Visualizing Hydration‐Induced Cu Migration in SSZ‐13 Zeolite Through Electron Ptychography

ABSTRACT Cu‐exchanged SSZ‐13 zeolite (Cu‐SSZ‐13), a dynamic catalytic system, plays a critical role in the selective catalytic reduction of nitrogen oxides with ammonia (NH 3 –SCR). Catalytically active Cu ions exhibit activity through the adsorption and desorption of ammonia. Although the actual reaction involves complex interactions, clarifying Cu speciation based on water‐Cu interactions provides a fundamental baseline for understanding the active site dynamics. Although x‐ray diffraction and absorption have provided insights into the dynamic changes of Cu sites, their interpretation remains limited to average structures, leaving atomic‐scale local structures unresolved. Here, we directly visualized the hydration‐induced migration of Cu ions using electron ptychography, which enabled low‐dose imaging with atomic resolution. Under hydrated conditions corresponding to catalytic environments, Cu ions were observed to migrate from double six‐membered ring sites to eight‐membered ring sites. Although these hydrated Cu sites were largely consistent with those predicted using theoretical models, sub‐angstrom deviations were detected, suggesting the presence of a previously unrecognized Cu site. Revealing the local structure and dynamics of guest metal ions not only provides critical insights for optimizing catalytic performance but also advances our fundamental understanding of the mechanisms of catalytic activation and degradation, thereby opening new avenues for developing advanced zeolite catalysts.