The electrochemical conversion of CO 2 to fuels such as CO and HCOO − is a highly attractive approach for decreasing the amount of greenhouse gases in the atmosphere and sustainable generation of valuable resources. Herein, electrocatalytic selectivities toward CO 2 reduction reaction over nanosized Pd−M (M = Zn, Cu, Sn, and Ag) bimetallic alloys were investigated. It was found that the selectivity for the products in the CO 2 reduction reaction depends on the effects of secondary elements, with Pd−Zn and Pd−Cu alloys showing formate selectivity and Pd−Ag 3 and Pd−Sn alloys showing CO selectivity. The faradic efficiency (FE) of HCOO − for PdZn NPs/CB was found to be significantly higher than that of the conventional Pd nanoparticles catalyst for the CO 2 reduction reaction at −0.1 V, and a record high FE of 99.4% at −0.1 V was also found. On the other hand, bimetallic PdAg 3 exhibits CO selectivity with a low overpotential and a much high FE (96.2% at −0.8 V) compared to Pd. The analysis of the center of the Pd d-band (i.e., d-band center) allowed us to rationalize the obtained high FE toward the CO 2 reduction reaction. We believe that this systematic effort will accelerate the development of novel highly selective and active electrocatalysts.

It is important to investigate the electrochemical reduction reaction of CO2 on the catalytic selectivity dependence the materials because it might be guideline to create a co-catalyst of photocatalytic CO2 reduction. Widely studied electrocatalysts for electrochemical CO2 reduction are precious metals, such as Pd, Ag, and Au. It is known that precious metals can efficiently reduce the CO2 to carbon monoxide (CO) or formate (HCOO-). In particular, Pd nano-particles (Pd NPs) was proved as a unique electrocatalyst for CO2 reduction. HCOO- and CO generation for electrochemical reduction of CO2 on Pd NPs can be observed at low and high potential region, respectively. It should be believed that high selectivity towards CO formation can be realized by a formation of bimetallic compounds with transition metals in Pd structure.