Comparison of the electrochemical properties of impregnated and functionally gradient LaNi0.6Fe0.4O3–Gd0.2Ce0.8O2 composite cathodes for Solid Oxide Fuel Cell

Abstract

This study investigates the electrochemical properties of three different configurations of LaNi0.6Fe0.4O3 (LNF)-based cathodes for Solid Oxide Fuel Cell (SOFC). The results show functionally gradient LNF cathode and Gd0.2Ce0.8O2 (GDC)-impregnated LNF cathode both reveal the better electrochemical properties compared to that of 70 wt.% LNF–30 wt.% GDC cathode. Functionally gradient LNF cathode with better interface of LNF/GDC/ScSZ can be achieved by the gradual change in composition from electrolyte to cathode, resulting in the decline in charge transfer resistance and gas phase diffusion resistance, therefore the decline in specific cathode polarization resistance (Rp). Whereas, the dramatic decrease in Rp for GDC-impregnated LNF cathode is mainly attributed to the extended triple phase boundary (TPB) and enhanced oxide ion conductivity. The nano-sized GDC particle on LNF backbone with high porosity would allow gas phase molecules to easily diffuse to the LNF/GDC/ScSZ boundaries, which significantly enhances cathode activities for oxygen reduction reaction (ORR). The GDC-impregnated LNF cathode reveals the lowest Rp, the lowest activation energies of Rp and the lowest activation energy of ORR among three cathode configurations. Noticeably, the cathode performance can be significantly improved by impregnating nano-sized GDC particles into LNF porous backbone.