Doping palladium with tellurium for the highly selective electrocatalytic reduction of aqueous CO₂ to CO

Designing highly selective and energy-efficient electrocatalysts to minimize the competitive hydrogen evolution reaction in the electrochemical reduction of aqueous CO₂ remains a challenge. In this study, we report that doping Pd with a small amount of Te could selectively convert CO₂ to CO with a low overpotential. The PdTe/few-layer graphene (FLG) catalyst with a Pd/Te molar ratio of 1 : 0.05 displayed a maximum CO faradaic efficiency of about 90% at -0.8 V (vs. a reversible hydrogen electrode, RHE), CO partial current density of 4.4 mA cm^-2, and CO formation turnover frequency of 0.14 s^-1 at -1.0 V (vs. a RHE), which were 3.7-, 4.3-, and 10-fold higher than those of a Pd/FLG catalyst, respectively. Density functional calculations showed that Te adatoms preferentially bind at the terrace sites of Pd, thereby suppressing undesired hydrogen evolution, whereas CO₂ adsorption and activation occurred on the high index sites of Pd to produce CO.