Anode electrochemical cell

A system consisting of aqueous PtCl " as the catalyst and phospho-molybdic acid as the redox mediator in a carbon cloth anode electrochemical cell, electrocatalytically hydroxylated p-toluenesulfonic acid according to the equation [24] ... 

The concept of the reversed fuel cell, as shown schematically, consists of two parts. One is the already discussed direct oxidation fuel cell. The other consists of an electrochemical cell consisting of a membrane electrode assembly where the anode comprises Pt/C (or related) catalysts and the cathode, various metal catalysts on carbon. The membrane used is the new proton-conducting PEM-type membrane we developed, which minimizes crossover. 

A gravimetric method in which the signal is the mass of an electrodeposit on the cathode or anode in an electrochemical cell. 

In electrogravimetry the analyte is deposited as a solid film on one electrode in an electrochemical cell. The oxidation of Pb +, and its deposition as Pb02 on a Pt anode is one example of electrogravimetry. Reduction also may be used in electrogravimetry. The electrodeposition of Cu on a Pt cathode, for example, provides a direct analysis for Cu +. 

Also, by convention, potentiometric electrochemical cells are defined such that the indicator electrode is the cathode (right half-cell) and the reference electrode is the anode (left half-cell). 

Shorthand Notation for Electrochemical Cells Although Figure 11.5 provides a useful picture of an electrochemical cell, it does not provide a convenient representation. A more useful representation is a shorthand, or schematic, notation that uses symbols to indicate the different phases present in the electrochemical cell, as well as the composition of each phase. A vertical slash ( ) indicates a phase boundary where a potential develops, and a comma (,) separates species in the same phase, or two phases where no potential develops. Shorthand cell notations begin with the anode and continue to the cathode. The electrochemical cell in Figure 11.5, for example, is described in shorthand notation as... 

What are the anodic, cathodic, and overall reactions responsible for the potential in the electrochemical cell shown here Write the shorthand notation for the electrochemical cell. 

Potentiometric electrochemical cells are constructed such that one of the half-cells provides a known reference potential, and the potential of the other half-cell indicates the analyte s concentration. By convention, the reference electrode is taken to be the anode thus, the shorthand notation for a potentiometric electrochemical cell is... 

Equations 11.19-11.21 are defined for a potentiometric electrochemical cell in which the pH electrode is the cathode. In this case an increase in pH decreases the cell potential. Many pH meters are designed with the pH electrode as the anode so that an increase in pH increases the cell potential. The operational definition of pH then becomes... 

Identify the anode and cathode for the following electrochemical cells, and write the oxidation or reduction reaction occurring at each electrode. 

Ethylene glycol can be produced by an electrohydrodimerization of formaldehyde (16). The process has a number of variables necessary for optimum current efficiency including pH, electrolyte, temperature, methanol concentration, electrode materials, and cell design. Other methods include production of valuable oxidized materials at the electrochemical cell s anode simultaneous with formation of glycol at the cathode (17). The compound formed at the anode maybe used for commercial value direcdy, or coupled as an oxidant in a separate process. 

Anodic Oxidation. The abiUty of tantalum to support a stable, insulating anodic oxide film accounts for the majority of tantalum powder usage (see Thin films). The film is produced or formed by making the metal, usually as a sintered porous pellet, the anode in an electrochemical cell. The electrolyte is most often a dilute aqueous solution of phosphoric acid, although high voltage appHcations often require substitution of some of the water with more aprotic solvents like ethylene glycol or Carbowax (49). The electrolyte temperature is between 60 and 90°C. 

Electrochemical Process. Several patents claim that ethylene oxide is produced ia good yields ia addition to faradic quantities of substantially pure hydrogen when water and ethylene react ia an electrochemical cell to form ethylene oxide and hydrogen (206—208). The only raw materials that are utilized ia the ethylene oxide formation are ethylene, water, and electrical energy. The electrolyte is regenerated in situ ie, within the electrolytic cell. The addition of oxygen to the ethylene is activated by a catalyst such as elemental silver or its compounds at the anode or its vicinity (206). The common electrolytes used are water-soluble alkah metal phosphates, borates, sulfates, or chromates at ca 22—25°C (207). The process can be either batch or continuous (see Electrochemicalprocessing). 

A problem common to electrochemical cells is the analyzer can fail (degradation of the anode material and electrolyte or loss of sensor sensitivity), but still indicate a safe oxidant level when in reality it may not be so. Adherence to the manufacturer s recommendation as to how... 

There are two principal methods of applying cathodic protection, viz. the impressed current technique and the use of sacrificial anodes. The former includes the structure as part of a driven electrochemical cell and the latter includes the structure as part of a spontaneous galvanic cell. 

Half-cell one half of an electrochemical cell, comprising one electrode (anode or cathode) and its immediate electrolyte (anolyte or catholyte). 

It is always true that in an electrochemical cell, anions move to the anode cations move to the cathode. 

Although iodides are more reactive than bromides, 2-(trifluoro-methyl)pyridine was obtained in 95% yield from 2-bromopyridine and CF3Br using an undivided electrochemical cell, DMF, and a sacrificial copper anode. CF3Cu was the reactive intermediate (92CC53). Photochem-... 

The corrosion of steel or other metals in a boiler plant system takes place when an electrochemical cell is established. This occurs when two different metals (anode and cathode) are coupled together in water, which acts as the electrolyte in any steam-water circuit. 

In an electrochemical cell, electrical work is obtained from an oxidation-reduction reaction. For example, consider the process that occurs during the discharge of the lead storage battery (cell). Figure 9.3 shows a schematic drawing of this cell. One of the electrodes (anode)q is Pb metal and the other (cathode) is Pb02 coated on a conducting metal (Pb is usually used). The two electrodes are immersed in an aqueous sulfuric acid solution. 

Measurement of E° and Activities Electrochemical cells can be constructed to measure E° and thermodynamic properties such as K, AG, AH, AS, A V, and ACP for a reaction. Consider as an example the cell shown schematically in Figure 9.4.x The cathode consists of an Ag metal rod coated with AgCl(s). The anode is a Pt metal rod around which H2(g) is bubbled. The two electrodes are... 

Figure 1. Relative cost of fluorine as a function of current based on a four-anode callandria cell using 20 x 20 cm anodes 8000 A corresponds to 300 mA cm-2. (Reprinted from G. L. Bauer and W. V. Childs, J. Electrochem. Soc. 142, 2286-2290,1994. Reproduced with permission of The Electrochemical Society, Inc.)...

The electrochemical cell consists of high surface area Pd/C or unsupported Pd-Ru cathodes interfaced to Nafion with a Pt-black/H2 counter electrode. The cell configuration, as well as the reactions taking place on the anode and the cathode are the following ... 

The ammonium polysulfide, (NH4)2SX (with x=2 to 6) is produced in an electrochemical cell where aqueous ammonium sulfide, (NH4)2S, solution is supplied as electrolyte. The cell comprises an anode and a gas diffusion carbon cathode over which gaseous 02 is supplied in contact with the electrolyte.11 The cell operated continuously at pressures up to 60 bar. The applied potential, UWc> was 0.01 to 5 V. Pronounced electrochemical promotion behaviour was observed at Uwc values as low as 0.02 V with a current 1=0.5 A. 

An electrochemical cell in which electrolysis takes place is called an electrolytic cell. The arrangement of components in electrolytic cells is different from that in galvanic cells. Typically, the two electrodes share the same compartment, there is only one electrolyte, and concentrations and pressures are far front standard. As in all electrochemical cells, the current is carried through the electrolyte by the ions present. For example, when copper metal is refined electrolytically, the anode is impure copper, the cathode is pure copper, and the electrolyte is an aqueous solution of CuS04. As the Cu2f ions in solution are reduced and deposited as Cu atoms at the cathode, more Cu2+ ions migrate toward the cathode to take their place, and in turn their concentration is restored by Cu2+ produced by oxidation of copper metal at the anode. 

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