(216e) Modeling Electrochemical Reactions:  DFT-Based Models Including Explicit Solvation, Electrolyte, and Electrochemical Potential | AIChE

(216e) Modeling Electrochemical Reactions:  DFT-Based Models Including Explicit Solvation, Electrolyte, and Electrochemical Potential

Authors 

Goodpaster, J. - Presenter, University of Minnesota Twin Cities
Modeling Electrochemical Reactions: DFT-Based Models Including

Explicit Solvation, Electrolyte, and Electrochemical Potential

Jason D. Goodpaster* 

Department of Chemistry, University of Minnesota Twin Cities, Minneapolis, Minnesota 55455, USA

*Corresponding author: jgoodpas@umn.edu

I report an electrochemical model based on periodic Kohn-Sham Density Functional Theory (DFT) that includes the effects of the electrochemical potential, solvent, and electrolyte. In this model, the electrode surface and all adsorbates are treated using DFT. In the region close to the surface, the solvent is treated explicitly, whereas in the region far from the surface the solvent is treated using a continuum dielectric. The electrolyte ions are implicitly represented by a linearized Poisson-Boltzmann model.1,2 The electrode potential was calculated from the Fermi energy. The Fermi energy can be varied by changing the number of electrons in the simulation cell; therefore, the electrochemical potential was set by calculating the number of electrons the simulation cell required for a specific Fermi energy.3 Using this model, free energy profiles for a reaction can be calculated as a function of the applied potential. The free energy of activation for each elementary step can then used to determine the rate coefficient for that step and combined with microkinetic models to determine the rate of product formation.

I applied this model to investigate the mechanistic pathways by which CO2 on copper and silver surfaces are electrochemically reduced.3,4 I compare this model to vacuum DFT, implicit solvation DFT, explicit solvation DFT, and electrochemical potential DFT models. Our results demonstrated that including electrochemical potential is critical to accurate calculations of free energy barriers and kinetics for electrochemical reactions. Additionally, we show that for some reactions explicit solvation plays an important role in solvating adsorbed intermediates. Finally, I discuss progress in using these free energies for microkinetic modeling.

References:

  1. K. Letchworth-Weaver and T. A. Arias Phys. Rev. B 86, 075140 (2012).
  2. K. Mathew, R. Sundararaman, K. Letchworth-Weaver, T. A. Arias, and R. G. Hennig.
    J. Chem. Phys. 140, 084106 (2014).
  3. J. D. Goodpaster, Alexis T. Bell, and M. Head-Gordon J. Phys. Chem. Lett. 7, 1471 (2016).
  4. J. D. Goodpaster, Alexis T. Bell, and M. Head-Gordon in prep.