A High-Performance Si-Based Photocathode Enhanced by Spatial Confinement Strategy for Photoelectrochemical Hydrogen Production

Metallic materials (such as Ti, Pt, and Ag) modified on silicon-based photocathodes exhibit strong light reflection, which significantly hinders light absorption by the underlying silicon (Si), thereby limiting the efficiency of Si-based photocathodes. Herein, a high-performance Si-based photocathode is designed by spatial confinement strategy. The Pt cocatalysts are confined to the Ti protective layer at the top of the pyramid, which serve as catalytic active sites for the photoelectrochemical hydrogen evolution reaction. The other regions are covered by the SiO 2 layer, which allow incident light to penetrate and be absorbed by the underlying Si. This design effectively suppresses parasitic light absorption, thereby enhancing the photoelectrochemical performance of the Si-based photocathodes. In addition, the SiO 2 layer and the Ti layer can protect Si from being corroded by the electrolyte. Under 1 sun (AM 1.5G) illumination, the OP-Si/SiO 2 /Ti/Pt photocathode exhibits an onset potential of 0.415 V vs reversible hydrogen electrode (RHE) and a photocurrent density of −13.93 mA cm –2 at 0 V vs RHE, which is significantly superior to the control photocathode (OP-Si/Ti/Pt). This work provides a promising avenue to develop highly efficient Si-based photocathodes.