Research Article In Situ Dispersive EXAFS in Electrocatalysis: The Investigation of the Local Structure of IrO  in Chronoamperometric Conditions as a Case Study Elisabetta Achilli, 1 Alessandro Minguzzi, 2 Ottavio Lugaresi, 2 Cristina Locatelli, 2 Sandra Rondinini, 2 Giorgio Spinolo, 1 and Paolo Ghigna 1 1 Dipartimento di Chimica, Universit` a di Pavia, Via Taramelli 16, 27100 Pavia, Italy 2 Dipartimento di Chimica, Universit` a degli Studi di Milano, Via Golgi 19, 20133 Milano, Italy Correspondence should be addressed to Paolo Ghigna; paolo.ghigna@unipv.it Received 22 October 2014; Revised 16 December 2014; Accepted 18 December 2014; Published 31 December 2014 Academic Editor: Davidson Sajan Copyright © 2014 Elisabetta Achilli et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. An in situ study with dispersive EXAFS (Extended X-Ray Absorption Spectroscopy) at the Ir-L III edge is performed to characterize Electrodeposited Iridium Oxide Films (EIROF) under chronoamperometric conditions. he technique monitors the local chemical environment and electronic structure of iridium during the oxidation of Ir(III) to Ir(IV) with a time resolution of milliseconds. he study is performed in both acidic and basic media. he Fourier transforms of the time-resolved EXAFS signals clearly show that the short-range structure of Ir is similar to that of rutile-type IrO 2 and is maintained during the reaction, thus accounting for the lexibility of the structure of the electrode material in accommodating diferent oxidation states. From a more general point of view, the work demonstrates the capabilities of in situ experiments based on state-of-the-art dispersive EXAFS in clarifying the mechanistic aspects of electrochemical processes. 1. Introduction When dealing with the mechanism and the kinetics of heterogeneous catalytic reactions, one of the main challenges is to investigate the processes with suicient time resolution. he same purpose lies in the investigation of electrocatalytic reactions [1], where the catalysts need to be deposited onto or chemically bound (permanently or just by charge transfer) to a proper conductive support. In order to obtain the maximum number of available active catalytic sites, highly hydrated ilms and nanostructured materials are usually employed [2]. he observation of changes (in terms of state of charge, local geometric and electronic environment, and structural disorder), linked to the catalytic cycle, does lead to useful information for understanding important mechanistic and kinetic aspects [3, 4]. hanks to the advent of synchrotron radiation sources it has become possible to exploit the ine structure of the absorption coeicient (XAS: X-Ray Absorption Spectroscopy) in order to get information about both the local geometry and electronic structure [5]. Many XAS experiments have been performed onto electrochemical systems both in transmission and in luorescence mode. However, one of the main downsides associated with this technique is the time needed for the monochromator to scan over a desired energy range and to settle between movements. A strategy to overcome this limitation is represented by the so-called QUICK-XAS [6] technique, in which the angle of the monochromator is continuously varied. his setup allows acquiring an XAS spectrum in seconds or fractions of seconds. Nevertheless, it should be noted that the time reso- lution needed to investigate the kinetics and the mechanism of electrocatalytic systems is much higher. he achievement of a iner time resolution and highly focused beams (of dimensions of less than 20 m) has become possible ater the advent of the 3rd generation synchrotron radiation sources. In the setup of a time-resolved-XAS experiment, the standard monochromator is replaced by a polychromator so that the sample is crossed by a polychromatic beam which is Hindawi Publishing Corporation Journal of Spectroscopy Volume 2014, Article ID 480102, 7 pages http://dx.doi.org/10.1155/2014/480102