Pd-induced polarized Cu0-Cu+ sites for electrocatalytic CO2-to-C2+ conversion in acidic medium

The acidic CO2 reduction reaction (CO2RR) offers a promising approach to mitigate CO2 reactant loss and carbonate deposition, which are challenging issues in alkaline or neutral electrolytes. However, the hydrogen evolution reaction (HER) competes in the proton-rich environment near the catalyst surface as a side reaction, reducing the energy efficiency of generating multi-carbon (C2+) products. In this work, we proposed a palladium (Pd) doping strategy in a copper (Cu)-based catalyst to stabilize polarized Cu0-Cu+ sites, thus enhancing the C  C coupling step during the CO2RR while suppressing HER. At an optimal doping ratio of 6 %, the Pd dopants were well dispersed as single atoms without aggregation, allowing for the stabilization of subsurface oxygen (OSub), preserving the polarized Cu0-Cu+ active sites, and reducing the energy barrier of C  C coupling. The Pd-doped Cu/Cu2O catalyst exhibited a peak Faradaic efficiency (FE) of 64.0 % for C2+ products with a corresponding C2+ partial current density of 407.1 mA∙cm−2 at − 2.18 V versus a reversible hydrogen electrode, a high CO2 single-pass conversion efficiency (SPCE) of 73.2 %, as well as a high electrochemical stability of ∼ 150 h at industrially relevant current densities, thus suggesting a potential approach for tuning the electrocatalytic CO2 performances in acidic environments with higher carbon conversion efficiencies.