Materials scientists from Spain and the UK have made a cathode material that allows solid oxide fuel cells (SOFCs) to be used at lower temperatures.

Albert Tarancón and colleagues at the University of Barcelona, and Imperial College, London found that the oxide GdBaCo₂O_5+? performed very well in the temperature range 500-700 °C.

SOFCs consist of three main components: an anode, cathode and electrolyte. The cathode catalyses the reduction of oxygen at its surface and allows ions to be transported to the electrolyte. At the anode, the fuel (for example, hydrogen) is oxidised.

Lowering the temperature that SOFCs operate at reduces costs and improves durability. However, the cathode performance is the limiting factor when lowering the temperature. New cathode materials with higher catalytic activities are needed, in which the oxide ions are able to diffuse easily.

According to Tarancón, the oxygen transport properties and electrical performance of the perovskite-structured oxide were comparable to other excellent cathodes. He also suggested that 'its structural characteristics suggest a new family of SOFCs cathode materials based on layered perovskites'.

Peter Slater, a materials chemist at the University of Surrey, Guildford, UK, praised Tarancón's research, saying 'they elegantly demonstrate high oxygen surface exchange properties, along with low activation energies for both surface exchange and oxide ion diffusion' and agreed that the family has great promise as cathode materials.

Susan Batten