Strained nickel phosphide nanosheet array - ACS Applied Materials

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Strained nickel phosphide nanosheet array Jingjing Duan, Sheng Chen, and Chuan Zhao ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b09147 • Publication Date (Web): 23 Aug 2018 Downloaded from http://pubs.acs.org on August 23, 2018

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ACS Applied Materials & Interfaces

Strained nickel phosphide nanosheet array Jingjing Duan, Sheng Chen, and Chuan Zhao* School of Chemistry, The University of New South Wales, Sydney, New South Wales 2052

ABSTRACT. We develop strained nickel phosphide nanosheets with 5 nm thickness and several hundreds of nanometers lateral size aligned on the top of nickel foam/nickel sulfide support. The material is characteristic of substantial compressive strain of 5.6% along nickel-phosphorus bond length, originated from the in-situ topotactic transformation. The architecture demonstrates excellent performances toward electrocatalytic hydrogen evolution with the turnover frequency exceeding its strain-free counterpart by a factor of 24. Further study reveals the strain effect leads to downshifts of d-band center in Ni-P bonds, weakens the adsorption to hydrogen species, and in turn facilitates hydrogen formation and desorption for boosted catalysis.

KEYWORDS. Metal phosphide; Strain engineering; In-situ transformation; Electrochemistry; Hydrogen evolution reaction

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Transition metal phosphides (TMPs), constructed by joining metal (M) and phosphorus (P) in the form of M-P chemical bonds, represent a class of versatile functional materials for a wide range of technical applications.1-7 The metal-phosphorus (M-P) bonds are basic subunits of TMPs formed via weak “ligand interaction” between metal and phosphorus atoms,2 and directly determine TMPs’ electronic structures, surface energies, and many other physical and chemical properties. For example, during the processes of electrochemical and catalytic reactions, the M-P bridge sites usually adsorb various reagent species such as hydrogen, lithium/sodium, and hydroxyl, where the charge transfer between M-P bonds and these species is the rate-determining step (RDS) of overall reactions.2-3,

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Particularly, the M-P bond length is recognized as an

important reactivity descriptor for the related reactions, which can affect the electron localization on both metal and phosphorus atoms that contributes to modulating the interactions with absorbents.2 Therefore, it is important to rationally modify the M-P bonds of TMPs, especially their bond lengths, to manipulate their intrinsic properties for various utilizations. Recently, strain engineering has received growing interest for precisely modifying the bond length, binding energy, and other properties of transition meal materials.9-12 In comparison to other strategies, this technique provides great flexibility for lattice adjustment inside a crystal that can be realized either in the absence or presence of a second component. Moreover, it can alter the atom spacing from deeply inside the material rather than at surfaces or close sublayers, thus offering the benefit of preventing cross-contamination during applications.9-11 Thus far, only a few strained TMPs have been illustrated including gallium phosphide nanowires by mechanical strain4 and indium phosphide by thermal induced deformation of substrates.5 Some key challenging problems remain in this research direction: i) The reported strained TMP materials are generally prepared in densely packed architecture without hierarchical porosity which could


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limit their use in many chemical or catalytic processes because of lacking efficient mass transport channels; (ii) The synthetic methods for introducing strains, like mechanical induced strain4 and thermal induced deformation of substrates,5 present difficulties for scalable production owing to the low yield and complicated procedures; (iii) A detailed mechanism study on the strain effect of TMPs over many electrochemical reactions has been scarcely explored. In this work, we fabricate strained nickel phosphide nanosheet array on large scale via a simple in-situ transformation procedure. The lattice coherence maintains over the entire nanosheet structure without dislocations despite of a substantial lattice constraint along Ni-P bond. The material features a number of attractive structural possesses including hierarchical porosity originated from macroporous nickel foam substrate and porous nanosheets, which are desirable for many gas-involved electrocatalytic reactions such as the hydrogen evolution reaction (HER). Typically, the material is synthesized by a facile two-step in-situ transformation procedure (Fig. 1a), starting by mixing nickel foam (NF, scanning electron microscope-SEM in Supplementary Fig. 1) with the sulfur precursor (thioacetamide) in a solvothermal environment. The decomposition of thioacetamide releases H2S gas to convert NF into NiS sheet array (Supplementary Fig. 2).13 Next, NiS is used as a support and template to be thermally annealed in the presence of phosphorus precursor (NaH2PO2), where the decomposition of NaH2PO2 releases PH3 to convert the nickel sulfide into strained nickel phosphide nanosheets (Denoted as NiSP, Supplementary Fig. 3), resulting in 5-layered heterostructure with NF as the core, two nickel phosphide layers as the surfaces, while sulfide sitting between NF and phosphide layers.8 For comparison, strain-free nickel phosphide (denoted as NiP) was prepared by directly annealing NF with the phosphorus precursor (SEM in Supplementary Fig. 4 and transmission


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electron microscope-TEM in Supplementary Fig. 5). The as-formed NiSP adopts a free-standing architecture of a few centimeters in size and several millimeters in thickness that resembles the geometrical diameter of NF, indicating the insitu conversion. The crystal phases of NiSP have been analyzed by X-ray diffraction (denoted as XRD; Figs. 1b,S6). Specifically, NF support has the crystal phase of metallic Ni (ICDD number: 00-003-1051); NiS precursor contains both NF (inside the core) and rhombohedral nickel sulfide (ICDD number: 00-001-1286), while NiSP contains small amount of NF and NiS, in addition to the dominant rhombohedral Ni8P3 phase in the space group of R3CH (a = 6.613 Å, c = 4.90 Å, α = 90 o, γ = 120 o, ICDD number: 01-078-1183). Interestingly, the XRD profile of NiP is similar to that of NiSP with NiS excluded, indicating similar crystal structures of nickel phosphides. The nickel sulfide precursor and phosphide product share a similar rhombohedral structure, suggesting a topotactic transformation from nickel sulfide to phosphide during the preparation process.14-15 The nanosheet array morphology of NiSP is imaged, several hundreds of nanometers in lateral size with pores ranging from several to tens of nanometers (Figs. 2a,S3b,S7a,S7b) and ~5 nm in thickness (Atomic Force microscope-AFM in Fig. 2e). Separated element domains of nickel, sulfur and phosphorus are observed in TEM energy-dispersive X-ray spectroscopy (EDS) element maps that further confirm the conversion from nickel sulfide template to phosphide (Figs. 2a-d,S7c-f). Moreover, the high-angle annular dark field (HAADF)-scanning transmission electron microscopy (STEM) reveals that the strained nanosheet consists of small single crystalline domains with well-defined atomic arrangement with a rhombohedral phase as shown in the schematic viewing along c-axis (Figs. 2f-i,S8,S9). The HAAD-STEM image taken from a larger area (Fig. 2i) shows continuous lines of atoms without dislocations across the nanosheet


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surfaces over 50 unit cells, thus indicating the full coherence of strained nanosheets. The chemical states of each component inside NiSP are investigated using X-ray photoelectron spectroscopy (XPS, Figs. 3a,3b,S10,S11, Table S1). According to the deconvoluted high resolution Ni 2p spectrum, both NiSP and NiP display the characteristic peaks of metallic Ni owing to their nickel skeleton from the nickel foam.16 The peak position of oxidized nickel (Ni+, Ni 2p3/2 and its satellite, Ni 2p1/2 and its satellite) only differs slightly, and Ni+ in NiSP has the higher binding energy than that of NiP, indicating a higher oxidation valence originated from the attenuated electron localization because of the compressive Ni-P strain.16-17 This result is further consistent with the downshift in binding energy of P 2p3/2 and P 2p1/2 in NiP bonds in the strained sample, indicating greater electron localization on the Ni sites. The degree of strain inside NiSP is determined by X-ray absorption spectroscopy (XAS) of Ni and P in energy-space, photoelectron wave vector (k)-space and k3-weighted radial distance (R)-space using the metallic nickel foil as the reference (Figs. 3c-f). The Ni K-edge peak derived from the 1s-3p transition in the near edge X-ray absorption spectra (NEXAS) shifts toward higher energies, from metallic nickel reference (8332.5 eV) to NiP (8332.7 eV) and NiSP (8334.4 eV), which also suggests the increase of oxidation states that is consistent with the XPS data.18-19 The high Ni oxidation valence in the NiSP can be ascribed to the more deficiency in the d-band occupation which enables an electron-donating ability, thus enhancing the HER activity of Ni sites.17, 20 Moreover, the features in the extended X-ray absorption fine structure (EXAFS) regime are originated from the scattering of the electron ionized from Ni by surrounding atoms; thus can give information of its spatial structure.18, 21 The oscillatory amplitudes of k-space of the as-prepared catalysts are slightly damped but close to metallic nickel foil reference, suggesting good crystalline order (Fig. 3d).18 The corresponding Fourier transformed R-space spectra show


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the information of the coordination situation of Ni atoms (Figs. 3e,f). The first peak set is originated from the first coordination shell in Ni, which is Ni-P bond, with the value of 1.7 Å in NiSP, 1.8 Å in NiP and Ni-S bond of 1.7 Å in NiS. The second coordination shell derived from the Ni-Ni bonds, which is 2.4 Å in NiSP, 2.5 Å in NiP and 2.4 Å in NiS, and 2.7 Å for metallic Ni.18, 21 Accordingly, NiSP has witnessed significant compressive strains of 4.0% in Ni-Ni bonds, 5.6% in Ni-P bonds in comparison to the NiP counterpart. Interestingly, the bond lengths of Ni-P in NiSP is close to that of Ni-S (1.7 Å) in NiS, further supporting the fact of topotactic transformation from nickel sulfide to phosphide during synthetic process. Owing to above advantageous features, NiSP exhibits good HER performance characterized by various electrochemical techniques (Figs. 4,S12, Table S2). Firstly, the required overpotential to achieve a geometric current density (Jgeo) of 10 mA cm-2 (η10, iR corrected, Fig. 4a) for NiSP is 68.4 mV, much lower than 177.0 mV for NiP, 248.2 mV for NiS and 235.7 mV for NF. Furthermore, we evaluate the quantity of the active sites using electrochemical active surface area (ECSA, Supplementary Figs. 13,14).22 Taking Pt foil as the reference, the calculated roughness factor is 32.0 for Pt/C, 5.1 for NiSP, 2.3 for NiP, 2.1 for NiS and 1.6 for NF, therefore the amount of active sites is increased by 2.2 times by the sulfide-templated synthesis. According to the Jgeo normalized by roughness factor (JECSA, Fig. 4b), η10-ECSA of NiSP is almost the same with that of Pt/C (104.7 mV vs 103.3 mV), suggesting an intrinsically competitive HER ability of this superstructure with commercial Pt with the surface area effect excluded. At high current density range (Jgeo>100 mA cm-2, JECSA>10 mA cm-2), HER capability of NiSP even outperforms Pt/C (limited by the mass-transfer despite fast kinetics) promoted by the same η, attributed to facile mass transfer resulted from the three-dimensional, conductive and hierarchical porous superstructure. Assuming all nickel atoms in the catalysts are active sites, the calculated TOF at


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200 mV are 2.4 × 10-5 s-1 for NF, 2.2 × 10-5 s-1 for NiS, 9.9 × 10-5 s-1 for NiP, and 2.4×10-3 s-1 for NiSP (Table S2,S4);23 therefore, the average TOF (which could represent the activity of each Ni atom) increased by at least 24 times owing to the strain effect. According to the Tafel plot (Fig. 4c), NiSP displays a small Tafel slope of 46.6 mV dec-1 (close to Pt/C of 29.9 mV dec-1) and much lower than that of NiP (91.6 mV dec-1), NiS (125.3 mV dec-1) and NF (114.4 mV dec-1). By extrapolating the Tafel plot, the exchange current density (j0, Fig. 4d) can be obtained, which is 0.072 mA cm-2 for NiSP (0.110 mA cm-2 for Pt/C), higher than that of 0.062 mA cm-2 of NiP, 0.047 mA cm-2 for NiS and 0.051 mA cm-2 for NF, suggesting a high standard rate constant of HER promoted by NiSP (j0 = Fk0C, k0 is the rate constant and C is reactant concentration). The facilitated kinetics is further supported by the smaller charge transfer resistance (Rct@332 mV) for NiSP (0.71 ohm cm2, Figs. 4e,S15) as comparison to other counterparts like NF (1.31 ohm cm2), NiS (2.36 ohm cm2), NiP (1.14 ohm cm2), even Pt/C (2.60 ohm cm2) at the high overpotential range. By comparison with recently reported electrocatalysts, NiSP ranks among the best HER catalysts to our best knowledge (Tables S2, S3).24-28 The NiSP electrode holds great promise for large-scale applications, showing good stability in both cyclic voltammetry (CV) and chronopotentiometry testing (Figs. 4f,S16,S17). The overpotential increases marginally after 50,000 CV cycles with seldom morphology and crystal structure alternation (Fig. S16). The electrode can smoothly work for 100-hour under 10, 20, 40, 60, 80 and 100 mA cm-2 current densities during the chronopotentiometry analysis (Fig. S17). Moreover, NiSP electrode can survive in highly concentrated KOH solution (e.g. 6 M KOH, Figs. S18,S19), and demonstrates competitive HER activity in neural electrolyte (1 M potassium buffer solution, Fig. S20), suggesting it is promising for commercial water electrolysis in a wide


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range of electrolytes. The significantly enhanced HER performance on NiSP is originated from its advantageous properties. Firstly, the compressive strain along Ni-P bond length is justified to facilitate charge transfer from Ni to P, and consequently reduces Rct from 1.14 to 0.71 ohm cm2. The enhanced Ni-P charge donation can alter d-band center of nickel sites that is usually more than half filled with electrons according to its 3d84s2 outer-layer electronic structure. When applying compressive strain to nickel phosphide, the width of the d-band is broadened (Fig. 4g), which reduces the degree of filling in d-band. Driven by thermodynamic forces,10, 29-30 the d band center downshifts to preserve its degree of filling to minimize surface energy, thereby leading to reduced binding energy between Ni-P chemical bonds to reagent species. Such a compressive strain effect has dominated the overall NiSP system that provides optimized chemical bonding energy to trap hydrogen intermediate for promoted HER kinetics. Secondly, NiSP sheets are synthesized from an in-situ transformation method via rational manipulation of the experimental parameters such as nickel precursors, reaction temperatures and durations. In addition, the in-situ transformation process allows for a small Rct for NiSP because of the intimate contact between layers in the heterostructure. Besides, the series resistance (Rs) of NiSP (0.8 ohm cm2) is even smaller than that of NF (1.02 ohm cm2) because of the d band vacancy increase and spontaneous surface oxidation of NF. Furthermore, the resultant NiSP adopts two-dimensional ultrathin microstructure in the form of macroscopic array electrode, which generates rich out-of-plane and in-plane pores for a facile gas transport, in addition to enormous accessible surfaces as catalytically active sites. All these contributors lead to significantly enhanced HER activity of NiSP over its strain-free counterpart. In conclusion, we develop an in-situ transformation method to synthesize ultrathin, strained


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nickel phosphide nanosheets with advantageous chemical and physical properties. The material is characteristic of a large compressible lattice strain along the Ni-P chemical bonds, low resistance, high mass loading of active species, hierarchical pores within the electrode, which is beneficial the charge and mass transfer in many applications. The strained induced catalyst shows high HER electrocatalytic ability with a small overpotential, low Tafel slope, high exchange current density and large electrochemically active surface areas. Our synthesis procedure involves only simple operation steps, low-cost precursors (nickel foam, thioacetamide, and NaH2PO2), and common laboratory instrumentation (Teflon-lined stainless-steel autoclave and tube furnace), therefore holds great promise for scalable production for widespread chemical and catalytic applications.

ASSOCIATED CONTENT Supporting Information. The Supporting Information is available free of charge on the ACS Publications website at DOI:xxx Material synthesis, physical, and electrochemical characterizations; Supplementary data: SEM, TEM, EDS, XRD, XPS data of related materials; Tables for comparison of HER performance with other materials in the literature. AUTHOR INFORMATION Corresponding Author *[email protected] ACKNOWLEDGMENT The authors thank for Dr Rosalie Hocking from James Cook University and Dr. César Ortiz


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Ledón from The University of Texas at Austin for helpful discussions on the analysis of XAS and electrochemistry. This research used equipment from the UNSW MWAC analytic centre and University of Wollongong Electron Microscopy Centre. We also acknowledge the financial support from the Australian Research Council (DP160103107) and UNSW Vice-Chancellor’s Research Fellowship (S.C.). REFERENCES 1.

Caban-Acevedo, M.; Stone, M. L.; Schmidt, J. R.; Thomas, J. G.; Ding, Q.; Chang, H. C.; Tsai, M. L.; He, J. H.; Jin, S., Efficient Hydrogen Evolution Catalysis Using Ternary PyriteType Cobalt Phosphosulphide. Nat. Mater. 2015, 14, 1245-1251.

2.

Zhang, G.; Wang, G.; Liu, Y.; Liu, H.; Qu, J.; Li, J., Highly Active and Stable Catalysts of Phytic Acid-Derivative Transition Metal Phosphides for Full Water Splitting. J. Am. Chem. Soc. 2016, 138, 14686-14693.

3.

Sun, M.; Liu, H.; Qu, J.; Li, J., Earth-Rich Transition Metal Phosphide for Energy Conversion and Storage. Adv. Energy Mater. 2016, 6, 1600087.

4.

Greil, J.; Assali, S.; Isono, Y.; Belabbes, A.; Bechstedt, F.; Valega Mackenzie, F. O.; Silov, A. Y.; Bakkers, E. P.; Haverkort, J. E., Optical Properties of Strained Wurtzite Gallium Phosphide Nanowires. Nano Lett. 2016, 16, 3703-3709.

5.

Sun, Y. T.; Baskar, K.; Lourdudoss, S., Thermal Strain in Indium Phosphide on Silicon Obtained by Epitaxial Lateral Overgrowth. J. Appl. Phys. 2003, 94, 2746-2748.

6.

Pu, Z.; Amiinu, I. S.; Kou, Z.; Li, W.; Mu, S., RuP2-Based Catalysts with Platinum-Like Activity and Higher Durability for the Hydrogen Evolution Reaction at All pH Values. Angew. Chem. Int. Ed. 2017, 56, 11559-11564.


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Page 11 of 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


7.

Wang, P.; Pu, Z.; Li, Y.; Wu, L.; Tu, Z.; Jiang, M.; Kou, Z.; Amiinu, I. S.; Mu, S., IronDoped Nickel Phosphide Nanosheet Arrays: An Efficient Bifunctional Electrocatalyst for Water Splitting. ACS Appl. Mater. Inter. 2017, 9, 26001-26007.

8.

Tian, J.; Liu, Q.; Asiri, A. M.; Sun, X., Self-Supported Nanoporous Cobalt Phosphide Nanowire Arrays: An Efficient 3D Hydrogen-Evolving Cathode over the Wide Range of pH 0-14. J Am. Chem. Soc. 2014, 136, 7587-7590.

9.

Xie, S.; Tu, L.; Han, Y.; Huang, L.; Kang, K.; Lao, K. U.; Poddar, P.; Park, C.; Muller, D. A.; DiStasio, R. A.; Park, J., Coherent, Atomically Thin Transition-Metal Dichalcogenide Superlattices with Engineered Strain. Science 2018, 359, 1131-1136.

10. Luo, M.; Guo, S., Strain-Controlled Electrocatalysis on Multimetallic Nanomaterials. Nat. Rev. Mater. 2017, 2, 17059. 11. Wang, H.; Xu, S.; Tsai, C.; Li, Y.; Liu, C.; Zhao, J.; Liu, Y.; Yuan, H.; Abild-Pedersen, F.; Prinz, F. B.; Nørskov, J. K.; Cui, Y., Direct and Continuous Strain Control of Catalysts with Tunable Battery Electrode Materials. Science 2016, 354, 1031-1036. 12. Bu, L.; Zhang, N.; Guo, S.; Zhang, X.; Li, J.; Yao, J.; Wu, T.; Lu, G.; Ma, J. Y.; Su, D.; Huang, X., Biaxially Strained PtPb/Pt Core/Shell Nanoplate Boosts Oxygen Reduction Catalysis. Science 2016, 354, 1410-1414. 13. Zhou, W.; Wu, X.-J.; Cao, X.; Huang, X.; Tan, C.; Tian, J.; Liu, H.; Wang, J.; Zhang, H., Ni3S2 Nanorods/Ni Foam Composite Electrode with Low Overpotential for Electrocatalytic Oxygen Evolution. Energy Environ. Sci. 2013, 6, 2921. 14. Niu, P.; Wu, T.; Wen, L.; Tan, J.; Yang, Y.; Zheng, S.; Liang, Y.; Li, F.; Irvine, J. T. S.; Liu, G.; Ma, X.; Cheng, H. M., Substitutional Carbon-Modified Anatase TiO2 Decahedral Plates


11


Page 12 of 19

Directly Derived from Titanium Oxalate Crystals Via Topotactic Transition. Adv. Mater. 2018, 30, 1705999. 15. Han, N.; Wang, Y.; Yang, H.; Deng, J.; Wu, J.; Li, Y.; Li, Y., Ultrathin Bismuth Nanosheets from in-Situ Topotactic Transformation for Selective Electrocatalytic CO2 Reduction to Formate. Nat. Commun. 2018, 9, 1320. 16. Huang, Z.; Chen, Z.; Chen, Z.; Lv, C.; Meng, H.; Zhang, C., Ni12P5 Nanoparticles as an Efficient Catalyst for Hydrogen Generation Via Electrolysis and Photoelectrolysis. ACS Nano 2014, 8, 8121-8129. 17. Bai, Y.; Fang, L.; Xu, H.; Gu, X.; Zhang, H.; Wang, Y., Strengthened Synergistic Effect of Metallic MxPy (M = Co, Ni, and Cu) and Carbon Layer Via Peapod-Like Architecture for Both Hydrogen and Oxygen Evolution Reactions. Small 2017, 13, 1603718. 18. Moreau, L. M.; Ha, D. H.; Zhang, H.; Hovden, R.; Muller, D. A.; Robinson, R. D., Defining Crystalline/Amorphous Phases of Nanoparticles through X-Ray Absorption Spectroscopy and X-Ray Diffraction: The Case of Nickel Phosphide. Chem. Mater. 2013, 25, 2394-2403. 19. Blanchard, P. E. R.; Grosvenor, A. P.; Cavell, R. G.; Mar, A., X-Ray Photoelectron and Absorption Spectroscopy of Metal-Rich Phosphides M2P and M3P (M = Cr−Ni). Chem. Mater. 2008, 20, 7081-7088. 20. Chen, W. F.; Sasaki, K.; Ma, C.; Frenkel, A. I.; Marinkovic, N.; Muckerman, J. T.; Zhu, Y.; Adzic, R. R., Hydrogen-Evolution Catalysts Based on Non-Noble Metal NickelMolybdenum Nitride Nanosheets. Angew. Chem. Int. Ed. 2012, 51, 6131-6135. 21. Kawai, T.; Sato, S.; Suzuki, S.; Chun, W. J.; Asakura, K.; Bando, K. K.; Matsui, T.; Yoshimura, Y.; Kubota, T.; Okamoto, Y.; Lee, Y. K.; Oyama, S. T., In-Situ X-Ray


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Absorption Fine Structure Studies on the Structure of Nickel Phosphide Catalyst Supported on K-USY. Chem. Lett. 2003, 32, 956-957. 22. Kibsgaard, J.; Tsai, C.; Chan, K.; Benck, J. D.; Nørskov, J. K.; Abild-Pedersen, F.; Jaramillo, T. F., Designing an Improved Transition Metal Phosphide Catalyst for Hydrogen Evolution Using Experimental and Theoretical Trends. Energy Environ. Sci. 2015, 8, 30223029. 23. Duan, J.; Chen, S.; Vasileff, A.; Qiao, S. Z., Anion and Cation Modulation in Metal Compounds for Bifunctional Overall Water Splitting. ACS Nano 2016, 10, 8738-8745. 24. Wang, P.; Zhang, X.; Zhang, J.; Wan, S.; Guo, S.; Lu, G.; Yao, J.; Huang, X., Precise Tuning in Platinum-Nickel/Nickel Sulfide Interface Nanowires for Synergistic Hydrogen Evolution Catalysis. Nat. Commun. 2017, 8, 14580. 25. Wang, X.; Kolen'ko, Y. V.; Bao, X. Q.; Kovnir, K.; Liu, L., One-Step Synthesis of SelfSupported Nickel Phosphide Nanosheet Array Cathodes for Efficient Electrocatalytic Hydrogen Generation. Angew. Chem. Int. Ed. 2015, 54, 8188-8192. 26. Pu, Z.; Wei, S.; Chen, Z.; Mu, S., Flexible Molybdenum Phosphide Nanosheet Array Electrodes for Hydrogen Evolution Reaction in a Wide pH Range. Appl. Catal. B: Environ. 2016, 196, 193-198. 27. Pu, Z.; Zhang, C.; Amiinu, I. S.; Li, W.; Wu, L.; Mu, S., General Strategy for the Synthesis of Transition-Metal Phosphide/N-Doped Carbon Frameworks for Hydrogen and Oxygen Evolution. ACS Appl. Mater. Interfaces 2017, 9, 16187-16193. 28. Zhang, C.; Pu, Z.; Amiinu, I. S.; Zhao, Y.; Zhu, J.; Tang, Y.; Mu, S., Co2P Quantum Dot Embedded N, P Dual-Doped Carbon Self-Supported Electrodes with Flexible and Binder-


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Free Properties for Efficient Hydrogen Evolution Reactions. Nanoscale 2018, 10, 29022907. 29. Mavrikakis, M.; Hammer, B.; Nørskov, J. K., Effect of Substrate Strain on Adsorption. Phys. Rev. Lett. 1998, 81, 2819. 30. Hammer, B.; Nørskov, J., Electronic Factors Determining the Reactivity of Metal Surfaces. Surf. Sci. 1995, 343, 211-220.


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Figure 1. Synthesis and structural characterizations of the strained nickel phosphide on Ni/NiS support (denoted as NiSP). (a) Schematic of synthetic procedure; (b) XRD profiles; (c,d) SEM images; (e) Optical image.


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Figure 2 Morphology characterizations of NiSP. (a) HAADF-STEM; (b-c) EDS element maps of Ni and P; (d) EDS spectrum; (e) AFM image and the height distribution curve; (f,i) High resolution HAADF-STEM image with relevant schematic crystal structure; (g) Reduced FFT transform image; (h) Schematic structure.


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Figure 3 Refined structural characterizations of NiSP. (a-b) High resolution XPS spectra of Ni 2p and P 2p; (c-e) XAS spectra (fluorescence mode) of energy-space, k-space, and R-space from nickel foil reference, NiS, NiP and NiSP; (f) the calculated bonding lengths of Ni-Ni and Ni-P (S) and the compressive strain degree.


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Figure 4 Electrocatalytic hydrogen evolution characterizations of NiSP. (a-b) Polarization curves with geometric current density and Jgeo normalized by ECSA, (c) Tafel slopes, (d) Exchange current density (j0, left) and overpotential@10 mA cm-2 (η10, right), (e) EIS spectra, inset is the equivalent circuit; (f) Polarization curves obtained before and after long-term CV scans. All the current densities were tested in 1 M KOH. All the data were obtained in 1M KOH and iR corrected. (g) Energy diagrams explaining the influence of compressive strain on the position of the d band center in nickel sites of Ni-P bonds.


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Strained nickel phosphide nanosheet array - ACS Applied Materials

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