X-ray absorption in relation to valency of iridium in sputtered iridium oxide films

Electronic and structural changes induced by the charge storage reaction du e to proton insertion in sputtered iridium oxide films (SIROFs) have been i nvestigated by in situ X-ray absorption spectroscopy at the L-3 edge of iri dium atoms in 1 M H2SO4. The iridium valency is shown to increase from 3 to 3.85 when the potential varies from - 0.2 to + 1 V(SCE). In XANES spectra, the white line peak height and energy position decrease with insertion. Th e fine structures of the spectra have been analyzed and simulated in view o f structural parameter extraction. A correspondence curve is established be tween the interatomic Ir-O distance in the first shell and the iridium vale ncy. A strong decrease of this distance is observed with the oxidation stat e of iridium accompanied by a conspicuous decrease of the Debye-Waller fact or. (C) 1999 Elsevier Science S.A. All rights reserved.