Water self-diffusion anisotropy and electrical conductivity of perfluorosulfonic acid/SiO2 composite proton exchange membranes

► Water self-diffusion anisotropy in perfluorosulfonic acid (PFSA)/SiO2 composite membranes was investigated. ► The dependence of water diffusivity on diffusion time, temperature and relative humidity was measured. ► The effect of in situ grown sulfonated silica nanoparticles on the orientation of water channels is discussed.