Electrocatalytic Oxidative Dehydrogenation of Glyoxylic Acid to Oxalic Acid and Hydrogen Gas over Palladium–Bismuth Catalyst

Abstract Electrocatalytic oxidative dehydrogenation (EOD) of aldehydes over copper (Cu)-based catalysts enables ultralow voltage and simultaneous production of hydrogen gas (H2) and carboxylic acids. However, Cu suffers from instability at elevated potentials, which has limited the study of the EOD process. Herein, we present palladium–bismuth bimetallic catalysts as an alternative to Cu-based catalysts for EOD. Palladium–bismuth was electrodeposited on carbon cloth using cyclic voltammetry to uniformly disperse the metals. Bipolar H2 was produced by oxidizing glyoxylic acid at the anode via EOD and water splitting at the cathode with anodic potential between 0.625 and 1.125 V vs reversible hydrogen electrode. When approaching higher potentials, the Faradaic efficiency for the EOD reaction decreased from 77 to 12% as the electrochemical oxidation of glyoxylic acid became more favored. Density functional theory calculations suggest that the addition of Bi to Pd helps facilitate the EOD reaction by weakening CO binding, allowing for Pd–Bi to function as an oxidation catalyst at potentials where Pd electrocatalysts are CO poisoned. Despite the low Faradaic efficiency at high potentials, this study demonstrates that EOD can occur at more anodic potentials than reported for Cu-based catalysts, due to the improved oxidative stability of Bi-based catalysts.