Abstract
Inverse-structured metal-metal oxide materials-where the oxides are located on top of a different metal-can provide unique chemical properties. Here, a few layers of reactive metal oxides, including In(2)O(3), MoO(3), Bi(2)O(3), or TiO(2), are overcoated on Al(2)O(3)-supported Pt nanoparticles using atomic layer deposition (ALD). In contrast to prior work focusing on stabilizing metal surfaces or new mixed-valence nanoparticles, here the goal is to create new reactive surfaces and interfaces. The overcoating altered the Pt nanoparticle accessibility as measured by STEM, CO chemisorption, and CO DRIFTS. The reactivity of the overcoated materials is interrogated with temperature-programmed reduction in H(2), in propane, and in the catalytic reaction of propane with O(2). Strong interactions between In(2)O(3) and the Pt nanoparticles are evident from changes in Pt accessibility, In(2)O(3) reducibility, and tandem catalytic reactivity. MoO(3) and Bi(2)O(3) overcoats also showed significant changes to Pt accessibility and the reducibility of the oxide in H(2); Bi(2)O(3) addition led to complete propane combustion. This study establishes ALD methods for reactive oxides on high surface area materials suitable for applications such as heterogeneous catalysis, and it illustrates the wide range of useful physiochemical modifications resulting from the unique oxide-metal interfaces generated.