In situ exsolution of Ni particles on the PrBaMn2O5 SOFC electrode material monitored by high temperature neutron powder diffraction under hydrogen

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 8; no. 7; pp. 3590 - 3597
• Main Authors: Bahout, Mona, Managutti, Praveen B, Dorcet, Vincent, Annie Le Gal La Salle, Paofai, Serge, Hansen, Thomas C
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2020
• Subjects: Anodes; Atmosphere; Catalysts; Chemical Sciences; Diffraction patterns; Electrochemical analysis; Electrochemistry; Electrode materials; Electrode polarization; Electrodes; Heating; High temperature; Hydrogen; Material chemistry; Metal particles; Neutron diffraction; Nickel; Optimization; Orthorhombic phase; Particle physics; Perovskites; Phase transitions; Spectroscopy; Transmission electron microscopy; Electrochemical performance; Initial composition; Orthorhombic phase; Hydrogen; Barium compounds; Neutrons; Praseodymium compounds; Polarization resistances; Electrode material; Manganese oxide; Hydrogen atmosphere; Perovskite; Impedance spectroscopy measurements; Electrochemical electrodes; Powder metals; Solid oxide fuel cells (SOFC); Nickel; High resolution transmission electron microscopy; Anodes; Rietveld analysis; Real time observation; Nickel oxide; Electrochemical impedance spectroscopy; Neutron powder diffraction
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c9ta10159d

NiO has been incorporated into the Pr0.5Ba0.5MnO3−δ perovskite to produce, upon heating under a hydrogen atmosphere, in situ exsolved Ni-catalysts supported on the PrBaMn2O5 anode material. Transmission electron microscopy (TEM) and neutron powder diffraction (NPD) showed that the initial composition obtained by annealing in air at 950 °C consists of two perovskite phases: orthorhombic Pr0.65Ba0.35Mn0.975Ni0.025O3 (S.G. Ibmm, ∼75 wt%) and 2H-hexagonal BaMnO3−δ (S.G. P63/mcm, ∼25 wt%). On heating the two-phase sample under wet hydrogen, MnO particles exsolve at T ∼ 500 °C meanwhile the orthorhombic phase transforms to tetragonal (S.G. I4/mcm) then to cubic (S.G. Pm3m) at T ∼ 665 °C. When the temperature approaches 900 °C, the emergence of Ni metal particles was detected in the neutron diffraction patterns meanwhile the two perovskite phases start to transform into a Ni-free layered double perovskite, PrBaMn2O5. In situ real time observation of the structural changes under hydrogen atmosphere provided evidence of the simultaneity of Ni exsolution and phase transformation within our timescale resolution. From quantitative Rietveld analysis, the fraction of exsolved nickel represents the whole amount of Ni introduced in the synthesis. Impedance spectroscopy measurements in a 5% H2/Ar atmosphere show promising electrochemical performance for the Ni-exsolved layered perovskite electrode with a polarization resistance of 0.4 Ω cm2 at 800 °C (0.135 Ω cm2 at 850 °C) without any optimization.