Carbon deposition on Ni/YSZ anode SOFC for direct methane steam reforming

Abstract

Carbon deposition on Ni-YSZ anode SOFC for direct methane steam reforming Haiyang Li Solid Oxide Fuel Cells (SOFCs) are electrochemical devices that produce electricity directly from oxidizing fuels. Compared to direct combustion of hydrogen to generate power, it has a big advantage in aspects from efficiency and safety when using hydrogen as the fuel of SOFCs. Nowadays, about 50% of the hydrogen of world demand is derived from the natural gas. Hydrocarbon reforming is one of the conventional methods to convert nature gas into hydrogen. While, considering the difficulty in storage and transportation of hydrogen, we can utilize the supporting materials on the anode side of SOFCs as catalyst to generate hydrogen via hydrocarbon reforming process and pour the hydrogen as fuel into the SOFC system. Among many kinds of anode materials that have a good catalytic reforming and electrochemical reactivity, Ni/YSZ is the most commonly used because of its cost-effective and well suitable for anode-supported fuel cell design requirements. While there are also some drawbacks, the biggest one is the performance degradation of fuel cell caused by solid carbon formation on the surface of the Ni/YSZ anode cermet, which may block gas diffusion tunnel. Moreover, the accumulation of carbon on catalysts can crack the cell. In the present report, methane steam reforming and carbon deposition on Ni catalyst from the thermodynamic and kinetic views are discussed. The process of carbon deposition on Ni catalyst is also described. In order to face the challenge, some measures have been taken to suppress the effect including optimizing system parameters, addition of other metal elements and synthesizing smaller Ni particle catalyst. In the future, a lot of work should be done on adjusting catalyst compositions, feed compositions, and reaction conditions, especially on developing new materials that fit the system perfectly. For the application in SOFC system, it is reported to have less carbon deposition by adjusting the current density of the cell. More efforts are still to be made from the system aspect.