Atom Trapping: Key to the Design of Thermally Stable and Regenerable Single Atom Catalysts

Abhaya K. Datye

University of New Mexico

Heterogeneous catalysts represent the mainstay of the chemical industry, and a large majority involve nanoparticles on a support. Decreasing size of the nanoparticles leads to better utilization of the precious metals, with the highest atom efficiency being achieved when the metal is atomically dispersed in the form of isolated atoms. Isolated atoms become mobile at elevated temperatures, causing agglomeration into nanoparticles. Our research is focused on developing methods to control the growth of particle size and the transformation of nanoparticles into isolated single atoms.

Supports differ in their ability to maintain small particles. For instance, if we prepare 1 wt% Pt synthesized using the same amine precursor and
calcined at 500 °C in air to decompose the precursor, the resulting catalysts are very different. The conventional term used to describe these differences is metal-support interactions (MSI),
which is meant to suggest bonding of the metal nanoparticle with the oxide support. But the term MSI fails to capture the underlying mechanism that leads to these observations. We have characterized these differences in catalyst supports in terms of their ability to trap atoms. We learnt that ceria supports help generate a stable and fully regenerable Pt catalyst that can change reversibly from single atoms into metallic nanoparticles. The understanding of atom trapping derived from ceria supports can be translated to other oxide supports. This will impact not only automotive exhaust treatment (where catalysts are exposed to high temperature) but also other industrial reactions such as propane dehydrogenation or methane oxidation, where high temperatures are required.