Solvation of furfural at metal|water interfaces: Implications for aqueous phase hydrogenation reactions

Metal|water interfaces are central to understanding aqueous phase heterogeneous catalytic processes. However, it is challenging to model the interactions between metal surfaces, adsorbates and the solvent water molecules at the interface. Herein, we use ab-initio molecular dynamics (AIMD) simulations to study the adsorption of furfural, a platform biomass chemical on several catalytically relevant metal|water interfaces (Pt, Rh, Pd, Cu and Au) at low coverages. We find that furfural adsorption is destabilized on all the metal|water interfaces compared to the metal|vacuum interfaces considered in this work. This destabilization is a result of the energetic penalty associated with the displacement of water molecules near the surface upon adsorption of furfural. This is evidenced by a linear correlation between solvation energy and the change in surface water coverage. To predict solvation energies without the need for computationally expensive AIMD simulations, we demonstrate OH binding energy in vacuum to be a good descriptor to estimate the solvation energies of furfural on different metal|water interfaces. Using microkinetic modeling, we further explain the origin of the activity for furfural hydrogenation on intrinsically strong-binding metals, such as Rh and Pt, under aqueous conditions, i.e., the endothermic solvation energies for furfural adsorption helps prevent surface poisoning. Our work sheds light on the development of active aqueous-phase catalytic systems via rationally tuning the solvation energies of reaction intermediates.