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

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 mu mol 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.