Effects of nitrogen doping on the structure of carbon nanotubes (CNTs) and activity of Ru/CNTs in ammonia decomposition

Nitrogen doping on carbon nanotubes (CNTs) was carried out using N2 microwave plasma at the powers of 200 and 400 W. N2 physisorption, XPS, XRD, TEM, and CO chemisorption were employed to investigate the effects of nitrogen doping on the structure of CNTs and the state of Ru particles supported on CNTs. The bulk structure and the surface texture of CNTs remain unchanged by such nitrogen doping. Two types of nitrogen species, pyridinic and quaternary nitrogen, were found on the surface of nitrogen doped CNTs. Pyridinic nitrogen atom may have a strong interaction with Ru. The average Ru particle size decreases with the increase of pyridinic nitrogen content. The activity of Ru/CNTs catalysts in ammonia decomposition is dependent on the dispersion of Ru particles and remaining nitrogen on the surface of CNTs.