Performance of IrO<sub>x</sub> pH Sensor Prepared by Electrochemical and Thermal Oxidation
Xinyu Liu, Yunxia Pei, Yuanxia Wang, Xiangju Liu, Xuwei Chen, Congtao Sun, Nazhen Liu
Abstract
In this work, the morphology, chemical constitution, and pH sensing performance of IrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> electrode prepared by cyclic voltammetry (hydrous) and thermal oxidation (anhydrous) are investigated. The results suggest that, IrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> film prepared by the electrochemical method consists of Ir(III) and Ir(IV). A hydration treatment of 30 days is required to establish a super-Nernstian response to pH (67 mV/pH). IrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> film prepared by thermal oxidation has a stronger adhesion with the substrate and consists of Ir(III), Ir(IV) and Ir(VI). A more thorough hydration of 60 days is required to establish a Nernstian response to pH (59 mV/pH). The pH sensing mechanism of both electrodes is discussed and their respective application field is recommended.