resumo
Strontium-cerium manganite Sr 0.7 Ce 0.3 MnO 3-s was evaluated as a Co-free candidate material for oxygen electrodes of commercial-grade solid oxide fuel and electrolysis cells (SOFC/SOEC). Sr 0.7 Ce 0.3 MnO 3-s ceramics was confirmed to show high electrical conductivity (304-309 S/cm at 700-800 degrees C) and moderate thermal expansion coefficient (12.3 ppm/K at 25-1100 degrees C) at atmospheric oxygen pressure, and very small changes in oxygen nonstoichiometry on p(O2)-T cycling under oxidizing conditions below 1000 degrees C. The studies of oxygen transport properties by electrical conductivity relaxation technique revealed that, compared to (La,Sr)(Co,Fe)O3-s perovskites, Sr 0.7 Ce 0.3 MnO 3-s exhibits an order of magnitude lower oxygen diffusivity, with D chem in the range (4-10) x 10-6 cm2/s at 875-950 degrees C, but similar oxygen surface exchange kinetics, with k ex in the range (0.5-5.6) x 10-3 cm/s at these temperatures. The electrochemical performance of fuel electrode-supported solid oxide cells with Sr 0.7 Ce 0.3 MnO 3-s oxygen electrodes at 700-800 degrees C was found to be moderate but could improved by surface activation of Sr 0.7 Ce 0.3 MnO 3-s electrode layers with praseodymia. The activation of the oxygen electrode resulted in a reduction in total polarization resistance of the cells by 2 and 7 times in SOFC and SOEC modes, respectively, under moderate current densities at 800 degrees C. The polarization losses in SOFC mode 700-800 degrees C were 1.5-2.0 times higher than in the SOEC regime. Further improvements in oxygen electrode performance are necessary to compete with solid electrolyte cells with (La,Sr)CoO3-s and (La,Sr)(Co,Fe)O3-s electrodes.
palavras-chave
FUEL-CELLS; THERMOCHEMICAL EXPANSION; ELECTRICAL-PROPERTIES; PRASEODYMIUM OXIDE; CHEMICAL DIFFUSION; DOPED CERIA; SOFC; CONDUCTIVITY; CATHODES; EXCHANGE
categoria
Chemistry; Electrochemistry; Energy & Fuels
autores
Jagielski, S; Kluczowski, R; Boiba, D; Zakharchuk, K; Ajdys, L; Naumovich, Y; Yaremchenko, AA
nossos autores
Aleksey Yaremchenko
Investigador Principal
Kiryl Zakharchuk
Estudante de doutoramentoProjectos
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
agradecimentos
This work was developed within the scope of project DC-SOFEC funded by the NCN (Poland, UMO-2018/30/M/ST8/00675) , Project ACT-SOC funded by the NAWA (Poland, BPN/BPT/2021/1/00041/U/00001) and the FCT (Portugal) , and Project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 (DOI 10.54499/UIDB/50011/2020) , UIDP/50011/2020 (DOI 10.54499/UIDP/50011/2020) & LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020) , financed by National funds through the FCT/MCTES (PIDDAC) , Portugal.