(392a) Deactivation and Reactivation of the Copper Electrocatalyst during CO Reduction in Alkaline Media

Electrochemical CO₂ reduction enables carbon-neutral fuels and chemicals to be produced using renewable electricity. The reaction produces ethene, the most widely produced organic compound in the world, as the dominant reaction product when catalyzed by a Cu-based electrocatalyst. Unfortuantely, the reaction suffers from poor voltage, current, and CO₂ utilization efficiencies. The poor CO₂ utilization efficiency is a direct result of mineralization reactions between CO₂ and hydroxide anions evolved over the cathode surface. Many of these challenges can be improved or completely circumvented by splitting the overall reaction into a series of reaction steps: the first converting CO₂ into CO and the second converting CO into ethene. The latter reaction is performed using a gas diffusion electrode and an alkaline electrolyte, which improves both the voltage and current efficiencies for ethene production. However, the Cu electrocatalyst exhibits poor stability under these conditions and neither the mechanism of deactivation nor effective reactivation protocols have been identified. This presentation will begin by elucidating the mechanism of deactivation of the Cu electrocatalyst in alkaline media using a combination of x-ray photoelectron spectroscopy, low energy ion scattering, and electrochemical mass spectrometry. Carbophillic trace metal electrolyte impurities are identified as the ultimate cause of the observed deactivation. These carbophilic impurities are deposited onto the electrocatalyst surface during the reaction and then catalyze coke formation, which results in near complete deactivation over prolonged operation. This knowledge is then leveraged to develop effective reactivation protocols that utilize brief anodic pulses to strip the electrodeposited impuriuties and coke from the electrocatalyst surface. This protocol elevates the ethene partial current density after 20 hrs of continuous operation by over 500% while reducing the time spent producing value-added products by less than 1%.