Hydrophilic and mesoporous SiO2–TiO2–SO3H system for fuel cell membrane applications

Hydrophilic and mesoporous sulfonated SiO2–TiO2–SO3H systems as new additives for fuel cell electrolyte membranes are directly synthesized by the binary sol–gel reaction of TEOS–TiCl4 and consecutive sulfonation with a hydrophilic generator, dihydroxy-m-benzenedisulfonic acid disodium salt. The sulfonation approach makes use of the simple chelating chemistry between the catecholic groups (dihydroxy benzene) and surface Ti ions of the inorganic ordered mesoporous SBA-15 structure. The system is successfully employed in fuel cell membrane applications with a composite Nafion membrane mixed with a mesoporous hydrophilic resin additive, and reveals an obvious enhancement of the proton conductivity at low humidity and elevated temperatures. This improvement was attributed to the excellent water retention capability of the hydrophilic mesoporous resin.

Graphical abstractThe composite films containing SiO2–TiO2–SO3H resin additives, with strong water retention capabilities, showed superior proton conductivity, even at 120 °C and 25% RH, as well as a slightly improved current density at 30% RH and 70 °C, when compared to costly Nafion film.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► The hydrophilic and mesoporous SiO2–TiO2–SO3H resins have a potential to be used as alternative membrane source materials in PEFCs. ► The sulfonation for hydrophilicity is conducted via simple chelating chemistry between catecholic groups and surface Ti ions. ► The proton conductivity of SiO2–TiO2–SO3H composite films is superior to the commercial Nafion film.