Oxygen Reduction in Alkaline Media - a Discussion

ANNA IGNACZAK; RENAT NAZMUTDINOV; LEANDRO PINTO; FERNANDA JUAREZ; PAOLA QUAINO; GUSTAVO BELLETTI; ELIZABETH SANTOS; WOLFGANG SCHMICKLER

Electrocatalysis

Springer

Lugar: Berlin ; Año: 2017

1868-2529

We propose a complete reaction sequence foroxygen reduction in alkaline solutions, in which the first twosteps occur in the outer sphere mode. The oxygen-oxygenbond is broken in the third step, which involves adsorptionof OH, which is desorbed in the last step. We have inves-tigated the sequence by quantum-chemical methods anddetermined the energies of activation. Whether the reactionfollows a four- or a two-electron mechanism, depends criti-cally on the energy of adsorption of OH. We surmise that ourmechanism holds on all electrodes which interact weaklywith oxygen, in particular on gold, silver, and graphite. Weexplain, why Au(100) is a better catalyst than Au(111), whyat high overpotentials the reaction on Au(100)reverts to atwo-electron mechanism, and why this does not happen onsilver.