Conductometric Titration to Analyze Nafion^® 117 Conductivity

Nafion^® membrane presents good chemical, thermal and mechanical stability and excellent protonic conductivity when the material is previously well-hydrated. This type of perfluorosulphonic acid membrane is widely used in a great variety of devices, being mainly applied in the field of renewable energy, for fuel cell and electrolyzers of polymeric electrolytes. Focusing on electrolyzers, it is well known that nowadays, they represent the most promising method for the production of hydrogen, being a well-established, robust and easy to use technology. Using Nafion^® membrane in alkaline water electrolyzers as a separator, the aim of this study is to analyze its behaviour under alkaline conditions. Samples of Nafion^® 117 membranes in their original state and samples submitted to a previous cleaning treatment and specific hydration treatment were used. This hydration treatment assured an amount of molecules of water per sulphonic acid group (λ = 17–20). The ionic exchange rate between the hydrogen ion of the sulphonic group of Nafion^® membrane and the sodium and potassium cations present in the alkaline solution were studied. The chemical kinetics of the reaction was determined with the purpose of establishing the time to carry out conductometric titration of the membrane using sodium and potassium hydroxide as titrates. Results show that the exchange rate of the alkaline ions, in the solution, present a first order kinetics reaction, at the concentration of hydroxide ions in that solution.