ab initio Composite Procedure for Accurate Prediction of Standard Redox Potentials

Project: Research

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Description

Oxidation-reduction (redox) reactions cover a large and diverse body of familiar chemical and physical processes such as fire, rusting, browning of fruit, respiration and photosynthesis. In the redox reactions such as water oxidation and CO2 reduction catalyzed by electrocatalysts, the efficiency of the electrocatalyst is normally evaluated as a function of two interrelated quantities - rate and overpotential.  The overpotential is the difference between the applied potential and the equilibrium potential for the reaction under given reaction conditions. This equilibrium potential is further related to the standard reduction (or oxidation) potential (Ered or Eox), via the Nernst equation. Thus, the Ered (or Eox) is one of the key electrochemical properties governing the efficiency of electrocatalyst.  Experimentally, the Ered (or Eox) can be accurately measured by mean of cyclic voltammetry and nevertheless the theoretical determination of Ered or Eox in solvated medium is still in its developing stage. Knowledge on thermochemical properties in both gaseous state and condensed phase is of fundamental importance.  By determining the value of thermochemical properties such as ionization energy, bond dissociation energy, proton affinity, activation energy and heat of formation, one can easily foresee the reactivity in chemical reactions.  The ab initio predictions of the above thermochemical properties values are so mature that a number of theoretical composite procedures with high reliability and accuracy have been developed in last twenty years. For example, method like the Gaussian-n (Gn, n = 1 - 4), has been implemented in general quantum chemistry software and made available to computational and generic chemists.  The accuracy for thermochemistry predictions, in general, is ~2-4 kJ/mol. However, the composite methods are limited to gas-phase molecules; none of them is targeted for predictions of Eored for redox reactions.  In spite of the importance of redox reactions in chemistry, the development of composite theoretical method for the Eored predictions in solvent and solution environment, especially for transition metal-containing species is lag behind. This proposal seeks financial support todevelop an ab initio composite procedure for the predictions of standard redoxpotentials in aqueous and non-aqueous medium;assess the performance of the composite procedure by comparing the results with theavailable Ered values for metal containing species;apply the composite procedure to predict Ered of biologically and chemicallyimportant redox active species.

Detail(s)

Project number9042707
Grant typeGRF
StatusActive
Effective start/end date1/10/18 → …