Hydrogen Adsorption on Nanosized Platinum and Dynamics of Spillover onto Alumina and Titania

Abstract

An extended theoretical investigation of the electronic and interface properties of titania and alumina with and without supported platinum nanoparticles is presented and compared to recent experimental data with the aim to understand the mechanism of hydrogen activation, adsorption, and spillover. Thirteen-atom platinum particles on titania adopt a distinct different structure than on alumina, which results in distinct hydrogen coverages. Upon hydrogen adsorption, titania is reduced with creation of Ti(III) electronic trap states, strongly interacting with the surface adsorbed protons. The combined Ti(III)/proton migration rate is slower than the one of single surface protons, and it is not influenced by the presence of coadsorbates, such as water molecules. Hydrogen is instead heterolytically split on defect sites on alumina with the formation of a surface proton and a hydride moiety, bound to the particularly reactive surface tricoordinated aluminum site. The electronic structure of alumina is only mar...