Abstract
In this report, ternary titanium dioxide (TiO2)/carbon nanotubes (CNTs)/reduced graphene oxide (rGO) composites were fabricated by a facile and environmentally friendly one-pot solvethermal method for the removal of Rhodamine B (RhB). Its structures were represented by X-ray powder diffraction (XRD), Raman spectrometry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocatalytic performance was tested by the degradation efficiency of RhB under UV-vis light irradiation. The experimental results indicated that photocatalytic activity improved as the ratio of CNTs:TiO2 ranged from 0.5% to 3% but reduced when the content increased to 5% and 10%, and the TiO2/CNTs/rGO-3% composites showed superior photocatalytic activity compared with the binary ones (i.e., TiO2/CNTs, TiO2/rGO) and pristine TiO2. The rate constant k of the pseudo first-order reaction was about 1.5 times that of TiO2. The improved photocatalytic activity can be attributed to the addition of rGO and CNTs, which reduced the recombination of photo-induced electron-hole pairs, and the fact that CNTs and rGO, with a high specific surface area and high adsorption ability to efficiently adsorb O2, H2O and organics, can increase the hydroxyl content of the photocatalyst surface.
Highlights
Photocatalysts have aroused extensive interest for their effective treatment of organic contaminations which were degraded into small molecules of carbon dioxide (CO2) and water [1,2]
It is obvious that the ID/IG ratio of TiO2/carbon nanotubes (CNTs)/reduced graphene oxide (rGO)-3% composites was highest, which indicated that TiO2/CNTs/rGO-3% might be a characteristic of higher level disorder structures and more active sites [34] to improve photocatalytic properties
There are three reasons for this: rGO and CNTs with large surface areas and strong adsorption ability can adsorb O2, H2O and organics to increase the content of OH· and improve photocatalytic activity [37,38]; CNTs improved the oxidation-reduction ability and decreased the recombination efficiency of photo-inducd electron-hole pairs [39]; and CNTs prevented the stacking of rGO and enlarged the distance of rGO sheets that can enrich the active sites for photocatalytic reaction [40]
Summary
Photocatalysts have aroused extensive interest for their effective treatment of organic contaminations which were degraded into small molecules of carbon dioxide (CO2) and water [1,2]. As we all know, electron-hole recombination and the low availability of sunlight have been disadvantages that have reduced the photocatalytic activity [6,7] Plentiful research works, such as those on noble metal deposition [8,9], transition metal or non-metallic elements dopants [10,11], metal oxide deposition [12,13] and preparation of carbon-based TiO2 compounds [14,15,16], have been done to solve the aforementioned problems. Gogoi et al [26] applied polymer-supported carbon dots to produce hydrogen peroxide Another latent carbon material, carbon nanotubes (CNTs), are a kind of one-dimensional nanomaterial with high surface area and excellent conductivity [27]. The as-prepared TiO2/CNTs/rGO-3% composites showed superior photocatalytic activity compared with the binary ones (i.e., TiO2/CNTs, TiO2/rGO) and pristine TiO2
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