  Heterogeneous gas and solid catalyst reactions occur at the atomic level, and
understanding and controlling complex catalytic reactions at this level is
crucial for the development of improved processes and materials. There are
postulations that single atoms and very small clusters can act as primary
active sites in chemical reactions. Early applications of our novel aberration
corrected (AC) environmental scanning transmission electron microscope (ESTEM)
with single atom resolution are described. This instrument combines, for the
first time, controlled operating temperatures and a continuous gas environment
around the sample with full AC STEM capabilities for real-time in-situ analysis
and visualization of single atoms and clusters in nano particle catalysis.
ESTEM imaging and analysis in controlled gas and temperature environments can
provide unique insights into catalytic reaction pathways that may involve
metastable intermediate states. Benefits include new knowledge and more
environmentally friendly technological processes for health care and renewable
energy as well as improved or replacement mainstream technologies in the
chemical and energy industries.
