Chemical Bond-Modulated Interfacial Energy Band Structures of Heterojunctions for Efficient Photoelectrochemical Water Splitting

Abstract

Understanding the interfacial interaction of a nanostructure heterojunction and improving the efficiency of photoanodes are of great significance to develop photoelectrochemical (PEC) water splitting. Herein, taking BiVO4 and Bi2S3 as model materials, we investigate the modulation effect of a chemical bond at the heterojunction interface on the energy band structure. A BiVO4/Bi2S3 heterojunction is favorably constructed by a convenient chemical technique of successive ionic layer absorption and reaction (SILAR) method. We find that a Bi–O chemical bond is reasonably introduced at the BiVO4 and Bi2S3 interface, which is different from the physical contact heterojunction of BiVO4/Bi2S3(DC). Experimental and theoretical studies reveal that the Bi–O bond at the heterojunction interface distinctly downshifts the Fermi level of the BiVO4 surface and reverses the bending direction of the interfacial band from the former type II structure to a direct Z-scheme structure. Due to the excellent charge separation efficiency and high redox potential, the heterojunction of BiVO4/Bi2S3 (SILAR) exhibits a significantly raised photocurrent density of 2.71 mA cm–2 at 1.23 VRHE, 11.29 times higher than that of BiVO4/Bi2S3(DC). This study emphasizes the modulation effect of interfacial chemical bonds in the fabrication of heterojunctions and provides a reference to construct high-activity photoanodes for PEC water splitting.