(113g) Inverse Effects in Catalysis: Impact of Metals on Supports

Metal-support interactions have garnered much attention due to their impact on the structure and reactivity of supported metal catalysts. Despite the widespread recognition of multifunctional mechanisms in metal/metal oxide systems, much less attention has been paid to how the metal influences its support. Here, we explore metal-support interactions using hydrogen adsorption and spillover at the interface of dehydroxylated γ-Al₂O₃(110) supported Pt₁₀ clusters as a prototype. Through molecular dynamics simulations performed using an actively trained machine-learned force field, we observed reversible hydrogen spillover between the support and the metal. Analysis of the electronic structure and chemical nature of the interface reveals that charge transfer from H to the Pt₁₀ cluster drives the spillover by stabilizing H adsorbed on the support. The same charge transfer concept also explains the stabilization of OH fragments at the Pt₁₀/γ-Al₂O₃(110) interface despite the scarcely impacted or even reduced acidity of interfacial Al sites. A loss of Lewis acidity at the interfacial sites, however, does not mean a loss in reactivity. By computing the barrier of heterolytic H₂ dissociation on Al/O pairs as a prototypical acid-base reaction, we found that some Al/O pairs can become highly active, due to surface relaxation and reconstruction of the dehydroxylated γ-Al₂O₃(110) surface induced by the Pt₁₀ cluster. This perturbation to the interfacial Al/O site structure and chemical properties shifts the transition state geometry and ultimately leads to the formation of site-specific transition state scaling relations. Overall, our findings demonstrate the rich chemistry of metal-support interfaces and the importance of “inverse” effects in the fundamental understanding of supported catalysts.