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. Stronger interactions are observed between Pt and the (111) surface facets of the CeO2 octahedra compared with the (100) surfaces of the CeO2 cubes. These interactions result in more stable and electron‐poor Pt species on the CeO2 octahedra, which translates to higher pairwise selective addition of parahydrogen to propene and enhanced NMR signals compared with the electron‐rich nanoparticle Pt on the CeO2 cubes.