Membrane in fuel cell performance

Overall, a great deal of attention has been paid to inducing ionic conductivity in chitosan membranes for application in fuel cell membranes. In both cationic and anionic membranes, the fuel cell performance values are approaching that of the industry standard Nation membranes. 

Long nanochannels can be used as single molecule sensors in a similar way as nanopores, as has been demonstrated in several recent studies. In addition to the application as single molecule sensors, long nanochannels and their arrays can be used as filters for molecule separation, membranes for electroosmotic pumping, templates for nanowire synthesis, electrodes for supercapacitors, and proton exchange membranes in fuel cells. Novel and complex transport phenomena can occur in nanochannels, leading to improved performance or new functions for devices made of nanochannels. 

Three main effects of cationic contamination include a loss in fuel cell performance an increase in high frequency cell resisfance, which does not wholly account for the performance losses and a decrease in limiting current. In addition to the effect on the membrane conductivity, the presence... 

Studies have shown that the decrease in membrane conductivity can explain only part of the total loss in fuel cell performance, typically 5 to 15%. Uribe et al. [84] and Soto et al. [86] attributed some performance loss to decreased ionomer conductivity in the catalyst layer. However, other studies [85,89] indicated that NH3 could also affect the kinetics of the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR). Halseid et al. [85] found that the HOR in a symmetric H2/H2 cell was affected by NH3 and they suggested that the adsorbed species could partially block the anode catalyst surface. They also found that the... 

The contaminants in a fuel cell system, if not effectively mitigated, can result in fuel cell performance degradation and premature failure of the fuel cell system. The adverse effect of certain contaminants (e.g., CO, H2S, NH4) on fuel cell performance can be detected quickly. These effects tend to be somewhat reversible. The effects of other contaminants are not easily detected, and tend to be irreversible. For example, certain trace metallic ions (Fe" % Cu ) can catalyze the decomposition of polymer electrolyte membranes without affecting ionic conductivity or the gas crossover rate of the membrane until... 

Poly(2,2 -(p-phenylene)5,5 -bibenzimidazole) (para-PBI) exhibits excellent performance when used as a membrane in fuel cells.[5] Para-PBI is prepared through the PPA process using equimolar amounts of terephthalic acid and... 

Low RH wiU also make thermal management of the fuel cell difficult. As the membrane resistance increases, the output voltage drops. To achieve the same power, the output current must increase. Thus, the fuel cell temperature rises, further decreasing the RH and making the membrane more hydrophobic. The result is continuous deterioration in fuel cell performance. 

Thomassin, J.M., J. Kollar, G. Caldarella et al. 2007. Beneficial effect of carbon nanotubes on the performances of Nafion membranes in fuel cell applications. Journal of Membrane Science 303 252-257. 

For further improvement in fuel cell performance, obvious problems as have been mentioned in this book need to be solved, such as raising the activity of catalysts for methanol oxidation, lowering the sensitivity of oxygen-electrode catalysts toward methanol, and building improved membranes. In addition, a number of fundamental problems need to be solved in the field of electrocatalysis. 

Features of ab-PBI are a Tg of 485°C, low coefficient of friction, high wear resistance properties, very high limiting oxygen index (LOI), very high heat deflection temperature (HDT), and extended high-temperature mechanical performance and excellent chemical resistance. Indeed, ab-PBI offers high heat resistance and mechanical property retention over 300°C. Potential uses are PBI areas mentioned earlier and in membranes in fuel cells, which operate at elevated temperatures. 

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