Mitigation of Sulfur Poisoning of Ni/Zirconia SOFC Anodes by Antimony and Tin

Abstract

Surface Sb/Ni and Sn/Ni alloys were found to efficiently minimize the negative effects of sulfur on the performance of Ni/zirconia anode-supported solid oxide fuel cells (SOFC). Prior to operating on fuel gas containing low concentrations of H 2 S, the nickel/ zirconia anodes were briefly exposed to antimony or tin vapor, which only slightly affected the SOFC performance. During the subsequent exposures to 1 and 5 parts per million H 2 S, increases in anodic polarization losses were minimal compared to those observed for the standard nickel/zirconia anodes. Post-test x-ray photoelectron spectroscopy analyses showed that Sb and Sn tended to segregate to the surface of Ni particles, and further confirmed a significant reduction of adsorbed sulfur on the Ni surface in Ni-Sn and Ni-Sb samples compared to the Ni. The effect may be the result of weaker sulfur adsorption on bimetallic surfaces, adsorption site competition between sulfur and Sb or Sn on Ni, or other factors. The use of dilute binary alloys of Ni-Sb or Ni-Sn in the place of Ni, or brief exposure to Sb or Sn vapor, may be an effective means to counteract the effects of sulfur poisoning in SOFC anodes and Ni catalysts. Other advantages, including the suppression of coking, are also expected.

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

“…3). Similar decreases in electrochemical performance with Sn content have been observed previously [25,26,30].…”

“…XPS analysis of a reduced 2% SnIeNi/YSZ anode, prepared in the preliminary phase of this work, indicated a Sn/Ni weight ratio of 22% showing that most of the Sn in the Ni particle was concentrated at the surface of the particle. This high concentration of Sn at the Ni surface may lead to Sn occupying the electrochemically active Ni sites [26,30] thereby increasing the polarization resistance. …”

Effect of Pd-impregnation on performance, sulfur poisoning and tolerance of Ni/GDC anode of solid oxide fuel cells

“…This may indicate that the impregnated Pd nanoparticles diminishes, and inhibits the formation of Ce 2 O 2 S between ceria and H 2 S [65]. The significant reduced modification or change of the morphology of Ni and in particular GDC phases may also be the results of weaker sulfur adsorption on Pd impregnated Ni/ GDC anodes, similar to that reported on NieSb and NieSn bimetallic surfaces [66].…”

Performance evaluation of WNi–CeO2 as anode in a solid oxide fuel cell fed by simulated biogas mixtures

“…Different strategies have been adopted for the development of more durable and active anode. Among them, doping nickel catalysts with small amounts of the other materials is a popular and effective approach taken to alleviate carbon deposition and sulphur poisoning [16,17]. Ceramics based on CeO 2 exhibit mixed ionic and electronic conductivity in a reducing atmosphere due to reduction of Ce 4þ to Ce 3þ .…”