(127d) Study of Carbon Supported Cupd Alloy Nanoparticles with Pd-Rich Surface for the Electrochemical Interconversion between CO2 and Formate

Human activities have dramatically increased the CO₂ concentration in the atmosphere from 300 to 408 ppm within just seven decades. One way to address this important issue would be developing a sustainable energy system to limit any future release of CO₂ by combining an electrochemical CO₂ reduction (eCO₂R) unit and a direct formate fuel cell (DFFC). Palladium (Pd) is reported to be one of the few catalysts that can reduce CO₂ into formate at low overpotential (< 0.2 V)and it is one of the most widely used catalysts for formate oxidation (FO). However, in order to use Pd as the catalyst for both the eCO₂R and FO, the following needs to be addressed: (1) the high cost of Pd and (2) the limited current toward the interconversion between CO₂ and formate. According to the reaction mechanism, the catalytic activity of Pd toward eCO₂R and FO can be increased by decreasing the bonding strength of Pd-hydrogen and Pd-oxygen.

In this work, we achieved this by modifying the electronic surface properties of Pd by synthesizing carbon-supported copper-palladium nanoparticles (CuPd/C NPs). The size of the nanoparticles was determined by transmission electron microscopy (TEM). The crystallographic orientation of the surface of the NPs was determined by X-ray powder diffraction (XRD). Their electronic surface property was measured by X-ray photoelectron spectroscopy (XPS). Finally, the electrochemical activity and stability toward eCO₂R and FO were measured by cyclic voltammetry (CV) and controlled potential electrolysis (CPE). The results of XPS and CV measurements confirmed that by decreasing the binding energies of the Pd-H and the Pd-O on the surface of CuPd/C modified the catalytic activity toward eCO₂R and FO. The lowering of the binding energy improved the electrochemical activity of this bimetallic CuPd/C catalyst toward both eCO₂R and FO.