Enhanced proton conductivity of the hybrid membranes by regulating the proton conducting groups anchored on the mesoporous silica

Mesoporous silica submicrospheres with -NH2 groups or -PO3H2 groups on the outer surface, and -PO3H2 groups on the inner pore walls are prepared and designated as N-P-SiO2 and P-P-SiO2, respectively. Both kinds of silica submicrospheres are introduced into Nafion membrane matrix to fabricate hybrid membranes. The water uptake, membrane swelling properties, and proton conductivities at different temperatures and different relative humidities of the hybrid membranes are characterized. Proton conducting performances of the hybrid membranes are all enhanced compared to that of the pristine Nafion membrane, and the highest proton conductivity is 0.339 S cm(-1) (115 degrees C, 100% RH). At 100% RH, Nafion/N-P-SiO2 membranes exhibit higher proton conductivities than the Nafion/P-P-SiO2 counterparts; while at low humidities, the proton conductivities of the Nafion/P-P-SiO2 membranes are enhanced more pronouncedly than those of the Nafion/N-P-SiO2 counterparts. The different increasing tendencies of the proton conducting performance could be attributed to the varied synergistic effects between the proton conducting groups introduced by the mesoporous silica and the groups anchored on the membrane matrix. (C) 2014 Elsevier B.V. All rights reserved.