Direct cell performances

Ren, X. Springer, T. E. and Gottesfeld, S. (1998). Direct Methanol Fuel Cell Transport Properties of the Polymer Electrolyte Membrane and Cell Performance. Vol. 98-27. Proc. 2nd International Symposium on Proton Conducting Membrane Euel Cells. Pennington, NJ Electrochemical Society. 

Zhou WJ, Song SQ, Li WZ, Zhou ZH, Srm GQ, Xin Q, Douvartzides S, Tsiakaras P. 2005. Direct ethanol fuel cells based on PtSn anodes The effect of Sn content on the fuel cell performance. J Power Sources 140 50-58. 

As stated, one of the fundamental problems encountered in the direct oxidation of hydrocarbon fuels in SOFCs is carbon deposition on the anode, which quickly deactivates the anode and degrades cell performance. The possible buildup of carbon can lead to failure of the fuel-cell operation. Applying excess steam or oxidant reagents to regenerate anode materials would incur significant cost to SOFC operation. The development of carbon tolerant anode materials was summarized very well in several previous reviews and are not repeated here [7-9], In this section, the focus will be on theoretical studies directed toward understanding the carbon deposition processes in the gas-surface interfacial reactions, which is critical to the... 

Thomas, X., Ren, S., and Gottesfeld, J., Influence of ionomer content in catalyst layers on direct methanol fuel cell performance, Electrochem. Soc., 146, 4354, 1999. 

Discussions with the only US. PAFC manufacturer justified the direct use of the PAFC performance information from the 1994 edition of the Fuel Cell Handbook. There have been only minor changes in cell performance, mostly due to changing the operating conditions of the cell. These are considered within the performance trends shown in this section. The manufacturer has concentrated on improving cell stability and life, and in improving the system components to improve reliability and lower cost. It should be noted that the performance shown in this section is based on information from contracts that the manufacturer had with the Department of Energy or outside institutions. Any new PAFC performance has been accomplished with company funding and is considered proprietary by the manufacturer (1). 

Later it was found that the ink could be directly applied to the membrane [39]. However, for this technique, the membrane had to be converted to Na+ or K+ form to increase its robustness and thermoplasticity. With advancements in the technique, the total catalyst loading for the CCM could be reduced to 0.17 mg/ cm without any compromise in cell performance [39]. Compared to CCCDL technology, the CCM approach seems the preferred method for CL fabrication. 

Hatanaka, T., Hasegawa, N., Kamiya, A., Kawasumi, M., Morimoto, Y. and Kawahara, K. 2002. Cell performances of direct methanol fuel cells with grafted membranes. Fuel 81 2173-2176. 

Elabd, Y. A., Walker, C. W. and Beyer, F. L. 2004. Triblock copolymer ionomer membranes. Part 11. Structure characterization and its effects on transport properties and direct methanol fuel cell performance. Journal of Membrane Science 231 181-188. 

As discussed previously, a number of different materials have been considered as potential candidates to be used as diffusion layers in PEMFCs and direct liquid fuel cells (DLFCs). The two materials used the most so far in fuel cell research and products are carbon fiber papers and carbon cloths, also known as carbon woven fabrics. Both materials are made from carbon fibers. Although these materials have been quite popular for fuel cells, they have a number of drawbacks—particularly with respect to their design and model complexity—that have led to the study of other possible materials. The following sections discuss in detail the main materials that have been used as diffusion layers, providing an insight into how these materials are fabricated and how they affect fuel cell performance. 

Ofher diffusion layer approaches can also be found in the literature. Chen-Yang et al. [81] made DLs for PEMFCs out of carbon black and unsintered PTFE comprising PTFE powder resin in a colloidal dispersion. The mixture of fhese materials was then heated and compressed at temperature between 75 and 85°C under a low pressure (70-80 kg/cm ). After this, the DLs were obtained by heating the mixture once more at 130°C for around 2-3 hours. Evenfually, fhe amount of resin had a direct influence on determining the properties of fhe DL. The fuel cell performance of this novel DL was shown to be around a half of that for a CFP standard DL. Flowever, because the manufacturing process of these carbon black/PTFE DLs is inexpensive, they can still be considered as potential candidates. 

In addition to the way in which the MPL is manufactured, other MPL parameters directly affect fuel cell performance. These include fhickness of fhe MPL, carbon loading, PTFE content, type of carbon parficles, efc. The following subsection will briefly discuss them. 

C. Xu, T. S. Zhao, and Q. Ye. Effect of anode backing layer on the cell performance of a direct methanol fuel cell. Electrochimica Acta 51 (2006) 5524—5531. 

Cul could be partly in contact with Ti02 directly therefore, the efficiency decreased by the recombination of injected electrons with Cul. In order to increase cell performance, direct contact between the Ti02 film and Cul must be minimized. Solid-state DSSCs have been studied using other organic and inorganic hole conductor materials, such as p-type CuSCN [147,148], polypyrrole [149], and polyacrylonitrile [95]. 

The analysis of the conditions within a gas channel can also be assumed to be onedimensional given that the changes in properties in the direction transverse to the streamwise direction are relatively small in comparison to the changes in the stream-wise direction. In this section, we examine the transport in a fixed cross-sectional area gas channel. The principle conserved quantities needed in fuel cell performance modeling are energy and mass. A dynamic equation for the conservation of momentum is not often of interest given the relatively low pressure drops seen in fuel cell operation, and the relatively slow fluid dynamics employed. Hence, momentum, if of interest, is normally given by a quasi-steady model,... 

For the calculation of the electrochemical reaction rates the cathode gas composition is required. Considering the MCFC as a black box, the anode feed gas is completely oxidized with air which is fed into the catalytic combustion chamber, either electro-chemically or in an ordinary combustion reaction. With this, the amount and composition of the exhaust gas is independent of the electric cell performance and can be calculated directly from the conditions of the anode feed and the air feed. According to the assumption of spatially concentrated conditions inside the cathode channel, the exhaust conditions correspond to the conditions in the cathode gas channel. Thus, the cathode gas composition is determined from a combustion calculus. 

In recent decades, research has intensified to develop commercially viable fuel cells as a cleaner, more efficient source of energy, due to the global shortage of fossil fuels. The challenge is to achieve a cell lifetime suitable for transportation and stationary applications. Among the possible fuel cell types, it is generally believed that PEM fuel cells hold the most promise for these uses [10, 11], In order to improve fuel cell performance and lifetime, a suitable technique is needed to examine PEM fuel cell operation. EIS has also proven to be a powerful technique for studying the fundamental components and processes in fuel cells [12], and is now widely applied to the study of PEM fuel cells as well as direct methanol fuel cells (DMFCs), solid oxide fuel cell (SOFCs), and molten carbonate fuel cells (MCFCs). 

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