Fluorine Anion-Doped Ba_0.6Sr_0.4Co_0.7Fe_0.2Nb_0.1O_3-δ as a Promising Cathode for Protonic Ceramic Fuel Cells

The widespread application of protonic ceramic fuel cells is limited by the lack of oxygen electrodes with excellent activity and stability. Herein, the strategy of halogen doping in a Ba_0.6Sr_0.4Co_0.7Fe_0.2Nb_0.1O_3-δ (BSCFN) cathode is discussed in detail for improving cathode activity. Ba_0.6Sr_0.4Co_0.7Fe_0.2Nb_0.1O_3-x-δF_x (x = 0, 0.05, 0.1) cathode materials are synthesised by a solid-phase method. The XRD results show that fluorine anion-doped BSCFN forms a single-phase perovskite structure. XPS and titration results reveal that fluorine ion doping increases active oxygen and surface adsorbed oxygen. It also confines chemical bonds between cations and anions, which enhances the cathode’s catalytic performance. Therefore, an anode-supported single cell with the configuration of Ni-BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ (BZCYYb)|BZCYYb|Ba_0.6Sr_0.4Co_0.7Fe_0.2Nb_0.1O_3-0.1-δF_0.1 (BSCFN-F_0.1) achieved a high peak power density of 630 mW cm⁻² at 600 °C. Moreover, according to the symmetrical cell test, the BSCFN-F_0.1 electrode demonstrated a superb stability for nearly 400 h at 600 °C. This work focuses on the influence of fluorine anion incorporation upon the performance of cathode materials. It also analyses and discusses the effects of different fluorine ion incorporation amounts to occupy different oxygen positions.