Competing Surface Dynamics of Copper Catalyst Particles during Electrochemical Carbon Dioxide Reduction

Copper is a powerful catalyst for the electrochemical carbon dioxide reduction reaction (CO2RR), but it faces challenges with selectivity and stability dependent on its structural characteristics. We developed a platform that combines graphitized carbon nanofibers with identical-location transmission electron microscopy (IL-TEM) to study individual copper nanoparticles at the atomic scale under various reaction conditions. Notably, we observed that competing phenomena such as Ostwald ripening, coalescence, selective etching, and Coulomb-explosion-like fragmentation coexist in the same reaction area, with the latter being qualitatively consistent with a charge-driven fission pathway in larger nanoparticles (>10 nm). By tracking uniquely identifiable nanoparticles both individually and in groups, our findings focus on the range of surface-confined restructuring pathways during CO2RR. This contrasts with solution-mediated phenomena, such as dissolution–precipitation, which dominate under open-circuit potential (OCP) and significantly destabilize the catalyst prior to the reaction, highlighting the importance of eliminating this effect. Under CO2RR conditions, Cu nanoparticles are highly sensitive to subtle variations in the support’s nanotexture, defects, and electronic structure, leading to the coexistence of counteracting mechanisms we observed. These observations provide a structural framework for understanding the dynamic behavior of copper-on-carbon catalysts under CO2RR conditions, guiding the development of strategies to improve catalyst stability and performance.