Synergistic effects between TiO2 and carbon nanotubes (CNTs) in a TiO2/CNTs system under visible light irradiation

• Published in: Environmental technology Vol. 34; no. 17; pp. 2513 - 2519
• Main Authors: Wu, Chung-Hsin, Kuo, Chao-Yin, Chen, Shih-Ting
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 01.09.2013; Taylor & Francis Ltd
• Subjects: Applied sciences; carbon nanotubes; Catalysis; Catalytic reactions; Chemical engineering; Chemistry; Coloring Agents - isolation & purification; crystallization; Crystallization, leaching, miscellaneous separations; decolorization; decolourization; environmental technology; Exact sciences and technology; General and physical chemistry; irradiation; Light; Nanotubes, Carbon - chemistry; Naphthalenesulfonates - isolation & purification; photocatalysis; photodegradation; Photolysis; Pollution; Raman spectroscopy; Reactors; sol-gel processing; surface area; synergism; temperature; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; TiO; Titanium - chemistry; titanium dioxide; transmission electron microscopy; Triazines - isolation & purification; visible light; X-ray diffraction; X-ray photoelectron spectroscopy; Discoloration; decolourization; photodegradation; Specific surface area; visible light; Synergism; Composite material; Calcining; carbon nanotubes; Visible radiation; pH; TiO; Rate constant; Photochemical degradation; Pollutant behavior; Photocatalysis; Crystallization; X ray diffraction; Ultraviolet radiation; Transmission electron microscopy; First order; Reactive dye; Physicochemical purification; Kinetics; Titanium oxide; Catalyst
• ISSN: 1479-487X; 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2013.774058

This study synthesized a TiO ₂/carbon nanotubes (CNTs) composite via the sol-gel method. The surface characteristics of the TiO ₂/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 of the TiO ₂/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 TiO ₂/CNTs composite dosage on RR2 decolourization were determined simultaneously. The optimal calcination temperature to generate TiO ₂ and the TiO ₂/CNTs composite was 673 K, as the percentage of anatase crystallization at this temperature was highest. The specific surface area of the TiO ₂/CNTs composite and TiO ₂ were 45 and 42 m ²/g, respectively. The band gap of TiO ₂ and the TiO ₂/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 TiO ₂/CNTs composite. The RR2 decolourization rates can be approximated by pseudo-first-order kinetics; moreover, only the TiO ₂/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 TiO ₂/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 TiO ₂/CNTs composite exceeded that of TiO ₂.