Single Cell Performances Based Glass Composite Membrane for Low Temperature H2/O2 Fuel Cells

Membrane electrode assemblies (MEAs) for a low temperature H2/O2 fuel cell were fabricated using glass composite membrane and Pt/C electrode were evaluated by various operating condition. The stability and durability of the cell and polarization characteristics of membrane electrode assembles (MEAs) were reported. Electrochemical performances on MEAs consist of PWA {(12-tungsto(VI) phosphoric acid, n-hydrate)}/P2O5(phosphoric acid)/SiO2 (TEOS, tetraethoxysilane) glass composite membrane electrolyte and Pt/C electrode have been demonstrated representing a major milestone towards developing a viable atmospheric low temperature H2/O2 fuel cell system. MEAs were showed good performances under various functions of the temperature and relative humidity. A maximum current density of 141 mA/cm2 was obtained at 35 °C with 30% relative humidity by using a PWA/P2O5/SiO2 (5/5/90 mol%) glass composite membrane and Pt/C (0.1 mg/cm2) electrode. Polarization curves were recorded and their results support the conclusions obtained from the electrochemical impedance spectroscopy (EIS)

Guest Molecule-Responsive Functional Calcium Phosphonate Frameworks for Tuned Proton Conductivity

We report the synthesis, structural characterization, and functionality of an open-framework hybrid that combines Ca2+ ions and the rigid polyfunctional ligand 5-(dihydroxyphosphoryl) isophthalic acid (PiPhtA). Ca-PiPhtA-I is obtained by slow crystallization at ambient conditions from acidic (pH≈3) aqueous solutions. It possesses a high water content (both Ca coordinated and in the lattice), and importantly, it exhibits water-filled 1D channels. At 75 °C, Ca-PiPhtA-I is partially dehydrated and exhibits a crystalline diffraction pattern that can be indexed in a monoclinic cell with parameters close to the pristine phase. Rietveld refinement was carried out for the sample heated at 75 °C, Ca-PiPhtA-II, using synchrotron powder X-ray diffraction data.All connectivity modes of the “parent” Ca-PiPhtA-I framework are retained in Ca-PiPhtA-II. Upon Ca-PiPhtA-I exposure to ammonia vapors (28% aqueous NH3) a new derivative is obtained (Ca-PiPhtA-NH3) containing 7 NH3 and 16 H2O molecules according to elemental and thermal analyses. Ca-PiPhtA-NH3 exhibits a complex X-ray diffraction pattern with peaks at 15.3 and 13.0 Å that suggest partial breaking and transformation of the parent pillared structure. Although detailed structural identification of Ca-PiPhtA-NH3 was not possible, due in part to nonequilibrium adsorption conditions and the lack of crystallinity, FT-IR spectra and DTA-TG analysis indicate profound structural changes compared to the pristine Ca-PiPhtA-I. At 98% RH and T = 24 °C, proton conductivity, σ, for Ca PiPhtA-I is 5.7 ×10−4 S·cm−1. It increases to 1.3 × 10−3 S·cm−1 upon activation by preheating the sample at 40 °C for 2 h followed by water equilibration at room temperature under controlled conditions. Ca-PiPhtA-NH3 exhibits the highest proton conductivity, 6.6 × 10−3 S·cm−1, measured at 98% RH and T = 24 °C. Ea for proton transfer in the above-mentioned frameworks range between 0.23 and 0.4 eV, typical of a Grothuss mechanism of proton conduction.Proyecto nacional MAT2010-1517

The preparation and characterization of TiO2/ZrO2 composites doped with PMA/PWA

A new class of glass composite membranes of various compositions was prepared via a sol-gel technique. The membranes, consisting of (phophotungsticacid/phosphomolybdicacid) PWA/PMA-P2O5-SiO2 mixed with either ZrO2 or TiO2 displayed varying properties depending on their composition and mode of fabrication. The structure and property of the obtained glass ceramic composite membranes were investigated by FTIR, TG/DTA and textural analysis. The results included good mechanical, textural and thermal properties and the materials were deemed to be suitable electrolytes for fuel cell applications