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Highly Active and Stable Iridium Pyrochlores for Oxygen Evolution Reaction
journal contribution
posted on 2017-05-31, 00:00 authored by Dmitry Lebedev, Mauro Povia, Kay Waltar, Paula M. Abdala, Ivano E. Castelli, Emiliana Fabbri, Maria V. Blanco, Alexey Fedorov, Christophe Copéret, Nicola Marzari, Thomas J. SchmidtProton
exchange membrane water electrolysis (PEMWE) is a promising
technology for electricity-to-fuel conversion which allows for direct
production of hydrogen from water. One of the key problems limiting
widespread implementation of PEMWE into energy systems is the sluggish
kinetics of the anodic process: the oxygen evolution reaction (OER).
Additionally, state-of-the-art OER materials contain large amounts
of low abundant noble metals (Ru, Ir), and therefore, development
of low-cost, highly active and stable OER catalysts remains an important
challenge. We developed a synthetic approach to the iridium pyrochlores–complex
oxides of iridium with reduced content of the noble metal as compared
to IrO2. The materials were synthesized from molten sodium
nitrate (Adams fusion method) at moderate temperatures (500–575
°C) and consist of highly crystalline iridium pyrochlore nanoparticles
with surface areas of up to 40 m2 g–1, which is a significant improvement compared to the traditional
high temperature solid-state synthesis. Electrochemical measurements
in acidic media showed that yttrium and bismuth pyrochlore catalysts
possess high OER activity approaching the activity of state-of-the-art
IrO2 nanoparticles. High intrinsic activities and stability
behavior of yttrium iridium catalysts were correlated with the formation
of the highly active IrOx surface layer
due to leaching of the Y3+ cations into the electrolyte
solution, revealed both experimentally and computationally using density
functional theory calculations.
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Keywords
surface areasIrO x surface layertheory calculationsiridium pyrochlore nanoparticlesOxygen Evolution Reaction Proton exchange membrane water electrolysisStable Iridium Pyrochloresoxygen evolution reactionyttrium iridium catalystsElectrochemical measurementsanodic processAdams fusion methodIrO 2 nanoparticlesstability behaviorIrO 2OER catalystselectricity-to-fuel conversionPEMWEenergy systemselectrolyte solutionOER activityacidic mediaOER materialsbismuth pyrochlore catalystssodium nitrate