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.

Now, researchers at the University of California, Riverside, U.S.A., have investigated increasing Pt utilisation in PEMFCs by using carbon multiwalled nanotubes (MWNTs) as the Pt support (C. Wang, M. Waje, X. Wang, J. M. Tang, R. C. Haddon and Y. Yan, Nano Lett., 2004, 4, (2), 345–348; doi: 10.1021/nl034952p).

MWNTs were grown directly onto C paper by chemical vapour deposition. The Pt catalyst was then electrodeposited onto the MWNTs. The Pt 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 C paper and excellent adhesion. The surface area of the MWNT-C paper composite was ∼ 80–140 m² g⁻¹ (< 2 m² g⁻¹ for the C paper alone).

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 Pt particle size to ∼ 2.5 nm, improving MWNT yield and reducing tube diameter will give C nanotube-based fuel cells of superior performance.