Catalytic Activity of Ni-YSZ composite as Anode for Methane Oxidation in Solid Oxide Fuel Cells

Natural gas has been exploited as an available energy source for solid oxide fuel cells in recent years. However, the problem of carbon deposition that forms on nickel-based anodes by using direct methane results in performance failure of cells. It is well known that the catalytic partial oxidation of methane is a good solution to suppress carbon formation. Herein, we present an investigation of the catalytic activity of Ni/YSZ cermet anodes as a function of the CH4/O-2 flow rate ratio (1 <= R-in <= 5). The behavior of methane catalytic activity was characterized using mass spectrometry (MS) and temperature-programmed oxidation (TPO). The catalytic activity of methane oxidation at 700 degrees C showed that Ni oxidation occurred at R-in <= 1.67. A basic equilibrium to prevent carbon deposition and Ni oxidation occurred at R-in <= 2.5, which exhibited the best activity among the Ni/YSZ electrodes. Through the electrochemical measurements and impedance spectroscopy analysis of the cell, it was proved that the cell possessed the lowest ohmic resistance and optimized output performance at R-in = 2.5. In addition, a stable cell operation at 0.9 V was guaranteed without serious degradation.