Positron annihilation lifetime (PAL), AC conductivity, and impedance spectroscopy have been applied for the investigation of polyvinyl alcohol (PVA) doped with different concentrations of NaI in the range from zero to 25 wt%. Wide‐angle x‐ray diffraction measurements reveal that the addition of NaI to the PVA structure leads to a decrease in the crystallinity of the sample. The free volume size obtained from PAL measurements increases with the increase of the NaI concentration on PVA. NaI acts as an inhibitor of positronium formation on the doped polymer with inhibition constant of 0.028 (Mol%)−1. The ionic conductivity of the investigated sample was found to be correlated with the free volume size, which indicates the major role of free volume in the conduction mechanism. The AC conductivity of the prepared samples is measured at room temperature in the frequency range from 50 Hz to 5 MHz. The calculated values of frequency exponent s indicate the hopping mechanism in ionic conductivity. Impedance spectroscopy of PVA doped with different concentrations of NaI was studied. The appeared semi‐circle, in the Nyquist plot, denotes the bulk influence of PVA with different concentrations of NaI. This has been attributed to the parallel connection of bulk resistance and bulk capacitance. Also, the semi‐circle radius of Cole‐Cole plots was found to decrease with the increase of the concentration ratio (wt%) of NaI. So, the increase of the conductivity of PVA with the increase of NaI contents has been investigated.

The possibility of developing low-cost commercial grafted and sulfonated Poly(vinylidene fluoride) (PVDF-g-PSSA) membranes as proton exchange membranes for fuel cell applications have been investigated. PVDF-g-PSSA membranes were systematically prepared and examined with the focus of understanding how the polymer microstructure (degree of grafting and sulfonation, ion-exchange capacity, etc) affects their methanol permeability, water uptake, and proton conductivity. Fourier transform infrared spectroscopy was used to characterize the changes of the membrane's microstructure after grafting and sulfonation. The results showed that the PVDF-g-PSSA membranes exhibited good thermal stability and lower methanol permeability.The proton conductivity of PVDF-g-PSSA membranes was also measured by the electrochemical impedance spectroscopy method. It was found that the proton conductivity of PVDF-g-PSSA membranes depends on the degree of sulfonation. All the sulfonated membranes show high proton conductivity at 92°C, in the range of 27 to 235 mScm, which is much higher than that of Nafion212 (102 mScm −1 at 80°C). The results indicated that the PVDF-g-PSSA membranesare particularly promising membranes to be used as polymer electrolyte membranes due to their excellent stability, low methanol permeability, and high proton conductivity. has high stability and good proton conductivity in low temperatures and high relative-humidity conditions. However, the Nafion-based PEM is expensive, and its conductivity showed reduction at higher temperatures (>80°C) and low humidity (<40%) conditions. A lot of studies have been performed with the goal of developing alternative membranes, focusing on the reduction of the methanol permeability. Some of them have worked on developing new synthetic polymeric membranes that have ionic clusters, [14][15][16][17] or the modification of the Nafion membranes by surface treatment or by blending them with other

Fuel cell has two essential problems, its cost and the durability, which hinder its commercialization. Platinum is the ideal catalyst that has high activity, stability and selectivity but has high cost. An attempt has been done to find a cheaper catalyst instead of platinum. Zinc oxide nanoparticles were synthesized via sol-gel method using zinc acetate and citric acid in basic media with different calcination temperatures (420, 520 and 620 °C). From X-ray diffraction (XRD) patterns, the calculated particles size is 7.7, 15.6 and 19.3 nm as the calcination temperature of 420, 520 and 620°C, respectively, indicating that the particles size increases with increasing the calcination temperature. Different concentrations (5 and 10 wt.%) of ZnO nanoparticles with 10 wt.% polyvinyl alcohol (PVA) were prepared and calcinated at 750 °C to get carbon/ZnO as a catalyst for fuel cell applications. A carbon core-shell surrounding by mono-disperse ZnO nanoparticles with large surface area that required for the new catalyst with believable morphology was shown by transmission electron microscope (TEM). Also, XRD presents high purity of the new composite with uniformly distinguishable peaks. Fourier transformation infrared (FTIR) spectroscopy shows the change in the carbon/ZnO nanoparticles spectra due to ZnO characteristic vibration band at 440-460 cm−1. Cyclic voltammetry (CV) exhibits a good promising catalytic activity and current density with oxidation behaviour is reported. Finally, ZnO used to enhance carbon electrochemically performance as a result of a novel non-precious catalyst.