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

The acidic CO 2 reduction reaction (CO 2 RR) offers a promising approach to mitigate CO 2 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 (C 2+ ) products. In this work, we proposed a palladium (Pd) doping strategy in a copper (Cu)-based catalyst to stabilize polarized Cu 0 -Cu + sites, thus enhancing the C C coupling step during the CO 2 RR 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 (O Sub ), preserving the polarized Cu 0 -Cu + active sites, and reducing the energy barrier of C C coupling. The Pd-doped Cu/Cu 2 O catalyst exhibited a peak Faradaic efficiency (FE) of 64.0% for C 2+ products with a corresponding C 2+ partial current density of 407.1 mA∙cm −2 at −2.18 V versus a reversible hydrogen electrode, a high CO 2 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 CO 2 performances in acidic environments with higher carbon conversion efficiencies.