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 215006, China Jiangsu Provincial Key Laboratory for Advanced Carbon Materials and Wearable Energy Technologies, Soochow University, Suzhou 215006, China Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, China 1
Table S1 ICP results of the as-synthesized catalysts. samples Co-Cu 7 S 4-0.035 Co-Cu 7 S 4-0.07 Co-Cu 7 S 4-0.14 Molar concentration of Cu (mmol/l) Molar concentration of Co (mmol/l) Co/(Cu+Co) ratio 0.3357 0.0126 0.035 0.097 0.0075 0.07 0.195 0.0317 0.14 Figure S1. SEM of Co-Cu 7 S 4-0.035 sample. 2
Figure S2. SEM of Co-Cu 7 S 4-0.14 sample. Figure S3. TEM of Co-Cu 7 S 4-0.14 sample. 3
Figure S4. HRTEM of the nanoparticle in Co-Cu 7 S 4-0.14 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 4-0.14 reveals that the generated nanoparticles are cobalt oxides. 4
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 4-0.07 nanodisks. 5
Figure S8. XPS spectra of (a) Cu 2p, and (b) S 2p in Co-Cu 7 S 4-0.035. Figure S9. XPS spectra of (a) Cu 2p, and (b) S 2p in Co-Cu 7 S 4-0.14. 6
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 4-0.035 catalyst. 7
Figure S12. CV curves at scan rates from 10 to 50 mv s -1 of the Co-Cu 7 S 4-0.14 catalyst. Figure S13. N 2 adsorption-desorption isotherms of the as-prepared samples. 8
Figure S14. Nyquist plots of the Co-Cu 7 S 4-0.07 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
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
Figure S18. Co 2p XPS spectra in Co-Cu 7 S 4-0.035 after OER test. Figure S19. Co 2p XPS spectra in Co-Cu 7 S 4-0.14 after OER test. 11
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 4 17.30% 25.48% Co-Cu 7 S 4-0.035 27.47% 41.38% Co-Cu 7 S 4-0.07 43.12% 48.86% Co-Cu 7 S 4-0.14 37.16% 46.07% 12
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 4-0.07 before OER. The energy level is calculated to be 4.26 ev. 13
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
Table S3 OER performance comparison of some Cu and Co based catalysts. Catalytic Electrolyte Loading (mg cm - 2 ) Co-Cu 7 S 4-0.07 1.0 M KOH 1 Co-Cu 7 S 4-0.035 1.0 M KOH 1 Co-Cu 7 S 4-0.14 1.0 M KOH 1 Cu 7 S 4 1.0 M KOH 1 Fe 3 O 4 @Co 9 S 8 /rgo-2 α-ni(oh) 2 Spheres 1.0 M KOH 0.25 0.1 M KOH 0.2 CP/CTs/Co-S 1.0 M KOH 0.32 Cu 3 P-450 1.0 M KOH 0.25 TOF (s - 1 ) 0.08 @0.35V 0.036 @0.35V 0.045 @0.35V 0.0071 @0.35V 0.009 @0.35V 0.0361 @0.35V 0.12 @0.25V 0.1431 @0.31V 0.043 @0.351V Overpotential @10 ma cm -2 Reference 0.27 this work 0.32 this work 0.34 this work 0.51 this work 0.32 1 0.331 2 0.306 3 0.29 4 Cu 0.3 Co 2.7 O 4 nanochains 1.0 M KOH 0.2 0.351 5 Co 0.5 Fe 0.5 S@N- MC 0.1 M KOH 0.8 0.4 6 Ni 3 S 2 NR/NF 0.1 M KOH 37 0.187 7 Co 3 S 4 0.1 M KOH 0.283 0.363 8 NiCo 2 S 4 NW/NF 1.0 M KOH 0.4 9 CuCo 2 S 4 1.0 M KOH 0.7 0.32 10 Cu-CMP850 1.0 M KOH 0.45 11 NiCuO x 1.0 M NaOH >0.4 12 CuCo 2 O 4 /NrGO 1.0 M KOH 0.14 0.36 13 Co-P/Cu 1.0 M KOH 2.71 0.345 14 RuO 2 1.0 M KOH 0.8 0.387 15 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, 7077-7084. 2. 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, 7077-7084. 15
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