Study of carbon supported CuPd alloy nanoparticles with Pd-rich surface for the electrochemical formate oxidation and CO2 reduction

Abstract

Carbon supported copper-palladium alloy nanoparticles (CuPd/C) with Pd-rich surface synthesized via the adsorbate induced surface segregation method were tested toward both the electrochemical oxidation of formate into electricity and CO2, and the reduction of CO2 to produce formate. An upshift of the d-band center and opposite binding energy shifts of Cu and Pd core levels were experimentally observed using X-ray photoelectron spectroscopy (XPS). This perturbation of the surface electronic structure of the CuPd/C nanoparticles leads to the lowering of the bonding strength of key adsorbate species for both the formate oxidation and electrochemical CO2 reduction, which increased the catalytic activity toward both reactions. Amongst the different compositions of CuxPd1-x/C, the 20:80 molar% of Cu:Pd concentration shows an important improvement toward formate oxidation (FO) compared to the other CuxPd1-y compositions and the monometallic Pd. On the other hand, CuxPd1-x/C catalyst with the 60:40 molar% of Cu:Pd concentration shows the highest faradaic efficiency for the electrochemical CO2 reduction toward the formate production. Therefore, by selecting a bimetallic CuxPd1-x/C alloy that (1) optimizes the formate oxidation current density and (2) the faradaic efficiency of the electrochemical reduction of CO2 into formate, a novel sustainable and regenerative power source (i.e., combining a direct formate fuel cell and a CO2 reduction unit into a single regenerative energy system) could be developed.