Understanding the impact of sulfur poisoning on the methane-reforming activity of a solid oxide fuel cell anode

Natural gas is one of the most attractive fuels for solid oxide fuel cells (SOFCs) because of the existing fuel distribution infrastructure. Unfortunately, natural gas routinely contains small concentrations of sulfur-containing compounds, which may result in degradation in performance of fuel cells due to sulfur poisoning of Ni-based anodes. To date, the deactivation mechanism of anodes by sulfur remains poorly understood, making it extremely challenging to mitigate the problem. Here, we report our findings in unveiling the mechanism of the electrode processes on a Ni-yttria-stabilized-zirconia (Ni-YSZ) anode, enabled by highly surface-sensitive, in situ surface-enhanced Raman spectroscopy (SERS). While two different configurations of CO reformates were observed on the Ni-YSZ surface during steam methane-reforming (SMR) processes, the accumulation of S-S bonds at the sulfur-contaminated solid-gas interface significantly hinders the subsequent methane-reforming process. The identification of the key steps responsible for sulfur poisoning is vital to the development of effective strategies for minimizing the impact of sulfur on robust SOFC operations.