Journal
ACS CATALYSIS
Volume 8, Issue 12, Pages 11773-11782Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.8b00574
Keywords
oxygen evolution reaction; water splitting; transition metal oxides; spinels; density functional theory
Categories
Funding
- German Research Foundation (DFG, Deutsche Forschungsgemeinschaft) [SPP1613, PE883/9-2]
- Center of Computer Science and Simulation (DFG) [INST 20876/209-1 FUGG, INST 20876/243-1 FUGG]
- Collaborative Research Center [TRR247]
- Leibniz Rechenzentrum [pr87ro]
Ask authors/readers for more resources
Using density functional theory calculations with an on-site Hubbard term (DFT+U), we explore the effect of surface termination and cation substitution on the performance of the CoxNi1-xFe2O4(001) surface (x = 0.0, 0.5, 1.0) as an anode material in the oxygen evolution reaction (OER). Different reaction sites (Fe, Co, Ni, and an oxygen vacancy) were investigated at three terminations: the B-layer with octahedrally coordinated Co/Ni and with an additional half and full monolayer of Fe (0.5A and A-layer, respectively). Ni substitution with an equal concentration of Co and Ni (x = 0.5) reduces the overpotential over the end members for the majority of reaction sites. Surface Co cations are identified as the active sites and the ones at the A-layer termination for x = 0.5 exhibit one of the lowest theoretically reported overpotentials of 0.26 V. The effect of the additional iron layer on the active site modification is 2-fold: analysis of the electronic properties and spin densities indicates that the additional Fe layer stabilizes a bulk-like oxidation state of +2 for Co and Ni at the A-layer termination, whereas at the B-layer termination, they are oxidized to 3+. Moreover, the unusual relaxation pattern enables the formation of a hydrogen bond of the OOH intermediate to a neighboring surface oxygen that lowers the reaction free energy of this formerly rate-limiting step, leading to a deviation from the scaling relationship and almost equidistant reaction free-energy steps of intermediates. This renders an example of how a selective surface modification can result in a significant improvement of OER performance.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available