Pd-Bi Bimetallic Nanochains for Electroreduction of CO₂ to Syngas in Ionic Liquid-Based Electrolytes

The electroreduction of carbon dioxide (CO₂ ) is a sustainable method for generating valuable chemicals; however, avoiding unwanted hydrogen (H₂ ) production during the electrolysis is a major challenge. Coproduction of carbon monoxide (CO) and H₂ to produce syngas is an effective strategy for solving this problem, and syngas with a desired CO/H₂ ratio can be employed to produce methanol or other valuable chemicals. Herein, a series of palladium-bismuth (Pd-Bi) bimetallic nanochains with different Pd/Bi atomic ratios were prepared and used in the electroreduction of CO₂ to syngas in ionic liquid-based electrolytes. The ratio of CO/H₂ in syngas was regulated in a wide range from 1 : 7 to 9 : 1 by controlling the applied potentials, Pd/Bi atomic ratios and composition of the electrolytes. In particular, the current density reached 19.3 mA cm^-2 on Pd₃ Bi bimetallic nanochains at an applied potential of -2.3 V versus Ag/Ag⁺ when the CO/H₂ ratio was approximately 1 : 1. Moreover, the maximum CO Faradaic efficiency was 87.7 % for these electrocatalysts at an applied potential of -2.0 V versus Ag/Ag⁺ . The synergistic effect of Pd and Bi in the ionic liquid-based electrolyte was the primary reason for the distinct electrocatalytic efficiency of the Pd₃ Bi bimetallic nanochains. The incorporation of moderate amounts of Bi into the Pd lattice resulted in a stronger CO₂ adsorption capacity, more active sites and faster electron transfer rate, which are conducive to improving the electrocatalytic activity.