Advances for in situ characterization techniques applied to gas-solid heterogeneous catalysis under reaction conditions

Heterogeneous catalysis is fundamental to chemical processes, with gas-solid catalysis extensively employed in chemical production, energy conversion, and environmental protection. Attaining high efficiency in these processes necessitates catalysts exhibiting exceptional activity, selectivity, and stability, frequently accomplished using nanostructured metal catalysts. The continuous growth of active sites in heterogeneous metal catalysts presents a considerable obstacle for the precise identification of the genuine active sites. The emergence of in situ and operando characterization techniques has clarified the knowledge of dynamic alterations in active sites, offering substantial scientific information to underpin the rational design of catalysts. This review summarizes recent progress in the development of diverse situ/operando approaches for identifying active regions in catalytic conversion over heterogeneous catalysts. We comprehensively outline the applicability of diverse optical and X-ray spectroscopic techniques, including transmission electron microscopy, Raman spectroscopy, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy, in identifying active sites and elucidating reaction processes in heterogeneous catalysis. The discussion encompasses issues and future views on the identification of active sites evolution during the reaction process, as well as the advancement of in situ and operando characterization approaches.