Electrodeposited iridium oxide as studied by tip/substrate steady state voltammetry Alessandro Minguzzi, Cristina Locatelli, Alberto Vertova, Sandra Rondinini Dipartimento di Chimica Fisica ed Elettrochimica, Università degli Studi di Milano, via Golgi 19, 20133, Milan, Italy XXX@unimi.it Iridium oxide is well known for its wide field of applications that range from electrocatalysis to electroanalysis, from electrochromism to neural stimulation. In this work, the properties of electrodeposited iridium oxide films (EIROFs) have been studied by scanning electrochemical microscopy (SECM) in the feedback mode by means of the so-called tip/substrate (T/S) voltammetry under steady state conditions. This SECM mode was intensively used in the past for the study of conducting polymers, as in reference [1]. The main purpose is the study of the reversible solid state-redox transitions that occur over iridium oxide in the potential range around 0.4 -1.4 V (RHE) and that are at the basis of all its applications. The transitions are observed and studied by combining (i) the use of suitable reversible redox couples and (ii) the effect of selecting different solution pHs for “shifting” the potential of the redox transitions themselves. In fact, the latter are pH dependent as evident from the common equation: IrOx(OH)y + H+(solution) + e(oxide) = IrOx-(OH)y+ (1) Moreover, being EIROFs highly hydrated films, protons are free to move in the whole electrode mass. In particular conditions, the transition includes a conversion semiconductor/conductor (like in the Ir(III)/Ir(IV) transition), that has a remarkable effect on the feedback current. The possible individuation of electrogenerated iridium species of different valencies via their reaction with one form of the redox couple, by analogy with a recent publication [2] on oxidized Pt, is also discussed. [1] Lee, C.; Bard, A.J. Anal. Chem. 1990, 62, 1906 [2] Rodriguez Lopez, J.; Minguzzi, A.; Bard, A.J. J. Phys. Chem. C. 2010, 114, 18645 Acknowledgements: The financial contributions of PRIN 2008 – “Pt-free electrocatalysts for direct alcohol fuel cells.” 2008N7CYL5 and PUR-Università degli Studi di Milano (2009 – 2010) funds are gratefully acknowledged.

Electrodeposited iridium oxide as studied by tip/substrate steady state voltammetry / A. Minguzzi, C. Locatelli, A. Vertova, S. Rondinini. ((Intervento presentato al 24. convegno Congresso Nazionale della Società Chimica Italiana tenutosi a Lecce nel 2011.

Electrodeposited iridium oxide as studied by tip/substrate steady state voltammetry

A. Minguzzi;C. Locatelli;A. Vertova;S. Rondinini
2011

Abstract

Electrodeposited iridium oxide as studied by tip/substrate steady state voltammetry Alessandro Minguzzi, Cristina Locatelli, Alberto Vertova, Sandra Rondinini Dipartimento di Chimica Fisica ed Elettrochimica, Università degli Studi di Milano, via Golgi 19, 20133, Milan, Italy XXX@unimi.it Iridium oxide is well known for its wide field of applications that range from electrocatalysis to electroanalysis, from electrochromism to neural stimulation. In this work, the properties of electrodeposited iridium oxide films (EIROFs) have been studied by scanning electrochemical microscopy (SECM) in the feedback mode by means of the so-called tip/substrate (T/S) voltammetry under steady state conditions. This SECM mode was intensively used in the past for the study of conducting polymers, as in reference [1]. The main purpose is the study of the reversible solid state-redox transitions that occur over iridium oxide in the potential range around 0.4 -1.4 V (RHE) and that are at the basis of all its applications. The transitions are observed and studied by combining (i) the use of suitable reversible redox couples and (ii) the effect of selecting different solution pHs for “shifting” the potential of the redox transitions themselves. In fact, the latter are pH dependent as evident from the common equation: IrOx(OH)y + H+(solution) + e(oxide) = IrOx-(OH)y+ (1) Moreover, being EIROFs highly hydrated films, protons are free to move in the whole electrode mass. In particular conditions, the transition includes a conversion semiconductor/conductor (like in the Ir(III)/Ir(IV) transition), that has a remarkable effect on the feedback current. The possible individuation of electrogenerated iridium species of different valencies via their reaction with one form of the redox couple, by analogy with a recent publication [2] on oxidized Pt, is also discussed. [1] Lee, C.; Bard, A.J. Anal. Chem. 1990, 62, 1906 [2] Rodriguez Lopez, J.; Minguzzi, A.; Bard, A.J. J. Phys. Chem. C. 2010, 114, 18645 Acknowledgements: The financial contributions of PRIN 2008 – “Pt-free electrocatalysts for direct alcohol fuel cells.” 2008N7CYL5 and PUR-Università degli Studi di Milano (2009 – 2010) funds are gratefully acknowledged.
Settore CHIM/02 - Chimica Fisica
Società Chimica Italiana
Electrodeposited iridium oxide as studied by tip/substrate steady state voltammetry / A. Minguzzi, C. Locatelli, A. Vertova, S. Rondinini. ((Intervento presentato al 24. convegno Congresso Nazionale della Società Chimica Italiana tenutosi a Lecce nel 2011.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/208687
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