Characterization of activated carbon fiber/polyaniline materials by position-resolved microbeam small-angle X-ray scattering

Activated carbon fiber (ACF)/polyaniline (PANI) materials have been prepared using two different methods, viz. chemical and electrochemical polymerization. Electrochemical characterization of both materials shows that the electrodes with polyaniline have a higher capacitance than does a pristine porous carbon electrode. To analyze the distribution of PANI within the ACF, characterization by position-resolved microbeam small-angle X-ray scattering (μSAXS) has been carried out. μSAXS results obtained with a single ACF indicate that, for the experimental conditions used, a PANI coating is formed inside the micropores and that it is higher in the external regions of the ACF than in the core. Additionally, it seems that the penetration of PANI inside the fibers occurs in a larger extent for the chemical polymerization or, in other words, for the electrochemically polymerized sample there is a slightly larger accumulation of PANI in the external regions of the ACF.Fil: Salinas-Torres, D.. Universida de Alicante; EspañaFil: Sieben, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Lozano-Castelló, D.. Universida de Alicante; EspañaFil: Morallón, E.. Universida de Alicante; EspañaFil: Burghammer, M.. EuropeanSynchrotronRadiationFacility; FranciaFil: Riekel, C.. EuropeanSynchrotronRadiationFacility; FranciaFil: Cazorla Amorós, Diego. Universida de Alicante; Españ

Mesoscopic effects in an agent-based bargaining model in regular lattices

The effect of spatial structure has been proved very relevant in repeated games. In this work we propose an agent based model where a fixed finite population of tagged agents play iteratively the Nash demand game in a regular lattice. The model extends the multiagent bargaining model by Axtell, Epstein and Young [1] modifying the assumption of global interaction. Each agent is endowed with a memory and plays the best reply against the opponent’s most frequent demand. We focus our analysis on the transient dynamics of the system, studying by computer simulation the set of states in which the system spends a considerable fraction of the time. The results show that all the possible persistent regimes in the global interaction model can also be observed in this spatial version. We also find that the mesoscopic properties of the interaction networks that the spatial distribution induces in the model have a significant impact on the diffusion of strategies, and can lead to new persistent regimes different from those found in previous research. In particular, community structure in the intratype interaction networks may cause that communities reach different persistent regimes as a consequence of the hindering diffusion effect of fluctuating agents at their borders.Spanish Ministry of Science and Innovation, references TIN2008-06464-C03-02 and CSD2010-00034 (CONSOLIDER-INGENIO 2010), and by the Junta de Castilla y Leon, references VA006A009, BU034A08 and GREX251-200

Gas storage

International audienceThe continuous increase of energy demands based on fossil fuels in the last years have lead to an increase of greenhouse gases (GHG) emission which strongly contribute to global warming. The main strategies to limit this phenomenon are related to the efficient capture of these gases and to the development of renewable energies sources with limited environmental impact. Particularly, carbon dioxide (CO2) and methane (CH4) are the main constituents of greenhouse gases while hydrogen (H2) is considered an alternative clean energy source to fossil fuels. Therefore, tremendous research to store these gases has been reported by several approaches and among them the physisorption on activated carbons (AC) have received significant attention. Their abundance, low cost and tunable porous structure and chemical functionalities with an existing wide range of precursors that includes bio-wastes make them ideal candidates for gas applications. This chapter presents the recent developments on CH4, CO2 and H2 storage by activated carbons with focus on biomass as precursor materials. An analysis of the main carbon properties affecting the AC's adsorption capacity (i.e. specific surface area, pore size and surface chemistry) is discussed in detail herein

Spread of a SARS-CoV-2 variant through Europe in the summer of 2020.

Following its emergence in late 2019, the spread of SARS-CoV-21,2 has been tracked by phylogenetic analysis of viral genome sequences in unprecedented detail3–5. Although the virus spread globally in early 2020 before borders closed, intercontinental travel has since been greatly reduced. However, travel within Europe resumed in the summer of 2020. Here we report on a SARS-CoV-2 variant, 20E (EU1), that was identified in Spain in early summer 2020 and subsequently spread across Europe. We find no evidence that this variant has increased transmissibility, but instead demonstrate how rising incidence in Spain, resumption of travel, and lack of effective screening and containment may explain the variant’s success. Despite travel restrictions, we estimate that 20E (EU1) was introduced hundreds of times to European countries by summertime travellers, which is likely to have undermined local efforts to minimize infection with SARS-CoV-2. Our results illustrate how a variant can rapidly become dominant even in the absence of a substantial transmission advantage in favourable epidemiological settings. Genomic surveillance is critical for understanding how travel can affect transmission of SARS-CoV-2, and thus for informing future containment strategies as travel resumes. © 2021, The Author(s), under exclusive licence to Springer Nature Limited

Advanced carbon materials for gas storage and space cryocoolers applications

El comportamiento de materiales carbonosos avanzados en dos aplicaciones (almacenamiento de hidrógeno y aplicación espacial) ha puesto de manifiesto que las propiedades de los materiales carbonosos se deben diseñar para la adsorción del correspondiente gas (H2 and He) a alta presión y diferentes temperaturas. Los resultados remarcan la importancia de optimizar la textura porosa (principalmente volumen de microporos y distribución de tamaño de la microporosidad) y densidad de los materiales para alcanzar altos valores de capacidades en base gravimétrica, y volumétrica, respectivamente, (en todos los casos, el adsorbente está confinado en un volumen restringido)Performance of advanced carbon materials in two applications, storage of H2 and space cryocoolers are reported, concluding that carbon material properties must be designed for the adsorption of the corresponding gas (H2 and He) at high pressures and different temperatures. Results shown here remark the importance of optimizing the porous texture (mainly the micropore volume and the micropore size distribution) and density of the materials for achieving high capacities in gravimetric basis, and volumetric, respectively (in all cases the adsorbent is confined in a limited volume)

Role of surface chemistry on electric double layer capacitance of carbon materials

A large number of porous carbon materials with different properties in terms of porosity, surface chemistry and electrical conductivity, were prepared and systematically studied as electric double layer capacitors in aqueous medium with H2SO4 as electrolyte. The precursors used are an anthracite, general purpose carbon fibres and high performance carbon fibres, which were activated by KOH, NaOH, CO2 and steam at different conditions. Among all of them, an activated anthracite with a BET surface area close to 1500 m2/g, presents the best performance, reaching a value of 320 F/g, using a three-electrode system. The results obtained for all the samples, agree with the well-known relationship between capacitance and porosity, and show that the CO-type oxygen groups have a positive contribution to the capacitance. A very good correlation between the specific capacitance and this type of oxygen groups has been found.The authors thank MEC for financial support (Project PPQ2003-03884)

Chemical and electrochemical characterization of porous carbon materials

Chemical and electrochemical techniques have been used in order to asses surface functionalities of porous carbon materials. An anthracite has been chemically activated using both KOH and NaOH as activating agents. As a result, activated carbons with high micropore volume (higher than 1 cm3/g) have been obtained. These samples were oxidized with HNO3 and thermally treated in N2 flow at different temperatures in order to obtain porous carbon materials with different amounts of surface oxygen complexes. Thermal treatment in H2 was also carried out. The sample treated with H2 was subsequently treated in air flow at 450 ºC. Thus, materials with very similar porous texture and widely different surface chemistry have been compared. The surface chemistry of the resulting materials was systematically characterized by TPD experiments and XPS measurements. Galvanostatic and voltammetric techniques were used to deepen into the characterization of the surface oxygen complexes. The combination of both, chemical and electrochemical methods provide unique information, regarding the key role of surface chemistry in improving carbon wettability in aqueous solution and the redox processes undergone by the surface oxygen groups. Both contributions are of relevance to understand the use of porous carbons as electrochemical capacitors.Ministerio de Ciencia y Tecnología (PPQ2003-03884)

Impact of the carbonisation temperature on the activation of carbon fibres and their application for hydrogen storage

Special issue: 2nd World Congress of Young Scientists on Hydrogen Energy Systems.Porous materials are gaining interest due to their potential for storing hydrogen via physisorption. In the present work, two carbon fibres, carbonised at 973 and 1273 K, have been chemically activated with KOH and NaOH, in order to obtain materials with optimised characteristics for hydrogen storage application. Highly microporous activated carbon fibres were obtained from both precursors, especially from the fibre carbonised at the lower carbonisation temperature, remarking its importance on its subsequent activation process. As activation agent, KOH is more effective for developing the narrow microporosity, and higher yields are obtained. H2 adsorption isotherms were measured at 298 K for pressures up to 20 MPa, and at 77 K up to 4 MPa. The maximum excess adsorption of hydrogen reached 1 wt% at 298 K and 3.8 wt% at 77 K. The total volumetric storage capacity is of 17 g/l at 298 K, and 32 g/l at 77 K.Financial help from the European Union (Marie Curie Research Training Network—HyTRAIN Project reference:512443), MEC (Accion complementaria; ENE2005-23824-E/CON), the Generalitat Valenciana (Accion complementaria; ACOMP06/089) and MEC-CTQ2006-08958PPQ. Samples supplied by Osaka gas Co., Ltd