Pan Xiulian

Enhanced Ammonia Synthesis Activity of Ru Supported on Nitrogen-Doped Carbon Nanotubes

Nitrogen-doped carbon nanotubes (NCNTs) were synthesized via chemical vapor deposition using acetonitrile as the carbon and nitrogen sources. Transmission electron microscopic characterization showed clearly tubular morphology of NCNTs with inner diameter of 10-15 nm and wall thickness of 10-20 nm. X-ray photoelectron spectroscopy (XPS) indicated that nitrogen species were incorporated into CNTs and the predominating type of nitrogen species were pyridinic and quaternary nitrogen. XPS, X-ray diffraction, and Raman spectroscopy showed that with increasing temperature the total amount of nitrogen species decreased but the nanotubes were better graphitized. Ru supported on NCNTs exhibited an obviously enhanced activity in ammonia synthesis as compared with the CNT-supported Ru catalyst. In particular, in the temperature range of 550 similar to 750 degrees C, the NCNTs obtained at 650 degrees C after deposition of Ru yielded a better activity, which was most likely attributed to the promoting effect of nitrogen doping and the graphitization of nanotubes.