Free Standing Nanoporous Pd Alloys as CO Poisoning Tolerant Electrocatalysts for the Electrochemical Reduction of CO2 to Formate

CO2 electrochemical reduction to formate has emerged as one of the promising routes for CO2 conversion to useful chemicals and renewable energy storage. Palladium has been shown to make formate with a high selectivity at minimal overpotential. However, production of CO as a minor product quickly deactivates the catalyst during extended electrolysis. Here, we present nanoporous Pd alloys (np-PdX) formed by electrochemical dealloying of Pd15X85 alloys (X = Co, Ni, Cu, and Ag) as active free standing electrocatalysts with high formate selectivity and superior CO poisoning tolerance. Rate of deactivation under constant potential electrolysis, due to CO passivation, is strongly correlated to the identity of the transition metal alloying component. We purport that this composition dependent behavior is due to the induced electronic changes in the active Pd surface, affecting both the CO adsorption strength and the near surface hydrogen solubility which can impact the adsorption strength of active/inactive intermediates and reaction selectivity. Free-standing np-PdCo is found to exhibit high areal formate partial current densities, > 40 mA cm-2, with superior CO poisoning tolerance and minimal active area loss at cathodic potentials, demonstrating the utility of these materials for selective and stable CO2 electrolysis