Anodized electrodes

Anode electrode assembly, electrode panel between compression molded gaskets. 

Anode Electrode at which oxidation occurs and toward which anions move, 481-485,496 Antifreeze solution, 270 Antimony, 63... 

The Surface Fractal Investigatioii of Anode Electrode of Molten Carbonate Fuel Cell... 

In order to describe the geometrical and structural properties of several anode electrodes of the molten carbonate fuel cell (MCFC), a fractal analysis has been applied. Four kinds of the anode electrodes, such as Ni, Ni-Cr (lOwt.%), Ni-NiaAl (7wt.%), Ni-Cr (5wt.%)-NijAl(5wt.%) were prepared [1,2] and their fractal dimensions were evaluated by nitrogen adsorption (fractal FHH equation) and mercury porosimetry. These methods of fractal analysis and the resulting values are discussed and compared with other characteristic methods and the performances as anode of MCFC. 

The wetting ability of the anode electrode was evaluated as the contact angle measured by the capillary rise method. The value of fractal dimension of anode electrode of MCFC was calculated by use of the nitrogen adsorption (fractal FHH equation) and the mercury porosimetry. 

The wetting ability of an MCFC electrode is closely related to the performance of cell operation especially including electrochemical reaction, and can be expressed as contact angle between electrolyte and electrode. The surface energy of 3 phases, geometric structure of anode electrode and... 

Here, is the average effective radius of pore, is surface tension between liquid and vapor, 0 is the contact angle, rj is the dynamic viscosity of the electrolyte, and h is the height elevation of the electrolyte within pore at time r. In the experiment, the amount of electrol he wetted within the anode electrode, m, expressed as h = m/pAP, was measured instead of the height, h. Integrated Eq. (l)for t becomes Eq. (2). 

Here, A is the contacting surface area of anode electrode facing with electrolyte and P is the porosity of anode electrode. The average effective radius of pore,, could be calculated from the results of the capillary rise method using ethanol, which shows a contact angle of 0° with the anode electrode. And then, the contact angle 0 could be acquired as the slope from the plot of m versus... 

Here, P is the equilibrium pressure. Therefore, Dj of the anode electrode can be also calculated through the slope of a log-log plot of Eq. (4) by the data from the mercury porosimeter. 

With the experimental results about the wetting ability and the fractal dimension of four kinds of anode electrodes, we could conclude the following. The addition of NisAl could make the electrolyte wet the electrode very well. The pore structures of all the electrodes prepared in this study were highly irregular and rough. Finally, the chemical properties of the surfaces were as important as the physical properties in determining the wetting ability of the electrodes in this study. 

Fig. 1. Mass increases of anode electrodes with time by the contact with electrolytes.

Anode electrode Sintering temp. ("C) Initial porosity (%) FHH equation (Nitrogen adsorption) Mercury porosimetry Average Ds- Contact Angle with electrolyte 0C)... 

Fig. 1 shows I-V characteristics of MEAs fabricated with prepared catalysts. As anode electrodes, Pt-Ru/SRaw, Pt-Ru/S700, Pt-Ru/S800 and Pt-Ru/S900 catalysts were evaluated. 

The functional dependence of the activation energy of the anodic electrode reaction can be derived as follows. According to the definition of the rate of the electrode reaction, the partial current density... 

A similar relationship is valid for the charge transfer coefficient of the anodic electrode reaction, aa. 

In order to explain the changing optical properties of AIROFs several models were proposed. The UPS investigations of the valence band of the emersed film support band theory models by Gottesfeld [94] and by Mozota and Conway [79, 88]. The assumption of nonstoichiometry and electron hopping in the model proposed by Burke et al. [87] is not necessary. Recent electroreflectance measurements on anodic iridium oxide films performed by Gutierrez et al. [95] showed a shift of optical absorption bands to lower photon energies with increasing anodic electrode potentials, which is probably due to a shift of the Fermi level with respect to the t2g band [67]. 

In applications where Nafion is not suitable, at temperatures above 200 °C with feed gas heavily contaminated with CO and sulfur species, a phosphoric acid fuel cell (PAFC)-based concentrator has been effective [15]. Treating the gas shown in Table 1, a H2 product containing 0.2% CO, 0.5%CO2 and only 6 ppm H2S was produced. The anode electrode was formed from a catalyst consisting basically of Pt-alloy mixed with 50% PTFE on a support of Vulcan XC-72 carbon. The cathode was... 

The same group, in a previous work, reported on the realization of a hybrid anode electrode [197]. An appreciable improvement in methanol oxidation activity was observed at the anode in direct methanol fuel cells containing Pt-Ru and Ti02 particles. Such an improvement was ascribed to a synergic effect of the two components (photocatalyst and metal catalyst). A similar behavior was also reported for a Pt-Ti02-based electrode [198]. Another recent study involved the electrolysis of aqueous solutions of alcohols performed on a Ti02 nanotube-based anode under solar irradiation [199]. 

Fig. 4. Artist s drawing of the stimulator, silicone rubber tube or guidance channel, and the electrical circuit within the spinal cord. The tube was implanted into the dorsal spinal cord. The uninsulated tip of the cathodal electrode (negative) was sealed within the center of the tube, while the anodal electrode (positive) remained outside the vertebral column, sutured to paravertebral musculature. The body of the stimulator was surgically placed within the fat pad at the base of the guinea-pig s neck. To complete a circuit, current must flow initially into each end of the hollow tube as diagrammed. For diagrammatic purposes, the drawing is not made to scale. [Reproduced with permission from Borgens (1999).]...

Electron injection has been observed during the chemical dissolution of an oxide film in HF [Mai, Ozl, Bi5]. The injected electrons are easily detected if the anodized electrode is n-type and kept in the dark. Independently of oxide thickness and whether the oxide is thermally grown or formed by anodization, injected electrons are only observed during the dissolution of the last few monolayers adjacent to the silicon interface. The electron injection current transient depends on dissolution rate respectively HF concentration, however, the exchanged charge per area is always in the order of 0.6 mC cm-2. This is shown in Fig. 4.14 for an n-type silicon electrode illuminated with chopped light. The transient injection current is clearly visible in the dark phases. 

CNT-based inorganic hybrid materials are part of carbon-based inorganic hybrid materials as anodic electrodes in LIBs. The concept has been proven to be successful at least at laboratory scale, and is promising as a potential alternative to replace graphite-based anodes. However, little is known about the interface structure between CNT and the supported active materials, and thus the electron transfer between the two components. More detailed fundamental research on the interface and interaction between CNTs and active materials at atomic level is needed for a better understanding of the abovementioned improvement. 

In electrochemical kinetics, the plot of reaction current (reaction rate) as a fimction of electrode potential is conventionally called the polarization curve. Figure 7—4 shows schematic polarization curves of cathodic and anodic electrode reactions. The term of polarization means shifting the electrode potential from a certain specified potential, e.g. the equilibrium potential of an electrode reaction, to more negative (cathodic) or more positive (anodic) potentials. The term of polarization also occasionally applies to the magnitude of potential shift from the specified potential. 

For some metallic electrodes, such as transition metals, metal ions dissolve directly from the metallic phase into acidic solutions tiiis direct dissolution of metal ions proceeds at relatively low (less anodic) electrode potentials. The direct dissolution of metal ions is inhibited by the formation of a thin oxide film on metallic electrodes at higher (more anodic) electrode potentials. At still higher electrode potentials this inhibitive film becomes electrochemically soluble (or apparently broken down) and the dissolution rate of the metal increases substantially. These three states of direct dissolution, inhibition by a film, and indirect dissolution via a film (or a broken film) are illustrated in Fig. 11-9. 

Summing of Electrode Polarization Activation and concentration polarization can exist at both the positive (cathode) and negative (anode) electrodes in fuel cells. The total polarization at these electrodes is the sum of r act and riconc, or... 

Even though the above work is providing a stable, non-sintering, creep-resistant anode, electrodes made with Ni are relatively high in cost. Work is in progress to determine whether a cheaper material, particularly Cu, can be substituted for Ni to lower the cost while retaining stability. A complete substitution of Cu for Ni is not feasible because Cu would exhibit more creep than Ni. It has been found that anodes made of a Cu - 50% Ni - 5% A1 alloy will provide long-term creep resistance (36). Another approach tested at IGT showed that an "IGT" stabilized Cu anode had a lower percent creep than a 10% Cr - Ni anode. Its performance was about 40 to 50 mV lower than the standard cell at 160 mA/cm. An analysis hypothesized that the polarization difference could be reduced to 32 mV at most by pore structure optimization (37). 

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