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A new series of polymer composite membranes was fabricated using a linear sulfonated poly(ether ether ketone) (SPEEK) polymer with zinc cobalt oxide (ZCO) as an inorganic filler and evaluated for fuel cell applications. SPEEK was obtained by the direct sulfonation of PEEK using concentrated sulfuric acid, and appropriate quantities of ZCO were loaded into it to yield the polymer composites. Proton nuclear magnetic resonance studies revealed the degree of sulfonation of SPEEK to be 55%, while morphological studies confirmed the successful incorporation of inorganic fillers into the polymer matrix. To evaluate the suitability of the prepared composite membranes for fuel cell applications, their physicochemical properties were studied in detail. The pristine SPEEK membrane exhibited a proton conductivity of 0.009 S cm−1 at 30°C, whereas the values for the composite membranes loaded with 2.5 to 10 wt% of ZCO were in the range 0.012–0.020 S cm−1. Moreover, the composite membranes showed excellent thermal stability up to 370°C. Indeed, the membranes obtained by the incorporation of ZCO into the SPEEK polymer show potential for fuel cell applications.

The design and development of proton conducting polymer electrolyte membranes from a linear constituent, sulfonated poly (ether ether ketone) (SPEEK), and inorganic additive, niobium oxide (NBO), have been achieved. The degree of sulfonation of SPEEK was measured by back titration method and found to be 57%. The physicochemical properties such as water uptake ability, ion-exchange capacity, swelling ratio, proton conductivity, and thermal stability of the prepared polymer nanocomposite membranes were studied in detail. The distribution of NBO throughout the polymer matrix has been examined by scanning electron microscopic and X-ray diffraction analyses and found to be uniform. The SP-NBO-10 composite membrane shows 38.4% of water uptake, whereas the pristine membrane limits to 27.1%. The prepared electrolyte membranes exhibit good proton conductivity at temperature varying from 30°C to 90°C and possess less activation energy for the transportation of proton by the incorporation of NBO filler. The thermal studies demonstrated that the stability of the composite membranes was significantly enhanced by the impregnation of NBO. The filler NBO shows excellent improvements on the polymer nanocomposite, making it a very promising additive for other polymers and offers new roads for energy applications.

Flexible organic–inorganic polymer nanocomposite membranes with uniformly distributed metal oxide nanoparticles were prepared using sulfonated poly(ether ether ketone) (SPEEK) as a base material and praseodymium oxide (PSO) as an inorganic additive. The degree of sulfonation of SPEEK was determined by proton nuclear magnetic resonance (NMR) analysis and found to be 60%. The characteristic properties of the polymer nanocomposite membranes were examined by thermogravimetric analysis, X-ray diffraction, ion exchange capacity, water uptake ability, and proton conductivity. The incorporation of metal oxide into the polymer matrix was confirmed by scanning electron microscope with energy dispersive X-ray spectroscopy and X-ray diffraction analyses. The nanocomposite membrane exhibits good thermal stability when compared to that of the pristine membrane and SPEEK with 10 wt% of PSO loading was found to be stable up to 450°C. The assessment of polymer electrolyte membrane is accomplished by fabricating membrane electrode assemblies of pure SPEEK and SP-PSO-10 membranes and the latter produced maximum peak power density of 622 mW cm−2. The constructed SPEEK/PSO nanocomposite membranes offered superior physicochemical properties while applying these materials in an H2-O2 fuel cell.

A new reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed for the separation and identification of impurities present in metadoxine. Herein, we report that one of the impurities eluted from the metadoxine sample is 4-deoxypyridoxine hydrochloride (4-DPH). In HPLC analysis, the retention time (RT) of 4-DPH was observed to be at 13.5 min in both the reference and metadoxine samples and the relative retention time (RRT) was 1.71. The presence of 4-DPH in a metadoxine sample was also confirmed by a chromatogram obtained by spiking the 4-DPH standard into the sample. Furthermore, the elution and mass of impurity 4-DPH in metadoxine was proven by LC-mass spectroscopy studies. This method highlights the presence of another unknown impurity that has so far not been observed in earlier methods of metadoxine evaluation. Hence, the developed method achieved superior resolution between metadoxine and impurities and thereby facilitates the production of a purer metadoxine drug.

A series of phenolphthalein-based sulfonated poly(ether ether sulfone) (SPEES) membranes were synthesized by aromatic nucleophilic polymerization reaction. The degree of sulfonation was controlled by direct synthesis of sulfonated polymer, which leads to high thermal stability. The physicochemical properties of the SPEES membranes were studied in order to evaluate the suitability of these membranes in fuel cell applications. The ion-exchange capacity of the synthesized SPEES membranes was found in the range between 2.19 mequiv. g−1 and 2.35 mequiv. g−1. The morphology of the membranes was investigated with high-resolution scanning electron microscopy and confirmed the presence of hydrophilic domains that impart good proton conductivity. The membrane electrode assembly of SPEES-30 and SPEES-50 membranes has been successfully fabricated, where SPEES-50 produced a maximum peak power density of 643 mW cm−2 while applying in hydrogen–oxygen fuel cell.

A new class of polymer electrolyte membranes containing an azo based ionic diol (30, 40 and 50 mol%) was prepared for use in a fuel cell. Its proton conductivity, hydrolytic stability, water uptake capacity, swelling behaviour and ion-exchange capacity measurement data indicated its suitability for use as a proton exchange electrolyte membrane in fuel cells. For example, the membranes containing 30, 40 and 50 mol% of azo based ionic monomers exhibit fairly good proton conductivities of 0.073 S cm−1, 0.075 S cm−1 and 0.079 S cm−1, respectively at 30 °C. Moreover, the prepared membranes show a phase separated morphology and exhibit a high thermal stability up to 460 °C which are important parameters for successful fuel cell design. Two types of azo based sulfonated poly(arylene ether sulfone) (SPAES) such as the SPAES-30 and SPAES-50 membrane electrode assembly have been successfully fabricated and yielded a good fuel cell performance in the whole range of current density.