Covalency-aided electrochemical CO2 reduction to CO on sulfide-derived Cu–Sb

Abstract

p-Block dopants like sulfur have been shown to break scaling relations in the electrocatalytic CO₂ reduction reaction (CO₂RR) by providing alternative binding sites with altered *CO binding energy. However, most sulfide-derived catalysts reported to date tend to produce formate or hydrogen during the CO₂RR by shifting the reaction pathway away from C-bound intermediates. In this work, we discovered highly selective CO production on a bimetallic Cu–Sb–S derived catalyst. The high CO selectivity is in contrast with the individual control samples of CuS_x and SbS_x that demonstrate a preference towards the formate product. Interestingly, different starting phases and atomic ratios of Cu–Sb–S affect the CO₂RR selectivity. Post-catalysis characterization coupled with DFT calculations indicates that the key enabler towards CO formation is the substitution of Sb sites with sulfur which improves *COOH binding relative to *CO, breaking scaling relations and facilitating subsequent CO (g) formation. The highest CO production of FE_CO = 80.5% was observed on the tetrahedrite Cu–Sb–S-derived sample at −1.0 V RHE with 37.6 mA cm⁻² geometric partial current density.