Staff directory Dilson Juan Innocente

Dilson Juan Innocente

Research Assistant
dilson.juan(ELIMINAR)@icn2.cat
Theory and Simulation

Publications

2021

  • Localized electronic vacancy level and its effect on the properties of doped manganites

    Juan D., Pruneda M., Ferrari V. Scientific Reports; 11 (1, 6706) 2021. 10.1038/s41598-021-85945-5. IF: 3.998

    Oxygen vacancies are common to most metal oxides and usually play a crucial role in determining the properties of the host material. In this work, we perform ab initio calculations to study the influence of vacancies in doped manganites La (1 - x)Sr xMnO 3, varying both the vacancy concentration and the chemical composition within the ferromagnetic-metallic range (0.2<x<0.5). We find that oxygen vacancies give rise to a localized electronic level and analyse the effects that the possible occupation of this defect state can have on the physical properties of the host. In particular, we observe a substantial reduction of the exchange energy that favors spin-flipped configurations (local antiferromagnetism), which correlate with the weakening of the double-exchange interaction, the deterioration of the metallicity, and the degradation of ferromagnetism in reduced samples. In agreement with previous studies, vacancies give rise to a lattice expansion when the defect level is unoccupied. However, our calculations suggest that under low Sr concentrations the defect level can be populated, which conversely results in a local reduction of the lattice parameter. Although the exact energy position of this defect level is sensitive to the details of the electronic interactions, we argue that it is not far from the Fermi energy for optimally doped manganites (x∼1/3), and thus its occupation could be tuned by controlling the number of available electrons, either with chemical doping or gating. Our results could have important implications for engineering the electronic properties of thin films in oxide compounds. © 2021, The Author(s).


2017

  • Electrochemical behavior of nanostructured La0.8Sr0.2MnO3 as cathodes for solid oxide fuel cells

    Sacanell J., Sánchez J.H., Rubio Lopez A.E., Martinelli H., Siepe J., Leyva A.G., Ferrari V.P., Pruneda M., Juan D., Lamas D.G. ECS Transactions; 78 (1): 667 - 675. 2017. 10.1149/07801.0667ecst. IF: 0.000

    La0.8Sr0.2MnO3 (LSM) is one of the most commonly used cathodes in Solid Oxide Fuel Cells (SOFC). In spite of the fact that nanostructured cathodes are expected to display improved performance, the high operating temperature (∼ 1000°C) of LSM-based SOFCs hinders their stability. In the present work, we have developed nanostructured cathodes prepared from LSM nanotubes of enhanced performance, allowing its use at lower temperatures (∼ 800°C). We observed that our cathodes have qualitative improvements compared with microstructured materials: firstly, the diffusion in the gas phase is optimized to a negligible level and secondly, evidence of ionic conduction is found, which is extremely rare in LSM cathodes. We propose that this important change in the electrochemical properties is due to the nanostructuration of the cathode and deserves further attention, including the exploration of other materials. © The Electrochemical Society.


  • Oxygen Reduction Mechanisms in Nanostructured La0.8Sr0.2MnO3 Cathodes for Solid Oxide Fuel Cells

    Sacanell J., Hernández Sánchez J., Rubio López A.E., Martinelli H., Siepe J., Leyva A.G., Ferrari V., Juan D., Pruneda M., Mejía Gómez A., Lamas D.G. Journal of Physical Chemistry C; 121 (12): 6533 - 6539. 2017. 10.1021/acs.jpcc.7b00627. IF: 4.536

    In this work we outline the mechanisms contributing to the oxygen reduction reaction in nanostructured cathodes of La0.8Sr0.2MnO3 (LSM) for Solid Oxide Fuel Cells (SOFC). These cathodes, developed from LSM nanostructured tubes, can be used at lower temperatures compared to microstructured ones, and this is a crucial fact to avoid the degradation of the fuel cell components. This reduction of the operating temperatures stems mainly from two factors: (i) the appearance of significant oxide ion diffusion through the cathode material in which the nanostructure plays a key role and (ii) an optimized gas phase diffusion of oxygen through the porous structure of the cathode, which becomes negligible. A detailed analysis of our Electrochemical Impedance Spectroscopy supported by first-principles calculations point toward an improved overall cathodic performance driven by a fast transport of oxide ions through the cathode surface. (Figure Presented). © 2017 American Chemical Society.