Performance of IrOx pH Sensor Prepared by Electrochemical and Thermal Oxidation

In this work, the morphology, chemical constitution, and pH sensing performance of IrO _x electrode prepared by cyclic voltammetry (hydrous) and thermal oxidation (anhydrous) are investigated. The results suggest that, IrO _x 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 _x 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.