Facile Synthesis of Phosphate-Functionalized MWCNT-TiO Nanocomposites as Efficient Photocatalysts and Insights into the Roles of Nanostructured Carbon.

Effectively contacted multiwalled carbon nanotube (MWCNT)-titanium dioxide nanocomposites and phosphate-functionalized MWCNT-TiO composites have been successfully synthesized by simple one-pot phase-separated hydrolysis-solvothermal processes. The key to this synthetic strategy is to disperse MWCNTs uniformly in Ti(OBu) in advance and then to put them into the toluene organic phase. The as-prepared nanocomposites between TiO and the correct amount of MWCNT exhibits higher activity in the photocatalytic degradation of rhodamine B than that with the resulting TiO , although the activity in the photocatalytic degradation of gas-phase aldehyde and liquid-phase phenol is lower. Interestingly, the functionalization of MWCNTs with an appropriate amount of phosphoric acids prior to the synthesis could greatly improve the activity of the MWCNT-TiO nanocomposites for the degradation of aldehyde and phenol, even superior to that of commercial P25 TiO . Based on the measurements of atmosphere-controlled surface photovoltage spectra and O temperature-programmed desorption, it is suggested that MWCNTs are favorable to increase rhodamine B adsorption on the composite to promote the photosensitization oxidation reactions, whereas it is unfavorable for the adsorption of O and responsible for the low photocatalytic activity for the degradation of colorless pollutants. Phosphate functionalization greatly enhances the amount of O adsorbed on the MWCNT, which leads to significant charge separation, and thus, to significant photoactivity for the degradation of colored and colorless pollutants of the nanocomposites.