10.1021/acscatal.5b01281.s001 Alessandro Minguzzi Alessandro Minguzzi Cristina Locatelli Cristina Locatelli Ottavio Lugaresi Ottavio Lugaresi Elisabetta Achilli Elisabetta Achilli Giuseppe Cappelletti Giuseppe Cappelletti Marco Scavini Marco Scavini Mauro Coduri Mauro Coduri Paolo Masala Paolo Masala Benedetta Sacchi Benedetta Sacchi Alberto Vertova Alberto Vertova Paolo Ghigna Paolo Ghigna Sandra Rondinini Sandra Rondinini Easy Accommodation of Different Oxidation States in Iridium Oxide Nanoparticles with Different Hydration Degree as Water Oxidation Electrocatalysts American Chemical Society 2015 Different Hydration Degree XRPD Iridium Oxide Nanoparticles IrOx IrO 2 shell HR pair distribution function Water Oxidation ElectrocatalystsIn material synchrotron radiation techniques TEM operando XAS experiments Different Oxidation States PDF transmission electron microscopy Ir core 2015-09-04 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Easy_Accommodation_of_Different_Oxidation_States_in_Iridium_Oxide_Nanoparticles_with_Different_Hydration_Degree_as_Water_Oxidation_Electrocatalysts/2134570 In this paper, we present a comprehensive study on low hydration Ir/IrO<sub>2</sub> electrodes, made of an Ir core and an IrO<sub>2</sub> shell, that are designed and synthesized with an innovative, green approach, in order to have a higher surface/bulk ratio of Ir–O active centers. Three materials with different hydration degrees have been deeply investigated in terms of structure and microstructure by means of transmission electron microscopy (TEM) and synchrotron radiation techniques such as high-resolution (HR) and pair distribution function (PDF) quality X-ray powder diffraction (XRPD), X-ray absorption spectroscopy (XAS), and for what concerns their electrochemical properties by means of cyclic voltammetry and steady-state <i>I</i>/<i>E</i> curves. The activity of these materials is compared and discussed in the light of our most recent results on hydrous IrO<sub><i>x</i></sub>. The main conclusion of this study is that the Ir core is noninteracting with the IrO<sub><i>x</i></sub> shell, the latter being able to easily accommodate Ir in different oxidation states, as previously suggested for the hydrated form, thus explaining the activity as electrocatalysts. In addition, in operando XAS experiments assessed that the catalytic cycle involves Ir­(III) and (V), as previously established for the highly hydrated IrO<sub><i>x</i></sub> material.