Integrating Semiconducting Catalyst of ReS₂ Nanosheets into P-Silicon Photocathode for Enhanced Solar Water Reduction

Loading electrocatalysts at the semiconductor–electrolyte interface is one of the promising strategies to develop photoelectrochemical water splitting cells. However, the assembly of compatible and synergistic heterojunction between the semiconductor and the selected catalyst remains challenging. Here, we report a hierarchical p-type silicon (p-Si)/ReS2 heterojunction photocathode fabricated through the uniform growth of vertically standing ReS2 nanosheets (NSs) on a planar p-Si substrate for the solar-driven hydrogen evolution reaction (HER). The laden ReS2 NSs not only serve as a high-activity HER catalyst but also render a suitable electronic band coupled with p-Si into a II-type heterojunction, which facilitates the photoinduced charge production, separation, and utilization. As a result, the assembled p-Si/ReS2 photocathode exhibits a 23-fold increased photocurrent density at 0 VRHE and a 35-fold enhanced photoconversion efficiency compared with the pure p-Si counterpart. The bifunctional ReS2 as a catalyst and a semiconductor enables multi-effects in improving light harvesting, charge separation, and catalytic kinetics, highlighting the potential of semiconducting catalysts integrated into solar water splitting devices.