Suchergebnisse

In order to understand the participation of electrical double layer and pseudocapacitance to the overall behavior of supercapacitors, a new approach to the analysis of the electrochemical data is proposed. Both the variation of the specific capacitance values and the dependence of these values with the operating voltage window (varying from 0–0.2 V to 0–1 V) were evaluated and used to quantify the contribution arising from each mechanism of energy storage to the total capacitance of the system. The suitability of the methodology here proposed was tested in various carbon materials (multiwalled carbon nanotubes, a carbon aerogel and two activated carbons), different both in nature and physicochemical characteristics. For all of the carbons studied, the capacitance with an exclusive faradic and non-faradic origin was quantified. Whereas some of the carbons studied showed a behavior close to an ideal electrical double layer capacitor (EDLC) with virtually no pseudocapacitance contribution (case of the carbon nanotubes), others presented up to a 40% of pseudocapacitance contribution (case of KOH-activated carbon). ; Authors acknowledge financial support from the MICINN and European Union (Project MAT2010-20601-C02-01). Silvia Roldán thanks MICINN for a FPI predoctoral research grant. ; Peer reviewed

The energy efficiency of vanadium redox flow batteries (VRFB) greatly depends on the electrochemical performance of the electrodes that constitute these devices, so it is essential to develop more efficient electrode materials with optimized structure and physicochemical properties. Carbon-based felts are commonly used as electrodes in such devices due to their high chemical stability in acid media, high electrical conductivity and their three-dimensional structure. However, they show low reversibility and electrocatalytic activity, especially for the VO2+ / VO2+ redox couple. In the quest for improving the electrochemical behaviour of carbon-based felts, it has been proposed to modify them with functionalized carbon nanotubes or graphene oxide by electrophoretic deposition. To elucidate if the improvements achieved on these electrodes can be really ascribed to the presence of the carbon nanomaterials or to the oxidation undergone by the fibers during this treatment, the electro-oxidation of a pristine rayon-based graphitized carbon felt was performed in parallel. The electro-oxidized felt exhibits the best behaviour, suggesting that the improved performance obtained for the electrodes modified with nanocarbons are mainly influenced by the oxidation of the fibers. ; The authors would like to acknowledge the support from the Spanish Research Agency AEI/PID2019-104028RB-100, the Principality of Asturias Research Council (PCTI) through EU (FEDER) IDI/2018/000121 and CSIC (PTI FlowBat: 201980E101). V.G Rocha would like to thank the Spanish Government (Ramón y Cajal fellowship, RYC2018-024404-I). ; Peer reviewed

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 reviewed

The transformation of anthracene oil into pitch is a feasible procedure for obtaining pitches with binder and impregnating characteristics. Moreover, their high aromaticity, total absence of solid particles and good fluidity make anthracene oil-based pitches interesting precursors for graphitizable carbon materials (e.g., carbon fibres, synthetic graphites). To prepare this kind of material the formation of mesophase in necessary during any one of the processing steps. This work deals with the preparation of mesophase from anthracene oil derivatives by controlled thermal treatment and subsequent sedimentation. ; The European Union (Project Ref. RFC-PR04001) and FICYT (Project Ref. PC-04-13. The Spanish Science and Education Ministry (Ministerio de Educación y Ciencia), "Juan de la Cierva". The Spanish Scientific Council for Research (CSIC), I3P ; Peer reviewed

Enhanced SO2 adsorption of activated carbon fibers is obtained by tailoring a specific micro-mesoporous structure in the fibers. This architecture is obtained via metal catalytic activation of the fibers with a novel precursor, cobalt naphthenate, which contrary to other precursors, also enhances spinnability and carbon fiber yield. In the SO2 oxidation, it is demonstrated that the combination of micropores and large mesopores is the main factor for an enhanced catalytic activity which is superior to that observed in other similar microporous activated carbon fibers. This provides an alternative way for the development of a new generation of catalytic material. ; The research leading to these results has received funding from the European Union's Research Fund for Coal and Steel research program under Grant Agreement number RFCR-CT-2009- 00004. Assistance from the Spanish Science and Innovation Ministry (CONSOLIDER INGENIO 2010, MAT2010-16194 and Ramon y Cajal research contract of Dr. P. Álvarez) is also acknowledged. ; Peer reviewed

[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 reviewed

The presence of nanomaterials in our everyday life is ever increasing, and so too are concerns about the possible health consequences of exposure to them. While evidence of their biological activity is growing, there is still scant knowledge of the epigenetic mechanisms that could be at play in these processes. Moreover, the great variability in the chemical and physical structures of these compounds handicaps the study of their possible health risks. Here we have synthesized reduced graphene oxide (rGO) through the thermal exfoliation/reduction of graphite oxide, and characterized the resulting material. We have then made use of Illumina's MethylationEPIC arrays and bisulphite pyrosequencing to analyse the genome-wide and global DNA methylation dynamics associated with the medium-term exposure of human lung epithelial cells to rGO at concentrations of 1 and 10 µg/mL. The results show no genome-wide or global DNA methylation changes associated with either condition. Our observations thus suggest that medium-term rGO exposure does not have significant effects on the DNA methylation patterns of human lung epithelial cells. ; This work has been financially supported by: The Plan Nacional de I+D+I co-funding FEDER (PI15/00892 and PI18/01527); the Government of the Principality of Asturias PCTI-Plan de Ciencia, Tecnología e Innovación de Asturias co-funding 2018-2022/FEDER (IDI/2018/146 and IDI/2018/121); AECC (PROYE18061FERN); FGCSIC (0348_CIE_6_E); IUOPA-ISPA-FINBA (The IUOPA is supported by the Obra Social Cajastur-Liberbank, Spain); A.F. Fernández is supported by a Miguel Servet II fellowship (contract CPII16/00007); R.F. Pérez is supported by ISPA-FINBA. ; Peer reviewed