Improved performance of IT-SOFC by negative thermal expansion Sm0.85Zn0.15MnO3 addition in Ba0.5Sr0.5Fe0.8Cu0.1Ti0.1O3−δ cathode

Abstract

To improve performance of intermediate temperature solid oxide fuel cells (IT-SOFCs), the negative thermal expansion (NTE) material Sm0.85Zn0.15MnO3 (SZM) is introduced in Ba0.5Sr0.5Fe0.8Cu0.1Ti0.1O3−δ (BSFCT) cathode. XRD results indicate that BSFCT, SZM and Ce0.8Sm0.2O2−δ (SDC) oxides have good chemical compatibility up to 1173 K. The average linear thermal expansion coefficient of BSFCT–xSZM (x = 0, 10, 20 and 30 wt.%) decreases markedly from 29.2 × 10−6 K−1 for x = 0 wt.% to 15.6 × 10−6 K−1 for x = 30 wt.%. The electrochemical performance of single cells with configuration of NiO–BZCY|SDC|BSFCT–xSZM is comparatively investigated in the 773–973 K. The best performance is observed for x = 20 wt.%, which should be caused by the balance between thermal matching of cathode/electrolyte layers and oxygen reduction reaction activity of composite cathodes. The corresponding peak power density in the 773–973 K is 136–918 mW cm−2, which is 249%–64% higher than that (39–559 mW cm−2) with single BSFCT cathode. Due to the existence of electron blocking layer at anode/electrolyte interface, the open circuit voltage of all cells is higher than 1.0 V. In short, the introduction of NTE oxide in conventional cathode materials may provide an effective strategy to enhance the performance of IT-SOFCs with electron blocking layer.