Catalysis Today 284 (2017) 129–136 Contents lists available at ScienceDirect Catalysis Today j our na l ho me page: www.elsevier.com/locate/cattod Peroxo group enhanced nanorutile as visible light active photocatalyst Tamás Gyulavári a,b , Zsolt Pap a,c,d,e , Gábor Kovács a,b,c,d , Lucian Baia c,d , Milica Todea d , Klára Hernádi a,b , Gábor Veréb a,f,∗ a Research Group of Environmental Chemistry, Institute of Chemistry, University of Szeged, H-6720, Szeged, Tisza Lajos krt. 103, Hungary b Department of Applied and Environmental Chemistry, University of Szeged, H-6720, Szeged, Rerrich tér 1, Hungary c Faculty of Physics, Babes-Bolyai University, RO-400084, Cluj-Napoca, M. Kogalniceanu 1, Romania d Institute for Interdisciplinary Research on Bio-Nano-Sciences, Babes-Bolyai University, RO-400271, Cluj-Napoca, Treboniu Laurian 42, Romania e Institute of Environmental Science and Technology, University of Szeged, H-6720, Szeged, Tisza Lajos krt. 103, Hungary f Department of Process Engineering, Faculty of Engineering, University of Szeged, H-6725, Szeged, Moszkvai krt. 9, Hungary a r t i c l e i n f o Article history: Received 15 July 2016 Received in revised form 29 September 2016 Accepted 6 November 2016 Available online 18 November 2016 Keywords: Titanium dioxide Rutile Peroxo group Phenol Visible light excitability a b s t r a c t Hydrogen peroxide was applied during the synthesis to enhance the visible light excitability of nanosized (<10 nm), pure rutile phase titanium dioxides synthesized by a facile, sol-gel method at low tempera- ture. Different amounts of hydrogen peroxide were used during the synthesis to form peroxo groups on the surface of TiO 2 -s. As-prepared photocatalysts were characterized by X-ray diffraction (XRD), dif- fuse reflectance spectroscopy (DRS), infrared spectroscopy (IR), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the catalysts were investigated by phenol, Rhodamine B dye and coumarin degradation under visible light irradiation. Evonik Aeroxide P25 TiO 2 and commercial rutile phase titanium dioxide were used as reference photocatalysts. First order derivative of DRS spectra showed enhanced visible light excitability in the case of Ti:H 2 O 2 = 1:2 ratio (applied during the synthe- sis). XPS measurements confirmed the formation of peroxo groups in this specific TiO 2 . Photocatalytic measurements pointed out that this TiO 2 had by far the best photocatalytic performance, exceeding the photocatalytic activity of Aeroxide P25 and commercial rutile as well. This activity gain was attributed to the presence of peroxo groups on the surface. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Heterogeneous photocatalysis is one of the most promising advanced oxidation process and it is extensively investigated since the discovery of water splitting using titanium dioxide (TiO 2 ) [1]. TiO 2 based photocatalysis have been widely studied for water treat- ment applications due to its ability to decompose various kinds of organic pollutants even toxic, chemically stable and persistent con- taminants like phenol [2–7], organic dyes [8,9], pesticides [8,10], pharmaceuticals [11,12], moreover, this method has high potential in disinfection [2,6,7,13–15] processes. It is imperative to develop visible light active photocatalysts for indoor applications (e.g. air- cleaning and self-cleaning surfaces) in order to utilize artificial light due to the negligible amount of UV photons under usual internal lighting conditions. Extending TiO 2 light absorption into the visible light region can also be beneficial for outdoor applications in case ∗ Corresponding author at: Research Group of Environmental Chemistry, Institute of Chemistry, University of Szeged, H-6720, Szeged, Tisza Lajos krt. 103, Hungary. E-mail address: verebg@mk.u-szeged.hu (G. Veréb). of natural solar irradiation (∼45% of the solar spectrum is in the visible range). There are many different approaches in the literature to pre- pare visible-light active TiO 2 -s, like doping with various elements (e.g. nitrogen, iron, iodine, silver, gold, sulfur) [4–7,9,16,17], sen- sitizing with dyes [18,19], deposition of noble metals [12,20] or by preparing composites [20,21]. The photocatalytic efficiency can be increased by enhancing the visible light absorption of TiO 2 via the adsorption of hydrogen peroxide on the surface thus form- ing yellow-colored Ti-peroxo species [22,23]. A relatively novel approach to enhance the visible light activity of TiO 2 is to anchor Ti-peroxo groups on the surface using hydrogen-peroxide (H 2 O 2 ) during the synthesis procedure, which increases the visible light absorption [18,24–27] thus amplifying the efficiency. Amorphous [25], anatase [18] or mixed phase [24,26,27] TiO 2 -s were inves- tigated, however forming peroxo groups on the surface of pure nanosized rutile in order to increase the visible light sensitiv- ity have not been reported to our best knowledge, even though rutile has generally higher visible light activity [28,29] than anatase phase. http://dx.doi.org/10.1016/j.cattod.2016.11.012 0920-5861/© 2016 Elsevier B.V. All rights reserved.