Edge-to-edge oriented self-assembly of ReS 2 nanoflakes

Transcription

1 Edge-to-edge oriented self-assembly of ReS 2 nanoflakes Qin Zhang,, Wenjie Wang,, Xin Kong, Rafael G. Mendes, Liwen Fang, Yinghui Xue, Yao Xiao, Mark H. Rümmeli,#,, Shengli Chen and Lei Fu*, College of Chemistry and Molecular Science, Wuhan University, Wuhan , P. R. China IFW Dresden, P.O. Box , Dresden, Germany # College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou, Nano Science and Technology, Soochow University, Suzhou , China Centre of Polymer and Carbon Materials, Polish Academy of Sciences, M. Curie-Sklodowskiej 34, Zabrze , Poland These authors contributed equally to this work. * To whom correspondence should be addressed: leifu@whu.edu.cn S1

2 1. Experiments and characterizations CVD growth of 3DGF: Nickel foams plates with small size (R = 12 mm) as substrates were put in a CVD chamber and heated to 1000 C. The heating and annealing process, used a gas mix of Ar (200 sccm) and H 2 (50 sccm), at ambient pressure. A small quantity of CH 4 (10 sccm) was brought into the quartz tube during the reaction, and simultaneously the H 2 was switched off. After that, the nickel foam was etched away with HNO 3 solution. The obtained 3DGF was washed with ultrapure water several times and then dried in a vacuum dryer at 70 C for 2h. Greater details can be found in ref. 1. Fabrication of ReS 2 NWs/3DGF composite: 0.1 mol/l ReS 2 precursor solution was prepared by dissolving NH 4 ReO 4 (0.268 g) in ultrapure water. The 3DGF was placed in NH 4 ReO 4 solution for 4 minutes and then dried at 70 C in vacuum oven for 2 h. After transfer into the CVD chamber, the furnace was heated up to 450 C within 15 minutes with argon (5 sccm) as the carrier gas. Once the temperature was stable, the composite was annealed at 450 C for 20 min with a mix of Ar (5 sccm) and H 2 S (1 sccm). The system cooled down naturally after the reaction. Lithium intercalation: The lithium intercalation of ReS 2 NWs/3DGF was performed in a coin cell using the Li foil as the anode and 1 M LiPF 6 as the electrolyte, which was dissolved in a mixture of ethyl carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 1:1. The lithium intercalation was operated using a galvanostatic discharge at current currents of 200 ma/g. During the discharge process, the ReS 2 nanowalls transformed to nanoscrolls (NSs), the lithium-intercalated ReS 2 NSs/3DGF was subsequently washed by dimethyl carbonate (DMC) and ethanol repeatedly to remove the residual electrolyte. Finally, the as-obtained ReS 2 NSs/3DGF composite was dried in a vacuum dryer at 80 C for 1 h. Characterization: Raman spectra were collected with a laser micro-raman spectrometer (Renishaw in Via, Renishaw, 532 nm excitation wavelength). Scanning electron microscopy (SEM) images were obtained from a ZEISS Merlin Compact SEM with energy dispersive X-ray spectroscopy (EDX) - INCAPentalFETx3 Oxford EDX. The X-ray photoelectron spectroscopy (XPS) measurement collected with a Thermo Scientific, ESCALAB 250Xi. The measuring spot size was 500 µm and the binding energies were calibrated by referencing the C 1s peak (284.8 ev). X-ray diffraction (XRD) measurement was performed with Rigaku MiniFlex600 using Cu-Ka radiation over the range of 2θ = The transmission electron microscopy (TEM) images were obtained by an aberration-corrected high-resolution TEM system (Model AC-HRTEM, FEI Titan), in which S2

3 the operating voltage was 80 kv. Density functional theory (DFT) calculations: All of the calculations were carried out by the unrestricted spin-polarized periodic DFT implemented in DMol 3 package 2, on Materials Studio program of Bio Accelrys. A core treatment was adopted as an all electron relativistic method to conduct metal relativistic effect, whereas the exchange-correlation functional were parameterized by the Perdew Burke Ernzerhof (PBE) within the generalized gradient approximation (GGA). Double numerical plus polarization function basis sets were adopted in the calculation. For all calculations, the geometry convergence tolerance for energy change was ev, while the force and displacement were smaller than ev/å and Å,respectively. To achieve accurate electronic convergence, self-consistent-field (SCF) procedures were performed with a convergence criterion of ev on the total energy. When setting samples, the periodic supercell of 1 1 ReS 2 without cutoff was used to simulate the original total energy and the k-points was In addition, a model consisting of 10 1 ReS 2 corresponding to the [010] direction was sampled by k-points. A vacuum region of 20 Å was used to separate each layer and images were in the direction parallel to the plane. For comparison, a supercell of 1 10 ReS 2 was used as the model of [100] direction and its k-points is were prepared. For either module, the distance between two sheets was set as 9.2 Å. S3

4 Figure S1. (a) Images of 3DGF, precursor coated 3DGF and ReS 2 nanowalls. (b) Photograph showing the flexibility of ReS 2 nanoscrolls. S4

5 Figure S2. SEM images of nanoscrolls with various magnifications. S5

6 Figure S3. TEM micrographs of ReS 2 nanowalls. S6

7 Figure S4. (a) XRD patterns of ReS 2 NSs and ReS 2 NWs on 3DGF. (b) Raman spectra of ReS 2 NWs and ReS 2 NSs. (c d) XPS analysis of ReS 2 NSs on 3DGF. S7

8 Figure S5. (a b) HR-TEM images of a cross section. The red line may follow the contour of a rolling sheet. The red arrow depicts a piece of the 2D ReS 2 nanoflake sticking out that did not roll. (c d) HR-TEM images of the individual nanoscroll with a large opening. The red lines follow a possible rolling direction. S8

9 Figure S6. HR-TEM image and EDX measurement of ReS 2 nanoscrolls. EDX shows a composition of atom% Re and atom% S. S9

10 Figure S7. HR-TEM micrograph of ReS 2 nanoscrolls. The fracture along the nanoscroll can be considered as an attachment or anchor point, and the fast Fourier transform (FFT) images indicate the same orientation for the two regions (yellow and red squares). S10

11 Figure S8. Simulation and calculations of binding energies between different facets in ReS 2. The binding energy can be represented as: E [xyz] =E [xyz] E Total Since the supercell of 1 1 ReS 2 without cutoff consisted of 12 atoms, E Total can be calculated as a tenfold value of the 1 1 supercell (E 0 ), for the purpose of matching with the 120 atoms in module of [100] and [010] directions. From the calculations, E 0 was Ha (1 Ha = 27.2 ev). E [010] and E [100] were and , respectively. As a result, E [010] is larger than that of E [100], and as such is the dominant facet. S11

12 Figure S9. SEM images of the ReS 2 NSs controlled via different voltages and HR-TEM images with corresponding distributions of the nanoscroll diameters. When the discharge voltage is 3.0 V, the average diameter is about 26 nm and the average aspect ratio is approximately 20:1. When discharging at 2.2 V, the average diameter is 22 nm and the average aspect ratio is over 45:1. With decreasing voltage, the average diameter of the nanoscrolls is 27 nm and the aspect ratio is greater than 50:1. S12

13 Figure S10. SEM images of several samples under lower voltages. The nanoscroll structures are destroyed or even disappear. References 1. Zhang, Q.; Tan, S.; Mendes, R. G.; Sun, Z.; Chen, Y.; Kong, X.; Xue, Y.; Rummeli, M. H.; Wu, X.; Chen, S.; Fu, L. Adv. Mater. 2016, 28, Delley, B. J Chem. Phys. 2000, 113, S13