Institute Carboquimica ICB CSIC

Zaragoza, Spain

Institute Carboquimica ICB CSIC

Zaragoza, Spain
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Martin A.,University of Alcalá | Hernandez-Ferrer J.,Institute Carboquimica ICB CSIC | Vazquez L.,CSIC - Institute of Materials Science | Martinez M.-T.,Institute Carboquimica ICB CSIC | Escarpa A.,University of Alcalá
RSC Advances | Year: 2014

This work describes a rationalization of the interactions between two fully characterized graphene nanoribbons (GNRs) and a set of significant target molecules. The GNRs were carefully synthesized by unzipping multi-walled carbon nanotubes (MWCNTs) to yield graphene oxide nanoribbons (GNRox) containing 44 wt% oxygen. The GNRox were reduced to yield reduced graphene oxide nanoribbons (GNRred) containing 14 wt%. Each material was characterized by atomic force microscopy, transmission electronic microscopy, Raman spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and voltammetry techniques. Differential pulse voltammetry was used to assess the detection of two strategically selected groups of molecules, including benzenediols, hydroquinone, catechol, and resorcinol, as well as, l-dopa, ascorbic acid, uric acid, and l-tyrosine. The results showed that GNRs provided significantly better electrochemical responses compared to MWCNTs and the non-modified glassy carbon electrode. The chemistry of the few layers of graphene strongly influenced the electrochemical properties of the material. GNRox may be the material of choice for sensing molecules having high oxidation potentials. GNRred, on the other hand, yielded an excellent sensitivity for aromatic molecules in which π-π interactions were dominant or the number of conjugated 1,2-diols present was high. GNRred combines the advantages of the high proportion of sp2-carbon atoms with the presence of a few oxygen moieties remaining in the lattice after the reduction step. The primary interactions responsible for the shift in oxidation potentials were elucidated. This work presents new opportunities for tailoring graphene to a particular sensing application based on the specific chemistry of the molecule. © 2014 The Royal Society of Chemistry.

Fraile J.M.,University of Zaragoza | Garcia-Bordeje E.,Institute Carboquimica ICB CSIC | Roldan L.,University of Zaragoza
Journal of Catalysis | Year: 2012

Sulfonated hydrothermal carbons present high activity for esterification of palmitic acid with alcohols. However, the catalyst is significantly deactivated upon recovery. Leaching of sulfonated species does not account for this deactivation, which is observed even by pretreatment only with the alcohol under reflux. Solid state NMR shows the presence of chemically bound alkyl groups coming from the alcohol, clearly different from strongly physisorbed species obtained by pretreatment at room temperature. The formation of sulfonate esters accounts for the deactivation behavior in reactions taking place in alcohols as solvents, mainly with methanol due to its higher reactivity. © 2012 Elsevier Inc. All rights reserved.

Martinez J.D.,Institute Carboquimica ICB CSIC | Martinez J.D.,Pontifical Bolivarian University | Puy N.,Institute Carboquimica ICB CSIC | Murillo R.,Institute Carboquimica ICB CSIC | And 3 more authors.
Renewable and Sustainable Energy Reviews | Year: 2013

This review deals with the state-of-the-art of waste tyre pyrolysis for the first time in literature. Pyrolysis has been addressed as an attractive thermochemical process to tackle the waste tyre disposal problem while allowing energy recovery. Pyrolysis enables the separation of carbon black from tyres and the volatile matter released (condensable and non-condensable compounds) has the potential of renewable energy recovery given the significant proportion of natural rubber present in the tyre. Given this waste-to-energy pathway, a comprehensive review has been carried out in order to show the effects of the main process conditions (heating rate, temperature, pressure, carrier gas flow rate and type, volatiles residence time and pyrolysis time) on the physicochemical properties and distributions of the resulting products (gas, liquid and solid fractions). It has also been reviewed the influence of the size and composition of the feedstock. All reported results have been framed regarding the type of reactor as well as the experimental conditions used to avoid contradictions among the large number of publications on the subject. It is shown that the occurrence of secondary reactions is very sensitive to the interaction of the aforementioned variables. Also, the main properties of the pyrolytic products are pointed out. The liquid and gaseous fractions obtained are a valuable fuel source; while the solid fraction (char) has the recovery potential of low- grade carbon black or as carbon adsorbent after applying an activation step. Special attention has been given to the liquid fraction, highlighting its properties as alternative fuel in compression ignition engines. © Copyright 2013 Published by Elsevier Ltd. All rights reserved.

Callen M.S.,Institute Carboquimica ICB CSIC | Iturmendi A.,Institute Carboquimica ICB CSIC | Lopez J.M.,Institute Carboquimica ICB CSIC
Environmental Pollution | Year: 2014

One year sampling (2011-2012) campaign of airborne PM2.5-bound PAH was performed in Zaragoza, Spain. A source apportionment of total PAH by Positive Matrix Factorization (PMF) was applied in order to quantify potential PAH pollution sources.Four sources were apportioned: coal combustion, vehicular emissions, stationary emissions and unburned/evaporative emissions. Although Directive 2004/107/EC was fulfilled regarding benzo(a)pyrene (BaP), episodes exceeding the limit value of PM2.5 according to Directive 2008/50/EC were found. These episodes of high negative potential for human health were studied, obtaining a different pattern for the exceedances of PM2.5 and the lower assessment threshold of BaP (LATBaP). In both cases, stationary emissions contributed majority to total PAH. Lifetime cancer risk exceeded the unit risk recommended by the World Health Organization for those episodes exceeding the LATBaP and the PM2.5 exceedances for the warm season. For the cold season, the risk was higher for the LATBaP than for the PM2.5 exceedances. © 2014 Elsevier Ltd. All rights reserved.

Marco Y.,Institute Carboquimica ICB CSIC | Roldan L.,Institute Carboquimica ICB CSIC | Armenise S.,Institute Carboquimica ICB CSIC | Garcia-Bordeje E.,Institute Carboquimica ICB CSIC
ChemCatChem | Year: 2013

Ru nanoparticles were supported on monoliths that were coated with variously functionalized carbon nanofibers (CNFs), that is, un-doped CNFs, CNFs that had been post-treated with H2O2, and CNFs that had been doped with nitrogen during their growth. The Ru uptake (by equilibrium adsorption) onto N-doped CNFs was larger compared to that on their un-doped and O-doped counterparts. The functionalization of the CNF support did not play a significant role in determining the size of the deposited Ru nanoparticles, but it substantially impacted on the sintering under the reaction conditions and on the electron density of the reduced metal. Among the catalysts on the different CNF supports, Ru on N-CNF exhibited the highest H2 productivity from ammonia decomposition, which pointed to electronic effects that were induced by functionalization of the support. What a state of affairs: High NH 3-decomposition conversions were obtained at low temperatures by using a supported Ru catalyst on a honeycomb monolith that was coated with N-doped carbon nanofibers (N-CNF). The higher negative charge on the Ru center accounted for its enhanced performance compared to its un-doped CNF-supported counterpart. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Valles C.,Institute Carboquimica ICB CSIC | Jimenez P.,Institute Carboquimica ICB CSIC | Munoz E.,Institute Carboquimica ICB CSIC | Benito A.M.,Institute Carboquimica ICB CSIC | Maser W.K.,Institute Carboquimica ICB CSIC
Journal of Physical Chemistry C | Year: 2011

We report the formation of a solid-state charge-transfer complex upon simultaneous reduction of a graphene oxide-polyaniline (GO-PANI) composite consisting of GO sheets coated by a thin layer of PANI. The reduced R(GO-PANI) material exhibits an unprecedented donor-acceptor interaction at the interface between RGO sheets and the thin PANI layer coating. A conceptual explanation is proposed in which RGO plays a dual role as electron acceptor and as large counterion stabilizing an atypical intermediate oxidation state of PANI. Moreover, the donor-acceptor interactions are responsible for superior materials characteristics, such as excellent water dispersibility, high environmental (chemical and thermal) degradation stability, and enhanced electric conductivity as high as 2600 S/m. These results may enable further opportunities for the development of novel electroactive materials based on graphene and intrinsically conducting polymers and the fabrication of corresponding flexible electronic devices through traditional solution processing techniques. © 2011 American Chemical Society.

Adanez J.,Institute Carboquimica ICB CSIC | Abad A.,Institute Carboquimica ICB CSIC | Garcia-Labiano F.,Institute Carboquimica ICB CSIC | Gayan P.,Institute Carboquimica ICB CSIC | De Diego L.F.,Institute Carboquimica ICB CSIC
Progress in Energy and Combustion Science | Year: 2012

This work is a comprehensive review of the Chemical-Looping Combustion (CLC) and Chemical-Looping Reforming (CLR) processes reporting the main advances in these technologies up to 2010. These processes are based on the transfer of the oxygen from air to the fuel by means of a solid oxygen-carrier avoiding direct contact between fuel and air for different final purposes. CLC has arisen during last years as a very promising combustion technology for power plants and industrial applications with inherent CO 2 capture which avoids the energetic penalty present in other competing technologies. CLR uses the chemical looping cycles for H 2 production with additional advantages if CO 2 capture is also considered. The review compiles the main milestones reached during last years in the development of these technologies regarding the use of gaseous or solid fuels, the oxygen-carrier development, the continuous operation experience, and modelling at several scales. Up to 2010, more than 700 different materials based on Ni, Cu, Fe, Mn, Co, as well as other mixed oxides and low cost materials, have been compiled. Especial emphasis has been done in those oxygen-carriers tested under continuous operation in Chemical-Looping prototypes. The total time of operational experience (≈3500 h) in different CLC units in the size range 0.3-120 kW th, has allowed to demonstrate the technology and to gain in maturity. To help in the design, optimization, and scale-up of the CLC process, modelling work is also reviewed. Different levels of modelling have been accomplished, including fundamentals of the gas-solid reactions in the oxygen-carriers, modelling of the air- and fuel-reactors, and integration of the CLC systems in the power plant. Considering the great advances reached up to date in a very short period of time, it can be said that CLC and CLR are very promising technologies within the framework of the CO 2 capture options. © 2011 Elsevier Ltd. All rights reserved.

Garcia-Bordeje E.,Institute Carboquimica ICB CSIC | Armenise S.,Institute Carboquimica ICB CSIC | Roldan L.,Institute Carboquimica ICB CSIC
Catalysis Reviews - Science and Engineering | Year: 2014

This perspective article focuses on the recent advances in the rational design of catalyst for NH3 decomposition at different length scales, from catalyst nanoparticles to reactor design. For an overall optimum performance, all scales should be optimized in a concerted manner. The study of the mechanism of reaction has given guidelines for the catalyst design. As far as reactor design is concerned, a structured reactor is beneficial for this reaction because it minimizes the inhibiting effect of produced H2 besides other inherent advantages. This holistic optimization of catalysts is expected to pave the way for application of NH3 as H2 storage media. © 2014 Taylor and Francis Group, LLC.

Callen M.S.,Institute Carboquimica ICB CSIC | Lopez J.M.,Institute Carboquimica ICB CSIC | Iturmendi A.,Institute Carboquimica ICB CSIC | Mastral A.M.,Institute Carboquimica ICB CSIC
Environmental Pollution | Year: 2013

The total PAH associated to the airborne particulate matter (PM10) was apportioned by one receptor model based on positive matrix factorization (PMF) in an urban environment (Zaragoza city, Spain) during February 2010-January 2011. Four sources associated with coal combustion, gasoline, vehicular and stationary emissions were identified, allowing a good modelling of the total PAH (R2 = 0.99). A seasonal behaviour of the four factors was obtained with higher concentrations in the cold season. The NE direction was one of the predominant directions showing the negative impact of industrial parks, a paper factory and a highway located in that direction. Samples were classified according to hierarchical cluster analysis obtaining that, episodes with the most negative impact on human health (the highest lifetime cancer risk concentrations), were produced by a higher contribution of stationary and vehicular emissions in winter season favoured by high relative humidity, low temperature and low wind speed. © 2012 Elsevier Ltd. All rights reserved.

Valles C.,Institute Carboquimica ICB CSIC | David Nunez J.,Institute Carboquimica ICB CSIC | Benito A.M.,Institute Carboquimica ICB CSIC | Maser W.K.,Institute Carboquimica ICB CSIC
Carbon | Year: 2012

We report the fabrication of flexible conductive graphene paper through a direct and gentle annealing process of graphene oxide paper. Thermal treatments at 700 °C under argon or hydrogen atmosphere directly applied to parent graphene oxide paper lead to a significant removal of disruptive oxygen-containing functional groups, and to a considerable recovery of the sp 2 network structure. Detailed comparison of chemical and combined chemical-thermal treatments by scanning electronic microscopy (SEM), Raman, X-photoelectron spectroscopy (XPS) and conductivity measurements underline the high efficiency of the direct annealing process. The resulting highly reduced graphene oxide paper exhibits electrical conductivities as high as 8100 S/m representing an increase of five orders of magnitude with respect to the parent graphene oxide paper, which significantly outperforms the results of chemical treatments. Moreover, our direct and gentle thermal reduction allows maintaining the structural integrity and mechanical flexibility of the parent graphene oxide paper thus overcoming problems of brittleness typically encountered in annealing processes. Our approach sets the base for an easy, cost-effective and environmentally friendly fabrication route for flexible conducting graphene paper of great application potential as flexible electrodes in various fields of technology. © 2011 Elsevier Ltd. All rights reserved.

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