Regensburg 2016 – scientific programme
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O: Fachverband Oberflächenphysik
O 60: Chemistry at Solid/Liquid Interfaces
O 60.7: Talk
Wednesday, March 9, 2016, 16:45–17:00, S052
Structure Sensitivity of the Oxygen Evolution Reaction on Cobalt(II,III) Oxide — •Craig Plaisance1, Karsten Reuter1, and Rutger van Santen2 — 1Technische Universität München, Germany — 2Technische Universiteit Eindhoven, The Netherlands
Quantum chemical calculations and kinetic simulations were used to examine the structure sensitivity of the oxygen evolution reaction on several surface terminations of Co3O4 [1]. Three characteristically different active sites were identified, all of which carry out O-O bond formation by nucleophilic attack on an oxo coordinated by one to three Co cations. A method was developed to calculate the turnover frequency of oxygen evolution as a function of overpotential, and it was found that three overpotential ranges exist, each with a different active site dominating. At low overpotentials an oxo coordinated to two Co(IV) and one Co(II) at a step edge of the (311) surface is most active. At medium overpotentials, the active site switches to an oxo coordinated to two Co(IV) on the A termination of the (110) surface, and at high overpotentials, to an oxo coordinated to a single Co(V) on the B termination of the (110) surface. The less coordinated oxos are intrinsically more reactive but require a higher overpotential to oxidize to the active state. Analysis of the electronic structure indicates that the intrinsic reactivity is related to the energy to transfer a hole from an oxidized Co cation to the oxo, with the less coordinated sites requiring the least energy.
[1] C.P. Plaisance and R.A. van Santen, J. Am. Chem. Soc., 2015, 137 (46), 14660-72.