Electrochemical impedance spectroscopy study of Ta2O5 based EIOS pH sensors in acid environment

To develop an on-line pH sensor for acidic environment application, a tantalum pentoxide (Ta2O5) based electrolyte-ion sensitive membrane-oxide-semiconductor (EIOS) pH sensor has been prepared and investigated by applying electrochemical impedance spectroscopy (EIS) and capacitance-voltage method (C-V). Nernstian behavior toward variable proton concentrations (∼56.19 mV/pH) in the pH range from 1 to 10 could be achieved. Atomic force microscopic (AFM) showed that the surface of the H+ sensitive Ta2O5 film was uniform and smooth. Electrochemical impedance spectroscopy (EIS) revealed that the space charge capacitance easily distinguish pH changes. Possible interference from Cu2+, Fe2+ and Fe3+ were studied in pH 2.2 solutions.