Tuning Electrochemical Performance by Microstructural Optimization of the Nanocrystalline Functional Oxygen Electrode Layer for Solid Oxide Cells

Bartosz Kamecki; Grzegorz Cempura; Piotr Jasiński; Sea-Fue Wang; Sebastian Molin

doi:10.1021/acsami.2c18951

Tuning Electrochemical Performance by Microstructural Optimization of the Nanocrystalline Functional Oxygen Electrode Layer for Solid Oxide Cells

ACS Appl Mater Interfaces. 2022 Dec 28;14(51):57449-57459. doi: 10.1021/acsami.2c18951. Epub 2022 Dec 15.

Authors

Bartosz Kamecki^{1

2}, Grzegorz Cempura³, Piotr Jasiński², Sea-Fue Wang⁴, Sebastian Molin²

Affiliations

¹ Advanced Materials Center, Faculty of Applied Physics and Mathematics, Gdańsk University of Technology, Gabriela Narutowicza street 11/12, 80-233 Gdańsk, Poland.
² Advanced Materials Center, Faculty of Electronics, Telecommunications, and Informatics, Gdańsk University of Technology, Gabriela Narutowicza street 11/12, 80-233 Gdańsk, Poland.
³ International Centre for Electron Microscopy, Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, Adama Mickiewicza street 30, 30-059 Kraków, Poland.
⁴ Department of Materials and Mineral Resources Engineering, National Taipei University of Technology, No.1, Sec. 3, Zhongxiao E. Rd., Taipei 106, Taiwan.

PMID: 36520672
DOI: 10.1021/acsami.2c18951

Abstract

Further development of solid oxide fuel cell (SOFC) oxygen electrodes can be achieved through improvements in oxygen electrode design by microstructure miniaturization alongside nanomaterial implementation. In this work, improved electrochemical performance of an La_0.6Sr_0.4Co_0.2Fe_0.8O_3-d (LSCF) cathode was achieved by the controlled modification of the La_0.6Sr_0.4CoO_3-d (LSC) nanocrystalline interlayer introduced between a porous oxygen electrode and dense electrolyte. The evaluation was carried out for various LSC layer thicknesses, annealing temperatures, oxygen partial pressures, and temperatures as well as subjected to long-term stability tests and evaluated in typical operating conditions in an intermediate temperature SOFC. Electrochemical impedance spectroscopy and a distribution of relaxation times analysis were performed to reveal the rate-limiting electrochemical processes that limit the overall electrode performance. The main processes with an impact on the electrode performance were the adsorption of gaseous oxygen O₂, dissociation of O₂, and charge transfer-diffusion (O^2-). The introduction of a nanoporous and nanocrystalline interlayer with extended electrochemically active surface area accelerates the oxygen surface exchange kinetics and oxygen ion diffusions, reducing polarization resistances. The polarization resistance of the reference LSCF was lowered by one order of magnitude from 0.77 to 0.076 Ω·cm² at 600 °C by the deposition of a 400 nm LSC interlayer at the interface. The developed electrode tested in the anode-supported fuel cell configuration showed a higher cell performance by 20% compared to the cell with the reference electrode. The maximum power density at 700 °C reaches 675 and 820 mW·cm^-2 for the reference cell and the cell with the LSC interlayer, respectively. Aging tests at 700 °C under a high load of 1 A·cm² were performed.

Keywords: distribution of relaxation times; electrochemical impedance spectroscopy; electrode−electrolyte interface; nanocrystalline layer; oxygen electrode interlayer; solid oxide fuel cells; spray pyrolysis.