Carbon nanotubes/amorphous carbon composites as high-power negative electrodes in lithium ion capacitors

A nitrogen-rich carbon nanotubes/amorphous carbon (CNT/C) composite was prepared by carbonising a CNT/polyaniline (PANI) composite, and characterised. Scanning electron microscopy and X-ray photoelectron spectroscopy confirmed that the composite retained a mesoporous CNT structure as its backbone, whilst the nitrogen-rich PANI-derived carbon formed a thin amorphous coating on the CNT surface. Electrochemical characterisation of the CNT/C composite indicated that it had nearly double the reversible Li⁺ intercalation capacity (390 vs. 219 mAh g^?1) and 39 % less irreversible capacity (622 vs. 1,015 mAh g^?1) than the pristine CNT. The CNT/C composite showed exceptionally high rate capability with a de-intercalation capacity of 81 mAh g^?1 at a very high charge/discharge rate of 60 C (time taken for charge or discharge is 1 min) (1 C = 1 h charge or discharge), whereas the pristine CNT delivered 53 mAh g^?1 at this C-rate. By comparison, the rate capabilities of conventional graphite (N3 and SLP30) were very poor above 5 C (~17 mAh g^?1 at 5 C). Both the pristine CNT and CNT/C composite showed an excellent cyclability at 1 C charge/discharge over 600 cycles. The CNT/C composite maintained a fairly stable capacity of ~200 mAh g^?1 after 600 cycles, whilst the commercial graphite showed a steady and significant decrease in de-intercalation capacity; reaching <70 mAh g^?1 after 600 cycles.     

Pt nanoparticles synthesized with new surfactants: improvement in C1–C3 alcohol oxidation catalytic activity

Platinum electrocatalysts were prepared using PtCl₄ as a starting material and 1-decylamine, N,N-dimethyldecylamine, 1-dodecylamine, N,N-dimethyldodecylamine, 1-hexadecylamine, and 1-octadecylamine as surfactants. These surfactants were used for the first time in this synthesis to determine whether the primary and/or tertiary structure and/or chain length of the surfactants, affects the size and/or activity of the catalysts in C₁–C₃ alcohol electro-oxidation reactions. Electrochemical measurements (cyclic voltammetry and chronoamperometry) indicated that the highest electrocatalytic performance was observed for the Pt nanocatalysts that were stabilized by N,N-dimethyldecylamine, and this has a tertiary amine structure with a short chain length (R = C₁₀H₂₁). The high performance may be due to the high electrochemical surface area, Pt(0)/Pt(IV) ratio, %Pt utility, and roughness factor (R _f). X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy, and transmission electron microscopy were used to determine the parameters that affect the catalytic activities.     

Improved electro-assisted removal of phosphates and nitrates using mesoporous carbon aerogels with controlled porosity

Three-activated carbon aerogels were synthesized by CO₂ activation of the materials prepared by the polycondensation of resorcinol and formaldehyde mixtures followed by supercritical drying. The obtained carbon aerogels were characterized and used as electrode materials for the electrosorption of sodium phosphate and nitrate. X-ray diffraction and Raman spectroscopy showed the dependence of the structural ordering of the aerogels with the resorcinol/catalyst ratio and the extent of activation. The electrosorption capacitance evaluated by cyclic voltammetry revealed large values for the activated samples containing a large contribution of mesopores, regardless the electrolyte salt. Due to an adequate combination of chemical and porous features, the desalting capacity of the activated carbon aerogel electrodes exceeded that of the as-prepared materials. The evaluation of the kinetic properties by chronocoulometric relaxation and impedance spectroscopy showed a decrease of time constant and resistances for highly mesoporous activated samples. A high deionization capacity and fast electrode discharge was detected for the deionization of sodium nitrate on the highly mesoporous activated aerogel. Data also showed the efficient electrosorption of ionic species on consecutive charge/discharge cycles, confirming the stability of the aerogel electrodes at the high applied potentials.     

Alkaline activation of coals and carbon-base materials

Data on the reactions and processes occurring under the conditions of the alkaline activation of carbon substances—the production of activated carbons by the thermolysis of carbon substances in the presence of alkali metal hydroxides MOH—are summarized. The following most important activation processes were recognized: (1) the interaction of functional groups with MOH and the formation of intermediate structures with the C-O-M group; (2) their conversion into metal-containing compounds (primarily, M₂CO₃ and M₂O) in reactions with carbon, especially, with terminal C atoms on the periphery of graphenes; and (3) the reduction of M₂CO₃ and M₂O to the metal M, which is intercalated into the interlayer spaces of crystallites. The mechanism of alkaline activation was studied in most detail for KOH as an activating agent. The thermally initiated reduction of potassium oxide with carbon and the intercalation of potassium metal are the two most important processes for the development of the microporosity of activated carbon.     

Environmental ageing studies of impact modified waste polypropylene

Toughness of rigid thermoplastic is an important mechanical property in polymer technology. In the present study, toughening of waste polypropylene (WPP) with ethylene–propylene–diene monomer (EPDM) rubber at different loading levels was carried out by melt blending at 180 °C. The EPDM-toughened WPP samples were characterized for its thermo-mechanical properties. The effect of carbon black (5 wt%) as a functional filler in WPP/EPDM to impart UV protection was also studied. The test sheets were subjected to natural weathering in variable climatic conditions for a 4-month period of time and were taken out at regular intervals for characterization. The waste PP underwent excessive degradation as the mechanical strength properties such as tensile, flexural and impact strengths were reduced drastically. On the other hand, WPP containing varying proportions of EPDM and carbon black showed better retention of strength properties. The percentage degree of crystallinity has been unusually increased after the environmental degradation due to chemi-crystallization. The impact-modified WPP which contains carbon black retained the processability even after the environmental aging. After aging, the non-stabilized systems were shown extensive change, whereas the structural integrity has been well retained of the toughened WPP containing carbon black as was evident from SEM and optical photomicroscopy.     

Hydrogenated silicon oxycarbonitride films. Part II. Physicochemical and functional properties

The optical, and electrophysical characteristics of hydrogenated silicon oxycarbonitride films synthesized by the plasma enhanced chemical vapor decomposition of the mixtures of 1,1,1,3,3,3-hexamethyldisilazane with oxygen and nitrogen in the temperature range of 373–973 K have been studied. It has been shown that the obtained films are highly transparent (transmittance is ～92–99%) in the UV, visible, and IR ranges of the spectrum; they have refractive indices in the range of 1.43–2.25, a low reflection coefficient of visible light (nearly 3%), and low dielectric permittivity.     

Electricity System Reliability Issues During Energy System Transformation

Energy system transformation in the electric energy industry encompasses a broad range of changes in how primary energy is produced, transported, converted, priced, and delivered to consumers. Minnesota Power (ALLETE) is responding to these changes by implementing strategies like our EnergyForward resource strategy. EnergyForward describes the transition to a diverse and balanced generation portfolio that meets customers' desires for clean, safe, flexible, and affordable electricity.     

Regioselective Synthesis of Naphtho‐fused Heterocycles via Palladium(0)‐Catalyzed Tandem Reaction of N‐Tosylhydrazones

We have developed a palladium(0)‐catalyzed tandem process which involves the cross‐coupling reaction of N‐tosylhydrazones with dibromide compounds followed by a sequence of intramolecular 5‐exo‐trig, 3‐exo‐trig cyclization, ring opening, and β‐hydride elimination to produce 6‐endo‐trig cyclized products. The strategy was successfully applied for the regioselective synthesis of substituted benzo[b]naphtho[2,1‐d]thiophenes, naphtho[1,2‐b]benzofurans, and benzo[a]carbazoles in moderate to excellent yields.

     

A Mixed Ligand Approach for the Asymmetric Hydrogenation of 2‐Substituted Pyridinium Salts

Herein we describe a new methodology for the asymmetric hydrogenation (AH) of 2‐substituted pyridinium salts. An iridium catalyst based on a mixture of a chiral monodentate phosphoramidite and an achiral phosphine was shown to hydrogenate N‐benzyl‐2‐arylpyiridinium bromides to the corresponding N‐benzyl‐2‐arylpiperidines with full conversion and good enantioselectivity. The mechanism of the reaction under optimized conditions was investigated via kinetic measurements and isotopic labeling experiments. Our study suggests that the hydrogenation starts with a 1,4‐hydride addition and that the enantiodiscriminating step involves the reduction of an iminium intermediate.