Electrochemical promotion of catalysis over Pd nanoparticles for CO(2) reduction

Electrochemical promotion of catalysis (EPOC) has been shown to accelerate the rate of many heterogeneous catalytic reactions; however, it has rarely been reported in low-temperature aqueous electrochemical reactions. Herein, we report a significant EPOC effect for the CO(2) reduction to generate formate over Pd nanoparticles (NPs) in a 1 M KHCO(3) aqueous solution. By applying a negative potential over differently-sized Pd NPs, the rate of formate production is greatly improved as compared to that at an open-circuit voltage, with a rate enhancement ratio ranging from 10 to 143. The thermocatalytic and electrocatalytic reduction of CO(2) compete with each other and are promoted by the applied negative potential and H(2) in the feeds, respectively. Inspired by the EPOC effect, a composite electrode containing Pd/C and Pt/C catalysts on different sides of a carbon paper was constructed for catalyzing the CO(2) reduction without adding H(2) to the feeds. Water electrolysis over Pt NPs generates H(2), which then effectively promotes formate production over Pd NPs.