Tolerance tests of H2S-laden biogas fuel on solid oxide fuel cells

Biogas is a variable mixture of methane, carbon dioxide and other gases. It is a renewable resource which comes from numerous sources of plant and animal matter. Ni-YSZ anode-supported solid oxide fuel cell (SOFC) can directly use clean synthesized biogas as fuel. However, trace impurities, such as H₂S, Cl₂ and F₂ in real biogas can cause degradation in cell performance. In this research, both uncoated and coated Ni-YSZ anode-supported cells were exposed to three different compositions of synthesized biogases (syn-biogas) with 20 ppm H₂S under a constant current load at 750-850 °C and their performance was evaluated periodically using standard electrochemical methods. Postmortem analysis of the SOFC anode was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results show that H₂S causes severe electrochemical degradation of the cell when operating on biogas, leading to both complete electrochemical and mechanical failure. The Ni-CeO₂ coated cell showed excellent stability during CH₄ reforming and some tolerance to H₂S contamination.