Electronic semiconducting oxides as pH sensors

Abstract Limitations on the response of electronically-conducting oxides as pH sensors are demonstrated. PtO2, IrO2, RuO2, OsO2, Ta2O5 and TiO2 showed near-Nernstian behavior in the pH range 2–12 in air-saturated solutions. Interferences from selected reducing and oxidizing agents and from some complexing anions were measured and catalogued. No interference from monovalent cations (Group IA) was observed. Several reaction mechanisms are proposed and discussed.