Operando TEM Probes Dynamic Evolution of Transition Metal‐Based Catalysts and Their Heterostructures

Abstract Transition metals‐based catalysts and their heterostructures represent a critical category of catalytic materials, and understanding their catalytic mechanisms and achieving precise synthesis are of paramount importance. Operando transmission electron microscopy (TEM) enables real‐time monitoring of sample responses to external stimuli, which is crucial for observing structural, compositional, and electronic changes in nanocatalysts during reactions and aids in designing efficient catalysts and establishing atomic‐level structure‐property relationships. This review discusses how operando TEM, with its high spatial and temporal resolution, enables real‐time observation of critical phenomena such as nucleation, growth, sintering, and single‐atom dispersion in nanocatalysts. The effects of external stimuli, including gas atmosphere, thermal, optical, and electrical fields, on the structural and chemical properties of catalysts are analyzed. Moreover, the application of operando TEM for real‐time monitoring of structural evolution and external signal changes in catalysts under operating conditions is discussed, providing essential insights into the ‘black box’ of heterogeneous reactions. It is anticipated that these efforts will further facilitate the development of novel high‐performance catalysts and deepen the understanding of material structure‐performance relationships at a more profound level.