Electrode additives, carbons

Zinc/carbon (Leclanchc cell) Electrode additive, current collector... 

Of practical importance is the contribution that is made by carbonaceous materials as an additive to enhance the electronic conductivity of the positive and negative electrodes. In other electrode applications, carbon serves as the electrocatalyst for electrochemical reactions and/or the substrate on which an electrocatalyst is located. In... 

Perhaps the first practical application of carbonaceous materials in batteries was demonstrated in 1868 by Georges Le-clanche in cells that bear his name [20]. Coarsely ground MnO, was mixed with an equal volume of retort carbon to form the positive electrode. Carbonaceous powdered materials such as acetylene black and graphite are commonly used to enhance the conductivity of electrodes in alkaline batteries. The particle morphology plays a significant role, particularly when carbon blacks are used in batteries as an electrode additive to enhance the electronic conductivity. One of the most common carbon blacks which is used as an additive to enhance the electronic conductivity of electrodes that contain metal oxides is acetylene black. A detailed discussion on the desirable properties of acetylene black in Leclanche cells is provided by Bregazzi [21], A suitable carbon for this application should have characteristics that include (i) low resistivity in the presence of the electrolyte and active electrode material, (ii) absorption and retention of a significant... 

About 20 amalgam-forming metals, including Pb, Sn, Cu, Zn, Cd, Bi, Sb, Tl, Ga, In and Mn, are easily measurable by stripping strategies (ASV and PSA) based on cathodic deposition onto mercury electrodes. Additional metals, such as Se, Hg, Ag, Te and As are measurable at bare solid electrodes such as carbon or gold. 

Lintz and co-workers have investigated the effect of a bismuth additive in metal electrodes for carbon monoxide oxidation56 and have also used SEP to study carbon monoxide oxidation.57... 

Carbon electrodes — Carbon is selected for many electrochemical applications because of its good electrical and thermal conductivity, low density, adequate corrosion resistance, low thermal expansion, low elasticity, and high purity In addition, carbon materials can be produced in a variety of structures, such as powders, fibers, large blocks, thin solid and porous sheets, nanotubes, fullerenes, graphite, and diamond. Furthermore, carbon materials are readily available and are generally low-cost materials. 

Carbon and graphite are used in batteries as electrodes or as additives in order to enhance the electronic conductivity of the electrodes. As electrodes, graphites and disordered carbons reversibly insert lithium, and hence they may serve as the anode material in -> lithium batteries. Graphitic carbons intercalate lithium in a reversible multi-stage process up to LiC6 (a theoretical capacity of 372 mAh g-1) and are used as the main anode material in commercial rechargeable Li ion batteries. As additives, carbon and graphite can be found in most of... 

What, if any, relevance do such results have when predicting the influence of adsorbed bismuth on the CO of supported platinum nanoparticle catalysts In order to test the transferrability of results obtained on single crystals to practical fuel-cell anode catalysts, a series of experiments was performed [77] on a gas diffusion electrode of carbon-supported platinum (0.22 mg cm ) catalyst (Johnson Matthey). Figure 10 shows the results of polarization measurements for hydrogen oxidation at clean and bismuth-modified (0.65-ML) catalysts. In order to establish the CO tolerance of the electrodes, in addition to experiments involving pure H2,... 

The use of carbon materials in electrochemical systems started in 19 century, when carbon electrodes replaced copper ones in Volta batteries and Pt electrodes in Grove Cells. Nowadays, carbon materials are used in many electrochemical applications because of their high electrical and thermal conductivity, low density, high corrosion resistance, low elasticity adequate strength and high purity. In addition, carbon materials are available in a variety of physical structures (powders, fibres, cloths), have a low cost and can be fabricated into composite structures. 

In the above reactions, the oxidation process takes place in the anode electrode where the methanol is oxidized to carbon dioxide, protons, and electrons. In the reduction process, the protons combine with oxygen to form water and the electrons are transferred to produce the power. Figure 9-1 is a reaction scheme describing the probable methanol electrooxidation process (steps i-viii) within a DMFC anode [1]. Only Pt-based electrocatalysts show the necessary reactivity and stability in the acidic environment of the DMFC to be of practical use [2], This is the complete explanation of the anodic reactions at the anode electrode. The electrodes perform well due to the presence of a ruthenium catalyst added to the platinum anode (electrode). Addition of ruthenium catalyst enhances the reactivity of methanol in fuel cell at lower temperatures [3]. The ruthenium catalyst oxidizes carbon monoxide to carbon dioxide, which in return helps methanol reactivity with platinum at lower temperatures [4]. Because of this conversion, carbon dioxide is present in greater quantity around the anode electrode [5]. 

In addition, carbon nanotube samples which were grown in a horizontal quartz tube reactor placed in a furnace by the reaction technique using a xylene-ferrocene mixture by means of a method described in details in papers [23,24] were examined. In our investigations of adsorbed liquids and smface porosity parameters of nanotubes, we used carbon products obtained by two methods a DC electric arc was generated between graphite electrodes and hydrocarbon vapour was thermally decomposed in the presence of a catalyst (N-1 sample). This material was sonicated in a water/ethanol mixture for 30 min (N-2 sample). 

The active substance of the positive electrode is the polymer of fluorinated carbon with the overall formula of (CFj ) . As a rule, subscript x in this formula is close to unity, polymerization degree n exceeds 1(X)0. The polymer of fluorinated carbon is a layered compound obtained by fluorination of carbon (graphitized or nongraphitized) in the form of a powder, fibers, or even fabrics by elementary fluorine at the temperatures of 350 - 600°C. As polyfluorocarbon is characterized by negligible electron conductivity, a certain amount of a conductive additive (carbon black) is introduced into the active mass of cathodes. Elementary carbon is formed in the course of discharge and the overall conductivity of the cathode increases. 

Batteries of this type have been developed with film, tablet, and cylindrical designs. In the first type, the electrolyte film is applied onto the metal anode or cathodic current collector by sputtering or vaporization. The tablet and cylindrical batteries designed for comparatively high drain rates employ porous electrodes manufactured by pressing a mixture of the powders of the active materials (silver or polyiodide), electrolyte, and conductive additive (carbon black, etc.). 

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