Photocatalytic evaluation of RGO/TiO 2 NWs/Pd-Ag nanocomposite as an improved catalyst for efficient dye degradation Hossein Khojasteh, Masoud Salavati-Niasari * , Fatemeh Sadat Sangsefidi Institute of Nano Science and NanoTechnology, University of Kashan, Kashan, P. O. Box 87317e51167, Islamic Republic of Iran article info Article history: Received 14 December 2017 Received in revised form 8 February 2018 Accepted 28 February 2018 Keywords: RGO Ceramic Palladium TiO 2 nanowires Nanostructures Dye degradation abstract In this work RGO/TiO 2 NWs/Pd-Ag nanocomposite was prepared by using a combination of hydrothermal and photo-deposition methods. The properties of all prepared products were evaluated by using SEM, XRD, DRS, FT-IR, EDS, BET, TEM, TGA and ICP-OES analysis. Nanodimension structure of all samples was confirmed by TEM and SEM results. The calculated band gap values which were obtained by using DRS technique, suggested that Gr/TiO 2 NWs/Pd-Ag nanocomposites have a semiconductor behavior with a direct band-gap value of 2.95 eV. The amount of loaded graphene in the nanocomposite was evaluated by using TGA analysis. The degradation of rhodamine B and methylene blue by TiO 2 -NWs and RGO/ TiO 2 NWs/Pd-Ag nanocomposites were compared under UV light irradiation in similar conditions. The observations confirmed that the RGO/TiO 2 NWs/Pd-Ag nanocomposite have high photocatalytic perfor- mance toward both of pollutants owning to the much higher available surface area of TiO 2 nanowires, the unique synergic effect of Pd and Ag species and high electric transport property of the graphene structure. The product synthesis procedure has valuable advantages like high surface area photocatalyst, facile photodeposition of silver and palladium on the TiO 2 surface, and simple conversion of graphene oxide (GO) to reduced graphene oxide (RGO) during the hydrothermal process without using strong reducing agents, which can be a promising route for preparing various types of high active carbon based nanocomposite photocatalyst. © 2018 Elsevier B.V. All rights reserved. 1. Introduction As we know, dissemination of heavy metals, pesticides, organic wastes and dyes in the environment is an significant issue and have provided the serious motivation to start deep research related to the area of environmental protection [1]. As a solution, semi- conductor photo catalysis using solar energy for photodegradation of water pollutants is taken into consideration [2e4]. Photocatalysis of water pollutants is one of the cleanest and greenest ways of water purifying, which has great potential in solving the clean water problem. To act as spontaneous photocatalysis, three prop- erty should be existed for a semiconductor: (1) it must be stable against photo corrosion, during photo catalysis, (2) it should be reusable with no reduction in photocatalytic performance and (3) it should have high degradation or photocatalytic power. Depend on the material and its mixture content, semi- conductors has a variety of band gaps and can conduct different amounts of electricity. Most of the semiconductors like TiO 2 , CdSe, WO 3 , Bi 2 WO 6 , Bi 2 O 3 , NiTiO 3 , ZnO and CDs, etc. has been reported to have photocatalytic activity for various applications such as degradation of dyes and other organic water splitting, pollutants, solar cells etc. [5e10]. But among the various semiconductors, those which have some benefits such as compatibility with other mate- rials, inexpensive, performance stability, chemical inertness, non- toxicity, strong photo-oxidizing property and environmentally safe are desirable [6, 11 , 12]. As an example of known semiconductor, titanium dioxide as a heterogeneous photocatalyst has been widely studied during the past decades and has emerged as an appropriate material for degradation of organic pollutants to produce less toxic substances [13e15]. After absorbing of the light, the electrons in the valence bond of the titania excite to conduction band to product photoexcited electrons and holes [16]. But the mistake is that the photogenerated electrical charges and holes are unstable and recombination of e  and h þ pairs occurs immediately. But as we know, when the recombination is prevented by preventing the recombination of electron hole, the photocatalytic activity will be more effective [17 , 18]. Some attempts to solve this problem is based * Corresponding author. E-mail address: salavati@kashanu.ac.ir (M. Salavati-Niasari). Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom https://doi.org/10.1016/j.jallcom.2018.02.345 0925-8388/© 2018 Elsevier B.V. All rights reserved. Journal of Alloys and Compounds 746 (2018) 611e618