Template-free synthesis of carbon doped TiO2 mesoporous microplates for enhanced visible light photodegradation
Juming Liu† • Lu Han† • Huiyan Ma • Hao Tian • Jucai Yang • Qiancheng Zhang* • Benjamin J Seligmann • Shaobin Wang • Jian Liu*
Juming Liu • Lu Han • Huiyan Ma • Qiancheng Zhang
Key Lab of Industrial Catalysis of the Inner Mongolia Autonomous Region, Inner Mongolia University of Technology, Hohhot 010051, China
Qiancheng Zhang:
Juming Liu • Jucai Yang
School of Energy and Power Engineering, Inner Mongolia University of Technology, Hohhot, 010051, China
Hao Tian • Benjamin J Seligmann • Shaobin Wang • Jian Liu
Department of Chemical Engineering, Curtin University, Perth, WA 6845, Australia
E-mail:
† These authors contributed equally to this work.
1. Experimental
1. 1 Sample preparation
1.1.1 Preparation of reduced sample
The reduced sample was prepared by a mild oxidation process. In a typical experiment, 0.5 g of the as-prepared carbon-doped TiO2 microplates (original sample) was put into a crucible. Then, the crucible was placed in a furnace. The temperature was gradually increased to 400 ºC with a heating rate of 10 ºC/min and kept at this temperature for 12 h in air. The final product (reduced sample) was allowed to cool to room temperature naturally.
1.1.2 Preparation of regenerated sample
The regenerated sample was prepared by an impregnation method. Typically, 0.3 g of the as-prepared reduced sample and 5mL glacial acetic acid were mixed in a crucible. The crucible was placed in a tube furnace. The subsequent preparation process was carried out in a pure nitrogen atmosphere (N2, 100 mL/min). Firstly, the temperature was gradually increased to 130 ºC (10 ºC/min) and kept at this temperature for 40 min. At this stage, acetic acid reacted with TiO2 to form the bidentate chelating structure. Then the temperature was increased from 130 ºC to 200 ºC (10 ºC/min) and kept for 2 h to remove the redundant acetic acid. The final product (regenerated sample) was allowed to cool to room temperature naturally.
1.2 Sample characterization
X-Ray diffraction (XRD) pattern was collected on a PANalytical Empyrean X-ray diffractometer with Cu Kα radiation. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were performed with an FEI Tecnai F20 transmission electron microscope. Scanning electron microscopy (SEM) investigation was carried out on a field emission-scanning electron microscope (FESEM, Hitachi S-4800), and the energy-dispersive spectroscopy (EDS) was observed using Bruker QUANTAX 200 detector. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy measurements were carried out using a Perkin Elmer Frontier FTIR spectrometer with an attenuated total reflection (ATR) accessory. X-ray photoelectron spectroscopy (XPS) was accomplished using THERMON ESCALAB 250 with monochromatic Al Kα source to identify the surface chemical constituents. Ultraviolet visible diffuse reflectance spectra (UV-Vis DRS) was recorded in the range of 300-800 nm using a UV-Vis spectrometer (UV-3600, Shimadzu) equipped with an integrating sphere accessory.
1.3 Photocatalytic degradation experiment
The photocatalytic activities of the samples were evaluated using phenol degradation in an aqueous solution under visible light irradiation. The visible light was provided by a visible light-emitting diode (Vis-LED, 450 nm) with the power of 20 W. The Vis-LED was equipped with 420 nm cutoff glass filter to ensure the visible wavelength components (λ≥420 nm), as shown in Fig. S8.
In a typical experiment, 0.1 g of sample was added to 30 mL of 20 mg/L phenol solution in a 50 mL quartz beaker. Prior to irradiation, the suspensions were magnetically stirred for 1 h to achieve adsorption-desorption equilibrium for phenol. Thereafter, the suspensions were illuminated with the Vis-LED equipped with 420 nm cutoff glass filter. During illumination over a 3 h period, a few milliliters of solution together with the solid catalyst was taken out every 30 min to determine the concentration of the remaining phenol using UV-Vis spectrophotometer by measuring of absorbance at 270 nm. The solution was separated from the catalyst through syringe filtration (pore size 0.22 μm). The concentration of phenol was obtained according to the linear relation between the absorbance and the concentration of the phenol solution.
1.4 Filtration experiment
The separation efficiency of the sample was evaluated using a filtration experiment at ambient temperature and pressure, in which Degussa P25 nanoparticles was used as a reference sample. Typically, 0.1 g sample was added to 30 mL of distilled water in a 50 mL beaker with stirring for 30 min to ensure complete mixing. Then the filtration experiment was performed with traditional method, draining this suspension turbid liquid through filter paper at ambient temperature and pressure. The change of filtrated volume with time was investigated. The vertical axis represents filtrated volume, while the horizontal axis represents filtration time.
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Fig. S1 Photographs of the formation process of white fluffy structure precursor
Fig. S2 SEM images ofthe white precursor (a) and carbon-doped TiO2 microplates (b) at the scale of 100 μm
Fig. S3 XRD patterns of the white precursor and carbon-doped TiO2 microplates
Fig. S4 Nitrogen adsorption-desorption isotherm (left) and pore size distribution (right) of the carbon-doped TiO2 microplates
Fig. S5 Energy-dispersive X-ray spectroscopy (EDS) of the carbon-doped TiO2 microplates
Fig. S6 Binding mode of bidentate chelating, bidentate bridging and monodentate binding
Generally, the band separation is 60-100 cm-1 for bidentate chelating, 150-180 cm-1 for bidentate bridging, and 350-500 cm-1 for monodentate binding [1], as shown in Fig. S6.
Fig. S7 XRD patterns of the original sample and reduced sample
Fig. S8 The spectra of Vis-LED equipped with 420 nm cutoff glass filter
Fig. S9 ATR-FTIR spectra (a) and photocatalytic degradation rate (b) of original sample, reduced sample and regenerated sample
References
1. Qu Q, Geng H, Peng R, et al (2010) Chemically binding carboxylic acids onto TiO2 nanoparticles with adjustable coverage by solvothermal strategy. Langmuir 26:9539-9546
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