Supercapacitor modified with methylene blue as redox active electrolyte

MWCNT-based supercapacitors (SC) containing methylene blue (MB) as redox active electrolyte were studied. MWCNTs were employed as model of electrode active material due to their ideal double-layer behavior facilitates the investigation of the energy storage mechanisms involved. MB led to a cell capacitance enhancement equal to 4.5 times the original cell capacitance of MWCNTs in sulphuric acid with a capacitance reduction of only 12% after 6000 charge–discharge cycles. The potential evolution of each electrode during galvanostatic cycling revealed that MB redox reaction develops in both electrodes simultaneously in the voltage range of 0–0.104 V and that this is the main cause of cell capacitance enhancement. Beyond this voltage range, the Faradaic contribution from the MB redox reaction decreases because the anode behaves as a capacitative electrode with a rather reduced charge-capacity due to the small surface area of MWCNTs. By means of a modified assembly composed of a Nafion membrane and MB and sulfuric acid solutions located in the cathode and anode compartments, respectively, it was demonstrated the limiting role of the capacitative electrode in the cell charge-capacity in this type of hybrid devices.The authors acknowledge the financial support of the MICINN (Project MAT2010-20601-C02-01). Silvia Roldán thanks MICINN for a FPI predoctoral research grant.Peer reviewe

High dielectric constant in Barium titanate-graphene composites around the percolation threshold

Resumen del trabajo presentado a la 14th International Conference of the European Ceramic Society, celebrada en Toledo (España) del 21 al 25 junio de 2015.Peer Reviewe

Evaluating capacitive deionization for water desalination by direct determination of chloride ions

Ionic conductivity and capacitance measurements are widely used methods for evaluating the desalination efficiency in capacity deionization processes. In this study, these methods are revised and several problems associated to them are identified and evaluated. Furthermore, a new method based on the determination of the chloride ion concentration by means of a chloride selective electrode is proposed as a more reliable alternative for evaluating the desalination performance in these systems. This method has been shown not only to be precise in a wide range of salt concentrations but also to be independent of pH, one of the main limitations of the determinations based on ionic conductivity measurements.The authors thank MICINN and the European Union (project MAT2010-20601-C02-01) for the financial support provided. Patricia Díaz thanks MICINN for a FPI predoctoral research grant (FPI: BES-2011-045394).Peer reviewe

Método de obtención de oxido de material pregrafítico, oxido de grafeno o grafeno a partir de materiales pregrafíticos y productos obtenidos por dicho método

Método de obtención de óxido de material pregrafítico, óxido de grafeno o grafeno a partir de materiales pregrafíticos y productos obtenidos por dicho método. Método de obtención de un producto seleccionado del grupo que consiste en óxido de material pregrafítico, óxido de grafeno y grafeno, caracterizado porque comprende transformar al menos un material pregrafítico en el producto sin tratamiento de grafitización. Preferiblemente, el material pregrafítico es coque (comercial o preparado a partir de breas, tanto de petróleo como de carbón o sintéticas)Peer reviewedConsejo Superior de Investigaciones CientíficasB1 Patente sin examen previ

Comparison between electrochemical capacitors based on NaOH and KOH activated carbons

This work describes the chemical activation of a coke using two different activating agents to investigate their behavior as electrodes in supercapacitors. A coke was chemically activated with two hydroxides (KOH and NaOH) under nitrogen flow, at a constant mass hydroxide/coke ratio of 2 and temperatures of 600, 650, and 700 °C. All of the samples were characterized in terms of porosity by N2 sorption at 77 K, surface chemistry by temperature-programmed desorption (TPD), and electrical conductivity. Their electrochemical behavior as electric double-layer capacitors was determined using galvanostatic, voltammetric, and impedance spectroscopy techniques in an aqueous medium with 1 M H2SO4 as the electrolyte. Large differences in capacitive behavior with the increase in the current density were found between the two series of activated samples. The different trends were correlated with the results obtained from the TPD analysis of the CO-type oxygen groups. It was found that these oxygen groups make a positive contribution to capacitance, finding a good correlation between the specific capacitance values, and the amount of these oxygen groups was found for both series.This work was supported by the MICIN (Project MAT2007-61467).Peer reviewe

Graphene materials with different structures prepared from the same graphite by the Hummers and Brodie methods

[EN] Graphene materials containing different functional groups were prepared from a natural graphite, by means of two different oxidation methods (Hummers and Brodie). It was observed that the differences in the structure of the resultant graphite oxides (GOs) greatly affect the structure of the graphenes resulting from their thermal exfoliation/reduction. Although the oxidation of the graphite was more effective with the modified Hummers method than with Brodie’s method (C/O of 1.8 vs 2.9, as determined by XPS), the former generated a lower residual oxygen content after thermal exfoliation/reduction and a better reconstruction of the 2D graphene structure (with fewer defects). This is explained by the presence of conjugated epoxy and hydroxyl groups in the GO obtained by Brodie’s method, which upon thermal treatment, lead to the incorporation of oxygen into the carbon lattice preventing its complete restoration. Additionally, graphene materials obtained with Brodie’s method exhibit, in general, smaller sheet size and larger surface area.The authors thank MICINN and European Union (CONSOLIDER INGENIO 2010, Ref. CSD2009-00050, MAT2010-16194) for their financial support. Dr. Patricia Alvarez thanks MICINN for her Ramon y Cajal contract.Peer reviewe

Waste-polystyrene foams-derived magnetic carbon material for adsorption and redox supercapacitor applications

The current impact of plastic waste on the environment and nature pushes for coming up with methods for their efficient reuse and recycle. Expanded polystyrene waste, massively produced worldwide, is presented in this work as a novel precursor of magnetic activated carbons (MAC) for the first time. A simple methodology based on the impregnation of EPS samples with Fe3+ in solution, followed by pyrolysis under Ar pressure and chemical activation is proposed. The as-prepared carbonaceous magnetic materials present nanometric phases of Fe0, Fe3C, and Fe3O4, and showed high specific surface area (672 m2 g−1) and total pore volume (0.35 cm3 g−1), one of the highest found in the carbonaceous magnetic materials literature. Their excellent textural, chemical and electrical properties, combined with the possibility of magnetically collection and regeneration after operation guaranteed an excellent performance of MAC in two different applications: as adsorbents of organic contaminants and as electrodes of redox supercapacitors.The authors would like to thank the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) for the financial support. P.F.R. Ortega acknowledges the FAPEMIG (DOF nº. 2720262/2018). The authors are also grateful to Rede Mineira de Química. R.L. Lavall is recipient of fellowship from CNPq (grant number 313304/2017-3). N. C. F. Machado, K. H. A. Mendes, and L. A. M. de Jesus would like to thank CEFET-MG and FAPEMIG for scholarships receivedPeer reviewe

Medio ambiente, sociedad, ética, auditoría y educación: reflexiones desde la disciplina contable.

Los servicios y desarrollos tecnológicos en todos los sectores económicos, al igual que la actualidad social, educativa, ambiental y agropecuaria en el mundo, constituyen oportunidades para que los contadores públicos se alejen de los procesos netamente manuales, y se acerquen al desarrollo de actividades que agreguen mayor valor a las unidades económicas en las cuales se desempeñan profesionalmente; en consecuencia, la academia recibe en la misma dimensión retos importantes que conllevan revisar y actualizar constantemente los contenidos, medios y escenarios educativos, a través de los cuales se cumple con la misión de formar contadores públicos idóneos para la sociedad. El programa de Contaduría Pública de la Corporación Universitaria Minuto de Dios – UNIMINUTO, UVD, consiente de la responsabilidad que tiene al ser uno de los programas con mayor número de estudiantes actualmente en Colombia, ha cimentado a lo largo de sus primeros ocho años bases adecuadas y orientadas a constituir una comunidad académica reconocida por sus aportes alternativos a la profesión y a la industria contable en general. El libro Medio ambiente, sociedad, ética, auditoría y educación en su segunda versión es una muestra de cómo el III Encuentro Nacional y II Internacional de Investigación Contable UNIMINUTO UVD, llevado a cabo en Bogotá en Octubre del 2018, se convirtió en un espacio extraordinario en el que se reunieron representantes de los veintiún lugares de oferta del programa de Contaduría Pública UNIMINUTO UVD, para compartir los avances de los proyectos que se tejen diariamente en diferentes lugares del territorio nacional, y que hacen parte integral de las cuatro sublíneas de investigación que se desarrollan al interior del programa y que se visualizan claramente lo largo del presente libro

Medio ambiente, sociedad, ética, auditoría y educación: reflexiones desde la disciplina contable.

Los servicios y desarrollos tecnológicos en todos los sectores económicos, al igual que la actualidad social, educativa, ambiental y agropecuaria en el mundo, constituyen oportunidades para que los contadores públicos se alejen de los procesos netamente manuales, y se acerquen al desarrollo de actividades que agreguen mayor valor a las unidades económicas en las cuales se desempeñan profesionalmente; en consecuencia, la academia recibe en la misma dimensión retos importantes que conllevan revisar y actualizar constantemente los contenidos, medios y escenarios educativos, a través de los cuales se cumple con la misión de formar contadores públicos idóneos para la sociedad. El programa de Contaduría Pública de la Corporación Universitaria Minuto de Dios – UNIMINUTO, UVD, consiente de la responsabilidad que tiene al ser uno de los programas con mayor número de estudiantes actualmente en Colombia, ha cimentado a lo largo de sus primeros ocho años bases adecuadas y orientadas a constituir una comunidad académica reconocida por sus aportes alternativos a la profesión y a la industria contable en general. El libro Medio ambiente, sociedad, ética, auditoría y educación en su segunda versión es una muestra de cómo el III Encuentro Nacional y II Internacional de Investigación Contable UNIMINUTO UVD, llevado a cabo en Bogotá en Octubre del 2018, se convirtió en un espacio extraordinario en el que se reunieron representantes de los veintiún lugares de oferta del programa de Contaduría Pública UNIMINUTO UVD, para compartir los avances de los proyectos que se tejen diariamente en diferentes lugares del territorio nacional, y que hacen parte integral de las cuatro sublíneas de investigación que se desarrollan al interior del programa y que se visualizan claramente lo largo del presente libro

Diseño para el desarrollo sustentable y la habitabilidad segura e incluyente

Este libro se divide en dos partes que permiten permear en el campo de la enseñanza del diseño; la primera se enfoca en temáticas que se desprenden del diseño en la educación para la sustentabilidad; en la segunda, se identifican las tendencias del diseño como un modo de verlo y sentirlo: va desde el diseño emocional hacia uno de conservación, reúso y reparación de objetos para reducir el consumo de recursos materiales