Investigation on stability of electroplated-sulfurized CuInS2-based photocathode modified with an In2S3 layer for H2 evolution under various pH conditions

Abstract

We investigated photoelectrochemical water splitting properties of Pt-In2S3/CuInS2 photocathodes from near neutral toward basic condition (pH 6, 9, and 13). Half-cell solar-to-hydrogen (HC-STH) of Pt-In2S3/CuInS2 measured under 0.2 M NaH2PO4 was the highest when the pH of the solution was 13 (4.7% at 0.42 V vs. RHE) with a maximum photocurrent density of 16.3 mA cm-2 (at 0 V vs. RHE) and onset potential of 0.9 V vs. RHE (defined as cathodic photocurrent of 0.1 mA cm-2). However, it suffers from rapid degradation of the photocurrent over the time course when kept at 0 V vs. RHE under constant illumination. On the other hand, the photocathode showed relatively stable photocurrent when measured under near neutral condition (pH 6): HC-STH of 2.85% (at 0.28 V vs. RHE) with a maximum photocurrent density of 16.3 mA cm-2 (at 0 V vs. RHE) and onset potential of 0.72 V vs. RHE were obtained from the photocathode. Passivation using In2S3 oxygen-free can stabilize the photocathode at alkaline pH (pH 13).