A V-doped nickel-phosphide material and its preparation method and application

Abstract

The present invention belongs to the technical field of electrolytic water catalysts and discloses a V-doped nickel phosphide material and its preparation method and application. The present invention uniformly grows a V-NiZn-LDH microsphere array on NF by a hydrothermal method, and then obtains a precursor with rich defects by a selective alkaline etching method, successfully preparing nickel iron phosphide V-Ni with rich surface defects anchored on nickel foam. vac 2P / NF. V‑Ni prepared in 1M KOH solution vac The 2P / NF self-supporting electrode exhibits excellent oxygen evolution and hydrogen evolution performance in water electrolysis. In situ Raman spectroscopy shows that during the OER process, defects significantly accelerate the reconstruction of adjacent nickel atoms into highly active NiOOH species, becoming the real catalytic active center. DFT calculations also show that the introduction of vacancies can improve the conductivity of the catalyst. In the step of adsorbing *OOH, V-Ni vac 2P / NF can effectively reduce the adsorption energy barrier of *OOH.

Description

Technical Field

[0001] The present invention belongs to the technical field of water electrolysis catalysts, and more particularly relates to a V-doped nickel-phosphorus material and a preparation method and application thereof. Background Art

[0002] Currently, non-renewable fossil fuels such as oil, coal, and natural gas account for over 80% of the global energy supply and dominate CO2 emissions. To ensure long-term sustainability, the production of green hydrogen through water electrolysis using renewable energy sources (such as solar and wind energy) is widely considered the most promising energy carrier for various end-use sectors. Commercial water electrolyzers typically require ultra-high-purity water as a feedstock to maximize their lifespan and save costs, which is an impractical approach in hot and arid regions with limited freshwater supplies. For example, Xinjiang has ample potential for photovoltaic and wind power generation. Compared to renewable energy sources, Xinjiang's inland location increases the cost of hydrogen production due to its abundant seawater reserves. Therefore, the electrolysis of brackish water offers a rich opportunity for regions with limited freshwater resources. Brine electrolysis can be divided into the HER and OER reactions, accompanied by competing anodic halide reactions, particularly the ClER. Therefore, the main challenge in brine electrolysis is to minimize the catalyst's overpotential for oxygen evolution, avoiding the ClER and thus selectively promoting the OER at the anode.

[0003] Among many catalysts, transition metal phosphides have attracted much attention due to their unique physical and chemical properties (including high conductivity, abundant reserves, etc.). However, among many catalysts, transition metal phosphides have attracted much attention due to their unique physical and chemical properties (including high conductivity, abundant reserves, etc.). Scientists have shown through a large number of experiments that the high HER activity of the Ni2P (001) surface can be attributed to the P-Ni bridge site bonding with the reaction intermediate with moderate strength after combining with P. With further research on transition metal phosphides, scientists have also developed a series of non-noble and noble, phosphorus-deficient and phosphorus-rich TMPs families with high activity for HER, OER, etc. in recent years. To date, a large number of studies are still focused on developing different preparation methods to obtain different TMPs, or exploring their different applications. Although Ni2P has been developed for hydrogen production, in the face of harsh brine electrolysis, we need to find a suitable strategy to modify it. At present, a large number of studies have greatly improved the catalytic performance of transition metal phosphides through the vacancy introduction strategy. Ionic vacancies can effectively reduce the OER energy barrier of transition metal phosphides to hydroxide oxides, thereby optimizing the binding energy of OER intermediates and enhancing the overall OER kinetics. Combined with the inherent high HER activity of Ni2P, transition metal phosphides can be prepared into efficient bifunctional catalysts.

[0004] Therefore, how to provide a V-doped nickel-phosphide material and its preparation method and application is a problem that those skilled in the art urgently need to solve. Summary of the Invention

[0005] In order to overcome the shortcomings and deficiencies of the prior art, the present invention provides a V-doped nickel-phosphide material and its preparation method and application, wherein nickel foam is used as a conductive substrate and Zn particles are used as a vacancy generating agent, a precursor with a spherical morphology is in situ grown on the surface of nickel foam by a hydrothermal method, and a micronized sphere array V-Ni is synthesized by alkaline etching and low-temperature phosphating. vac 2P / NF.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a V-doped nickel-phosphorus material, characterized by comprising the following steps:

[0008] (1) NiCl2·6H2O, Zn(NO3)2·6H2O, VCl3, NH4F, and (NH4)2CO were dissolved in deionized water with constant magnetic stirring to form a homogeneous solution;

[0009] (2) The homogeneous solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene, pretreated nickel foam was added, heated for reaction, and then naturally cooled to room temperature, repeatedly washed with deionized water, and vacuum dried at 60°C to obtain a V-NiZn-LDH / NF precursor;

[0010] (3) The V-NiZn-LDH / NF precursor was immersed in a KOH solution for alkaline etching, the defective products were collected and washed several times with deionized water and ethanol, and dried under vacuum at 60 °C to obtain the defective products;

[0011] (4) Place the defective product in a porcelain boat on the downstream side of the tube furnace, and add NaH2PO2 to another porcelain boat on the upstream side. Heat the tube furnace in an argon environment and keep it warm. Cool it naturally to room temperature to obtain V-Ni vac 2P / NF material.

[0012] Preferably, the molar ratio of NiCl2·6H2O, Zn(NO3)2·6H2O, VCl3, NH4F, (NH4)2CO and deionized water in step (1) is 1:0.4:0.2:6:5:1.67.

[0013] Preferably, the stirring time in step (1) is 30 minutes.

[0014] Preferably, the heating temperature in step (2) is 120° C. and the heating time is 8 h.

[0015] Preferably, the concentration of KOH in step (3) is 6 M, and the alkaline etching time is 6 h.

[0016] Preferably, the mass ratio of NaH2PO2 in step (4) to deionized water in step (1) is 0.5:30.

[0017] Preferably, the heating rate of the tubular furnace in step (4) is 2°C / min, the temperature is raised to 350°C, and the holding time is 2h.

[0018] The present invention also provides a V-doped nickel-phosphorus material prepared by the above method.

[0019] The present invention also provides application of the above-mentioned V-doped nickel-phosphorus material in salt water decomposition.

[0020] It can be seen from the above technical solutions that, compared with the prior art, the present invention provides a V-doped nickel-phosphorus material and its preparation method and application, which have the following beneficial effects:

[0021] (1) The present invention uniformly grows V-NiZn-LDH microsphere arrays on NF by a hydrothermal method, and then obtains a precursor with rich defects by a selective alkaline etching method, successfully preparing nickel iron phosphide V-Ni with rich surface defects anchored on nickel foam. vac 2P / NF. V-Ni prepared in 1M KOH solution vac The 2P / NF self-supporting electrode exhibits excellent oxygen evolution and hydrogen evolution performance in water electrolysis. The current density is 100 mA cm -2 The OER overpotential is only 330 mV and the stability is up to 2000 h. -2 At a current density of 1000 nm, the HER overpotential is only 70 mV. In situ Raman spectroscopy shows that during the OER process, defects significantly accelerate the reconstruction of adjacent nickel atoms into highly active NiOOH species, becoming the real catalytic active center. DFT calculations also show that the introduction of vacancies can improve the conductivity of the catalyst. In the step of adsorbing *OOH, V-Ni vac 2P / NF can effectively reduce the adsorption energy barrier of *OOH.

[0022] (2) The electronic interaction between the Zn vacancies and V introduced in the present invention and the introduction of Zn ion vacancies can also accelerate the reconstruction of the catalyst, improve the conductivity of the catalyst, and reduce the adsorption energy barrier from *O to *OOH, thereby improving the intrinsic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0024] Figure 1 V-Ni vac Schematic diagram of the synthesis of 2P / NF.

[0025] Figure 2 XRD patterns, where: (a) V-NiZn-LDH / NF; (b) V-Ni vac 2P / NF; (c)V-Ni vac 2P / NF, V, Zn-Ni2P / NF and V-Ni2P / NF.

[0026] Figure 3 Scanning electron microscopy images, including: (a) V-NiZn-LDH / NF; (b) V-Ni vac 2P / NF-1; (c) V-Ni vac 2P / NF, (d)V-Ni vac 2P / NF-2.

[0027] Figure 4 Scanning electron microscope images, where: (a), (b) V, Zn-Ni2P / NF; (c), (d) V-Ni vac 2P / NF; (e), (f) V-Ni2P / NF.

[0028] Figure 5 V-Ni vac Characterization images of 2P / NF, including: (a) TEM image; (b) HRTEM lattice fringes; (c) SAED image; (d) element distribution map.

[0029] Figure 6 (a) is V-Ni vac Overall XPS spectra of 2P / NF and V, Zn-Ni2P / NF.

[0030] Figure 6 (b)-(e) are V-Ni vac XPS spectra of 2P / NF, including: (b) Ni 2p; (c) V 2p; (d) Zn 2p; (e) P 2p.

[0031] Figure 6 (f) is V-Ni vac Electron paramagnetic resonance spectra of 2P / NF and V, Zn-Ni2P / NF.

[0032] Figure 7 (a)-(b) are the LSV curves of V-Ni2P / NF with different V contents, where: (a) HER; (b) OER.

[0033] Figure 7 (c)-(d) are V-Ni with different Zn contents vac LSV curves of 2P / NF, where: (c) HER; (d) OER.

[0034] Figure 8 (a)-(d) are the OER performances of each material, including: (a) LSV curve; (b) Tafel; (c) Nyquist; (d) C dl ;(e)V-Ni vac Polarization curves of 2P / NF before and after 5000 CV cycles; (f) V-Ni vac Chronopotentiometry curves of 2P / NF at 2000 h.

[0035] Figure 9 CV curves at different scan rates during the OER process, where: (a) V-Ni vac 2P / NF; (b) V, Zn-Ni2P / NF; (c) V-Ni2P / NF; (d) V-NiZn-LDH / NF.

[0036] Figure 10 (a)-(d) are the HER performance of each material, where: (a) LSV curve; (b) Tafel; (c) Nyquist; (d) C dl ;(e)V-Ni vac Polarization curves of 2P / NF before and after 5000 CV cycles; (f) V-Ni vac Chronopotentiometry curves of 2P / NF at 1000 h.

[0037] Figure 11 CV curves at different scan rates during the HER process, where: (a) V-Ni vac 2P / NF; (b) V, Zn-Ni2P / NF; (c) V-Ni2P / NF; (d) V-NiZn-LDH / NF.

[0038] Figure 12 (a)-(d) are the polarization curves of NFF(V, Na)-P||NFF(V, Na)-P, the amount of H2 and O2 fully hydrolyzed, the chronopotentiometry curves in 1M KOH, and the chronopotentiometry curves in 1M KOH+0.5M NaCl, respectively. DETAILED DESCRIPTION

[0039] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0040] The experimental drugs used in the present invention are shown in Table 1, the experimental instruments used are shown in Table 2, and the material characterization instruments used are shown in Table 3.

[0041] Table 1 Main experimental reagents and gases

[0042]

[0043]

[0044] Table 2 Experimental instruments

[0045]

[0046] Table 3 Instruments and models required for material characterization

[0047]

[0048] Example 1

[0049] The pretreatment method of nickel foam is as follows: add the nickel foam to 3M hydrochloric acid and ultrasonicate for half an hour, rinse twice with deionized water, then place it in deionized water and ultrasonicate for half an hour, and finally place it in a beaker containing ethanol and ultrasonicate for half an hour, and place the washed nickel foam in a vacuum drying oven overnight.

[0050] A method for preparing a V-doped nickel-phosphorus material, characterized by comprising the following steps:

[0051] (1) Dissolve 1 mmol NiCl2·6H2O, 0.4 mmol Zn(NO3)2·6H2O, 0.2 mmol VCl3, 6 mmol NH4F, and 5 mmol (NH4)2CO in 30 mL deionized water with constant magnetic stirring for 30 min to form a homogeneous solution;

[0052] (2) The homogeneous solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene, and pretreated nickel foam of 2 cm*3 cm was added. The mixture was heated at 120°C for 8 h, then naturally cooled to room temperature, washed with deionized water three times, and vacuum dried at 60°C to obtain a V-NiZn-LDH / NF precursor.

[0053] (3) The V-NiZn-LDH / NF precursor was immersed in a 6 M KOH solution for alkaline etching for 6 h, the defective product was collected and washed with deionized water and ethanol three times each, and dried under vacuum at 60 °C to obtain the defective product;

[0054] (4) The defective product was placed in a porcelain boat on the downstream side of the tube furnace, and 0.5 g of NaH2PO2 was added to another porcelain boat on the upstream side. The tube furnace was heated to 350 ° C at a rate of 2 ° C / min in an argon environment and kept warm for 2 h, and then cooled naturally to room temperature to obtain V-Ni vac 2P / NF material.

[0055] Comparative Example 1

[0056] The difference from Example 1 is that the amount of Zn(NO3)2·6H2O used in step (1) is 0.2 mmol. The rest is the same. vac 2P / NF-1 material.

[0057] Comparative Example 2

[0058] The difference from Example 1 is that the amount of Zn(NO3)2·6H2O used in step (1) is 0.6 mmol. The rest is the same. vac 2P / NF-2 material.

[0059] Comparative Example 3

[0060] The difference from Example 1 is that Zn(NO3)2·6H2O is not added in step (1). The rest is the same. V-Ni2P / NF material is obtained.

[0061] Comparative Example 4

[0062] The difference from Example 1 is that the alkaline etching in step (3) is omitted. The rest is the same. V, Zn-Ni2P / NF material is obtained.

[0063] Experiment 1 Characterization experiment

[0064] Firstly, V-NiZn-LDH microsphere arrays were uniformly grown on NF by a hydrothermal method, and then a V-NiZn-LDH / NF precursor with rich defects was obtained by selective alkaline etching. Finally, V-NiZn-LDH / NF precursor was obtained by phosphorylation in an Ar atmosphere. vac 2P / NF, such as Figure 1 As shown in the figure. As previously reported, Ni and Zn are both divalent cations, and Zn atoms will occupy the positions of Ni atoms. Therefore, Ni atoms close to Zn atoms are more susceptible to corrosion.

[0065] The electrocatalytic performance of the catalyst is closely related to the component content and structure. XRD was used to characterize the V-NiZn-LDH / NF precursor, V-Ni vac The crystal structures of 2P / NF and a series of comparative samples were analyzed. Figure 2 As shown in Figure a, the precursor can match well with Ni(OH)2(PDF#01-073-6992) and Zn(OH)2(PDF#00-012-0142), and V does not form a phase, indicating that the precursor is V-NiZn-LDH / NF. vac The diffraction peaks of 2P / NF catalyst match well with those of Ni2P ( Figure 2 b), the three strong peaks at 44.5°, 51.8° and 76.3° are attributed to the (111), (200) and (220) crystal planes of NF, respectively. The diffraction peaks at 30.4°, 31.8°, 35.4°, 40.6°, 44.6°, 47.4°, 54.2°, 54.4°, 55.1°, 74.7° and 74.9° 2θ correspond to the (110), (011), (200), (111), (021), (210), (300), (002), (211), (400) and (212) planes of Ni2P (PDF#65-3544), respectively. In addition to the peaks of Ni2P diffraction, there are no additional peaks, indicating that the obtained sample is a V-Ni with rich defects. vac 2P / NF. Figure 2 c. In addition, samples without Zn and without alkali etching were also tested. XRD showed that the phases of V-Ni2P / NF and V, Zn-Ni2P / NF were all different from those of V-Ni. vac 2P / NF is similar, indicating that the presence or absence of Zn ions does not affect the composition of the catalyst, but only affects the crystallinity of the substance. The presence of an appropriate amount of Zn ions will increase the crystallization of the catalyst. It can be seen from the illustration that after alkaline etching of Zn atoms, the peak position shifts to a low angle, indicating that the lattice is distorted.

[0066] Using scanning electron microscopy ( Figure 3 ) observed the morphology of V-NiZn-LDH / NF. It can be seen from the figure that the precursor is a "hairy" micron-sphere structure. The precursor samples with different zinc nitrate contents (0.2mmol, 0.4mmol, 0.6mmol) were phosphated and recorded as V-Ni vac 2P / NF-1, V-Ni vac 2P / NF, V-Ni vac 2P / NF-2. V-Ni vac 2P / NF-1 is a micron ball formed by nanosheets, V-Ni vacTo further verify the morphology of the catalyst, when the amount of Zn increased to 0.6mmol, the size of the microspheres also increased. When no Zn was added, it was found that the morphology of V-Ni2P / NF was similar to that of 0.2mmol Zn, indicating that the morphology of both the V-Ni2P / NF and the V-Ni2P / NF was microspheres formed by nanosheets. Figure 4 ); When the Zn content is appropriate, V-Ni vac 2P / NF shows a hollow microsphere array structure and grows uniformly on the NF. It is this hollow and rough structure that enables electrolysis to well infiltrate the catalyst, thereby improving the catalytic efficiency.

[0067] The present invention also carries out the characterization of TEM, such as Figure 5 As shown in a, it can be seen from TEM that V-Ni vac 2P / NF is a hollow microsphere structure, which is also consistent with the SEM image. Its thickness is about 500nm. From the high-resolution TEM (HR-TEM), it can be seen that ( Figure 5 b), the 0.19nm and 0.16nm lattice fringes in the microsphere belong to the (210) and (012) crystal planes of Ni2P (PDF#65-3544). The corresponding selected area electron diffraction (SAED) verifies that V-Ni vac The crystal structure of 2P / NF, in which the diffraction rings are associated with the (221) and (111) planes of Ni2P, respectively ( Figure 5 c). ICP (Inductively coupled spectroscopy) showed (Table 4), V-Ni vac 2P / NF can better meet the Ni:P ratio of about 2:1, and after alkaline etching, part of the Zn is reacted. 2+ , most of the Zn still exists with V-Ni vac 2P / NF. In addition, Figure 5 As shown in the elemental map in d, they are in V-Ni vac The distribution in 2P / NF is also very uniform, and Zn still exists 2+ , which is consistent with the results of ICP. The above analysis results show that the hollow structure of V-Ni was successfully prepared. vac 2P / NF microspheres.

[0068] Table 4V-Ni vac Inductively coupled spectroscopic data of 2P / NF and V, Zn-Ni2P / NF

[0069]

[0070] X-ray photoelectron spectroscopy (XPS) measurements were further used to carefully analyze the surface composition and chemical state.vac The overall XPS spectrum of 2P / NF clearly shows the signals of Ni, Zn, V and P elements ( Figure 6 a). From the overall XPS spectrum, it can be seen that after alkaline etching, V-Ni vac The signal peak of Zn in 2P / NF is weakened, which means that part of the Zn component has been removed. vac Ni 2p( Figure 6 b) High-resolution XPS spectrum shows typical p-orbital spin-orbit splitting signals. In the Ni2p XPS spectrum, the main peaks at 853.8 and 871.0 eV correspond to Ni-P, and there is a pair of peaks at binding energies of 857.1 and 875.2 eV corresponding to Ni 2p. 3 / 2 and 2p 1 / 2 Track, proves that Ni 3+ and Ni 2+ There is also a pair of satellite peaks located at. Figure 6 c shows the V-Ni vac High-resolution XPS spectra of Zn 2p in 2P / NF, V, and Zn-Ni2P / NF show Zn2p at 1022.37 and 1045.29 eV. 3 / 2 and Zn 2p 1 / 2 In addition, in addition to the V introduced by VCl3 3+ (515.41 / 522.81eV), V-Ni vac The XPS spectrum of V 2p in 2P / NF shows two pairs of peaks ( Figure 6 d), due to the redox reaction and contact with air, the two pairs of peaks belong to the surface oxidized V species, namely V 4+ (516.77 / 523.80eV) and V 5+ (517.83 / 524.83eV). Figure 6 e is the high-resolution P 2p spectrum of the electrocatalyst, P 2p 3 / 2 and P2p 1 / 2 The double peaks at 129.62 / 130.77 eV are attributed to the metal-P of the metal phosphide, while the peak at 133.85 eV is attributed to the surface oxidation of the phosphide. According to the above XPS results, the doping of V and the introduction of vacancies effectively optimize its electronic structure and further enhance its electrocatalytic activity. Figure 6 f is the electron paramagnetic resonance spectrum of the sample. It can be found that there is an obvious peak at g = 2.003, and after Zn etching, V-Ni vac The vacancies in 2P / NF are greatly increased.

[0071] Experiment 2: Electrochemical performance experiment

[0072] Electrochemical performance evaluation indicators include:

[0073] (1) Linear sweep voltammetry (LSV)

[0074] The test scan rate is 5mV·s -1 The polarization curve at this time is used to analyze the open circuit potential and overpotential of the catalyst in terms of current and voltage. The smaller the overpotential, the higher the catalytic activity.

[0075] (2) Cyclic voltammetry (CV)

[0076] The test sweep rates are 20, 40, 60, 80, and 100 mV·s. -1 The electrochemical active surface area (ECSA) of the electrocatalyst was evaluated by calculating the double-layer capacitance of the catalyst in the non-Faraday region from the CV curves.

[0077] (3) Electrochemical impedance spectroscopy (EIS)

[0078] The frequency range of EIS test is 0.01 to 10 5 Hz, AC amplitude of 5mV. Evaluate the reaction kinetics of the catalyst. EIS test potential is 10mA·cm -2 The corresponding potential.

[0079] (4) Stability test

[0080] CV testing observes changes in the LSV curve before and after cycling; smaller changes indicate better stability. Chronopotentiometry observes changes in potential during long-term testing at a fixed current; smaller changes indicate better durability. Furthermore, multi-step chronoamperometric testing can be used to compare the potential changes during different current ramps. Symmetry indicates good mass transfer.

[0081] Here are the results:

[0082] The V-Ni vac The electrocatalytic OER and HER performances of 2P / NF, V, Zn-Ni2P / NF, V-Ni2P / NF and V-NiZn-LDH / NF samples were investigated. As controls, Pt / C / NF and RuO2 / NF were also tested as industrial electrocatalysts. The amounts of V and Zn were also adjusted to optimize the performance of the catalysts. Figure 7 ), when V is 0.2mmol and Zn is 0.4mmol, V-Ni vac 2P / NF has the best performance.

[0083] Figure 8a shows the polarization curve of the OER test without iR compensation. In order to avoid the interference of metal ion oxidation reaction on oxygen evolution overpotential, linear sweep voltammetry (LSV) adopted a negative scan from high voltage to low voltage with a scan rate of 5 mV·s -1 The overpotentials were 194 and 330 mV, and the current densities were 10 and 100 mA·cm -2 When the current density is 10 mA·cm -2 , which is better than similar materials V, Zn-Ni2P / NF (226mV), V-Ni2P / NF (221mV), V-NiZn-LDH / NF (370mV) and commercial RuO2 / NF (222mV) electrocatalysts. vac The overpotential of 2P / NF is significantly lower than that of V, Zn-Ni2P / NF, indicating that the key to improving the activity of Ni vacancies generated by Zn atoms after alkaline corrosion is to improve the activity of Ni vacancies. Figure 8 In b, V-Ni vac Tafel slope of 2P / NF relative to V, Zn-Ni2P / NF (68.6mV·dec -1 )、V-Ni2P / NF(52.0mV·dec -1 )、V-NiZn-LDH / NF(65.9mV·dec -1 ) shows a lower value of 25.1 mV·dec -1 , showing a faster kinetic process during OER. It is worth noting that this phenomenon is also consistent with the results of electrochemical impedance spectroscopy ( Figure 8 c). V-Ni vac The charge transfer resistance of 2P / NF (4.5Ω) is much smaller than that of V, Zn-Ni2P / NF (6.4Ω), V-Ni2P / NF (7.4Ω), and V-NiZn-LDH / NF (63.1Ω). dl ) is an important signal for evaluating surface active sites. According to the reported calculation method, based on Figure 9 Calculate V-Ni from the CV results vac C of 2P / NF dl The value is 10.6mF·cm -2 ( Figure 8 d), which is superior to other similar materials and shows good OER active site supply capacity. Figure 4-8 As shown in e, V-Ni vac In addition to its excellent catalytic activity, 2P / NF also has good stability. vac The polarization curve of 2P / NF catalyst after 5000 CV cycles is almost the same as that before cycling, indicating that V-Ni vac2P / NF catalyst has good OER stability in alkaline electrolyte. Figure 8 f, at 100 mA·cm -2 The OER was tested under chronopotentiometry to evaluate the V-Ni vac The long-term stability of 2P / NF showed that V-Ni vac 2P / NF exhibits good stability for OER, with a voltage retention of 93.6% after 1300 h of testing.

[0084] Figure 10 a shows the polarization curve of HER test. V-Ni vac The 2P / NF electrocatalyst only needs an overpotential of 102 mV to reach 10 mA cm -2 Its performance is slightly higher than that of commercial Pt / C / NF (47mV), but better than similar materials V, Zn-Ni2P / NF (130mV), V-Ni2P / NF (152mV), V-NiZn-LDH / NF (280mV) and commercial electrocatalysts, showing excellent electrocatalytic performance. Figure 10 bLook, V-Ni vac 2P / NF shows 21.4mV·dec -1 V, Zn-Ni2P / NF (52.8mV·dec -1 )、V-Ni2P / NF(63.1mV·dec -1 )、V-NiZn-LDH / NF(88.6mV·dec -1 ) has a lower Tafel slope, which plays a faster kinetic process. Compared with V, Zn-Ni2P / NF (20.0Ω), V-Ni2P / NF (29.5Ω), and V-NiZn-LDH / NF (230.1Ω), V-Ni vac 2P / NF (18.4Ω) has lower R ct value( Figure 10 c), which is consistent with the results of Tafel slope, further confirming its higher catalytic activity. Figure 11 The CV results in C dl The value is 20.4mF·cm -2 ( Figure 10 d). Figure 10 e shows the V-Ni vac Polarization curve of HER of 2P / NF catalyst after 5000 CV cycles. vac The polarization curve of 2P / NF catalyst after 5000 cycles decreased slightly compared with the initial polarization curve, indicating that the V-Ni vac2P / NF catalysts have very good HER stability in alkaline electrolytes. Figure 10 f, at 100 mA·cm -2 The HER was tested under chronopotentiometry to evaluate the V-Ni vac The long-term stability of 2P / NF showed that V-Ni vac 2P / NF has good stability for HER, with a voltage retention rate of 96.7% after 1000 hours of testing.

[0085] The V-Ni vac The catalytic performance of 2P / NF as a bifunctional self-supporting electrode. The main problem in seawater electrolysis is the competitive CIER of hypochlorite formation in alkaline electrolytes. In addition, ions or microorganisms in seawater can block and poison the active sites, resulting in poor catalytic activity. The LSV curve shows ( Figure 12 a), V-Ni vac 2P / NF∥V-Ni vac The performance of 2P / NF pair in 1M KOH and 1MKOH+0.5MNaCl showed no significant change. The 2P / NF pair could drive 10 and 100 mA cm in 1MKOH+0.5MNaCl. -2 The required energy input is lower, at 1.42 and 1.64 V respectively. Figure 12 As can be seen in the volume change curve of water electrolysis in b, the volume ratio of O2 and H2 is about 1:2. The calculation also confirms that the Faradaic efficiency of HER and OER in the process of water electrolysis is about 100%. vac 2P / NF∥V-Ni vac The operational stability of 2P / NF pair when water / simulated seawater is decomposed into two electrolytes. -2 , the catalysts can operate stably for more than 1800 hours; in 1MKOH+0.5MNaCl, the catalysts can operate stably for nearly 1000 hours without obvious degradation ( Figure 12 c, d).

[0086] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the solutions disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method section.

[0087] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a V-doped nickel-phosphorus material, characterized in that: The following steps are involved: (1) NiCl2·6H2O, Zn(NO3)2·6H2O, VCl3, NH4F and (NH4)2CO were dissolved in deionized water under constant magnetic stirring to form a homogeneous solution; (2) The homogeneous solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene, and the pretreated nickel foam was added and heated for reaction. The mixture was then naturally cooled to room temperature, washed with deionized water for 2 to 3 times, and vacuum dried at 60 °C to obtain a V-NiZn-LDH / NF precursor. (3) The V-NiZn-LDH / NF precursor was immersed in a KOH solution for alkaline etching, and the defective products were collected and washed with deionized water and ethanol 2 to 3 times respectively, and dried under vacuum at 60 °C to obtain the defective products; (4) Place the defective product in a porcelain boat on the downstream side of the tube furnace, and add NaH2PO2 to another porcelain boat on the upstream side. Heat the tube furnace in an argon environment and keep it warm. Cool it naturally to room temperature to obtain V-Ni vac 2P / NF material, V-Ni vac Zn still exists in 2P / NF materials 2+ .

2. The method for preparing a V-doped nickel-phosphorus material according to claim 1, characterized in that: The molar ratio of NiCl2·6H2O, Zn(NO3)2·6H2O, VCl3, NH4F, (NH4)2CO and deionized water in step (1) is 1:0.4:0.2:6:5:1.

67.

3. The method for preparing a V-doped nickel-phosphorus material according to claim 1, characterized in that: The stirring time in step (1) is 30 min.

4. The method for preparing a V-doped nickel-phosphorus material according to claim 1, characterized in that: The heating temperature in step (2) is 120° C. and the heating time is 8 h.

5. The method for preparing a V-doped nickel-phosphorus material according to claim 1, characterized in that: The concentration of KOH in step (3) is 6 M, and the alkaline etching time is 6 h.

6. The method for preparing a V-doped nickel-phosphorus material according to claim 1, characterized in that: The mass ratio of NaH2PO2 in step (4) to deionized water in step (1) is 0.5:

30.

7. The method for preparing a V-doped nickel-phosphorus material according to claim 1, characterized in that: The heating rate of the tubular furnace in step (4) is 2°C / min, the temperature is raised to 350°C, and the holding time is 2h.

8. A V-doped nickel-phosphide material prepared according to the method according to any one of claims 1 to 7.

9. Use of the V-doped nickel-phosphide material according to claim 8 in brine electrolysis.

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