Nanoarchitectonics of fibrous clays as fillers of improved proton-conducting membranes for fuel-cell applications

This work reports on the development of various nanostructured materials based on the assembly of SiO2, TiO2 and ZnO nanoparticles to sepiolite fibers (Sep) and their incorporation as a filler of Nafion to improve their performance as proton exchange membrane for fuel cells applications. Various nanoarchitectures, SiO2-Sep, TiO2-SiO2-Sep and ZnO@SiO2-Sep, were prepared following a colloidal route based on the controlled hydrolysis of alkoxide precursos (tetramethoxysilane and titanium tetraisopropoxide) in the presence of hexadecyltrimethylammonium-sepiolite. The SiO2 and TiO2 nanoparticles were consolidated after a thermal treatment that also removes the surfactant and assures their assembly to the clay. In the case of the ZnO@SiO2-Sep nanostructured material, previously formed ZnO nanoparticles were assembled to the intermediated produced after the hydrolysis-polycondensation of tetramethoxysilane on the organoclay, followed by a thermal treatment that consolidates the nanoarchitecture. The resulting nanoarchitectures were characterized by XRD, FTIR, SEM, TEM and N2 adsorption-desorption isotherms, confirming the formation of the nanoparticles and their assembly through silanol groups at the external surface of the clay. Nafion-based composite membranes were prepared using as nanofiller the produced SiO2-Sep, TiO2-SiO2-Sep and ZnO@SiO2-Sep nanoarchitectures. Thermal properties, water uptake and proton conductivity of the resulting composite membranes were evaluated in comparison to those of a neat Nafion membrane to ascertain their potential usefulness for applications in PEMFC. [Display omitted] •Preparation of nanoarchitectured materials by assembly of of SiO2, TiO2 and ZnO nanoparticles to sepiolite fibers.•Use of the sepiolite-based nanoarchitectures as nanofiller of Nafion membranes.•Evaluation of proton conductivity of the resulting composite membranes for potential uses in fuel cell applications.•Nanofillers containing two types of nanoparticles assembled to the clay offer better properties.