Direct Observation of Sample Dynamics in the Gaseous Environment: A Perspective on Current Trends and Future Directions of In Situ Gas Cell Transmission Electron Microscopy

In situ environmental transmission electron microscopy (ETEM) is an emerging technique among in situ methods as it allows unique insights into the dynamic processes underlying gas-solid interactions. Aberration-corrected ETEMs providing atomically precise data mimicking benchtop conditions represent the state-of-the-art in in situ and operando experimentation. New developments in ETEM methods have sparked renewed interest in understanding solid-gas interactions, especially regarding catalyst systems, due to their structure-property correlation. Two types of ETEM systems are known: differentially pumped and windowed gas cell systems. With recent technological advancements, the gas cell system is emerging as a leading option for conducting in situ ETEM studies. In this Perspective, we have chosen to focus on recent reports in the past 4-5 years utilizing the windowed gas cell system, as well as several advancements in operando techniques, which highlight the extraordinary capabilities of the gas cell ETEM and its potential for the future.