Supporting Information

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1 Supporting Information Enhanced Photocatalytic Activity of Titanium Dioxide: Modification with Graphene Oxide and Reduced Graphene Oxide Xuandong Li,* Meirong Kang, Xijiang Han, Jingyu Wang, and Ping Xu Department of Chemistry, Harbin Institute of Technology, Harbin 151, P. R. China (Received January 27, 214; CL-1463; Copyright The Chemical Society of Japan

2 Supporting Information Experimental Preparation of samples Synthesis of Graphene Oxide (GO) and Reduced graphene oxide (RGO). GO gel was prepared by the modified Hummers method [S1-S3]. For the preparation of RGO, 1 mg of graphite oxide was added to 1 ml deionized water under ultrasonic dissection for 1 h. Then, 2 ml of hydrazine hydrate was added into the suspension, and the system was heated at 1 for 6 h. After filteration, washing, and drying, RGO was obtained. Preparation of GO-TiO 2. The sulfuric acid titanium sulfate solution was prepared according to the method in reference [S4]. The nominal mass ratio of GO to TiO 2 was designed as.1,.5,.1,.15,.2 and 1., respectively. A certain amount of GO was added into 2 ml of.1 mol/l potassium hydroxide solution. The solution was ultrasonically treated for.5 h, and then added to the preheated titanium sulfate solution. The resulting solution was placed in a water bath understirring at 8 for 4 h, and then the solid products were hot filtered, washed and dried. Preparation of RGO-TiO 2. 1 mg GO-TiO 2 composite was dispersed in 1 ml deionized water with ultrasonic dissection for.5 h. Then 2 ml hydrazine hydrate was added into the suspension. The mixture was refluxed for 6h and then cooled to room temperature. The solid products were filtered, washed and dried. Characterization The FT-IR spectroscopy was measured on a Nicolet Avatar 36 FT-IR Spectrometric Analyzer with KBr pellets. The characteristics of the crystallite structure of the prepared samples were determined using an XRD-6 X-ray diffractometer (Shimadzu) with a CuK radiation source (λ = nm, 4. kv, 3. ma). Raman spectra were recorded using a DXR Smart Raman (Thermo Scientific) with a 78 nm laser. The exposure time was 5 seconds. The oxidation states of the element in the composites were characterized by X-ray photoelectron spectroscopy (XPS), by using a PHI 57 ESCA system (Physical Electronics) with

3 AlKα (25. W, ev) radiations as the excitation source. The thermogravimetric (TG) analysis was carried out on a Setsys Evolution TGA (Setaram) in the temperature range from room temperature to 8 with the heating rate of 1 /min under air flow. Morphology measurements were carried out on a 2 FEI (Quanta) scanning electron microscope (SEM) at 3 kv accelerating voltage, and the samples were sputter-coated with gold before analysis. Photodegradation 5 mg of sample was added to 5 ml of prepared 1 mg/l methyl orange solution. A 5 W halogen lamp (Institute of Electric Light Source, Beijing) was used as visible-light source. While reacting with dyes, a cutoff filter was settled to completely remove any radiation below 42 nm and to ensure illumination by visible-light. Before irradiation, the suspensions were stirred for 4 min in the dark to establish the adsorption-desorption equilibrium. The methyl orange solution was sampled every 15 min during the irradiation, with immediately centrifuging and conducting desorption by NaOH solution, finally collecting all of the clear liquid to record the dye absorption spectra. The changes in maximum absorption (1-A/A ), versus irradiation time (t) were obtained; these reflected the decrease in the dye concentration and could be used to calculate the degradation ratio. After two hours of photodegradation, samples were washed with distilled water for several times and dried again, which were used to repeat a new degradation process for testing the reuse performance of samples.

4 Figure S1. FT-IR spectra of graphite and GO. Figure S2. XRD patterns of GO, RGO, GO/RGO-TiO 2 composites prepared from mass ratio of GO/RGO:TiO 2 =.15.

5 (a) D 1 GO G Intensity ( a.u. ) RGO Graphite Raman Shift ( cm -1 ) 2 (b) D Intensity ( a.u. ) 1 GO/TiO 2 =.15 Graphite oxide G Raman Shift ( cm -1 ) 1 (C) RGO D Intensity ( a.u. ) RGO/TiO 2 =.15 G Raman Shift ( cm -1 ) Figure S3. Raman spectra of GO and RGO (a), GO-TiO 2 composites prepared from mass ratio of GO:TiO 2 =.15 (b) and RGO-TiO2 composites prepared from mass ratio of GO:TiO 2 =.15 (c).

6 3 25 (a) ev C-C Intensity ( cps ) ev -O-C=O ev C-OH Binding Energy ( ev ) 6 5 (b) ev C-C 4 Intensity ( cps ) ev -C-O-C ev C-OH ev -C-O-C ev -O-C=O Binding Energy ( ev ) (c) ev C-C Intensity(cps) ev -O-C=O ev C-OH ev -C-O-C Binding Energy(eV)

7 65 6 (d) ev C-C Intensity(cps) ev -C-O-C ev -O-C=O ev C-OH Binding Energy (ev) 4 35 (e) Ti Ⅳ 2P 3/2 3 Intensity ( cps ) 25 2 Ti Ⅳ 2P 1/ Binding Energy ( ev ) Figure S4. C1s XPS spectra of GO (a), GO-TiO 2 =.15 (b), RGO-TiO 2 =.15 (c), and GO-TiO 2 =.15 (7R) (d). Ti2P XPS spectra of GO-TiO 2 =.15 (e).

8 (a) TG ( % ) DTA ( uv ) Temperature ( ) (b) TG ( % ) DTA ( uv ) Temperature ( ) Figure S5. Thermogravimetric curves of GO-TiO 2 =.15 (a) and RGO-TiO 2 =.15 (b). The composite of GO-TiO 2 (=.15) has three obvious weight loss steps: (1) the moisture removal in the temperature range form 2 to 19 ; (2) decomposition of the polar groups of the GO in the second step form to 251.8, corresponding to the exothermic peak in the analysis of DTA at 233 ; (3) the combustion of carbon skeleton of GO at the third step from to 497, corresponding to the exothermic peak in DTA curve near 457. With further rising of temperature, the mass of sample remains constant, and the residue is pure TiO [S5] 2. It can be calculated by thermal analysis curves that the actual mass ratio of water, GO and TiO 2 is 1:7:12. Compared with GO-TiO 2, it is clear that RGO-TiO 2 has only one significant weight loss step from to 625.2, which is the combustion of carbon skeleton, corresponding to the exothermic peak in DTA curve at about 571.

9 Figure S6. Bar plot showing the adsorbing concentration fraction of MO after continuous stirring for 4 min in the dark over TiO 2, GO/TiO 2, and RGO/TiO 2 samples. Reference S1. W. S. Hummers, R. E. Offeman, J. Am. Chem. Soc., 1958, 8, S2. N. I. Kovtyukhova, P. J. Ollivier, B. R. Martin, T. E. Mallouk, S. A. Chizhik, E. V. Buzaneva, A. D. Gorchinskiy, Chem. Mater. 1999, 11, 771. S3. I. R. M. Kottegoda, N. H. Idris, L. Lu, J. Z. Wang, H. K. Liu, Electrochimica Acta 211, 56,5815. S4. Q Zhang, Y. Q. He, X. G. Chen, D. H. Hu, L. L. Li, T. Yi, Chin. Sci. Bull. 21, 55, 62. S5. G. D. Jiang, Z. F. Lin, C. Chen, L. H. Zhu, Q. Chang, N. Wang, W. Wei, H. Q. Tang. Carbon, 211, 49, 2693.