A highly efficient 3D/0D CdIn2S4/Cu2O photoanode with a p–n type heterojunction for boosted photoelectrochemical water splitting under visible light irradiation

Abstract

Cadmium indium sulfide (CdIn₂S₄) is a promising photoanode material owing to its narrow bandgap and appropriate band edge position. However, the H₂ production performance of photoelectrochemical (PEC) water splitting is still limited by the rapid recombination and poor transport ability of charge carriers. To solve these issues, we prepared CdIn₂S₄/Cu₂O heterostructures for the first time through simple hydrothermal, successive ion layer adsorption reaction (SILAR), and vacuum annealing processes. The photocurrent of the CdIn₂S₄/Cu₂O heterostructure reached a maximum of 6 mA cm⁻² at 0 V vs. Ag/AgCl, much higher than that of the pure CdIn₂S₄ substrate. At the same time, the H₂ production rate was also significantly increased after loading Cu₂O, reaching 144.72 μmol cm⁻² h⁻¹, which is 2.9 times that of the CdIn₂S₄ substrate. We characterized the heterostructure and analyzed the reasons for its performance improvement through X-ray photoelectron spectroscopy (XPS), Mott–Schottky (M–S) curves, Tauc diagrams, and 3D finite-difference time-domain (FDTD) simulations. Through analysis, the significant improvement in PEC performance is attributed to the construction of heterostructures, which enhances the original light absorption capacity. At the same time, the synergistic effect of type II and p–n junctions greatly improves its charge transfer efficiency and separation efficiency. This study also provides a reference strategy for designing photoanodes to achieve PEC performance from the perspectives of light energy utilization and interface energy engineering.