Electronic Supplementary Information: A novel ZnO

Supplementary Material (ESI) for Chemical Communications This journal is (c) The Royal Society of Chemistry 2010
Electronic Supplementary Information:
A novel ZnO nanostructure: rhombus-shaped ZnO nanorod array
Feng Xu,a,b Yinong Lu,*a Litao Sun*b and Linjie Zhi*c
a State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, Nanjing 210009, China. E-mail: [email protected]; Fax: +86-25-83172118; Tel: +86-25-83172119
b Key Laboratory of MEMS of Ministry of Education, Southeast University, Nanjing 210096, China. E-mail: [email protected]; Fax: +86-25-83792939; Tel: +86-25-83792632 ext. 8813
c National Center for Nanoscience and Technolog, Beijing 100190,. China. E-mail: [email protected]
Experimental section
All chemicals purchased from Shanghai Chemical Reagents Co. Ltd. were of analytical reagent grade and used as received without further purification. In a typical electrodeposition procedure, the rhombus-shaped Zn(OH)F nanorod arrays were directly electrodeposited onto tin doped indium oxide (ITO, 10–15Ω/□) glass substrate with a pre-prepared seed layer of ZnO from an aqueous electrolyte bath containing Zn(NO3)2 and NaF with starting solution pH of 5.0±0.1. The solution temperature was strictly controlled at between 55 and 60 ºC. The electrodeposition was potentiostatically performed on a CHI660D potentiostat (Shanghai Chenhua Instrument Co., China), using a classical three-electrode configuration, in which a ZnO seedlayer/ITO substrate, a graphite rod and a saturated calomel electrode (SCE) served as the working electrode (cathode), the counter electrode, and the reference electrode, respectively. The SCE was immersed in saturated KCl solution that was connected to the electrolyte bath with a Luggin-Haber capillary. The space width between the working electrode and the counter electrode was about 5 cm. At the end of growth period, the ITO substrate covered with Zn(OH)F nanorod arrays was removed from the solution and immediately rinsed in flowing deionized water to eliminate any residual impurities from the surface. Finally, the as-obtained Zn(OH)F sample was pyrolyzed at 450 ºC for 2 h to yield unique rhombus-shaped ZnO nanorod arrays.
A scanning electron microscope (SEM, JSM–5900, JEOL Ltd., Japan) were employed for the observation of the surface morphology of the obtained samples, operated at an acceleration voltage of 20 kV. Prior to the observation, the samples were sputter-coated with Au under the vacuum condition for electric conduction. The crystallographic characterization was investigated by an X-ray diffractometer (XRD, ARL XTRA, Themo Electron Co., USA) with Cu KαB radiation at a scan speed of 5Pº/min in the 2θ range from 20ºP to 65Pº P. The tube voltage and the tube current were 45 kV and 35 mA, respectively. Transmission electron microscopic (TEM) images were taken with a high-resolution transmission electron microscope (HRTEM, JEM-2010 operated at 200 kV, JEOL Ltd., Tokyo, Japan) having a point-to-point resolution of 0.19 nm and a line resolution of 0.14 nm. The HRTEM was equipped with a Gatan multiscan charge-coupled device (CCD) camera system (Model 794, Gatan Inc., Pleasanton, CA, USA) and an Erlangsheng ES 500W CCD camera (Model 782，Gatan Inc., Pleasanton, CA, USA) to record the HRTEM images and SAED patterns. The room-temperature photoluminescence (PL) spectra were measured using a spectrophotometer (Jobin Yvon Fluorolog3-221) with a Xe lamp (450 W) as excitation source at an excitation wavelength of 325 nm. Hydrogen adsorption and desorptionexperiments were perfomed using a gas reaction controller at room temperature. The rhombus-shaped ZnO nanorods (300 mg) scraped from the substrate were employed and the hydrogen uptake process was performed under the pressure of 5.05 MPa (the high-point pressure of the apparatus). Before the measurement, the samples were heated at 300 ºC for 1 h to eliminate such impurities as water and oxygen. Then, highly purified hydrogen (99.99%) was introduced into the measurement system and hydrogen storage began.
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Supplementary Material (ESI) for Chemical Communications This journal is (c) The Royal Society of Chemistry 2010
Figure S1. SEM image of ZnO seedlayer prepared by the spin-coating method.
Figure S2. Experimental set for the electrochemical deposition of rhombus-shaped Zn(OH)F nanorod arrays.
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Supplementary Material (ESI) for Chemical Communications This journal is (c) The Royal Society of Chemistry 2010
Figure S3. Cross-section SEM micrograph of the rhombus-shaped nanorod arrays.
Figure S4. Plan-view SEM image of rhombus-shaped crystals electrodeposited on naked ITO substrates without a pre-prepared ZnO seedlayer.
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Supplementary Material (ESI) for Chemical Communications This journal is (c) The Royal Society of Chemistry 2010
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Figure S5. High resolution TEM image on the middle of an individual rhombus-shaped ZnO nanorod, showing its polycrystalline structure.
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Figure S6. High-resolution TEM image on the rhombic end plane of a Zn(OH)F NR, showing its polycrystalline structure.
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Supplementary Material (ESI) for Chemical Communications This journal is (c) The Royal Society of Chemistry 2010

Figure S7. Schematic diagram of the ZnO wurtzite structure, and the possible sites (AB or BC) on which the hydrogen can be incorporated. BC indicates the bond-center sites, and AB indicates the antibonding sites.
UV emission
Visible emission

Intensity (a. u.)

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450

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Wavelength (nm)

Figure S8. Room-temperature photoluminescence spectrum of the polycrystalline rhombus-shaped ZnO nanorod arrays after a hydrogen storage experiment.

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