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Bismuth Iridium Oxide Oxygen Evolution Catalyst from Hydrothermal Synthesis

DOI: 10.1021/cm302468b DOI Help

Authors: Kripasindhu Sardar (University of Warwick) , Sarah C. Ball (Johnson Matthey Technology Centre, U.K.) , Jonathan D. B. Sharman (Johnson Matthey Technology Centre, U.K.) , David Thompsett (Johnson Matthey Technology Centre, U.K.) , Janet M. Fisher (Johnson Matthey Technology Centre, U.K.) , Richard A. P. Smith (University of Warwick, U.K.) , Pabitra K. Biswas (University of Warwick, U.K.) , Martin R. Lees (University of Warwick) , Reza J. Kashtiban (University of Warwick, U.K.) , Jeremy Sloan (University of Warwick, U.K.) , Richard I. Walton (University of Warwick)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry Of Materials , VOL 24 (21)

State: Published (Approved)
Published: October 2012

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

Journal Keywords: Pyrochlore; Neutron Diffraction; Electrocatalysis; Oxygen Evolution; Xanes

Subject Areas: Chemistry, Materials

Instruments: B18-Core EXAFS

Added On: 07/11/2012 13:16

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