Polarization-Induced Local pH Swing Promotes Pd-Catalyzed CO 2 Hydrogenation

Electrochemical polarization can dramatically promote the rate of concurrent nonfaradaic catalytic reactions, but the mechanistic basis for these promotion effects at solid–liquid interfaces remains poorly understood. Herein, we establish a mechanistic framework for nonfaradaic promotion in aqueous media that operates via a local pH swing induced by a concurrent faradaic reaction. As a model system, we examined the kinetics of nonfaradaic Pd-catalyzed CO 2 hydrogenation to formate and find that the reaction can be promoted by a combination of high alkalinity and high CO 2 concentration. In bulk electrolyte, alkalinity and CO 2 concentration are inversely correlated to each other as set by the CO 2 /bicarbonate equilibrium. We show that this impasse can be overcome by using electrical polarization to generate a nonequilibrium local environment that has both high alkalinity and high CO 2 c…