pinecone/core-2020-05-10-deduplication huggingface dataset:
Limitations for current production in Geobacter sulfurreducens biofilms

Devices that exploit electricity produced by electroactive bacteria such as Geobacter sulfurreducens have not yet been demonstrated beyond the laboratory scale. The current densities are far from the maximum that the bacteria can produce because fundamental properties such as the mechanism of extracellular electron transport and factors limiting cell respiration remain unclear. In this work, a strategy for the investigation of electroactive biofilms is presented. Numerical modeling of the response of G. sulfurreducens biofilms cultured on a rotating disk electrode has allowed for the discrimination of different limiting steps in the process of current production within a biofilm. The model outputs reveal that extracellular electron transport limits the respiration rate of the cells furthest from the electrode to the extent that cell division is not possible. The mathematical model also demonstrates that recent findings such as the existence of a redox gradient in actively respiring biofilms can be explained by an electron hopping mechanism but not when considering metallic-like conductivities.Fil: Bonanni, P. Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina; Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentina;Fil: Bradley, Dan F.. University Of Liverpool. Chemistry Department; Reino Unido;Fil: Schrott, Germán David. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina; Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentina;Fil: Busalmen, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina; Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentina
Hydrolysis of oligosaccharides over solid acid catalysts: a review

Mild fractionation/pretreatment processes are becoming the most preferred choices for biomass processing within the biorefinery framework. To further explore their advantages, new developments are 
needed, especially to increase the extent of the hydrolysis of poly- and oligosaccharides. A possible way forward is the use of solid acid catalysts that may overcome many current drawbacks of other common methods. In this Review, the advantages and limitations of the use of heterogeneous catalysis for the main groups of solid acid catalysts (zeolites, resins, carbon materials, clays, silicas, and other oxides) and their relation to the hydrolysis of model soluble disaccharides and soluble poly- and oligosaccharides are presented and discussed. Special attention is given to the hydrolysis of hemicelluloses and hemicellulose-derived saccharides into monosaccharides, the impact on process performance of potential catalyst poisons originating from biomass and biomass hydrolysates (e.g., proteins, mineral ions, etc.). The data clearly point out 
the need for studying hemicelluloses in natura rather than in model compound solutions that do not retain the relevant factors influencing process performance. Furthermore, the desirable traits that solid acid catalysts must possess for the efficient hemicellulose hydrolysis are also presented and discussed with regard to the design of new catalysts
Hierarchical Sulfur‐Based Cathode Materials with Long Cycle Life for Rechargeable Lithium Batteries

Composite materials of porous pyrolyzed polyacrylonitrile–sulfur@graphene nanosheet (pPAN–S@GNS) are fabricated through a bottom‐up strategy. Microspherical particles are formed by spray drying of a mixed aqueous colloid of PAN nanoparticles and graphene nanosheets, followed by a simple heat treatment with elemental sulfur. The pPAN–S primary nanoparticles are wrapped homogeneously and loosely within a three‐dimensional network of graphene nanosheets (GNS). The hierarchical pPAN–S@GNS composite shows a high reversible capacity of 1449.3 mAh g −1  sulfur  or 681.2 mAh g −1  composite  in the second cycle; after 300 cycles at a 0.2 C charge/discharge rate the capacity retention is 88.8 % of its initial reversible value. Additionally, the coulombic efficiency (CE) during cycling is near 100 %, apart from in the first cycle, in which CE is 81.1 %. A remarkable capacity of near 700 mAh g −1  sulfur  is obtained, even at a high discharge rate of 10 C. The superior performance of pPAN–S@GNS is ascribed to the spherical secondary GNS structure that creates an electronically conductive 3D framework and also reinforces structural stability.     The Peter PAN of Composites : Composite materials of porous pyrolyzed polyacrylonitrile–sulfur@graphene nanosheet (pPAN–S@GNS) are prepared through a bottom‐up strategy. The superior rate capability and excellent cycling stability of pPAN–S@GNS is ascribed to the special spherical structure possessing an electronically conductive and rigid hierarchical framework
Graphene Oxide alpha Bi2O3 Composites for Visible Light Photocatalysis, Chemical Catalysis and Solar Energy Conversion

The growing challenges of environmental purification by solar photocatalysis, precious metal free catalysis and photocurrent generation in photovoltaic cells are receiving the utmost global attention. Here we demonstrate the one pot green chemical synthesis of a new stable heterostructured, eco friendly, multifunctional micro composite consisting of  amp; 945; Bi2O3 micro needles intercalated with anchored graphene oxide  GO  micro sheets  1.0 wt   for the above mentioned applications in a large economical scale. The bare  amp; 945; Bi2O3 micro needles display twice as better photocatalytic activities than commercial TiO2  Degussa P25  while the GO hybridized composite exhibit  4 6 times enhanced photocatalytic activities than neat TiO2 photocatalyst in the degradation of colored aromatic organic dyes  crystal violet and rhodamine 6G  under visible light irradiation  300 W tungsten lamp .    The highly efficient activity is associated with the strong surface adsorption ability of GO for aromatic dye molecules, the high carrier acceptability and efficient electron hole pair separation in Bi2O3 by individual adjoining GO sheets. Introduction of Ag nanoparticles  2.0 wt   further enhances the photocatalytic performance of the composite over 8 folds due to a plasmon induced electron transfer process from Ag nanoparticles via GO sheets into the conduction band of Bi2O3. The new composites are also catalytically active. They catalyze the reduction of 4 nitrophenol to 4 aminophenol in presence of borohydride ions. Photoanodes assembled from GO  amp; 945; Bi2O3 and Ag GO  amp; 945; Bi2O3 composites display an improved photocurrent response  power conversion efficiency   20  higher  over those prepared without GO in dye sensitized solar cells  DSSCs
Governing Chemistry of Cellulose Hydrolysis in Supercritical Water

Producción CientíficaAt extremely low reaction times (0.02 s), cellulose was hydrolyzed in supercritical water (T=400 °C and P=25 MPa) to obtain a sugar yield higher than 95 wt %, whereas the 5-hydroxymethylfurfural (5-HMF) yield was lower than 0.01 wt %. If the reaction time was increased to 1 s, the main product was glycolaldehyde (60 wt %). Independently of the reaction time, the yield of 5-HMF was always lower than 0.01 wt %. To evaluate the reaction mechanism of biomass hydrolysis in pressurized water, several parameters (temperature, pressure, reaction time, and reaction medium) were studied for different biomasses (cellulose, glucose, fructose, and wheat bran). It was found that the H+ and OH− ion concentration in the reaction medium as a result of water dissociation is the determining factor in the selectivity. The reaction of glucose isomerization to fructose and the further dehydration to 5-HMF are highly dependent on the ion concentration. By an increase in the pOH/pH value, these reactions were minimized to allow control of 5-HMF production. Under these conditions, the retroaldol condensation pathway was enhanced, instead of the isomerization/dehydration pathway.Ministerio de Economía, Industria y Competitividad - FEDER (Proyect CTQ2013-44143-R
Heterojunction solar cells based on silicon and composite films of graphene oxide and carbon nanotubes

Graphene oxide (GO) sheets have been used as the surfactant to disperse single-walled carbon nanotubes (CNT) in water to prepare GO/CNT electrodes that are applied to silicon to form a heterojunction that can be used in solar cells. GO/CNT films with different ratios of the two components and with various thicknesses have been used as semitransparent electrodes, and the influence of both factors on the performance of the solar cell has been studied. The degradation rate of the GO/CNT-silicon devices under ambient conditions has also been explored. The influence of the film thickness on the device performance is related to the interplay of two competing factors, namely, sheet resistance and transmittance. CNTs help to improve the conductivity of the GO/CNT film, and GO is able to protect the silicon from oxidation in the atmosphere
Processes forming Gas, Tar, and Coke in Cellulose Gasification from Gas-Phase Reactions of Levoglucosan as Intermediate

The gas‐phase pyrolysis of levoglucosan (LG), the major intermediate species during cellulose gasification, was studied experimentally over the temperature range of 400–900 °C. Gaseous LG did not produce any dehydration products, which include coke, furans, and aromatic substances, although these are characteristic products of the pyrolysis of molten LG. Alternatively, at >500 °C, gaseous LG produced only fragmentation products, such as noncondensable gases and condensable C₁–C₃ fragments, as intermediates during noncondensable gas formation. Therefore, it was determined that secondary reactions of gaseous LG can result in the clean (tar‐ and coke‐free) gasification of cellulose. Cooling of the remaining LG in the gas phase caused coke formation by the transition of the LG to the molten state. The molecular mechanisms that govern the gas‐ and molten‐phase reactions of LG are discussed in terms of the acid catalyst effect of intermolecular hydrogen bonding to promote the molten‐phase dehydration reactions
Electrolytes Ageing in Lithium-ion Batteries:AMechanistic Study from Picosecond to Long Timescales

International audienceThe ageing phenomena occurring in various diethyl carbonate/LiPF6 solutions are studied using gamma and pulse radiolysis as a tool to generate similar species as the ones occurring in electrolysis of Li-ion batteries (LIBs). According to picosecond pulse radiolysis experiments, the reaction of the electron with (Li+, PF6−) is ultrafast, leading to the formation of fluoride anions that can then precipitate into LiF(s). Moreover, direct radiation-matter interaction with the salt produces reactive fluorine atoms forming HF(g) and C2H5F(g). The strong Lewis acid PF5 is also formed. This species then forms various R1R2R3P=O molecules, where R is mainly −F, −OH, and −OC2H5. Substitution reactions take place and oligomers are slowly formed. Similar results were obtained in the ageing of an electrochemical cell filled with the same model solution. This study demonstrates that radiolysis enables a description of the reactivity in LIBs from the picosecond timescale until a few days
Association and diffusion of Li+ in carboxymethylcellulose solutions with application to environmentally friendly Li-ion batteries: a combined Molecular Dynamics and NMR study

Carboxymethylcellulose (CMC) has been proposed as a polymeric binder for the electrodes in environmentally friendly Li-ion batteries. Its physical properties and interaction with Li+ ions in water are interesting from the point of view of electrode preparationprocessability in water is one of the main reasons for its environmental friendlinessbut also for its possible application in aqueous Li-ion batteries. We combine MD simulations and variable-time PFGSE-NMR spectroscopy to investigate Li+ transport in CMC-based solutions. Both simulation and experiment show that, at concentrations such that Li-CMC has a gel like consistency, the Li+ diffusion coefficient is still very close to that in water. These ions interact preferentially with CMC’s carboxylate groups, giving rise to a rich variety of coordination patterns. However, the diffusion of Li+ in these systems is essentially unrestricted, with a fast, nanosecond-scale exchange of the ions between CMC and the aqueous environment
In situ radiographic investigation of  de lithiation mechanisms in a tin electrode lithium ion battery.

The lithiation and delithiation mechanisms of multiple Sn particles in a customized flat radiography cell were investigated by in amp; 8197;situ synchrotron radiography. For the first time, four  de lithiation phenomena in a Sn electrode battery system are highlighted  1  amp; 8197;the  de lithiation behavior varies between different Sn particles, 2  amp; 8197;the time required to lithiate individual Sn particles is markedly different from the time needed to discharge the complete battery, 3  amp; 8197;electrochemical deactivation of originally electrochemically active particles is reported, and 4  amp; 8197;a change of electrochemical behavior of individual particles during cycling is found and explained by dynamic changes of  de lithiation pathways amongst particles within the electrode. These unexpected findings fundamentaly expand the understanding of the underlying  de lithiation mechanisms inside commercial lithium ion batteries  LIBs  and would open new design principles for high performance next generation LIB
Molybdenum Disulfide-Coated Lithium Vanadium Fluorophosphate Anode: Experiments and First-Principles Calculations

To develop a new anode material to meet the increasing demands of lithium-ion battery, MoS2 is used for the first time to modify the C/LiVPO4F anode to improve its lithium-storage performance between 3 and 0.01 V. Morphological observations reveal that the MoS2-modified C/LiVPO4F particles (M-LVPF) are wrapped by an amorphous carbon as interlayer and layered MoS2 as external surface. Charge–discharge tests show that M-LVPF delivers a high reversible capacity of 308 mAh g−1 at 50 mA g−1. After 300 cycles at 1.0 A g−1, a capacity retention of 98.7 % is observed. Moreover, it exhibits high rate capability with a specific capacity of 199 mAh g−1 at 1.6 A g−1. Electrochemical impedance spectroscopy tests indicate that the lithium-ion diffusion and charge-exchange reaction at the surface of M-LVPF are greatly enhanced. First-principles calculations for the MoS2 (001)/C/LiVPO4F (010) system demonstrate that the absorption of MoS2 on C/LiVPO4F is exothermic and spontaneous and that the electron transfer at the MoS2-absorbed C/LiVPO4F surface is enhanced.postprin
Green and selective polycondensation methods toward linear sorbitol-based polyesters: enzymatic versus organic and metal-based catalysis

Renewable polyesters derived from a sugar alcohol (i.e., sorbitol) were synthesized by solvent-free polycondensation. The aim was to prepare linear polyesters with pendant hydroxyl groups along the polymer backbone. The performance of the sustainable biocatalyst SPRIN liposorb CALB [an immobilized form of Candida antarctica lipase B (CALB); SPRIN technologies] and the organo-base catalyst 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD) were compared with two metal-based catalysts: dibutyl tin oxide (DBTO) and scandium trifluoromethanesulfonate [also known as scandium triflate, Sc(OTf)3]. For the four catalytic systems, the efficiency and selectivity for the incorporation of sorbitol were studied, mainly using 13C and 31P NMR spectroscopies, whereas side reactions, such as ether formation and dehydration of sorbitol, were evaluated using MALDI-TOF-MS. Especially the biocatalyst SPRIN liposorb CALB succeeded in incorporating sorbitol in a selective way without side reactions, leading to close-to-linear polyesters. By using a renewable hydroxyl-reactive curing agent based on l-lysine, transparent and glossy poly(ester urethane) networks were successfully synthesized offering a tangible example of bio-based coatings.Peer ReviewedPostprint (author's final draft
Tandem catalytic depolymerization of lignin by water-tolerant Lewis acids and rhodium complexes

P.C.A.B. thanks the Netherlands Organization for Scientific Research (NWO) for a Vernieuwingsimpuls Veni Grant. The CatchBio program is acknowledged for financial support. N.J.W. thanks EPSRC for funding by the EP/J018139/1, EP/K00445X/1 grants and an EPSRC Doctoral Prize Fellowship to C.S.L. Saumya Dabral and Prof. Carsten Bolm (RWTH Aachen) are gratefully acknowledged for providing an authentic sample of 5b. Dr. Wouter Huijgen (ECN) is acknowledged for Klason lignin determination. SuBiCat Initial Training Network, Call FP7-PEOPLE-2013-ITN, #607044) is gratefully acknowledged.Lignin is an attractive renewable feedstock for aromatic bulk and fine chemicals production, provided that suitable depolymerization procedures are developed. Here, we describe a tandem catalysis strategy for ether linkage cleavage within lignin, involving ether hydrolysis by water-tolerant Lewis acids followed by aldehyde decarbonylation by a rhodium complex. In situ decarbonylation of the reactive aldehydes limits loss of monomers by recondensation, a major issue in acid-catalyzed lignin depolymerization. Rate of hydrolysis and decarbonylation were matched using lignin model compounds, allowing the method to be successfully applied to softwood, hardwood and herbaceous dioxasolv lignins as well as poplar sawdust to give the anticipated decarbonylation products, and, rather surprisingly, 4-(1-propenyl)phenols. Promisingly, product selectivity can be tuned by variation of Lewis acid strength and lignin source.Publisher PDFPeer reviewe
Metal triflates for the production of aromatics from lignin

This work was funded by the European Union (Marie Curie ITN ‘SuBiCat’ PITN-GA-2013-607044, PJD, CWL, NJW, PCKL, KB, JGdeV) as well as EP/J018139/1, EP/K00445X/1 grants (NJW and PCJK) and an EPSRC Doctoral Prize Fellowship (CSL).The depolymerization of lignin into valuable aromatic chemicals is one of the key goals towards establishing economically viable biorefineries. In this contribution we present a simple approach for converting lignin to aromatic monomers in high yields, under mild reaction conditions. The methodology relies on the use of catalytic amounts of easy to handle metal triflates (M(OTf)x). Initially, we evaluated the reactivity of a broad range of metal triflates using simple lignin model compounds. More advanced lignin model compounds were also used to study the reactivity of different lignin linkages. The product aromatic monomers were either phenolic C2-acetals obtained by stabilization of the aldehyde cleavage products by reaction with ethylene glycol, or methyl aromatics obtained by catalytic decarbonylation. Notably, when the former method was ultimately tested on lignin, especially Fe(OTf)3 proved very effective and the phenolic C2-acetal products were obtained in an excellent, 19.3±3.2 wt % yield.PostprintPeer reviewe
Cooperative Catalytic Effect of ZrO2 and a-Fe2O3 Nanoparticles on BiVO4 Photoanodes for Enhanced Photoelectrochemical Water Splitting

Photoelectrochemical water splitting with metal oxide semiconductors offers a cost-competitive alternative for the generation of solar fuels. Most of the materials studied so far suffer from poor charge-transfer kinetics at the semiconductor/liquid interface, making compulsory the use of catalytic layers to overcome the large overpotentials required for the water oxidation reaction. Herein, we report a very soft electrolytic synthesis deposition method, which allows remarkably enhanced water oxidation kinetics of BiVO4 photoanodes by the sequential addition of Zr and Fe precursors. Upon a heat treatment cycle, these precursors are converted into monoclinic ZrO2 and α-Fe2O3 nanoparticles, which mainly act as catalysts, leading to a five-fold increase of the water oxidation photocurrent of BiVO4. This method provides a versatile platform that is easy to apply to different semiconductor materials, fully reproducible, and facile to scale-up on large area conductive substrates with attractive implications for technological deploymentWe thank financial support from the University Jaume I through the project P1⋅1B2011-50. Serveis Centrals at UJI (SCIC) are also acknowledged
Influence of binders and solvents on stability of Ru/RuOx nanoparticles on ITO nanocrystals as Li–O2 battery cathodes

Fundamental research on Li–O2 batteries remains critical, and the nature of the reactions and stability are paramount for realising the promise of the Li–O2 system. We report that indium tin oxide (ITO) nanocrystals with supported 1–2 nm oxygen evolution reaction (OER) catalyst Ru/RuOx nanoparticles (NPs) demonstrate efficient OER processes, reduce the recharge overpotential of the cell significantly and maintain catalytic activity to promote a consistent cycling discharge potential in Li–O2 cells even when the ITO support nanocrystals deteriorate from the very first cycle. The Ru/RuOx nanoparticles lower the charge overpotential compared with those for ITO and carbon-only cathodes and have the greatest effect in DMSO electrolytes with a solution-processable F-free carboxymethyl cellulose (CMC) binder (<3.5 V) instead of polyvinylidene fluoride (PVDF). The Ru/RuOx/ITO nanocrystalline materials in DMSO provide efficient Li2O2 decomposition from within the cathode during cycling. We demonstrate that the ITO is actually unstable from the first cycle and is modified by chemical etching, but the Ru/RuOx NPs remain effective OER catalysts for Li2O2 during cycling. The CMC binders avoid PVDF-based side-reactions and improve the cyclability. The deterioration of the ITO nanocrystals is mitigated significantly in cathodes with a CMC binder, and the cells show good cycle life. In mixed DMSO–EMITFSI [EMITFSI=1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide] ionic liquid electrolytes, the Ru/RuOx/ITO materials in Li–O2 cells cycle very well and maintain a consistently very low charge overpotential of 0.5–0.8 V
Evaluation of the effect of sulfur on the performance of Ni/CGO-based solid oxide fuel cell (SOFC) anodes

The focus of this study is the measurement and understanding\ud
of the sulfur poisoning phenomena of Ni/gadolinium-doped\ud
ceria (CGO) based solid oxide fuel cells (SOFC). Cells with Ni/\ud
CGO10 and NiCu5/CGO40 anodes were characterized by using\ud
impedance spectroscopy at different temperatures and H2/H2O\ud
fuel ratios. The short-term sulfur poisoning behavior was investigated\ud
systematically at temperatures of 800–9508C, current\ud
densities of 0–0.75 Acm@2, and H2S concentrations of 1–\ud
20 ppm. A sulfur poisoning mitigation effect was observed at\ud
high current loads and temperatures. The poisoning behavior\ud
was reversible for short exposure times. It was observed that\ud
the sulfur-affected processes exhibited significantly different\ud
relaxation times that depend on the Gd content in the CGO\ud
phase. Moreover, it was demonstrated that the capacitance of\ud
Ni/CGO10 anodes is strongly dependent on the temperature\ud
and gas-phase composition, which reflects a changing Ce3+/\ud
Ce4+ ratio
One-Pot Preparation of Dimethyl Isosorbide from d-Sorbitol via Dimethyl Carbonate Chemistry

Direct synthesis of dimethyl isosorbide (DMI) from d-sorbitol via dimethyl carbonate (DMC) chemistry is herein first reported. High yield of DMI was achieved using the nitrogen superbase 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst and performing the reaction in a stainless steel autoclave by increasing the temperature from 90 to 200°C. In this procedure, DMC features its full capacity acting in the different steps of the process as carboxymethylating, leaving-group (cyclization), and methylating agent; DMC is also employed as the reaction media