In-situ visualization of atomic scale reaction dynamics of supported nanocatalysts during oxidation and ammonia synthesis using environmental (scanning) transmission electron microscopy

Abstract Reaction dynamics in gases at operating temperatures at the atomic level are the basis of heterogeneous gas-solid catalyst reactions and are crucial to the catalyst function. Supported noble metal nanocatalysts such as platinum are of interest in fuel cells and as diesel oxidation catalysts for pollution control, and practical ruthenium nanocatalysts are explored for ammonia synthesis. Graphite and graphitic carbons are of interest as supports for nanocatalysts. Despite considerable literature on the catalytic processes on graphite and graphitic supports, reaction dynamics of the nanocatalysts on the supports in different reactive gas environments and operating temperatures at the single atom level are not well understood. Here we present real time in-situ observations and analyses of reaction dynamics of Pt in oxidation, and practical Ru nanocatalysts in ammonia synthesis, on graphite and related supports under controlled reaction environments using a novel environmental (scanning) transmission electron microscope with single atom resolution. By recording snapshots of the reaction dynamics, the behaviour of the catalysts is imaged. The images reveal single metal atoms, clusters of a few atoms on the graphitic supports and the support function. These all play key roles in the mobility, sintering and growth of the catalysts. The experimental findings provide new structural insights into reaction dynamics, morphology and stability of the nanocatalysts.