Dynamic Restructuring of Stacking‐Fault‐Rich Copper Catalysts

Copper (Cu) catalysts with abundant defects are pivotal for converting CO 2 into valuable multi‐carbon products. However, the practical application of Cu catalysts is challenged by the thermodynamic instability of the defects, often leading to surface reconstruction during catalytic processes. Here, it is found that particle size and COO‐containing intermediates are key factors driving reconstruction, as the defect stability is size‐dependent and can be amplified by leveraging the highly reactive intermediates as the initial reactant. Combined experimental and theoretical analyses reveals that such intermediates induce significant electron delocalization at stacking faults (SFs), driving a size‐dependent reconstruction of stacking‐fault‐rich Cu catalysts. Smaller nanoparticles (10 nm) with lower chemical potential evolved into structures with 2.2 nm nanopores. In contrast, larger nanoparticles (30 and 60 nm) exhibit more stable stacking faults due to higher chemical potential. These findings deepen the understanding of the stability of stacking faults in Cu electrocatalysts, reinforcing the critical importance of designing stacking‐fault‐rich Cu catalysts at optimal sizes for sustainable applications.