Applied Catalysis B: Environmental 218 (2017) 758–769 Contents lists available at ScienceDirect Applied Catalysis B: Environmental j ourna l h omepa ge: www.elsevier.com/locate/apcatb Research paper One-step hydrothermal synthesis of Bi-TiO 2 nanotube/graphene composites: An efficient photocatalyst for spectacular degradation of organic pollutants under visible light irradiation Umair Alam a , M. Fleisch b , Imme Kretschmer b , Detlef Bahnemann b,c , M. Muneer a,∗ a Department of Chemistry, Aligarh Muslim University, Aligarh, 202002, India b Photocatalysis and Nanotechnology, Institut fuer Technische Chemie, Gottfried Wilhelm Leibniz Universitaet Hannover, Callinstrasse 3, D-30167 Hannover, Germany c Photoactive nanocomposite materials, Saint-Petersburg, State University, Ulyanovskaya Str, Peterhof, Saint-Petersburg, 198504, Russia a r t i c l e i n f o Article history: Received 12 February 2017 Received in revised form 1 June 2017 Accepted 5 June 2017 Available online 7 June 2017 Keywords: Bi-TiO2NT/graphene Photocatalytic activity Methylene blue Dinoseb a b s t r a c t In the present study, we have adopted a simple one-pot alkaline hydrothermal route to synthesize Bi- doped TiO 2 NT/graphene composites by using different wt% of Bi with an aim to achieve the excellent photocatalytic activity under visible light source. The nature of GO is changed to deoxygenated graphene with simultaneous embedding of Bi into TiO 2 nanotube (TNT), during hydrothermal process. XRD and FTIR analysis confirm the successful conversion of GO to deoxygenated graphene. EPR analysis reveals the co- existence of Ti 3+ ion with oxygen vacancy, which is created by the Bi doping. The photocatalytic activity of the prepared samples is measured by the degradation of aqueous suspensions of methylene blue (MB) and Dinoseb (phenolic herbicide), under visible-light irradiation. The prepared TiO 2 NT/graphene composite with 2-wt% bismuth (2-BTNTG) has shown the improved photocatalytic activity as compared to their counterparts. The improved photocatalytic activity is associated to the synergistic effect of graphene and Bi-TNT, which facilitate the interfacial charge transfer and enhances the efficiency of light harvesting in the visible region. Moreover, the underlying mechanism involving photocatalytic degradation of organic pollutants over 2-BTNTG is explored by using trapping experiments, suggesting that the . OH radicals solely contributed to degradation. © 2017 Published by Elsevier B.V. 1. Introduction Recently, a wide variety of organic pollutants comprising of her- bicide derivatives, textile dyes, and phenolic compound derivatives responsible for environmental and water pollution are reported [1–3]. Among these, herbicide derivatives and textiles dyes are most difficult to decompose owing to their chemical and biolog- ical stability [4–7]. These are ranked as the most carcinogenic and high toxic pollutants, manifesting the major threat to human and aquatic life [8–10]. Enormous research efforts are devoted to reduce these pollutants in water by biological and physical techniques but the majority of these are cumbersome, expensive and less effective [11–13]. In this regard, semiconductor photocatalysis is emerging as an advanced and green technology for the degradation ∗ Corresponding author. E-mail addresses: readermuneer@gmail.com, m.muneer.ch@amu.ac.in (M. Muneer). of these pollutants due to its environmental benignancy, stabil- ity, and safety [14,15]. Significantly, TiO 2 has proven to be one of the most widely accepted and benchmark photocatalytic material owing to its strong oxidizing power, intoxicate high photostabil- ity, and low cost [16–19]. One-dimensional (1D) nanostructures of TiO 2 , such as nanorods [20], nanowires [21], and nanotubes [22,23], have gained interest owing to their quantum confinement and high surface area. TiO 2 nanotubes are widely applied in the photocat- alytic degradation of organic pollutants because of their structure dependent enhanced photocatalytic properties [23–25]. However, the major drawbacks that confine its use to larger scale are its wide bandgap and quick recombination of charge carriers [25–27]. Sev- eral strategies are adopted to modify TiO 2 such as extending its spectral response to the visible region and prolonging the life span of photoinduced electron-hole pairs. The strategies involve, doping with metals and non-metals [27–29], noble metals deposition [30] and heterostructure construction with narrow bandgap semicon- ductors and carbonaceous materials [31–35]. The carbon-titania nanocomposites by linking titania with carbonaceous materials http://dx.doi.org/10.1016/j.apcatb.2017.06.016 0926-3373/© 2017 Published by Elsevier B.V.