One-pot molten-salt construction of channels for hole transport and mass transfer over CoS2 nanocubes for visible-light-driven CO2 reduction

Abstract

The photocatalytic reduction of CO₂ into value-added chemicals is of great significance for the utilization of carbon resources, but it also faces the problem of low solar energy efficiency and inefficient charge separation. Herein, a CuSCN-loaded CoS₂ photocatalyst was prepared via a one-pot molten-salt method, and the optimal CO generation rate could reach 289.8 μmol g⁻¹ h⁻¹ (selectivity 92.0%), approximately 32 times that of bare CoS₂ under a visible-light excitation of λ ≥ 420 nm. In situ X-ray photoelectron spectroscopy (XPS) results indicate that CuSCN acts as a hole acceptor, and photoelectrochemical tests and density functional theory (DFT) calculations demonstrate that CuSCN/CoS₂ has higher efficiency in the separation and transfer of photogenerated carriers than CoS₂. CuSCN was proved to be a strong carrier for CO₂ mass transfer through Brunauer–Emmett–Teller (BET) physical adsorption. Mechanistic studies show that CuSCN/CoS₂ is more conducive to the conversion of adsorbed CO₂ into the key reactive intermediate *COOH, for which the Co sites of CuSCN/CoS₂ exhibit a lower formation energy, in comparison with CoS₂ and CuSCN alone. As such, the combined action of CuSCN/CoS₂ was a synergistic effect that enhances CO₂ chemisorption and hole transfer, resulting in increased photocatalytic activity for CO₂ reduction.