Improved electrochemical oxidation kinetics of La_0.5Ba_0.5FeO_3-δ anode for solid oxide fuel cells with fluorine doping

Sluggish anode kinetics and serious carbon deposition are two major obstacles to developing hydrocarbon fueled solid oxide fuel cells. A highly active and stable perovskite La_0.5Ba_0.5FeO_3-δ anode material is studied in this work. The oxygen surface exchange and charge transfer steps are the rate-determining steps of the anode process, and the former is accelerated with fluorine doping on the anion sites due to the lowering of metal-oxygen bond energy. The oxygen surface exchange coefficients of La_0.5Ba_0.5FeO_3-δ and La_0.5Ba_0.5FeO_2.9-δF_0.1 at 850 °C are 1.4 × 10⁻⁴ and 2.8 × 10⁻⁴ cm s⁻¹, respectively. A single cell supported by a 300 μm-thick La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ electrolyte layer with La_0.5Ba_0.5FeO_3-δ anode shows maximum power densities of 1446 and 691 mW cm⁻² at 850 °C with wet hydrogen and methane fuels, respectively, which increase to 1860 and 809 mW cm⁻² respectively when La_0.5Ba_0.5FeO_2.9-δF_0.1 is used as the anode. The cell exhibits a short-term durability of 40 h using wet methane as fuel without carbon deposition on the anode.