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.
Synthesis, water stability and proton conductivity of novel sulfonated polyimides from 4,4′-bis(4-aminophenoxy)biphenyl-3,3′-disulfonic acid
Abstract A novel sulfonated diamine monomer, 4,4′-bis(4-aminophenoxy)biphenyl-3,3′-disulfonic acid (BAPBDS) with the high basisity and flexible structure was synthesized by direct sulfonation of 4,4′-bis(4-aminophenoxy)biphenyl (BAPB). Sulfonated polyimides (SPIs) were prepared from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), BAPBDS and nonsulfonated diamines such as BAPB. The SPI membranes showed much higher water stability at high temperatures than other sulfonated diamine-based SPIs reported so far. Their water vapor sorption isotherm, water uptake (WU), density, dimensional change and proton conductivity σ were investigated. The SPIs showed rather isotropic dimensional changes with WU and the volume increases were slightly smaller than those estimated from the additivity. The SPIs with ion exchange capacities (IECs) of 1.9–2.7 meq/g displayed the similar relationship between σ and WU each other, which was different from those of Nafion 117 and also of the SPIs with the lower IECs. The former SPIs showed reasonably high σ values of 10 −2  S/cm or more even at WU of 25 g/100 g dry polymer under 70% RH at 50 °C, whereas the latter showed the similarly high σ values only in liquid water, but not in the nearly saturated water vapor.
Sulfonated polybenzimidazole membranes — preparation and physico-chemical characterization
Abstract The preparation of sulfonated polybenzimidazole by sulfuric acid treatment on pre-formed polybenzimidazole membranes was investigated. This polymer, which is originally a thermal resistant and insulating material is transformed by the chemical treatment into a proton conductor. The modified material is stable at temperatures close to 400°C. The proton conductivity of the sulfonated membrane at 160°C and 100% r.h. is 7.5×10 −5  S/cm. The low conductivity is explained by protonation of nitrogen in the imidazolium ring, as evidenced by FT-IR analysis, which lowers the proton mobility. Hydrogen bridge bonds are formed between nitrogen in the imidazole and oxygen of sulfonic group creating a more regular structure in the material which becomes insoluble in polar solvent such as dimethyl sulfoxide. These modifications of the material have been observed in the X-ray diffraction patterns, which evidence an incipient crystalline structure of the sulfonated polybenzimidazole.