Amphibious hybrid nanostructured proton exchange membranes

Amphibious proton exchange membranes (PEMs) which could be used under both wet and dry conditions were prepared by sol–gel method in this work. Those novel hybrid PEMs were constructed by three parts: (1) polysiloxane with two basic sites (–NH– on the pendant and N– in the triazole); (2) H3PO4 as the proton source; (3) poly(vinyl alcohol) (PVA) which had good film-forming capacity and ability to anchor the H3PO4 under wet conditions. The resulting hybrid membranes were thermally stabilized up to 200 °C. A matrix-change between polysiloxane and PVA could be observed at a high PVA doping level. The proton conducting property of these membranes was investigated under both hydrous and anhydrous conditions. From 25 to 120 °C, the non-soaked and soaked (soaked in the water) membranes showed the proton conductivity of 19–68 and 9–31 mS cm−1 at 100% relative humidity (RH), respectively. Under completely dry conditions, the proton conductivity of these membranes showed large dependence on the temperature and the proton conductivity of 4.7–21 mS cm−1 was achieved at 150 °C for these membranes. The excellent performance of these hybrid membranes under both wet and dry conditions demonstrated that they have potential use as electrolytes in polymer electrolyte membrane fuel cells (PEMFCs) operating either in a watery or in a water-free environment and so called “amphibious” proton conducting membranes.

Research highlights▶ PVA enhances the film-forming capacity at a high acid doping level. ▶ PVA does not influence the thermal stability obviously. ▶ Increasing PVA content leads to a matrix change between PVA and PGA. ▶ PVA facilitates the proton conduction of the soaked membrane under wet conditions.