Author ORCID Identifier

Julie N. Renner

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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 1.48 V, 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 O–O 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.


core-shell, electrolysis, IrO 2, oxygen evolution reaction mechanism, RuO 2

Publication Title

Journal of Electroanalytical Chemistry



First Page


Last Page



DE-SC0012704; DE-FG02-12ER86531; DE-AC02-06CH11357; 21336003; 2014CB239703


Office of Basic Energy Science, U.S. Department of Energy; Office of Energy Efficiency and Renewable Energy; Office of Science, U.S. Department of Energy; National Natural Science Foundation of China; Major Basic Research Program of China


© 2017 Published by Elsevier


This is a peer reviewed Accepted Manuscript of an article published in its final form in Journal of Electroanalytical Chemistry, available at:



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