Stability and catalytic performance of reconstructed Fe₃O₄(001) and Fe₃O₄(110) surfaces during oxygen evolution reaction

M. Müllner, M. Riva, F. Kraushofer, M. Schmid, G. S. Parkinson, S. F. L. Mertens, U. Diebold

J. Phys. Chem. C 123 (2019) 8304-8311

Earth-abundant oxides are promising candidates as effective and low-cost catalysts for the oxygen evolution reaction (OER) in alkaline media, which remains one of the bottlenecks in electrolysis and artificial photosynthesis. A fundamental understanding of the atomic-scale reaction mechanism during OER could drive further progress, but a stable model system has yet to be provided. Here we show that Fe₃O₄ single crystal surfaces, prepared in ultra high vacuum (UHV) are stable in alkaline electrolyte in the range pH 7-14 and under OER conditions in 1 M NaOH. Fe₃O₄(001) and (110) surfaces where studied with X-ray photoelectron spectroscopy, low-energy electron diffraction and scanning tunneling microscopy in UHV, and atomic force microscopy in air. Fe₃O₄(110) is found to be more reactive for oxidative water splitting than (001)-oriented magnetite samples. Magnetite is electrically conductive, the structure and properties of its major facets are well understood in UHV. With these newly obtained results we propose magnetite (Fe₃O₄) as a promising model system for further mechanistic studies of electrochemical reactions in alkaline media and highly oxidizing conditions.

Corresponding author: Gareth Parkinson (parkinson).

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