English

• INTRODUCTION

  Electrochemical water decomposition is one of the most attractive and sustainable technologies for the production of hydrogen by converting electrical energy into chemical energy.^[1-6] The water electrolysis is carried out through the oxygen evolution reaction at the anode to produce oxygen and the hydrogen evolution reaction (HER) at the cathode to produce hydrogen.^[7-11] HER is limited by the high price and stability of noble metal materials (Pt-based for HER), making them difficult to apply commercially on a large scale.^{[12, 13]}

  Nowadays, non-noble metal electrocatalysts with high activity and long-term stability for electrocatalytic hydrolysis have been intensively investigated, and big achievements have been made.^[14-17] On the other hand, it is well known that 96.5% of the global water resources is seawater, and freshwater resources are only about 1%,^[18] while little has been done on the seawater electrolysis due to the main challenge of the chlorine evolution reaction, leading to the corrosion and fast performance decay of the catalysts. Therefore, the exploration of seawater electrolysis catalysts with low cost, resistance to seawater corrosion, and excellent stability is desirable option to promote the commercialization of related fields.^{[19, 20]} The application of some non-noble metal catalysts to the seawater electrolysis has been studied, such as sulfides,^{[21, 22]} selenide,^{[23, 24]} phosphides,^{[20, 25]} oxides,^{[26, 27]} and nitrides,^{[28, 29, 13]} which showed great potential to replace the noble metals, and with the merits of low cost. However, there are still some urgent problems needed to be solved. Firstly, the current studies generally use simulated seawater instead of real seawater for the tests, while the effect of the complex environment of real seawater on the catalyst surface is avoided. Secondly, the electrocatalytic activity was only studied at a relatively low potential,^[30] which is far from the requirement of the industrial application (over 500 mA cm^-2). Thirdly, the synthesized methods are usually complex and time-consuming, which covers a shadow on the industrial application of the prepared catalysts. Hence, it is urgently needed to explore a simple and highly efficient strategy to prepare the catalysts for seawater electrolysis with high performance and large current densities.

  In this work, a one-step and rapid electrodeposition method to synthesize the P-Ni₄Mo/CF catalysts was proposed, which are highly efficient and durable for seawater electrolysis. P-Ni₄Mo/CF exhibited the current density of 100 mA cm^-2 with an overpotential (η) of ~260 mV, which is very competitive, and only 88 mV away from commercial Pt/C catalyst (172 mV). In addition, the catalyst also displayed excellent stability, and no performance decay can be observed after a durability test for 200 h. Furthermore, the P-Ni₄Mo/CF reaches an impressive current density of 1.0 A cm^-2 at an overpotential of 551 mV. It's proposed that the special nano-flower structure ensured abundant mass transfer channels and more active sites accessible, resulting in the high activity, and the performance was further enhanced with the P-doping. Our work not only develops a high-performance phosphorus-doped transition metal catalyst for seawater electrolysis, but also provides insights into the development of industry-standard, inexpensive catalysts.

  RESULTS AND DISCUSSION

  The P-Ni₄Mo/CF catalyst was synthesized by a one-step electrodeposition method, as shown in Figure 1a. P-Ni₄Mo is grown directly on the CF and spatially interconnected to form many voids. X-ray diffraction (XRD) patterns display those three peaks located at 43.54°, 50.64°, and 74.30° are assigned to (211), (310), and (420) planes of P-Ni₄Mo, respectively. Compared to Ni₄Mo (PDF#03-1036), the P-Ni₄Mo shows a negative shift in the diffraction peaks, suggesting the successful P doping (Figure 1b). Fi-gure 1c shows the uniform coverage of P-Ni₄Mo on the surface of CF. Figure 1d-e presents the formation of a nano-flower structure by catalyst P-Ni₄Mo/CF. This special structure has excellent catalytic activity specific surface area and abundant active material, which may facilitate the catalyst to fully contact the electrolyte and thus increase the reaction rate. Meanwhile, copper foam is a 3D porous material with excellent electrical conductivity and provides a large specific surface area favorable for electron transport, and the nano-flower structure of P-Ni₄Mo provides active and adsorption sites.

  Figure 1

  

  Figure 1.  (a) Synthetic illustration of P-Ni₄Mo/CF. (b) XRD patterns of P-Ni₄Mo. (c-e) SEM image of P-Ni₄Mo/CF.

  DownLoad: Full-Size Img PowerPoint

  The transmission electron microscopy (TEM) image shows that P-Ni₄Mo is uniformly distributed in the copper network and appears as nanosheets (Figure 2b). An overlapping lamellar shape of the nanosheets is observed in the HRTEM image (Figure 2c), which is consistent with the SEM data (Figure 1c). Figure 2d displays the distinct lattice spacing of 2.07 Å, which is consistent with the (211) planar distance of Ni₄Mo (Figure 2e). High magnification HAADF-TEM and energy-dispersive X-ray spectroscopy (EDS) images show that Ni, Mo, and P are uniformly distributed across the P-Ni₄Mo (Figure 2f-i). The chemical states of P-Ni₄Mo are studied by XPS (Figure 3a), and Figure 3b displays four peaks located at 856.18, 862.08, 873.88, and 880.28 eV, respectively. The two peaks appearing at 856.18 and 873.88 eV are assigned to Ni 2p_3/2 and Ni 2p_1/2 binding energies of Ni₄Mo, and the other two peaks at 862.08 and 880.28 eV are related to satellite peaks, respectively.^[31] Figure 2c shows that in the Mo 3d spectrum, the two peaks at Mo 3d_5/2 (232.18 eV) and Mo 3d_3/2 (235.28 eV) are attributed to the Ni₄Mo.^[32] In addition, two small peaks at 232.08 and 235.29 eV are attributed to Mo⁶⁺.^[33] The peaks of P 2p are centered at 132.68 and 133.38 eV, which are attributed to M-P and P-O, respectively (Figure 3d).^[34] Thus, this result combined with XRD and TEM confirms that P is successfully doped in the Ni₄Mo.

  Figure 2

  

  Figure 2.  (a-d) The TEM image of P-Ni₄Mo. (e) SAED pattern. (f) HAADF image of P-Ni₄Mo and (g-i) the corresponding elemental mappings of Ni (red), Mo (purple) and P (yellow).

  DownLoad: Full-Size Img PowerPoint

  Figure 3

  

  Figure 3.  (a) XPS spectra of P-Ni₄Mo, and high-resolution of (b) Ni 2p, (c) Mo 3d, and (d) P 2p.

  DownLoad: Full-Size Img PowerPoint

  In a typical three-electrode system, P-Ni₄Mo/CF was used directly as a working electrode to evaluate the electrocatalytic activity of P-Ni₄Mo/CF for HER under 1.0 M KOH + seawater. For comparison, the catalytic activities of Pt/C, Ni₄Mo/CF and bare CF were also measured. It can be seen that P-Ni₄Mo/CF exhibited a significant catalytic activity towards HER (Figure 4a), which is much higher than that of Ni₄Mo/CF and CF. P-Ni₄Mo/CF produced a current density of 100 mA cm^-2 at an overpotential (η) of 260 mV. In addition, the current density of 1.0 A cm^-2 can reach an overpotential of 551 mV, which is close to that of a commercial Pt/C catalyst (453 mV). As shown in Figure 4b, P-Ni₄Mo/CF possessed a lower overpotential of 150, 260, and 422 mV than those of Ni₄Mo/CF catalysts at current densities of 10, 100, and 500 mA cm^-2, respectively, implying that phosphorus doping can greatly enhance the catalytic activity. Figure S5 shows the performance of HER under three different electrolytes, KOH + seawater, KOH + NaCl, and KOH systems, and compares it with the literature, as shown in Table S1, suggesting the activity of P-Ni₄Mo/CF is comparable or even better than that of the recently published papers. The Tafel slope of 90.6 mV dec^-1 for P-Ni₄Mo/CF is slightly larger than that of Pt/C, while much lower than that of Ni₄Mo/CF (148.2 mV dec^-1) and CF (210.1 mV dec^-1), respectively, suggesting more favorable kinetics and higher catalytic activity of P-Ni₄Mo/CF catalyst (Figure 4c).

  Figure 4

  

  Figure 4.  (a) LSV curves of different materials. (b) Overpotential corresponding to different current densities. (c) Corresponding Tafel plots with linear fitting. (d) The estimation of C_dl. (e) EIS spectra were measured at 10 mA cm^-2. (f) Electrocatalysts efficiency of P-Ni₄Mo/CF for HER. (g) Multipotential stability test of P-Ni₄Mo/CF and long-term constant current stability test P-Ni₄Mo/CF at 10 mA cm^-2.

  DownLoad: Full-Size Img PowerPoint

  To better analyze the HER mechanism, the electrochemical impedance spectroscopy (EIS) was tested at an overpotential of 10 mA cm^-2, and the intrinsic properties of the prepared samples were evaluated (Figure 4d). The charge transfer resistance (R_ct) is related to the electrocatalytic kinetic properties of the electrolysis and catalyst interface. In general, smaller R_ct values indicated a faster electron transfer.^[35] The R_ct of P-Ni₄Mo/CF (R_ct = 1.2 Ω) is much lower than that of Ni₄Mo/CF (R_ct = 3.6 Ω) and CF (R_ct = 11.4 Ω), which indicated that P doping enhanced the conductivity of Ni₄Mo/CF.^[36] In addition, P-Ni₄Mo/CF, Ni₄Mo/CF, and CF all showed excellent conductivity, demonstrating excellent ion transfer between the electrode and electrolyte (Table S2).^[37] The electrochemically active surface area (ECSA) of different catalysts was evaluated, which can reflect the number of electrocatalytic active sites.^[38] The magnitude of (C_dl) can be determined by calculating the relationship between different scan rates and current density. As presented in Figure 4e, P-Ni₄Mo/CF showed a slope value of 45.9 mF cm^-2, which is remarkably larger than that of Ni₄Mo/CF (32.4 mF cm^-2), suggesting the introduction of P can increase the number of active sites and the catalytic activity. The actual versus theoretical hydrogen production of the P-Ni₄Mo/CF catalyst was measured at the current density of 100 mA cm^-2 for 108 min (Figure 4f). P-Ni₄Mo/CF gave a Faraday efficiency of ~99.1% in the HER process, demonstrating its excellent conversion efficiency. The Multi-order potential stability test was performed, and the test curve remained smooth at each stage as the current density increased from 10 to 50 mA cm^-2, indicating that P-Ni₄Mo/CF has good stability, conductivity, and excellent electron transfer capability (Figure 4g, green line). To evaluate the long-term stability of P-Ni₄Mo/CF, current density versus time (i-t) curves were recorded. P-Ni₄Mo/CF maintained its catalytic activity after a durability test at 10 mA cm^-2 for 200 h (Figure 4g, yellow line), which is much better than many recently published literatures, such as Ni-SA/NC only for 14 h,^[39] Ru-CoO_x/NF for 100 h,^[40] and Ni-SN@C for 40 h,^[28] demonstrating the high durability of P-Ni₄Mo/CF catalyst.^[41]

  The overall morphology of P-Ni₄Mo/CF after durability test was examined by SEM, and no big differences can be observed compared with the initial materials, suggesting the structural stability of the catalyst (Figure S3). XPS measurements were also performed after the durability test. Figure S4a shows the XPS of Ni, and two peaks centered at Ni 2p_3/2 (855.68 eV) and Ni 2p_1/2 (873.17 eV), respectively, corresponding to Ni(OH)₂,^[42] and the other two satellites peaks (861.48 and 879.67 eV) are related to NiO.^[43] For Mo 3d, two obvious peaks centered at 231.88 and 234.67 eV are attributed to the oxidation state of Mo, Mo⁵⁺ (Figure S4b).^{[44, 45]} For P 2p, the characteristic peaks located at 133.38 and 134.98 eV belong to PO₄^3- (Figure S4c).^[46] For O 1s (Figure S4d), three peaks located at 530.57, 530.98, and 532.58 eV are respectively attributed to M-O, OH^- and H₂O.^[47-49] Therefore, the catalyst undergoes surface reconstruction to form metal oxidate after the long-term stability, while the HER performance is still well preserved.

  CONCLUSIONS

  In summary, P-Ni₄Mo/CF catalysts were successfully prepared by a rapid one-step electrodeposition method, and were applied for the electrolysis of seawater. The overpotential at 100 mA cm^-2 is only 260 mV, and the current density can reach up to 1.0 A cm^-2 at the overpotential of 551 mV. P-Ni₄Mo/CF also exhibits significant HER stability and can be stably operated for 200 h. The excellent HER activity of the obtained P-Ni₄Mo/CF can be attributed to the high conductivity of the catalyst, the high specific surface area, and the electronic structure modulation due to the P doping. Our research may provide a new avenue for the development of cost-effective, highly stable and active catalysts for seawater electrolysis.

  
  ACKNOWLEDGEMENTS: This work was supported by the Natural Science Foundation of Hainan Province (221RC1018), the National Natural Science Foundation of China (22109034, 22109035, 52164028, 62105083), the Opening Project of Key Laboratory of Electrochemical Energy Storage and Energy Conversion of Hainan Province (KFKT2021007), and the Foundation of State Key Laboratory of Marine Resource Utilization in South China Sea (Hainan University, Grant No. MRUKF2021029). COMPETING INTERESTS
  The authors declare no competing interests.
  For submission: https://mc03.manuscriptcentral.com/cjsc
  ADDITIONAL INFORMATION
  Supplementary information is available for this paper at http://manu30.magtech.com.cn/jghx/EN/10.14102/j.cnki.0254-5861.2022-0110
  
• 1. [1]

     Tian, X.; Zhao, X.; Su, Y.-Q.; Wang, L.; Wang, H.; Dang, D.; Chi, B.; Liu, H.; Hensen, E. J.; Lou, X. W. Engineering bunched Pt-Ni alloy nanocages for efficient oxygen reduction in practical fuel cells. Science 2019, 366, 850-856. doi: 10.1126/science.aaw7493

  2. [2]

     Liu, Z.; Zeng, L.; Yu, J.; Yang, L.; Zhang, J.; Zhang, X.; Han, F.; Zhao, L.; Li, X.; Liu, H. Charge redistribution of Ru nanoclusters on Co₃O₄ porous nanowire via the oxygen regulation for enhanced hydrogen evolution reaction. Nano Energy 2021, 85, 105940. doi: 10.1016/j.nanoen.2021.105940

  3. [3]

     Feng, S.; Luo, J.; Li, J.; Yu, Y.; Kang, Z.; Huang, W.; Chen, Q.; Deng, P.; Shen, Y.; Tian, X. Heterogeneous structured Ni₃Se₂/MoO₂@Ni₁₂P₅ catalyst for durable urea oxidation reaction. Mater. Today Phys. 2022, 23, 100646. doi: 10.1016/j.mtphys.2022.100646

  4. [4]

     Yang, Y.; Wu, D.; Yu, Y.; Li, J.; Rao, P.; Jia, C.; Liu, Z.; Chen, Q.; Huang, W.; Luo, J.; Deng, P.; Shen, Y.; Tian, X. Bridge the activity and durability of ruthenium for hydrogen evolution reaction with the RuOC link. Chem. Eng. J. 2022, 433, 134421. doi: 10.1016/j.cej.2021.134421

  5. [5]

     Yu, Y.; Chen, Q.; Li, J.; Rao, P.; Li, R.; Du, Y.; Jia, C.; Huang, W.; Luo, J.; Deng, P.; Shen, Y.; Tian, X. Progress in the development of heteroatom-doped nickel phosphates for electrocatalytic water splitting. J. Colloid Interface Sci. 2022, 607, 1091-1102. doi: 10.1016/j.jcis.2021.09.032

  6. [6]

     Zheng, X.; Wu, D.; Liu, Y.; Li, J.; Yang, Y.; Huang, W.; Liu, W.; Shen, Y.; Tian, X. Photocatalytic reduction of water to hydrogen by CuPbSbS₃ nanoflakes. Mater. Today Energy 2022, 25, 100956. doi: 10.1016/j.mtener.2022.100956

  7. [7]

     Gao, M.; Zhou, W.-Y.; Mo, Y.-X.; Sheng, T.; Deng, Y.; Chen, L.; Wang, K.; Tan, Y.; Zhou, H. Outstanding long-cycling lithium-sulfur batteries by core-shell structure of S@Pt composite with ultrahigh sulfur content. Adv. Powder Mater. 2022, 1, 100006. doi: 10.1016/j.apmate.2021.09.006

  8. [8]

     Li, Z.; Wu, X.; Jiang, X.; Shen, B.; Teng, Z.; Sun, D.; Fu, G.; Tang, Y. Surface carbon layer controllable Ni₃Fe particles confined in hierarchical N-doped carbon framework boosting oxygen evolution reaction. Adv. Powder Mater. 2021, 1, 100020.

  9. [9]

     Li, P. Y.; Hong W. T.; Liu, W. Fabrication of large scale self-supported WC/Ni(OH)₂ electrode for high-current-density hydrogen evolution. Chin. J. Struct. Chem. 2021, 40, 1365-1371.

  10. [10]

      Yang, Y.; Yu, Y.; Li, J.; Chen, Q.; Du, Y.; Rao, P.; Li, R.; Jia, C.; Kang, Z.; Deng, P. Engineering ruthenium-based electrocatalysts for effective hydrogen evolution reaction. Nano-Micro. Lett. 2021, 13, 1-20. doi: 10.1007/s40820-020-00525-y

  11. [11]

      Rao, P.; Luo, J.; Li, J.; Huang, W.; Sun, W.; Chen, Q.; Jia, C.; Liu, Z.; Deng, P.; Shen, Y.; Tian, X. One-dimensional PtFe hollow nanochains for the efficient oxygen reduction reaction. Carbon Energy 2022, https://doi.org/10.1002/cey2.192 doi: 10.1002/cey2.192

  12. [12]

      Wu, Y. L.; Xie, N.; Li, X. F.; Fu, Z. M.; Wu, X. T.; Zhu Q. L. MOF-derived hierarchical hollow NiRu-C nanohybrid for efficient hydrogen evolution reaction. Chin. J. Struct. Chem. 2021, 40, 1346-1356.

  13. [13]

      Yu, L.; Zhu, Q.; Song, S.; McElhenny, B.; Wang, D.; Wu, C.; Qin, Z.; Bao, J.; Yu, Y.; Chen, S. Non-noble metal-nitride based electrocatalysts for high-performance alkaline seawater electrolysis. Nat. Commun. 2019, 10, 1-10. doi: 10.1038/s41467-018-07882-8

  14. [14]

      Deng, Y.; Luo, J.; Chi, B.; Tang, H.; Li, J.; Qiao, X.; Shen, Y.; Yang, Y.; Jia, C.; Rao, P.; Liao, S.; Tian, X. Advanced atomically dispersed metal-nitrogen-carbon catalysts toward cathodic oxygen reduction in PEM fuel cells. Adv. Energy Mater. 2021, 11, 2101222. doi: 10.1002/aenm.202101222

  15. [15]

      Rao, P.; Wang, T.-J.; Li, J.; Deng, P.; Shen, Y.; Chen, Y.; Tian, X. Plasma induced Fe-N active sites to improve the oxygen reduction reaction performance. Adv. Sens. Energy Mater. 2022, 1, 100005. doi: 10.1016/j.asems.2022.100005

  16. [16]

      Rao, P.; Wu, D.; Luo, J.; Li, J.; Deng, P.; Shen, Y.; Tian, X. A plasma bombing strategy to synthesize high-loading single-atom catalysts for oxygen reduction reaction. Cell Rep. Phys. Sci. 2022, 3, 100880. doi: 10.1016/j.xcrp.2022.100880

  17. [17]

      Tian, H.; Wu, D.; Li, J.; Luo, J.; Jia, C.; Liu, Z.; Huang, W.; Chen, Q.; Shim, C. M.; Deng, P.; Shen, Y.; Tian, X. Rational design ternary platinum based electrocatalysts for effective methanol oxidation reaction. J. Energy Chem. 2022, 70, 230-235. doi: 10.1016/j.jechem.2022.02.021

  18. [18]

      Dresp, S. R.; Dionigi, F.; Klingenhof, M.; Strasser, P. Direct electrolytic splitting of seawater: opportunities and challenges. ACS Energy Lett. 2019, 4, 933-942. doi: 10.1021/acsenergylett.9b00220

  19. [19]

      Wu, H. S.; Miao, T. F.; Shi, H. X.; Xu, Y.; Fu, X. L.; Qian, L. Probing photocatalytic hydrogen evolution of cobalt complexes: experimental and theoretical methods. Chin. J. Struct. Chem. 2021, 40, 1696-1709.

  20. [20]

      Ma, Y.-Y.; Wu, C.-X.; Feng, X.-J.; Tan, H.-Q.; Yan, L.-K.; Liu, Y.; Kang, Z.-H.; Wang, E.-B.; Li, Y.-G. Highly efficient hydrogen evolution from seawater by a low-cost and stable CoMoP@C electrocatalyst superior to Pt/C. Energy Environ. Sci. 2017, 10, 788-798. doi: 10.1039/C6EE03768B

  21. [21]

      Wang, C.; Zhu, M.; Cao, Z.; Zhu, P.; Cao, Y.; Xu, X.; Xu, C.; Yin, Z. Heterogeneous bimetallic sulfides based seawater electrolysis towards stable industrial-level large current density. Appl. Catal., B 2021, 291, 120071. doi: 10.1016/j.apcatb.2021.120071

  22. [22]

      Yu, L.; Wu, L.; McElhenny, B.; Song, S.; Luo, D.; Zhang, F.; Yu, Y.; Chen, S.; Ren, Z. Ultrafast room-temperature synthesis of porous S-doped Ni/Fe (oxy) hydroxide electrodes for oxygen evolution catalysis in seawater splitting. Energy Environ. Sci. 2020, 13, 3439-3446. doi: 10.1039/D0EE00921K

  23. [23]

      Chang, J.; Wang, G.; Yang, Z.; Li, B.; Wang, Q.; Kuliiev, R.; Orlovskaya, N.; Gu, M.; Du, Y.; Wang, G. Dual-doping and synergism toward high-performance seawater electrolysis. Adv. Mater. 2021, 33, 2101425. doi: 10.1002/adma.202101425

  24. [24]

      Yang, C.; Zhou, L.; Wang, C.; Duan, W.; Zhang, L.; Zhang, F.; Zhang, J.; Zhen, Y.; Gao, L.; Fu, F. Large-scale synthetic Mo@(2H-1T)-MoSe₂ monolithic electrode for efficient hydrogen evolution in all pH scale ranges and seawater. Appl. Catal., B 2022, 304, 120993. doi: 10.1016/j.apcatb.2021.120993

  25. [25]

      Wu, L. B.; Yu, L.; McElhenny, B.; Xing, X. X.; Luo, D.; Zhang, F. H.; Bao, J. M.; Chen, S.; Ren, Z. F. Rational design of core-shell-structured CoP_x@FeOOH for efficient seawater electrolysis. Appl. Catal. B-Environ. 2021, 294, 120256. doi: 10.1016/j.apcatb.2021.120256

  26. [26]

      Tran, P. K. L.; Tran, D. T.; Malhotra, D.; Prabhakaran, S.; Kim, D. H.; Kim, N. H.; Lee, J. H. Highly effective freshwater and seawater electrolysis enabled by atomic Rh-modulated Co-CoO lateral heterostructures. Small 2021, 17, 2103826. doi: 10.1002/smll.202103826

  27. [27]

      ul Haq, T.; Haik, Y. S doped Cu₂O-CuO nanoneedles array: free standing oxygen evolution electrode with high efficiency and corrosion resistance for seawater splitting. Catal. Today 2021, 17, 0920-5861.

  28. [28]

      Jin, H.; Wang, X.; Tang, C.; Vasileff, A.; Li, L.; Slattery, A.; Qiao, S. Z. Stable and highly efficient hydrogen evolution from seawater enabled by an unsaturated nickel surface nitride. Adv. Mater. 2021, 33, 2007508. doi: 10.1002/adma.202007508

  29. [29]

      Yu, L.; Wu, L.; Song, S.; McElhenny, B.; Zhang, F.; Chen, S.; Ren, Z. Hydrogen generation from seawater electrolysis over a sandwich-like NiCoN|Ni_xP|NiCoN microsheet array catalyst. ACS Energy Lett. 2020, 5, 2681-2689. doi: 10.1021/acsenergylett.0c01244

  30. [30]

      Liang, C.; Zou, P.; Nairan, A.; Zhang, Y.; Liu, J.; Liu, K.; Hu, S.; Kang, F.; Fan, H. J.; Yang, C. Exceptional performance of hierarchical Ni-Fe oxyhydroxide@NiFe alloy nanowire array electrocatalysts for large current density water splitting. Energy Environ. Sci. 2020, 13, 86-95. doi: 10.1039/C9EE02388G

  31. [31]

      Londoño-Calderón, V.; Ospina, R.; Rodriguez-Pereira, J.; Rincón-Ortiz, S. A.; Restrepo-Parra, E. Molybdenum and nickel nanoparticles synthesis by laser ablation towards the preparation of a hydrodesulfurization catalyst. Catalysts 2020, 10, 1076. doi: 10.3390/catal10091076

  32. [32]

      Du, W.; Shi, Y.; Zhou, W.; Yu, Y.; Zhang, B. Unveiling the in situ dissolution and polymerization of Mo in Ni₄Mo alloy for promoting the hydrogen evolution reaction. Angew. Chem. Int. Ed. 2021, 60, 7051-7055. doi: 10.1002/anie.202015723

  33. [33]

      Jin, Z.; Wang, L.; Chen, T.; Liang, J.; Zhang, Q.; Peng, W.; Li, Y.; Zhang, F.; Fan, X. Transition metal/metal oxide interface (Ni-Mo-O/Ni₄Mo) stabilized on N-doped carbon paper for enhanced hydrogen evolution reaction in alkaline conditions. Ind. Eng. Chem. Res. 2021, 60, 5145-5150. doi: 10.1021/acs.iecr.1c00039

  34. [34]

      Hao, Y.; Du, G.; Fan, Y.; Jia, L.; Han, D.; Zhao, W.; Su, Q.; Ding, S.; Xu, B. Mo/P dual-doped co/oxygen-deficient Co₃O₄ core-shell nanorods supported on Ni foam for electrochemical overall water splitting. ACS Appl. Mater. Interfaces 2021, 13, 55263-55271. doi: 10.1021/acsami.1c18813

  35. [35]

      Huang, S.; Ouyang, T.; Zheng, B. F.; Dan, M.; Liu, Z. Q. Enhanced photoelectrocatalytic activities for CH₃OH-to-HCHO conversion on Fe₂O₃/MoO₃: Fe-O-Mo covalency dominates the intrinsic activity. Angew. Chem. Int. Ed. 2021, 60, 9546-9552. doi: 10.1002/anie.202101058

  36. [36]

      Wang, X.; Wang, J.; Yu, B.; Jiang, W.; Wei, J.; Chen, B.; Xu, R.; Yang, L. Facile synthesis MnCo₂O_4.5@C nanospheres modifying PbO₂ energy-saving electrode for zinc electrowinning. J. Hazard. Mater. 2022, 428, 128212. doi: 10.1016/j.jhazmat.2021.128212

  37. [37]

      Lee, J.; Jung, H.; Park, Y. S.; Woo, S.; Yang, J.; Jang, M. J.; Jeong, J.; Kwon, N.; Lim, B.; Han, J. W. High-efficiency anion-exchange membrane water electrolyzer enabled by ternary layered double hydroxide anode. Small 2021, 17, 2100639. doi: 10.1002/smll.202100639

  38. [38]

      Xue, S.; Wu, G.; Li, M.; Liu, Z.; Deng, Y.; Han, W.; Lv, X.; Wan, S.; Xi, X.; Yang, D. Generalized assembly of sandwich-like 0D/2D/0D heterostructures with highly exposed surfaces toward superior electrochemical performances. Nano Res. 2022, 15, 255-263. doi: 10.1007/s12274-021-3468-y

  39. [39]

      Zang, W.; Sun, T.; Yang, T.; Xi, S.; Waqar, M.; Kou, Z.; Lyu, Z.; Feng, Y. P.; Wang, J.; Pennycook, S. J. Efficient hydrogen evolution of oxidized Ni-N₃ defective sites for alkaline freshwater and seawater electrolysis. Adv. Mater. 2021, 33, 2003846. doi: 10.1002/adma.202003846

  40. [40]

      Wu, D.; Chen, D.; Zhu, J.; Mu, S. Ultralow Ru Incorporated amorphous cobalt‐based oxides for high-current-density overall water splitting in alkaline and seawater media. Small 2021, 17, 2102777. doi: 10.1002/smll.202102777

  41. [41]

      Zheng, B.-F.; Ouyang, T.; Wang, Z.; Long, J.; Chen, Y.; Liu, Z.-Q. Enhanced plasmon-driven photoelectrocatalytic methanol oxidation on Au decorated α-Fe₂O₃ nanotube arrays. Chem. Commun. 2018, 54, 9583-9586. doi: 10.1039/C8CC04199G

  42. [42]

      Tao, S.; Wen, Q.; Jaegermann, W.; Kaiser, B. Formation of highly active NiO(OH) thin films from electrochemically deposited Ni(OH)₂ by a simple thermal treatment at a moderate temperature: a combined electrochemical and surface science investigation. ACS Catal. 2022, 12, 1508-1519. doi: 10.1021/acscatal.1c04589

  43. [43]

      Wang, F.; Sun, X.; Wang, Y.; Zhou, H.; Yin, J.; Zhang, X. Metallized Ni(OH)₂·NiO/FeOOH on Ni foam as a highly effective water oxidation catalyst prepared by surface treatment: oxidation-corrosion equilibrium. ACS Appl. Energy Mater. 2021, 4, 5599-5605. doi: 10.1021/acsaem.1c00384

  44. [44]

      Lu, Q.; Huang, B.; Zhang, Q.; Chen, S.; Gu, L.; Song, L.; Yang, Y.; Wang, X. Single-crystal inorganic helical architectures induced by asymmetrical defects in sub-nanometric wires. J. Am. Chem. Soc. 2021, 143, 9858-9865. doi: 10.1021/jacs.1c03607

  45. [45]

      Wang, M.; Ye, C.; Xu, M.; Bao, S. MoP nanoparticles with a P-rich outermost atomic layer embedded in N-doped porous carbon nanofibers: self-supported electrodes for efficient hydrogen generation. Nano Res. 2018, 11, 4728-4734. doi: 10.1007/s12274-018-2057-1

  46. [46]

      Yu, C.; Xu, F.; Luo, L.; Abbo, H. S.; Titinchi, S. J.; Shen, P. K.; Tsiakaras, P.; Yin, S. Bimetallic Ni-Co phosphide nanosheets self-supported on nickel foam as high-performance electrocatalyst for hydrogen evolution reaction. Electrochim. Acta 2019, 317, 191-198. doi: 10.1016/j.electacta.2019.05.150

  47. [47]

      Panigrahi, K.; Howli, P.; Chattopadhyay, K. K. Three-dimensional VO₂@PANI micro flower array for flexible supercapacitor. Mater. Lett. 2019, 253, 90-94. doi: 10.1016/j.matlet.2019.06.034

  48. [48]

      She, X.; Liu, L.; Ji, H.; Mo, Z.; Li, Y.; Huang, L.; Du, D.; Xu, H.; Li, H. Template-free synthesis of 2D porous ultrathin nonmetal-doped g-C₃N₄ nanosheets with highly efficient photocatalytic H₂ evolution from water under visible light. Appl. Catal., B 2016, 187, 144-153. doi: 10.1016/j.apcatb.2015.12.046

  49. [49]

      Wang, S.; Lu, Z.; Fang, Y.; Zheng, T.; Zhang, Z.; Wang, W.; Zhao, R.; Xue, W. Controllable synthesis of self-templated hierarchical Ni₃S₂@N-doped carbon for enhanced oxygen evolution reaction. Mater. Adv. 2021, 2, 3971-3980. doi: 10.1039/D1MA00229E

• 

  Figure 1  (a) Synthetic illustration of P-Ni₄Mo/CF. (b) XRD patterns of P-Ni₄Mo. (c-e) SEM image of P-Ni₄Mo/CF.

  下载: 全尺寸图片 幻灯片
  

  Figure 2  (a-d) The TEM image of P-Ni₄Mo. (e) SAED pattern. (f) HAADF image of P-Ni₄Mo and (g-i) the corresponding elemental mappings of Ni (red), Mo (purple) and P (yellow).

  下载: 全尺寸图片 幻灯片
  

  Figure 3  (a) XPS spectra of P-Ni₄Mo, and high-resolution of (b) Ni 2p, (c) Mo 3d, and (d) P 2p.

  下载: 全尺寸图片 幻灯片
  

  Figure 4  (a) LSV curves of different materials. (b) Overpotential corresponding to different current densities. (c) Corresponding Tafel plots with linear fitting. (d) The estimation of C_dl. (e) EIS spectra were measured at 10 mA cm^-2. (f) Electrocatalysts efficiency of P-Ni₄Mo/CF for HER. (g) Multipotential stability test of P-Ni₄Mo/CF and long-term constant current stability test P-Ni₄Mo/CF at 10 mA cm^-2.

  下载: 全尺寸图片 幻灯片
•