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One-step fabrication of Ag/RGO doped ­TiO2 nanotubes during anodization process with high photocatalytic performance Kamyar Khoshsirat Janekbary1 · Neda Gilani2 · Azadeh Ebrahimian Pirbazari1

© Springer Science+Business Media, LLC, part of Springer Nature 2020

Abstract Reduced graphene oxide (RGO) and Ag nanoparticles were incorporated simultaneously with two-step anodic ­TiO2 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–TiO2 nanotube. Morphological characterization showed that Ag NPs and RGO sheets were well-doped inside and outside the T ­ iO2 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 ­TiO2 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 ­TiO2 V Cell volume of ­TiO2 d Interplanar spacing Eg Energy of band gap h Planck’s constant K Scherrer constant C Concentration of pollutant (ppm) C0 Initial concentration of pollutant (ppm) t Photocatalytic degradation time (min) kabs Apparent rate constant (ppm/min) R2 Correlation coefficient

* Neda Gilani [email protected]; [email protected] 1



Fouman Faculty of Engineering, College of Engineering, University of Tehran, Fouman, P. O. Box 43515‑1155, 43516‑66456 Tehran, Iran



Department of Chemical Engineering, University of Guilan, 41996‑13776 Rasht, Iran

2

Greek symbols α Absorption coefficient ϑ Frequency of vibration Subscripts h, k, l Miller coordinates

1 Introduction The increase in global population and the rapid development of industry lead to climate changes, reduced natural resources and increased industrial pollutants, all rendering environmental crisis the biggest concern of the current century. Increased population and industrial effluents rapidly augment the demand for clean water. Therefore, the disposal of residual wastewater in water resources poses threats to the sustainable development of human society [1], hence the absolute necessity of purifying and recycling wastewater for ecosystem revival. Chlorophenols constitute a specific group of priority toxic pollutants li