Efficient photocatalytic hydrogen evolution of g-C3N4/Vs-SnS2/CdS through a sulfur vacancy-rich SnS2 induced charge storage effect

Abstract

Photocatalytic hydrogen production using semiconductors is one of the most promising routes for sustainable energy production. However, poor electron–hole separation and slow surface reactions of photocatalysts impede their performance. Here, a hierarchical hollow g-C₃N₄/Vs-SnS₂/CdS tandem heterojunction photocatalyst was constructed. For the first time, the charge storage characteristics of S-vacancy-rich SnS₂ in photocatalytic applications were developed. Due to the charge storage properties of Vs-SnS₂, more electrons accumulate on the surface of Vs-SnS₂, which greatly improves the separation efficiency of charge carriers and prolongs the lifetime of charge carriers. The aggregation of electrons leads to the formation of Cd–S–OH chemical bonds, which is beneficial for the adsorption and activation of H₂O. As a result, this catalyst shows an excellent photocatalytic hydrogen evolution rate of 2.3 mmol h⁻¹ g⁻¹. Encouragingly, electron storage signals were detected in the femtosecond transient absorption spectra of heterojunctions, and it was proved that the electrons stored in Vs-SnS₂ could be utilized in the photocatalytic process. This provides new insights into the electron capture and storage process of semiconductors with electron storage properties during photocatalysis.