Recent advances in heteroatom substitution Sr2Fe1.5Mo0.5O6–δ oxide as a more promising electrode material for symmetrical solid-state electrochemical devices: A review

Abstract

In recent years, the interest in solid state electrochemical devices has significantly increased due to the various cases of their use in the energy field. The first case is the solid oxide fuel cells with both oxygen-ion and proton-conducting membranes. The second case is the electrolysis cells for hydrogen production. As a rule, in both cases, electrochemical cells consist of an ion-conducting membrane and two different electrodes. The present review is focused on structural, physicochemical, and electrochemical properties of a complex oxide based on strontium ferrite with partial replacement of iron by molybdenum. This complex oxide has a number of unique characteristics: in particular, it is able to function effectively as an electrode in oxidizing and strongly reducing atmospheres, which makes it a promising material for electrochemical devices based on solid electrolytes with symmetrical electrodes. Doping with elements in A-, B- and O-sublattices and surface modification increases electro-catalytic activity of Sr2Fe1.5Mo0.5O6−δ porous oxide material, which increases competitiveness of the electrode material for application in solid oxide electrochemical devices. Mechanisms for improving electro-catalytic activity are outlined stepwise by doping of different sublattices of double perovskite, by level of doping, and by different types of dopants. In conclusion, the data on material conductivity, power densities of both symmetric and fuel cells are systematized, and the remaining problems and prospects for future developments and upgrades of Sr2Fe1.5Mo0.5O6−δ oxide electrode material are described.