Supporting Information A General Strategy for the Synthesis of Transition-Metal Phosphide/N-doped Carbon Frameworks for Hydrogen and Oxygen Evolution Zonghua Pu, Chengtian Zhang, Ibrahim Saana Amiinu, Wenqiang Li, Lin Wu, and Shichun Mu * State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, P. R. China * E-mail: msc@whut.edu.cn S-1
Table S1. Reaction conditions for the synthesis of several metal phosphides. Samples Ni/Co/Fe salt NH 4 H 2 PO 4 Temperature ( ) Ni 2 P@NC 1.68 mmol 7 mmol 700 Ni 12 P 5 @NC 1.68 mmol 7 mmol 800 Co 2 P@NC 4.0 mmol 2 mmol 800 CoP@NC 1.68 mmol 7 mmol 800 Fe 2 P@NC 4.0 mmol 2 mmol 800 FeP@NC 1.68 mmol 7 mmol 800 S-2
Figure S1. (a) STEM image and EDX elemental mapping images of (b,c) Ni, (d) P, (e) N and (f) C for for Ni 2 P@NC. S-3
Figure S2. (a) Low- and (b) high-magnification SEM images of bulk Ni 2 P. (c) XRD pattern of bulk Ni 2 P. S-4
Figure S3. Survey XPS spectra of Ni 2 P@NC. S-5
Figure S4. (a) Survey XPS spectrum of Ni 12 P 5 @NC. XPS spectra in the (b) Ni 2p, (c) P 2p, (d) N 1s and (e) C 1s regions for Ni 12 P 5 @NC. (f) Raman spectrum of as-prepared Ni 12 P 5 @NC. S-6
Figure S5. (a) Survey XPS spectrum of Co 2 P@NC. XPS spectra in the (b) Co 2p, (c) P 2p, (d) N 1s and (e) C 1s regions for Co 2 P@NC. (f) Raman spectrum of as-prepared Co 2 P@NC. S-7
Figure S6. (a) Survey XPS spectrum of CoP@NC. XPS spectra in the (b) Co 2p, (c) P 2p, (d) N 1s and (e) C 1s regions for CoP@NC. (f) Raman spectrum of as-prepared CoP@NC. S-8
Figure S7. (a) Survey XPS spectrum of FeP@NC. XPS spectra in the (b) Fe 2p, (c) P 2p, (d) N 1s and (e) C 1s regions for FeP@NC. (f) Raman spectrum of as-prepared FeP@NC. S-9
Figure S8. (a) Survey XPS spectra of Fe 2 P@NC. XPS spectra in the (b) Fe 2p, (c) P 2p, (d) N 1s and (e) C 1s regions for Fe 2 P@NC. (f) Raman spectrum of as-prepared Fe 2 P@NC. S-10
Figure S9. (a) TEM, (b) HRTEM images, and (c) XRD pattern of post-her Ni 2 P@NC. S-11
Figure S10. XPS spectra in the (a) Ni 2p, (b) P 2p, (c) N 1s and (d) C 1s regions for post-her Ni 2 P@NC. S-12
Figure S11. Size distribution of (a) Ni 2 P NPs in Ni 2 P@NC, (b) Ni 12 P 5 NPs in Ni 12 P 5 @NC, (c) CoP NPs in CoP@NC, (d) Co 2 P NPs in Co 2 P@NC, (e) FeP NPs in FeP@NC and (f) Fe 2 P NPs in Fe 2 P@NC. S-13
Figure S12. (a) TEM, (b) HRTEM images, and (c) XRD pattern of post-oer Ni 2 P@NC. S-14
Figure S13. XPS spectra in the (a) Ni 2p, (b) P 2p, (c) N 1s and (d) C 1s regions for post-oer Ni 2 P@NC. S-15
Figure S14. Polarization curve of Ni 2 P@NC catalyst couples for overall water splitting in 1.0 M KOH. S-16
Figure S15. CVs for (a) Fe 2 P@NC, (b) FeP@NC, (c) Co 2 P@NC, (d) CoP@NC, (e) Ni 2 P@NC and (f) Ni 12 P 5 @NC. (g) The difference in current density (j) between the anodic and cathodic sweeps ( j) versus scan rate; the slope of the fitting line is used for determination of the double-layer capacitance (C dl ). S-17
Figure S16. Comparison of BET for the six samples. S-18
Figure S17. Nyquist plots obtained by EIS for the six samples (Fe 2 P@NC, FeP@NC, Co 2 P@NC, CoP@NC, Ni 2 P@NC and (f) Ni 12 P 5 @NC) in 0.5 M H 2 SO 4 at overpotential of 120 mv. S-19
Table S2. Comparison of HER performance in acidic media for Ni 2 P@NC with nickel phosphide-based HER electrocatalyst. Catalyst Electrolyte Current density (j, ma cm -2 ) η at the corresponding j (mv) Ref. Ni 2 P@NC 0.5 M H 2 SO 4 10 138 This work Ni 2 P hollow nanoparticles 0.5 M H 2 SO 4 10 116 1 Ni 2 P nanoparticles 0.5 M H 2 SO 4 20 140 2 Ni 2 P NRs 0.5 M H 2 SO 4 10 265 3 Ni 2 P/Ti 0.5 M H 2 SO 4 10 120 4 Ni 2 P NCs 0.5 M H 2 SO 4 10 137 5 Ni 2 P 0.5 M H 2 SO 4 10 225 6 Ni 2 P-NRs 0.5 M H 2 SO 4 10 131 7 Ni 2 P/CNT 0.5 M H 2 SO 4 10 124 8 NiP 2 /CC 0.5 M H 2 SO 4 10 152 9 Ni 12 P 5 0.5 M H 2 SO 4 10 208 5 Ni 5 P 4 0.5 M H 2 SO 4 10 118 5 Ni 5 P 4 -Ni 2 P 0.5 M H 2 SO 4 10 120 10 S-20
Table S3. Comparison of OER performance in alkaline media for nickel phosphide-based OER electrocatalyst. Catalyst Electrolyte Current density (j, ma cm -2 ) η at the corresponding j (mv) Ref. Ni 2 P@NC 1.0 M KOH 10 320 This work Ni 2 P nanoparticles 1.0 M KOH 10 290 2 Ni 2 P nanowires 1.0 M KOH 10 400 11 Ni P films 1.0 M KOH 10 344 12 Ni P/CF 1.0 M KOH 10 325 13 Ni P nanoplate 1.0 M KOH 10 300 14 Ni 2 P/Ni/NF 1.0 M KOH 10 200 15 S-21
References (1) Popczun, E. J.; McKone, J. R.; Read, C. G.; Biacchi, A. J.; Wiltrout, A. M.; Lewis, N. S.; Schaak, R. E. Nanostructured Nickel Phosphide as an Electrocatalyst for the Hydrogen Evolution Reaction. J. Am. Chem. Soc. 2013, 135, 9267 9270. (2) Feng, L.; Vrubel, H.; Bensimon, M.; Hu, X. Easily-Prepared Dinickel Phosphide (Ni 2 P) Nanoparticles as an Efficient and Robust Electrocatalyst for Hydrogen Evolution. Phys. Chem. Chem. Phys. 2014, 16, 5917 5921. (3) Lu, A.; Chen, Y.; Li, H.; Dowd, A.; Cortie, M.; Xie, Q.; Guo, H.; Qi, Q.; Peng, D. Magnetic Metal Phosphide Nanorods as Effective Hydrogen-Evolution Electrocatalysts. Int. J. Hydrogen Energy 2014, 39, 18919 18928. (4) Pu, Z.; Liu, Q.; Tang, C.; Asiri, A. M.; Sun, X. Ni 2 P Nanoparticle Films Supported on a Ti Plate as an Efficient Hydrogen Evolution Cathode. Nanoscale 2014, 6, 11031 11034. (5) Pan, Y.; Liu, Y.; Zhao, J.; Yang, K.; Liang, J.; Liu, D.; Hu, Liu, W. D.; Liu, Y.; Liu, C. Monodispersed Nickel Phosphide Nanocrystals with Different Phases: Synthesis, Characterization and Electrocatalytic Properties for Hydrogen Evolution. J. Mater. Chem. A 2015, 3, 1656 1665. (6) Bai, Y. J.; Zhang, H. J.; Li, X.; Liu, L.; Xu, H. T.; Qiu, H. J.; Wang, Y. Novel Peapod-Like Ni 2 P Nanoparticles with Improved Electrochemical Properties for Hydrogen Evolution and Lithium Storage. Nanoscale 2015, 7, 1446 1453. (7) Wang, X.; Kolen ko, Y. V.; Liu, L. Direct Solvothermal Phosphorization of Nickel Foam to Fabricate Integrated Ni 2 P-Nanorods/Ni Electrodes for Efficient Electrocatalytic Hydrogen Evolution. Chem. Commun. 2015, 51, 6738 6741. (8) Pan, Y.; Hu, W.; Liu, D.; Liu, Y.; Liu, C. Carbon Nanotubes Decorated with Nickel Phosphide Nanoparticles as Efficient Nanohybrid Electrocatalysts for the Hydrogen Evolution Reaction. J. Mater. Chem. A 2015, 3, 13087 13094. (9) Jiang, P.; Liu, Q.; Sun, X. NiP 2 Nanosheet Arrays Supported on Carbon Cloth: an Efficient 3D Hydrogen Evolution Cathode in Both Acidic and Alkaline Solutions. Nanoscale 2014, 6, 13440 13445. S-22
(10) Wang, X.; Kolen'ko, Y. V.; Bao, X. Q.; Kovnir, K.; Liu, L. One-Step Synthesis of Self-Supported Nickel Phosphide Nanosheet Array Cathodes for Efficient Electrocatalytic Hydrogen Generation. Angew. Chem., Int. Ed. 2015, 54, 8188 8192. (11) Han, A.; Chen, H.; Sun, Z.; Xu, J.; Du, P. High Catalytic Activity for Water Oxidation Based on Nanostructured Nickel Phosphide Precursors. Chem. Commun. 2015, 51, 11626 11629. (12) Jiang, N.; You, B.; Sheng, M.; Sun, Y. Bifunctionality and Mechanism of Electrodeposited Nickel Phosphorous Films for Efficient Overall Water Splitting. ChemCatChem 2016, 8, 106 112. (13) Liu, Q.; Gu, S.; Li, C. Electrodeposition of Nickel Phosphorus Nanoparticles Film as a Janus Electrocatalyst for Electro-Splitting of Water. J. Power Sources 2015, 299, 342 346. (14) Yu, X.; Feng, Y.; Guan, B.; Lou, X.; Paik, U.; Carbon Coated Porous Nickel Phosphides Nanoplates for Highly Efficient Oxygen Evolution Reaction. Energy Environ. Sci. 2016, 9, 1246 1250. (15) You, B.; Jiang, N.; Sheng, M.; Bhushan, M. W.; Sun, Y. Hierarchically Porous Urchin-Like Ni 2 P Superstructures Supported on Nickel Foam as Efficient Bifunctional Electrocatalysts for Overall Water Splitting. ACS Catal. 2016, 6, 714 721. S-23