Robust palladium hydride catalyst for electrocatalytic formate formation with high CO tolerance

Palladium is unique in the electrocatalytic reduction of CO2 to formate because of its low or even near-equilibrium onset potential. However, the inevitably produced CO molecules poison and deactivate the catalyst surface, resulting in an insufficient operating lifetime (<30 min) for conventional and optimized Pd catalysts. Herein, we present a hydrogen-rich Palladium hydride catalyst (PdH0.5/C) derived from a one-step solvothermal synthesis. This catalyst showed a 93.1 % faradaic efficiency towards formate at - 0.4 V (vs RHE). The working lifetime reached a record of 4 h, which was similar to 15 times longer than a commercial Pd catalyst and outperformed all previous Pd-based electrocatalysts for CO2-HCOO- conversion . The high CO tolerance was attributed to the selectivity improvement induced by lattice hydrogen and the weak CO adsorption strength on diverse active sites (i.e. kink, step, and terrace). Isotopic analysis revealed a direct participation of the lattice hydrogen in the protonation of CO2 molecules in formate formation.