A study of carbon deposition on fuel cell power plants -- morphology of deposited carbon and catalytic metal in carbon deposition reactions on stainless steel

摘要

Carbon deposited on SUS304 stainless steel (l8Cr 8Ni) has been observed by two different methods. One method was Field Emission Transmission Electron Microscopy (FE-TEM), with developed preparation for in situ observation of a cross-section of the deposited carbon from the base (SUS) to the top. The other method was X-ray Photoelectron Spectroscopy (XPS), obtaining composition--depth profiles by argon ion sputtering. Carbon was deposited on SUS304, 550deg. C, l atm, H_2/CO/CO_2 = 75/l5/10, after drained the steam-reformed natural gas composition. One result from FE-TEM identified the major form of deposited carbon was tubular in shape with a variety of diameters, ranging from approximately 7 to l00 nm. Some tubes contained metallic particles which were about 20 nm in size at their tips. Therefore, it can be established that the carbon deposition mechanism is similar to that reported for metals such as Fe, Ni, and that the deposited carbon can grow after the SUS surface is covered with deposits under the above conditions. Observations from EDX attached to FE-TEM also determined that most of the particles consisted of Fe and from XPS, that the content of Fe on the surface of the reaction plate was lower than on the unreacted sample. This indicates that carbon deposition on stainless steel was influenced by Fe rather than Ni and Cr.