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Microfluidic-enhanced 3-D photoanodes with free interfacial energy barrier for photoelectrochemical applications
摘要： The sluggish reaction kinetics and poor interfacial mass transfer seriously limit the industrial applications of planar photoelectrocatalytic devices. Here, the principle of 3-D flow-through photoanodes with free interfacial barrier for electron transfer and microfluidic channels for reactant transportation was demonstrated. Owing to the epitaxial growth of anisotropic ZnO nanorods with internal electrostatic field onto carbon cloth (CC), the spatial separation of photo-induced charge carriers was realized. Experimental characterizations confirmed the formation of Schottky-barrier-free interface with low electrical resistance for electron transfer, resulting in the significantly decreased onset potential. Compared to traditional planar FTO/ZnO photoanodes, flow-through CC/ZnO photoanodes exhibited 4 times (for Rhodamine B) and 3 times (for bisphenol A) higher degradation kinetics. Fluid dynamics simulation suggested that the flow-through mode greatly enhanced the microscale velocity magnitude and the mass transfer of reactants. Thus, this work presents an ideal platform for the design of 3-D microfluidic-enhanced system for photoelectrochemical applications.
关键词： Mass transfer,Flow-through photoanodes,Internal electrostatic field,Schottky barrier,Photoelectrochemical
更新于2025-09-04 15:30:14
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Atomic layer deposited TiO <sub/>2</sub> -IrO <sub/>x</sub> alloys enable corrosion resistant water oxidation on silicon at high photovoltage.
摘要： We synthesized by atomic layer deposition (ALD) TiO2-IrOx alloys that enable high photovoltages and catalyze water oxidation on silicon metal-insulator-semiconductor (MIS) photoanodes. The ratio of TiO2 to IrOx was precisely controlled by varying the number of ALD cycles for each precursor. Silicon with a 2 nm surface SiO2 layer was coated with TiO2-IrOx alloys ranging in composition from 18-35% iridium relative to the sum of titanium and iridium concentrations. IrOx catalyzed oxygen evolution and imparted a high work function to the TiO2-IrOx alloys, enabling photovoltages during water oxidation that exceeded 600 mV. TiO2 imparted stability and inhibited corrosion of the underlying silicon light absorber. After annealing in forming gas (5% H2 / 95% N2), TiO2-IrOx alloys were stable for 12 hours of continuous water oxidation in 1 M H2SO4. Key properties of the MIS junction affecting electrochemical operation were also extracted by electrochemical impedance spectroscopy. This work demonstrates that alloying by ALD is a promising approach for designing corrosion resistant Schottky contacts with optimized electronic and materials properties for catalyzed, solar driven water oxidation.
关键词： photovoltage,water oxidation,TiO2-IrOx alloys,Atomic layer deposition,corrosion resistance,silicon photoanodes
更新于2025-09-04 15:30:14
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Metal oxide/(oxy)hydroxide overlayers as hole collectors and oxygen evolution catalysts on water splitting photoanodes
摘要： Solar-water-splitting provides a mechanism to convert and store solar energy in the form of stable chemical bonds. Water-splitting systems often include semiconductor photoanodes, such as n-Fe2O3 and n-BiVO4, which use photogenerated holes to oxidize water. These photoanodes often exhibit improved performance when coated with metal-oxide/(oxy)hydroxide overlayers that are catalytic for the water oxidation reaction. The mechanism for this improvement, however, remains a controversial topic. This is, in part, due to a lack of experimental techniques that are able to directly track the flow of photogenerated holes in such multicomponent systems. In this Perspective we illustrate how this issue can be addressed by using a second working electrode to make direct current/voltage measurements on the catalytic overlayer during operation in a photoelectrochemical cell. We discuss examples where the second working electrode is a thin metallic film deposited on the catalyst layer, as well as where it is the tip of a conducting atomic-force-microscopy probe. In applying these techniques to multiple semiconductors (Fe2O3, BiVO4, Si) paired with various metal-(oxy)hydroxide overlayers (e.g. Ni(Fe)OxHy and CoOxHy), we found in all cases investigated that the overlayers collect photogenerated holes from the semiconductor, charging to potentials sufficient to drive water oxidation. The overlayers studied thus form charge-separating heterojunctions with the semiconductor as well as serve as water-oxidation catalysts.
关键词： solar-water-splitting,water oxidation reaction,semiconductor photoanodes,photoelectrochemical cell,metal-oxide/(oxy)hydroxide overlayers
更新于2025-09-04 15:30:14