title: Characterization of Platinum and Iridium Oxyhydrate Surface Layers from Platinum and Iridium Foils.
abstract: Platinum and iridium polycrystalline foils were oxidized electrochemically through anodization to create thin platinum and iridium hydrous oxide layers, which were analyzed through laboratory photoelectron spectroscopy during heating and time series (temperature-programmed spectroscopy). The films contain oxygen in the form of bound oxides, water, and hydroxides and were investigated by depth profiling with high-energy photoelectron spectroscopy. The Pt films are unstable and begin to degrade immediately after removal from the electrolyte to form core-shell structures with a metallic inner core and a hydrous oxide outer shell almost devoid of Pt. However, evidence was found for metastable intermediate states of degradation; therefore, it may be possible to manufacture PtOx phases with increased stability. Heating the film to even 100 °C causes accelerated degradation, which shows that stoichiometric oxides such as PtO2 or PtO are not the active species in the electrolyte. The Ir films exhibit increased stability and higher surface Ir content, and gentle heating at low temperatures leads to a decrease in defect density. Although both layers are based on noble metals, their surface structures are markedly different. The complexity of such hydrous oxide systems is discussed in detail with the goal of identifying the film composition more precisely.
authors.affiliation: Fritz Haber Institute, Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany. benjamin@fhi-berlin.mpg.de.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Johnson
authors.affiliation: Max Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470Mülheim an der Ruhr, Germany.
authors.forename: Chinmoy
authors.initials: C
authors.lastname: Ranjan
authors.affiliation: Fritz Haber Institute, Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany.
authors.forename: Mark
authors.initials: M
authors.lastname: Greiner
authors.affiliation: Fritz Haber Institute, Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany.|Diamond Light Sourc Ltd., Diamond House, Harwell Science and Innovation Campus Didcot, Oxfordshire, OX11 0DE, UK.
authors.forename: Rosa
authors.initials: R
authors.lastname: Arrigo
authors.affiliation: Fritz Haber Institute, Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany.|Johnson Matthey.
authors.forename: Manfred Erwin
authors.initials: ME
authors.lastname: Schuster
authors.affiliation: Helmholtz Zentrum für Materialien und Energie, Hahn-Meitner-Platz 1, 14109, Berlin, Germany.
authors.forename: Britta
authors.initials: B
authors.lastname: Höpfner
authors.affiliation: Helmholtz Zentrum für Materialien und Energie, Hahn-Meitner-Platz 1, 14109, Berlin, Germany.
authors.forename: Mihaela
authors.initials: M
authors.lastname: Gorgoi
authors.affiliation: Helmholtz Zentrum für Materialien und Energie, Hahn-Meitner-Platz 1, 14109, Berlin, Germany.
authors.forename: Iver
authors.initials: I
authors.lastname: Lauermann
authors.affiliation: Fritz Haber Institute, Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Willinger
authors.affiliation: Fritz Haber Institute, Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Knop-Gericke
authors.affiliation: Fritz Haber Institute, Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany.|Max Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470Mülheim an der Ruhr, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Schlögl
mesh_terms: D007495:Iridium / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D010087:Oxides; D014867:Water; D007495:Iridium; D010984:Platinum
keywords: iridium; oxidation; platinum; redox chemistry; surface analysis