Construction of CoSe₂/WO₃@Si Multiheterojunctions for Efficient Photoelectrochemical Water Splitting

Developing efficient photoanodes for photoelectrochemical (PEC) water splitting is crucial for solar-to-hydrogen energy conversion. Monocrystalline silicon, as a photoelectrode material, has limitations of high surface reflectivity, easy formation of oxide passivation, and instability in aqueous solutions. Herein, flower cluster CoSe₂ and lamellar WO₃ obtained via the solvothermal method are coated onto the surface of textured silicon by chemical bath deposition to prepare a multiheterojunction structured photoanode. The as-prepared CoSe₂/WO₃@Si-9 photoelectrode exhibits a desirable photocurrent of 10.1 mA cm^-2 at 1.23 V_RHE under simulated solar irradiation (AM 1.5G, 100 mW cm^-2) in comparison to WO₃@Si (0.49 mA cm^-2) and CoSe₂@Si (1.56 mA cm^-2) and excellent stability over 10 h. The improved PEC hydrogen evolution performance comes from the synergistic effect of the multiple heterojunctions of CoSe₂/WO₃@Si composites. The synergistic effect can improve the separation efficiency of photogenerated electron-hole pairs while maintaining strong redox capability. The CoSe₂/WO₃@Si-9 photoanode exhibits a high photocurrent density and stability, making it a promising candidate for practical applications.