Advances in in situ and operando TEM: From basic catalysis to industry-relevant reactions and future directions

Heterogeneous catalysis is the cornerstone of the chemical and energy sectors and is expected to be crucial in the transition from fossil fuels to sustainable energy sources. These catalytic reactions, occurring at the interface between solid catalysts and gaseous or liquid reactants, require thorough investigation for the design of highly active, stable, and selective materials. In situ transmission electron microscopy (TEM) is a sophisticated technique that combines high spatial imaging resolution with integrated spectroscopy techniques, enabling the direct observation of catalysts under realistic conditions and specific stimuli. When complemented by additional analytical methods, in situ TEM facilitates operando experiments that uncover crucial structure-property relationships. This review provides an overview of recent advancements in in situ and operando TEM applied to catalysis research, with a focus on industrially and environmentally significant reactions. Finally, we discuss the future directions and ongoing evolution of in situ TEM as a tool to drive further innovations in catalysis research.