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

The electrochemical CO₂ reduction reaction (CO₂ RR) to syngas represents a promising solution to mitigate CO₂ emissions and manufacture value-added chemicals. Palladium (Pd) has been identified as a potential candidate for syngas production via CO₂ RR due to its transformation to Pd hydride under CO₂ 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 CO₂ 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 CO₂ RR. The pre-hydridization and reduced NC size together lead to significantly improved activity and selectivity of CO₂ RR.