Hybrid Nafion–silica membranes doped with heteropolyacids for application in direct methanol fuel cells

Nafion–silica composite membranes doped with phosphotungstic and silicotungstic acids have been investigated for application in direct methanol fuel cells at high temperature (145°C). The phosphotungstic acid-based membrane showed better electrochemical characteristics at high current densities with respect to both silicotungstic acid-modified membrane and silica–Nafion membrane. A maximum power density of 400 mW cm−2 was obtained at 145°C in the presence of oxygen feed, whereas the maximum power density in the presence of air feed was approaching 250 mW cm−2. The results indicate that the addition of inorganic hygroscopic materials to recast Nafion extends the operating range of a direct methanol fuel cell. Operation at high temperatures significantly enhances the kinetics of methanol oxidation.