Molecular-Level Details about Liquid H2O Interactions with CO and Sugar Alcohol Adsorbates on Pt(111) Calculated Using Density Functional Theory and Molecular Dynamics
CJ Bodenschatz and S Sarupria and RB Getman, JOURNAL OF PHYSICAL CHEMISTRY C, 119, 13642-13651 (2015).
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 H2O-adsorbate interactions. We obtain ensembles of liquid configurations with classical MD and compute the electronic energies of these systems with DFT. We examine CO, CH2OH, and C(3)H(7)O3 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 H2O molecules arrange around surface intermediates in ways that favor hydrogen bonding, with larger and more hydrophilic intermediates forming significantly more hydrogen bonds With H2O. For example, CO hydrogen- bonds with 1.5 +/- 0.4 nearest neighbor H2O molecules and exhibits an interaction energy With these H2O molecules near 0 (-0.01 +/- 0.09 eV), while CH2OH forms 2.2 +/- 0.6 hydrogen bonds and exhibits an interaction energy of -0.43 +/- 0.07 eV. C(3)H(7)O3 farms 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 H2O molecules that are strongly bound to surface adsorbates, and we find that these H2O 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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