Proton-conducting Organic-inorganic Sulfo-containing Membranes for Fuel Cell

Cross-linked organiс-inorganic sulfo-containing membranes of various compositions based on acrylic monomers (acrylonitrile, acrylic acid, 3-sulfopropylacrylate potassium salt, ethylene glycol diacrylate) and sol-gel systems of tetraethoxysilane have been developed. Synthesis of the polymer matrix was carried out by UV-initiated polymerization of the monomer mixture and the inorganic component was formed in situ while conducting the sol-gel process of the precursor. FTIR, SEM, EDS, DMA, impedance spectroscopy were used to characterize the synthesized materials. The influence of inorganic component content on the properties of the membranes was investigated. DMA results show that an increase in silica content leads to a decrease in packing density and an increase in structural heterogeneity in sulfo-containing polyacrylate/silica membranes. The highest values of proton conductivity 1.12 ꞏ 10−2 Sm/cm at 60 °C were found in membranes containing 3 wt.%. of the added sol-gel system. Further increase of silica content does not increase the proton conductivity of the membranes. The proton transfer activation energies in the membranes were calculated from the temperature dependence of proton conductivity. The obtained cross-linked sulfo-containing organic-inorganic materials can be used for the development of proton-conducting membranes for fuel cells.

Membrane pervaporation performance applied for brackish water prepared by vacuum impregnation method

Coating method and number of membrane layer are crucial factors on membrane performance. Through a vacuum impregnation method allows a sol solution uniformly fill into membrane support and it is required only less solution. The aim of this study is to apply vacuum impregnation method through vacuum calcination and air calcination during fabrication of silica membranes and to investigate the effect of layer variations on silica membranes performance to apply for brackish water. The sol solution was made from TEOS as silane precursor, ethanol and dual catalysts (citric acid + ammonia). Alumina membrane support was coated by vacuum impregnation method and calcined the membrane under air and vacuum condition. From the FTIR result, it indicates that silica membranes calcined in air and vacuum calcination have Si-O-Si and Si-OH. The vacuum impregnation obtained smoother surface membranes. The silica membrane calcined via vacuum calcination performs excellent water fluxes and salt rejection of 22.01 kg.m− 2.h−1 and 98.98 %. If compare to silica membranes calcined in air, the water flux (19.11 kg.m− 2.h−1) and salt rejection (98.75 %). It also found the two layers silica membrane is better than three layers for the membrane performance result.

Sol-Gel Processed Cobalt-Doped Methylated Silica Membranes Calcined under N2 Atmosphere: Microstructure and Hydrogen Perm-Selectivity

Methyl-modified, cobalt-doped silica (Co/MSiO2) materials were synthesized by sol-gel technique calcined in N2 atmospheres, and membranes were made thereof by coating method. The effects of Co/Si molar ratio (nCo) on the physical-chemical constructions of Co/MSiO2 materials and microstructures of Co/MSiO2 membranes were systematically investigated. The gas permeance performance and hydrothermal stability of Co/MSiO2 membranes were also tested. The results show that the cobalt element in Co/MSiO2 material calcined at 400 °C exists not only as Si–O–Co bond but also as Co3O4 and CoO crystals. The introduction of metallic cobalt and methyl can enlarge the total pore volume and average pore size of the SiO2 membrane. The activation energy (Ea) values of H2, CO2, and N2 for Co/MSiO2 membranes are less than those for MSiO2 membranes. When operating at a pressure difference of 0.2 MPa and 200 °C compared with MSiO2 membrane, the permeances of H2, CO2, and N2 for Co/MSiO2 membrane with nCo = 0.08 increased by 1.17, 0.70, and 0.83 times, respectively, and the perm-selectivities of H2/CO2 and H2/N2 increased by 27.66% and 18.53%, respectively. After being steamed and thermally regenerated, the change of H2 permeance and H2 perm-selectivities for Co/MSiO2 membrane is much smaller than those for MSiO2 membrane.