Coke Resistant and Sulfur Tolerant Ni-based Cermet Anodes for Solid Oxide Fuel Cells

Thursday, 27 July 2017: 11:40
Grand Ballroom West (The Diplomat Beach Resort)
M. Li (Huazhong University of Science and Technology), B. Hua (University of Alberta), S. P. Jiang (Curtin University), and J. Li (Huazhong University of Science and Technology)
Conventional Ni-based cermet anodes of solid oxide fuel cells (SOFCs) are highly susceptible to deactivation from carbon deposition and sulfur poisoning in sulfur-containing hydrocarbon fuels. Here we propose a viable approach to substantially enhance the carbon deposition resistance and sulfur tolerance of the Ni-gadolinia doped ceria (Ni-GDC) anode. Perovskite BaCe0.9Yb0.1O3-δ (BCYb) is adopted to modify Ni-GDC anode via wet impregnation. Since BCYb nanoparticles could selectively deposit on Ni surfaces in a Ni-GDC anode backbone, a slight amount of infiltrates could lead to the excellent modification of the Ni grains without blocking the gas diffusion channels. The deposited BCYb nanoparticles decrease the exposed surfaces of Ni grains, showing promise to inhibit carbon deposition and sulfur species adsorption. BCYb has high oxygen ion conductivity, beneficial to the transportation of oxygen ions to remove the adsorbed carbon and sulfur (Fig. 1). Therefore, the stability of conventional Ni-GDC anode in wet methane fuel (3% H2O in CH4) is remarkably improved with modification of BCYb nanoparticles. The voltage of a full cell with conventional Ni-GDC anode decreases rapidly from 0.58 to 0.15 V within 6 h at 200 mA cm-2 and 750 °C. While in the case of a cell with BCYb modified Ni-GDC anode, designated as B+Ni-GDC, the cell voltage is essentially constant at around 0.65 V over a period of 48 h tested under identical conditions. Furthermore, the impregnation of BCYb nanoparticles can also improve sulfur poisoning resistance of Ni-GDC anode. The enhanced stability is observed in 500 ppm of H2S/H2 at 650 °C. The B+Ni-GDC anode manages to retain its microstructure in CH4 and H2S-containing H2 fuels, resulting in stable performance output. In addition, the electrochemical performance of Ni-GDC anode is also improved with BCYb modification in both wet H2 and CHfuels. The BCYb impregnation approach shows promising potential in the development of highly active and stable Ni-GDC based anodes for direct hydrocarbon SOFCs.

Figure 1. Schematic diagram showing carbon and sulfur removal processes on BCYb modified Ni-GDC anode.