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

Abstract

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.