Direct Utilization of a HF-Treated Si Photocathode for Efficient Hydrogen Production

Silicon (Si)-based photocathodes are generally considered as ideal materials for photoelectrochemical (PEC) hydrogen production. The fabrication of Si-based photocathodes usually requires hydrofluoric acid (HF) treatment to remove the oxide layer first, and H-dangling bonds can be formed inevitably on the surface of Si at the same time. However, the impacts of Si–H bonds in the PEC reaction are usually ignored. Here we report that the enriched H-dangling bonds at the solid–liquid interface play multiple roles in PEC hydrogen production, which can both efficiently collect photogenerated electrons from Si and accelerate the kinetics of the hydrogen evolution reaction at the interface. Furthermore, the coupling mechanism of H₂ production triggered by H-dangling bonds significantly improves the efficiency of the PEC process. This work demonstrates that the HF-treated Si photocathode can be directly used for efficient hydrogen production, which will undoubtedly force a new phase in the study of Si-based photocathodes.