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

Oxide supports with well-defined shapes are beneficial in catalysis studies as they enable investigations on the effects of surface structure on metal-support interactions as well as 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. By using octahedra and cubes, which expose exclusively (111) and (100) surfaces respectively, the effect of CeO2 surface facet on the Pt-CeO2 interactions under reducing conditions was revealed. Strong electronic interactions were found to result in electron-deficient Pt species on the CeO2 (111) after reduction, which increased the stability of the atomically dispersed Pt and afforded significantly higher NMR signal enhancement compared with the electron-rich platinum on the CeO 2 (100), and a factor of two higher pairwise selectivity (6.1 %) than previously reported for a monometallic heterogeneous Pt catalyst.