Photocatalysis, as a green technology for addressing energy shortages and environmental pollution, has garnered widespread attention. However, due to the involvement of intricate multiscale dynamic processes of charge‐carriers during photocatalysis, conventional characterization methods struggle to directly observe changes in catalyst structure and reactive intermediates. In situ characterization techniques enable real‐time monitoring of structural evolution, charge‐carrier dynamics, and surface reactive species of photocatalysts under realistic or near‐realistic reaction conditions, directly linking the properties of photocatalytic materials to their performance. This capability is crucial for elucidating photocatalytic mechanisms and guiding the design of efficient photocatalysts. This review summarizes recent advances in the application of typical in situ characterization techniques in photocatalytic research, classified by the dimensionality of detected information into three aspects: monitoring photogenerated charge‐carrier behavior, identifying reactive intermediates and active sites, and observing catalyst structural evolution. The advantages and limitations of each technique, representative research examples, and mechanistic insights gained in photocatalysis are elaborated. Furthermore, future prospects are outlined, including multimodal operando photocatalysis platforms and artificial intelligence (especially machine learning and large language models). This review will provide valuable references for researchers, deepen the understanding of structure‐performance relationships in photocatalysis, and facilitate the rational design of novel high‐efficiency photocatalytic systems.
Fan et al. (Mon,) studied this question.