Impact of Ceria Support Morphology on Au Single-Atom Catalysts for Benzyl Alcohol Selective Oxidation

Alcohol oxidations are a key industrial chemical transformation, with aldehydes and ketones finding use in an array of applications. Nobel metals are known for their activity towards this chemoselective transformation, however, sustainable catalyst synthesis requires optimal utilisation of these scarce elements. Here, we report Au catalytic systems based on the deposition of isolated Au sites on different morphologies of ceria in which different surface facets of the support are exposed. Through tailoring the support morphology and from extensive catalyst characterisation, it is shown that the exposed facet is critical for controlling the formation (or not) of isolated Au sites. Both the 110 and 111 facets are capable of this feat, yielding single-atom sites for rod, octahedron, and polyhedron morphologies. In contrast, the 100 facet is not, resulting in Au nanoparticles on cubic ceria. This dictation over Au species is critical to benzyl alcohol oxidation capacity at mild conditions and in the absence of a soluble base, with only single-atom catalyst (SAC) systems demonstrating activity. Furthermore, the exposed surface facet also governs the degree of surface oxygen vacancies, which is critical to catalyst activity due to their control over substrate adsorption strength, as revealed through T1/T2 NMR relaxation measurements. Single atoms of gold supported on ceria show excellent activity for base-free benzyl alcohol oxidation, with ceria morphology governing the formation of either single sites (Rods, icosahedra, polyhedral) or nanoparticles (cubes). Catalytic activity is dictated by the degree of Ce3+ surface species present in the different morphology, which simultaneously controls the strength of benzyl alcohol adsorption. image