Preparation of Various Pd-Based Alloys for Electrocatalytic CO₂ Reduction Reaction—Selectivity Depending on Secondary Elements

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.