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Quantum chemical modelling of oxygen reduction on cobalt hydroxide and oxyhydroxide

J R Tobias Johnsson Wass ; Itai Panas (Institutionen för kemi- och bioteknik, Oorganisk miljökemi) ; Jon Asbjörnsson ; Elisabet Ahlberg
Journal of Electroanalytical Chemistry Vol. 599 (2007), 2, p. 295-312.
[Artikel, refereegranskad vetenskaplig]

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.

Nyckelord: oxygen reduction, hydrogen peroxide, cobalt oxyhydroxide, cobalt, hydroxide, quantum chemistry, density functional theory, cluster models, SINGLE-CRYSTAL ELECTRODES, DENSITY-FUNCTIONAL THEORY, WATER-ADSORPTION, ALKALINE-SOLUTIONS, OXIDE CLUSTERS, FUEL-CELLS, HYDROLYSIS, ENERGY, ELECTROCATALYSIS, GOLD



Denna post skapades 2007-11-06. Senast ändrad 2010-04-30.
CPL Pubid: 61192

 

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Institutioner (Chalmers)

Institutionen för kemi (2001-2011)
Institutionen för kemi- och bioteknik, Oorganisk miljökemi (2005-2014)

Ämnesområden

Kemi

Chalmers infrastruktur