[Note] The degree of lattice strain in the electrode, the correlation between enthalpy segregation and electrode reaction.
Fuel cells are the key energy technologies of the future and can become environmentally friendly renewable energy sources. In particular, solid oxide fuel cells composed of ceramic materials are receiving more and more attention due to their ability to directly convert various forms of fuels such as biomass, LNG and LPG into electrical energy. KAIST researchers describe a new technology that improves the chemical stability of electrode materials and extends life by using very small amounts of metal.
The core factor determining the performance of a solid oxide fuel cell is the cathode in which the oxygen reduction reaction takes place, and an oxide having a perovskite structure (ABO3) is usually used in the cathode. However, although perovskite oxides have high performance in initial operations, their performance degrades over time, limiting their long-term use. In particular, the conditions of the high-temperature oxidation state required for the operation of the cathode cause surface segregation, in which a second phase such as strontium oxide (SrOx) accumulates on the surface of the oxide, resulting in deterioration of electrode performance.
Using computational chemistry and experimental data, the team of Professor WooChul Jung of the Department of Materials Science and Engineering observed that the localized squeezed state around the Sr atom in the perovskite electrode lattice weakened the Sr-O bond strength, thereby facilitating the separation of the ruthenium. The team found that local variations in strain distribution in perovskite oxides are the main cause of surface separation. Based on these findings, the team incorporated different sizes of metals in the oxide to control the degree of lattice strain in the cathode material and effectively inhibit enthalpy segregation.
Professor WooChul Jung said: "This technology can be achieved by adding a small amount of metal atoms to the material synthesis process without the need for additional processes. I hope this technology will be effective in developing highly durable perovskite oxide electrodes. ."
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