Utilizing Bipolar Design

Titanium bipolar plate Negative electrode material Porous separator Sealing rubber washer Positive electrode material Titanium positive end plate Insulating rubber sheet Stainless steel plate 

Bipolar electrode ceU design adapted from U.S. Patent 4022952 [accessed February 12,2012]. Al, A2, and A3 are positive electrodes of supercapacitor Bl, B2, and B3 are negative electrodes of supercapacitor. 

Following in succession, Aj is in direct contact to electrode Bj as they are both represented by the single bipolar electrode. As a result, for n bipolar electrodes, the stack will contain n + 1 cells in series. The current collectors on both ends of the stack labeled Ej and E2 are critical in transmitting the power density of a stack and therefore, require excellent intrinsic conductivity and good contact with the active material. 

Metal end plates are normally used as the current collectors because they possess sound mechanical properties that maintain the stack s structural stability and provide a facile means of connecting external leads. However, the current collector surface musf be treafed to enhance the contact of the 

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They also dramatically advanced the bipolar design concept, first explored by Marwood and Vayenas to induce NEMCA in monolithic YSZ stmctures, a key step for the practical utilization of NEMCA. 

The Hooker MX, Allied PCF, and Ionics Chloromate electrolyzers are all bipolar designs that utilize plastic cell frames The electrolytic area of these cells is typically 1.2-1 5 per cell unit The electrolyzers are typically composed of 10-50 cell units Power consumptions are reported to be 2750 KWH/metric ton of NaOH operating at 3KA/M current density at 95% current efficiency producing 35% caustic soda (65,69,70) ... 

Efforts to improve the ratio of effective to theoretical specific energy involve, in general (1) replacement, where possible, of inert grid, container, connector, and current collector materials by lightweight substances (2) increase of utilization of active materials by improved cell design and/or use of special additives (3) careful modeling and optimization of current collection and (4) use of bipolar electrodes. 

Design and demonstrate a reformate-capable fuel cell stack, utilizing CO-tolerant membrane electrode assemblies (MEAs) and low cost bipolar collector plates. 

The depolarization shock can be delivered flirough either a unipolar or bipolar lead. Most older leads utilize the unipolar design (Morley-Davies and Cobbe, et al., 1997), in which a single insulated electrode is placed near the myocardium of the heart and acts as a cathode (Tyers et al., 1997 ... 

Engineering issues of fuel cell stack and systems design will be dealt with in the following chapters. Hence, issues of, e.g., coflow or counterflow within one cell, stoichiometry and utilization of fuel and oxidant, temperature and current distribution in a fuel cell of technical scale, and, certainly, issues of stacking cells into a bipolar arrangement will not be discussed here. 

Other methanol-tolerant catalysts have been found in iron poiphyiine-type materials supported on high surface area carbon [69,70]. These catalysts were tested in fuel cell conditions and it was found that no deterioration of the electrode performance could be seen when utilizing methanol in the ceU. The catalysts are insensitive to methanol. These catalysts were also combined with a new cell concept whereby the anode and the cathode reside in the same compartment. Both electrodes are in contact with the same side of the membrane, thus eliminating most of the ohmic resistance in the cell. The fuel efficiency in the ceU at low current densities was much higher than for a normal bipolar plate design. A methanol-tolerant cathode is a prerequisite to make this concept feasible. 

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