Proton exchange membrane fuel cells (PEMFCs) generate electric power efficiently without producing exhaust gases, so are very desirable for use in LEVs or ZEVs (low or zero emission vehicles) and as power sources for small portable electronics. However, achieving minimised metal content with the costly platinum group metals catalysts is one of the challenges to their commercialisation.
The Process for Using Multi-Walled Carbon Nanotubes (MWNTs) as the Platinum Support in PEMFCs
Now, researchers at the University of California, Riverside, U.S.A., have investigated increasing platinum utilisation in PEMFCs by using carbon multiwalled nanotubes (MWNTs) as the platinum support (C. Wang, M. Waje, X. Wang, J. M. Tang, R. C. Haddon and Y. Yan, Nano Lett., 2004, 4, (2), 345–348;). MWNTs were grown directly onto carbon paper by chemical vapour deposition. The platinum catalyst was then electrodeposited onto the MWNTs. The platinum particles had an average diameter of 25 nm (commercial Pt/C catalysts are 2–3 nm). There was good electrical contact between the MWNTs and the carbon paper and excellent adhesion. The surface area of the MWNT-carbon paper composite was ~ 80–140 m2 g−1 (< 2 m2 g−1 for the carbon paper alone).
Fuel Cells Based on Carbon Nanotubes Can Offer Improved Quality
A membrane electrode assembly was prepared with two of the composite electrodes and tested in a fuel cell station. Its performance was lower than that of a conventional PEMFC, but its robustness was confirmed. It is suggested that reducing the platinum particle size to ~ 2.5 nm, improving MWNT yield and reducing tube diameter will give carbon nanotube-based fuel cells of superior performance.
Source: Platinum Metals Review, July 2004, Volume 48, Issue 3, page 132.
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