Proton conductivity of zwitterionic-type molecular solids under intermediate temperature and anhydrous conditions

Anhydrous proton conducting material for polymer electrolyte membrane fuel cell (PEFC) was prepared by the mixing of zwitterionic-type molecular solid 3-pyridinesulfonic acid (PS) and organic acid methylenediphosphonic acid (MP). As a result, PS molecule, which has sulfonic acid and pyridine group in its structure, showed the proton conductivity of 4 × 10−5 S cm−1 at 160 °C under anhydrous condition. Surprisingly, by the mixing of MP to PS material, the PS–MP composite material exhibited a conductivity of 2 × 10−3 S cm−1. Moreover, the conductivity of PS–MP composite material did not decrease under the heating at 160 °C for 50 h.