Conductometric titration as a technique to determine variation in conductivity in perfluorosulfonic acid materials for fuel cells and electrolyzers

One important requirement for a polymeric material to be used as a membrane in fuel cells or water electrolyzers is its high ionic conductivity. In this research work the redeveloped conductometric titration was used to determine conductivity variation with the objective to improve the precision of the determination and reduce the time of operation. Results obtained by changing the experimental conditions of the techniques: reaction rate and conductometric titration, which are two related techniques, are presented. The reaction rate allows to know the chemical kinetics of the neutralization reaction between Nafion®117 membrane and a solution of sodium or potassium hydroxide, the order or pseudo-order reaction and the half-life period. This last parameter is used to carry out the conductometric titration which permits to determine the total acid capacity of this type of polymeric materials. The experimental conditions studied are: type and time of agitation and working temperature control. Good results were obtained in the techniques where the nitrogen bubble stirring was applied, throughout the determination. This procedure ensures a liquid medium with properties near isotropy, suitable for this analysis. The temperature controlled by a thermostat allows isolating the system of temperature variations and permits to compare the results between determinations. Time reduction was ~48 times lower, if 24 h is considered necessary to reach reaction equilibrium.