Proton-exchange membrane fuel cells efficiency

F. (2010). Ionic liquids in proton exchange membrane fuel cells Efficient systems for energy generation /, power Source, 195,6483-6485, ISSN 0378-7753. 

There are six different types of fuel cells (Table 1.6) (1) alkaline fuel cell (AFC), (2) direct methanol fuel cell (DMFC), (3) molten carbonate fuel cell (MCFC), (4) phosphoric acid fuel cell (PAFC), (5) proton exchange membrane fuel cell (PEMFC), and (6) the solid oxide fuel cell (SOFC). They all differ in applications, operating temperatures, cost, and efficiency. 

In the case of 50 kW power, the rate of hydrogen supply needed (LH) is around 1.69 X 103 (mol/h) at the energy-conversion-efficiency level of 45% for the proton exchange membrane fuel cell (PEM-FC) [38]. 

Fang, B., et al., High Pt loading on functionalized multiwall carbon nanotubes as a highly efficient cathode electrocatalyst for proton exchange membrane fuel cells. Journal of Materials Chemistry, 2011. 21(22) p. 8066-8073. 

J. Srmivason, et al., "High Energy Efficiency and High Power Density Proton Exchange Membrane Fuel Cells - Electrode Kinetics and Mass Transport," Journal of Power Sources, p. 36, 1991. 

General. There is no doubt that a comparison (updated in the 1990s) of the potential vs. current density plot for the various fuel cells (see Fig. 13.27) shows that the proton exchange membrane fuel cell with a perfluoropolymer sulfuric acid has superior performance (i.e., higher cell potential and hence efficiency) compared with the other types of fuel cells. Because this cell has been chosen for development by the majority of the automotive manufacturers, special attention is given here to its development. 

Bulk production of hydrogen via electrolysis appears improbable until renewable or nuclear electricity becomes widely available and considerably cheaper than at present. The principal attribute of electrolytic hydrogen is its ultra-purity, which is an important requirement for proton-exchange membrane fuel cells. Nevertheless, the use of valuable electricity to electrolyze water and then feeding the resultant hydrogen to a fuel cell is intrinsically wasteful by virtue of the combined inefficiencies of the two devices involved. This really only makes sense in situations where there is more electricity than can be consumed as such, or where there are reasons for wanting hydrogen that transcend considerations of efficiency and cost. 

Min et al. [35] experimented on high-catalyst loading with 60% carbon and 40% Teflon backing claimed to be the most efficient electrode for direct methanol/proton exchange membrane fuel cell (PEMFC). The catalysts used were platinum and ruthenium which formed an alloy at an atomic ratio 1 1. The formation of the alloy was seen in XRD as there were no pure metal peaks found. The alloy formation of Pt and Ru promotes oxidation of methanol at lower temperatures. The 60% carbon backing makes it evident that the lower the percentage of carbon increases the efficiency. 

Fang B, Kim JH, Kim M, Yu JS (2009) Ordered hierarchical nanostructured carbon as a highly efficient cathode catalyst support in proton exchange membrane fuel cell. Chem Mater 21(5) 789-796... 

---