Point defects largely govern the electrochemical properties of oxides: at low defect concentrations, conductivity increases with concentration; however, at higher concentrations, defect–defect interactions start to dominate^{1, 2}. Thus, in searching for electrochemically active materials for fuel cell anodes, high defect concentration is generally avoided. Here we describe an oxide anode formed from lanthanum-substituted strontium titanate (La-SrTiO₃) in which we control the oxygen stoichiometry in order to break down the extended defect intergrowth regions and create phases with considerable disordered oxygen defects. We substitute Ti in these phases with Ga and Mn to induce redox activity and allow more flexible coordination. The material demonstrates impressive fuel cell performance using wet hydrogen at 950 °C. It is also important for fuel cell technology to achieve efficient electrode operation with different hydrocarbon fuels^{3, 4}, although such fuels are more demanding than pure hydrogen. The best anode materials to date—Ni-YSZ (yttria-stabilized zirconia) cermets⁵—suffer some disadvantages related to low tolerance to sulphur⁶, carbon build-up when using hydrocarbon fuels⁷ (though device modifications and lower temperature operation can avoid this^{8, 9}) and volume instability on redox cycling. Our anode material is very active for methane oxidation at high temperatures, with open circuit voltages in excess of 1.2 V. The materials design concept that we use here could lead to devices that enable more-efficient energy extraction from fossil fuels and carbon-neutral fuels.

1. School of Chemistry, University of St Andrews, St Andrews, Fife KY16 9ST, UK
2. Department of Inorganic Chemistry, University of La Laguna, 38200, Canary Islands, Spain
3. †Present addresses: Department of Inorganic Chemistry, University of La Laguna, 38200, Canary Islands, Spain (J.C.R.-M.); Instituto de Ciencia de los Materiales ICMAB-CSIC, 08193, Barcelona, Spain (J.C.-V.)

Correspondence to: John T. S. Irvine¹ Correspondence and requests for materials should be addressed to J.T.S.I. (Email: jtsi@st-and.ac.uk).

Received 16 September 2005; Accepted 1 November 2005

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