Banca de DEFESA: MORENA BRITO DE FARIAS
Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.STUDENT : MORENA BRITO DE FARIAS
DATE: 20/09/2024
TIME: 08:30
LOCAL: https://videoconf-colibri.zoom.us/j/94147801962
TITLE:
Study of cobalt-free composite oxygen electrodes for solid oxide cells
KEY WORDS:
Solid Oxide Cell (SOC); Oxygen electrode; Electrochemical Impedance Spectroscopy (EIS); Mixed Ionic-Electronic Conductor (MIEC); Double perovskite, Ruddlesden-Popper phases.
PAGES: 135
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
SPECIALTY: Cerâmicos
SUMMARY:
Solid oxide cells are energy conversion devices that can operate in two modes: as fuel cells to produce electricity from hydrogen, and as electrolysis cells to generate hydrogen from electricity. In these devices, the oxygen electrode often faces challenges, such as slow reaction kinetics or interfacial degradation, which can significantly impact overall cell performance and thus require careful optimization. Traditionally, materials containing cobalt are widely used as oxygen electrodes due to their excellent kinetics for reactions with oxygen. However, one of the current challenges is to replace this critical element in energy applications due to concerns related to health, the environment, and limited geographic availability. In this thesis, the compounds Sr2Fe1.5Mo0.5O6-δ (SFM) and Lan+1NinO3n+1 (n = 1 and 3, LNO) are explored as cobalt-free oxygen electrodes, demonstrating excellent mixed ionic-electronic conduction properties. The electrodes were initially optimized by successive deposition of material layers onto the electrolyte substrate, resulting in a higher solid fraction near the electrode/electrolyte interface. This process not only optimized the thickness of the electrodes but also improved the distribution of ionic current from the electrolyte into the electrode, resulting in a reduction in polarization resistance (Rpol). Consequently, the optimized electrodes achieved Rpol values of ~0.6 Ω cm2 for SFM, ~4.9 Ω cm2 for La2NiO4+δ (L2N1), and ~12.9 Ω cm2 for La4Ni3O10-δ (L4N3) at 700 °C. Additionally, a new composite electrode of SFM with approximately 34 vol% of praseodymia doped ceria (Ce0.8Pr0.2O2-δ) was developed, leading to improvements in incorporation kinetics. However, the overall performance of this composite electrode was compromised by insufficient electronic conductivity (Rpol ~7.3 Ω cm2 at 700 °C). For the LNO electrodes, impregnation with praseodymium oxide (~10 wt%) resulted in a reduction in polarization resistance by ~7 times for L2N1 (Rpol ~0.7 Ω cm2) and ~17 times (Rpol ~0.8 Ω cm2) for L4N3 at 700 °C. This significant improvement is attributed to the catalytically active PrOx sites, which enhance oxygen dissociation and charge transfer processes. Overall, this work provides critical insights into the microstructural and compositional criteria essential for the future development of high-performance cobalt-free oxygen electrodes, contributing to the advancement of more sustainable and efficient solid oxide cells.
COMMITTEE MEMBERS:
Externa à Instituição - VANESSA CRISTINA DINIZ DA GRAÇA - UA
Externo à Instituição - ALLAN JEDSON MENEZES DE ARAÚJO - UA
Presidente - 1300987 - CARLOS ALBERTO PASKOCIMAS
Externo à Instituição - DANIEL ARAÚJO DE MACEDO - UFPB
Externo à Instituição - FABIO CORAL FONSECA - IPEN
Externo à Instituição - FRANCISCO JOSÉ ALMEIDA LOUREIRO - UA
Interno - 1350249 - RUBENS MARIBONDO DO NASCIMENTO