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 130022, P. R. China *E-mail: zjl@ciac.ac.cn Tel: 86 0431 85262346 University of Chinese Academy of Sciences, Beijing 100049, P. R. China College of Life Science, Shenzhen University, Shenzhen 518060, P. R. China S1
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 = 371.14), 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
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 = 1.5405 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
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
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
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
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
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