Enhanced sulfur tolerance of nickel-based anodes for oxygen-ion conducting solid oxide fuel cells by incorporating a secondary water storing phase

In this work, a Ni+BaZr_0.4Ce_0.4Y_0.2O_3-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 Sm_0.2Ce_0.8O_1.9 (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.