Supporting Information Nest-like NiCoP for Highly Efficient Overall Water Splitting Cheng Du, a Lan Yang, a Fulin Yang, a Gongzhen Cheng a and Wei Luo a,b* a College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, Hubei 430072, P. R. China, Tel.: +86-27-68752366 *Corresponding author. E-mail addresses: wluo@whu.edu.cn. b Key laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Nankai University, Tianjin 300071, P. R. China Scheme S1. Schematic illustration of the nest-like NiCoP/CC fabrication process. S1
Figure S1. SEM images for NiCo2O4/CC Figure S2. EDS elemental mapping images of nest-like NiCoP/CC. S2
Figure S3. (a) and (b) XRD patterns for metal oxides and metal phosphides. Figure S4. N 2 adsorption-desorption isotherms of (a) nest-like NiCoP/CC, (b) Ni 2 P/CC, and (c) CoP/CC. Figure S5. EDX spectrum of nest-like NiCoP/CC. S3
Figure S6. SEM images for NiCoP/CC with different amounts of urea. (a, d) 5 mmol, (b, e) 10 mmol, (c, f) 20 mmol. Figure S7. SEM images for Ni0.33Co0.67P/CC (a, c) and Ni0.67Co0.33P/CC (b, d). S4
Figure S8. XRD patterns for NiCoP/CC, Ni 33 Co 67 P/CC and Ni 67 Co 33 P/CC. Figure S9. XPS survey scans for the nest-like NiCoP (a); High-resolution XPS spectra of (b) Co(2p), (c) Ni(2p), (d) P(2p), (e) O(1s) and (f) C(1s) peaks for the nest-like NiCoP/CC. S5
Figure S10. The current density per geometric surface area (black), and specific current densities per BET surface area (red) at 0.1 V overpotential for HER (a) and 0.27 V overpotential for OER (b) in 1 M KOH. Figure S11. (a) The HER polarization curves in 0.5 M H 2 SO 4 and (b) the OER polarization curves in 1 M KOH of 3D nest-like NiCoP/CC and NiCoP/CC nanoarray. The mass loading for electrodes was controlled to be ~1.3 mg cm -2. S6
Figure S12. High-resolution XPS spectra of (a) Co(2p), (b) Ni(2p), (c) P(2p) and (d) O(1s) peaks for the nest-like NiCoP/CC after OER test. Figure S13. Nyquist plots of nest-like NiCoP/CC, CoP/CC and Ni 2 P/CC recorded at (a) η = 60 mv in 0.5 M H 2 SO 4 solution, (b) η = 237 mv in 1 M KOH solution. S7
Figure S14. Cyclic voltammetries for (a) nest-like NiCoP/CC, (c) Ni 2 P/CC, and (e) CoP/CC. The capacitive currents at 0.10 V as a function of scan rate for (b) nest-like NiCoP/CC, (d) Ni 2 P/CC, and (f) CoP/CC in 0.5 M H 2 SO 4. S8
Figure S15. Cyclic voltammetries for (a) nest-like NiCoP/CC, (c) Ni 2 P/CC, and (e) CoP/CC. The capacitive currents at 0.96 V as a function of scan rate for (b) nest-like NiCoP/CC, (d) Ni 2 P/CC, and (f) CoP/CC in 1 M KOH. S9
Figure S16. Current-time slopes of chronoamperometric tests for HER in acid (a) and basic (b) solution; the voltage-time slopes of chronopotentiometric test for OER (c) and water (d). Figure S17. Faraday efficiency of H 2 and O 2 production. S10
Table S1 Comparison of the catalytic activity toward the HER in 0.5 M H 2 SO 4 of the nest-like NiCoP/CC with other reported high performance HER catalysts. Materials η10 (mv) Tafel slop Ref. (mv dec -1 ) Ni-P nanoplates/gc 110 73 1 Ni-P/carbon fiber paper 98 58.8 2 NiCoP /Ti 97 50 3 CoP/rGO 105 50 4 u-cop/ti 45 49.3 5 NiCoP/rGO 42 45.2 6 Ni5P4 films/ Ni foam 140 40 7 Ni2P nanorods arrays/ni foam 131 106.1 8 Ni5P4-Ni2P nanosheets array 120 79.1 9 Ni2P/carbon nanospheres 92 46 10 Ni12P5 nanoparticles/ti 107 63 11 CoP/CNT 122 54 12 CoP/CC 67 51 13 CoP/Ti 90 43 14 N2P nanoparticles/ti 120 60 15 Ni2P hollow NPs/Ti 116 46 16 CoP/NCNTs 383 62 17 NiP2 NS/CC 75 51 18 Ni2P/NRGO 102 59 19 NiCoP /CC 44 38.5 This work Table S2 Comparison of representative Co-based and Ni-based water- catalysts in alkaline electrolyte. Mass Materials loading (mg cm -2 ) Ni5P4 films/ NiOOH 3.475 NiCoP/Ni foam 1.6 Ni-P/carbon fiber paper 25.8 Water electrolysis test (in 1.0 M KOH) η10 Tafel Energy slop consumption of (mv) (mv the cells dec -1 ) (kwh (kgh2) -1 ) Mass activity at the overpotential of 0.3 V (ma g -1 ) HER 150 53 - - OER 290 40-3.2 >470 - >45.2 0.6 HER 32 37 - - OER 280 87-10 350-42.0 2.7 HER 117 85.4 - - OER 190 73-2.0 400-43.3 0.6 Fe-Co/carbon 1.2 HER 163 51 - - fiber papers 2 OER 283 34-14.3 Ref. 7 20 21 22 S11
- 450-44.7 2.6 HER >200 - - - OER 350 56-39.5 NiFe@NC 0.2 23 580-48.1 - HER 150 38 - - OER 340 66-1.5 CoP/rGO 0.28 4 470-45.2 - HER 94 42 - - OER 345 47-0.2 Co-P film 2.6 24 >400 - >43.3 0.2 HER 154 51 - - CoP N-doped OER 319 52-23.5 0.283 25 carbon >470 - >45.2 3.0 Ni-Co nanowire 0.3 OER 302 43.6-33 26 Ni Co P-300 0.286 HER 150 60.6 - - 27 C@NiCoP 0.65 HER 76 43 - - 28 HER 88 50 - - OER 300 96-35.1 CoP2/RGO 0.285 29 330-41.5 27.7 u-cop/ti 6.32 HER 60 49.1 - - 5 HER 209 124.1 - - NiCoP/rGO 0.15 NiCoP/Ni foam ~5 Ni0.51Co0.49P film OER 270 65.7-147.8 360-42.3 50.8 HER OER 133 (η 50) 308 (η 50) 540 (η 50) 68.6 - - - - 9.9-47.1 7.0 HER 82 43 - - OER 239 45 - - - 340-41.7 - HER 110 143 - - OER 310 145-3.3 Ni@C-400 NSs ~2.35 340-41.7 1.5 HER 130 58.5 - - OER 270 73.2-4.7 Ni/NiP 10.58 380-42.8 0.28 HER 111 60 - - OER 277 85.6-25.2 CoP NS/C 0.71 310-40.9 11.3 HER 54 51 - - OER 290 65-2.6 CoP-MNA 6.2 390 89 43.1 0.46 S12 6 30 31 32 33 34 35
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