Supporting Information

Transcription

1 Supporting Information Novel Strategy for Facile Synthesis of C-Shaped CeO 2 Nanotubes with Enhanced Catalytic Properties Nan Lv,, Jilin Zhang,,* Guangming Li,, Xun Wang,, and Jiazuan Ni, State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Changchun , P. R. China * zjl@ciac.ac.cn Tel: University of Chinese Academy of Sciences, Beijing , P. R. China College of Life Science, Shenzhen University, Shenzhen , P. R. China S1

2 Experimental section Materials and methods Dimethylformamide (DMF), nitric acid (HNO 3, 65%) and ammonium hydroxide (NH 3 H 2 O, 28wt%, HPLC grade) were obtained from Beijing Chemical Regent Co., Ltd. (Beijing, China). Rare earth nitrates (Ce(NO 3 ) 3 6H 2 O, La(NO 3 ) 3 6H 2 O, Nd(NO 3 ) 3 6H 2 O, Y(NO 3 ) 3 6H 2 O) were supplied by Sinopharm Chemical Reagents Company (China). Polyvinyl pyrrolidone (PVP, MW=90000), p-nitrophenol (p-np, 99.5%, MW=139.11) and p-nitrophenyl disodium orthophosphate (C 6 H 4 NO 6 PNa 2 6H 2 O, p-npp, 98%, MW = ), were purchased from Aladdin (Shanghai, China). Polyacrylonitrile (PAN, MW=85000) was supplied by Shanghai Macklin Biochemical Co., Ltd. (Shanghai, China). All the chemical agents were used without further purification. The fabrication of the [PVP/Ce(NO 3 ) 3 ]//PVP Janus fibers and [PAN/Ce(NO 3 ) 3 ]//PAN Janus fibers: The spinning solution I for fabricating PVP/Ce(NO 3 ) 3 nanofibers in [PVP/Ce(NO 3 ) 3 ]//PVP Janus fibers was achieved as below: 1.0 g of Ce(NO 3 ) 3 6H 2 O was dissolved in 30 g of DMF and then 4 g of PVP was added into the solution with magnetic stirring for 6 h. The spinning solution II for PVP nanofibers in [PVP/Ce(NO 3 ) 3 ]//PVP Janus fibers was synthesized as follows: 1 g of PVP was added into 7 g of DMF with magnetic stirring for 6 h. The spinning solution I for fabricating [PAN/Ce(NO 3 ) 3 ] nanofibers in [PAN/Ce(NO 3 ) 3 ]//PAN Janus fibers was obtained as follows: 1 g of Ce(NO 3 ) 3 6H 2 O was dissolved in 10 g of DMF and then 1.1 g of PAN was added into the solution with magnetic stirring for 8 h. The spinning solution II for PAN nanofibers in [PAN/Ce(NO 3 ) 3 ]//PAN Janus fibers was synthesized as below: 0.5 g of PAN was added into 4 g of DMF with magnetic stirring for 8 h. The electrospinning technique using the specially designed parallel spinneret was used to fabricate the [PAN/Ce(NO 3 ) 3 ]//PAN Janus fibers and [PVP/Ce(NO 3 ) 3 ]//PVP Janus fibers as illustrated in Figure 1f. A sheet of aluminum foil was used as a collector and S2

3 placed about 20 cm away from the top of the spinneret. A positive direct current (DC) voltage of 25 kv was set between the spinneret and the collector. The as-spun product was heated to 700 C at a heating rate of ca. 0.7 C min -1 and the reaction was then maintained at 700 C for 2 h in air in a furnace. Finally, CeO 2 nanotubes were obtained. Preparation of CeO 2 nanofibers: In a typical synthesis, 1.0 g of Ce(NO 3 ) 3 6H 2 O was dissolved in 15 g of DMF and then 2 g of PVP was added into the solution with magnetic stirring for 6 h. A sheet of aluminum foil was used as a collector and placed about 20 cm away from the top of the spinneret. A positive direct current (DC) voltage of 22 kv was set between the spinneret and the collector. The as-spun product was heated to 700 C at a heating rate of ca. 5 C min -1 and the reaction was then maintained at 700 C for 2 h in air in a furnace to form CeO 2 nanofibers. Characterization. A field emission scanning electron microscope (FESEM, S4800, Hitachi) equipped with an energy-dispersive X-ray spectrum (EDX, JEOLJXA-840) was applied to determine morphologies and compositions of the as-prepared samples. Transmission electron microscopy (TEM), high-resolution TEM (HRTEM) images and energy-dispersive X-ray analysis (EDXA) were taken with a FEI Tecnai G 2 S-Twin transmission electron microscope operated at 200 kv. Powder X-ray diffraction (XRD) patterns were collected on a Bruker D8 Focus X-ray diffractometer using Cu Kα radiation (λ = Å). Fourier-transform infrared spectroscopy (FTIR) analysis was carried out on a Perkin-Elmer 580B infrared spectrophotometer using a standard KBr pellet technique. Nitrogen adsorption isotherms were measured at a liquid nitrogen temperature (77 K) with a Micromeritcs ASAP 2010 M apparatus. The specific surface area was determined by the Brunauer Emmett Teller (BET) method. TGA and DSC were carried out on a Netzsch Thermoanalyzer STA 409 instrument in an atmospheric environment with a heating rate of 0.7 C min 1 from room temperature to 500 C. UV-vis absorption spectra and the adsorption curves were obtained using a Shimadzu UV-1750 UV-vis spectrophotometer. S3

4 Figure S1. XRD patterns of [PAN/Ce(NO 3 ) 3 ]//PVP Janus fibers and C-shaped CeO 2 nanotubes. Figure S2. SEM images, N 2 adsorption-desorption isotherms and pore size distributions of C- shaped CeO 2 nanotubes (a, d, g), CeO 2 nanotubes (b, e, h) and CeO 2 nanofibers (c, f, i). S4

5 Figure S3. TG-DSC curve of [PAN/Ce(NO 3 ) 3 ]//PVP Janus fibers calcined in air at a heating rate of ca. 0.7 C min -1. Figure S4. SEM images of Ce(NO 3 ) 3 /PAN/PVP composite nanofibers after calcination at 700 C for 2 h at a heating rate of ca. 0.7 C min -1. S5

6 Figure S5. SEM images of [PAN/Ce(NO 3 ) 3 ]//PAN Janus fibers and [PVP/Ce(NO 3 ) 3 ]//PVP Janus fibers before (a, c) and after calcination (b, d) at 700 C for 2 h at a heating rate of ca. 0.7 C min -1. Figure S6. SEM images of [PAN/Ce(NO 3 ) 3 ]//PVP Janus fibers that contain different content of Ce(NO 3 ) 3 after calcination at 700 C for 2 h at a heating rate of ca. 0.7 C min -1. The mass ratio of the PAN: Ce(NO 3 ) 3 : PVP is 2:1:2 (a) and 2:3:2 (b). S6

7 Figure S7. Successive UV-vis spectra of the reaction mixtures in Figure 5b and Figure 5c recorded with the reaction time. a) blank test, b) CeO 2 nanofibers, c) CeO 2 nanotubes, d) C-shaped CeO 2 nanotubes. All the samples were diluted 10 times with NH 3 H 2 O (1%) before the UV-vis detection. Figure S8. Standard curves for (a) p-npp at wavelength 311 nm and (b) p-np at wavelength 400 nm. S7

8 Figure S9. Standard curve (a) for the UV-vis adsorption of P by the Phosphorus Molybdenum Blue method at 890 nm. UV-vis detection (b) of phosphate in the final supernatants of the mixtures in the experiment of Figure 5 by the Phosphorus Molybdenum Blue method. 0.4 ml supernatant was diluted to 25 ml for the UV-vis detection. The inset table shows the calculated amounts of phosphate (calculated in P, MW = 31) according to the standard curve in Figure S9a. Figure S10. The structure illustration of CeO 2 nanofibers, CeO 2 nanotubes and C-shaped CeO 2 nanotubes. S indicates the exposed surface. S8