Boosting Activity and Selectivity of CO2 Electroreduction by Pre‐Hydridizing Pd Nanocubes

Abstract The electrochemical CO 2 reduction reaction (CO 2 RR) to syngas represents a promising solution to mitigate CO 2 emissions and manufacture value‐added chemicals. Palladium (Pd) has been identified as a potential candidate for syngas production via CO 2 RR due to its transformation to Pd hydride under CO 2 RR conditions, however, the pre‐hydridized effect on the catalytic properties of Pd‐based electrocatalysts has not been investigated. Herein, pre‐hydridized Pd nanocubes (PdH 0.40 ) supported on carbon black (PdH 0.40 NCs/C) are directly prepared from a chemical reduction method. Compared with Pd nanocubes (Pd NCs/C), PdH 0.40 NCs/C presented an enhanced CO 2 RR performance due to its less cathodic phase transformation revealed by the in situ X‐ray absorption spectroscopy. Density functional theory calculations revealed different binding energies of key reaction intermediates on PdH 0.40 NCs/C and Pd NCs/C. Study of the size effect further suggests that NCs of smaller sizes show higher activity due to their more abundant active sites (edge and corner sites) for CO 2 RR. The pre‐hydridization and reduced NC size together lead to significantly improved activity and selectivity of CO 2 RR.