One-step fabrication of Ag/RGO doped TiO2 nanotubes during anodization process with high photocatalytic performance

Abstract

Reduced graphene oxide (RGO) and Ag nanoparticles were incorporated simultaneously with two-step anodic TiO 2 nanotube through anodization process, and their photocatalytic activity was investigated in the degradation of 2,4-dichlorophenol (2,4-DCP). Furthermore, the optical properties and photocatalytic degradation efficiency were examined as a function of Ag NPs concentration in Ag/RGO-TiO 2 nanotube. Morphological characterization showed that Ag NPs and RGO sheets were well-doped inside and outside the TiO 2 nanotubes' walls. Meanwhile, X-ray diffraction and EDX analysis confirmed the existence of both Ag NPs and RGO. The optical investigation revealed that the incorporation of Ag NPs and RGO with TiO 2 nanotubes improved the light absorbance and the narrowing of TNT bandgap energy (from 2.85 to 2.35 eV). Therefore, among the various samples, Ag50/RGO-TNTs photocatalyst had the most optimal performance, degrading 96% and 66% of 2,4-DCP under UV and visible light irradiation, respectively. The kinetic study confirmed that degradation reactions over all photocatalysts followed zero-order kinetics. Finally, the recovery test of the optimum sample (Ag50/RGO-TNT) showed 6% reduction following 5-cycle photocatalytic degradation of 2,4-DCP under UV irradiation. Keywords Anodic nanotube • Ag nanoparticles • RGO • Photocatalytic degradation List of symbols UV Ultra-violet radiation v Anodization voltage (V) D Mean crystalline size of TiO 2 V Cell volume of TiO 2 d Interplanar spacing E g Energy of band gap h Planck's constant K Scherrer constant C Concentration of pollutant (ppm) C 0 Initial concentration of pollutant (ppm) t Photocatalytic degradation time (min) k abs Apparent rate constant (ppm/min) R 2 Correlation coefficient Greek symbols α Absorption coefficient ϑ Frequency of vibration Subscripts h, k, l Miller coordinates * Neda Gilani

Preparation of Functionalized Mesoporous Silica as a Novel Carrier and Immobilization of Laccase

“…In recent years, with the rapid development of industries, the environmental problems are also increasing rapidly. 2,4-dichlorophenol (2,4-DCP) is a kind of toxic and carcinogenic organic pollutant, which seriously endangers human and animal health [1]. Therefore, 2,4-DCP is considered as a priority persistent pollutant, which is usually found in agricultural sites, pulp and paper mill wastewater [2].…”

Enhanced Photocatalytic CO2 Reduction to CH4 Using Novel Ternary Photocatalyst RGO/Au-TNTAs

“…The RGO peaks in the ternary composite also confirm the good decoration of RGO nanosheets on TNTAs. However, the strong peak appearing at 807 cm −1 in pure TNTAs is ascribed to the symmetrical stretching vibration band of TiO 2 (Ti-O-Ti) [32]. The peak between 2500-2250 cm −1 for TNTs and Au-TNTs could be due to other oxygen-containing functional groups.…”

“…The TiO 2 lattice vibration in doped TNTAs moved towards a lower frequency after the addition of Au NPs and RGO nanosheets, indicating the successful development of the ternary RGO/Au-TNTAs nanocomposite. Moreover, the absorption peak at 800 cm −1 in RGO/Au-TNTAs is attributed to the Ti-O-C band as a result of the interaction between the functionalities of Au and RGO with TNTAs [32,56,66].…”

“…The FTIR spectra revealed the successful reduction of the oxygencontaining groups in GO to form RGO as shown in Figure 6 (a,b). The GO exhibited various stretching vibration bands of 3400 cm −1 representing the hydroxyl (O-H) group, 1633 cm −1 for the unoxidized graphitic domains (C=C), 1384 cm −1 for the carboxyl (C-O) group and at 1121 cm −1 for alkoxy and epoxy pairs (C-O) [32,56,65]. After the reduction, all the peaks corresponding to the stretching vibration of oxygen-containing functional groups (O-H and C-O) were significantly reduced as a result of the de-oxygenation process [25].…”

“…Tremendous efforts have been devoted to addressing these TNTAs drawbacks through various strategies such as band gap engineering [25,26], coupling with metals and metal oxides [27,28], and doping with inorganic and organic materials [29,30]. However, the incorporation of TNTAs with noble metals such as silver (Ag), platinum (Pt), and gold (Au) was found to be the most effective strategy to enhance the photocatalytic performance by suppressing the recombination of photogenerated charges [31,32]. This photocatalytic enhancement is attributed to the unique characteristic of localized surface plasmon resonance (LSPR).…”