Unraveling the Dynamic Evolution of Cu-N-C during Electrochemical CO2 reduction: A Constant-Potential Ab-Initio Molecular Dynamics study

Atomically dispersed Cu single atoms anchored on N-doped graphene (Cu-N-C) have demonstrated significant potential for the electrochemical CO2 reduction reaction (CO2RR) toward multi-carbon (C2+) products. However, their catalytic performance is influenced by electrochemically induced structural transformations, particularly the structural evolution of atomically dispersed Cu into metallic Cu nanoparticles. Despite extensive experimental observations, the atomistic mechanism underlying this transformation remains unclear. In this work, we employed constant-potential ab initio molecular dynamics simulations (AIMD) to investigate the dynamic structural evolution of Cu-N-C under realistic CO2RR conditions. Our simulations reveal that Cu sites remain stable under pristine and during the hydrogen evolution (HER), but dissolve in the presence of N-H terminations and key CO2RR intermediates. Among these, CO* is identified as the most critical species driving Cu dissolution. The dissolved Cu ions subsequently aggregate and redeposit onto the surface, forming Cu nanoparticles (NP) on Cu-N-C. Furthermore, we find that carbon defects enhance the stability of the Cu-N bonding, helping to prevent Cu dissolution even under reactive conditions. These findings provide mechanistic insights into the electrochemical reconstruction of Cu-N-C catalysts and highlight the crucial roles of local coordination and specific intermediates in driving structural transformations.