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.

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