Search

In this work, the synthesis and catalytic activity of bimetallic Ag–Au nanoparticles (NPs) supported in TiO2 mesoporous thin films (MTFs) are presented. The composite materials were obtained through a two-step procedure, performed at room conditions. In the first step, Ag NPs were grown inside the MTFs by photoreduction. Then, a galvanic replacement reaction with Au was carried out, yielding the bimetallic NPs. The composites were characterized by UV/Vis spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray reflectometry (XRR), which show that the alloyed Ag–Au NPs are present inside the mesopores. Moreover, Ag and Au composition relationship can be controlled by adjusting the reaction times of the photoreduction and galvanic replacement reactions, respectively. Pores remain accessible after NPs synthesis, a feature that ensures their possible applications in any device that requires the contact between the NPs and the medium. Catalytic activity of the composites towards 4-nitrophenol reduction by sodium borohydride was evaluated. Although all the bimetallic systems exhibit improved catalytic properties in comparison with the monometallic Ag composite, the sample with lower Au/Ag relationship is the most effective. For the first time, to the best of our knowledge, bimetallic Au–Ag NPs are encapsulated inside mesoporous TiO2 films, paving the way towards a wide variety of applications. Fil: Coneo Rodríguez, Rusbel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Dispositivos y Sensores; Argentina Fil: Moya, Sergio Eduardo. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Departamento de Electrónica. Laboratorio de Instrumentación y Control; Argentina. CIC biomaGUNE; España Fil: Bruno, Mariano Martín. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; Argentina Fil: Angelome, Paula Cecilia. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; Argentina

This paper address the blocking of the electronic conductivity for a BaCe0.8Pr0.2O3-δ (BCP) material due to the addition of a BaCe0.4Zr0.4Y0.2O3-δ (BCZY) thin layer. Barium cerates (BCP and BCZY) show interesting features as electrolytes for Proton Conducting Solid Oxide Fuel Cells (PC-SOFC). BCP perovskite displays good mechanical properties associated to its sintering capability, typically proposed as a possible electrolyte. However, this compound shows poor CO2 tolerance above 500 °C and presents mixed conductivity under wet synthetic air. Protonic transport is the main feature of BCZY perovskite and it presents an excellent CO2 tolerance. However, the drawback of this compound is its high grain boundary resistance. In this work, a BCZY film was grown by Pulsed Laser Deposition (PLD) on BCP in order to block its electronic conductivity and improve CO2 tolerance. From the electrochemical characterization of materials, it is proposed that BCP dominates transport mechanisms on the BCZY/BCP bilayer membranes under wet synthetic air and wet diluted hydrogen. Our measurements confirm that the BCZY film blocks the electronic conductivity of BCP under wet synthetic air and protects it from CO2-containig atmospheres. Due to this set of properties, the BCZY/BCP bilayer membrane represents a possible candidate as electrolyte for PC-SOFC operating between 400 and 600 °C.

N-doped graphene hydrogels were prepared by crosslinking graphene oxide with ethylenediamine. These materials presented 10 at. % nitrogen, as determined by X-ray photoelectron spectroscopy. N-doped graphene was entangled within mesoporous matrices by diffusion of resorcinol-formaldehyde solutions throughout the hydrogels. According to nitrogen desorption isotherms, N-doping graphene slightly reduces the pore size and volume toward values closer to the graphene-free resins. The underlying graphene framework was observed within the amorphous porous carbon by transmission microscopy. These porous materials were impregnated with LiBH4 at 30, 50 and 70 vol %. Differential scanning calorimetry of the nanoconfined hydrides illustrates how N-doped matrix promotes a decrease in LiBH4 decomposition temperature, and this effect was quantified by volumetric studies. Powder diffraction revealed a peak at 12.6° attributed to the interaction of LiBH4 with the N-doped matrix. Owing to Yates analysis, N-doping lowers hydrogen release temperature by 10 °C, while at 325 °C the quantity released is increased by 1 wt %. This effect is more important than the diminution of pore size from 10 to 5 nm and compensates the presence of graphene. The benefit from N-doping is more remarkable for lower size of pores and higher LiBH4 filling, as illustrated by the proposed model.

Mixed ionic and electronic conductor (MIEC) oxides have been proposed as candidates to replace Ni/YSZ composites as anodes for Solid Oxide Fuel Cells (SOFC) due to their good stability under C-based fuels. Some MIECs have also demonstrated a good electro-catalytic activity both for oxygen reduction and hydrogen oxidation, making them suitable for symmetric configurations (S-SOFC). This approach presents remarkable advantages for reducing manufacturing and operational costs, as well as for extending the cell’s lifetime by reversing gas flows and thus partially reversing the negative effects of sulphur poisoning and carbon deposition that may happen during operation. Also, the catalytic activity of MIEC electrodes can be improved by functionalizing the oxide surface with active nanoparticles. In this work, we study the formation of Ni-Fe alloy nanoparticles by exsolution from a Sr0.93(Ti0.3Fe0.63Ni0.07)O3-δ (STFN) perovskite in reducing atmospheres, and also the process of reoxidation when the exsolved material is exposed to an oxidizing atmosphere. The initial Sr-deficient composition was chosen to alleviate the segregation of Sr [1], which typically can occur in these materials. Exsolution has previously been reported to improve the electrochemical performance of STFN anodes [2], but the mechanisms underlying the exsolution process and the solid/gas interface are still not well understood. The possibility of using S-SOFC materials that undergo exsolution also raises the question of whether the material is regenerated during reoxidation. While oxidation-induced redissolution of exsolved nanoparticles has been observed for Fe-Co exsolution on La0.8Sr1.2Fe0.9Co0.1O4−δ perovskites [3], for the Ni-Fe exsolution in Sr2(Fe1.4Ni0.1Mo0.5)O6− δ, nanoparticles remained at the surface even after reoxidation [4]. The first case is a very interesting result to achieve larger cell lifetimes, and the latter case is interesting as it opens an additional route to increase the cathode performance. In fact, in ref. [5] Ni exsolution in SrTi0.1Fe0.85Ni0.05O3− δ is deliberately employed as design strategy, fully exploiting the non-reversibility of the exsolution of nanoparticles. However, it is not clear whether Ni-Fe nanoparticles oxidize to form a (Ni,Fe)Ox phase or if Fe is reincorporated into the lattice leaving only NiO particles at the surface. It is also not clear how Sr segregation is affected by the exsolution/reoxidation treatments, or how the reoxidized STFN perovskite is modified compared to the pristine sample. To address these questions directly, ambient pressure X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopy (AP-XPS and NEXAFS) is used to study the chemical structure of STFN in a complete redox cycle in-situ. Based on the measurements, we can provide insights into the chemical states of Fe and Ni and can differentiate the surface and bulk species for Sr and O in each stage of the cycle. We observe that Ni exsolves readily, but we also note that the amount of surface Fe0 increases with increasing H2 content in the reducing atmosphere; Fe0 also increases with the reduction time following an exponential trend until a plateau value is reached within ~1h. Further, we find a significant Sr segregation in reducing atmospheres, which we presume occurs to compensate for the B-site cation exsolution. The amount of Sr segregation remains constant in the nearest surface after reoxidation, but is partially reversed for larger penetration depths; there is also a rapid reversibility in the Fe oxidation state during reoxidation. These observations were complemented with transmission (TEM) and scanning electron microscopy (SEM) studies, with simultaneous energy dispersive spectroscopy (EDS) analysis. In conclusion, we propose a reoxidation-induced reconstruction which forms a Fe- and Sr-rich STF perovskite in the near-surface region, leaving the Ni segregated from the perovskite. Finally, we link the results to the electrochemical impedance spectroscopy (EIS) response of the STFN electrode, observing that this STFN-reoxidized sample shows a significant improvement in its cathode performance compared to the pristine STFN. [1] Fagg, D. P. et al, J. Eur. Ceram. Soc. 21, 1831–1835 (2001). [2] Zhu, T., Troiani, H. E., Mogni, L. V, Han, M. & Barnett, S. A. Joule 2, 478–496 (2018). [3] Zhou, J. et al. Chem. Mater. 28, 2981–2993 (2016). [4] Liu, T. et al. J. Mater. Chem. A 8, 582–591 (2020). [5] Yang, G., Zhou, W., Liu, M. & Shao, Z. ACS Appl. Mater. Interfaces 8, 35308-35314 (2016). Figure 1

The modification of surface composition after long-term operation is one of the most reported degradation mechanisms of (La,Sr)(Co,Fe)O3-δ (LSCFO) cathodes for Solid Oxide Fuel Cells (SOFCs). Nevertheless, its effect on the oxygen reduction reaction kinetics of porous LSCFO cathodes has not been yet reliably established. In this work, La- and Sr-enrichment at the LSCFO surface of porous cathodes has been induced after 50 h aging at 800 °C under air. Such cation redistribution can extend up to ∼400 nm depth under the LSCFO surface as detected by high resolution Scanning Transmission Electron Microscopy-Energy Dispersive Spectroscopy maps acquired inside the cathode pores. The observed surface chemical changes hamper the oxygen surface exchange reaction at the LSCFO/gas interface. Accordingly, a suitable Electrochemical Impedance Spectroscopy analysis revealed that the oxygen ion conductivity remains practically unaltered during the aging treatment while the oxygen surface exchange resistance increases up to 1.8 times. As a result, the cathode impedance response deteriorates within the 10–0.1 Hz frequency range during the aging treatment, resulting in a total cathode area specific resistance increase of 150%. The methodology adopted has demonstrated to be very valuable for studying the degradation of SOFC cathodes produced by the modification of surface composition.

In this work, we have studied La0.4Sr0.6Co0.8Fe0.2O3-δ/Ce0.8Gd0.2O2-δ/La0.4Sr0.6Co0.8Fe0.2O3-δ symmetrical cells containing Ce0.8Gd0.2O2-δ electrolytes synthetized with and without the addition of cobalt as sintering aid. Electrochemical impedance spectroscopy results indicate that both electrolyte and cathode impedance response are affected by the addition of Co to the electrolyte, despite using cathodes with similar nano/microstructure according to scanning electron microscopy observations. Transmission electron microscopy characterization revealed the formation of columnar structures at the cathode/electrolyte interface of the cell with Co-doped electrolyte. These columnar structures would negatively affect the cell performance hindering the diffusion of oxide ions from the cathode to the electrolyte.

Electrically conducting oxides have been proposed as alternatives to Ni-based cermet anodes for solid oxide fuel cells (SOFCs) to overcome issues such as coking and impurity poisoning, but their electrochemical performance is typically inferior to that of Ni-based cermets. Here we show that a new oxide composition, Sr0.95(Ti0.3Fe0.63Ni0.07)O3−δ, yields anode polarization resistance competitive with Ni cermets, and substantially better than that of the corresponding Ni-free compound, SrTi0.3Fe0.7O3−δ. Exposure to fuel results in exsolution and nucleation of Ni0.5Fe0.5 nanoparticles uniformly dispersed on the Ni-substituted perovskite surface, whereas no nanoparticles are observed on SrTi0.3Fe0.7O3−δ. A general thermodynamic model is developed that quantitatively predicts exsolved nanoparticle composition. The reduction in anode polarization resistance by the nanoparticles, by as much as 4 times, is most pronounced at cell operating temperatures below 800°C and low H2 partial pressures, suggesting that the nanoparticles improve performance by promoting H2 adsorption. Mixed conducting perovskite oxides are proposed as alternatives for solid oxide fuel cell anodes, and in situ metallic nanoparticle precipitation/exsolution is considered to improve their performance. However, understanding of exsolution is still lacking, such as the reason why specific cations exsolve from an oxide anode and what determines the exsolved phase composition under various anode conditions. Here we directly compare Sr(Ti,Fe)O3-based anodes with and without exsolved metallic nanoparticles, showing their impact on electrochemical characteristics especially under low anode hydrogen concentrations and low temperatures. Three different methods are used to quantitatively determine the composition of the exsolved (Ni,Fe) nanoparticles, and for the first time demonstrate that this can be achieved through thermogravimetric analysis. This work is the first to propose a detailed thermodynamic theory predicting the exsolved nanoparticle composition with successful experimental verification. Ni-Fe nanoparticles are observed to exsolve from Ni-substituted Sr0.95(Ti0.3Fe0.63Ni0.07)O3−δ anode. The exsolved nanoparticles act to enhance hydrogen dissociative adsorption, yielding much lower anode polarization resistance and higher cell performance, especially under low pH2 and temperatures, which is comparable with the current Ni-based cermets. Fil: Zhu, Tenglong. Northwestern University; Estados Unidos. Nanjing University of Science and Technology; China Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina Fil: Mogni, Liliana Verónica. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Han, Minfang. Tsinghua University; China Fil: Barnett, Scott A.. Northwestern University; Estados Unidos

A scalable, simple, robust and reproducible method is presented for the preparation of chemically homogeneous and ordered nanocrystalline and mesoporous Zr1-xCexO2 thin films. The method utilizes widely available commercial block copolymers as templates. We show how the preparation conditions, film compositions and thermal treatments determine the mesoporous and crystalline structure. Through the scanning of the synthetic process, it was possible to arrive at an optimized and very reproducible method which allows the preparation of high quality, transparent, nanocrystalline and ordered Zr1-xCexO2 mesoporous thin films with different compositions. Fil: Violi, Ianina Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina Fil: Luca, Vittorio. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Soldati, Analía Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina Fil: Soler Illia, Galo Juan de Avila Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; Argentina. Universidad Nacional de San Martin. Instituto de Nanosistemas; Argentina Fil: Zelcer, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina

Increasing SOFC electrode's surface area by modification of its microstructure is a well-known technique to reduce electrode polarization resistance. This is because reduced grain size and increased porosity promote diffusion and surface reactions, thus improving the electrode performance. However, a modified microstructure also causes differences in phase stability and in chemical compatibility with other SOFC materials. In this work, we study the effect of particle size in both the electrode performance and the phase stability under different fuel conditions and temperatures. SrTi0.3Fe0.7O3−δ (STF) is both prepared via solid state reaction (STF-SSR) and also by an alternative sol-gel route (STF-SG). The sintering temperature is reduced dramatically with the sol-gel method, hence inducing a higher porosity and a much smaller grain size. As particle size is reduced the stability under fuel conditions is also diminished, so decomposition induced by segregation of metallic Fe and SrO occurs at lower temperatures for the STF-SG sample. The stability under reducing conditions is studied by combined techniques such as TGA, TPR, XRD, SEM and TEM. Performance as anode and cathode is evaluated by Electrochemical Impedance Spectroscopy (EIS) by using electrolyte supported symmetrical cells. Prior to electrochemical experiments, the reactivity between La0.8Sr0.2Ga0.8Mg0.2O3 (LSGM) electrolyte and STF was studied, and also between STF and a Lanthanum Doped Ceria (LDC) buffer layer. It is seen that microstructure also plays a key role in the chemical stability of the STF. The impact of particle size reduction is higher for the anodic polarization resistance, which is reduced twice from STF-SSR to STF-SG.

The exsolution of metal cations from oxides under reducing fuel conditions results in the formation of surface metallic nanoparticles, which can reduce Solid Oxide Fuel Cell anode polarization resistance. However, the loss of the B-site cations shifts the stoichiometry of the perovskite oxide. Depending on the amount exsolved and the initial stoichiometry, the exsolution can presumably shift the oxide away from its single-phase perovskite region. Herein, the direct comparison of initially stoichiometric composition Sr(Ti0.3Fe0.63Ni0.07)O3-δ (STFN0) with initially A-site deficient Sr0.95(Ti0.3Fe0.63Ni0.07)O3-δ (STFN5) is conducted and reported. X-ray diffraction along with scanning and transmission electron microscopy analysis of the oxides, which are both reduced at 850 °C in H2/H2O/Ar, shows a similar size and density of exsolved Fe–Ni alloy nanoparticles, albeit with slightly different alloy compositions. Whereas the oxide phase in reduced STFN5 shows a well-ordered perovskite structure, the greater B-site deficiency in reduced STFN0 results in a highly disordered and strained structure. The electrochemical performance of STFN0 anodes is inferior to that of STFN5 anodes, and even worse than SrTi0.3Fe0.7O3-δ (Ni-free) anodes. It appears that an initial Sr deficiency is important to avoid a too-high B-site deficiency after exsolution, which distorts the perovskite structure and impairs electrochemical processes.

Here we investigate the electrochemical behavior of Pd/C synthesized by reduction with ethylene glycol in the presence of polyvinylpyrrolidone (EG-PVP). EG-PVP produces nanoparticles (NPs) with a narrow size distribution, but some of them remain covered by impurities after the synthesis. After successive voltammetric cycles, NPs become cleaner, but some agglomeration and structural modification occur; these effects affect the electrochemical behavior of Pd/C in different ways, so we used CO as a probe to better understand the processes taking place. CO stripping shows that the general features of the multiple oxidation peaks change with the number of cycles. Possibly, CO and OH from different NPs react when the particles agglomerate, contributing to CO stripping changes. Finally, different active areas are found when the charges involved in CO oxidation and PdO reduction are compared. Such differences are rationalized in terms of a balance between the increase of sites which promote the oxidation of CO and the loss of area provoked by the growing of the particles. Fil: Martins, Cauê A.. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Fernández, Pablo Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Troiani, Horacio E.. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Física de Metales; Argentina Fil: Martins, María Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Arenillas de la Puente, Ana. Instituto Nacional del Carbón; España Fil: Camara, Giuseppe A.. Universidade Federal do Mato Grosso do Sul; Brasil

Pure-phase La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM) nanocrystallites have been successfully synthesized by the combustion method, employing glycine as fuel and complexing agent, and ammonium nitrate as combustion trigger. A detailed morphological and structural characterization is performed, by using of X-ray diffraction, N2 physisorption and electron microscopy. The LSCM material consists in interconnected nanocrystallites (∼30 nm) forming a sponge-like structure with meso and macropores, being its specific surface area around 10 m2 g-1. Crystalline structural analyses show that the LSCM nanopowder has trigonal/rhombohedral symmetry in the R-3c space group. By employing the spin coating technique and quick-stuck thermal treatments of the ink-electrolyte, electrodes with different crystallite size (95, 160 and 325 nm) are built onto both sides of the La0.8Sr0.2Ga0.8Mg0.2O3-δ-disk electrolyte. To test the influence of the electrode crystallite size on the electrocatalytic behavior of the symmetrical cells, electrochemical impedance spectroscopy measurements at 800 ºC were performed. When the electrode crystallite size becomes smaller, the area specific resistance decreases from 3.6 to 1.31 Ω cm2 under 0.2O2-0.8Ar atmosphere, possibly due to the enlarging of the triple phase boundary, while this value increases from 7.04 to 13.78 Ω cm2 under 0.17H2-0.03H2O-0.8Ar atmosphere, probably due to thermodynamic instability of the LSCM nanocrystallites. Fil: Chanquia, Corina Mercedes. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Montenegro Hernandez, Alejandra. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Troiani, Horacio Esteban. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Física de Metales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Caneiro, Alberto. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Solid oxide fuel cell performance is usually limited by high cathodic area specific resistance (ASR) at intermediate temperatures (500-700°C). ASR can be decreased by reducing particle size to nanometer range. This improvement is usually ascribed to the area/volume ratio increase and a higher concentration of active sites for the oxygen reduction reaction (ORR). Nevertheless, this solely explanation seems not to be enough for explaining the high electrochemical performance of some nanostructured La0.4Sr0.6Co0.8Fe0.2O3-d cathodes previously reported (Baqué et al., Electrochemistry Comm. 10 (2008) 1905-1908). Accordingly, the ORR of these cathodes was studied by electrochemical impedance spectroscopy (EIS) under air and under pure oxygen within the 400-700°C range. The nanostructure was characterized even at atomic level by transmission electron microscopy (TEM), revealing that the cathode is composed of nanocrystals surrounded by zones with some degree of crystalline disorder. These results suggest that this kind of nanostructure facilitate the ORR in this compound. Fil: Baque, Laura Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Technical University Of Denmark; Dinamarca Fil: Soldati, Analía Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina Fil: Schreiber, Anja. Helmholtz Gemeinschaft; Alemania Fil: Caneiro, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina Fil: Serquis, Adriana Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina

Carbon supported Pt nanoparticles (NPs) have been prepared through polyols method using PVP. As observed with a large number of surfactants employed in NPs synthesis, it is very difficult to attain an efficient NPs cleaning, which is a fundamental requirement in catalysis researches. The aim of this paper was to obtain clean NPs, beginning by using “soft” methods, in order to keep unaltered both the NPs size and shape; however, an important surfactant remnant was observed. Consequently, it was performed an electrochemical cleaning through PVP and glycolate electro-oxidation, being accompanied with important perturbations of NPs atoms and dissolution and re-deposition of Pt. Finally, the performance of the catalyst towards the glycerol electro-oxidation reaction (GER), before and after the cleaning process was studied. In addition, we demonstrate how the impurities bring about poor reproducibility in this kind of experiments due to the fact that the cleaning process is occurring at the same time that the GER and because cleaning extent along cycles varies for each independent experiment. Fil: Fernández, Pablo Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; Argentina Fil: Ferreira, Dênis S.. Universidade Federal Do Mato Grosso Do Sul; Brasil Fil: Martins, Cauê A.. Universidade Federal Do Mato Grosso Do Sul; Brasil Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina Fil: Câmara, Giuseppe A.. Universidade Federal Do Mato Grosso Do Sul; Brasil Fil: Martins, María Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; Argentina

Gold nanoparticles (NP) were synthesized inside ordered mesoporous TiO2 thin films (MTTF) by stepwise reduction of AuCl4 − with NaBH4. This leads to an optical material (Au@TiO2) of interest for plasmonic applications. The films (pure titania or gold-titania nanocomposites) were thoroughly characterized by UV−visible and ellipsometry spectroscopies. The dielectric function of the MTTF, considered as the dielectric environment in which the NP are embedded, was acquired by ellipsometry and rationalized by the asymmetric Bruggeman model as an effective medium formed by the mixture of dense TiO2 and air. Nanocomposite Au@TiO2 systems present an isotropic dispersion of Au NP in the 5−8 nm range. The UV−visible spectra obtained with a low nanoparticle filling fraction of the pore volume (f NP < 2%) are accurately reproduced by both Maxwell−Garnett (MG) and Mie theories. Accurate and coincident values of f NP and NP size are obtained by this method. The dielectric function of Au NP used in this work was studied in detail; in particular, the interface damping parameter related to the NP/MTTF interface was determined by comparison with TEM microscopy. The potential of the ellipsometry technique to determine the material plasmonic response, and its correspondence with the UV−visible spectra, are discussed. This spectroscopy technique opens the possibility to study the plasmon response of the material to changes in the environment due to the presence of vapors, and other in situ experiments, as well as to provide nanostructural information of metallic nanoparticles (NP size, interparticle distance, number of NP) with well-defined spatial localization in a multilayered system. Fil: Sanchez, Veronica Muriel. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Martínez, Eduardo David. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Martinez Ricci, Maria Luz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Soler Illia, Galo Juan de Avila Arturo. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Nanoparticles (NPs) with magnetic properties based on magnetite (Fe3O4, MAG) modified with oleic acid (OA), chitosan (CS) and bovine serum albumin (BSA) have been prepared. A versatile method of synthesis was employed, involving two steps: (i) co-precipitation of MAG; and (ii) nanoprecipitation of macromolecules on as-formed MAG NPs. Experimental variables have been explored to determine the set of conditions that ensure suitable properties of NPs in terms of their size, functionality and magnetic properties. It was found that the presence of OA in Fe+2/Fe+3 solutions yields MAG NPs with lower aggregation levels, while increasing initial amounts of OA may change the capability of NPs to disperse in aqueous or organic media by modifying the stabilization mechanism. Incorporation of CS was verified through Fourier transform IR spectroscopy. This biopolymer stabilizes NPs by electrostatic repulsions leading to stable ferrofluids and minimal fraction of recoverable solid NPs. BSA was successfully added to NP formulations, increasing their functionality and probably their biocompatibility. In this case too stable ferrofluids were obtained, where BSA acts as a polyelectrolyte. From the proposed methodology it is possible to achieve a wide range of NPs magnetically active intended for several applications. The required properties may be obtained by varying experimental conditions. Fil: Nicolás, Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Planta Piloto de Ingeniería Química (i); Argentina. Universidad Nacional del Sur; Argentina Fil: Saleta, Martin Eduardo. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina Fil: Zysler, Roberto Daniel. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina Fil: Lassalle, Verónica Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto de Química del Sur; Argentina. Universidad Nacional del Sur; Argentina Fil: Ferreira, Maria Lujan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Planta Piloto de Ingeniería Química (i); Argentina. Universidad Nacional del Sur; Argentina

We present a crystallographic, morphologic and redox dynamic study on (60:40) NiO/Ce0.9Gd0.1O1.95 (NiO/GDC) cermets simulating Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC) anodes in situ conditions. We tested micro- and nanometer sized materials at 700ºC in three different atmospheres (5% H2, 5% O2 and 20% CH4). We used Dispersive X-ray Absorption Spectroscopy (DXAS) analysisat the Ce L3-edge and at the Ni K-edge to follow the metal´s oxidation states. A correlation between the catalytic/redox properties and the sample´s characteristics (microstructure, Ni distribution, etc.) was found, indicating that nanometric sized particles showed faster and higher reduction extents than micrometric particles of the same composition. Fil: Fernandez Zuvich, Afra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Larrondo, Susana Adelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Química. Laboratorio de Procesos Catalíticos; Argentina Fil: Saleta, Martin. Laboratório Nacional de Luz Síncrotron; Brasil Fil: Napolitano, Federico Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Caneiro, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Lamas, Diego Germán. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Arce, Mauricio Damián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Serquis, Adriana Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Soldati, Analía Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina

The co-condensation in situ of tetraethoxysilane (TEOS) and mercaptopropyltrimethoxysilane (MPTMS) using cetyltrimethylammonium bromide (CTAB) as a template results in the synthesis of multilayered mesoporous structured SiO2 colloids with “onion-like” chemical environments. Thiol groups were anchored to an inner selected SiO2 porous layer in a bilayered core shell particle producing different chemical regions inside the colloidal layered structure. X-Ray Photoelectron Spectroscopy (XPS) shows a preferential anchoring of the –SH groups in the double layer shell system, while porosimetry and simple chemical modifications confirm that pores are accessible. We can envision the synthesis of interesting colloidal objects with defined chemical environments with highly controlled properties.

Uniform polycrystalline SnO2 microtubes formed by sintered nanoparticles (fixed to a surface or in free standing form) were obtained with the infiltration technique using SnCl4 as precursor and a porous polycarbonate (PC) film as template. The advantage of this synthesis method was based on its simplicity, reproducibility, low cost, and the possible applicability to other complex oxides. The morphology and crystal structure of SnO2 tubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The crystalline sizes of the nanoparticles assembled in the tube walls obtained at 600 °C were in the range of 5–7 nm, calculated from both the XRD and the TEM data. The length of the microtubes fixed to a silicon nitride surface ranged between 2 and 7 μm. Sensors fabricated with this material showed unusual sensitivity to ethanol at room temperature and fast reversible response, as compared to those obtained by the deposition of metallic tin film and further oxidation (Rheotaxial Growth and Thermal Oxidation method).

This paper analyses the synergetic effect of the coupled addition of Co particles (Co, 5 wt%) and pure multi-walled carbon nanotubes (MWCNTs, 5 wt%) on hydrogen sorption kinetics of MgH2 (M). Experimental results show that MCo co-milled 50 h plus admixed MWCNTs for 5 h exhibits enhanced absorption/desorption performance, which remains stable after 15 hydrogen sorption cycles. About 6.5 wt% of hydrogen was absorbed after 100 s and desorbed in 85 min at 250 °C, being one of the best conditions reported for Mg-based composites. Furthermore, desorption temperature after cycling was reduced by 55 °C due to the introduction of Co, and 136 °C by the combined Co and MWCNT addition as compared to free MgH2. Activation energy analysis demonstrates that although the MWCNT addition has a slight influence on the energy barrier, the Co particles show a good catalytic effect. Moreover, the coupled effect of Co and MWCNTs reduces the activation energy and it is maintained after cycling. As a consequence of cycling, some nanograins of MgH2 appear covered with a thin external layer of amorphous carbon while some part of the MWCNTs remains intact in the material. An interpretation of the kinetics effect of Co particles and MWCNT coupled addition is proposed.

The preparation and study of quantum dots and quantum wires play a very important role in nanotechnology. In this particular study, we report on the uptake of silver by living alfalfa plants. X-ray absorption spectroscopy and transmission electron microscopy (TEM) studies corroborated silver metal uptake by alfalfa plants from a silver-rich solid medium and the subsequent formation of silver nanoparticles. Silver nanoparticle alignment, structure, and coalescence were observed using TEM with an atomic resolution analysis. Dark field image TEM showed the connection of silver nanoparticles of different sizes by possibly noncrystalline silver atomic wires. To our knowledge, this is the first report on the formation of silver nanoparticles by a living plant system.

The commercialization of Solid oxide fuel cells (SOFCs) is still hindered by their cost and long term degradation. One of the most common degradation mechanisms of La1-xSrxFe1-yCoyO3-d (LSCFO) cathodes reported in literature is element demixing. In this work, the degradation of LSCFO cathodes deposited on Ce1-xGdxO2-d electrolytes at 800°C in air for 50 h was investigated by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). EIS spectra from LSCFO cathodes present two contributions: one at high frequency and another at low frequency. The high frequency contribution remains invariable during the ageing treatment while the low frequency contribution continuously increases. The formation of small segregates was observed after the ageing treatment. Energy dispersive spectroscopy analysis reveals that these segregates were particularly poor in Sr. Fil: Baque, Laura Cecilia. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Soldati, Analía Leticia. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Serquis, Adriana Cristina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Metal-porous oxide nanocomposites present great interest in optical devices and heterogeneous catalysis. For these applications, particle shape and size control, as well as accessibility, are critical aspects. In this work, gold nanoparticles (NPs) were infiltrated into mesoporous TiO2 thin films (MTTF) by an impregnation-reduction method. In situ ellipsometry measurements were performed during thermal treatment to follow in real time the changes in the optical constants and thickness of the composites systems while being submitted to continuous heating at different rates, from room temperature up to 600 °C. Complementary characterization by UV–visible spectrophotometry, grazing incident wide angle scattering (GIWAXS), and X-ray reflectometry (XRR) were performed. TEM microscopy was used to analyze the morphological changes in the composite films after the thermal treatment. Our experiments demonstrate that particle coarsening starts at temperatures below 200 °C through the processes of ripening and particle migration, leading to changes in the particle size distribution (PSD) until a mechanical restriction, due to the porous geometry, induces a change of the particle shape from spherical to ellipsoidal. This results in an internal stress that swells the mesoporous film. The effect of the gold filling fraction and the heating ramp was analyzed. A mechanism based on the kinetics of particle migration and coalescence, through the modeling of the localized surface plasmon resonance under the dipolar approximation, is proposed to explain the changes in the optical properties of these composites materials and unravel the thermal activated processes occurring in metal crystallites supported on porous oxide frameworks. Fil: Martínez, Eduardo David. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina Fil: Cédric, Boissiere. College de France; Francia Fil: Grosso, David. College de France; Francia Fil: Sanchez, Clément. College de France; Francia Fil: Troiani, Horacio Esteban. Comision Nacional de Energia Atomica. Gerencia D/area de Energia Nuclear; Argentina Fil: Galo, J. A. A. Soler Illia. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina

Controlling the structures of supports and supported phases is important for catalytic applications where synergic effects can play a main role. In this context, we present versatile methods for suitable microstructurization of CeO2 support and improved dispersion of supported Pt crystallites in a Pt/CeO2 system for enhanced catalytic oxidation of CO. The physicochemical properties investigated using SEM, BET, visible Raman, H2-TPR and OSC measurements demonstrated the important role played by the precursor on the properties of CeO2. Further, 0.5 wt% Pt deposited over CeO2 via ethylene glycol assisted reduction (EGR) was found to be more advantageous than conventional impregnation (IMP) in producing very finely dispersed Pt particles that did not noticeably sinter even after thermal treatment at 500 ◦C for longer duration. H2-chemisorption and H2-TPR experiments further substantiated better Pt dispersion on CeO2 prepared in the presence of Cl− ions regardless of the method employed, thus suggesting a strong microstructural effect of support during growth and anti-sintering activity of Pt crystallites. The CO oxidation activity additionally demonstrates that samples prepared by EGR method show remarkably better performance (100% conversion in

We report the synthesis of rare-earth manganese-oxide-based nanotubes. The pore wetting technique was used to obtain structures of nominal composition La0.325Pr0.300Ca0.375MnO3 with 800 nm external diameter, 4000 nm length, and wall thickness below 100 nm exhibiting magnetic and magnetoresistive behavior below 200 K, including nonvolatile memory. Walls are found to be formed by small crystals of approximately 20 nm. Structures obtained using different diameter of pores, as small as 100 nm, have a similar aspect ratio. Results show the realization of nanotubes of manganites exhibiting intrinsic phase separation.

Nanopowders of La0.75Sr0.25Cr0.5Mn0.5O3−δ (LSCM) perovskite-type oxide, potential electrode material for symmetrical solid oxide fuel cell (S-SOFC), have been successfully prepared by the solution combustion method employing glycine as complexing agent and fuel. Several glycine-to-nitrates molar ratios were investigated. A detailed morphological and structural characterization was performed, employing X-ray diffraction, N2 physisorption, and electron microscopy (scanning and transmission). The as-synthesized LSCM nanopowders consist of interconnected nanoparticles forming a sponge-like structure with typical meso- and macropores. For glycine-to-nitrates molar ratios above stoichiometric molar ratio, a high proportion of well-crystallized LSCM phase was obtained. An increase of glycine content in the initial synthesis gel, decreases the average nanoparticles size from ~20 to ~6 nm, narrows the distribution crystallite size, and increases the specific surface area of the LSCM nanopowders from ~14 to ~30 m2/g. The evolution of crystalline phases of the as-synthesized LSCM nanopowders after calcination at various temperatures was studied: pure-phase La0.75Sr0.25Cr0.5Mn0.5O3−δ perovskites with particle-size distribution between 100 and 300 nm, have been obtained after calcination at 1,000 °C for 6 h. The crystalline structural analyses showed that the LSCM nanocrystallites have trigonal/rhombohedral symmetry in the R-3c space group. These final LSCM nanopowders present microstructures with low densification and open porosity but probably with sufficient integrity to enable them to be used as efficient electrodes in S-SOFC.

M/CeO2/YSZ nanocomposites (M = Ru, Pd, Ag) were prepared by successive impregnation and tested in the ethanol steam reforming (ESR). Ru/CeO2/YSZ demonstrated good activity and stability under reaction conditions. Pd/CeO2/YSZ shows good initial activity but suffers of significant deactivation while the performances of the Ag-based sample were rather poor. A plethora of different structural (Powder XRD), microstructural (HR-TEM), morphological (surface area, CO chemisorption) and thermal analysis characterization techniques were used to evidence the modification of the samples induced by prolonged exposure to the reaction mixture. The promising performances of Ru/CeO2/YSZ were associated to the combination of the positive action of the metal selectivity to syn-gas and of CeO2 in metal dispersion stabilization and coke deactivation prevention. (C) 2011 Elsevier B.V. All rights reserved.

The synthesis method for obtaining sub-micrometric structures of rare earth manganese-based mixed oxide compounds is described. Pore wetting of porous polycarbonate templates with the liquid precursor was followed by a two-stage thermal treatment to obtain single phase La0.325Pr0.300Ca0.375MnO3 hollow and solid structures, with external diameter determined by the sacrificial template pore size. The first thermal stage, a microwave assisted denitration process, determines the shape of the structures. The second treatment, performed at 1073 K, allows to obtain the crystallographic structure of the compound. A variety of techniques (scanning and transmission electron microscopy, scanning probe microscopy) allowed to fully characterize the microstructure and morphology of these self-standing manganite nanostructures. For 1 mum pore size templates we obtained tubes, with external diameter around 800 nm and wall thickness around 150 nm; densely packed nanoparticles sized 20-50 nm are the building blocks of the walls. For pore size below 0. 1 mum, solid nanowires were obtained, the size of constituent crystallites being around 10 nm. Overall obtained material exhibits ferromagnetic ordering below 200 K.

La1-xSrxCo1-yFeyO3-? oxides are good candidates for solid oxide fuel cell (SOFC) cathodes because these materials present high ionic and electronic conductivity, and compatibility with Cerium Gadolinium Oxide (CGO) electrolytes allowing a lower operation temperature. In this work, we report the synthesis of La0.4Sr0.6Co0.8Fe0.2O3-? (LSCF) nanotubes prepared by a porous polycarbonate membrane approach, obtaining different microstructures depending on sintering conditions. The structure and morphology of the nanotubes and deposited films were characterized by X-ray diffraction, transmission and scanning microscopy. Finally, we obtained nanostructured films of vertically aligned LSCF tubes deposited over the whole surface of CGO pellets with diameter up to 2.5cm in a direct and single step process.