Performance of PEMFC

The research is focused on lowering the cost of PEMFC and improving its performance. Usually, increasing the power for a system makes it more efficient. Additionally, it will also increase the cost and weight of the fuel cell system. The pressure increase raises the exchange current density and hence the OCV also increases lowering the cathode overpotenlial. The rate in OCV is given by 

Let current I Amperes in flowing through n stacks of PEMFC then the power gain will be given by 

We derive the voltage loss and hence power loss in a more detailed way as follows  

Whenever a gas expands, work is done by gas, or in other words, the work is done on the gas for compressing it. In an adiabatic reversible process (no heat loss), the pressure change from pi to p2 will lead to temperature change of Ti to T[ i.e., 

Equation (2.87) provides the temperature change, which will be used to obtain the power lost (Fiost) for unit time i.e.. 

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Jung, U. H., Park, K. T., Park, E. H., and Kim, S. H. Improvement of low-humidity performance of PEMFC by addition of hydrophilic SiOj particles to catalyst layer. Journal of Power Sources 2006 159 529-532. 

G. Lim and C. Y. Wang. Effects of hydrophobic polymer content in GDL on power performance of a PEM fuel cell. Electrochimica Acta 49 (2004) 4149-4156. G. G. Park, Y. J. Sohn, T. H. Yang, et al. Effect of PTFE contents in the gas diffusion media on the performance of PEMFC. Journal of Power Sources 131 (2004) 182-187. 

G. Velayutham, J. Kaushik, N. Rajalakshmi, and K. S. Dhathathreyan. Effect of PTFE content in gas diffusion media and microlayer on the performance of PEMFC tested under ambient pressure. Fuel Cells 7 (2007) 314—318. 

T. Jian-hua, S. Zhao-yuan, S. Jin-song, and S. Zhong-qiang. Preparation of water management layer and effects of its composition on performance of PEMFCs. Energy Conversion and Management 49 (2008) 1500-1505. 

Figure 6.11. Nyquist plots for MEAs containing different proton-conducting ionomers at 0.85 V without external humidification catalyst loading = 0.4, 0.7 mg Pt/cm2 for anode and cathode, respectively TceU = 25°C Pressure = 1 atm and H2/02 flow = 400 cmVmin [8]. (Reprinted from Electrochimica Acta, 50(2-3), Ahn SY, Lee YC, Ha HY, Hong SA, Oh IH. Effect of the ionomers in the electrode on the performance of PEMFC under non-humidifying conditions, 673-6, 2004, with permission from Elsevier.)...

The performance of PEMFC is often presented by the polarization curve that shows the voltage output as a function of current density. Fig. 8 shows a typical polarization curve of PEMFC. As the PEMFC processes charge-transfer reactions and the diffusion of the reactants to and products from the electrochemical interface, the transport and kinetics within the cell determine the polarization characteristics of PEMFC. In the practical PEMFC, the terminal cell potential V... 

The gas diffusion layers, one next to the anode and the other next to the cathode, are usually made of a porous carbon paper or carbon cloth, typically 100 pm to 300 pm thick. Fig. 14 shows a porous GDL made of carbon paper, which is partially covered by catalyst layer. The porous nature of the backing layer ensures effective diffusion of feed and product components to and from the electrode on the MEA. The correct balance of hydrophobicity in the backing material, obtained by PTFE treatment, allows the appropriate amount of water vapor to reach the MEA, keeping the membrane humidified while allowing the liquid water produced at the cathode to leave the cell. The permeability of oxygen in the GDL affects the limiting current density of ORR, and thus the performance of PEMFC.[ l... 

Stack, to optimize the FCS efficiency and reliability and to fully exploit the dynamic performance of PEMFC. 

Zhou, T. and Liu, H.T., Simulation of Performance of PEMFC Operated by Reformed Gas, accepted for the 2002 Fuel Cell Seminar, Palm Springs, California, November 18-21, 2002. 

Tungsten carbide based non-Pt electrocatalyst have been evaluated for single cell performance of PEMFC. The power densities of WC/C (1 mg/cm ) and Ni-WC/C (1 mg/cm ) anodes fabricated by TPRe were 6.5 and 8.9 mW/cm, respectively, cathode of 20 wt% Pt and membrane of Naflon 117 (151). W2C (0.48 mg/cm ) anode catalyst was prepared by ball-milling of WO3, Mg, and C mixture and tested in a single cell mode at 80°C with Pt/C cathode (0.3 mg/cm ), Naflon 112 membrane, and H2/Air = 5. This electrocatalyst produced high current densities of 240 mA/cm (at 2 atm) and 280 mA/cm (at 3 atm) at 0.5 V, and an open circuit voltage of 0.95 V(152). These values represent the highest current density reported for WC-based anode in the literature. In the analysis, the material... 

Lee SJ, Mukerjee S, McBreen J, Rho YW, Kho YT, Lee TH. Effects of Nafion impregnation on performances of PEMFC electrodes. Electrochim Acta... 

It has been found that the use of a second element wifli Pt, sueh as Ru, Sn, Co, Cr, Fe, Ni, Pd, Os, Mo, Mn, etc., in the form of an alloy or a co-deposit yields significant improvement in the CO-tolerance relative to pure Pt [29-38]. Among these various Pt-based binary systems, the most commonly used eatalyst is carbon-supported PtRu alloy (PtRu/C). This material is known to enhance CO tolerance, which can be ascribed to the electronic modification of Pt-Ru in PtRu alloys that decreases the CO binding energy on Pt and also binds OH strongly on the Ru active sites in the PtRu alloys [39]. Within this system, the performance of PEMFCs has been improved for fuel streams containing CO [40-42]. 

Park GG, Sohn YJ, Yang TH, Yoon YG, Lee WY, Kim CS. Effect of PTFE contents in the gas diffusion media on the performance of PEMFC. J Power Sources 2004 131 182-7. 

Many concerns arose about the quality of hydrogen rich gas because, during the hydrogen production process, impurities are also produced or introduced from feedstock or air and may adversely affect the performance of PEMFCs. 

The effects of air impurities, such as SO2, NO2, H2S, and CT, on the performance of PEMFCs have not been extensively studied in the literature, although it is believed that continual exposure to low concentration of these impurities is detrimental to cell performance. Contamination mitigation on... 

Boyaci SFC, Isik-Gulsac I, Osman OO (2013) Analysis of the polymer composite bipolar plate properties on the performance of PEMFC (polymer electrolyte membiane fuel cells) by RSM (response surface methodology). Eneigy 55 1067-1075... 

FIGURE 8.19 Simulated performance of PEMFC performance under air + NO,. (Reprinted from Franco, A. A. et al. 2009. ECS Transactions 25 1595-1604. With permission from The Electrochemical Society, Inc.)... 

Figure 17.20 Performance of PEMFC fabricated by using H PO -treated BC (a) and PA-treated BC (b) as a proton conducting membrane.

Figure 17.22 Performance of PEMFC fabricated by using Pt-incorporated BC shows an increase in maximum power density with an increase in operating temperature.

Eigure 14.11 shows isotherms of water desorption, that is, the dependence of water content V on the values of Ps/po for Nafion 117 membranes at temperatures of 20 and 80°C. These isotherms are of importance since, depending on mass-transport processes, the relative humidity in the gas chambers adjacent to the membranes can vary substantially. The corresponding changes in the membrane s water content influence the conductivity of the membrane and hence the fuel cell performance. From the figure it can be seen that a lowering of the Ps/po value from 1.0 to 0.8 at 80°C leads to a 20% decrease of the membrane s water content, which can substantially lower the performance of PEMFCs. 

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