On the complexity of proton conduction phenomena

The proton transport mechanisms in systems containing water and in cubic pe rovskite-type oxides are analyzed in detail in terms of chemical interactio ns. Some features of proton transport in hydroxides and systems containing ore-acid anions or heterocycles as proton solvents are also described. Desp ite the differences between the rather complex proton conduction mechanisms in these systems, significant structural and dynamical variations of hydro gen bond interactions as a result of a good balance of chemical interaction s in a wide range of configuration space have been identified as common fea tures. These allow for high rates of proton transfer and structural reorgan ization, the two reactions involved in long-range proton transport. From th e analyses and additional information on mesoscopic effects, suggestions ar e also made for the optimization of the mobility of protonic defects in hyd rated, acidic polymers and perovskite-type oxides, which are interesting as separator materials for fuel cells. For the former, the importance of the microstructure is emphasized, while, for the latter, the prospects for III- III perovskites are stressed. (C) 2000 Elsevier Science B.V. All rights res erved.