Imaging Gas-Involved Structural Dynamics by Environmental Electron Microscopy.

Understanding gas-involved physicochemical reactions is undoubtedly one of the most significant challenges in the modern chemical industry. To clarify how those reactions precede requires deep insights into the real-time visualization of reaction dynamics within a gas environment. The emergence and rapid development of in situ environmental electron microscopy (EEM) including scanning electron microscopy (ESEM) and transmission electron microscopy (ETEM) have enabled multiscale observation of dynamic gas-involved physicochemical reactions. This review examines the state-of-art EEM technologies, categorizing those gas reactions into various physical and chemical processes and detailing the corresponding dynamic behaviors. It begins by reviewing the state-of-the-art EEM techniques and is followed by detailing their application in typical physical processes. It clarifies physical vapor condensation, deposition, and geometric reshaping with gaseous involving. More importantly, all the gas-involved chemical reactions into electrochemical reactions, thermochemical reactions, chemical crystal growth, and catalytic reactions are thoroughly explored and categorized. Finally, the review highlights the technical challenges and valuable perspectives provided by in situ EEM for addressing critical gas-involved issues. Overall, this article offers a multiscale and comprehensive understanding of the physicochemical origins associated with gas-involved reactions, envisioning fundamental strategies for designing high-performance gas-involved functional materials.