Proton exchange membrane fuel cells platinum catalysts

Sasikumar, G., Ihm, J. W, and Ryu, H. Dependence of optimum Nation content in catalyst layer on platinum loading. Journal of Power Sources 2004 132 11-17. Taylor, E. J., Anderson, E. B., and Vilambi, N. R. K. Preparation of high-plat-inum-utilization gas diffusion electrodes for proton-exchange-membrane fuel cells. Journal of the Electrochemical Society 1992 139 L45-L46. 

DMFCs and direct ethanol fuel cells (DEFCs) are based on the proton exchange membrane fuel cell (PEM FC), where hydrogen is replaced by the alcohol, so that both the principles of the PEMFC and the direct alcohol fuel cell (DAFC), in which the alcohol reacts directly at the fuel cell anode without any reforming process, will be discussed in this chapter. Then, because of the low operating temperatures of these fuel cells working in an acidic environment (due to the protonic membrane), the activation of the alcohol oxidation by convenient catalysts (usually containing platinum) is still a severe problem, which will be discussed in the context of electrocatalysis. One way to overcome this problem is to use an alkaline membrane (conducting, e.g., by the hydroxyl anion, OH ), in which medium the kinetics of the electrochemical reactions involved are faster than in an acidic medium, and then to develop the solid alkaline membrane fuel cell (SAMFC). 

An important possible future use for pure hydrogen is in proton-exchange-membrane fuel cells (PEMFCs) the basic source for the hydrogen could be either a hydrocarbon or an alcohol, either of which can be steam-reformed to produce water-gas.16,17 As explained above, the equilibrium concentration of carbon monoxide decreases as the temperature falls (Figure 10.1), but as little as 1% is detrimental to the operation of platinum-based catalysts in a fuel cell. Excess water, which is commonly used,18 serves to move the... 

Pt-based electrocatalysts are usually employed in proton exchange membrane fuel cells (PEMFC) and direct methanol fuel cells (DMSC). In direct-methanol fuel cells (DMFCs), aqueous methanol is electro-oxidized to produce COj and electrical current. To achieve enhanced DMFC performance, it is important to develop electrocatalysts with higher activity for methanol oxidation. Pt-based catalysts are currently favored for methanol electro-oxidation. In particular, Pt-Ru catalysts, which gave the best results, seem to be very promising catalysts for this application. Indeed, since Pt activates the C-H bounds of methanol (producing a Pt-CO and other surface species which induces platinum poisoning), an oxophilic metal, such as Ru, associated to platinum activates water to accelerate oxidation of surface-adsorbed CO to... 

Zhang S, yuan XZ, Cheng Hin JN, Wang H (2009) A review of platinum-based catalysts layer degradation in proton exchange membrane fuel cells. J Power Sources 194 588-600... 

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. 

Chen S, Gasteiger HA, Hayakawa K, Tada T, Shao-Hom Y (2010) Platinum-alloy cathode catalyst degradation in proton exchange membrane fuel cells nanometer-scale compositional and morphological changes. J Electrochem Soc 157(1) A82-A97... 

Electrodes with thin catalyst layers made using platinum on carbon electrocatalysts with a high Pt/C weight ratio and with more platinum localized near the front surface had the effect of diminishing the overpotentials in proton-exchange-membrane fuel cells [200]. 

Olson TS, Chapman K, Atanassov P (2008) Non-platinum cathode catalyst layer composition for single membrane electrode assembly proton exchange membrane fuel cell. J Power Density 183 557-563... 

Figure 23.23. Platinum surface area of the cathode with TKK 46 wt% Pt/Vulcan catalyst over 10,000 potential cycles at 20 mV/s in the voltage range 0.6-1.0 V at 80 °C under humidified H2-N2 (anode-cathode) [33]. (Reprinted by permission of ECS— The Electrochemical Society, from Ferreira PJ, la O GJ, Shao-Hom Y, Morgan D, Makharia R, Kocha S, Gasteiger HA. Instability of PEC electrocatalysts in proton exchange membrane fuel cells.)...

Figure 23.30. Comparison of the cumulative carbon corrosion following a 24-h 1.2 V potentiostatic hold at 80 °C in 1 M H2SO4 for two commercial carbons COl, C02 and one heat-treated carbon C03, and platinum and Pt/Co alloy catalysts on these carbons [95]. (Reprinted from Journal of Power Sources, 166(1), Prasanna M, Cho EA, Kim H-J, Oh I-H, Lim T-H, Hong S-A, Performance of proton-exchange membrane fuel cells using the catalyst-gradient electrode technique, 18-25, 2007, with permission from Elsevier.)...

FIGURE 3.12 Normalized activity of three separate 40 wt% platinum catalysts. Average of three separate tests and limits of error are plotted. (Reprinted from Journal of Power Sources, 161, Chhina, H. et al. An oxidation-resistant indium tin oxide catalyst support for proton exchange membrane fuel cells, 893 900, Copyright (2006), with permission from Elsevier.)... 

Nanofibre for use in proton exchange membrane fuel cells has been a focus of research during the last 5 years. These fuel cells have the potential for high thermodynamic efficiency and almost zero emissions, but are currently hindered by high cost of the platinum-based catalyst and low durability. Carbon nanofibre webs as a supporting medium for platinum nanoparticles have been employed [46]. 

Nitrogen-doped carbon nanotubes as platinum catalyst supports for oxygen reduction reaction in proton exchange membrane fuel cells. The Journal of Physical Chemistry C, 114 (50), 21982-21988. 

---