resumo
In this work, we conduct a systematic investigation of composite oxygen electrodes for Solid Oxide Cells (SOCs) based on the recently emerging misfit calcium cobaltite material, Ca3Co4O9+delta - C349. Its electrochemical performance is shown to be limited by its low intrinsic level of ionic conductivity, thus, requiring the addition of an ionic-conducting composite phase. In this respect, Ce0.8Gd0.2O2-delta (CGO) is the state-of-the-art choice due to its excellent ionic conductivity. Nonetheless, little attention has been given to the use of alternative ionic phases, such as Ce0.8Pr0.2O2-delta, which also offer minor levels of p-type conductivity. Therefore, we try to elucidate the influence of this minor electronic component in this phase, on the resultant oxygen reaction mechanism of the composite electrode. We demonstrate that a preferential series pathway for the oxygen reaction occurs in the CGO-based electrode, performing better at high temperatures and low oxygen partial pressures. Conversely, the CPO-based electrode presents superior performance under highly oxidising conditions and at low temperatures, related to an increasing importance of possible parallel reaction pathways. The results are supported by a detailed mechanistic study, based on a Distribution Function of Relaxation Times (DFRT) analysis, allowing clarification of potential mechanistic models for both electrodes.
palavras-chave
PRASEODYMIUM-DOPED CERIA; OXIDE FUEL-CELLS; THERMAL-EXPANSION; ELECTROCHEMICAL PERFORMANCE; TRANSPORT-PROPERTIES; MIXED CONDUCTIVITY; RELAXATION-TIMES; CATHODE; PR; MICROSTRUCTURE
categoria
Electrochemistry
autores
Araujo, AJM; Loureiro, FJA; Grilo, JPF; Macedo, DA; Paskocimas, CA; Fagg, DP
nossos autores
Francisco José Almeida Loureiro
Bolseiro de investigação
João Grilo
Investigador Júnioragradecimentos
This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior - Brasil (CAPES) - Finance Code 001. Allan J. M. Araujo acknowledges the Conselho Nacional de Desenvol-vimento Cientifico e Tecnologico (CNPq/Brazil, reference number 200439/2019-7). Jo ~ao P. F. Grilo, Carlos A. Paskocimas and Daniel A. Macedo also thank CNPq/Brazil (482473/2010-0, 446126/2014-4, 308548/2014-0, 307236/2018-8, 431428/2018-2 and 309430/2019- 4). The Aveiro team acknowledges projects PTDC/CTM-CTM/2156/2020, PTDC/QUI-ELT/3681/2020, POCI-01-0145-FEDER-032241, UID/EMS/00481/2019-FCT, CENTRO-01-0145-FEDER-022083, funded by FEDER, Centro Portugal Regional Operational Programme (Centro2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF) and by national funds (OE), through FCT/MCTES. Francisco J. A. Loureiro acknowledges FCT for the financial support with the reference CEECIND/ 02797/2020.