(677d) Understanding Adsorption of Model Bio-Oil Compounds in Aqueous-Phase from First-Principles

Producing transportation fuels and chemicals through the valorization of biomass-derived molecules is a promising strategy to decrease our reliance on fossil fuels. Aqueous-phase electrocatalytic hydrogenation driven with renewable electricity can be used to hydrogenate and deoxygenate the mixture of organics produced from biomass pyrolysis, thus providing a route to produce CO₂-neutral chemicals from a renewable feedstock. Unfortunately, important aqueous-phase phenomena at the solvent/catalyst interface, such as the adsorption of organics, are not well understood, which makes it challenging to predict reaction rates.

In this talk, we will discuss several approaches for estimating aqueous-phase adsorption energies of model bio-oil compounds (i.e., phenol, benzaldehyde, furfural, benzyl alcohol, and cyclohexanol) on catalytically relevant facets of polycrystalline Pt and Rh.¹ Through direct comparison with experimentally determined aqueous-phase adsorption energies, we will explain how gas-phase and implicit solvent modeling techniques, which are commonly used to approximate aqueous-phase behavior, fail to describe aqueous-phase adsorption trends. Specifically, these techniques predict the aqueous-phase enthalpy of adsorption of model compounds to be ~50-250 kJ mol^-1 more exothermic than what is measured experimentally. We will show that accounting for solvent displacement at the solvent/catalyst interface using a bond-additivity model² based on first-principles calculations yields much improved agreement with experimental measurements. These results highlight the necessity of properly accounting for the effect of solvent displacement at the metal interface when modeling adsorption of organic molecules relevant to condensed-phase catalytic reactions, particularly those with large adsorption footprints such as aromatics. This bond-additivity framework can aid in the understanding of how solvents impact adsorption from first-principles. By quantifying a solvent’s effect on organic adsorption, this model may help rationalize the selection of a solvent environment to tune condensed-phase catalytic rates.

References:

(1) Akinola, J. et al. ACS Catal. 2020, 4929–4941.

(2) Singh, N.; Campbell, C. T. ACS Catal. 2019, 9, 8116–8127.