Catalysis performance comparison for electrochemical reduction of CO2 on Pd-Cu/graphene catalyst

A Pd-Cu/graphene catalyst for the electrochemical reduction of CO2 was prepared by means of sodium borohydride reduction in a graphite oxide suspension with metal precursor salts, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), linear sweep voltammetry (LSV), cyclic voltammetry (CV), and current-time (I-t) scans technologies. The formation of Pd-Cu catalysts was investigated by changing the precursors and the Pd-Cu ratio. The results indicated that graphene with a d-spacing of 3.82 angstrom was fabricated and Pd-Cu metal nanoparticles whose size ranges from 8 to 10 nm were highly dispersed on the graphene sheets with amorphous structure. Additionally, sharp increase of the reduction current under CO2 compared to that under N-2 could be observed which contributed to the catalytic reaction of CO2 reduction on the Pd-Cu/graphene electrode. The best catalytic performance of the metal/graphene catalysts was achieved on 1 wt% Pd-2 wt% Cu/graphene, which had a relative positive peak potential and reduction current were -1.3 V (vs. Ag/AgCl) and -2.8 mA, respectively. The Pd-Cu/graphene electrode effectively suppressed the reaction process of hydrogen and showed stable CO2 reduction activity. Finally, the reaction pathway for the CO2 reduction on the Pd-Cu/graphene electrode was proposed.