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Reaction mechanism for oxygen evolution on RuO2, IrO2, and RuO2@IrO2 core-shell nanocatalysts
Iridium dioxide, IrO2, is second to the most active RuO2 catalyst for the oxygen evolution reaction (OER) in acid, and is used in proton exchange membrane water electrolyzers due to its high durability. To improve the activity of IrO2-based catalysts, we prepared RuO2@IrO2 core-shell nanocatalysts u...
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Published in: | Journal of electroanalytical chemistry (Lausanne, Switzerland) Switzerland), 2018-06, Vol.819, p.296-305 |
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Main Authors: | , , , , , , , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Iridium dioxide, IrO2, is second to the most active RuO2 catalyst for the oxygen evolution reaction (OER) in acid, and is used in proton exchange membrane water electrolyzers due to its high durability. To improve the activity of IrO2-based catalysts, we prepared RuO2@IrO2 core-shell nanocatalysts using carbon-supported Ru as the template. At 1.48V, the OER specific activity of RuO2@IrO2 is threefold that of IrO2. While the activity volcano plots over wide range of materials have been reported, zooming into the top region to clarify the rate limiting steps of most active catalysts is important for further activity enhancement. Here, we verified theory-proposed sequential water dissociation pathway in which the OO bond forms on a single metal site, not via coupling of two adsorbed intermediates, by fitting measured polarization curves using a kinetic equation with the free energies of adsorption and activation as the parameters. Consistent with theoretical calculations, we show that the OER activities of IrO2 and RuO2@IrO2 are limited by the formation of O adsorbed phase, while the OOH formation on the adsorbed O limits the reaction rate on RuO2.
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•A simple method to prepare active RuO2 and RuO2@IrO2 core-shell nanocatalysts.•Oxygen evolution reaction mechanism on highly active metal dioxides elucidated.•Formation of O and OOH phases limits the activity of IrO2 and RuO2, respectively.•TiO2 appears to be a suitable core for enhancing IrO2 activity for oxygen evolution. |
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ISSN: | 1572-6657 1873-2569 |
DOI: | 10.1016/j.jelechem.2017.10.062 |