Enhanced Sulfur Tolerance of Nickel-Based Anodes for Oxygen-Ion Conducting Solid Oxide Fuel Cells by Incorporating a Secondary Water Storing Phase

Abstract

In this work, a Ni+BaZr0.4Ce0.4Y0.2O3-δ (Ni+BZCY) anode with high water storage capability is used to increase the sulfur tolerance of nickel electrocatalysts for solid oxide fuel cells (SOFCs) with an oxygen-ion conducting Sm0.2Ce0.8O1.9 (SDC) electrolyte. Attractive power outputs are still obtained for the cell with a Ni+BZCY anode that operates on hydrogen fuels containing 100-1000 ppm of H2S, while for a similar cell with a Ni+SDC anode, it displays a much reduced performance by introducing only 100 ppm of H2S into hydrogen. Operating on a hydrogen fuel containing 100 ppm of H2S at 600 °C and a fixed current density of 200 mA cm-2, a stable power output of 148 mW cm-2 is well maintained for a cell with a Ni+BZCY anode within a test period of 700 min, while it was decreased from an initial value of 137 mW cm-2 to only 81 mW cm-2 for a similar cell with a Ni+SDC anode after a test period of only 150 min. After the stability test, a loss of the Ni percolating network and reaction between nickel and sulfur appeared over the Ni+SDC anode, but it is not observed for the Ni+BZCY anode. This result highly promises the use of water-storing BZCY as an anode component to improve sulfur tolerance for SOFCs with an oxygen-ion conducting SDC electrolyte.