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.