The Extent of Platinum-Induced Hydrogen Spillover on Cerium Dioxide

Hydrogen spillover from metal nanoparticles to oxides is an essential process in hydrogenation catalysis and other applications such as hydrogen storage. It is important to understand how far this process is reaching over the surface of the oxide. Here, we present a combination of advanced sample fabrication of a model system and in situ X-ray photoelectron spectroscopy to disentangle local and far-reaching effects of hydrogen spillover in a platinum-ceria catalyst. At low temperatures (25-100 degrees C and 1 mbar H2) surface O-H formed by hydrogen spillover on the whole ceria surface extending microns away from the platinum, leading to a reduction of Ce4+ to Ce3+. This process and structures were strongly temperature dependent. At temperatures above 150 degrees C (at 1 mbar H2), O-H partially disappeared from the surface due to its decreasing thermodynamic stability. This resulted in a ceria reoxidation. Higher hydrogen pressures are likely to shift these transition temperatures upward due to the increasing chemical potential. The findings reveal that on a catalyst containing a structure capable to promote spillover, hydrogen can affect the whole catalyst surface and be involved in catalysis and restructuring.

Automated summary

Hydrogen spillover from metal nanoparticles to oxides is an important process in hydrogenation catalysis and hydrogen storage. In this study, advanced sample fabrication and in situ X-ray photoelectron spectroscopy were used to investigate the local and far-reaching effects of hydrogen spillover in a platinum-ceria catalyst. The results showed that at low temperatures, hydrogen spillover led to the formation of surface O-H on the whole ceria surface, extending microns away from the platinum. These findings demonstrate the impact of hydrogen on the entire catalyst surface and its involvement in catalysis and restructuring.