Carbon tolerance, electrochemical performance and stability of solid oxide fuel cells with Ni/yttria stabilized zirconia anodes impregnated with Sn and operated with methane

摘要

Carbon formation on conventional Ni/YSZ anodes is a major problem when solid oxide fuel cells (SOFC) are operated with hydrocarbons. Carbon formation reduces the operational stability and lifetime of SOFC. In this paper, the influence of the addition of Sn to Ni/VSZ anodes (100 micron) on the carbon tolerance, electrochemical performance and stability of the anodes when operated with CH_4 is studied. Sn is incorporated into the Ni/YSZ anodes of electrolyte-supported SOFC by impregnation (1 and 5 wt% Sn with respect to Ni). Addition of Sn to Ni/YSZ anodes does not reduce the carbon formation when SOFC are operated with CH_4 at low steam to carbon ratios (<0.03) and high temperatures (1013 and 1073 K). Severe coking and metal dusting occurs on Sn-impregnated Ni/YSZ anodes when operated at OCV and 1073 K with dry CH_4. Addition of higher amounts of Sn (5%) reduces electrochemical performance of Ni/ YSZ anodes in H_2 and also reduces the carbon gasification rates, leading to higher carbon accumulation. The Sn content in the anode decreases after operation at 1073 K for 30 h. Hence retaining Sn in the anode might be difficult in actual stack operations at high temperatures (1073 K) and long durations (>40,000 h).