Renewable Energy Sources, Hydropower Materials for Fuel Cells Based on Barium and Strontium Cobaltites Synthetized on a Solar Furnace

Study was carried out on materials based on perovskite structures of cobaltite compositions of strontium \({\text{SrCoO}_{{3 - \delta }}}\) and barium \({\text{BaCoO}_{{3 - \delta }}},\) obtained by synthesis from a melt of a stoichiometric mixture of cobalt oxide with strontium carbonates Co₂O₃ + SrCO₃ or barium Co₂O₃ + BaCO₃ in a stream of high (150 W/cm²) density concentrated solar radiation in a solar furnace, followed by quenching in water and sintering at a temperature of 1300 K. Hexagonal barium and strontium cobaltites had a developed fine microstructure (grains in the form of densely packed polyhedrons of various shapes 2–5 μm in size), a semiconductor character of electrical conductivity, and a low thermal expansion coefficient (average 12.6 × 10^–6 K^–1) in the temperature range 300–1100 K. The change in the electrical resistance of materials is due to the high affinity of cobalt ions for oxygen, which causes oxygen sorption and, as a result, leads to changes in the electronic structure of cobalt ions, as a result of charge transitions 2Co³⁺ = Co²⁺ + Co⁴⁺. This circumstance indicates the possibility of using materials based on barium and strontium cobaltites as selective absorbers, oxygen membranes, or cathode materials for the manufacture of solid-oxide fuel cells in the production of electrical energy as well as materials for hydrogen storage.