Measurement of hydrogen ion conductivity through proton exchange membrane
Proton exchange membrane is the prime part of proton exchange membrane fuel cell (PEMFC). In this work, it has focused to the proton conduction through two different conductive polymer membranes such as Nafion 212 and Fumapem AM (PBI). The conductivity has measured by the two probe method with the help of electrochemical impedance spectroscopic (EIS) analysis. To increase the conductivity, Fumapem AM (PBI) membrane has been doped with 85 % concentrated H3PO4 acid at ambient temperature. Due to acid doping, it has swelled 41 % compare to prior on. The highest conductivity has recorded as 3.54 and 2.24 mS/cm under 60 °C temperature for Nafion 212 and Fumapem AM (PBI) respectively. The proton conductivity of both membranes is fully dependent on the surrounding temperature.
Polymer Electrolyte Fuel Cell Degradation Mechanisms and Their Diagnosis by Frequency Response Analysis Methods: A Review
Several experimental techniques involving dynamic electrical variables are used to study the complex behaviour of polymer electrolyte membrane fuel cells in order to improve performance and durability. Among them, electrochemical impedance spectroscopy (EIS) is one of the most employed methods. Like any frequency response analysis (FRA) methodology, EIS enables one to separate the contribution of many processes to performance losses. However, it fails to identify processes with a similar time constant and the interpretation of EIS spectra is often ambiguous. In the last decade, alternative FRA methodologies based on non-electrical inputs and/or outputs have been developed. These studies were mainly driven by requirements for a better diagnosis of polymer electrolyte membrane fuel cells (PEMFCs) faulty operation conditions as well as better component and material design. In this contribution, a state-of-the-art EIS and novel FRA techniques for PEMFC diagnosis are summarised. First, common degradation mechanisms and their causes are discussed. A mathematical framework based on linear system theory of time invariant systems is described in order to explain the theoretical implications of the use of different input/output configurations. In relation to this, the concepts and potential are depicted as well as the problematic aspects and future prospective of these diagnostic approaches.
Soluble sulfonated naphthalenic polyimides as materials for proton exchange membranes
Series of sequenced sulfonated naphthalenic polyimides with improved solubility were prepared by polycondensation in m-cresol using aromatic diamines containing phenylether bonds and/or bulky groups. Sulfonated polyimides were characterized by NMR and IR spectroscopies. Membranes were prepared by solution casting method and characterized by determining the ion-exchange capacity, water swelling, proton conductivity whereas the morphology of polymer membranes was studied by small angle neutron scattering.