Effect of Platinum-Support Interactions on Hydride Formation

Catalysts are indispensable to modern life, speeding up chemical reactions and making large-scale manufacturing processes possible. Many commonly used industrial catalysts consist of platinum nanoparticles dispersed on a metal oxide support, such as aluminum oxide. In recent experiments, single hydrogen atoms have been observed to bind linearly to platinum atoms at the surface of the catalyst platinum on gamma-alumina, and little is known about the mechanism responsible for this phenomenon. The goal of this project is to test if these hydrogen atoms come from support-bound hydroxyl groups, and if interactions between platinum and the support influence the extent to which platinum-hydride bonds form. This is important to study as platinum catalysts are necessary for many industrial hydrogenation reactions, in which hydrides could have unstudied effects. To test our hypothesis, we synthesized four different platinum catalysts, varying support type and particle size. Because the platinum-hydride bond is detectable by infrared spectroscopy, we used it to measure hydride bond formation for each catalyst. The platinum-hydride bond was observed only on the two catalysts with a gamma-alumina support, which has hydroxyl groups. However, no hydride formation occurred on the two non-hydroxylated silica supported catalysts, suggesting that only hydroxylated supports facilitate hydride formation. Changing particle size yielded no conclusive results. Our findings suggest the hydrogen atoms in platinum-hydride bonds did transfer from hydroxyl groups bound to the support. They leave further room for investigating what triggers this reverse hydrogen spillover and if manipulating metal-support interactions allows control over hydride formation.

Faculty Mentor: Phillip Christopher

Project Mentor: Ryan Berry