title: Synergistic effects between TiO2 and carbon nanotubes (CNTs) in a TiO2/CNTs system under visible light irradiation.
abstract: This study synthesized a TiO2/carbon nanotubes (CNTs) composite via the sol-gel method. The surface characteristics of the TiO2/CNTs composite were determined by X-ray diffraction, transmission electron microscopy, specific surface area analyser, ultraviolent (UV)-vis spectroscopy, X-ray photoelectron spectroscopy and Raman spectrometer. The photocatalytic activity ofthe TiO2/CNTs composite was evaluated by decolourizing C.I. Reactive Red 2 (RR2) under visible light irradiation. Furthermore, the effects of calcination temperature, pH, RR2 concentration, and the TiO2/CNTs composite dosage on RR2 decolourization were determined simultaneously. The optimal calcination temperature to generate TiO2 and the TiO2/CNTs composite was 673 K, as the percentage of anatase crystallization at this temperature was highest. The specific surface area of the TiO2/CNTs composite and TiO2 were 45 and 42 m2/g, respectively. The band gap of TiO2 and the TiO2/CNTs composite was 2.97 and 2.71 eV by UV-vis measurements, respectively. Experimental data indicate that the Ti-O-C bond formed in the TiO2/CNTs composite. The RR2 decolourization rates can be approximated by pseudo-first-order kinetics; moreover, only the TiO2/CNTs composite had photocatalytic activity under visible light irradiation. At pH 7, the RR2 decolourization rate constant of 0.5, 1 and 2 g/L TiO2/CNTs addition was 0.005, 0.0015, and 0.0047 min(-1), respectively. Decolourization rate increased as pH and the RR2 concentration decreased. The CNTs functioned as electron acceptors, promoting separation of photoinduced electron-hole pairs to retard their recombination; thus, photocatalytic activity of the TiO2/CNTs composite exceeded that of TiO2.
authors: Department of Chemical and Materials Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan. wuch@kuas.edu.tw
authors: Chung-Hsin
authors: CH
authors: Wu
authors: Department of Environmental and Safety Engineering, National Yunlin University of Science and Technology, Douliou, Yunlin, Taiwan.
authors: Chao-Yin
authors: CY
authors: Kuo
authors: Department of Environmental and Safety Engineering, National Yunlin University of Science and Technology, Douliou, Yunlin, Taiwan.
authors: Shih-Ting
authors: ST
authors: Chen
mesh_terms: D002384:Catalysis; D004396:Coloring Agents / Q000302:isolation & purification*; D008027:Light; D037742:Nanotubes, Carbon / Q000737:chemistry*; D009282:Naphthalenesulfonates / Q000302:isolation & purification*; D010782:Photolysis; D014025:Titanium / Q000737:chemistry*; D014227:Triazines / Q000302:isolation & purification*
chemical_list: D004396:Coloring Agents; D037742:Nanotubes, Carbon; D009282:Naphthalenesulfonates; D014227:Triazines; C098610:reactive red 2; C009495:titanium dioxide; D014025:Titanium