FRANCISCO NOBUO TABUTI

FRANCISCO NOBUO TABUTI

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Steam reforming catalytic layer on anode-supported and metal-supported solid oxide fuel cells for direct ethanol operation
2023 - MACHADO, MARINA; TABUTI, F.; PIAZZOLLA, F.; MORAES, T.; ABE, R.; GUIMARAES, R.M.; MIURA, Y.; FUKUYAMA, Y.; FONSECA, F.C.
A catalyst based on lanthanum chromite with exsolved metallic ruthenium nanoparticles (LaCrO3-Ru) was applied as a catalytic layer for internal ethanol steam reforming of anode-supported and metal-supported solid oxide fuel cells. The metal support exhibits limited catalytic properties for the ethanol steam reforming reaction. Thus, the LaCrO3-Ru catalysts were optimized for operating temperatures in the 600-700 °C range to promote stable ethanol reforming. The catalytic layer had no significant impact on the electrochemical properties of the fuel cell, and samples with and without the catalytic layer exhibited similar performance in hydrogen. Initial durability tests with LaCrO3-Ru layer have shown that the catalytic layer plays a crucial role in the stability of the metal-supported fuel cell under ethanol.
W-doped Lanthanum Molybdenum Oxide/Lithium-Sodium-Potassium Carbonate Composite Membranes for Carbon Dioxide Permeation
2023 - MEDINA, MIDILANE S.; CARVALHO, SABRINA G.M.; TABUTI, FRANCISCO N.; MUCCILLO, ELIANA N.S.; FONSECA, FABIO C.; MUCCILLO, REGINALDO
Single-phase tungsten-doped lanthanum molybdenum oxide (La2MoWO9) ceramic powders were synthesized using the complex polymerization technique. Porous ceramic pellets were obtained by thermally removing graphite, which served as a pore former. The porous pellets were then impregnated with molten eutectic lithium-sodium-potassium carbonates. The energy dispersive X-ray analysis and scanning electron microscopy (FEG-SEM) images of the external and fracture surfaces of the La2MoWO9-(Li,Na,K)2CO3 composite dual-phase membrane revealed the percolation of the carbonate mixture through the pores. Electrochemical impedance spectroscopy measurements conducted at temperatures below and above the melting point of the eutectic carbonate composition demonstrated the contributions of oxygen and carbonate ions to the ionic conductivity of the dual membrane. The electrical conductivity of the carbonate ions within the membrane was continuously monitored for over 1300 h with negligible degradation, implying that the membrane could be used for long-term monitoring of CO2 without aging effects. A comparison of FEG-SEM images taken before and after this endurance test suggested minimal fouling, indicating that the membrane could potentially replace similar zirconia- and ceria-based composite membranes.
Desenvolvimento de célula a combustível de óxido sólido de temperatura intermediária a etanol direto com camada catalítica à base de céria
2023 - TABUTI, FRANCISCO N.
As células a combustível de óxidos sólidos (SOFC) apresentam diversas vantagens com relação a dispositivos tradicionais geradores de energia, inclusive se comparadas a outros tipos de célula a combustível. Entre as principais características das SOFC destacam-se: elevada eficiência de conversão, descentralização da produção de energia, possibilidade de uso de combustíveis diversos como gás natural e etanol - que são estratégicos para Brasil - e a baixa emissão de poluentes. Entretanto, existem várias barreiras a serem superadas para a difusão dessa tecnologia. Entre elas, a alta temperatura de operação da célula - que resulta em vários problemas para montagem e operação de um sistema de potência elevando o custo do sistema - e a desativação da célula devido à deposição de carbono na superfície do anodo de níquel quando a célula é alimentada com hidrocarbonetos. Muitas pesquisas têm buscado superar estes problemas garantindo a estabilidade da SOFC. A estratégia escolhida para se tentar solucionar esse problema é a utilização de componentes anódicos ativos para reforma catalítica do combustível, associado a um processo de reforma interna do combustível, fornecendo H2 e CO, passíveis de oxidação eletroquímica. Desta maneira, este trabalho de doutoramento aborda estes dois aspectos: (I) baixar a temperatura de operação da célula para temperaturas intermediárias, ou seja, de 850 °C para 600 °C e (II) utilização direta do etanol como combustível pelo processo de reforma interna. São apresentados os resultados de testes de células operando com etanol direto em alta temperatura e resultados de células suportadas no anodo com camadas catalíticas - sem a presença de metais preciosos - operando com etanol direto em temperaturas intermediárias. São descritos os procedimentos para fabricação da célula suportada no eletrólito e para preparação e aplicação das suspensões utilizadas nas diferentes camadas da célula. Também são descritos os sistemas utilizados nos testes de célula. Como principal resultado, obteve-se a estabilização da corrente de saída da célula vii operando com etanol direto tanto a 850 °C quanto a 700 °C sem adição de água ao combustível.
Exploring the stability of direct ethanol solid oxide fuel cells at intermediate temperature
2021 - FONSECA, F.C.; TABUTI, F.; MORAES, T.; ABE, R.; GUIMARAES, R.M.; MIURA, Y.; FUKUYAMA, Y.
Anode supported fuel cells were tested in direct (no water added) bioethanol at intermediate temperature (600°C and 700°C). The standard fuel cell has reasonable short-term stability under dry ethanol if current is continuously drawn at a minimum fuel utilization factor at 700ºC. However, the YSZ/Ni anode develops carbon deposits as inferred from post fuel cell test analyses and fixed bed steam reforming catalytic tests at 600°C. Thus, an active catalytic layer with tailored properties for ethanol internal reforming was studied. Initial tests investigated the Ir/gadolinium-doped ceria catalysts previously proven stable at 850°C. The main results have shown that the catalytic layer has no significant effect on the performance of the fuel cell running under hydrogen. The use of a ceria-based catalytic layer has enhanced the stability of the fuel cell under dry ethanol at 700°C, but stable operation at 600°C requires the development of more active catalyst.
The role of the ceria dopant on Ni / doped-ceria anodic layer cermets for direct ethanol solid oxide fuel cell
2021 - SILVA, A.A.A. da; STEIL, M.C.; TABUTI, F.N.; RABELO-NETO, R.C.; NORONHA, F.B.; MATTOS, L.V.; FONSECA, F.C.
The effect of ceria dopant aiming at stability in Ni/doped-ceria anodic layers for direct ethanol solid oxide fuel cells (SOFC) was studied. Solid solutions of ceria doped with Y, Gd, Zr, or Nb (10 mol%) impregnated with NiO were tested in a fixed bed reactor for ethanol conversion reactions and for direct (dry) ethanol SOFC. The ceria dopant showed a marked effect on both the catalytic and the electrical transport properties of the ceramic support. Catalytic activity data revealed that the studied materials deactivate in ethanol decomposition reaction but are stable for ethanol steam reforming. Thus, feeding dry ethanol to the SOFC with a Ni/doped-ceria anodic catalytic layer evidenced that water produced from the electrochemical hydrogen oxidation provides steam for the internal reforming resulting in great stability of the fuel cells tested during ~100 h. The combined catalysis and SOFC results demonstrate Ni/doped-ceria is as candidate anode layer for stable SOFC running on bioethanol.
Development of ceria-based direct ethanol intermediate-temperature solid oxide fuel cell
2018 - TABUTI, FRANCISCO N.; PEREIRA, VICTORIA B.; PIAZZOLLA, FERNANDO; FONSECA, FABIO C.
Solid oxide fuel cells (SOFCs) have several advantages over traditional energygenerating devices. A key property is the possibility of using various fuels such as natural gas and ethanol, which are strategic for Brazil. This study addresses two aspects that need to be improved in SOFC: (a) the high operating temperature of the cell that brings several problems for assembly and operation of a power system, and (b) the deactivation of the cell due to the deposition of carbon on the surface of the nickel anode when the cell is fed with carbon-containing fuels. The properties of ceria-based/Ni cermets both as the anode material and as the catalytic layer for bio-ethanol fueled SOFC with yttria-stablilized zirconia electrolyte were investigated. Ceria-based/Ni cermets were studied as the catalytic layer deposited onto the standard yttria-stabilized zirconia/Ni anode for direct ethanol SOFCs. Properties of both Zr- and Nb-doped (10 mol%) ceria / Ni (15 vol%) cermets were investigated as the catalytic layer in direct ethanol SOFCs. Electrolyte-supported fuel cells with doped-ceria /Ni catalytic layer were tested for ~100 hours under (dry) ethanol. Fuel cells using the different ceria/Ni cermets showed excellent stability on ethanol. The promising results obtained with ceria-based anodes for SOFC of ethanol motivated the development of ceriabased SOFCs. Thus, intermediate-temperature SOFCs using doped-ceria electrolytes have been tested at 600 °C using hydrogen. Preliminary results show that direct ethanol SOFC are promising devices for efficient energy conversion at intermediate temperatures.
Anodic layers based on doped-Ceria/Ni cermet for direct ethanol fuel cells
2017 - SILVA, A.A. da; TABUTI, F.N.; MATTOS, L.V.; STEIL, M.C.; NORONHA, F.B.; FONSECA, F.C.
Ceria-based/Ni cermets were studied as the catalytic layer deposited onto the standard yttria-stabilized zirconia/Ni anode for direct ethanol solid oxide fuel cells. The influence of the dopant on both Zr- and Nb-doped (10 mol%) ceria and pure ceria was investigated on the properties of cermets with Ni ~15% volume fraction. Electrolyte-supported fuel cells with ceria-based/Ni catalytic layer were tested for ~100 hours under (dry) ethanol. Fuel cells using the different ceria/Ni cermets showed excellent stability on ethanol, irrespectively of the different properties of the ceramic phase of the catalytic layer. Fuel cells results confirmed that the studied ceria-based cermets are stable catalysts towards ethanol steam reforming.
Optimization of spin-coated electrodes for electrolyte-supported solid oxide fuel cells
2017 - NOBREGA, SHAYENNE D. da; MONTEIRO, NATALIA K.; TABUTI, FRANCISCO; FLORIO, DANIEL Z. de; FONSECA, FABIO C.
Electrodes for electrolyte-supported solid oxide fuel cells (SOFC’s) were fabricated by spin coating. Strontium- doped lanthanum manganite (LSM) cathode and nickel yttria-stabilized zirconia cermet anodes were synthesized and processed for enhanced deposition conditions. The influence of electrode microstructural parameters was investigated by a systematic experimental procedure aiming at optimized electrochemical performance of single cells. Polarization curves showed a strong dependence on both electrode thickness and sintering temperature. By a systematic control of such parameters, the performance of single cells was significantly enhanced due to decreasing of polarization resistance from 26 Ω cm² to 0.6 Ω cm² at 800°C. The results showed that spin-coated electrodes can be optimized for fast and cost effective fabrication of SOFCs.
Influence of microwave-assisted hydrothermal treatment on the properties of nickel oxide-zirconia based composites
2016 - PINHEIRO, L. B.; TABUTI, F.N.; MARTINELLI, A.E.; FONSECA, F.C.
Nickel/gadolinium-doped ceria anode for direct ethanol solid oxide fuel cell
2014 - AUGUSTO, BRUNO L.; NORONHA, FABIO B.; FONSECA, FABIO C.; TABUTI, FRANCISCO N.; COLMAN, RITA C.; MATTOS, LISIANE V.