On calculating reorganization energies for electrochemical reactions using density functional theory and continuum solvation models

An “all theoretical” method of calculating reorganization energies for electrode reactions using a procedure implemented in the commercial quantum calculation package Gaussian is proposed. The procedure relies in calculating both equilibrium and non-equilibrium Gibbs free energies in solution, eliminating the need to calculate separately inner and outer-sphere contributions to the total reorganization energy, while the molecule's real shape is also considered. The procedure is intended as a tool for electrochemists to estimate reliably Marcus-type reorganization energies. The comparison is made for simple electrochemical reactions, for which the metal electrode is considered simply as an electron reservoir. The calculated values show good agreement with experimental ones, typically within 10%. The procedure, while not perfect, yields good estimates for reorganization energies of a large variety of electrode reactions and it is more suitable to be used by electrochemists than other methods.