Significant developments in micro-electrical-mechanical systems (MEMS)-based devices have led to the commercialization of windowed gas cells that now enable atomic-resolution scanning transmission electron microscopy (STEM) observation of phenomena occurring during gas-solid interactions at atmospheric pressure. An in situ atmospheric STEM study provides information that is beneficial to correlating the structure-properties relationship of catalytic nanomaterials, particularly under realistic gaseous reaction conditions. In this article, we illustrate the advantages of this tool as applied to our study of two important systems: (1) the CO-induced Pt nanoparticle surface reconstruction at saturation coverage and (2) the ordering and Pt surface enrichment in supported Pt3Co nanoparticles.
