(597a) Explaining the Activity Dependence on Particle Size for Phenol Hydrogenation on Pt and Rh By Identifying the Active Facet
AIChE Annual Meeting
Thursday, November 11, 2021 - 12:30pm to 12:48pm
To this end we identify the active facet for phenol ECH and TCH on Pt and Rh that has optimal surface properties (high reaction rate constant and optimal surface coverages of the reacting bio-oil species). We measured the phenol TCH turnover frequency on Rh in the kinetic regime at varying phenol concentrations and fit the rate data to a Langmuir-Hinshelwood model, to extract the phenol adsorption energy on the active facet of Rh. We showed that the active facet for phenol TCH and ECH on both Rh and Pt is the facet that binds phenol very weakly due to water displacement, which we attribute to the (111) facets through density functional theory and microkinetic modelling. Finally, we show that as we increase the fraction of the active (111) facets by increasing the Pt and Rh NPs sizes, the measured ECH turnover frequencies are much higher compared to the smaller particles, further confirming that the (111) facets dominate the catalytic turnover. Ultimately our studies show that Pt and Rh nanoparticles are almost inactive at small particle sizes (e.g., 2 nm) because of the high abundance of inactive step sites.