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.

Microkinetic modeling using energies from DFT and scaling relations to reveal roles of water in aqueous phase reforming of glycerol.

A significant number of heterogeneously-catalyzed chemical processes occur under liquid conditions, but simulating catalyst function under such conditions is challenging when it is necessary to include the solvent molecules. The bond breaking and forming processes modeled in these systems necessitate the use of quantum chemical methods. Since molecules in the liquid phase are under constant thermal motion, simulations must also include configurational sampling. This means that multiple configurations of liquid molecules must be simulated for each catalytic species of interest. The goal of the protocol presented here is to generate and sample trajectories of configurations of liquid water molecules around catalytic species on flat transition metal surfaces in a way that balances chemical accuracy with computational expense. Specifically, force field molecular dynamics (FFMD) simulations are used to generate configurations of liquid molecules that can subsequently be used in quantum mechanics-based methods such as density functional theory or ab initio molecular dynamics. To illustrate this, in this manuscript, the protocol is used for catalytic intermediates that could be involved in the pathway for the decomposition of glycerol (C 3 H 8 O 3). The structures that are generated using FFMD are modeled in DFT in order to estimate the enthalpies of solvation of the catalytic species and to identify how H 2 O molecules participate in catalytic decompositions.

Reaction energies and activation barriers for dehydrogenation reactions of methanol derivatives under realistic liquid water configurations using a multiscale method.