Microscopic insights into Cu-N-C catalyst stability and leaching mechanisms through orbital interactions

Abstract

Copper-nitrogen-codoped graphene (Cu-N-C) single-atom catalysts (SACs) feature an intriguing dynamic transformation between copper single atoms and clusters under electrochemical conditions, a behavior absent in the other metal-centered M-N-C SACs. Yet, the underlying cause of this distinctive phenomenon remains poorly understood. Herein, we delve into the modulation of electronic structure in M-N-C SACs by the solvent effects and electrochemical potentials, revealing the leaching mechanisms of copper atoms based on Crystal Field Theory (CFT) and hybrid-solvation constant potential method. We demonstrate that in M-N-C SACs, the orientation of d-orbitals nearest to the Fermi level determines the stability of M-N bonds. The d⁹ electronic configuration of copper imparts the Cu-N bond with the highest sensitivity to external voltage. Meanwhile, it is revealed that proton transfer (PT) on central copper atoms rearranges the energy levels of d-orbitals near the Fermi level, accelerating charge accumulation in the anti-bonding state in Cu-N bonds and ultimately inducing copper atoms leaching. These findings provide microscopic insights into the interaction between electronic orbitals and leaching behaviors in Cu-N-C SACs, advancing the mechanistic understanding of dynamic phenomena in electrochemical systems.