Determining the proton diffusion coefficient in highly hydrated iridium oxide films by energy dispersive X-ray absorption spectroscopy

• DOI: 10.1016/j.electacta.2023.142017
• Publication Date: 2023-02-07T01:31:32Z
• Authors: Elisabetta Achilli; Simone Minelli; Irene Casale; Xiufang He; Giovanni Agostini; Giorgio Spinolo; Paolo Ghigna; Alessandro Minguzzi; Alberto Vertova
• Keywords: Oxygen evolution reaction; Electrochemical impedance spectroscopy; Warburg element; EIROF; 02 engineering and technology; 0210 nano-technology; 530; 543

Charge transfer reactions in electrodeposited iridium oxide films (EIROF) are investigated by means of operando energy dispersive X-ray absorption spectroscopy (EDXAS), where oxidation and reduction conditions are selected to drive the Ir(III)/Ir(IV) and Ir(IV)/Ir(V) reactions in acidic solutions. The Ir(III)/Ir(IV) couple is related to a well-known electrochromic phenomenon, while the Ir(IV)/Ir(V) couple might play an important role in the catalysis of the oxygen evolution reactions (OER). In the experiments, current intensity and time-resolved X-ray absorption spectroscopy (XAS) are simultaneously recorded upon application of appropriate potential steps, leading to the independent determination of both the relevant reaction rates and the rate-determining steps. This is allowed by the fast acquisition time (~10