Quantum chemical modelling of oxygen reduction on cobalt hydroxide and oxyhydroxide
Artikel i vetenskaplig tidskrift, 2007

Quantum chemistry has been employed to analyse the experimentally observed production of H2O2 during electrochemical reduction of O-2 on cobalt oxyhydroxide, CoOOH(s). The site for O-2 reduction was modelled using both small hydrated Co hydroxide clusters and periodic slab models of a step edge site. A catalytic site was found for the Co(II) model cluster, Co(OH)(2)(H2O)(7), which was also found in the step edge models. However, the site was found to bind O-3(2) very loosely and the Co(II) site alone displayed no electron affinity. The reduction reaction was initiated by adding an electron with O-2 present at the Co(II) site. This produces a superoxide ligand, which upon protonation is able to undergo further reduction to HO2- as Co(III) is formed at the site. Adding a second electron leads to detachment of HO2- as Co(II) is restored. A catalytic redox cycle is presented based on this understanding. The reduction behaviour explains why O-2 is readily reduced on p-type CoOOH at potentials where H2O2 is reduced at a low rate only. O-2 has the ability to introduce new charge carriers into the electrode, which means that the current is limited by charge transfer kinetics and not the electrical properties of the electrode material. H2O2 cannot produce additional charge carriers, and the electrode material limits the current.

quantum chemistry

ENERGY

cobalt

density functional theory

SINGLE-CRYSTAL ELECTRODES

oxygen reduction

DENSITY-FUNCTIONAL THEORY

HYDROLYSIS

OXIDE CLUSTERS

ELECTROCATALYSIS

FUEL-CELLS

GOLD

cobalt oxyhydroxide

hydrogen peroxide

ALKALINE-SOLUTIONS

cluster models

WATER-ADSORPTION

hydroxide

Författare

J R Tobias Johnsson Wass

Göteborgs universitet

Itai Panas

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

Jon Asbjörnsson

Göteborgs universitet

Elisabet Ahlberg

Göteborgs universitet

Journal of Electroanalytical Chemistry

1572-6657 (ISSN)

Vol. 599 2 295-312

Ämneskategorier

Kemi

DOI

10.1016/j.jelechem.2006.05.009