Construction of NiSe2/WO3@SiMPs Heterojunction with Enhanced Photoelectrochemical Performance

Monocrystalline silicon, despite its widespread use as a photoelectrode material, is hindered by inherent drawbacks, such as high surface reflectivity, vulnerability to oxide passivation, and instability in aqueous electrolytes. To address these, a micropyramidal texture is fabricated on the silicon surface via wet chemical etching. A heterojunction photoanode was constructed by sequentially depositing NiSe2 and WO3 onto the textured silicon using chemical bath deposition, forming NiSe2/WO3@SiMPs. The photoanode demonstrates optimal photoelectrochemical performance at a NiSe2 to WO3 mass ratio of 9:1. Under simulated solar illumination (AM 1.5 G, 100 mW cm−2), it achieves a photocurrent of 5.62 mA cm−2 at 1.23 V (vs. RHE), and a maximum photocurrent of 13.6 mA cm−2 at 2.0 V (vs. RHE), markedly outperforming the individual components NiSe2@SiMPs (8.23 mA cm−2) and WO3@SiMPs (0.95 mA cm−2) at 2.0 V (vs. RHE). Electrochemical impedance spectroscopy (EIS) results show a markedly lower charge transfer resistance (Rct) for the NiSe2/WO3@SiMPs (8.16 Ω) compared to the single-phase counterparts NiSe2@SiMPs (121.48 Ω) and WO3@SiMPs (902.23 Ω), indicating more efficient charge separation. In addition, the photocurrent remains steady for about 10 h without significant degradation. This work presents a promising strategy for improving the photoelectrochemical water splitting efficiency of silicon-based photoelectrodes through rational heterostructure engineering.