Supporting Information

Transcription

1 Supporting Information Quantum Dots of 1T Phase Transitional Metal Dichalcogenides Generated via Electrochemical Li Intercalation Wenshu Chen, Jiajun Gu,*, Qinglei Liu, Ruichun Luo, Lulu Yao, Boya Sun, Wang Zhang, Huilan Su, Bin Chen, Pan Liu, and Di Zhang*, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, , China School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, , China *Correspondence to: 1

2 Figure S1. XRD results of original CFP, the samples after calcination under 600 ºC for 1.5 h, and the samples experiencing sulfurization at 600 ºC for 20 min. After calcination, the XRD peaks of highly crystalline MoO 2 covered those of CFP (blue curve). Moreover, the rapid sulfurization process produced 2H-MoS 2 with low crystallinity and the peaks of CFP were observable in the XRD results (red curve). 2

3 Figure S2. SEM images of (a) and (b) the original CFP, (c) and (d) the MoO 2 grown on CFP under 600 ºC for 1.5 h, (d) and (e) the MoS 2 obtained via sulfurization under 600 ºC for 20 min. After calcination, MoO 2 flakes show lateral sizes ranging from 50 to 100 nm. 3

4 Figure S3. (a) Full XPS spectrum and (b) high-resolution XPS spectra (Mo 3d and S 2p) for the samples sulfurated on CFP under 600 ºC for 20 min. The XPS results confirm that the original MoS 2 is of 2H phase. 4

5 Figure S4. Typical discharge curve for the Li-MoS 2 battery with a discharge current density of A/g. The discharge process was cut off at 0.7 V. Figure S5. Intercalated Li amounts determined via discharge curves with different discharge current densities (using purchased MoS 2 as a cathode). 5

6 Figure S6. TEM images of the exfoliated MoS2 treated with discharge current densities of (a) 1.0 A/g, (b) 0.1 A/g, (c) 0.01 A/g, and (d) A/g. Figure S7. Enlarged HRTEM image of Figure 2e in the main text. 6

7 Figure S8. Mean lateral size of the exfoliated 2D MoS 2 obtained from the AFM data (Figure 2a-d in the main text). 7

8 Figure S9. HAADF-STEM images of the exfoliated 2D MoS2 QDs (0.001 A/g). The arrangements of atoms for H-MoS2 and T-MoS2 are given in the individual images (purple: Mo; yellow: S). The yellow dashed lines in (g) and (h) denote the boundaries between H and T phase. 8

9 Figure S10. XRD results of the exfoliated MoS 2 treated under different discharge current densities. 9

10 Figure S11. Raman spectra of the exfoliated MoS 2 treated under various discharge current densities. 10

11 Figure S12. (a) XPS results of the exfoliated MoS 2 treated with various discharge current densities. (b) Mole fractions of 1T (2H) phase calculated from the deconvolution area ratio in (a). The appearance of high binding energies of Mo 3d (Mo 6+ state, in purple line) may originate from the oxidation of Mo 4+ during sample preparation and XPS measurement. 11

12 Figure S13. CV results for RHE calibration in 0.5 M H 2 SO 4 solution. E (RHE) = E (SCE) V. Figure S14. XPS spectra of 2D MoS 2 QDs before and after HER cycles. (a) Full XPS spectra. (b) High-resolution XPS spectra for Mo 3d. The fluorine signals originated from the Teflon GC electrode. 12

13 Figure S15. SEM images of (a) MoSe 2, (b) WS 2 and (c) WSe 2 raw powders. 13

14 Figure S16. Discharge curves for (a) MoSe 2, (b) WS 2, and (c) WSe 2 with a discharge current density of A/g. These Li intercalation processes were cut off when x approached 2.0 for Li x MX 2 (estimated from the discharge time). 14

15 Figure S17. Full XPS spectra of (a) MoSe 2, (b) WS 2, and (c) WSe 2 before and after the Li intercalation (current density: A/g). The fluorine signals originated from the electrolyte in the battery. 15

16 Table S1. Summary of the electrochemical properties of the exfoliated MoS 2 electrodes. Sample η 10 [mv vs. RHE] Tafel slope [mv/dec] R s [Ω/cm 2 ] R ct [Ω/cm 2 ] J 0 [A/cm 2 ] 1.0 A/g MoS A/g MoS A/g MoS A/g MoS A/g MoS 2 after cycles Table S2. A survey on the HER performance of MoS 2 based electrocatalysts from recent literatures. Materials 1T content Loading [mg/cm 2 ] η 10 [mv vs. RHE] Tafel slope [mv/dec] J 0 [A/cm 2 ] Ref. 2D-MoS 2 QDs 94% This work MoS 2 on glass carbon electrode defect-rich MoS Disordered MoS MoS 2 80% MoS 2 100% double-gyroid MoS MoS 2 grown on graphite disc MoS 2 on 3D substrates MoS 2 grown on CFP 54% MoS 2 grown on CFP 55% 3.4~ Amorphous MoS 2.7@ NPG Monolayer MoS 2 on NPG MoS 2 on RGO Amorphous MoS 3 films Other types of MoS 2 [Mo 3S 13] 2- nanoclusters Pt-doped MoS Strained vacancy (SV-MoS 2) Cu 7S 4@MoS 2 heterostructure

17 References (1) Xie, J.; Zhang, H.; Li, S.; Wang, R.; Sun, X.; Zhou, M.; Zhou, J.; Lou, X. W. D.; Xie, Y., Defect-Rich MoS 2 Ultrathin Nanosheets with Additional Active Edge Sites for Enhanced Electrocatalytic Hydrogen Evolution. Adv. Mater. 2013, 25, (2) Xie, J.; Zhang, J.; Li, S.; Grote, F.; Zhang, X.; Zhang, H.; Wang, R.; Lei, Y.; Pan, B.; Xie, Y., Controllable Disorder Engineering in Oxygen-Incorporated MoS 2 Ultrathin Nanosheets for Efficient Hydrogen Evolution. J. Am. Chem. Soc. 2013, 135, (3) Voiry, D.; Salehi, M.; Silva, R.; Fujita, T.; Chen, M.; Asefa, T.; Shenoy, V. B.; Eda, G.; Chhowalla, M., Conducting MoS 2 Nanosheets As Catalysts for Hydrogen Evolution Reaction. Nano Lett. 2013, 13, (4) Geng, X.; Sun, W.; Wu, W.; Chen, B.; Al-Hilo, A.; Benamara, M.; Zhu, H.; Watanabe, F.; Cui, J.; Chen, T.-p., Pure and Stable Metallic Phase Molybdenum Disulfide Nanosheets for Hydrogen Evolution Reaction. Nat. Commun. 2016, 7, (5) Kibsgaard, J.; Chen, Z.; Reinecke, B. N.; Jaramillo, T. F., Engineering the Surface Structure of MoS 2 to Preferentially Expose Active Edge Sites for Electrocatalysis. Nat. Mater. 2012, 11, (6) Lukowski, M. A.; Daniel, A. S.; Meng, F.; Forticaux, A.; Li, L.; Jin, S., Enhanced Hydrogen Evolution Catalysis from Chemically Exfoliated Metallic MoS 2 Nanosheets. J. Am. Chem. Soc. 2013, 135, (7) Wang, H.; Lu, Z.; Xu, S.; Kong, D.; Cha, J. J.; Zheng, G.; Hsu, P.-C.; Yan, K.; Bradshaw, D.; Prinz, F. B., Electrochemical Tuning of Vertically Aligned MoS 2 Nanofilms and Its Application in Improving Hydrogen Evolution Reaction. Proc. Natl. Acad. Sci. USA 2013, 110, (8) Wang, H.; Lu, Z.; Kong, D.; Sun, J.; Hymel, T. M.; Cui, Y., Electrochemical Tuning of MoS 2 Nanoparticles on Three-Dimensional Substrate for Efficient Hydrogen Evolution. ACS Nano 2014, 8, (9) Ge, X.; Chen, L.; Zhang, L.; Wen, Y.; Hirata, A.; Chen, M., Nanoporous Metal Enhanced Catalytic Activities of Amorphous Molybdenum Sulfide for High-Efficiency Hydrogen Production. Adv. Mater. 2014, 26, (10) Tan, Y.; Liu, P.; Chen, L.; Cong, W.; Ito, Y.; Han, J.; Guo, X.; Tang, Z.; Fujita, T.; Hirata, A., Monolayer MoS 2 Films Supported by 3D Nanoporous Metals for High-Efficiency Electrocatalytic Hydrogen Production. Adv. Mater. 2014, 26, (11) Li, Y.; Wang, H.; Xie, L.; Liang, Y.; Hong, G.; Dai, H., MoS 2 Nanoparticles Grown on Graphene: an Advanced Catalyst for the Hydrogen Evolution Reaction. J. Am. Chem. Soc. 2011, 133, (12) Vrubel, H.; Hu, X., Growth and Activation of an Amorphous Molybdenum Sulfide Hydrogen Evolving Catalyst. ACS Catal. 2013, 3, (13) Kibsgaard, J.; Jaramillo, T. F.; Besenbacher, F., Building an Appropriate Active-Site Motif into a Hydrogen-Evolution Catalyst with Thiomolybdate [Mo 3 S 13 ] 2- Clusters. Nat. Chem. 2014, 6, (14). Deng, J.; Li, H.; Xiao, J.; Tu, Y.; Deng, D.; Yang, H.; Tian, H.; Li, J.; Ren, P.; Bao, X., Triggering the Electrocatalytic Hydrogen Evolution Activity of the Inert Two-Dimensional MoS 2 Surface via Single-Atom Metal Doping. Energy Environ. Sci. 2015, 8, (15) Li, H.; Tsai, C.; Koh, A. L.; Cai, L.; Contryman, A. W.; Fragapane, A. H.; Zhao, J.; Han, H. S.; Manoharan, H. C.; Abild-Pedersen, F., Activating and Optimizing MoS 2 Basal Planes for Hydrogen Evolution through the Formation of Strained Sulphur Vacancies. Nat. Mater. 2016, 15,

18 (16) Xu, J.; Cui, J.; Guo, C.; Zhao, Z.; Jiang, R.; Xu, S.; Zhuang, Z.; Huang, Y.; Wang, L.; Li, Y., Ultrasmall Cu 7 S 2 Hetero-Nanoframes with Abundant Active Edge Sites for Ultrahigh-Performance Hydrogen Evolution. Angew. Chem. Int. Ed. 2016, 55,