Volume 57, Issue 39 pp. 12840-12844
Communication

Operando X-Ray Absorption Spectroscopy Shows Iron Oxidation Is Concurrent with Oxygen Evolution in Cobalt–Iron (Oxy)hydroxide Electrocatalysts

Dr. Lisa J. Enman

Dr. Lisa J. Enman

Department of Chemistry & Biochemistry and the Materials Science Institute, University of Oregon, Eugene, OR, 97403 USA

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Dr. Michaela Burke Stevens

Dr. Michaela Burke Stevens

Department of Chemistry & Biochemistry and the Materials Science Institute, University of Oregon, Eugene, OR, 97403 USA

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Meir Haim Dahan

Meir Haim Dahan

Department of Materials Science & Engineering and The Nancy & Stephen Grand Technion Energy Program, Technion—Israel Institute of Technology, Haifa, 3200003 Israel

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Dr. Michael R. Nellist

Dr. Michael R. Nellist

Department of Chemistry & Biochemistry and the Materials Science Institute, University of Oregon, Eugene, OR, 97403 USA

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Prof. Maytal Caspary Toroker

Corresponding Author

Prof. Maytal Caspary Toroker

Department of Materials Science & Engineering and The Nancy & Stephen Grand Technion Energy Program, Technion—Israel Institute of Technology, Haifa, 3200003 Israel

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Prof. Shannon W. Boettcher

Corresponding Author

Prof. Shannon W. Boettcher

Department of Chemistry & Biochemistry and the Materials Science Institute, University of Oregon, Eugene, OR, 97403 USA

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First published: 15 August 2018
Citations: 149

Graphical Abstract

Fe-containing Co and Ni (oxy)hydroxides are the fastest-known catalysts for water oxidation in alkaline conditions. Fe is essential to the high activity, but its role in the mechanism is under active investigation. Now it is shown that oxygen evolution is concurrent with the oxidation of Fe cations and shortening of Fe−O bonds. The results are consistent with density functional theory calculations and may indicate Fe-based active sites.

Abstract

Iron cations are essential for the high activity of nickel and cobalt-based (oxy)hydroxides for the oxygen evolution reaction, but the role of iron in the catalytic mechanism remains under active investigation. Operando X-ray absorption spectroscopy and density functional theory calculations are used to demonstrate partial Fe oxidation and a shortening of the Fe−O bond length during oxygen evolution on Co(Fe)OxHy. Cobalt oxidation during oxygen evolution is only observed in the absence of iron. These results demonstrate a different mechanism for water oxidation in the presence and absence of iron and support the hypothesis that oxidized iron species are involved in water-oxidation catalysis on Co(Fe)OxHy.

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