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Bismuth rridium oxide oxygen evolution catalyst from hydrothermal synthesis

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Sardar, Kripasindhu, Ball, Sarah C., Sharman, Jonathan D. B., Thompsett, David, Fisher, Janet M., Smith, Richard A. P., Biswas, P. K. (Pabitra K.), Lees, Martin R., Kashtiban, Reza J., Sloan, Jeremy and Walton, Richard I. (2012) Bismuth rridium oxide oxygen evolution catalyst from hydrothermal synthesis. Chemistry of Materials, Volume 24 (Number 21). pp. 4192-4200. doi:10.1021/cm302468b

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Official URL: http://dx.doi.org/10.1021/cm302468b

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Abstract

We present a detailed characterization of the pyrochlore Bi2Ir2O7 prepared by a one-step hydrothermal synthesis route from aqueous sodium hydroxide solution of NaBiO3·2H2O and IrCl3·5H2O in the presence of Na2O2 at 240 °C. Using 5 M NaOH solution as the reaction medium, a fine powder of polycrystalline Bi2Ir2O7 with an average crystal size of 10 nm and surface area of 46 m2 g–1 is produced. Structure refinement against powder neutron diffraction reveals a stoichiometric pyrochlore with no evidence for significant oxide-ion defects. X-ray absorption near-edge structure (XANES) spectra recorded at both metal LIII-edges show that, although Bi is present solely as Bi3+, there is evidence for the oxidation of iridium slightly beyond +4. This would suggest some surface oxidation of iridium, which is also shown by X-ray photoelectron spectroscopy (XPS) measurements. Magnetization data, as a function of temperature, show that the system is paramagnetic down to a temperature of 2 K, while the electrical conductivity shows hydrothermal Bi2Ir2O7 to be a metallic conductor. In electrochemical tests, performed on rotating disk electrodes fabricated from the powdered iridate and Nafion solution, the material shows oxygen evolution activity in acidic solution, comparable to the most active precious-metal oxide materials, with reproducibility over >1000 cycles, demonstrating the formation of robust electrodes.

Item Type: Journal Article
Divisions: Faculty of Science, Engineering and Medicine > Science > Chemistry
Faculty of Science, Engineering and Medicine > Science > Physics
Journal or Publication Title: Chemistry of Materials
Publisher: American Chemical Society
ISSN: 0897-4756
Official Date: 2012
Dates:
DateEvent
2012UNSPECIFIED
Volume: Volume 24
Number: Number 21
Page Range: pp. 4192-4200
DOI: 10.1021/cm302468b
Status: Peer Reviewed
Publication Status: Published
Access rights to Published version: Restricted or Subscription Access

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