Cathode, graphite

Graphite, bulk Graphite cathodes Graphite electrodes... 

Hydrocarbon, typically natural gas, is fed into the reactor to intersect with an electric arc stmck between a graphite cathode and a metal (copper) anode. The arc temperatures are in the vicinity of 20,000 K inducing a net reaction temperature of about 1500°C. Residence time is a few milliseconds before the reaction temperature is drastically reduced by quenching with water. Just under 11 kWh of energy is required per kg of acetylene produced. Low reactor pressure favors acetylene yield and the geometry of the anode tube affects the stabiUty of the arc. The maximum theoretical concentration of acetylene in the cracked gas is 25% (75% hydrogen). The optimum obtained under laboratory conditions was 18.5 vol % with an energy expenditure of 13.5 kWh/kg (4). 

The electrolysis is conducted at 90—95°C and an anode current density of about 50 120 A/m when using lead alloy anodes and lead cathodes. Using graphite electrodes, the current density is from 70 100 A/m using titanium anodes and graphite cathodes, the current density is 50 80 A/m (82). 

Electrolysis —2.9 V, DMF, R4N X , 70-80% yield or Pd/graphite cathode, MeOH, AcOH, 2.5% NaCl04 (0.5 mol/L), 99% yield.Benzyl ethers and tosylates are stable to these conditions, but benzyl esters are cleaved. 

The CNTs were prepared by the group at EPF in Lausanne [10] following the method of Ebbesen et al. [ll]. A 100 A, 20 V dc arc between a 6.5 mm diameter graphite anode and a 20 mm graphite cathode is sustained in a 6.7x10 Pa helium atmosphere for about twenty min. Nanotubes were found on the cathode, where they were encapsulated in a cylindrical 1 cm long shell. The shell was cracked and the powdery soot-like deposit extracted. The powder was then... 

Figure 21-4 shows a schematic representation of an electrolysis cell for aluminum production. An external electrical potential drives electrons into a graphite cathode, where Al ions are reduced to A1 metal ... 

Shigehara K, Anson EC. 1982. Electrocatal3dic activity of three iron porphyrins in the reduction of dioxygen and hydrogen peroxide at graphite cathodes. J Phys Chem 86 2776. 

Chlorine, when contaminated with C02 or other relatively inert gases, can, in principle, be purified by electrochemical concentration. At a graphite cathode, Cl2 is reduced to chloride ions ... 

In the conception of Bjorkman [35], an extended area graphite cathode is comprised of a packed, flow-through bed. The electrolyte, in this case aqueous HC1, was immobilized in an asbestos matrix. Chloride ions are transported to the graphite anode where pure Cl2 is liberated. 

Battery technology has developed enormously in recent years. One of the most useful types of batteries is known as the lithium battery, but there are actually several designs only one of which will be described. In one of the types, the anode is constructed of lithium or a lithium alloy hence the name. A graphite cathode is used, and the electrolyte is a solution of Li[AlCl4] in thionyl chloride. At the anode, lithium is oxidized,... 

Balbach A variation of the Moebius process for electrolytically removing gold from silver, in which the anodes are placed horizontally in wooden trays lined with canvas to retain the slimes. The silver is deposited as crystals on graphite cathodes at the base of the cell. Invented by E. Balbach. See also parting, Parkes, Thum, Wohlwill. 

Acetone - Pinacol U.S., Japan, Eurpoe - modified graphite cathode Pb cathode in acid... 

One synthesis approach that does not rely on CNT formation from the gas phase is molten salt synthesis. The reactor consists of a vertically oriented quartz tube that contains two graphite electrodes (i.e. anode is also the crucible) and is filled with ionic salts (e.g. LiCl or LiBr). An external furnace keeps the temperature at around 600 °C, which leads to the melting of the salt. Upon applying an electric field the ions penetrate and exfoliate the graphite cathode, producing graphene-type sheets that wrap up into CNTs on the cathode surface. Subsequently, the reactor is allowed to cool down, washed with water, and nanocarbon materials are extracted with toluene [83]. This process typically yields 20-30 % MWCNTs of low purity. 

A dry cell contains a zinc anode and an inert graphite cathode, as shown in Figure 11.7. The electrolyte is a moist paste of manganese(IV) oxide, Mn02, zinc chloride, ZnGh, ammonium chloride, NH4CI, and carbon black, C(s), also known as soot. 

The D-size dry cell battery is shown whole, and cut in two. The anode is the zinc container, located just inside the outer paper, steel, or plastic case. The graphite cathode runs through the centre of the cylinder. 

It is commercially advantageous to operate cells with no diaphragm since the cell diaphiagm is the weakest point in the system. Achievement of this aim rests upon finding an anode reaction that destroys neither the substrate nor the product. Russian workers [63] showed that up to 90 % yields of adiponitrile can be obtained at a graphite cathode in an undivided cell with an iron oxide anode, provided that phosphate and tetraalkylammomum ions are present. Further research contributions from Monsanto, BASF and Japanese companies led to the present system for hydrodimerization of acrylonitrile using an undivided cell [64,65]. 

In the second cell, known as the decomposer cell, a graphite cathode is used whde sodium amalgam serves as the anode. Water reacts with the sodium metal of the amalgam in the decomposer ... 

Room temperature sensors based on a V2O5-graphite cathode and a polyethylene oxide-based electrolyte were reported by Sathiyamoorthi etal. [55]. The gas is sampled through the porous cathode and for both chlorine and fluorine good sensitivity and rapid response times were observed. 

Miller and his co-workers60) reported surprisingly high optical yields, close to 50 %, in the reduction of 2-acetylpyridine in the presence of strychnine. They also prepared chemically modified electrodes with optically active amino acids and attempted asymmetric induction in both reduction and oxidation61 . The best optical yield, only 14.5 %, seemed to be obtained in the reduction of 4-acetyl-pyridine on a graphite cathode modified with (S)-phenylalanine methyl ester. 

This system, commonly known as the mercury cell , is based on an amalgamated zinc anode, a concentrated aqueous potassium hydroxide electrolyte - saturated with zincate ion by zinc oxide - and a mercuric oxide/graphite cathode ... 

FIGURE 18.18 An elec- trolytic cell for production of aluminum by the Hall-Heroult process. Molten aluminum metal forms at the graphite cathode that lines the cell. Because molten aluminum is more dense than the Al203-Na3AlFg mixture, it collects at the bottom of the cell and is drawn off periodically. 

Hall-Heroult cell The electrolysis cell in which aluminium is extracted from purified bauxite dissolved in molten cryolite at 900°C. This cell has both a graphite anode and a graphite cathode. 

The formation of TAA-metals by cathodic reduction of TAA+ cations at several solid electrodes has recently been reported n. These coloured materials were observed at Hg, Pb, Sn, Bi and Sb cathodes, while Pt and Cr were unreactive. They all act as reducing agents and seem to incorporate both TAA+ and metal atoms (from the cathode) into their structure. They behave similarly and are probably related to the compounds resulting from the reduction of TAA+ at graphite cathodes 2). The best known and most extensively studied TAA-metals are those generated at mercury cathodes. They are also the likely catalysts for the organic electroreductions described below. Because TAA-mercury may be pervasively involved in the preparative reductions which are the topic of this review, the next few paragraphs provide information about their composition and evidence for their involvement as catalysts. 

White lead processes which have been employed on an industrial scale are as follows In the Gardner1 process, worked at Millwall, lead sheet anodes are packed between graphite cathodes. The lead and graphite are connected by strips of tin so that when the acetic acid vapours reach the metal, electrical action takes place and the conversion into white lead is greatly accelerated. The process is similar to the ordinary chemical one, but the time required for the formation of a batch of white lead is reduced from fourteen weeks to about five weeks. 

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