Quantum chemical modelling of oxygen reduction on cobalt hydroxide and oxyhydroxide

• 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.

Subject headings

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Keyword

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

quantum chemistry

Publication and Content Type

ref (subject category)

art (subject category)