Carbon powder anodes

Now let us consider a model for a SC device that comprises two electrodes (anode and cathode), each of them being electrically connected to a current collector fabricated of A1 foil. Let two of such collectors have a certain thickness of SAi- As an electrode material, an activated carbon powder is considered below. Anode and cathode are interposed with a separator of thickness Ss. The electrodes and separator are impregnated with electrolyte. In this paper we mostly focus on the optimization of SC performance by varying the electrode thickness, while some other effects will briefly be considered in the next section. 

Another important point regarding the fabrication process of MPLs is the fact that, typically, when carbon fiber paper is used as the DL, the MPL is coated just on one surface of the CLP. However, when a carbon cloth is used, a homogeneous water suspension of carbon powder and PTFE is filtered under vacuum onto both faces of the carbon cloth material to form the MPLs [153,158,161,171], followed by drying and sintering as mentioned earlier. Antolini et al. [161] were able to demonstrate that carbon cloth with double MPLs, for both the anode and the cathode sides, showed better performance than when a CFP was used as the cathode DL with one MPL. At low current densities, the difference between the two DLs was not as obvious, but it became more evident at higher current densities because the limiting current densities for each case are quite different ( 1.6 A cm for CFP vs. 2.7 A cm for CC) (see Figure 4.20 for more details). 

Pt/Ru electrocatalysts are currently used in DMFC stacks of a few watts to a few kilowatts. The atomic ratio between Pt and Ru, the particle si2 e and the metal loading of carbon-supported anodes play a key role in their electrocatalytic behavior. Commercial electrocatalysts (e.g. from E-Tek) consist of 1 1 Pt/Ru catalysts dispersed on an electron-conducting substrate, for example carbon powder such as Vulcan XC72 (specific surface area of 200-250 m g ). However, fundamental studies carried out in our laboratory [13] showed that a 4 1 Pt/Ru ratio gives higher current and power densities (Figure 1.6). 

Carbon powder mixed with polymeric binder (PVdF, PTFE) has been widely used as anode material for lithium ion batteries and as the electrode material for EDLC with liquid electrolyte solutions. When such composite electrodes composed of carbon powder and polymer binder were used in all-solid-state EDLC, the performance was not good enough because of poor electrical contact between the electrode s active mass and the electrolyte. By having the electrolyte inside the composite electrode, the contact between the active mass in the electrode and the electrolyte can be considerably improved and hence the capacitance can... 

The Leclancht cell has a cathode consisting of a mixture of MnO and carbon powder and a zinc anode. Manganese dioxide is the electro-... 

The methods described in detail in Section 36.2, or only mentioned, have been used as follows for spectrophotometric determination of palladium the thio-Michler s ketone — in silver, copper, and anodic slime [32], in catalysts [31] with thiosemicarbazide derivatives — in water [44] and alloys [46] with palladium-carbon powder — with a-benzilmonoxime [48] with PAR — in catalysts and ores [58] with thiazolylazo derivatives — in Ni-Al catalysts [63] with 5-Br-PADAP — in titanium alloys with pyridylazo derivatives - in nickel alloys [68] with sulphonitrophenol - in silver alloys [70] with Arsenazo III — in iron and meteorites and with Palladiazo — in catalysts, minerals, silica gel, and calcium carbonate [78]. 

This type of fuel cell has received much attention in recent years due to its moderate operating temperature and high-power density. The anode and cathode are Pt-loaded carbon powders. Air is normally used as the source of oxygen for the cathode reaction. Of major importance is the removal/management of product water from the fuel cell. A hydrated cation-exchange membrane separates the anode and cathode. 

Boron carbide can be prepared in a hydrogen-Ar plasma, using (1) amorphous boron and carbon powders (2) an anode made of a mixture of graphite with boric anhydride (or borax) and a graphite cathode, or (3) a mixture of BCI3-CH4 Boron... 

Alkaline cells use the same zinc-manganese dioxide couple as Leclanche cells. However, the ammonium chloride electrolyte is replaced with a solution of about 30 wt% potassium hydroxide (KOH) to improve ionic conductivity. The ceU reactions are identical to those above, but the battery construction is rather different (Figure 9.7). The negative material is zinc powder, and the anode (negative terminal) is a brass pin. The positive component is a mixture of Mn02 and carbon powder that surrounds the anode. A porous cylindrical barrier separates these components. The positive terminal (cathode) is the container, which is a nickel-plated steel can. 

A second type of anode is based on a conductive coating with carbon powder in an organic matrix. It has the following advantages it does not require an overlay, it can easily be appHed to structures of any form, and it does not present problems of additional weight to the structure or limitations of dimension the cost of installation can be lower, down to about half that of activated titanium mesh systems. On the other hand, it cannot deliver current densities above 20 mA/m over long periods (and maximum levels of 35 mA/m ) and its service life can reach 10-15 y, but not in humid climates where there may be loss of adhesion and effects of premature deterioration. 

The measurement of tin in human hair, canned fruit juice, and spiked sea water has been carried out using flow injection anodic stripping voltammetry. The system uses an epoxy-carbon powder 8-hydro-xyquinoline composite electrode and nonelectrodic preconcentration in an open circuit in which Sn(II) is accumulated in the wall-jet electrode. 

Half a decade ago, carbon paste had celebrated a notable jubilee 50 years of existence and extraordinarily wide applicability across the areas of electrochemistry and electroanalysis [1-3]. Herein, it can be remembered that carbon paste - that is, a thick mixture of a carbonaceous moiety with a suitable (usually liquid) binder - had originally been discovered as a certain by-product, coming from unsuccessful experimentation with carbon powder-based suspension intended to accomplish an electrode with renewable surface for anodic oxidations [2, 3]. 

In the current technological state, most commercially available products are electric double-layer ESs. Their electrodes are manufactured using an identical material, such as a high surface carbon powder, to serve as both anode and cathode materials. Using carbons as electrode materials is advantageous because they are widely available, inexpensive, and diverse in both structure... 

The active components of the cell are lithium for the anode and polycarbon monofluoride (CF) for the cathode. The value of is typically 0.9 to 1.2. Carbon monofluoride is an interstitial compound, formed by the reaction between carbon powder and fluorine gas. While electrochemically active, the material is chemically stable in the organic electrolyte and does not thermally decompose up to 400" C, resulting in a long storage life. Different electrolytes have been used typical electrolytes are lithium hexafluorarsenate (LiAsFg) in S-butyrolactone (GBL) or lithium tetrafluoroborate (LiBFJ in propylene carbonate (PC) and dimethoxyethane (DME). 

FIGURE 2.13 H2/air PEM fuel cell performance of electrodes with MPLs prepared using different carbon powders. Cell temperature 80 °C humidifier temperatures for anode and cathode 90° and 85°, respectively operating pressure 0.2 MPa [30]. 

So far, the Pt-Ru alloy has shown the most promising performance for the oxidation of methanol and hydrogen oxidation reaction in the presence of CO. Carbon black has been used as support for the metal nanoparticles, particularly Vulcan XC-72 (Cabot), which has a surface area of 240 m g . Methanol oxidation starts at lower potential values for all the Pt-Ru/C catalysts than for Pt/C anodes. Comparison of electrodes prepared with Pt and Pt-Ru as the electrocatalyst supported on nanotubes and those prepared with the most usual support, Vulcan XC-72 showed that multi-wall carbon nanotubes produce catalysts (Pt-Ru/MWNT) with better performance than on other supports, particularly with respect to those prepared with the traditional Vulcan XC-72 carbon powder [18],... 

Fig. 3.3 Comparison of specific capacities of carbon powder to the modified nanofibrous carbon anode materials for lithium-ion batteries...

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