Bismuth doped La0.75Sr0.25Cr0.5Mn0.5O3-δ perovskite as novel redox-stable efficient anode for solid oxide fuel cell
La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM) perovskite oxide is a potential ceramic material as anode for solid oxide fuel cell. This work aims to improve its catalytic activity for electrochemical anode reaction by partially replacing lanthanum with bismuth. The Bi-doped LSCM is successfully fabricated at 1100 oC in air and is stable in hydrogen at 850 oC although Bi2O3 is not stable under the anodic conditions. Bi doping increases the symmetry of crystal structure, the concentration of surface oxygen species, the oxygen vacancy concentration associated with the decrease in average Mn valence, and the sinterability meanwhile decreases the electronic conductivity. When single phase LSCM is used as the electrode, Bi doping increases the catalytic activity by a factor up to 2.2 as determined with symmetrical cells based on perovskite structured electrolytes. The electrode performance is at least 40 % higher than those ever reported for LSCM doped with various elements. The performance is even higher than LSCM-based composite electrodes and nanostructured composites. In addition, Bi doping increases the peak power density of electrolyte supported single cell such as from 237 mW cm-2 to 386 mW cm-2 at 800 oC when humidified H2 is used as the fuel and from 119 mW cm-2 to 222 mW cm-2 for syngas fuel. The performance obtained with single phase anode is about twice as high as those reported with LSCM-YSZ nanocomposite and graded composite anodes. The performance is even higher than that reported with Pd doped (La,Sr)CrO3 where plenty of exsolved Pd nanoparticles are functioned as the electrocatalyst. The performance is competitive with the widely used Ni-based cermet anodes under similar conditons. Finally, the Bi-doped LSCM based cells show good stability operated with hydrogen and syngas fuels.
- This article is part of the themed collection: Journal of Materials Chemistry A HOT Papers