Proton exchange membranes for application in fuel cells: grafted silica/SPEEK nanocomposite elaboration and characterization

A Deep Insight into Different Acidic Additives as Doping Agents for Enhancing Proton Conductivity on Polybenzimidazole Membranes

The use of phosphoric acid doped polybenzimidazole (PBI) membranes for fuel cell applications has been extensively studied in the past decades. In this article, we present a systematic study of the physicochemical properties and proton conductivity of PBI membranes doped with the commonly used phosphoric acid at different concentrations (0.1, 1, and 14 M), and with other alternative acids such as phytic acid (0.075 M) and phosphotungstic acid (HPW, 0.1 M). The use of these three acids was reflected in the formation of channels in the polymeric network as observed by cross-section SEM images. The acid doping enhanced proton conductivity of PBI membranes and, after doping, these conducting materials maintained their mechanical properties and thermal stability for their application as proton exchange membrane fuel cells, capable of operating at intermediate or high temperatures. Under doping with similar acidic concentrations, membranes with phytic acid displayed a superior conducting behavior when compared to doping with phosphoric acid or phosphotungstic acid.

New series of organic–inorganic polymer nanocomposite membranes for fuel cell 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.

Nanocomposite Based on Functionalized Gold Nanoparticles and Sulfonated Poly(ether ether ketone) Membranes: Synthesis and Characterization

Gold nanoparticles, capped by 3-mercapto propane sulfonate (Au-3MPS), were synthesized inside a swollen sulfonated poly(ether ether ketone) membrane (sPEEK). The formation of the Au-3MPS nanoparticles in the swollen sPEEK membrane was observed by spectroscopic and microscopic techniques. The nanocomposite containing the gold nanoparticles grown in the sPEEK membrane, showed the plasmon resonance λ_max at about 520 nm, which remained stable over a testing period of three months. The size distribution of the nanoparticles was assessed, and the sPEEK membrane roughness, both before and after the synthesis of nanoparticles, was studied by AFM. The XPS measurements confirm Au-3MPS formation in the sPEEK membrane. Moreover, AFM experiments recorded in fluid allowed the production of images of the Au-3MPS@sPEEK composite in water at different pH levels, achieving a better understanding of the membrane behavior in a water environment; the dynamic hydration process of the Au-3MPS@sPEEK membrane was investigated. These preliminary results suggest that the newly developed nanocomposite membranes could be promising materials for fuel cell applications.

Mixed matrix membranes based on silica nanoparticles and microcellular polymers for CO2/CH4 separation

Mixed matrix membranes made from silica nanoparticles and microcellular polymers were prepared from Matrimid® 5218 combined with tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane via the sol–gel method. The nanoparticles were prepared in situ during membrane casting yielding a homogeneous distribution inside a foamed polyimide structure. Mixed matrix membranes with SiO2 contents up to 16% wt. were treated at 60℃, 100℃, 150℃, and 200℃. Thermal gravimetric analysis and Fourier transform infrared spectroscopy analyses were performed providing information on chemical composition and thermal stability, while the porous structure (average cell diameter and cell density) was studied by scanning electron micrograph. Also, dynamic mechanical analysis was used to determine the glass transition temperature (Tg) and elastic modulus. Finally, the gas transport properties were studied in terms of treatment temperature, feed pressure, SiO2 loading, and testing temperature. CO2 permeability was found to increase by a factor of 3–4 at 3% SiO2 content using tetraethoxysilane in Matrimid, while ideal selectivity for CO2/CH4 separation was constant. Finally, the plasticization effect was practically eliminated by the introduction of SiO2 nanoparticles.

Amino-functionalized mesoporous silica based polyethersulfone–polyvinylpyrrolidone composite membranes for elevated temperature proton exchange membrane fuel cells

It is important to find alternative membranes to the state-of-the-art polybenzimidazole based high temperature proton exchange membranes with high proton conductivity at elevated temperature but with simple synthesis procedures.

Microstructure and properties of novel SPEEK/PVDF-g-PSSA blends for proton exchange membrane with improved compatibility

Design and fabrication of a novel series of high performance SPEEK/PVDF-g-PSSA blend membranes with improved compatibility via grafting method.