Enhancing Electrochemical Water-Splitting Kinetics by Polarization-Driven Formation of Near-Surface Iron(0): An In Situ XPS Study on Perovskite-Type Electrodes

In the search for optimized cathode materials for high‐temperature electrolysis, mixed conducting oxides are highly promising candidates. This study deals with fundamentally novel insights into the relation between surface chemistry and electrocatalytic activity of lanthanum ferrite based electrolys...

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Published in:Angewandte Chemie International Edition 2015-02, Vol.54 (9), p.2628-2632
Main Authors: Opitz, Alexander K., Nenning, Andreas, Rameshan, Christoph, Rameshan, Raffael, Blume, Raoul, Hävecker, Michael, Knop-Gericke, Axel, Rupprechter, Günther, Fleig, Jürgen, Klötzer, Bernhard
Format: Article
Language:English
Subjects:
Calcium Compounds - chemistry
Communications
electrocatalysis
Electrochemical Techniques
Electrodes
heterogeneous catalysis
Iron - chemistry
Kinetics
Lanthanum - chemistry
Oxides - chemistry
perovskites
Photoelectron Spectroscopy
solid oxide electrolysis cells
Strontium - chemistry
Surface Properties
thin-film electrodes
Titanium - chemistry
Water - chemistry
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Summary:In the search for optimized cathode materials for high‐temperature electrolysis, mixed conducting oxides are highly promising candidates. This study deals with fundamentally novel insights into the relation between surface chemistry and electrocatalytic activity of lanthanum ferrite based electrolysis cathodes. For this means, near‐ambient‐pressure X‐ray photoelectron spectroscopy (NAP‐XPS) and impedance spectroscopy experiments were performed simultaneously on electrochemically polarized La0.6Sr0.4FeO3−δ (LSF) thin film electrodes. Under cathodic polarization the formation of Fe0 on the LSF surface could be observed, which was accompanied by a strong improvement of the electrochemical water splitting activity of the electrodes. This correlation suggests a fundamentally different water splitting mechanism in presence of the metallic iron species and may open novel paths in the search for electrodes with increased water splitting activity. The water‐splitting activity and surface chemistry of perovskite‐type La0.6Sr0.4FeO3−δ thin film electrodes were simultaneously investigated by impedance spectroscopy and synchrotron‐based near‐ambient‐pressure XPS. Upon cathodic polarization, the formation of metallic iron on the electrode surface could be observed, accompanied by a strong improvement of the electrochemical water‐splitting activity.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201409527