876 research outputs found
Phosphorus Doping on FeNC and CNx Catalysts in Oxygen Reduction Reaction in PEM Acidic Media
Fuel cells catalysts are being researched to achieve higher activity and lower costs for oxygen reduction reaction. Iron nitrogen carbon (FeNC) and nitrogen carbon (CNx) catalysts hold promising potential for being catalytically active at low costs. Phosphorus was doped on both FeNC and CNx catalysts to improve activity because of phosphorus’ elemental properties. The specific amount of phosphorus doping was also researched for activity optimization. Triphenylphosphine was used as a phosphorus dopant and incorporated in the ballmilling step for both FeNC and CNx synthesis. Activity testing using Rotating Disk Electrode (RDE) apparatus with glassy carbon working electrode was done on both FeNC and CNx catalysts with and without P-doping. The CV curves obtained from the testing in phosphoric acid acidic mediums were analyzed via onset or half-wave potentials to determine the catalytic activities. The results showed that P-doping did not positively affect the activity of FeNC but did positively affect the activity of CNx. The results suggest the different effectiveness of P-doping on different carbon structured catalysts.A three-year embargo was granted for this item.Academic Major: Chemical Engineerin
Dissociating stable nitrogen molecules under mild conditions by cyclic strain engineering
All quiet on the nitrogen front. The dissociation of stable diatomic nitrogen molecules (N-2) is one of the most challenging tasks in the scientific community and currently requires both high pressure and high temperature. Here, we demonstrate that N-2 can be dissociated under mild conditions by cyclic strain engineering. The method can be performed at a critical reaction pressure of less than 1 bar, and the temperature of the reaction container is only 40 degrees C. When graphite was used as a dissociated N* receptor, the normalized loading of N to C reached as high as 16.3 at/at %. Such efficient nitrogen dissociation is induced by the cyclic loading and unloading mechanical strain, which has the effect of altering the binding energy of N, facilitating adsorption in the strain-free stage and desorption in the compressive strain stage. Our finding may lead to opportunities for the direct synthesis of N-containing compounds from N-2
Development of lanthanum nickelate as a cathode for use in intermediate temperature solid oxide fuel cells
The performance of lanthanum nickelate, La2NiO4+δ (LNO), as a cathode in IT-SOFCs with the electrolyte cerium gadolinium oxide, Ce0.9Gd0.1O2−δ (CGO), has been investigated by AC impedance spectroscopy of symmetrical cells. A significant reduction in the area specific resistance (ASR) has been achieved with a layered cathode structure consisting of a thin compact LNO layer between the dense electrolyte and porous electrode. This decrease in ASR is believed to be a result of contact at the electrolyte/cathode boundary enhancing the oxygen ion transfer to the electrolyte. An ASR of 1.0 Ω cm2 at 700 °C was measured in a symmetrical cell with this layered structure, compared to an ASR of 7.4 Ω cm2 in a cell without the compact layer. In addition, further improvements were observed by enhancing the cell current collection and it is anticipated that a symmetrical cell consisting of a layered structure with adequate current collection would lower these ASR values further
Solid-phase combustion in the "titanium-carbon" system with high content of inert binder
The effect of mechanical activation on combustion process after processing in the strain energy ballmilling of "Ti - C" powder system was investigated. Embodiments of self-propagating high temperature synthesis(SHS) in powder mixtures with inert titanium binder up to 90 vol.% are describes
LiMnPO4 olivine as a cathode for lithium batteries
The olivine structured mixed lithium-transition metal phosphates LiMPO4 (M = Fe, Mn, Co) have attracted
tremendous attention of many research teams worldwide as a promising cathode materials for lithium batteries. Among
them, lithium manganese phosphate LiMnPO4 is the most promising considering its high theoretical capacity and
operating voltage, low cost and environmental safety. Various techniques were applied to prepare this perspective cathode
for lithium batteries. The solution based synthetic routes such as spray pyrolysis, precipitation, sol-gel, hydrothermal and
polyol synthesis allow preparing nanostructured powders of LiMnPO4 with enhanced electrochemical properties, which is
mostly attributed to the higher chemical homogeneity and narrow particle size distribution of the material. Up-to-date, the
LiMnPO4/C composites prepared by the spray pyrolysis route have the best electrochemical performance among the
reported in the literature
Caffeine-derived noble carbons as ball milling-resistant cathode materials for lithium-ion capacitors
Energy consumption is a growing phenomenon in our society causing many negative effects such as global warming. There is a need for the development of new sustainable materials for energy storage. Carbons are materials derivable from biowaste that can rather easily store energy due to their high conductivity and surface area. However, their large-scale processing is challenging as derived materials can be rather heterogeneous and homogenization requires ball milling, a process that can damage carbons in the process of oxidation. Herein, we have prepared caffeine-derived noble nitrogen-doped carbon that withstands the ball milling process without significant oxidation. Additionally, it performs extraordinarily as a cathode material for lithium-ion capacitors, making it an attractive biowaste-derived alternative to commercial heavy metal cathodes
Analisis Pengaruh Mechanical Milling Menggunakan Planetary Ball Milling terhadap Struktur Kristal dan Struktur Mikro Senyawa Libob
ANALISIS PENGARUH MECHANICAL MILLING MENGGUNAKAN PLANETARY BALL MILLING TERHADAP STRUKTUR KRISTAL DAN STRUKTUR MIKRO SENYAWA LiBOB. Telah dilakukan pembuatan senyawa Lithium bis Oksalat Borat (LiBOB) dari bahan baku LiOH, asam oksalat dan asam borat dengan metode reaksi padat padat. Serbuk yang dihasilkan dilanjutkan penghalusan menggunakan planetary ball milling dengan durasi milling di buat bervariasi (4 jam, 5 jam, 6 jam, 10 jamdan 13 jam). Serbuk LiBOB yang dihasilkan dianalisis menggunakan X-Ray Diffractometer (XRD) untuk mengetahui fasa yang terbentuk, struktur kristal dan ukuran kritalitnya. Hasil identifikasi senyawa LiBOB dengan XRD berupa pola difraksi kemudian dianalisismenunjukkan terbentuknya 2 fasa yaitu fasa LiB(C2O4)2 dan fasa LiB(C2O4)2.(H2O) dengan sistem kristal orthorhombic. Kerapatan atom paling kecil pada senyawa LiBOB dengan durasi milling 5 jam dan volum unit sel paling besar pada senyawa LiBOB dengan durasi milling 10 jam. Diameter ukuran kristalit berubah seiring dengan durasi milling, sedang regangan kisi terendah pada durasi milling 4 jam dan tertinggi pada durasi milling 5 jam. Durasi milling 5 jam adalah paling bagus dimana pada fasa ini memberikan ruang paling besar pada tiap unit sel dan regangan kisi paling besar sehingga dapat memudahkan ruang gerak transfer ion Li pada baterai Lithium. Senyawa LiBOB hasil sintesis mempunyai sistem kristal yang teratur. Tingkat keteraturan kristal yang dihasilkan ditunjukan dengan perhitungan indeks kristalinitas yang tinggi
Cellulase Production by Aspergillus flavus Linn Isolate NSPR 101 fermented in sawdust, bagasse and corncob
Bagasse, corncob and sawdust were used as lignocellulosic substrates for the production of cellulase enzyme using Aspergillus flavus after ballmilling and pretreatment with caustic soda. From the fermentation studies, sawdust gave the best result with an enzyme activity value of 0.0743IU/ml while bagasse and corncob gave 0.0573IU/ml and 0.0502IU/ml respectively. The three lignocellulosics gave their maximum enzyme activities at about the twelfth hour of cultivation, suggesting that the 12th hour is the optimum time when the enzyme may be harvested.
(African Journal of Biotechnology: 2003 2(6): 150-152
Application of Thermal Response Measurements to Investigate Enhanced Water Adsorption Kinetics in Ball-Milled C2N-Type Materials
Sorption-based water capture is an attractive solution to provide potable water in arid regions. Heteroatom-decorated microporous carbons with hydrophilic character are promising candidates for water adsorption at low humidity, but the strong affinity between the polar carbon pore walls and water molecules can hinder the water transport within the narrow pore system. To reduce the limitations of mass transfer, C2N-type carbon materials obtained from the thermal condensation of a molecular hexaazatriphenylene-hexacarbonitrile (HAT-CN) precursor were treated mechanochemically via ball milling. Scanning electron microscopy as well as static light scattering reveal that large pristine C2N-type particles were split up to a smaller size after ball milling, thus increasing the pore accessibility which consequently leads to faster occupation of the water vapor adsorption sites. The major aim of this work is to demonstrate the applicability of thermal response measurements to track these enhanced kinetics of water adsorption. The adsorption rate constant of a C2N material condensed at 700 °C remarkably increased from 0.026 s−1 to 0.036 s−1 upon ball milling, while maintaining remarkably high water vapor capacity. This work confirms the advantages of small particle sizes in ultramicroporous materials on their vapor adsorption kinetics. It is demonstrated that thermal response measurements are a valuable and time-saving method to investigate water adsorption kinetics, capacities, and cycling stability
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