Insight into the activation of light alkanes over surface-modified carbon nanotubes from theoretical calculations

The activation and conversion of light alkanes (such as methane, ethane, propane and isobutane) has attracted more and more attention in both industrial and fundamental aspects. Compared to the traditional metal catalysts, carbon catalysts have environmental acceptability with inexhaustible resources. Considerable experimental work concerning the activation of light alkanes by surface-modified carbon nanotubes (CNTs) has been reported, however, both the active centers and the catalytic reaction mechanisms still remain unclear. In our theoretical calculations, a number of possible pathways for the activation of light alkanes over various types of oxygen-containing surface groups of surface-modified CNTs were theoretically explored. It was demonstrated for the first time that the diketone-like carbonyl groups residing in two neighboring phenyl rings at the edges or in the defects of CNTs show reactivity as high as the conventional metal oxide catalysts, and that the metallic CNTs usually have much higher catalytic reactivity with respect to the semi-conducting CNTs.