Electrochemical Evaluation of Moisture Dependent Proton Conductivity of a Nickel(II) Complex

A coordination complex of Ni(II) ion was synthesized using an alkaline solution of 1-naphthol and an aqueous solution of nickel sulphate. Quantum chemical calculations were used to study the structure of the synthesized complex. Under 100% relative humidity (RH) the proton conductivity of the complex was studied using electrochemical impedance spectroscopy. The experimental results revealed that the proton conductivity of the complex increased with time and reached a constant value in 48 hours. Upon drying the sample, the complex lost the proton conductivity. On exposing to moisture the proton conductivity increased with time and attained a constant value within 48 hours. Thus, the complex exhibited a reversible moisture dependent proton conductivity. The effect of temperature on the proton conductivity of the synthesized complex was studied and the results revealed that the nickel complex is a good proton conducting solid state electrolyte at the elevated temperatures.