Ultralong Distance Hydrogen Spillover Enabled by Valence Changes in a Metal Oxide Surface

Hydrogen spillover is a phenomenon in which hydrogen atoms generated on metal catalysts diffuse onto catalyst supports. This phenomenon offers reaction routes for functional materials. However, due to difficulties in visualizing hydrogen, the fundamental nature of the phenomenon, such as how far hydrogen diffuses, has not been well understood. Here, in this study, we fabricated catalytic model systems based on Pd-loaded SrFeOx (x similar to 2.8) epitaxial films and investigated hydrogen-spillover. We show that hydrogen spillover on the SrFeOx support extends over long distances (similar to 600 mu m). Furthermore, the hydrogen spillover-induced reduction of Fe4+ in the support yields large energies (as large as 200 kJ/mol), leading to the spontaneous hydrogen transfer and driving the surprisingly ultralong hydrogen diffusion. These results show that the valence changes in the supports' surfaces are the primary factor determining the hydrogen spillover distance. Our study leads to a deeper understanding of the long-debated issue of hydrogen spillover and provides insight into designing catalyst systems with enhanced properties.

Automated summary

In this study, catalytic model systems based on Pd-loaded SrFeOx films were fabricated to investigate the phenomenon of hydrogen spillover. The results showed that hydrogen spillover on the SrFeOx support can extend over long distances, up to 600 μm. The reduction of Fe4+ on the support surface induced by hydrogen spillover yields large energies, driving the unexpectedly long-distance hydrogen diffusion. These findings provide a deeper understanding of hydrogen spillover and offer insights for designing catalyst systems with enhanced properties.