Electronic Supplementary Material Co-vacancy-rich Co 1 x S nanosheets anchored on rgo for high-efficiency oxygen evolution Jiaqing Zhu 1, Zhiyu Ren 1 ( ), Shichao Du 1, Ying Xie 1, Jun Wu 1,2, Huiyuan Meng 1, Yuzhu Xue 1, and Honggang Fu 1 ( ) 1 Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People s Republic of China, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080, China 2 College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, China Supporting information to DOI 10.1007/s12274-017-1511-9 Table S1 The experimental parameters of the synthesized samples Sample Inventory Co(NO 3 ) 2 6 H 2 O NH 3 H 2 O C 3 H 7 NO 2 S GO Reaction mode Co 1 x S/rGO 0.05 mmol 1 ml 0.31 mmol 25 mg CoS/rGO 0.05 mmol 0.25 mmol 25 mg Co 1 x S 0.05 mmol 1 ml 0.31 mmol CoS 0.05 mmol 0.25 mmol Co 3 O 4 /rgo 0.05 mmol 1 ml 25 mg Co 1 x S/rGO-1 0.05 mmol 1 ml 0.31 mmol 25 mg Co 1 x S/rGO-p 0.05 mmol 1 ml 0.31 mmol 25 mg Address correspondence to Zhiyu Ren, zyren@hlju.edu.cn; Hongang Fu, fuhg@vip.sina.com
Table S2 Frequency analysis of the intermediates on {110} surface of Co 1 x S and CoS Sample OH* O* OOH* CoS Computed 272.825630 24.618386 286.029923 vibrational 124.345575 11.869355(i) 139.196837 frequencies 103.193740 10.958106(i) 118.814726 (mev) 18.230310 26.298764 10.227266 19.919208 13.466707(i) 7.610050 5.848142 15.300820(i) 54.979765(i) E ZPE (ev) 0.264 0.012 0.315 Co 1 x S Computed vibrational frequencies (mev) 279.213573 123.512516 115.525533 13.399337 0.753456 21.722640(i) 8.732130 5.400658 28.879691(i) 286.365801 138.481011 120.359093 24.733511 19.235603 7.909700 2.523353 14.376472(i) 54.896259(i) E ZPE (ev) 0.266 0.007 0.299 Figure S1 XRD pattern of CoS powder. www.editorialmanager.com/nare/default.asp
Figure S2 XPS survey spectrum of Co 1 x S/rGO hybrid (a), Co 1 x S (b), and CoS/rGO hybrids (c). Figure S3 SEM image of Co 1 x S/rGO hybrid. www.thenanoresearch.com www.springer.com/journal/12274 Nano Research
Figure S4 (a) (c) The SEM images of Co 1 x S, Co 3 O 4 /rgo hybrid and CoS/rGO hybrid; (d) the SEM images of Co 1 x S/rGO-1 hybrid synthesized by one-step hydrothermal reaction. Figure S5 (a) (c) XRD patterns of Co 1 x S/rGO-1 and Co 3 O 4 /rgo hybrids. Figure S6 XPS survey spectrum of Co 1 x S/rGO-P. www.editorialmanager.com/nare/default.asp
Figure S7 (a) (d) CVs for Co 1 x S/rGO hybrid, Co 1 x S, CoS/rGO hybrid, and CoS at various scan rate (10, 20, 40, 60, 80, 100, and 120 mv s 1 ); (e) the capacitive current at 0.15 V (vs. RHE) as a function of scan rate for Co 1 x S/rGO hybrid,cos/rgo hybrid, and CoS (Δj 0 = j a j c ). Figure S8 Nitrogen adsorption desorption isotherms of Co 1 x S/rGO hybrid (a), Co 1 x S (b), CoS/rGO hybrid (c), Co 1 x S/rGO-1 hybrid (d), and CoS (e). www.thenanoresearch.com www.springer.com/journal/12274 Nano Research
Figure S9 (a) and (b) ir-compensated OER polarization curves and the corresponding Tafel plots for Co 1 x S/rGO-1 and hybrids electrodes in 1.0 M KOH; (c) EIS data collected for Co 1 x S/rGO-1 and hybrids, under OER overpotential = 270 mv. Figure S10 (a) and (b) ir-compensated OER polarization curves and the corresponding Tafel plots for CoS and hybrids electrodes in 1.0 M KOH; (c) EIS data collected for CoS and hybrids, under OER overpotential = 270 mv. Table S3 Comparison of catalytic performance of Co 1 x S/rGO hybrid for OER to reported catalysts Materials Electrode Onset potential (V vs. RHE) Potential (at 10 ma cm 2, V vs. RHE) Tafel slope (mv dec 1 ) Electrolyte Co 9 S 8 /graphene GC 1.51 1.639 82.7 1 M KOH [S1] CoSe 2 GC 1.50 1.55 44 1 M KOH [S2] Co 3 S 4 GC 1.58 1.65 61.4 [S3] Fe 3 O 4 @Co 9 S 8 /rgo GC 1.48 1.55 65.5 [S4] Mn 3 O 4 /CoSe 2 GC 1.54 1.68 49 0.1M KOH [S5] NG-CoSe 2 GC 1.523 1.589 40 [S6] CoS 2 /N,S-GO GC 1.62 75 1 M KOH [S7] Co 1 x Fe x S@N-MC GC 1.57 1.64 159 0.1 M KOH [S8] NiCo 2 S 4 @N/S-rGO GC 1.7 156 [S9] Ni 3 S 2 /Ni Ni foam 1.387 159.3 1 M KOH [S10] Ni 3 S 2 /NF Ni foam 1.49 43 1 M KOH [S11] NiSe Ni foam 1.50 64 1 M KOH [S12] NiCo 2 S 4 Carbon 1.50 1.51 141 1 M KOH [S13] Co 1 x S/rGO GC 1.49 1.54 79 1 M KOH Ref. This work www.editorialmanager.com/nare/default.asp
Table S4 Parameters obtained by fitting the impedance spectra of Co 1 x S/rGO, CoS/rGO, Co 1 x S, CoS, and Co 1 x S/rGO-1 using the equivalent circuit in Fig. 4(c) Sample name R S (Ω) C C (μf) R C (Ω) C CT (μf) R CT (Ω) Co 1 x S/rGO 0.74 160 7.99 3640 45.9 Co 1 x S CoS 1.66 1.94 28.1 7.48 16.3 28.5 2210 1730 158 229 CoS/rGO 0.82 106 10.1 3240 62.4 Co 1 x S/rGO-1 1.07 40.5 12.3 2930 77.0 Figure S11 (a) and (b) Ball models of Co 1 x S and CoS, respectively; Co and S atom is depicted blue and yellow, respectively. Table S5 Atomic populations of (110) facets of Co 1 x S Species Ion s p d f Total Charge (e) S 1 1.88 4.31 0.00 0.00 6.19 0.19 S 2 1.83 4.25 0.00 0.00 6.08 0.08 S 3 1.79 4.30 0.00 0.00 6.09 0.09 S 4 1.83 4.25 0.00 0.00 6.08 0.08 S 5 1.88 4.31 0.00 0.00 6.20 0.20 S 6 1.88 4.31 0.00 0.00 6.19 0.19 S 7 1.83 4.25 0.00 0.00 6.08 0.08 S 8 1.79 4.30 0.00 0.00 6.09 0.09 S 9 1.83 4.25 0.00 0.00 6.08 0.08 S 10 1.88 4.31 0.00 0.00 6.20 0.20 Co 1 0.48 0.32 7.87 0.00 8.67 0.33 Co 2 0.44 0.56 7.89 0.00 8.89 0.11 Co 3 0.43 0.53 7.93 0.00 8.89 0.11 Co 4 0.44 0.56 7.89 0.00 8.88 0.12 Co 5 0.48 0.32 7.90 0.00 8.71 0.29 Co 6 0.43 0.57 7.90 0.00 8.90 0.10 Co 7 0.41 0.54 7.95 0.00 8.90 0.10 Co 8 0.43 0.57 7.89 0.00 8.89 0.11 www.thenanoresearch.com www.springer.com/journal/12274 Nano Research
Table S6 Atomic populations of (110) facets of CoS Species Ion s p d f Total Charge (e) S 1 1.86 4.34 0.00 0.00 6.20 0.20 S 2 1.79 4.28 0.00 0.00 6.07 0.07 S 3 1.79 4.28 0.00 0.00 6.07 0.07 S 4 1.79 4.28 0.00 0.00 6.07 0.07 S 5 1.86 4.34 0.00 0.00 6.20 0.20 S 6 1.86 4.34 0.00 0.00 6.20 0.20 S 7 1.79 4.28 0.00 0.00 6.07 0.07 S 8 1.79 4.28 0.00 0.00 6.07 0.07 S 9 1.79 4.28 0.00 0.00 6.07 0.07 S 10 1.86 4.34 0.00 0.00 6.20 0.20 Co 1 0.50 0.41 7.92 0.00 8.84 0.16 Co 2 0.41 0.55 7.93 0.00 8.89 0.11 Co 3 0.40 0.55 7.97 0.00 8.92 0.08 Co 4 0.41 0.55 7.94 0.00 8.90 0.10 Co 5 0.50 0.41 7.93 0.00 8.84 0.16 Co 6 0.50 0.41 7.92 0.00 8.84 0.16 Co 7 0.41 0.55 7.94 0.00 8.89 0.11 Co 8 0.40 0.55 7.97 0.00 8.92 0.08 Co 9 0.41 0.55 7.94 0.00 8.89 0.11 Co 10 0.50 0.41 7.93 0.00 8.84 0.16 Figure S12 Calculated projected DOS for bulk Co 1 x S (110) and CoS (110). Table S7 Free energy of (110) facets of Co 1-x S and CoS with intermediates Free energy (ev) Co 1 x S (110) CoS (110) Clean surface 11,124.944 13,210.575 OH* 11,577.498 13,663.375 O* 11,560.548 13,645.824 OOH* 12,011.361 14,096.681 www.editorialmanager.com/nare/default.asp
Table S8 Calculated reaction free energy (ΔG) with the E ZPE corrections ΔG (ev) Reaction step Co 1 x S (110) CoS (110) ΔG 1 * + OH *OH + e 2.1 1.9 ΔG 2 *OH + OH H 2 O + *O + e 0.43 0.09 ΔG 3 *O + OH *OOH + e 0.98 1.39 ΔG 4 *OOH + OH * + O 2 + e 0.69 0.42 References [S1] Dou, S.; Tao, L.; Huo, J.; Wang, S. Y.; Dai, L. M. Etched and doped Co 9 S 8 /graphene hybrid for oxygen electrocatalysis. Energy Environ. Sci. 2016, 9, 1320 1326. [S2] Liu, Y. W.; Cheng, H.; Lyu, M. J.; Fan, S. J.; Liu, Q. H.; Zhang, W. S.; Zhi, Y. D.; Wang, C. M.; Xiao, C.; Wei, S. Q. et al. Low overpotential in vacancy-rich ultrathin CoSe 2 nanosheets for water oxidation. J. Am. Chem. Soc. 2014, 136, 15670 15675. [S3] Zhao, W. W.; Zhang, C.; Geng, F. Y.; Zhuo, S. F.; Zhang, B. Nanoporous hollow transition metal chalcogenide nanosheets synthesized via the anion-exchange reaction of metal hydroxides with chalcogenide ions. ACS Nano 2014, 8, 10909 10919. [S4] Yang, J.; Zhu, G. X.; Liu, Y. J.; Xia, J. X.; Ji, Z. Y.; Shen, X. P.; Wu, S. K. Fe 3 O 4 -decorated Co 9 S 8 nanoparticles in situ grown on reduced graphene oxide: A new and efficient electrocatalyst for oxygen evolution reaction. Adv. Funct. Mater. 2016, 26, 4712 4721. [S5] Gao, M. R.; Xu, Y. F.; Jiang, J.; Zheng, Y. R.; Yu, S. H. Water oxidation electrocatalyzed by an efficient Mn 3 O 4 /CoSe 2 nanocomposite. J. Am. Chem. Soc. 2012, 134, 2930 2933. [S6] Gao, M. R.; Cao, X.; Gao, Q.; Xu, Y. F.; Zheng, Y. R.; Jiang, J.; Yu, S. H. Nitrogen-doped graphene supported CoSe 2 nanobelt composite catalyst for efficient water oxidation. ACS Nano 2014, 8, 3970 3978. [S7] Ganesan, P.; Prabu, M.; Sanetuntiku, J.; Shanmugam, S. Cobalt sulfide nanoparticles grown on nitrogen and sulfur codoped graphene oxide: An efficient electrocatalyst for oxygen reduction and evolution reactions. ACS Catal. 2015, 5, 3625 3637. [S8] Shen, M. X.; Ruan, C. P.; Chen, Y.; Jiang, C. H.; Ai, K. L.; Lu, L. H. Covalent entrapment of cobalt-iron sulfides in N-doped mesoporous carbon: Extraordinary bifunctional electrocatalysts for oxygen reduction and evolution reactions. ACS Appl. Mater. Interfaces 2015, 7, 1207 1218. [S9] Chen, S.; Qiao, S. Z. Hierarchically porous nitrogen-doped graphene NiCo 2 O 4 hybrid paper as an advanced electrocatalytic water-splitting material. ACS Nano 2013, 7, 10190 10196. [S10] Zhou, W. J.; Wu, X. J.; Cao, X. H.; Huang, X.; Tan, C. L.; Tian, J.; Liu, H.; Wang, J. Y.; Zhang, H. Ni 3 S 2 nanorods/ni foam composite electrode with low overpotential for electrocatalytic oxygen evolution. Energy Environ. Sci. 2013, 6, 2921 2924. [S11] Feng, L. L.; Yu, G. T.; Wu, Y. Y.; Li, G. D.; Li, H.; Sun, Y. H.; Asefa, T.; Chen, W.; Zou, X. X. High-index faceted Ni 3 S 2 nanosheet arrays as highly active and ultrastable electrocatalysts for water splitting. J. Am. Chem. Soc. 2015, 137, 14023 14026. [S12] Liu, X.; Liu, W.; Ko, M.; Park, M.; Kim, M. G.; Oh, P.; Chae, S.; Park, S.; Casimir, A.; Wu, G. et al. Metal (Ni, Co)-metal oxides/graphene nanocomposites as multifunctional electrocatalysts. Adv. Funct. Mater. 2015, 25, 5799 5808. [S13] Tang, C.; Cheng, N. Y.; Pu, Z. H.; Xing, W.; Sun, X. P. NiSe nanowire film supported on nickel foam: An efficient and stable 3D bifunctional electrode for full water splitting. Angew. Chem., Int. Ed. 2015, 127, 9483 9487. www.thenanoresearch.com www.springer.com/journal/12274 Nano Research