Fabrication of Pt/In2S3/CuInS2 Thin Film as Stable Photoelectrode for Water Splitting under Solar Light Irradiation

Abstract Hydrogen has been expected as a new energy carrier for realizing low carbon society. This paper demonstrates H2 production from water splitting for development of artificial photosynthesis on the copper indium sulfide (CuInS2) electrodes. The photoelectrode was fabricated by electrodeposition (ED) of Cu and In metallic precursors on Mo-coated glass, followed by sulfurization under sulfur (S) vapor environment instead of H2S gas. In order to improve surface properties, the CuInS2 surface was modified with In2S3 by the chemical bath deposition (CBD). The Pt particles as a co-catalyst for proton reduction were, then, photo-electrochemically deposited on the CuInS2 or In2S3/CuInS2 electrodes. They exhibited photo-electrochemical (PEC) water splitting in 0.1 M Na2SO4 aqueous solution to produce H2, of which the efficiency is in the order of: Pt-In2S3/CuInS2 > Pt-CuInS2 >> CuInS2. The half-cell solar-to-hydrogen (HC-STH) of 0.7 % with almost 100% Faraday efficiency was obtained on the Pt-In2S3/CuInS2 photoelectrode. High photoelectrochemical property is attributed to the band-bending of p-n homo-junction between CuInS2 and In2S3.