For application of Vanadium Redox Flow Battery (VRFB), the proton conductivity and vanadium permeability of organic-inorganic (sulfonated poly (phenylene oxide) (sPPO)-nano sized sulfonated silica (sSiO₂)) hybrid membrane were analysed. Fourier Transform Infrared Spectroscopy (FT-IR) results proved the attachment of sulfonic acid (-SO₃H) functional group in PPO polymer and SiO₂. Compared with a typical organic sPPO membrane, the hybrid composite membrane (sPPO-2% sSiO₂) shows an increased Water Uptake (WU), Ion Exchange Capacity (IEC), proton conductivity (IC) and thermal stability. The IC of sPPO and hybrid membranes are 0.050 and 0.077 S/cm, respectively. Compared to sPPO alone, the higher amount of hydrophilic functional group (-SO₃H) existed in the hybrid membrane which is main reason for enhance the IC and WU. During VRFB unit cell operation, The measured Vanadium ion crossover is 14.66, 1.955 and 0.173 mmol/L for Nafion 212, sPPO and hybrid membranes, respectively and VO²⁺ permeability is 2.22 x 10^-7, 2.50 x 10^-8 and 4.76 x 10^-9 cm²/min for Nafion 212, sPPO and hybrid membrane, respectively. The VO²⁺ permeability in hybrid membrane is significantly lowered than Nafion 212 and sPPO membranes. Inorganic nano particles acted as a barrier for vanadium ion crossover in the hybrid polymer membrane. The low cost of hybrid membranes can be efficiently considered as an alternative membrane material for advanced VRFB systems.

Key Words : Vanadium Redox Flow Battery, Hybrid membrane, Poly(phenylene oxide), Sulfonated silica, Vanadium permeability.