Oxygen and hydrogen mobility are among the important characteristics for operation of solid oxide fuel cells, permselective membranes and many other electrochemical devices. This, along with other characteristics, enables reaching a high power density of solid oxide fuel cells and a high oxygen or hydrogen permeation fluxes for membranes. This work focuses on oxygen and hydrogen diffusion of mixed ionic (oxide ionic or/and protonic) – electronic conducting materials for these devices and its role in the performance. Ionic transport properties of conventional and state-of-the-art materials are reviewed.

Recent trends concerning hydrogen as a fuel of the future and problems related to its production, storage and utilization increase the demand for efficient technologies related to these problems. A large part of such technologies is related to application of advanced materials based on various complex oxides which are used as efficient catalysts for fuel transformation into hydrogen and syngas, materials for membranes with selective permeability for hydrogen and syngas production, components of solid oxide fuel cells/electrolyzers as well as many other applications in energy, electrochemistry and catalysis. Such materials are typically based on oxides and solid solutions with perovskite and fluorite structures or their derivatives. Attention is also paid to the materials based on spinel, apatite, mayenite, sheelite, fergusonite structures. The above-mentioned materials are continuously studied in order to modify and optimize their functional properties. On the other hand, other classes of materials (weberites, monazites, etc.) are recently discovered and considered as candidate materials for the aforementioned applications due to their specific functional properties or a great potential of their improvement. In this review, some of these materials are considered.