Quasi-Operando Liquid-Phase Electron Imaging of Metallic Copper Nanocubes Reveals Step-by-Step Subtle Dissolution, Redeposition, Reattachment, and Fragmentation Mechanisms during CO ₂ Electroreduction

ER in real time at nanometer resolution. Our statistical analysis reveals that dissolution/redeposition is the primary evolution mechanism. However, unlike other shapes, the thermodynamically active edges of copper cubes attract the redeposited aggregates that reattach to the cubes, moderating their surface-to-volume ratio. Additionally, the fragmentation mechanism was observed, which may occur due to highly defective sites. Our findings illustrate the synergistic effect of the thermodynamically high-energy sites and the role of the kinetic barrier in the dynamics of Cu nanocubes and their secondary aggregates, which affects their stability and as a consequence their selectivity over time.