Carbon nanotubes are modified through nitrogen doping using a ball milling-calcination method.With urea,pyridine,and melamine as nitrogen source,respectively,nitrogen doping is carried out at different carbon to nitrogen ratios and calcination temperature.By comparing the original carbon nanotubes,it is found that the optimal nitrogen doping calcination temperature is 600℃.The conversion rate of NO over the carbon nanotubes with melamine as nitrogen source and under a carbon to nitrogen ratio of 1∶0.5 is higher than that over the ones with other nitrogen sources.The conversion rate of NO reaches the peak at 350℃.Combined with the characterizations such as SEM,BET,XRD,FTIR,and XPS,it is demonstrated that nitrogen doping mainly exists in the forms of pyridine nitrogen,pyrrole nitrogen,and graphite nitrogen.Meanwhile,nitrogen-containing functional groups are added on the surface of carbon nanotubes,changing the charge state of carbon and nitrogen atoms,providing more active sites for the SCR reaction.
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