Solvent Promotion on the Metal-Support Interaction and Activity of Pd@ZrO2 Catalyst: Formation of Metal Hydrides as the New Catalytic Active Phase at the Solid-Liquid Interface

Abstract The supported metal catalysts are usually prepared and widely applied in aqueous phase. Here, by performing density functional theory calculations and ab initio molecular dynamics simulations with explicit solvent waters, the metal-support interaction of Pd@ZrO2 catalyst was found to be enhanced by water dissociation at the metal-support interface. This happens to an appreciable number of interfacial waters, generating ∼25% hydrides compared to Pd atoms. During the partially heterolytic dissociation, the generated Hδ+ would undergo the proton coupled electron transfer (PCET) from Pd to form the hydride (Hδ-). The spatial separation of the generated H on Pd and remaining OH on ZrO2 results in the polarization of metal-support interface, which then flattens the shape of cluster. Moreover, the formed metal-hydride behaves as the new catalytic active phase for CO oxidation, making the catalyst highly active in water vapor.