BaCo_1-xNbxO_3−δ as a Promising Cathode for Intermediate Temperature Solid Oxide Fuel Cells

Nb₂O₅ doped BaCoO_3-δ was synthesized using traditional solid-state reaction method. The electrochemical performance, physical properties and rate-determining step of BaCo_1-xNb_xO_3−δ as a cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs) were investigated. The introduction of Nb in BaCo_0.8Nb_0.2O_3-δ(BCN20)brings a stable cubic phase and a relative lower TEC (∼16.94×10-6 K⁻¹) compared BCN20 with other Co-based perovskites. The oxygen vacancy concentration (δ) for BCN20 symmetrical cell is 0.153. The area specific resistance (ASR) of BCN20 symmetrical cell is merely 0.0397 Ω⋅cm² at 700 °C. Base on the above findings, BCN20 has a great electrochemical performance as a cathode material for IT-SOFCs. Furthermore, we studies the reaction mechanism of BCN20 and concluded that desorption and diffusion of oxygen molecules is the oxygen reduction rate limiting step. Finally, full cell with BCN20 as cathode was tested and peak power density was measured to be 1042 mW⋅cm⁻² at 800 °C.