A low-cost fuel cell free from noble metals has been developed, and comprises an alkaline polymer electrolyte, a silver cathode and a nickel anode decorated with chromium
Various fuel cells have been developed for clean production of electricity, with hydrogen as the fuel and water as the only by-product. Several combinations of electrolytes and electrodes have been investigated, but noble metals have so far always been required as catalysts. Their use at either the anode (where hydrogen is oxidized) or the cathode (where oxygen is reduced), has hindered the widespread application of fuel cells because of their high cost. Now, Lin Zhuang and co-workers at Wuhan University in China have assembled1 the first fuel cell completely free from noble metals.
A polymer alkaline electrolyte was prepared from quaternary ammonium sulfone ions, and shown to be highly conductive and mechanically stable. It combines the advantages of polymer electrolytes, which avoid leakage problems and enable smaller devices to be made, with those of alkaline ones that can be used with the cheaper metals silver and nickel as electrodes. But although silver can be used as the cathode with the polymer version of the electrolyte, nickel has traditionally given poor performances as the anode.
Theoretical calculations showed that this loss of activity was due to strong interactions between the nickel surface and oxygen atoms, and suggested that this would be solved by the presence of a transition metal oxide. And indeed, the nickel anode had suitable catalytic activity when its surface also contained chromium. The fuel cell gave sufficient power and lifetime performance to prove for the first time that alkaline polymer electrolyte fuel cells, which do not require noble metals, are feasible.
References
Lu, S., Pan, J., Huang, A., Zhuang, L. & Lu, J. Alkaline polymer electrolyte fuel cells completely free from noble metal catalysts. Proc. Natl Acad. Sci. USA. 10.1073/pnas.0810041106 (2008).
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Pichon, A. Valuable but not noble. Nature Chem (2009). https://doi.org/10.1038/nchem.107
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DOI: https://doi.org/10.1038/nchem.107