Supporting Information. Electronic Modulation of Electrocatalytically Active. Highly Efficient Oxygen Evolution Reaction

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1 Supporting Information Electronic Modulation of Electrocatalytically Active Center of Cu 7 S 4 Nanodisks by Cobalt-Doping for Highly Efficient Oxygen Evolution Reaction Qun Li, Xianfu Wang*, Kai Tang, Mengfan Wang, Chao Wang, and Chenglin Yan* Soochow Institute for Energy and Materials InnovationS, College of Physics, Optoelectronics and Energy, Soochow University, Suzhou , China Jiangsu Provincial Key Laboratory for Advanced Carbon Materials and Wearable Energy Technologies, Soochow University, Suzhou , China Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou , China 1

2 Table S1 ICP results of the as-synthesized catalysts. samples Co-Cu 7 S Co-Cu 7 S Co-Cu 7 S Molar concentration of Cu (mmol/l) Molar concentration of Co (mmol/l) Co/(Cu+Co) ratio Figure S1. SEM of Co-Cu 7 S sample. 2

3 Figure S2. SEM of Co-Cu 7 S sample. Figure S3. TEM of Co-Cu 7 S sample. 3

4 Figure S4. HRTEM of the nanoparticle in Co-Cu 7 S sample. The lattice fringe with an interplanar distance of around 0.2 nm is consistent well with the spacing of the (4 0 0) planes of the cubic Co 3 O 4 phase. Figure S5. EDX elemental mapping images of Co, S, and Cu for the Co-Cu 7 S reveals that the generated nanoparticles are cobalt oxides. 4

5 Figure S6. XRD patterns of the as-synthesized Cu 7 S 4 nanodisks and optimized Cu 7 S 4 crystal structure model. Figure S7. Absorption spectra of Cu 7 S 4 and Co-Cu 7 S nanodisks. 5

6 Figure S8. XPS spectra of (a) Cu 2p, and (b) S 2p in Co-Cu 7 S Figure S9. XPS spectra of (a) Cu 2p, and (b) S 2p in Co-Cu 7 S

7 Figure S10. CV curves at scan rates from 10 to 50 mv s -1 of the pure Cu 7 S 4 catalyst. Figure S11. CV curves at scan rates from 10 to 50 mv s -1 of the Co-Cu 7 S catalyst. 7

8 Figure S12. CV curves at scan rates from 10 to 50 mv s -1 of the Co-Cu 7 S catalyst. Figure S13. N 2 adsorption-desorption isotherms of the as-prepared samples. 8

9 Figure S14. Nyquist plots of the Co-Cu 7 S catalyst. M + OH - M-OH + OH - M-O + OH - M-OOH + OH - M-OH + e M-O + H 2 O + e M-OOH + e M-O 2 + H 2 O + e M-O 2 M + O 2 Figure S15. OER processes in alkaline media. M refers to the catalyst. 9

10 Figure S16. TEM image of the Cu 7 S 4 after OER. Figure S17. (a) HRTEM image and (b) SAED pattern of the Cu 7 S 4 after OER. 10

11 Figure S18. Co 2p XPS spectra in Co-Cu 7 S after OER test. Figure S19. Co 2p XPS spectra in Co-Cu 7 S after OER test. 11

12 Figure S20. S 2p XPS spectra in Co-Cu 7 S 4 samples after OER test. Table S2 Calculated concentration of SO 4 2- species from XPS. Samples Area of SO 2-4 before Area of SO 2-4 after measured measured Cu 7 S % 25.48% Co-Cu 7 S % 41.38% Co-Cu 7 S % 48.86% Co-Cu 7 S % 46.07% 12

13 Figure S21. Ultraviolet photoelectron spectroscopy (UPS) spectrum of pure Cu 7 S 4 before OER. The energy level of Cu 7 S 4 is calculated to be 4.48 ev. Figure S22. Ultraviolet photoelectron spectroscopy (UPS) spectrum of pure Co-Cu 7 S before OER. The energy level is calculated to be 4.26 ev. 13

14 Figure S23. Ultraviolet photoelectron spectroscopy (UPS) spectrum of pure Cu 7 S 4 before OER. The energy level of Cu 7 S 4 is calculated to be 3.59 ev. Figure S24. Ultraviolet photoelectron spectroscopy (UPS) spectrum of pure Cu 7 S 4 before OER. The energy level of Cu 7 S 4 is calculated to be 0.99 ev. 14

15 Table S3 OER performance comparison of some Cu and Co based catalysts. Catalytic Electrolyte Loading (mg cm - 2 ) Co-Cu 7 S M KOH 1 Co-Cu 7 S M KOH 1 Co-Cu 7 S M KOH 1 Cu 7 S M KOH 1 Fe 3 O 9 S 8 /rgo-2 α-ni(oh) 2 Spheres 1.0 M KOH M KOH 0.2 CP/CTs/Co-S 1.0 M KOH 0.32 Cu 3 P M KOH 0.25 TOF (s - 1 ) ma cm -2 Reference 0.27 this work 0.32 this work 0.34 this work 0.51 this work Cu 0.3 Co 2.7 O 4 nanochains 1.0 M KOH Co 0.5 Fe 0.5 S@N- MC 0.1 M KOH Ni 3 S 2 NR/NF 0.1 M KOH Co 3 S M KOH NiCo 2 S 4 NW/NF 1.0 M KOH CuCo 2 S M KOH Cu-CMP M KOH NiCuO x 1.0 M NaOH > CuCo 2 O 4 /NrGO 1.0 M KOH Co-P/Cu 1.0 M KOH RuO M KOH References 1. Gao, M.; Sheng, W.; Zhuang, Z.; Fang, Q.; Gu, S.; Jiang, J.; Yan, Y. Efficient Water Oxidation Using Nanostructured α-nickel-hydroxide as an Electrocatalyst. J. Am. Chem. Soc. 2014, 136, Gao, M.; Sheng, W.; Zhuang, Z.; Fang, Q.; Gu, S.; Jiang, J.; Yan, Y. Efficient Water Oxidation Using Nanostructured α-nickel-hydroxide as an Electrocatalyst. J. Am. Chem. Soc. 2014, 136,

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