Highly selective palladium-copper bimetallic electrocatalysts for the electrochemical reduction of CO2 to CO

Abstract

Selective and efficient conversion of carbon dioxide (CO2) to a reusable form of carbon via the electrochemical reduction of CO2 has attracted much attention recently, as it is a promising approach for the storage of renewable energy. Herein, we synthesize palladium-copper bimetallic nanoparticles with different compositions, which serve as a well-defined platform to understand their fundamental catalytic activity in CO2 reduction. Among PdCu/C and Pd/C catalysts tested, Pd85Cu15/C catalyst shows the highest CO Faradaic efficiency of 86%, CO current density of 6.9mAcm−2 and mass activity for CO production of 24.5Ag−1 at −0.89V vs. RHE in CO2-saturated 0.1M KHCO3 solution, which is about 5 times, 8 times and 2.2 times higher than Pd/C catalyst, respectively. It was suggested from EXAFS and CO TPD-MS studies that the highly selective CO production on Pd85Cu15/C catalyst is due to the presence of an optimum ratio of the copper element and low-coordination sites over monometallic Pd active for H2 evolution with low overpotential. We believe that controllable size and composition for the bimetallic nanoparticles are critical to the CO2 reduction activity enhancement and high CO Faradaic efficiency. The insights gained through this work may shed light in a foundation for designing efficient catalysts for electrochemical reduction of CO2.