Effect of H2O on sulfur poisoning and catalytic activity of Ni–YSZ catalysts

Solid oxide fuel cells (SOFCs) are the most desirable fuel cells for stationary power generation and are used as auxiliary power sources in transportation applications. The fuel flexibility and higher efficiency of an SOFC make it a favorable choice. The Ni-based catalysts that are currently used have coking and sulfur tolerance issues. The current work focuses on studying the effect of H2S on the catalytic activity of Ni–YSZ catalysts, for various methane conversion reactions. Steady-state reaction experiments are complemented by temperature programmed desorption (TPD) studies and post-reaction characterization using TEM and X-ray absorption fine structure (XAFS) spectroscopy. It is found that oxidation sites are less susceptible to sulfur poisoning, and that the presence of water in the feed increases deactivation due to sulfur. Interactions between sulfur and the YSZ support are also observed. These results provide further insight into the deactivation process due to sulfur over Ni–YSZ catalysts, and hold relevance in determining operating conditions of internally reforming fuel cells for sulfur-contaminated hydrocarbon fuels.

Graphical abstractEffect of H2S and H2O in steady-state methane oxidation over Ni–YSZ.Figure optionsDownload full-size imageDownload high-quality image (100 K)Download as PowerPoint slideResearch highlights▶ Ni sites for methane oxidation and decomposition have different sulfur poisoning characteristics. ▶ Effect of H2S on catalytic activity of Ni–YSZ is more severe in the presence of water. ▶ S interactions with YSZ substrate were observed. ▶ XAFS analysis showed oxidation of Ni sites with exposure to H2S.