Exsolution from Ni-Co Doped Sr(Ti,Fe)O3 and Sr2FeMoO6 Perovskites for Solid Oxide Cell Electrodes Studied by Synchrotron X-ray Spectroscopies at the Solid-Gas Interface

Catalina E. Jiménez^a, Mauricio D. Arce^b, Mariano Santaya^b, Andrés López-García^c, Alfonso J. Carrillo^c, Rosario Suárez Anzorena^a, Lucía M. Toscani^d, Emilia A Carbonio^a^,^e, Raul Garcia-Diez^a, Marianne van der Merwe^a^,^h, Enggar R. Wibowo^a, Virginia Pérez Dieste^f, Ignacio J. Villar^f, Regan G. Wilks^a, Axel Knop-Gericke^e^,^g, Ana B. Hungría^h, Horacio E. Troiani^b, José M. Serra^c, Liliana V. Mogni^b, Marcus Bär^a^,ⁱ

^aHelmholtz-Zentrum für Materialen und Energie GmbH (HZB), 12489 Berlin, Germany

^bCAB-CNEA-CONICET, Centro Atómico Bariloche, 8400 S. C. de Bariloche, Rio Negro, Argentina

^cInstituto de Tecnología Química (ITQ-UPV-CSIC), 46022 Valencia, Spain.

^dInstituto de Tecnologías Emergentes y Ciencias Aplicadas (ITECA-UNSAM-CONICET), 1650 Buenos Aires, Argentina

^eFritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany

^fALBA Light Source, 08290 Barcelona, Spain.

^gMax Planck Institute for Chemical Energy Conversion (MPI-CEC), 45470 Mülheim an der Ruhr, Germany

^hUniversidad de Cádiz, 11510 Puerto Real, Spain

ⁱFriedrich-Alexander-Universität Erlangen-Nürnberg, 91058 Erlangen, Germany

^jHelmholtz Institute Erlangen-Nürnberg for Renewable Energy (HI ERN), 12489 Berlin, Germany

Proceedings of MATSUS Fall 2025 Conference (MATSUSFall25)

E.16 Exsolution for sustainable energy materials - #ExSusMat

València, Spain, 2025 October 20th - 24th

Organizers: Alfonso Carrillo, Dragos Neagu and Jose Manuel Serra

Invited Speaker, Catalina E. Jiménez, presentation 315
Publication date: 17th July 2025

Mono-, bi- and tri-metallic nanoparticle exsolution from perovskite oxides has become a widespread strategy to boost the performance of solid oxide cell (SOC) electrodes by enhancing the electrocatalytic activity at the solid/gas interface [¹]. A particular interesting group are redox stable perovskites, designed to exsolve nanoparticles and able to perform as anode or cathode in symmetric cells at intermediate temperatures (500 – 700 °C) with high efficiencies^{[1, 2]}. These perovskites are usually highly functionalized oxides with complex stoichiometries.

While high resolution scanning and transmission electron microscopies and electron spectroscopies are able to characterize the NP decoration over a wide length scale, or access quite accurately nanoparticle composition after exsolution, in-situ and operando synchrotron-based methods such as ambient pressure photoelectron and absorption fine structure spectroscopies (AP-XPS/NEXAFS) offer the required surface sensitivity, chemical and elemental specificity needed to distinguish the role of each element during exsolution near the solid/gas interface. Synchrotron-based in-situ X-ray diffraction on these materials offers a complementary structural perspective of the transformations undergone by the electrode materials during thermal exsolution.

In this contribution, we showcase this combination of in-situ/operando synchrotron-based methods with electron microscopies and spectroscopies applied to Sr(Ti,Fe)O_3-d perovskites ^[3-5] and Sr₂FeMoO_6-d double perovskites, doped with Ni and Co^[6]. In a next step, Ni-doped Sr(Ti,Fe)O_3-d perovskites were used to fabricate model cells for a device-driven optimization applying polarization and other electrochemical techniques such as voltammetry, chronoamperometry and electrochemical impedance spectroscopy while monitoring the electrode evolution with synchrotron-based techniques. Polarization can modify the surface chemistry of the working electrode, offering opportunities for tuning NP composition or regenerating the working electrode material by reversing exsolution or investigate SOCs in fuel or electrolysis (SOFC/SOEC) operation modes.

References:

[1] New trends in nanoparticle exsolution, A. J. Carrillo, A. López-García, B. Delgado-Galicia and J. M. Serra, Chem. Commun., 2024,60, 7987-8007

[2] Ni-Substituted Sr(Ti,Fe)O3 SOFC Anodes: Achieving High Performance via Metal Alloy Nanoparticle Exsolution, Zhu T., Troiani H.E., Mogni L.V., Han M., Barnett S.A., Joule, 2018, 2, 478–496

[3] A perspective on low-temperature solid oxide fuel cells”, Gao Z., Mogni L.V., Miller E.C, Railsback J.G. and Barnett S.A., Energy Environ. Sci., 2016,9, 1602-1644

[4] Tracking the nanoparticle exsolution/reoxidation processes of Ni-doped SrTi0.3Fe0.7O3−δ electrodes for intermediate temperature symmetric solid oxide fuel cells, Santaya M., Jiménez C. E., Troiani H.E., Carbonio E.A., Arce M.D., Toscani L.M., Garcia-Diez R., Wilks R.G., Knop-Gericke A., Bär M. and Mogni L.V., J. Mater. Chem. A, 2022, 10, 15554-15568

[5] Exsolution versus particle segregation on (Ni,Co)-doped and undoped SrTi0.3Fe0.7O3-δ perovskites: Differences and influence of the reduction path on the final system nanostructure, Santaya M., Jiménez C. E., Arce M.D., Carbonio E.A., Toscani L.M., Garcia-Diez R., Knop-Gericke A., Mogni L.V., Bär M. and Troiani H.E, Int. J. of Hydrogen Energy, 2023, 48, 38842-38853

[6] Understanding the evolution of ternary alloyed nanoparticles during reversible exsolution from double perovskite oxides, A. López-García, A. J. Carrillo, C. E. Jiménez, R. Suarez Anzorena, R. Garcia-Diez, V. Pérez-Dieste, I. J. Villar-Garcia, A. B. Hungría, M. Bär and J. M. Serra, J. Mater. Chem. A, 2024,12, 22609-22626

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