Proton transport properties in hybrid membranes investigated by ac-electrogravimetry

In this paper, a hybrid organic/inorganic membrane, based on poly(VDF-co-HFP) polymer associated to mesostructured modified silica and made through sol–gel techniques, was characterized by using ac-electrogravimetry. In order to perform experiments, a polypyrrole–heteropolyanion doped mediator film was inserted between the working electrode of the microbalance and the hybrid membrane. This mediator film, which is characterized by mixed conducting properties, is necessary to provide proton transfer between the different interfaces and in that way, the proton transport inside the hybrid film which is only an ionic conducting material. Proton transfer and transport was characterized through ac-electrogravimetry and an original theoretical approach was developed for extracting the attractive parameters. The change of the exchanged species concentration and the diffusion coefficient of the protons in the hybrid membrane, were estimated, for the first time, according to the applied potential. These studies pointed out that the low conductivity value in this hybrid membrane is related to i) the low diffusion coefficient of proton (10 − 7 cm 2 s − 1 ) in this membrane associated, ii) the low concentration of proton in the membrane (0.4 meq g − 1 ).