Visible-Light Photocatalysis Design Using Non-Faceted Semiconductor/Liquid Junctions

Abstract

Photocatalysis has been shown as a promising fuel generation method due to its potential for low cost and high scalability. Narrow-bandgap semiconductors are good candidates for photocatalytic fuel production because of their high light absorbance and quantum efficiency; however, the instability and the small driving force for charge separation inhibit their broad utilization for solar fuel generation. Because of these factors, researchers have been struggling with making a narrow-band-gap photocatalytic panel. To surmount these limitations, we proposed a surface design strategy to manipulate the electrons and holes separation process without any facets design and build-in junction. Our modeling study shows that charge separation can be controlled by surface coating and catalyst design. The doping level of the semiconductors and the geometry of catalysts are the most important factors for charge separation efficiency. Based on this principle, we developed conformal coatings with attached nanoscale catalysts enabling planar III-V semiconductors for overall water splitting. With the atomic layer deposition, the coating of high conductivity was grown on the semiconductors to protect them and tune their band edge position for the desired fuel generation reactions. With E-beam lithography, the cathodic and anodic catalysts were designed to optimize the charge separation processes. Using these techniques, we fabricated GaP/(Ti,M)Ox/Ir/Rh@CrOx and InGaP/GaN/IrOx/Rh@CrOx panels and successfully achieved hydrogen and oxygen coevolution. Figure 1