4 years ago

Oxygen Reduction in Alkaline Media—a Discussion

Wolfgang Schmickler, Anna Ignaczak, Leandro Moreira de Campos Pinto, Aleksej Goduljan, Renat Nazmutdinov, Paola Quaino, Elizabeth Santos, Fernanda Juarez, Gustavo Belletti

Abstract

We propose a complete reaction sequence for oxygen reduction in alkaline solutions, in which the first two steps occur in the outer sphere mode. The oxygen-oxygen bond is broken in the third step, which involves adsorption of OH, which is desorbed in the last step. We have investigated the sequence by quantum-chemical methods and determined the energies of activation. Whether the reaction follows a four- or a two-electron mechanism, depends critically on the energy of adsorption of OH. We surmise that our mechanism holds on all electrodes which interact weakly with oxygen, in particular on gold, silver, and graphite. We explain, why Au(100) is a better catalyst than Au(111), why at high overpotentials the reaction on Au(100) reverts to a two-electron mechanism, and why this does not happen on silver.

Graphical Abstract

We propose a mechanism for oxygen reduction in alkaline solution and support each step by theoretical calculations based on DFT and on our own theory. In particular we explain the central role of OH adsorption in the breaking of the oxygen-oxygen bond

Publisher URL: https://link.springer.com/article/10.1007/s12678-017-0365-y

DOI: 10.1007/s12678-017-0365-y

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