Anode contact cells

Xing and Dahn recently reported [70] that <2 R for disordered carbon and MCMB 2800 can be markedly reduced from about 180 and 30mAhg l to less than 50 and lOmAhg-1 respectively, when the carbon anode and cell assembly are made in an inert atmosphere and never come in contact with air. This indicates that these carbons contain nanopores that... 

Any one of the three components in SOFC, the cathode, anode, or electrolyte, can provide the structural support for the cells. Traditionally, the electrolyte has been used as the support however, this approach requires the use of thick electrolytes, which in turn requires high operating temperatures. Electrode-supported cells allow the use of thin electrolytes. The Siemens—Westinghouse Corporation has developed a cathode-supported design,although this has required electrochemical vapor deposition of the YSZ electrolyte. Most other groups have focused on anode-supported cells. In all cases, it is important to maintain chemical compatibility of those parts that come in contact and to match the thermal expansion coefficients of the various components. A large amount of research has been devoted to these important issues, and we refer the interested reader to other reviews. 

Certainly, the period between servicing of the cell is determined either by disintegration of the anode or by corrosion of the anode contact and downtime is a constant problem with fluorine cells. 

Figure 4. Typical HMI display for an individual operating cell, clearly showing a short circuit (high current) and a poor anode contact (adjacent low cathode currents).

The ohmic polarization in Eq. (26.12) represents the total area specific ohmic resistance of the cell. Ri is the sum of the anode, cathode, electrolyte, interconnect, and contact ohmic resistances. Typically, the ohmic resistance is dominated by the electrolyte resistance and decreases with increasing operating temperature. The reduction in ohmic polarization is part of the reason why anode-supported cells have become the standard design in current high-performance SOFCs. 

What is the cell potential of a concentration cell that contains two hydrogen electrodes if the cathode contacts a solution with pH = 7.8 and the anode contacts a solution with [H+] = 0.05 M ... 

With the exception of the anode contact (where slight modification of the top/anode interface is necessary), materials for the cadmium/mercuric oxide cell are generally the same as for the zinc/mercuric oxide cell. However, because of the wide range of storage and operating conditions of most applications, cellulose and its derivatives are not used, and low-melting-point polymers are also avoided. Nickel is usually used on the anode side of the cell and also, conveniently, at the cathode. 

Fig. 1 Cross section of a standard cell (1) anode channel (2) cathode channel (3) cooling channel (4) gas-diffusion layer (5) membrane (6) cathode contact area (7) anode contact area (8) hydrogen diffusion length at the channel (9) hydrogen diffusion length at the contact area (10) oxygen diffusion length at the channel (11) oxygen diffusion length at the contact areas (12) water diffusion length at the channel (13) water diffusion length at the contact areas...

Fig. 6 Cross section of a cell with a porous gas distribution structure (1) anode channel (2) cathode channel (3) cooling channel (4) gas-diffusion layer (5) membrane (6) cathode contact area (7) anode contact area...

Xing and Dahn recently reported [68] that Qjr for disordered carbon and MCMB 2800 can be markedly reduced from about 180 and 30 mAh g to less than 50 and 10 mAh g respectively, when the carbon anode and cell assembly are made in an inert atmosphere and never come in contact with air. This indicates that these carbons contain nanopores that are not accessible to the electrolyte but are permeable to O2, CO2, and H2O. The absorption of these gases appears to be the dominant cause of the irreversible loss of capacity [68]. The peaks at about 0.7 and 0.3 V vs Li/Li+ in dQ/d Vcurves are assigned to electrolyte reduction and reactions with COH and COOH groups respectively. 

The improvement in power conversion efficiency (PCE) of plasmonic solar cells is always an urgent problem and short circuit current density is one of the key factors for the PCE. The improvement in the Jsc of plasmonic solar cells is mainly achieved by the introduction of metallic nanoparticles, such as blending Au nanoparticles into the anodic buffer layer or the interconnecting layer that connects two subcells of the tandem plasmonic solar cells [86]. Compared with the metallic NPs, nanowires (NWs) are superior in terms of improving photocurrent, while most of the metallic NWs introducing in cells reported previously were used for the anodic contact of the cells [87]. The improvement of PCE in bulk heterojunction polymer solar cells with active layer P3HT PCBM by introducing 40 nm Au nanoparticles between ITO and PEDOT PSS layer with various concentrations is also observed by Gao et al. [88]. It has been found that both short-circuit current density and PCE increase from 3.50% to 3.81% with 0.9 wt. % Au NPs due to the localized surface plasmon excitation of Au NPs. 

Fig. 12 Le/i Effect of the flow configuration and methane conversion fraction (PR) on the stress. Case of an anode-supported cell with LSM-YSZ cathode and compressive gaskets, a Temperature profile and b First principal stress in the anode. The MIC is displayed in transparency, c First principal stress in the cathode (insert alxtve the symmetry line), d Contact pressure on the cathode GDL and compressive gasket and e vertical displacement along the z-axis, with an amplification factor of 2,000. Right column effect of creep in a cell based on a LSCF cathode and a temperature distribution, on b the evolution of the first principal stress in the anode support in operation and c during thermal cycling to RT and d evolution of the first principal stress in the GDC compatibility layer after thermal cycling. The profiles above and below the symmetry axis refer to different operation time [88, 89]. Reproduced here with kind permission from Elsevier 2012...

The cell for this process is unlike the cell for the electrolysis of aluminum which is made of carbon and also acts as the cathode. The cell for the fused-salt electrolysis is made of high temperature refractory oxide material because molten manganese readily dissolves carbon. The anode, like that for aluminum, is made of carbon. Cathode contact is made by water-cooled iron bars that are buried in the wall near the hearth of the refractory oxide cell. 

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