(656f) Ab Initio Molecular Dynamics Reveals New Active Sites in Atomically Dispersed Pt1/TiO2 Catalysts

Recent developments in catalysis focus on enhancing catalytic efficiency by atomically dispersing Pt-group and noble metals on support surfaces, predominantly for oxidation chemistry. 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 can be challenging. We employ a multiscale approach combining 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 TiO₂. Several new sites emerge from our analysis of 2ps NVE trajectories initiated at favorable lattice-binding sites determined in prior studies. In particular, we observe one site each on the pristine and vacancy-containing surfaces that consists of a near-linear O-Pt-O geometry. Such a site has not been reported before for these systems. An elementary surface chemistry study of CO adsorption shows that binding energies are highly sensitive to active site geometry and therefore span a wide range -- from -0.45eV at basal oxygen vacancies to -4.17eV at the H2 site. Therefore, it is important to examine the implications of the active site distribution on the mechanisms and kinetics of PROX and WGS reactions. Our subsequent objective is to examine the catalytic relevance of these newly determined sites and expand the scope of AIMD work to probe the dynamic sensitivity of the metal atom to adsorbates at reaction temperatures.