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Easy Accommodation of Different Oxidation States in Iridium Oxide Nanoparticles with Different Hydration Degree as Water Oxidation Electrocatalysts
journal contribution
posted on 2015-09-04, 00:00 authored by Alessandro Minguzzi, Cristina Locatelli, Ottavio Lugaresi, Elisabetta Achilli, Giuseppe Cappelletti, Marco Scavini, Mauro Coduri, Paolo Masala, Benedetta Sacchi, Alberto Vertova, Paolo Ghigna, Sandra RondininiIn
this paper, we present a comprehensive study on low hydration Ir/IrO2 electrodes, made of an Ir core and an IrO2 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/E curves. The activity of these materials is compared and
discussed in the light of our most recent results on hydrous IrOx. The main conclusion of this study is that the Ir core is noninteracting
with the IrOx 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 IrOx material.