A high-performance cathode for the next generation of solid-oxide fuel cells

Fuel cells directly and efficiently convert chemical energy to electrical energy¹. Of the various fuel cell types, solid-oxide fuel cells (SOFCs) combine the benefits of environmentally benign power generation with fuel flexibility. However, the necessity for high operating temperatures (800–1,000 °C) has resulted in high costs and materials compatibility challenges². As a consequence, significant effort has been devoted to the development of intermediate-temperature (500–700 °C) SOFCs. A key obstacle to reduced-temperature operation of SOFCs is the poor activity of traditional cathode materials for electrochemical reduction ofoxygen in this temperature regime². Here we present Ba_0.5Sr_0.5-Co_0.8Fe_0.2O_3−δ(BSCF) as a new cathode material for reducedtemperature SOFC operation. BSCF, incorporated into a thin-film doped ceria fuel cell, exhibits high power densities (1,010mWcm⁻²and 402mWcm⁻²at 600 °C and 500 °C, respectively) when operated with humidified hydrogen as the fuel and air as the cathode gas. We further demonstrate that BSCF is ideally suited to ‘single-chamber’ fuel-cell operation, where anode and cathode reactions take place within the same physical chamber³. The high power output of BSCF cathodes results from the high rate of oxygen diffusion through the material. By enabling operation at reduced temperatures, BSCF cathodes may result in widespread practical implementation of SOFCs.