Hydroxide Oxidation and Peroxide Formation at Embedded Binuclear Transition Metal Sites; TM=Cr, Mn, Fe, Co
Artikel i vetenskaplig tidskrift, 2011

Key steps in electro-catalytic water oxidation on binuclear Transition Metal (TM) sites are addressed. These comprise (a) two one-electron oxidation steps of TM-OH moieties to form the corresponding two TM=O oxy-groups, and (b) a chemical step whereby the two oxy-species form a TM-O-O-TM peroxy-bridge. A test rig representing a generic low crystal field oxide support is described and employed. The energetics for said reactions are compared for homo-nuclear Cr(IIIV), Mn(III-V), Fe(II-IV) and Co(II-IV) sites. The uniqueness of the TyrO/TyrOH reference potential for driving said oxidation steps is demonstrated. Hydroxide oxidation on binuclear Mn and Co candidates require an overpotential of approximately 0.5 V relative to the chosen reference potential. Correspondingly, the subsequent O-O bond formation becomes strongly exothermic of the order of 1 eV. Hydroxide oxidation on binuclear CrCr and FeFe systems are exothermic by 0.2-0.4 eV relative to the TyrO/TyrOH reference potential. Consequently, the chemical step for transforming the TM=O moieties to the peroxo species is found to be endothermic on the order of 0.7 eV. These findings suggest that hetero-binuclear sites containing one TM from each class would be optimal. The validity of this concept is demonstrated for the FeCo binuclear site. The results are discussed in the context of experimental observations, which display preference for mixed oxide systems.

magnesium oxyhydroxide support

catalysis

electrocatalysts

Water oxidation

activation energy

binuclear site

test rig

Författare

Michael Busch

Göteborgs universitet

Elisabet Ahlberg

Göteborgs universitet

Itai Panas

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

Physical Chemistry Chemical Physics

1463-9076 (ISSN) 1463-9084 (eISSN)

Vol. 13 15062-15068

Styrkeområden

Nanovetenskap och nanoteknik

Energi

Materialvetenskap

Ämneskategorier

Bearbetnings-, yt- och fogningsteknik

Annan kemiteknik

Annan kemi

Teoretisk kemi