(638b) Understanding the Active Facet and Particle Size-Dependent Activity Trends for Phenol Hydrogenation on Pt and Rh Nanoparticles | AIChE

(638b) Understanding the Active Facet and Particle Size-Dependent Activity Trends for Phenol Hydrogenation on Pt and Rh Nanoparticles

Authors 

Barth, I. - Presenter, University of Michigan
Akinola, J., University of Michigan
Lee, J., University of Michigan
Gutiérrez-Tinoco, O., Pacific Northwest National Laboratory
Sanyal, U., Pacific Northwest National Laboratory
Singh, N., University of Michigan
Thermocatalytic hydrogenation (TCH) and electrocatalytic hydrogenation (ECH) are two promising strategies for upgrading biomass-derived compounds to sustainably produce high-energy density fuels and value-added chemicals. However, ECH and TCH are not currently cost competitive with fossil fuels, in part due to low activity and high costs of the catalysts, which often are platinum group metals. ECH and TCH of bio-oils are commonly performed on supported metal nanoparticles (NPs), which have multiple exposed surface facets, not all of which are active for hydrogenation. Further understanding the active sites on metal NPs for hydrogenation can inform catalyst design to improve the reaction rate and minimize the quantity of expensive materials required.

In this work, we study ECH and TCH of phenol, a model bio-oil compound, on Pt and Rh NPs supported on carbon (Pt/C and Rh/C) to identify the active site on Rh/C and explain the activity of Rh/C and Pt/C. We fit phenol TCH rate data on Rh/C to a Langmuir-Hinshelwood model and extract the phenol adsorption energy on the active site to compare with adsorption energies previously measured on terraces and stepped facets. We model phenol hydrogenation on (111) terraces and (221) steps of Pt and Rh using density functional theory and microkinetic modeling to elucidate the relationship between intrinsic kinetics and phenol adsorption strength. We study phenol ECH on Rh/C as a function of particle size and find that larger particles, which have a higher fraction of terrace sites compared to smaller particles, are more active. Ultimately, we find that the (111) terraces of Pt and Rh are active for phenol hydrogenation, which our computational results indicate is due to higher intrinsic activity and weaker phenol adsorption. By providing a better understanding of the active site of Pt/C and Rh/C for phenol hydrogenation, these findings may inform catalyst design.

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