Preparation of electrodes

Direct Chemical or Electrochemical Deposition of the Disperse Catalyst This method of direct deposition from a solution of its salt on a suitable conducting substrate is simpler and more practical than the preparation of electrodes from the hnished powders. It has the merit of being able to provide better contact between the catalyst and substrate, and multicomponent metal catalysts can be deposited from a solution containing a mixture of salts of several metals. 

The second most widely used noble metal for preparation of electrodes is gold. Similar to Pt, the gold electrode, contacted with aqueous electrolyte, is covered in a broad range of anodic potentials with an oxide film. On the other hand, the hydrogen adsorption/desorption peaks are absent on the cyclic voltammogram of a gold electrode in aqueous electrolytes, and the electrocatalytic activity for most charge transfer reactions is considerably lower in comparison with that of platinum. 

Surfaces of finely divided nickel also promote the formation of aniline. A practical route to tlie preparation of electrodes coaled with a finely divided metal involves electroplating nickel onto a cathode from a solution containing a suspension of finely divided Raney nickel (Ni 50% A1 50%) or Devarda copper alloy (Cu 50% A1 45% Zn 5%), Some alloy particles stick to the cathode surface which is then activated by leaching out the aluminium using hot aqueous sodium hydroxide... 

The preparation of electrodes and M EAs have been described elsewhere [15]. FC tests (determination of the cell voltage E and power density P versus the current density j) were carried out in a single DEFC with 5 or 25 cm geometric surface area electrodes using a Globe Tech test bench, purchased from ElectroChem (USA) (Figure 1.12). 

Preparation of Electrodes Modified by Polycyanometalates and their Applications... 

There are numerous advantages of amperometric detection on-chip. These include (1) the detector has a minimal dead volume (2) preparation of electrodes (working) is compatible with the planar micromachining technology (3) the electrodes can be miniaturized without compromising LOD and (4) the EC detection has a short response time [746]. 

Preparation of Electrodes. The Ag/AgBr and Ag/AgI electrodes were prepared by anodic electrolysis of the appropriate sodium salt solution (IN) at 6.5 ma. per sq. cm. for 5 minutes. The two electrodes to be coated were connected and dipped into the solution a wire of pure silver was used as the cathode. In the case of the Ag/AgCl electrode IN HC1 was used. Just after preparation the electrodes were immersed in the appropriate halide solution (10-3 M). The Ag/Ag halide electrodes prepared in this manner showed a difference of potential of 0.3 to 0.5 mv. in the presence of 10 5 M solution of sodium halide. This potential will be referred to as rest or nonflow potential. 

A large number of protoeols for the preparation of electrodes based on the use of CNTs have been proposed. As in the case of pretreatments, in general, the seleetion of a given scheme will depend on the system under investigation. For instance, composites are easier to obtain from the point of view of the preparation time, while some others like the modification of GCE with CNTs dispersed in Nafion, are very eonvenient because in one step it is possible not only to immobilize the CNTs but also to have a barrier for interferents or a platform for further modifications. 

Preparation of Electrodes of Nanometer-Scale Thin Films of Platinum Group Metals and Alloys... 

Preparation of Electrodes-Modified with Sulfonate-Functionalized Polyanilines... 

Figure 1 - Fe-oxides identified by SEM analysis from the received roasted gold ore sample Material and Preparation of Electrodes...

Hence, the activation overpotential can be considerably decreased by appropriate preparation of electrode surface morphology, especially by formation of disperse deposits at low level of coarseness. Obviously, the roughness factor can be increased many times in real situations. It is well known that the surface morphology exerts a marked influence on the electrocatalytic activity of an electrode.73 At a microscopic level, the existence of pores, crevices, microcavities, etc. favors the increase of the electrodic surface area, though... 

Electroless deposition of the catalytic Pt or Pt-Ru layer was proposed for the preparation of electrodes in microdirect methanol fuel cells.53 A porous silicone substrate is prepared by the anodic etching in HF-ethanol-water (1 1 1) solution. After the etching, at the surface of porous silicon substrate, a thin film of titanium is sputtered and then a film of Pt or Pt-Ru alloy with thickness of about 150-200 nm was electroless deposited. The electrodes prepared in this way helped in minimization of the fuel cell size and increased the reactive area of the catalyst over the silicon electrode surface. 

These results suggest some factors for the preparation of electrodes with electron-transfer ability, (i) There is an optimum thickness of the coated polymer film for the electron-transfer reaction, (ii) The polymer matrix should be flexible. Otherwise, the matrix retards the diffusion of a counter ion and suppresses the effective collision between redox sites. (iii) A hydrophilic but uncharged polymer domain is suitable for the mass-transfer process in catalysis. A series of polymer complex coated electrodes were prepared as interfacial catalysts (16), one example is given below. 

Compounds of cerium and its relatives find numerous suggested uses. The pyrophoric metal known as " kunheim is a mixture of the hydrides of the cerium earth metals with magnesium and aluminium. Cerium fluoride and titanofluoride have been used in the preparation of electrodes for the flaming arc light. By impregnating the carbon electrodes with the cerium salts a more intense light is obtained and the arc bums evenly and quietly. Steam declares 1 that 300 tons of ceria are used annually for this purpose. 

Preparation of Electrodes with Preferred Crystallographic Orientation by Platinization... 

Figure 41.1 la presents one layout of this integrated system as well as a typical electropherogram obtained on this device (Figure 41.11b). In addition to enhanced chip-to-chip repeatability, the use of integrated electrodes improved the signal-to-noise ratio. The use of toner masks for preparation of electrodes can be also extended to other EC modes such as amperometry, voltammetry, and potentiometry. Furthermore, the use of copper tapes as electrodes is limited to the classical format (antiparallel design), while the use of toner masks allows one to investigate different electrode design for C D.

Electropolymerization techniques have also been popular for the preparation of electrodes modified by thin films of Schiff-base metallopolymers for prospective electrocatalytic, chemical sensing, and electrochromic applications [79-85]. In... 

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