Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1416505 | Carbon | 2011 | 7 Pages |
Surface defects were created on carbon nanotubes (CNTs) by catalytic steam gasification or catalytic etching with iron as catalysts. The structure and morphology of the etched CNTs were studied by transmission electron microscopy (TEM) and scanning tunneling microscopy (STM). The electronic structure of the etched CNTs was investigated by ultraviolet photoelectron spectroscopy (UPS). The etched CNTs were treated by nitric acid to obtain oxygen-containing functional groups. The amount and the thermal stability of these groups were studied by temperature-resolved X-ray photoelectron spectroscopy (XPS). Temperature-programmed desorption with ammonia as a probe molecule (NH3-TPD) was employed to investigate the interaction of the surface defects with foreign molecules in gas phase. TEM and STM studies disclosed the presence of surface defects especially edge planes on the etched CNTs. Etching of CNTs led to a less pronounced p-π band than the as-is CNTs, as evidenced by UPS studies. The XPS and NH3-TPD studies demonstrated that the defects on the CNTs enhanced the reactivity of the exposed surfaces allowing obtaining a higher degree of oxygen functionalization and more active adsorption sites.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Created surface defects on carbon nanotubes visualized by STM. ► Oxygen anchored on etched CNTs more stable as indicated by temperature-resolved XPS. ► Etching led to a less pronounced p-π band as disclosed by UPS. ► Defects active for adsorption of ammonia as evidenced by TPD.