Interfacial electric field of CdIn2S4/CuS heterostructure induced S-scheme charge transfer for efficient photoelectrochemical water splitting

Currently, the two predominant heterojunction types, namely type II and S-scheme heterojunctions, are extensively employed in photoelectrochemical (PEC) water splitting for hydrogen production. However, type II heterojunctions suffer from the drawback of diminished oxidation-reduction capability. In this work, S-scheme CdIn₂S₄/CuS (CIS/CuS) heterojunction nanoblocks (NBs) photoanode is constructed for the first time by a hydrothermal and the successive ionic layer adsorption and reaction (SILAR) methods. The heterojunction achieves a photocurrent density of up to 4.0 mA/cm² at 0 V vs. Ag/AgCl, 2.37 times that of the pure CIS NBs photoanode. X-ray photoelectron spectroscopy (XPS), Tauc plots, Mott-Schottky (M − S) tests and density functional theory (DFT) calculations reveal the formation of S-scheme band structure between the interface of CIS and CuS. As a result, the significantly enhanced PEC water splitting performance of CIS/CuS NBs photoanode is attributed to the superior light absorption ability of CuS and the effective charge separation achieved by S-scheme band structure between the interface of CIS and CuS. This work also provides new ideas and strategies for designing efficient S-scheme heterostructures for efficient PEC water splitting.