Performing In Situ Closed-Cell Gas Reactions in the Transmission Electron Microscope

Area of Science:

• Materials Science
• Surface Chemistry
• Analytical Chemistry

Background:

• In situ electron microscopy allows real-time observation of material transformations.
• Dynamic reactions are challenging to capture with traditional characterization methods.
• Closed-cell gas reaction (CCGR) studies offer a solution for observing reactions in controlled gas environments.

Purpose of the Study:

• To detail a method for performing in situ gas reactions in an aberration-corrected scanning transmission electron microscope (STEM).
• To demonstrate the application of microelectromechanical systems (MEMS)-based heating microchips (E-chips) for controlled gas reactions.
• To highlight the integration of residual gas analysis (RGA) for correlating gas composition with material evolution.

Main Methods:

• Utilized a CCGR holder with MEMS-based E-chips in an aberration-corrected STEM.
• Performed in situ gas reactions in both dry and wet gases at atmospheric pressure.
• Integrated a residual gas analyzer (RGA) to monitor gas composition during experiments.
• Described sample preparation methods for various material form factors.

Main Results:

• Successfully captured real-time morphological and microchemical transformations of materials at the atomic level.
• Demonstrated the ability to separate and identify localized dynamic reactions under various gas conditions (with/without water vapor).
• Validated gas exposure conditions using RGA mass spectra, correlating them with observed material surface evolution.

Conclusions:

• The described CCGR-STEM method provides critical insights into fundamental reaction mechanisms and kinetics.
• This approach allows for detailed investigation under specific environmental conditions (time, temperature, gas, pressure) in real-time.
• The technique is applicable to diverse materials systems, including catalysis and high-temperature oxidation.