title: Water-splitting electrocatalysis in acid conditions using ruthenate-iridate pyrochlores.
abstract: The pyrochlore solid solution (Na(0.33)Ce(0.67))2(Ir(1-x)Ru(x))2O7 (0≤x≤1), containing B-site Ru(IV) and Ir(IV) is prepared by hydrothermal synthesis and used as a catalyst layer for electrochemical oxygen evolution from water at pH<7. The materials have atomically mixed Ru and Ir and their nanocrystalline form allows effective fabrication of electrode coatings with improved charge densities over a typical (Ru,Ir)O2 catalyst. An in situ study of the catalyst layers using XANES spectroscopy at the Ir L(III) and Ru K edges shows that both Ru and Ir participate in redox chemistry at oxygen evolution conditions and that Ru is more active than Ir, being oxidized by almost one oxidation state at maximum applied potential, with no evidence for ruthenate or iridate in +6 or higher oxidation states.
authors.affiliation: Department of Chemistry, University of Warwick, Coventry, CV4 7AL (UK); Johnson Matthey Technology Centre, Sonning Common, Reading RG4 9NH (UK).
authors.forename: Kripasindhu
authors.initials: K
authors.lastname: Sardar
authors.forename: Enrico
authors.initials: E
authors.lastname: Petrucco
authors.forename: Craig I
authors.initials: CI
authors.lastname: Hiley
authors.forename: Jonathan D B
authors.initials: JD
authors.lastname: Sharman
authors.forename: Peter P
authors.initials: PP
authors.lastname: Wells
authors.forename: Andrea E
authors.initials: AE
authors.lastname: Russell
authors.forename: Reza J
authors.initials: RJ
authors.lastname: Kashtiban
authors.forename: Jeremy
authors.initials: J
authors.lastname: Sloan
authors.forename: Richard I
authors.initials: RI
authors.lastname: Walton
keywords: X-ray absorption spectroscopy; electrochemistry; hydrothermal synthesis; iridium; ruthenium