Three of the fundamental catalytic limitations that have plagued the electrochemical production of hydrogen for decades still remain: low efficiency, short lifetime of catalysts and a lack of ...low-cost materials. Here, we address these three challenges by establishing and exploring an intimate functional link between the reactivity and stability of crystalline (CoS2 and MoS2) and amorphous (CoSx and MoSx) hydrogen evolution catalysts. We propose that Co(2+) and Mo(4+) centres promote the initial discharge of water (alkaline solutions) or hydronium ions (acid solutions). We establish that although CoSx materials are more active than MoSx they are also less stable, suggesting that the active sites are defects formed after dissolution of Co and Mo cations. By combining the higher activity of CoSx building blocks with the higher stability of MoSx units into a compact and robust CoMoSx chalcogel structure, we are able to design a low-cost alternative to noble metal catalysts for efficient electrocatalytic production of hydrogen in both alkaline and acidic environments.
Mesenchymal stem cells (MSC) were recently shown to migrate to injured tissues when transplanted systemically. The mechanisms underlying the migration and homing of these cells is, however, unclear. ...In this study, we examine the role of CD44 and its major ligand, hyaluronic acid, in the trafficking of intravenously injected MSC in the glycerol-induced mouse model of acute renal failure (ARF). In vitro, hyaluronic acid promoted a dose-dependent migration of the stem cells that was inhibited by an anti-CD44 blocking monoclonal antibody. In vivo, stem cells injected into mice with ARF migrated to the injured kidney where hyaluronic acid expression was increased. Their presence correlated with morphological and functional recovery. Renal localization of the MSC was blocked by pre-incubation with the CD44 blocking antibody or by soluble hyaluronic acid. Stem cells derived from CD44 knockout mice did not localize to the injured kidney and did not accelerate morphological or functional recovery. Reconstitution by transfection of CD44 knockout stem cells with cDNA encoding wild-type CD44, but not a loss of function CD44 unable to bind hyaluronic acid, restored in vitro migration and in vivo localization of the cells to injured kidneys. We suggest that CD44 and hyaluronic acid interactions recruit exogenous MSC to injured renal tissue and enhance renal regeneration.
Tailoring nanoarchitecture of materials offers unprecedented opportunities in utilization of their functional properties. Nanostructures of vanadium oxide, synthesized by electrochemical deposition, ...are studied as a cathode material for rechargeable Na-ion batteries. Ex situ and in situ synchrotron characterizations revealed the presence of an electrochemically responsive bilayered structure with adjustable intralayer spacing that accommodates intercalation of Na+ ions. Sodium intake induces organization of overall structure with appearance of both long- and short-range order, while deintercalation is accompanied with the loss of long-range order, whereas short-range order is preserved. Nanostructured electrodes achieve theoretical reversible capacity for Na2V2O5 stochiometry of 250 mAh/g. The stability evaluation during charge–discharge cycles at room temperature revealed an efficient 3 V cathode material with superb performance: energy density of ∼760 Wh/kg and power density of 1200 W/kg. These results demonstrate feasibility of development of the ambient temperature Na-ion rechargeable batteries by employment of electrodes with tailored nanoarchitectures.
Low-cost transition metal oxides are actively explored as alternative materials to precious metal-based electrocatalysts for the challenging multistep oxygen evolution reaction (OER). We utilized the ...Kirkendall effect allowing the formation of hollow polycrystalline, highly disordered nanoparticles (NPs) to synthesize highly active binary metal oxide OER electrocatalysts in alkali media. Two synthetic strategies were applied to achieve compositional control in binary transition metal oxide hollow NPs. The first strategy is capitalized on the oxidation of transition-metal NP seeds in the presence of other transition-metal cations. Oxidation of Fe NPs treated with Ni (+2) cations allowed the synthesis of hollow oxide NPs with a 1–4.7 Ni-to-Fe ratio via an oxidation-induced doping mechanism. Hollow Fe–Ni oxide NPs also reached a current density of 10 mA/cm2 at 0.30 V overpotential. The second strategy is based on the direct oxidation of iron–cobalt alloy NPs which allows the synthesis of hollow Fe x Co100–x -oxide NPs where x can be tuned in the range between 36 and 100. Hollow Fe36Co64-oxide NPs also revealed the current density of 10 mA/cm2 at 0.30 V overpotential in 0.1 M KOH.
The production of fatty acid methyl esters (FAME) from crude tobacco seed oil (TSO) having high free fatty acids (FFA) was investigated. Due to its high FFA, the TSO was processed in two steps: the ...acid-catalyzed esterification (ACE) followed by the base-catalyzed methanolysis (BCM). The first step reduced the FFA level to less than 2% in 25
min for the molar ratio of 18:1. The second step converted the product of the first step into FAME and glycerol. The maximum yield of FAME was about 91% in about 30
min. The tobacco biodiesel obtained had the fuel properties within the limits prescribed by the latest American (ASTM D 6751-02) and European (DIN EN 14214) standards, except a somewhat higher acid value than that prescribed by the latter standard (<0.5). Thus, tobacco seeds (TS), as agricultural wastes, might be a valuable renewable raw material for the biodiesel production.
Modulation of Pd nanoparticle (NP) crystallinity is achieved by switching the surfactants of different binding strengths. Pd NPs synthesized in the presence of weak binding surfactants such as ...oleylamine possess polyhedral shapes and a polycrystalline nature. When oleylamine is substituted by trioctylphosphine, a much stronger binding surfactant, the particles become spherical and their crystallinity decreases significantly. Moreover, the Pd NPs reconvert their polycrystalline structure when the surfactant is switched back to oleylamine. Through control experiments and molecular dynamics simulation, we propose that this unusual nanocrystallinity transition induced by surfactant exchange was resulted from a counterbalance between the surfactant binding energy and the nanocrystal adhesive energy. The findings represent a novel postsynthetic approach to tailoring the structure and corresponding functional performance of nanomaterials.
Going platinum: The theoretical description of electrocatalytic phenomena is extremely challenging. A simple, density functional theory based model has been developed that is able to give a ...semiquantitative description of the reaction kinetics for the electrocatalytic oxygen reduction on several platinum binary alloys, Pt3M (see graph).
Developing technologies for the production of alternative fuels from biorenewable resources is a field of interest for many researchers. Adequate substitute to diesel fuel is biodiesel that is ...synthesized through the transesterification of vegetable oils or animal fats and fulfilled the international standards. Ionic liquids (ILs) and deep eutectic solvents (DESs) have gained tremendous attention for their use in biodiesel production because of environmental benefits and process improvements. The present work overviews the use of ILs and DESs in the reaction and purification steps of biodiesel production processes where they are used as catalysts, cosolvents and extracting solvent. In addition, the possibilities of recycling and reusing of ILs and DESs are pointed out. Moreover, optimization and kinetic studies of biodiesel synthesis in the presence of ILs or DESs are discussed. The use of novel technologies combined with ILs or and DESs are also considered. Therefore, the present paper highlights the promising uses of ILs and DESs in biodiesel production in the future.
The methanolysis of sunflower oil was studied in the presence of CaO previously calcined at various temperatures and the optimal temperature for CaO calcination was determined. The sigmoidal process ...kinetics was explained by the initial triglyceride (TG) mass transfer controlled region, followed by the chemical reaction controlled region in the latter reaction period. The TG mass transfer limitation was due to the small available active specific catalyst surface, which was mainly covered by adsorbed molecules of methanol. In the later phase, the adsorbed methanol concentration decreased, causing the increase of both the available active specific catalyst surface and the TG mass transfer rate, and the chemical reaction rate become smaller than the TG mass transfer rate.
Biodiesel production from corn oil: A review Veljković, Vlada B.; Biberdžić, Milan O.; Banković-Ilić, Ivana B. ...
Renewable & sustainable energy reviews,
08/2018, Letnik:
91
Journal Article
Recenzirano
This paper deals with biodiesel production from corn oil as a feedstock via the transesterification and esterification reactions. To date, corn oil has not been considered a viable biodiesel ...feedstock because of its high edible value and relatively high price, but some industrial corn processing co-products, such as corn germ and dried distillers grains with solubles (DDGS), have potential for this application after the extraction of corn distillers oil (CDO). Here, after brief discussion of the issues related to corn botany, cultivation, and use, as well as the corn germ and oil composition, properties and use, the methods of corn processing for germ and DDGS recovery are presented. In addition, the mechanical and solvent extraction techniques for oil recovery from whole ground corn kernels, germs, and DDGS are considered. Furthermore, biodiesel production from corn oil, waste frying corn oil, and CDO is critically analyzed. It is expected that further investigation will be directed toward developing simpler, more effective and energy-saving technologies for biodiesel production from corn oil-based feedstocks, especially from CDO. The integration of biodiesel production directly into corn-based ethanol production will advance the overall economy of industrial plants. Furthermore, the fuel properties, performances and exhaust gas emissions of corn-based biodiesel and its blends with diesel fuel are discussed, taking into account the biodiesel quality standards. Finally, issues related to the environmental and socio-economic impacts of corn-based biodiesel production and use are also tackled.
•Oily co–products of industrial corn processing are promising biodiesel feedstocks.•“Green” oil extraction methods will improve corn oil recovery.•Simpler, more efficient and energy–saving corn-based biodiesel technology is needed.•The integrated reactor/separation process of biodiesel production is more efficient.•Biodiesel production can be integrated in the corn-based ethanol production.
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