Effect of volatile boron species on the electrocatalytic activity of cathodes of solid oxide fuel cells

Abstract

The effect of volatile boron species on the electrocatalytic activity, microstructure and phase stability of conventional La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) and nano-structured LSCF infiltrated Gd0.1Ce0.9O1.95 (LSCF-GDC) electrodes of solid oxide fuel cell (SOFC) is studied. The cathodes were heat-treated at 700–800°C for 7-30 days in air in the presence of borosilicate glass. Heat-treatment in the presence of glass has a significantly detrimental effect on the microstructure and electrochemical activity of the cathodes. For example, the electrode polarization resistance (RE) of a freshly prepared LSCF cathode is 0.07 Ω cm2 at 800°C, and increases significantly to 84 Ω cm2 after heat-treated at 800°C for 30 days in the presence of glass. Similar degradation behavior was also observed on infiltrated LSCF-GDC electrodes. Present study shows that boron is not chemically compatible with LSCF and the interaction results in the disintegration and decomposition of LSCF perovskite structure, forming LaBO3 and Fe2O3. A reaction mechanism between volatile boron species and LSCF electrodes is proposed.