To prove the feasibility that nano-scale porous membrane can replace ion exchange membrane used for vanadium redox flow battery(VRB)

mass transfer of hydrated-ion in electrolyte solution through a limited space formed by PVDF nano-porous proton conductive membranes was studied.On a self-designed ion diffusion cell

NaCl and water permeation processes were measured under given concentration and hydrodynamic gradient

as well as osmotic pressure.The results obtained can be applied to correlate mass transport behaviors with membrane morphology.The results show that the behavior of ion diffusion through nano-scale limited space is similar to that in a bulk electrolyte solution; apparent diffusion coefficients are independent of ion concentration.In contrast

apparent diffusion coefficients of ion permeation through ion exchange membrane obviously increase with concentration gradient.For a given osmotic pressure

PVDF nano-porous proton conductive membranes have smaller water permeation rate than that of Nafion 117

and negative influence is also much smaller.Self-made PVDF proton conductive membrane can effectively reject VO2+

providing selectivity over 300 for H+/VO2+ electrolyte at ambient temperature

which means that it is possible to replace ion exchange membrane in flow battery application.