Photocatalytic water splitting on the CuInS2 photoelectrodes: Effects of co-electrodeposition mechanisms on the photoelectrochemical properties

Abstract

Copper indium sulfide (CuInS2, CIS) was fabricated by co-electrodeposition (co-ED) of the Cu-In (CI) alloy on the Mo-electrode, followed by sulfurization in the presence of solid sulfur. The morphology, crystal structures and In/Cu compositions of CIS were found to depend on the preparation conditions of the CI, i.e., the solution concentration, applied potential and amount of Coulomb charge. For the mechanism of CI formation, the copper species were preferentially deposited on the Mo electrode in their initial state, and subsequently the indium species were deposited on the Cu layer by the effects of the concentration gradient at the electrode interface. Furthermore, the optimized CIS possessed a chalcopyrite structure with an In/Cu ratio of 1.0 having a band-gap at ca. 1.5 eV. The Pt-In2S3/CIS photoelectrode was applied for photocatalytic water splitting and it demonstrated high photoelectrochemical (PEC) water splitting to evolve H2 (50 μmol h−1 cm−2) with a Faradic efficiency of 83.4% at + 0.1 V vs. RHE. The co-ED method, thus, enabled the facile fabrication of CI, and the prepared CIS clearly exhibited promising activity as a photo-absorber for PEC water splitting.