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

• DOI: 10.1002/anie.201409527
• Publication Date: 2014-12-30T20:57:34Z
• Authors: Alexander K. Opitz; Andreas Nenning; Christoph Rameshan; Raffael Rameshan; Raoul Blume; Michael Hävecker; Axel Knop‐Gericke; Günther Rupprechter; Jürgen Fleig; Bernhard Klötzer
• Keywords: Titanium; Surface Properties; Iron; Photoelectron Spectroscopy; Water; Large scale facilities for research with photons neutrons and ions; Oxides; Electrochemical Techniques; 02 engineering and technology; Calcium Compounds; 7. Clean energy; Communications; Kinetics; Lanthanum; Strontium; 0210 nano-technology; Electrodes

AbstractIn 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.