Phytic Acid-Assisted Formation of Hierarchical Porous CoP/C Nanoboxes for Enhanced Lithium Storage and Hydrogen Generation

Transcription

1 Phytic Acid-Assisted Formation of Hierarchical Porous CoP/C Nanoboxes for Enhanced Lithium Storage and Hydrogen Generation Xuxu Wang, ab Zhaolin Na, a Dongming Yin, a Chunli Wang, ab Yaoming Wu, a Gang Huang, *c Limin Wang *ab a State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, CAS, Changchun, , China. Fax: ; Tel: b University of Science and Technology of China, Hefei , China c WPI Advanced Institute for Materials Research, Tohoku University, Sendai , Japan *Corresponding author: Limin Wang, lmwang@ciac.ac.cn, Tel: , Fax: Gang Huang, huang.gang.e5@tohoku.ac.jp, Tel: , Fax:

2 Figure S1. SEM images and particle size distribution of ZIF-67 nanocubes. Figure S2. (a) XRD patterns of ZIF-67 and Co-PA-N (N=1-4); (b) FT-IR spectra of ZIF-67 and Co-PA-N (N=1-4).

3 a b c 2 μm 1 μm d 1 μm 1 μm Figure S3. SEM image of Co-PA-N (N=1-4): (a) Co-PA-1; (b) Co-PA-2; (c) Co-PA-3 and (d) Co-PA-4. a b 500 nm 200 nm Figure S4. TEM images of Co-PA-4.

4 Figure S5. XRD patterns of CoP-NB and CoP nanoparticle. Figure S6. XRD patterns of CoP-NB-2. Figure S7. XRD pattern of Co-PA-3 after heat-treated under 550 o C.

5 Figure S8. SEM images of Co-PA-3 after heat-treated under 750 o C. D G Intensity (a.u.) I D /I G =0.96 (a) Weight loss (%) % Wavennumber (cm -1 ) Figure S9. Raman spectrum of CoP-NB Temperature ( o C) (b) Intensity (a.u.) Co 2 P 2 O 7 :PDF# Theta (degree) Figure S10. (a) Thermogravimetric analysis (TG) of CoP-NB under air with a ramp rate of 10 o C min -1 ; (b) XRD pattern of CoP-NB after annealed in air at 1050 o C for 2 h with a ramp rate of 5 o C min -1.

6 (a) Quantity Adsorbed (cm 3 g -1 STP) adsorption desorption Relative Pressure (P/P 0 ) (b) dv/dd (cm 3 g -1 nm -1 ) Pore size (nm) Figure S11. (a) N 2 adsorption-desorption isotherm of CoP-NB; (b) corresponding NLDFT pore diameter distribution of CoP-NB. Figure S12. XPS spectrum and high-resolution XPS spectra of CoP-NB. (a) full XPS spectrum; (b) Co2p; (c) P 2p and ( d) C 1s.

7 Figure S13. (a) CV curves of CoP-NB at a scan rate of 0.1 mv s -1 between 0.01 and 3.0 V vs. Li/Li + ; (b) charge-discharge voltage profiles of the CoP-NB for the first, second and third cycles in the voltage range of V at a current rate of 100 ma g -1. Figure S14. Charge/discharge curves of CoP nanoparticle. Figure S15. Specific capacity vs. cycle number of carbon.

8 Figure S16. SEM and TEM images of cycled CoP-NB. Figure S17. (a) Cyclic voltammograms of CoP-NB in the region of V vs. RHE at various scan rates. (b) Difference in current density (ΔJ =J a -J c ) at 0 V plotted versus scan rate fitted to a linear regression for the calculation of double-layer capacitance (C dl ) of CoP-NB.

9 Figure S18. CoP unit cell. Co atoms: pink, P atoms: purple. The lattice parameters from reference X-ray diffraction patterns (PDF card No ) is used to calculate the densities of active sites. The specific capacitance can be converted into an electrochemically active surface area (ECSA) using the specific capacitance value for a flat standard with 1 cm 2 of real surface area. The specific capacitance for a flat surface is generally found to be in the range of μf cm -2. In the following calculations of TOF, we assume 40 μf cm -2 as a moderate value. Calculated electrochemical active surface area: A = specific capacitance 40μFcm per cm ESCA -2 2 ECSA Turnover Frequency Calculations 1 To calculate the persite turnover frequency (TOF), we used the following formula: TOF= 2 number of totalhydrogen turnovers/cm of geometric area 2 number of active sites/cm of geometric area The total number of hydrogen turnovers was calculated from the current density according to: ma 1Cs 1mol of e 1mol of H H moleculars no.of H = j cm 1000mA C 2 mol of e 1mol H H 2 /s ma = per 2 2 cm cm Active sites per real surface area: 4atom/unit cell Active sites CoP = = atom cm nm /unit cell real Finally, the plot of current density can be converted into a TOF plot according to: 15 H 2 /s ma per 2 2 cm cm TOF= j surfacesites A ECSA

10 Figure S19. TOF curves of CoP-NB. Figure S20. XRD patterns of CoP-NB after 40h stability measurement.

11 Table S1. Comparison of the electrochemical data of the CoP-NB and newly reported cobalt phosphide anodes for LIBs. Material N, P-Codoped Porous Carbon/CoP Peapod-Like Current Density Cycle Number Capacity (mah g -1 ) 0.2 A g A g References 2 3 CoP Nanorods 0.2 C CoP Hollow Nanoparticle 0.2 C Co x P-NC Polyhedra CoP/RGO Nanocomposite CoP-NB 0.2 A g A g A g This work

12 Table S2. Comparison of the catalytic performance of the CoP-NB and newly reported cobalt phosphide anodes for HER. Material Scan rate η 10 ma cm -2 Tafel Slope (mv dec -1 ) References CoP/CNT 2 mv s CoP Hollow 9 5 mv s Polyhedron Ni 0.62 Co 0.38 P 5 mv s C- Co X P 5 mv s CoP Particles On Carbon Fiber 5 mv s Paper Hollow CoP Nanoarrays 5 mv s Co 2 P NRs 5 mv s COP-NB 5 mv s This work

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