Enhanced proton conductivity from phosphoric acid-imbibed crosslinked 3D polyacrylamide frameworks for high-temperature proton exchange membranes

To enhance the proton conductivity of high-temperature proton exchange membranes (PEMs), one promising approach is to increase the proton conductor loading per unit membrane. The objectives of this research are to demonstrate the feasibility of the concept and realize H3PO4-imbibed polyacrylamide (PAM) frameworks as high-temperature PEMs using the unique absorption and retention of crosslinked PAM to H3PO4 aqueous solution. The 3D framework of PAM provides space to hold H3PO4 into the porous structure, which can be controlled by adjusting the polymerization process and crosslinking agent and initiator dosages. Results show that the H3PO4 loadings and therefore the conductivities of the membranes are significantly enhanced by expanding the size of pore structure. Proton conductivities as high as 0.0749 S cm−1 at ambient-temperature and fully hydrated state and 0.0635 S cm−1 at 183 °C under anhydrous atmosphere are recorded. The high conductivities at high temperatures in combination with the simple preparation, low cost, scalable hosts and proton conductors demonstrate the potential use of hydrogel materials in high-temperature PEMs.