Recent developments in catalysis focus on enhancing catalytic efficiency by atomically dispersing Pt-group and noble metals on oxide and other support surfaces. While microscopy and spectroscopy combined with computational studies yield critical insights into the location and coordination of these metal centers, the study of operando characteristics remain challenging. We combine quantum chemistry with ab initio molecular dynamics (AIMD) to determine the distribution of active sites obtained under reaction conditions for Pt-group metals on oxide supports. Pt exhibits a wide range of coordination environments and binding energies on rutile TiO<sub>2</sub>. New sites emerge from our analysis of 2ps NVE trajectories at high temperature (1200K) initiated at favorable lattice-binding sites determined in prior studies. In particular, we observe previously unreported sites on pristine and vacancy-containing surfaces that consist of a near-linear O-Pt-O geometry. In addition to thermally-induced migration, reaction intermediates constituting CO oxidation or water-gas shift can also induce mobility of the Pt atom. At 500K, we find that hydroxyl groups adsorbed on Pt induce rapid migration, which we hypothesize is occurring via the dynamical formation of hydrogen-bonds with oxygen atoms on the support. Through an extensive analysis of the stability of the metal-bound site under reaction conditions and site-sensitivity of catalytic activity towards CO oxidation, our goal is to develop a dynamical picture of the catalytic interface in atomically dispersed systems.

Dynamical evolution of atomically dispersed catalysts

ACS Spring Meeting 2021

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