Femtosecond Insights Into Catalytic Non‐Steady‐State Dynamics

Dynamic structural evolution in catalytic processes, such as atomic reconstruction of catalysts, molecular rearrangement at solid‐liquid interfaces, and quantum‐scale fluctuations, is key to determining their intrinsic activity and selectivity. However, these non‐steady‐state processes often occur on ultrafast timescales ranging from femtoseconds to nanoseconds, far beyond the detection limits of conventional in situ characterization techniques, and have long been regarded as a “black box.” The emergence of femtosecond ultrafast characterization techniques has provided revolutionary tools to address this challenge. This review pioneers a systematic exploration of the non‐steady‐state structural evolutions in catalysis and their structure‐activity relationships with catalytic performance from an ultrafast timescale perspective under femtosecond characterization. It elaborates on the underlying principles of these cutting‐edge techniques and unparalleled capabilities in capturing structural reconstruction, interfacial evolution, and quantum fluctuations. It highlights cross‐disciplinary applications in three major categories of key catalytic reactions (electrocatalysis, photocatalysis, and thermal catalysis), as well as in advanced battery research. Finally, this review outlines the challenges and future directions in the field, aiming to deliver pioneering dynamic‐level insights and strategies for the rational design of next‐generation high‐performance energy conversion and storage systems.