Design of a Silicon Photocatalyst for High-Efficiency Photocatalytic Water Splitting

Metallurgical silicon was studied for photocatalytic H₂ evolution activity. It has been found that metallurgical silicon with large particle size (above 800 nm) possesses poor photocatalytic activity because of the deteriorating photoelectric performance of the low-purity silicon. After size reduction (around 400 nm) and metal nanoparticle decoration, the photocatalytic performance was significantly enhanced to 1003.3 μmol·g^–1·h^–1. However, the photocatalytic performance of the Cu-, Ag-, and Pt-decorated silicon is degraded with the increase of time. Moreover, the degradation is independent of the metal. Electrochemical test and X-ray photoelectron spectroscopy suggested that the Mott–Schottky effect in the metal–silicon contact should be responsible for the degradation. After forming a heterojunction by vulcanizing the Ag-decorated silicon, the degradation was suppressed. Upgradation of the metal–silicon contact to form a heterojunction was a promising way to suppress the degradation and retain the high photocatalytic performance.