Examinando por Materia "Adsorption energies"

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    Ítem
    Improving DFT-based approaches to study CO2 electroreduction on transition metals
    (Universidad EAFIT, 2021) Rendón Calle, Jessica Alejandra; Calle Vallejo, Federico; Builes Toro, Santiago
    The industrial-scale conversion of electricity obtained from renewable sources is crucial to achieve an economy based on renewable energy. In that scenario, the electrochemical reduction of CO2, offers the possibility of producing some of the most demanded fuels and chemicals in a sustainable way. However, its efficient implementation on industrial scale is limited by factors as the high energy requirements for the product formation, the low selectivity and efficiency of electrolyzers, and the long-term deactivation of the catalysts. Understanding the many aspects that influence the reaction behavior is a challenging task because, apart from solvent and electrolyte effects, there are multiple intermediates, pathways, and products possible under similar operating conditions. In the recent decades this research field has been highly active in theory and experiments, and many studies have focused on finding the main factors that enhance the reaction performance. In this thesis, the electrochemical CO2 reduction is studied using state-of-the-art density functional theory (DFT) simulations, incorporating solvation effects as a crucial factor for improving thermodynamic predictions. To this end, a systematic micro-solvation method was developed to determine the number of hydrogen-bonded water molecules in the first solvation shell and the energetic stabilization granted by those hydrogen bonds. The reduction of CO2 to CO, CH4 and CH3OH on Cu, was considered to test this method, finding very good agreement with experiments without the need to include calculations of reaction kinetics. The estimation of solvation contributions for the CO2 reduction to CO has been extended to other transition metals such as Ag, Au, and Zn, finding significant variations between solvation corrections for the same adsorbates on different metals and finding very good agreement with experimental results. The increase in accuracy of the predictions make possible the development of a semiempirical method to explain the deactivation evidenced experimentally on Cu electrodes during CO2RR to CH4.
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    Ítem
    Substantial improvement of electrocatalytic predictions by systematic assessment of solvent effects on adsorption energies
    (Elsevier B.V., 2020-01-01) Rendón-Calle A.; Builes S.; Calle-Vallejo F.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de Procesos
    Electrocatalytic activities are largely determined by the interplay of adsorbates with substrates and solvents. Although capturing the interactions of those three components is usually arduous, here we provide a simple micro-solvation method to evaluate them in aqueous media. The method helps determine: (a) the number of water molecules making hydrogen bonds with the adsorbates, and (b) the energetic stabilization of the adsorbates by those hydrogen bonds. To evaluate the usefulness of the method, we consider CO2 reduction to CO, CH4, and CH3OH on Cu, Ag, Au, and Zn. Applying the calculated solvation corrections, we find good agreement with experiments in the predicted pathways and onset potentials, with an average error of only 0.07 V. Conversely, models with ad hoc or implicit solvation corrections predict unlikely pathways and onset potentials with considerably larger errors. These results indicate that accurate methods to assess solvent-adsorbate interactions contribute to improve computational electrocatalysis models. © 2020 Elsevier B.V.