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.