Exsolution is a trendy way to improve the catalytic activity of oxide materials which can be used in electrochemical devices. Its beneficial effect on operation of e.g. Solid Oxide Fuel Cells has been extensively discussed in the literature. This is due to the formation of metallic nanoparticles which are well socketed in the oxide support and therefore resistive to agglomeration and coarsening under SOFC operating conditions. In the case of perovskite ABO₃ structure, the catalytically active cations are incorporated into the B-site during the synthesis in air, and then the nanoparticles are exsolved in reductive atmosphere. Such technique has already allowed to obtain nanoparticle-decorated perovskite with transition metal catalysts such us: Ni [1], Co [2], Pd [3], Pt [4]. The aim of this work is to verify the possibility to exsolve nanoparticles of transition metals on the surface of strontium titanate-based compounds.
The (La_0.3Sr_0.6Ce_0.1)_0.9Me_0.1Ti_0.9O_3-δ (Me=Co, Cu, Fe, Mn, Ni) compounds were successfully synthesized using the solid state reaction method. After reducing in dry hydrogen at different temperatures, a formation of numerous exsolved metal nanoparticles decorating the perovskite surface was confimed in all fabricated compounds. The nonstoichiometry in the A sublattice of the perovskite structure was found to promote smaller size and higher surface density of exsolved particles. The smallest particles with an average size of 30 nm were successfully exsolved on the surface of Ni containing LSCNT perovskite.
The thermal and electrical properties of LSCMeT were investigated to determine the potential for its further application as SOFC anode materials. For all samples, a transition from semiconductor-type behavior to metallic-type behavior was observed at a certain temperature (~300 °C) in H₂ atmosphere. Although the measured values of total electrical conductivity are quite low (up to 5 Scm^-1), they can be further improved via the increase of reduction temperature (over 900 °C). The average coefficient of thermal expansion of all measured samples in the temperature 50-1000 °C was in the range of 11-12 ×10-6 K^-1 and was found to be similar to that of yttria-stabilized zirconia (YSZ).
 
References
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[4] M. Kothari, Y. Jeon, D.N. Miller, A.E. Pascui, J. Kilmartin, D. Wails, S. Ramos, A. Chadwick, J.T.S. Irvine, Nat. Chem. 13 (2021) 677–682
  
Acknowledgements
The research project was supported by the National Science Center under grant No. NCN 2021/42/E/ST5/00450.