Ultra-Low Loading Pt/CeO2 Catalysts: Ceria Facet Effect Affords Improved Pairwise Selectivity for Parahydrogen Enhanced NMR Spectroscopy.

Oxide supports with well-defined shapes enable investigations on the effects of surface structure on metal-support interactions and correlations to catalytic activity and selectivity. Here, a modified atomic layer deposition technique was developed to achieve ultra-low loadings (8-16 ppm) of Pt on shaped ceria nanocrystals. Using octahedra and cubes, which expose exclusively (111) and (100) surfaces, respectively, the effect of CeO2 surface facet on Pt-CeO2 interactions under reducing conditions was revealed. Strong electronic interactions result in electron-deficient Pt species on CeO2 (111) after reduction, which increased the stability of the atomically dispersed Pt. This afforded significantly higher NMR signal enhancement in parahydrogen-induced polarization experiments compared with the electron-rich platinum on CeO2 (100), and a factor of two higher pairwise selectivity (6.1 %) in the hydrogenation of propene than any previously reported monometallic heterogeneous Pt catalyst.