by hydrothermal reaction via adjusting the molar ratio of S2-/Cd2+ precursor. The co-exposed {0001} and {10 0} facets on hexagonal CdS single crystals with continuous band bending and well-defined epitaxial interfaces showed highly efficient visible-light-induced H2 evolution. The maximum photocatalytic H2 production rate of 24.33 mmol h?1g?1 is obtained over the facet-junction engineered hexagonal CdS-5 single crystals with an apparent quantum efficiency of 11.18% at 470 nm, which is about 5.27 times greater than CdS-1 nanoparticles. Also, superior photostability is also achieved, even after 25 consecutive cycles during 100 h light irradiation keeping impregnated in strong alkaline sacrificial agent beyond 20 days, the initial photoactivity is still remained. The enhanced photocatalytic H2 evolution activity and photostability can be ascribed to the type-II band alignment between the co-exposed {0001} and {10 0} facets that significantly promoted the separation rate of photo-generated electrons and holes. And the small amount of sulfur vacancies are also benefit for the photocatalytic hydrogen evolution activity of CdS-5. The time-resolved fluorescence (TRPL) decay and photoelectrochemical test further proved the effective spatial charge separation. This work provides a feasible and simple strategy for designing of facet-junction engineered CdS single crystals with highly efficient photocatalytic activity and unprecedented photostability.
关键词： hexagonal CdS single crystals,{0001} facets,photocatalytic hydrogen evolution,facet junction
更新于2025-09-10 09:29:36
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Au decorated hollow ZnO@ZnS heterostructure for enhanced photocatalytic hydrogen evolution: The insight into the roles of hollow channel and Au nanoparticles
摘要： A new type of Au nanoparticles (NPs) decorated hollow flower-like ZnO@ZnS (HZOS) heterostructure (HS) is elaborately designed as efficient photocatalyst for water splitting application. The optimal Au decorated HZOS exhibits a high hydrogen generation rate of 569.81 μmol/h (10 mg of catalyst), which is 345, 374 and 11 times higher than that of pristine ZnO (1.65 μmol/h), ZnS (1.52 μmol/h) and ZnO@ZnS (51.7 μmol/h), respectively. Furthermore, its apparent quantum efficiency reaches to 25.47 % at the wavelength of 365 nm. The significantly enhanced H2 evolution can be attributed to the synergistic effects from the hollow channel structure and the deposited Au NPs. The hollow channel creates a new migration pathway where charge carriers can transfer towards the hollow channel in addition to the outer surface of the photocatalyst, thus significantly reducing the migration distance of charge carriers, suppressing the recombination of photogenerated electrons and holes, and reducing their transfer resistance. The decoration of Au NPs at the interface between ZnO and ZnS not only facilitates the directional migration of charge carriers because of the formation of Schottky barrier, but also works as electron shuttles to form a Z-scheme transfer process, effectively promoting the separation and migration of charge carriers.
关键词： photocatalysis,heterostructure,hydrogen evolution,Z-scheme,hollow channel
更新于2025-09-10 09:29:36
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Low-Temperature Wafer-Scale Growth of MoS2-Graphene Heterostructures
摘要： In this study, we successfully demonstrate the fabrication of a MoS2-graphene heterostructure (MGH) on a 4-inch wafer at 300 oC by depositing a thin Mo film seed layer on graphene followed by sulfurization using H2S plasma. By utilizing Raman spectroscopy and high-resolution transmission electron microscopy, we have confirmed that 5–6 MoS2 layers with a large density of sulfur vacancies are grown uniformly on the entire substrate. The chemical composition of MoS2 on graphene was evaluated by X-ray photoelectron spectroscopy, which confirmed the atomic ratio of Mo to S to be 1:1.78, which is much lower than the stoichiometric value of 2 from standard MoS2. To exploit the properties of the nanocrystalline and defective MGH film obtained in our process, we have utilized it as a catalyst for hydrodesulfurization and as an electrocatalyst for the hydrogen evolution reaction. Compared to MoS2 grown on an amorphous SiO2 substrate, the MGH has smaller onset potential and Tafel slope, indicating its enhanced catalytic performance. Our practical growth approach can be applied to other two-dimensional crystals, which are potentially used in a wide range of applications such as electronic devices and catalysis.
关键词： PECVD,graphene,large-scale,heterostructure,hydrogen evolution reaction,MoS2
更新于2025-09-10 09:29:36
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Spatial separation of charge carriers in Nb2O5 nanorod superstructures for enhanced photocatalytic H2 production activity
摘要： Monoclinic Nb2O5 nanorod superstructures were first synthesized by a facile yet effective hydrothermal route using Sn2Nb2O7 nanoparticles as the precursor. These unique Nb2O5 nanorod superstructures assembled by small nanorods facilitate the spatial separation of photogenerated charge carriers, thus leading to improved photocatalytic H2 production activity in methanol aqueous solution under ultraviolet light irradiation, which is about 151 times higher than that of commercial Nb2O5 powders.
关键词： H2 evolution,Niobate oxide,Nanorod,Photocatalysis,Superstructures
更新于2025-09-10 09:29:36
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Controllable synthesis of P-doped MoS2 nanopetals decorated N-doped hollow carbon spheres towards enhanced hydrogen evolution
摘要： In order to construct the molybdenum disulfide (MoS2) hybrid nanostructure with enhanced conductivity and more active sites towards electrocatalytic hydrogen evolution reaction (HER), hierarchical P-doped MoS2 nanopetals decorated N-doped hollow carbon spheres (N-C@P-MoS2) core-shell structures were synthesized via calcination and hydrothermal synthesis. N-C@P-MoS2 with optimized loadings exhibited favorable HER activities with low onset overpotential (117 mV), small Tafel slopes (68 mV/dec), and fine stability compared with pure MoS2 nanosheets and all undoped samples. This is largely ascribed to the synergy of MoS2 and carbon in the rational hierarchical structures, as well as the modified electronic structure with improved conductivity, increased active sites by virtue of N and P doping. Furthermore, P-doped MoS2 nanosheets were encapsulated in carbon spheres (N-C/P-MoS2 (inside)) by controlling the dropping rate of adding MoS2 precursors. As the active sites were hampered, it is found that the N-C/P-MoS2 (inside) revealed poor HER performance compared with the core-shell counterparts. The results demonstrate that the fabrication of hierarchical MoS2/carbon composites with the synergy of structural (morphology and content) and electronic (active sites and conductivity) effects induced by various nonmetal doping pave the way for enhanced electrocatalytic HER activities.
关键词： Hollow carbon sphere,structural and electronic effect,Nonmetal doping,Hydrogen evolution reaction,Molybdenum disulfide
更新于2025-09-10 09:29:36
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Wireless Addressing of Free-Standing MoSe2 Macro- and Microparticles by Bipolar Electrochemistry
摘要： Doping of a transition metal dichalcogenide deposited onto a conducting surface acting as bipolar electrode was recently reported. Here, free-standing macro- and microscale transition metal dichalcogenide substrates are successfully employed as effective bipolar electrodes without the need of using an additional conducting support. This is first demonstrated by achieving site-selective bipolar electrodeposition of several metals such as gold, silver, copper and nickel on macroscale MoSe2 substrates (typically 1 cm in size). Also, the superior efficiency of MoSe2 compared to a carbon substrate towards hydrogen evolution reaction, well-known in conventional electrochemistry, is demonstrated in the bipolar electrochemistry configuration. Such electrocatalytic properties can be advantageously used by combining this reduction with a given oxidation reaction in order to ease the electrochemical coupling. Also, as a wireless technique, bipolar electrochemistry enables the simultaneous addressing of large ensembles of bipolar electrodes with a single pair of driving electrodes. Therefore, in a bulk experiment, a suspension composed of thousands of individual MoSe2 microparticles (with a typical size of 20-80 μm) that are addressed simultaneously, is employed to significantly accelerate an electrolysis. Amplex? Red was selected as an oxidizable organic model dye. Such an electrolysis occurs on the timescale of several seconds which is definitely not achievable by addressing a single macroscale MoSe2 bipolar electrode. This performance is due to the collective behavior of the ensemble of MoSe2 bipolar electrodes because the oxidation process occurs simultaneously at each individual anodic pole.
关键词： electrodeposition,MoSe2,bipolar electrochemistry,transition metal dichalcogenide,hydrogen evolution reaction
更新于2025-09-10 09:29:36
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Restoration of stable voltage in an isolated hybrid solar power system with combined JAYA-DE algorithm
摘要： This work discusses the implementation of JAYA-DE algorithm with Static Var Compensator for optimum voltage control through Reactive Power compensation inside solar based hybrid power system.The stability aspect of isolated solar based hybrid power system is enhanced through compensation of the reactive power by optimized SVC and are further analyzed with different stability criterion. The dynamic performance of the new hybrid technique under intermittent wind power input and variable load show superiority over the conventional control methods.
关键词： Reactive power compensation,JAYA optimization voltage stability,Differential evolution algorithm,HSPS
更新于2025-09-10 09:29:36
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Photocatalytic performance of K2Ti6O13 whiskers to H2 evolution and CO2 photo-reduction
摘要： K 2 Ti 6 O 13 whiskers were synthesized by conventional sol-gel method, sono-chemical assisted and microwave assisted sol-gel method in order to obtain catalysts with different particle sizes and to modify their optical, textural and electrochemical properties. These modifications improved their photocatalytic activity for H 2 evolution and CO 2 photo-reduction. Long K 2 Ti 6 O 13 whiskers prepared by ultrasound assisted sol-gel method are the most active photocatalysts for the hydrogen evolution reaction using pure water as reactant (U-SG, 10,065 μmol g ?1 ). In contrast, an opposite behavior was observed using a mixture of ethanol-water, where the highest activity was achieved by the shortest and less crystalline K 2 Ti 6 O 13 whiskers (C-SG, h32871 μmol g ?1 ). In case of CO 2 photo-reduction, long whiskers that were also prepared by the sono-chemical assisted sol-gel method were the most active to transform CO 2 to formaldehyde, methane, methanol and hydrogen. The E FB value of this catalyst is located very close to the potential for formaldehyde production and favors the selectivity to this organic product.
关键词： Sol-gel,Whiskers,Hydrogen evolution,K 2 Ti 6 O 13,CO 2 reduction
更新于2025-09-10 09:29:36
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Influence of Cr doping on the oxygen evolution potential of SnO2/Ti and Sb-SnO2/Ti electrodes
摘要： Oxygen evolution potential is the determining factor affecting the anode efficiency of the wastewater treatment process. In this study, we focus on increasing oxygen evolution potential of Cr-SnO2/Ti and Cr-Sb-SnO2/Ti electrodes with the pyrolytic method. XRD, SEM and XPS techniques had been applied to characterize the microstructures and chemical compositions of the samples. Electrochemical measurements had been performed to evaluate the oxygen evolution potential as a criterion of the wastewater treatment efficiency. The results show that co-doping of Sb and Cr improved the crystallinity and grain size of SnO2 coating, and Cr existed in the form of Cr(Ⅲ) valence states. The Cr doping treatment improved the electronic conductivity and the electrocatalytic activity of the electrodes. DFT calculation of the band-structure indicates Cr doped SnO2 had a superior electrical conductivity, where Cr atom acts as an acceptor providing vacancies for electron transportation. The DOS diagrams reveal the Cr doped SnO2 showing a p-type conductivity which would subsequently influence the built-in potential on metal-semiconductor interface. We proposed the mechanism of the increase of oxygen evolution potential is the doping of Cr expands the built-in potential.
关键词： Cr doping,oxygen evolution potential,DFT,wastewater treatment
更新于2025-09-10 09:29:36
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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