Environmental electron microscopy (ETEM) for catalysts with a closed E-cell with carbon windows

Area of Science:

• Materials Science
• Catalysis Research
• Nanotechnology

Background:

• High-resolution electron microscopy is crucial for understanding catalyst behavior at the atomic scale.
• In situ environmental transmission electron microscopy (ETEM) allows observation of catalysts during reactions.
• Previous studies lacked atomic-scale resolution for dynamic catalyst processes.

Purpose of the Study:

• To perform in situ atomic-scale observations of supported gold (Au) and palladium (Pd) catalyst clusters during chemical reactions.
• To investigate the structural and morphological changes of catalysts under different gas environments (H2 and O2) and temperatures.
• To demonstrate the capability of a windows-cell ETEM system for real-time catalyst analysis.

Main Methods:

• Utilized a Jeol 3010 high-resolution electron microscope equipped with a Jeol environmental sample holder.
• Employed a windows-cell environmental transmission electron microscopy (ETEM) system for in situ observations.
• Conducted experiments with Au and Pd clusters on TiO2 and amorphous carbon supports under H2 and O2 gases at pressures up to 4 mbar and temperatures up to 350°C.

Main Results:

• Achieved atomic-scale resolution, visualizing (1 1 1) lattice fringes of Au and Pd clusters.
• Observed Au clusters cleaning in H2 and attaining equilibrium fcc crystal shapes during annealing.
• Demonstrated sequential observation of the same Au particles under successive O2 and H2 treatments.
• Found decreased adhesion of Pd clusters upon in situ exposure to O2.

Conclusions:

• The windows-cell ETEM system enables unprecedented in situ atomic-scale visualization of catalyst dynamics.
• Catalyst restructuring, including shape evolution and particle adhesion, can be directly observed during chemical reactions.
• This technique provides valuable insights into catalyst deactivation and activation mechanisms under reaction conditions.