Issue 45, 2021

Influence of the cobalt content in cobalt iron oxides on the electrocatalytic OER activity

Abstract

Sub 10 nm cobalt ferrite CoxFe3−xO4 (x ≤ 1.75) nanoparticles and cobalt-rich wüstite (Cox/3Fe(1−x)/3)O nanoparticles (x ≥ 2) were synthesized in a solvothermal approach and characterized by powder X-ray diffraction (PXRD), selected area electron diffraction (SAED), transmission electron microscopy (TEM) as well as energy dispersive X-ray spectroscopy (EDX), IR, Raman, and 57Fe-Mössbauer spectroscopy. Their electrocatalytic activity in the oxygen evolution reaction (OER) was evaluated and the active state formation was tracked by operando X-ray absorption spectroscopy (XAS). Our studies demonstrate that the cobalt-rich wüstite (Cox/3Fe(1−x)/3)O nanoparticles underwent a phase-transformation into the spinels CoxFe3−xO4 (x ≥ 2) under the applied OER conditions. The overpotential η10 at 10 mA cm−2, serving as a benchmark for the OER activity of the cobalt ferrite nanoparticles in alkaline media, was lower than that of magnetite Fe3O4 even with low cobalt concentrations, reaching a minimum of 350 mV for Co2.25Fe0.75O4 with a Tafel slope of 50 mV dec−1. Finally, we identified that the catalytic activity is linked to the nanoparticle size as well as to the degree of Co redox activity and change in coordination during OER.

Graphical abstract: Influence of the cobalt content in cobalt iron oxides on the electrocatalytic OER activity

Supplementary files

Article information

Article type
Paper
Submitted
03 Aug 2021
Accepted
15 Okt 2021
First published
15 Okt 2021
This article is Open Access
Creative Commons BY-NC license

J. Mater. Chem. A, 2021,9, 25381-25390

Influence of the cobalt content in cobalt iron oxides on the electrocatalytic OER activity

S. Saddeler, G. Bendt, S. Salamon, F. T. Haase, J. Landers, J. Timoshenko, C. Rettenmaier, H. S. Jeon, A. Bergmann, H. Wende, B. Roldan Cuenya and S. Schulz, J. Mater. Chem. A, 2021, 9, 25381 DOI: 10.1039/D1TA06568H

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