Decoupling CO2 Effects from Electrochemistry: A Mechanistic Study of Copper Catalyst Degradation

Copper-based nanoparticles are key electrocatalysts for CO2 electrochemical reduction (CO2 ER) to liquid fuels and other value-added products. However, the copper catalyst can undergo rapid electrochemical corrosion, leading to a loss of catalyst material, fluctuations in the reaction conditions and increasing operational costs. We establish a mechanistic understanding of this detrimental process using in situ electrochemical electron microscopy and density functional theory (DFT). We find that copper corrosion can occur in the presence of CO2 in electroless conditions and before the onset potentials required for CO2 ER. The effects are isolated from pH changes resulting from dissolved CO2. Particles of corroded copper have oxidized surfaces, in contrast to copper surfaces exposed to CO2-free electrolytes. DFT calculations identify multiple routes by which CO2 can behave as a dissolution agent for copper and copper-oxide surfaces and suggest that formate-intermediates are a key driver of corrosion. This study highlights microenvironment-based factors that affect copper performance and degradation, facilitating strategies to inhibit and reverse copper degradation during CO2 ER.