STUDY OF THE EXSOLUTION PROCESS OF FE-NI NANOPARTICLES IN Srx(Ti,Fe,Ni)O3-δ PEROVSKITES SOFC ELECTRODES

SANTAYA M.; TROIANI H. E.; ZHU T; BARNETT S.; L. MOGNI.

La Plata

Encuentro; Nano 2018; 2018

YTEC

Mixedionic and electronic conductor (MIEC) oxides have been widely studied aspotential candidates for solid oxide fuel cell (SOFC) anodes [1,2]. This is dueto their good stability when working with C-based fuels and to the fact thatthe mixed conductivity extends the fuel oxidation reaction to the entire oxidesurface [2]. Another advantage of MIEC´s is that they can also showelectro-catalytic activity for O2-reduction,allowing use in symmetrical configuration S-SOFC, thus reducing manufacturingand operation costs. The electrode polarization resistance of MIEC´s can bereduced by introducing electro-catalytic nanoparticles on the oxide surface. Inthis work, the formation of Ni-Fe alloy nanoparticles by ex-solution from Srx(Ti,Fe,Ni)O3-δ (STFN) perovskites in different temperatures and H2/H2O/Aratmospheres is studied. Theeffects of the main variables affecting the process: Sr-sitedeficiencies, gas atmosphere and STF microstructure are discussed. The Fe-Ninanoparticles structure, microstructure and composition influences areexplored. The size and composition of the alloy nanoparticles is shown todepend on the conditions in which the sample is reduced (temperature,atmosphere and time) [3]. Previous works have shown A-site deficiency to be afundamental driving force for ex-solution to occur [4]; however in this study,A-site deficiency does not appear to play an important role in determining thecomposition of the ex-solved nanoparticles.Otherauthors reported that the metal nanoparticles can be re-incorporated into theoxide by re-oxidizing the sample at the same temperature at which ex-solutionhad been performed. For the Fe-Ni alloy nanoparticles studied in this work, Feseems to re-incorporate into the oxide although Ni does not, and thus NiOnanoparticles remain on the surface (Figure 1).Thiscould be an important result for both regenerating the electrodes andmaintaining highly active catalytic nanoparticles on the surface, which wouldimprove the material performance as a cathode. All these facts are put incontext to rationalize the ex-solution phenomena in perovskitesystems.