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Structural and electrical properties of LaNiO3 thin films grown on (100) and (001) oriented SrLaAlO4 substrates by chemical solution deposition method

Pontes, D. S. L.; Pontes, F. M.; Silva, Marcelo de Assumpcao Pereira da; Berengue, O. M.; Chiquito, A. J.; Longo, E.
Fonte: Elsevier; Amsterdam Publicador: Elsevier; Amsterdam
Tipo: Artigo de Revista Científica
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LaNiO3 thin films were deposited on SrLaAlO4 (1 0 0) and SrLaAlO4 (0 0 1) single crystal substrates by a chemical solution deposition method and heat-treated in oxygen atmosphere at 700 °C in tube oven. Structural, morphological, and electrical properties of the LaNiO3 thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and electrical resistivity as temperature function (Hall measurements). The X-ray diffraction data indicated good crystallinity and a structural preferential orientation. The LaNiO3 thin films have a very flat surface and no droplet was found on their surfaces. Samples of LaNiO3 grown onto (1 0 0) and (0 0 1) oriented SrLaAlO4 single crystal substrates reveled average grain size by AFM approximately 15-30 nm and 20-35 nm, respectively. Transport characteristics observed were clearly dependent upon the substrate orientation which exhibited a metal-to-insulator transition. The underlying mechanism is a result of competition between the mobility edge and the Fermi energy through the occupation of electron states which in turn is controlled by the disorder level induced by different growth surfaces.; FAPESP (08/57150-6, 11/20536-7); CNPq; CAPES

Structural and electrical properties of LaNiO3 thin films grown on (100) and (001) oriented SrLaAlO4 substrates by chemical solution deposition method

Pontes, D. S L; Pontes, F. M.; Pereira-Da-Silva, Marcelo A.; Berengue, O. M.; Chiquito, A. J.; Longo, Elson
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 8025-8034
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LaNiO3 thin films were deposited on SrLaAlO4 (1 0 0) and SrLaAlO4 (0 0 1) single crystal substrates by a chemical solution deposition method and heat-treated in oxygen atmosphere at 700° C in tube oven. Structural, morphological, and electrical properties of the LaNiO 3 thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and electrical resistivity as temperature function (Hall measurements). The X-ray diffraction data indicated good crystallinity and a structural preferential orientation. The LaNiO3 thin films have a very flat surface and no droplet was found on their surfaces. Samples of LaNiO3 grown onto (1 0 0) and (0 0 1) oriented SrLaAlO4 single crystal substrates reveled average grain size by AFM approximately 15-30 nm and 20-35 nm, respectively. Transport characteristics observed were clearly dependent upon the substrate orientation which exhibited a metal-to-insulator transition. The underlying mechanism is a result of competition between the mobility edge and the Fermi energy through the occupation of electron states which in turn is controlled by the disorder level induced by different growth surfaces. © 2013 Elsevier Ltd and Techna Group S.r.l.

Filmes finos de LaNiO3 e PZT preparados pelo métodos das soluções precursoras poliméricas e depositados em substratos de silício

Souza, Éder Carlos Ferreira de
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Tese de Doutorado Formato: 110 f. : il.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Pós-graduação em Química - IQ; Nesta tese estudou-se a preparação de filmes finos de PZT não dopados e dopados com Nióbio, depositados sobre substratos de Pt/Ti/SiO2/Si para aplicações em memórias não voláteis de acesso randômico (NVRAM) e memórias ferroelétricas de acesso randômico (FeRAM). A dopagem dos filmes de PZT com Nióbio foi realizada visando obter valores ótimos nas propriedades ferroelétricas para a aplicação destes filmes como memórias ferroelétricas. Todavia, problemas como imprint, corrente de fuga e fadiga na polarização, estão presentes nos dispositivos de memórias contendo filmes de PZT sobre substratos platinizados. Para tentar resolver estes problemas, estudamos a produção de eletrodos de LaNiO3 depositados sobre substratos de SiO2/Si, para substituição dos substratos com eletrodos de Pt na preparação de filmes de PZT. Além disso, a dopagem do PZT com Nb levou a uma melhoria na resistência à fadiga em substratos platinizados. Os filmes foram preparados pelo método das soluções precursoras poliméricas. A influência do tratamento térmico...

Structural, microstructural, optical and electrical properties of (Pb,Ba,Sr)TiO3 films growth on conductive LaNiO3-coated LaAO(3)(100) and Pt/Ti/SiO2/Si substrates

Pontes, D. S. L.; Capeli, R. A.; Garzim, M. L.; Pontes, F. M.; Chiquito, A. J.; Longo, E.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 93-96
Português
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); The ferroelectric and dielectric properties of lead barium strontium titanate (PBST) thin films are investigated on different bottom electrode and substrate such as Pt, LaNiO3 and Pt/Ti/SiO2/Si, LaAlO3(100), respectively. X-ray diffraction results indicate that the PBST and LaNiO3 films on LaAlO3(100) single crystal substrate are highly (100)-oriented whereas the PBST films on Pt/Ti/SiO2/Si are polycrystalline. The results indicate strong effects of bottom electrode on the dielectric permittivity and tunability of the PBST films. The dielectric permittivity and tunability for the highly (100)-oriented PBST films on LaNiO3/LaAlO3(100) structure were 1238% and 65%, respectively, at 100 kHz, while PBST films prepared on PtiTi/SiO2/Si substrate, showed a dielectric permittivity of 520 and tunability of 47%, at 100 kHz. A slight shift of the phase transition temperature to lower temperatures was observed for highly (100)-oriented films in comparison to the polycrystalline films. Electrical properties should depend strongly on orientation and bottom electrode...

Structural, dielectric, ferroelectric and optical properties of PBCT, PBST and PCST complex thin films on LaNiO3 metallic conductive oxide layer coated Si substrates by the CSD technique

Pontes, D. S. L.; Chiquito, A. J.; Pontes, F. M.; Longo, E.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 33-39
Português
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 08/57150-6; Processo FAPESP: 11/20536-7; Processo FAPESP: 13/07296-2; Ferroelectric thin films and LaNiO3 (LNO) metallic conductive oxide thin films were prepared by a chemical solution deposition (CSD) method. PBCT60, PBST60 and PCST60 ferroelectric thin films were grown on different structures such as LNO/Si and single-crystalline quartz SiO2 (X-cut) substrates. The LNO layer acts as the bottom electrode for the electrical measurements. X-ray diffraction (XRD) analysis shows that LNO thin films on Si substrates and PBCT60, PBST60 and PCST60 thin films on LNO/Si structures are poly-crystalline with a moderate (110)-texture and a complete perovskite phase. LNO, PBCT60, PBST60 and PCST60 thin films have a continuous, dense and homogenous microstructure with a grain size on the order of 50-80 nm. Electrical resistivity-dependence temperature data confirm that LNO thin films display a good metallic character over a wide large range of temperatures. Optical characteristics of PBCT60, PBST60 and PCST60 thin films have also been investigated using ultraviolet-visible (UV-vis) spectroscopy in the wavelength range of 200-1100 nm. Ferroelectric thin films show a direct allowed optical transition with optical band gap values on the of order of 3.54...

Effect of the oxide loading on the surface characteristics of LaNio3 oxide coated electrodes

Soares, C. O.; Silva, R. A.; Carvalho, M. D.; Jorge, M. E. Melo; Gomes, A.; Rangel, C. M.; Pereira, M. I. da Silva
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em 12/12/2011 Português
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The LaNiO3 perovskite-type oxide is one of the most tested anode for the oxygen evolution reaction in alkaline solutions. It is well established that the oxide preparation conditions and the electrode fabrication are key factors to control the electrochemical behaviour of oxide coatings. In a previous work the authors studied the influence of preparation conditions of the oxide and support type on the electrochemical behaviour of Ni foam coated LaNiO3 electrodes. Ni foam was selected as support due to its unique characteristics namely low contact resistance between the oxide and support, possibility of high metal oxide loadings and dimensional stability [1]. No studies were performed, concerning the influence of the oxide loading. Studies performed by Singh et al. on LaNiO3 coatings on Ni foil supports have shown that the electrode roughness factor increased with increase in oxide loading at the beginning and finally attained a constant value around 0.03 g cm-2 [2]. The present work reports on the study of the dependence of roughness factor (Rf) and morphology factor (φ) on the oxide loading for Ni foam coated LaNiO3 electrodes with loadings varying between 0.02 and 0.14 g cm-2. Cyclic voltammetry and electrochemical impedance spectroscopy were used to evaluate the Rf and φ values...

Oxide loading effect on the electrochemical performance of LaNiO3 coatings in alkaline media

Soares, C. O.; Silva, R. A.; Carvalho, M. D.; Jorge, M. E. Melo; Gomes, A.; Rangel, C. M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2013 Português
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LaNiO3 film electrodes were prepared by brush painting using nickel-foam supports in order to increase its surface area available for electrochemical reactions. Loadings varying between 20 and 140 mg cm-2 were tested. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to evaluate the coatings roughness (Rf) and morphology (f) factors, complemented by optical microscopy observations. The values obtained from the two methods are in excellent agreement. The Rf values, ranging from 848 ± 50 to 4260 ± 60, are within the highest in the open literature. A simulation, of the effect of the oxide loading on the coatings Rf values, was performed using just the experimental values of the roughness factors for oxide free foam and pelleted electrodes. It was found that the increase of oxide loading causes a quasi linear increase of the electrodes active surface area. Simulated values were in excellent agreement with the experimental roughness factors and pore resistances obtained by CV and EIS. The electrodes were tested for oxygen evolution.

LaNiO3-based catalyst in gas diffusion electrodes: activity and stability for oxigen reactions

Silva, R. A.; Soares, C. O.; Carvalho, M. D.; Jorge, M. E. Melo; Gomes, A.; Rangel, C. M.; Pereira, M. I. da Silva
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 Português
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Perovskite-type oxides are potential catalysts for next generation of regenerative fuel cells. In particular, LaNiO3 has been recognised as one of the most promising oxygen electrodes. In this work LaNiO3 perovskite-type oxides, prepared by a self-combustion method [1, 2], have been used for the preparation of porous gas-diffusion electrodes (GDE). Electrodes were prepared on Toray carbon paper (CP) substrates, consisting of a diffusion layer, a catalyst layer and a Nafion® layer. The gas diffusion layers were prepared using Vulcan XC-72R. The catalyst ink was prepared by suspending the material in isopropanol, stirring the mixture in an ultrasonic bath to thoroughly disperse it. Ink slurries were also pasted onto glassy carbon discs and used as working electrodes for full kinetic studies at potential domains for the oxygen reduction (ORR) and oxygen evolution (OER) reactions. A systematic study on the effect of the oxide loading (OL) on the electrodes surface area was done by cyclic voltammetry. It was found a quasi linear variation between the electrodes surface area and the oxide loading. Roughness values varying from 106±3 to 307±6 were obtained for OL between 1 and 5 mg cm-2 respectively. The results show that the peak current density increases with the increasing on oxide loading as shown in Fig. 1. Higher current densities for ORR were obtained for the electrodes prepared using LaNiO3-based perovskite with partial substitution of Ni by Cu. Stability studies of the GDEs...

Síntese da perovsquita do tipo LaNiO3 através do método dos precursores quelantes usando EDTA: otimização do teor de agente quelante

Santos,Jose Carlos dos; Pedrosa,Anne Michelle Garrido; Mesquita,Maria Eliane; Souza,Marcelo José Barros de
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 Português
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The perovskites are strategic materials due their catalytic, electronic and magnetic properties. These properties are influenced by the calcination and synthesis conditions. In this work was carried out the synthesis of LaNiO3 perovskite-type by chelating precursor method using EDTA and also was studied the optimization of the EDTA content in the synthesis. The synthesized materials were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TG) and Infrared Spectroscopy (FTIR). In the optimization of the EDTA content the lowest ratio of metal / EDTA used was 1.0 / 0.1, where it was possible to obtain monophasic perovskite.

Synthesis of LaNiO3 perovskite by the modified proteic gel method and study of catalytic properties in the syngas production

Santos,José C.; Souza,Marcelo J. B.; Ruiz,Juan A. C.; Melo,Dulce M. A.; Mesquita,Maria E.; Pedrosa,Anne M. Garrido
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2012 Português
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This work describes a study on the synthesis of LaNiO3 perovskites via the modified proteic gel method, varying collagen content and on the catalytic activity of LaNiO3 and LaNiO3/Al2O3 in the syngas (CO + H2) production. X-ray diffraction patterns revealed the formation of perovskite structure in all samples prepared by proteic gel synthesis method, varying collagen content and after calcinations at 700 ºC for 2 h. LaNiO3/Al2O3 catalyst prepared by the impregnation method showed diffraction peaks due to the perovskite structure and to the support (Al2O3). This catalyst presented: specific surface of 46.1 m² g-1, two reduction peaks in the temperature programmed reduction (TPR) profile and 46% of methane conversion (by the partial oxidation of methane using oxygen) after 18 h of reaction.

Estudo da influência das condições de síntese do método dos precursores poliméricos na formação de perovsquitas do tipo LaNiO3

Alves,M. C.; Souza,S. O.; Santos,J. C.; Souza,M. J. B.; Pedrosa,A. M. G.
Fonte: Associação Brasileira de Cerâmica Publicador: Associação Brasileira de Cerâmica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2011 Português
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A perovsquita do tipo LaNiO3 é um material que exibe aplicações em diversas áreas como catálise, óptica, células a combustível de óxido sólido, etc.. Neste trabalho, a otimização da síntese de perovsquitas do tipo LaNiO3 foi feita pelo método dos precursores poliméricos, modificando as razões metal/ácido cítrico e etilenoglicol/ácido cítrico. Em geral, as propriedades destes materiais variam com a composição e com o método de síntese. Os materiais sintetizados foram caracterizados por difração de raios X, análise termogravimétrica e espectroscopia de infravermelho. As perovsquitas com razões metal/ácido cítrico (1,0/1,0) e etilenoglicol/ácido cítrico (60/40) apresentaram melhores resultados em relação à obtenção da fase perovsquita monofásica.

Synthesis and Characterization of LaNiO3, LaNi(1-x)Fe xO3 andLaNi(1-x)Co xO3 Perovskite Oxides for Catalysis Application

Lima,Sania Maria de; Assaf,José Mansur
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2002 Português
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Mixed metal oxides with perovskite-type structure show a great potential to be used in catalysis, electrocatalysis and electronic ceramics. Perovskites oxides catalysts with the composition LaNiO3, LaNi(1-x)Fe xO3 and LaNi(1-x)Co xO3 (x = 0.4 and 0.7) have been synthesized by the precipitation method to be used in the methane reforming to produce hydrogen and synthesis gas. The compounds were characterized by X-ray diffraction, thermogravimetric and differential thermal analysis, inductively coupled plasma atomic emission spectroscopy, surface area measurements, energy dispersive X-ray spectrometry coupled to scanning electron microscopy and temperature programmed reduction. The results showed that a suitable combination of the preparation method with calcination variables (time and temperature) could result in oxides with the desired structure and with important properties at the application point of view in heterogeneous catalysis.

Síntese e caracterização de catalisadores de LaNiO3 não suportados e suportados em Al2O3 e ZrO2 para a reforma a vapor do metano

Martinelli, Daniele de Macedo Henrique
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia de Materiais; Processamento de Materiais a partir do Pó; Polímeros e Compósitos; Processamento de Materiais a part Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia de Materiais; Processamento de Materiais a partir do Pó; Polímeros e Compósitos; Processamento de Materiais a part
Tipo: Dissertação Formato: application/pdf
Português
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Ionic oxides with ABO3 structure, where A represents a rare earth element or an alkaline metal and B is a transition metal from group VIII of the periodic table are potential catalysts for oxidation and good candidates for steam reforming reaction. Different methods have been considered for the synthesis of the oxide materials with perovskite structure to produce a high homogeneous material with low amount of impurities and low calcination temperatures. In the current work, oxides with the LaNiO3 formula had been synthesized using the method of the polymeric precursors. The thermal treatment of the materials took place at 300 ºC for 2h. The material supported in alumina and/or zirconia was calcined at 800 ºC temperature for 4h. The samples had been characterized by the following techniques: thermogravimetry; infrared spectroscopy; X-ray diffraction; specific surface area; distribution of particle size; scanning electron microscopy and thermo-programmed reduction. The steam reforming reaction was carried out in a pilot plant using reducing atmosphere in the reactor with a mixture of 10% H2-Argon, a mass about 5g of catalyst, flowing at 50 mL.min-1. The temperature range used was 50 - 1000 oC with a heating rate of 10 oC.min-1. A thermal conductivity detector was used to analyze the gas after the water trapping...

Avaliação de perovskitas LaNiO3 para produção de gás de síntese a partir da reforma seca do metano

Noronha, Fábio Bellot; Carvalho, Maria Jeanedite de Sousa; Neto, Raimundo C. Rabelo; Souza, Priscila M; Borges, Luiz Eduardo Pizarro
Fonte: Instituto Nacional de Tecnologia Publicador: Instituto Nacional de Tecnologia
Tipo: apresentação
Português
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16o CBCat Congresso Brasileiro de Catalise. Campos do Jordão/SP. 2011.; A emissão em larga escala de CO2 e CH4 está na origem do fenômeno de aquecimento global, através do efeito estufa. Por isso, processos como o de reforma seca do metano tem recebido grande atenção1. Diversos catalisadores a base de metais nobres suportados ou de Ni têm mostrado altas conversões e elevada seletividade para a reforma do CH4. Como o Ni apresenta um menor custo, muitos estudos se concentram nesse elemento. Entretanto, a sinterização das partículas de Ni e a deposição de carbono a altas temperaturas são os principais obstáculos dessa rota. Estruturas do tipo perovskitas (ABO3) tem se mostrado muito promissora como precursores catalíticos já que levam à formação de partículas metálicas pequenas, com alta dispersão, quando submetidos a processos de redução, o que inibe a formação de carbono2. O objetivo desse estudo é avaliar o desempenho do LaNiO3, preparados por diferentes métodos, na reforma seca do metano.

The LaNiO3 perovskite-type oxides for the production of hydrogen through steam reforming of ethanol. The effect of the preparation method

Noronha, Fábio Bellot; Silva, Adriana Maria da; Costa, Lídia Oazem de Oliveira da; Mattos, Lisiane Veiga; Lima, Sonia M. de; Reis, Andressa Andrade Alves da Silva
Fonte: Instituto Nacional de Tecnologia Publicador: Instituto Nacional de Tecnologia
Tipo: apresentação
Português
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Escócia; The perovskite-type oxide with general formula ABO3 is a promising material as catalyst for the ethanol conversion reactions to hydrogen. These mixed oxides are able to produce highly dispersed metallic particles upon reduction, which inhibits the formation of carbon [1]. Recently, we have studied the performance of LaNiO3 perovskite-type oxide precursor as a catalyst for both steam reforming (SR) and oxidative steam reforming (OSR) of ethanol [2]. Catalyst deactivation took place depending on the reaction conditions and it was attributed to the deposition of carbon on the surface of the catalyst. The aim of this work was to study the effect of the preparation method of LaNiO3 perovskite-type oxide precursor on catalyst stability during SR and OSR of ethanol.

Charge transfer and interfacial magnetism in (LaNiO3)n/(LaMnO3)2 superlattices

Hoffman, Jason; Tung, I. C.; Nelson-Cheeseman, Brittany; Liu, Ming; Freeland, John; Bhattacharya, Anand
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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(LaNiO3)n/(LaMnO3)2 superlattices were grown using ozone-assisted molecular beam epitaxy, where LaNiO3 is a paramagnetic metal and LaMnO3 is an antiferromagnetic insulator. The superlattices exhibit excellent crystallinity and interfacial roughness of less than 1 unit cell. X-ray spectroscopy and dichroism measurements indicate that electrons are transferred from the LaMnO3 to the LaNiO3, inducing magnetism in LaNiO3. Magnetotransport measurements reveal a transition from metallic to insulating behavior as the LaNiO3 layer thickness is reduced from 5 unit cells to 2 unit cells and suggest a modulated magnetic structure within LaNiO3.

Interfacial Ferromagnetism in LaNiO3/CaMnO3 Superlattices

Grutter, A. J.; Yang, H.; Kirby, B. J.; Fitzsimmons, M. R.; Aguiar, J. A.; Browning, N. D.; Jenkins, C. A.; Arenholz, E.; Mehta, V. V.; Alaan, U. S.; Suzuki, Y.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/07/2013 Português
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We observe interfacial ferromagnetism in superlattices of the paramagnetic metal LaNiO3 and the antiferromagnetic insulator CaMnO3. LaNiO3 exhibits a thickness dependent metal-insulator transition and we find the emergence of ferromagnetism to be coincident with the conducting state of LaNiO3. That is, only superlattices in which the LaNiO3 layers are metallic exhibit ferromagnetism. Using several magnetic probes, we have determined that the ferromagnetism arises in a single unit cell of CaMnO3 at the interface. Together these results suggest that ferromagnetism can be attributed to a double exchange interaction among Mn ions mediated by the adjacent itinerant metal.; Comment: Accepted for publication in Physical Review Letters (http://prl.aps.org/), copyright (2013) by the American Physical Society

Redox stability and bifunctionality of LaNiO3-based oxygen electrodes

Silva, R. A.; Soares, C. O.; Carvalho, M. D.; Jorge, M. E. Melo; Gomes, A.; Rangel, C. M.; Pereira, M. I. da Silva
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 Português
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One key issue in the development of Regenerative fuel cells (RFCs) is the availability of cheap, highly active electrocatalysts for both oxygen reduction and water oxidation. Perovskite-type oxides, with the general formula ABO3, are potential catalysts for next generation of regenerative fuel cells. In particular, LaNiO3 has been recognised as one of the most promising oxygen electrodes. In this work LaNiO3 perovskite-type oxides, prepared by a self-combustion method [1, 2], have been simultaneously optimized for activity and stability as an anode and cathode material for water oxidation and oxygen reduction reaction (ORR), respectively. Extremely high surface area has been measured by BET analysis with matching electrochemical activity estimated by cyclic voltammetry and electrochemical impedance spectroscopy. A full electrochemical study has been conducted in order to kinetically characterize the prepared electrodes in alkaline media, using a Ni foam and carbon paper as support material for the electrodes. For LaNiO3 deposits on Ni foam, low contact resistance between the oxide and support, possibility of high metal oxide loadings and dimensional stability were accomplished with remarkable stability in the region of oxygen evolution. For LaNiO3 deposits on carbon paper...

METHANE PARTIAL OXIDATION BY THE LATTICE OXYGEN OF THE LANIO3-D PEROVSKITE. A PULSE STUDY

Sierra Gallego,Germán; Batiot-Dupeyrat,Catherine; Mondragón,Fanor
Fonte: DYNA Publicador: DYNA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2010 Português
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LaNiO3 perovskite was prepared by the self-combustion method and tested as catalyst for CH4 activation using the oxygen lattice at 700°C and 800°C. Based on the non-stoichiometry experiments, the perovskite formula is written as La3+Ni3+0.37Ni2+0.63O2.68. When unreduced LaNiO3-d perovskite is used, only b-type oxygen species were responsible for the partial CH4 oxidation. Over non reduced perovskite high CH4 conversions to H2 and CO were obtained. CH4 conversion and H2, CO and CO2, selectivities under quasi-stationary conditions were 100%, 80%, 98% and 2 % respectively at 800°C. At the beginning of the reaction, a complete oxidation of methane to CO2 and H2O took place, whereas a partial oxidation to CO and H2 was observed after that period. In such conditions the H2/CO molar ratio obtained was 1.7, indicating a contribution of the parallel reverse water gas shift reaction

Improving Electrocatalytic Activity of LaNiO3 Films by Deposition on Foam Nickel Substrates

Soares,C.O.; Carvalho,M.D.; Jorge,M.E. Melo; Gomes,A.; Silva,R.A.; Rangel,C.M.; Pereira,M.I. da Silva
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2011 Português
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In this work LaNiO3 oxide was prepared by a self-combustion method using citric acid. The electrodes were obtained by coating a nickel foam support with the oxide suspension. Optical microscopy and cyclic voltammetry were used on the electrodes characterization. The evaluation of the electrodes electrocatalytic activity, towards the oxygen evolution reaction in alkaline medium, was performed by means of steady state measurements. The reaction follows a first order kinetics, with respect to OH- concentration, with Tafel slopes close to 40 mV, for low overpotentials. Based on the apparent and real current densities it was possible to conclude that the increase on the electrode activity, when compared with the published data, is mostly related to geometric factors. This fact has been associated with the high electrode/electrolyte contact area provided by the foam nickel substrate. Synergetic effects between the Ni foam and the perovskite oxide cannot be discarded.