Non-metal atom modified SnS2 sheet for CO2 photoreduction with significant activity and selectivity improvements: A first-principles study

Abstract

Photocatalytic CO2 reduction suffers from low activity and poor product selectivity, seriously limiting its further application. Here, by means of density functional theory, we investigated the structural and catalytic properties of non-metal atoms X (X = B, C, N, and O) anchored at S vacancy site of SnS2 monolayer denoted as X/Sv-SnS2. The HSE06 result shows that both the band gap and band edge positions of X/Sv-SnS2 substrates are quite suitable for CO2 photoreduction. Interestingly, the adsorption strength of CO2 can be linearly enhanced with the decreasing non-metal atoms X from O to B, and the corresponding value ranges from −0.25 to −1.23 eV. Particularly, the diversity of non-metal atoms X generates completely different preference of CO2 reduction products according to the Gibbs free energy change. Whereas O, C, and B/Sv-SnS2 separately favor to form CO, HCOOH, and CH4 products, with remarkably low energy barrier of 1.07 eV, 0.58 eV, and 1.04 eV, respectively. These peculiar activity and selectivity properties mainly stem from the unique adsorption behavior and frontier orbital interaction between non-metal atoms X and intermediates. Our findings strongly suggest that cooperation of non-metal atoms and intrinsic defect could offer an exciting opportunity to design high activity and selectivity photocatalysis for CO2 reduction.