ELECTROCATALYST POTENTIAL DEPENDENT ACTIVATION BARRIERS APPROXIMATED WITH DENSITY FUNCTIONAL THEORY
Open Access
- Author:
- Esopi, Monica Roberta
- Area of Honors:
- Chemical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Dr. Michael John Janik, Thesis Supervisor
Dr. Wayne Roger Curtis, Thesis Honors Advisor - Keywords:
- DFT
electrocatalysis
CO2 reduction
electron transfer - Abstract:
- Density functional theory (DFT) studies of electrocatalytic systems are widespread, but the calculation of activation barriers for elementary steps involving electron and ion transfer remains challenging. A simple and transferable DFT approach to estimate these barriers for inner sphere electrochemical reactions, focusing on approximating the electron transfer coefficient, was studied. The challenge of finding a transition state for an electrochemical reaction step (A*+H++e- → AH*) is met by breaking the electrochemical step down into one electrochemical step (A*+H++e- → A*+H*) and one non-electrochemical step (A*+H* → AH*). The transition state of the non-electrochemical step can be found relatively easily. It is assumed that the transition states for these two reactions are identical at the specific electrode potential (U0) where the true reactant state (A*+H++e-) and the intermediate state (A*+H*) have the same free energy. Once the transition state is located, the activation barrier, Eact0, can be calculated at that potential, U0. The activation barrier can be extrapolated as a function of electrode potential using Butler-Volmer theory, with the symmetry factor estimated by examination of the transition state and reaction coordinate. The methods used to calculate the symmetry coefficient, β, yield values that make sense and fit well with the other data. The first elementary step of CO2 reduction, the hydrogenation of CO2* to COOH*, will be used as a detailed example case for the development of the β calculation methods.