Effects of Oxide Platforms on the Dynamics and Reduction Characteristics of Hydrogen Spillover
Abstract
The characteristics of hydrogen spillover on various metal oxides, involving the concurrent diffusion of protons (H+) and electrons (e-), were systematically studied by combining in situ analytical techniques with kinetic analyses. H2-temperature programmed reduction and in situ X-ray absorption fine structure data showed that hydrogen spillover from Pt onto TiO2 and WO3 greatly decreased the temperatures at which Zn2+ ions deposited on these remote metal oxides were reduced. In contrast, hydrogen spillover on MgO and CeO2 did not significantly affect the reduction of remote Zn2+. Mechanisms explaining the effects of spilled hydrogen on reduction for each oxide substrate were proposed based on the dynamic behaviors of H+ and e- as ascertained by means of in situ spectroscopic characterizations and kinetic analyses. The results of this work indicate that e- diffusion rather than H+ diffusion promotes the reduction of deposited metal ions and that interparticle hydrogen spillover can be facilitated over TiO2 and WO3 as a consequence of the interfacial diffusion of H+ and e- pairs. These findings provide an improved understanding of the hydrogen spillover phenomenon.