Polybenzimidazole-Graft-Polyvinylphosphonic Acid—Proton Conducting Fuel Cell Membranes

A new method for the preparation of polybenzimidazole (PBI)-based membranes, containing high concentrations of immobilized phosphonic acid groups, has been developed. The procedure used is carried out in two steps: (1) Synthesis of modified PBIs, containing 1,2-dihydroxypropyl groups and preparation of films there from; (2) Introduction of vinylphosphonic acid (VPA) and initiator (cerium ammonium nitrate) in the film, subsequent grafting of VPA from the active sites of the PBI backbone. Membranes with different length of the grafted polyvinylphosphonic acid chains were prepared. The molar ratio grafted VPA units per PBI repeating unit reaches 7.8. Proton conductivity was measured at 120C and relative humidity (RH) 20–100%. For the membrane with highest concentration of phosphonic acid groups the proton conductivity was 35 mS cm1 at 100% RH and 8 mS cm1 at 20% RH.JRC.F.2-Cleaner energ

Overpotential analysis of alkaline and acidic alcohol electrolysers and optimized membrane-electrode assemblies

Alcohol electrolysis using polymeric membrane electrolytes is a promising route for storing excess renewable energy in hydrogen, alternative to the thermodynamically limited water electrolysis. By properly choosing the ionic agent (i.e. H+ or OH) and the catalyst support, and by tuning the catalyst structure, we developed membrane-electrode-assemblies which are suitable for cost-effective and efficient alcohol electrolysis. Novel porous electrodes were prepared by Atomic Layer Deposition (ALD) of Pt on a TiO2-Ti web of microfibers and were interfaced to polymeric membranes with either H+ or OH conductivity. Our results suggest that alcohol electrolysis is more efficient using OH conducting membranes under appropriate operation conditions (high pH in anolyte solution). ALD enables better catalyst utilization while it appears that the TiO2-Ti substrate is an ideal alternative to the conventional carbon-based diffusion layers, due to its open structure. Overall, by using our developmental anodes instead of commercial porous electrodes, the performance of the alcohol electrolyser (normalized per mass of Pt) can be increased up to ~30 times

Overpotential analysis of alkaline and acidic alcohol electrolysers and optimized membrane-electrode assemblies

Alcohol electrolysis using polymeric membrane electrolytes is a promising route for storing excess renewable energy in hydrogen, alternative to the thermodynamically limited water electrolysis. By properly choosing the ionic agent (i.e. H+ or OH) and the catalyst support, and by tuning the catalyst structure, we developed membrane-electrode-assemblies which are suitable for cost-effective and efficient alcohol electrolysis. Novel porous electrodes were prepared by Atomic Layer Deposition (ALD) of Pt on a TiO2-Ti web of microfibers and were interfaced to polymeric membranes with either H+ or OH conductivity. Our results suggest that alcohol electrolysis is more efficient using OH conducting membranes under appropriate operation conditions (high pH in anolyte solution). ALD enables better catalyst utilization while it appears that the TiO2-Ti substrate is an ideal alternative to the conventional carbon-based diffusion layers, due to its open structure. Overall, by using our developmental anodes instead of commercial porous electrodes, the performance of the alcohol electrolyser (normalized per mass of Pt) can be increased up to ~30 times

Overpotential analysis of alkaline and acidic alcohol electrolysers and optimized membrane-electrode assemblies

Alcohol electrolysis using polymeric membrane electrolytes is a promising route for storing excess renewable energy in hydrogen, alternative to the thermodynamically limited water electrolysis. By properly choosing the ionic agent (i.e. H+ or OH) and the catalyst support, and by tuning the catalyst structure, we developed membrane-electrode-assemblies which are suitable for cost-effective and efficient alcohol electrolysis. Novel porous electrodes were prepared by Atomic Layer Deposition (ALD) of Pt on a TiO2-Ti web of microfibers and were interfaced to polymeric membranes with either H+ or OH conductivity. Our results suggest that alcohol electrolysis is more efficient using OH conducting membranes under appropriate operation conditions (high pH in anolyte solution). ALD enables better catalyst utilization while it appears that the TiO2-Ti substrate is an ideal alternative to the conventional carbon-based diffusion layers, due to its open structure. Overall, by using our developmental anodes instead of commercial porous electrodes, the performance of the alcohol electrolyser (normalized per mass of Pt) can be increased up to ~30 times

Nonisothermal melt-crystallization behavior of calcium phosphate/poly(3- hydroxybutyrate-co-3-hydroxyvalerate) nanocomposite microspheres

Microspheres consisting of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) polymer matrix and calcium phosphate (Ca-P) nanoparticles were made using the solid-in-oil-in-water (S/O/W) emulsion solvent evaporation technique. Amorphous Ca-P nanoparticles with the calcium to phosphate ratio of 1.5 were relatively well distributed in microspheres. The nonisothermal crystallization behavior of Ca-P/PHBV nanocomposite with different Ca-P contents (0-20%) was studied through differential scanning calorimetry using different cooling rates. During nonisothermal crystallization, the presence of Ca-P nanoparticles resulted in an increase in crystallization rate and the nucleation activity of the nanocomposite also increased with increasing Ca-P content. Various models were applied to investigate nonisothermal crystallization kinetics. All approaches, except for the Ozawa model, could successfully describe the nonisothermal crystallization behavior of PHBV and Ca-P/PHBV nanocomposite. The effective activation energy for nonisothermal crystallization was calculated using the differential isoconversional method proposed by Friedman. The morphology of PHBV spherulites in nanocomposite was also studied using polarized optical microscopy. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers.link_to_subscribed_fulltex