The Preparation And Performance Of Functional Anode Materials For Direct Hydrocarbon Utilization Of Solid Oxide Fuel Cell

Solid oxide fuel cell (SOFC) will inevitably exert a great impact on the development of the next generation energy technology and the hydrogen economy as fossil fuels are running out. SOFC requires hydrogen as the fuel, but viable near-term applications will need to use the more readily available hydrocarbons, such as methane. However, conventional Ni-based anode suffers a number of drawbacks in systems where hydrocarbon fuel is used such as carbon deposition since Ni is a good catalyst for hydrocarbon cracking reaction. Carbon deposition covers the active sites of the anode, resulting in rapid, irreversible cell deactivation. Therefore, much effort has been devoted in developing SOFC running on hydrocarbon fuels instead of hydrogen. In order to use the hydrocarbon fuel directly, the anode must be able to catalyze the reforming reaction or direct oxidation reaction of fuel to prevent carbon deposition. Therefore, the research and development of novel anode materials and anode structures for direct hydrocarbon-fueled SOFC has become one of the key factors in technological competition internationally.This study is focused on the electrochemical performance of perovskite-type materials based on doped LaGaO₃. La_0.7Sr_0.25Cr_0.5Mn_0.5O_3-δ(LSGMC) is used as electrolyte and (Pr0.7Ca_0.3)_0.9MnO₃(PCM) and La_0.7Sr_0.25Cr_0.5Mn_0.5O_3-δ (LSCM) are used as cathode and anode material, respectively. The performance of the conventional electrolyte-supported cell LSCM/LSGMC/PCM while operating on humidified hydrogen is modest with a maximum power density of 182,125 and 80mW/cm² at 850℃,800℃and 750℃, respectively, the corresponding values for the cell while operating on ethanol steam are 169,120 and 68mW/cm², respectively. Cell stability tests indicate no significant degradation in performance after 60 h of cell testing when LSCM anode is exposed to ethanol steam at 750℃. Almost no carbon deposition are detected after testing in ethanol steam at 750℃for >60h on the LSCM anodes, suggesting that carbon deposition is limited during cell operation.A dual-layer structure anode running on ethanol steam is fabricated by tape casting and screen-printing method, the addition of a LSCM–CeO₂ catalyst layer to the supported anode layer yields better performance in ethanol fuel. The effect that the synthesis conditions of the catalyst layer have on the performances of the composite anodes is investigated. The maximum power density of the cell with the Ni-ScSZ13 anode reaches 710 and 669 mW/cm² at 850℃running on hydrogen and ethanol steam, respectively, and the maximum power density of the cell with the Ni-ScSZ10 anode reaches 521 and 486 mW/cm² at 850℃running on hydrogen and ethanol steam, respectively. No significant degradation in performance has been observed after 144 h of cell testing when the Ni-ScSZ13 anode is exposed to ethanol steam at 700℃. Very little carbon is detected on the anode, suggesting that carbon deposition is limited during cell operation. Consequently, the LSCM–CeO₂ catalyst layer on the surface of the supported anode layer makes it possible to have good stability for long-term operation in ethanol fuel due to low carbon deposition.