The understanding of the diffusion of H was critical to a number of technologies, such as electrochromics, fuel cells and sensors, as well as in the study of corrosion/embrittlement phenomena. The motion of H species was reviewed here by comparing three different systems. First, the mobility of the counter-ions in the insulating naturally occurring silicates, exemplified by vermiculite, where single crystals were available, was described. Such materials were suggested as the electrolyte for batteries and fuel cells. Second, a series of semiconducting transition metal oxides, predominantly of tungsten and molybdenum were considered. Finally, diffusion of protons in the metallic conducting tungsten bronzes was considered. In no case was ionic mobility very rapid unless a solvent such as water was present.

Hydrogen Motion in Oxides - From Insulators to Bronzes. M.S.Whittingham: Solid State Ionics, 2004, 168[3-4], 255-63