Three-dimensional hydrogel frameworks for high-temperature proton exchange membrane fuel cells

With an aim of enhancing anhydrous proton conductivity and phosphoric acid (H3PO4) retention, we here report the employment of three-dimensional (3D) polyacrylamide-graft-chitosan (PAAm-g-CS) frameworks as supporters to load enormous H3PO4. Intrinsic microporous structure can seal H3PO4 molecules in the interconnected 3D frameworks of PAAm-g-CS matrix during a dehydration process. The hydrogel membranes are thoroughly characterized by morphology observation, structural analysis, swelling kinetics, proton-conducting performances as well as electrochemical behaviors. Results show that H3PO4 loading and therefore proton conductivity of the resultant PEMs are dramatically improved by employing PAAm-g-CS matrix in comparison with H3PO4-doped polybenzimidazole membranes. The highest H3PO4 loading and anhydrous proton conductivity are 92.2 wt % and 0.083 S cm−1 at 165 °C, respectively. The high H3PO4 loading, reasonable proton conductivity in combination with simple preparation, low cost, and scalable matrix demonstrates the potential use of PAAm-g-CS hydrogel membranes in high-temperature proton exchange membrane fuel cells.