Catalytic fuel production and energy generation from biomass-derived compounds generally involve the aqueous phase, and water molecules at the catalyst interface have energetic and entropic consequences on the reaction free energies. These effects are difficult to elucidate, hindering rational catalyst design for these processes and inhibiting their widespread adoption. In this work, we combine density functional theory (DFT) and classical molecular dynamics (MD) simulations to garner molecular-level insights into H 2 O-adsorbate interactions. We obtain ensembles of liquid configurations with classical MD and compute the electronic energies of these systems with DFT. We examine CO, CH 2 OH, and C 3 H 7 O 3 intermediates, which are critical in biomass reforming and direct methanol electrooxidation, on the Pt(111) surface under various explicit and explicit/implicit water configurations. We find that liquid H 2 O molecules arrange around surface intermediates in ways that favor hydrogen bonding, with larger and more hydrophilic intermediates forming significantly more hydrogen bonds with H 2 O. For example, CO hydrogen-bonds with 1.5 ± 0.4 nearest neighbor H 2 O molecules and exhibits an interaction energy with these H 2 O molecules near 0 (-0.01 ± 0.09 eV), while CH 2 OH forms 2.2 ± 0.6 hydrogen bonds and exhibits an interaction energy of -0.43 ± 0.07 eV. C 3 H 7 O 3 forms 6.7 ± 0.9 hydrogen bonds and exhibits an interaction energy of -1.18 ± 0.21 eV. The combined MD/DFT method identifies the number of liquid H 2 O molecules that are strongly bound to surface adsorbates, and we find that these H 2 O molecules influence the energies and entropies of the aqueous systems. This information will be useful in future calculations aimed at interrogating the surface thermodynamics and kinetics of reactions involving these adsorbates.
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© 2015 American Chemical Society.