In situ characterization is essential to capture the structure of catalytically active sites. However, the catalyst structure and process are extremely complex and to understand specific catalytic phenomena, simpler model systems should be used that capture the phenomena. To understand the influence of support on the phenomenon of spillover, we deposited pairs of platinum and iron oxide particles with a nano-meter precise distance on a support, either reducible, titania, or non-reducible alumina. Thus, on a single surface pairs with controlled distance between the platinum and iron oxide particles were produced. Such system is ideal to determine the influence of distance on the spillover of hydrogen over a support, provided that the structure of individual particles can be simultaneously determined. Using a photo-emission electron microscope at the Swiss Light Source, we were able to measure the structure of each of the iron oxide particles individually.<br/>Exposure of the titania system to hydrogen leads to partial surface reduction of titania, and hydrogen rapidly covers the complete surface enabling reduction of species away from the platinum, which is needed to dissociate molecular hydrogen. Spillover on such support occurs. On alumina, the situation is more complex and evidence is collected of the existence of a gradient of adsorbed hydrogen away from the platinum particle. Theoretical simulations suggested that diffusion of hydrogen competes with desorption as molecular hydrogen. Spectroscopic analysis of the alumina surface identified the existence of three-coordinate aluminum, which are the likely adsorption sites for hydrogen. Overall, spillover of hydrogen on non-reducible alumina is unlikely, but is not negligible.<br/>

Using x-rays to determine the role of support in hydrogen spillover

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.