(239g) Investigation of Hydrogen Spillover Pathways On a Bimetallic Hydrogenation Catalyst

Hydrogenation processes are of paramount importance in the chemical industry with a vast range of applications in the food, petrochemical and pharmaceutical sectors. Heterogeneous catalysts are widely used for hydrogenation; however, controlling the spillover of hydrogen on catalytic surfaces is challenging. It has recently been shown experimentally that it is possible to achieve this type of control on a Cu/Pd catalyst by reversible adsorption of a spectator molecule (CO).¹ This phenomenon was termed the "molecular cork" effect and can have profound implications in catalysis. In particular, it is possible to trap hydrogen on the catalytic surface at temperatures higher than its normal desorption temperature, thereby increasing the rate of hydrogenation reactions due to the higher reactivity of hydrogen under these conditions. Yet, questions remain with regard to the origins of this phenomenon and how it can be leveraged for the design of improved hydrogenation catalysts.

Motivated by these questions we employ a multiscale computational approach to study the "molecular cork" system. At the molecular level we use density functional theory (DFT) to calculate the energetics and kinetics of CO adsorption onto and desorption from the Pd sites, as well as hydrogen dissociative adsorption and associative desorption in the absence and in the presence of CO. At the catalyst level, we use kinetic Monte Carlo simulation to reproduce the experimental observations and investigate in detail the H₂ dissociation and spillover pathways. Our simulations provide valuable information that cannot be directly accessed by experiments and offer a fundamental understanding of the molecular-level processes underlying the "molecular cork" effect.

References

Marcinkowski, M. D., A. D. Jewell, M. Stamatakis, M. B. Boucher, E. A. Lewis, C. J. Murphy, G. Kyriakou and E. C. H. Sykes, Controlling a Spillover Pathway with the Molecular Cork Effect. Nature Materials, 2013: Accepted for publication.