Electrochemical and spectroscopic characterisations of cation exchange membrane equilibrated in acid and salt solutions: application as separator in microbial fuel cell

Abstract

The polymer cation exchange membrane (Nafion117) was equilibrated garden soil leachate. It was then characterised using the stationary voltamperometry method and the mass transfer electrochemical Hittorf-based method. The results obtained with these two techniques were compared to those obtained with the membrane conditioned only with conventional acid and/or salt electrolytes solutions. These two conditions highlighted the good proton conduction of the membrane, against metal ions. This finding was supported and complemented by impedance spectroscopic studies at both transient and stationary regimes. The parameters studied were electrical impedance and specific conductivity. It was found that at higher frequencies, the conductivity of the membrane conditioned with protons was five times higher than that stored in distilled water. As an application, the membrane was tested successfully in a garden soil microbial fuel cell under study, thereby evidencing its good proton conduction. Nafion exhibits, therefore, a high protonic conductivity when hydrated, because protons can be transported via Grotthus and hopping mechanisms via its functional sites.

Keywords:

• Nafion membrane
• proton
• metal ions
• electrochemical characterisation
• impedance spectroscopy
• microbial fuel cell

Acknowledgement

The authors acknowledge assistance from the technical staff of L.E.P.M-USTO-MB for impedance spectroscopy measurements.