Monoammonium salts of multiprotic acids as dopants for proton-conductive hydrogel membranes: the effects of anions.

Monoammonium salts of diprotic acid (NHHSO) and triprotic acid (NHHPO), whose cations and anions are both potential proton carriers, were employed as dopants for proton-conductive hydrogel membranes to explore the effects of anions on thermal, mechanical, and electrochemical performance. Robust hydrogel membranes were obtained by radical copolymerization of acrylamide and ethylene glycol dimethacrylate dissolved in aqueous solutions of NHHSO and NHHPO. By virtue of the protonated ammonium cation, the ionic conductivities of the hydrogels doped with NHHSO and NHHPO were superior to those doped with the corresponding inorganic acids (HSO and HPO).