Simple preparation method of Ni2P / Fe3P electrocatalyst and application of Ni2P / Fe3P electrocatalyst in industrial hydrogen production

Abstract

The invention relates to the field of electrocatalysts, in particular to a simple preparation method of a Ni2P / Fe3P electrocatalyst and application of the Ni2P / Fe3P electrocatalyst in industrial hydrogen production. Nickel nitrate hexahydrate, ferric nitrate nonahydrate, dimethylacetamide, N, N-dimethylacetamide and deionized water are mixed under the stirring condition and subjected to a hydrothermal reaction to obtain a Fe1Ni1-MOF material, then the obtained Fe1Ni1-MOF material is placed in a tubular furnace to be phosphatized, the Ni2P / Fe3P catalyst is obtained, the preparation method is environmentally friendly and simple, the cost is low, the product is pure, and the method is suitable for industrial production. The method has certain stability and activity in an ampere-level industrial current scene, and has a good application prospect.

Description

Technical Field

[0001] The present invention relates to the field of electrocatalysts, and in particular to a simple preparation method of a Ni2P / Fe3P electrocatalyst and its application in industrial hydrogen production. Background Art

[0002] The core of hydrogen production from water electrolysis lies in the efficient synergy between the cathode hydrogen evolution reaction (HER) and the anode oxygen evolution reaction (OER). However, the current bottleneck restricting the large-scale application of this technology is the lack of inexpensive electrocatalysts that can combine high catalytic activity and long-term stability at industrial-grade amperometric current densities (>1Acm-2).

[0003] In recent years, due to the extensive work of researchers, reports on hydrogen production by water electrolysis have emerged one after another, and there are also many materials with high electrocatalytic activity. However, there are very few that can be adapted to actual industrial scenarios and put into application. This is because when facing actual working scenarios, there are some problems that are easily overlooked at low current densities. From the perspective of the external environment, at high current density, a large amount of H2 and O2 will be generated near the working electrode, which is manifested on a macroscopic scale as a large number of bubbles generated near the electrode. The bubbles will have a significant impact on the reaction system at high current density. First, the most intuitive is that the strong impact when the bubbles are generated can easily cause the catalyst to fall off, resulting in a 37-40% reduction in catalyst activity. Secondly, the bubbles may also adhere to the catalyst surface, affecting the charge-mass transfer rate between the active sites and the reactants. At the same time, a large amount of H2 and O2 will cause the working electrode to be degraded or corroded during long-term operation, thereby reducing its activity and stability. In addition, in addition to the influence of the external environment on high-current electrocatalysis, as the current density increases, the local environment of the electrocatalyst will also change, thereby affecting the catalytic performance. This is mainly due to the following two reasons. First, as current density increases, the bias voltage also increases, leading to a highly polarized state different from the equilibrium potential. Second, high current density triggers strong reactions, resulting in rapid consumption of reactants and formation of products. These factors further affect electron transfer, mass transport, and stability. Therefore, most current research on hydrogen production by water electrolysis focuses on low currents and cannot be applied to industrial hydrogen production.

[0004] CN 114016073B discloses an Fe-doped Ni-(0.85)Se nanosheet array, which has a high conductivity at 100 mA cm -2Its overpotential is about 1.52V at a current density of 1.53V. In addition, in terms of stability, most of the reported FeNi-based catalytic materials have good stability at low current densities at the milliampere level, but there is a lack of research on high current densities at the ampere level. For example, CN118600466A discloses a FeNi-MOF material, which has poor stability at ampere current densities; CN 119352088A discloses a FeNi-LDH@NF material, which has poor stability at ampere current densities at only 20mAcm under a constant current test at 1.53V. -2 It shows good stability but has no industrial applicability. In addition, the Co-Fe2P@NiP2 bimetallic phosphide disclosed in CN 118563352A has a high stability at 8 mA cm -2 At low current density, it is far from meeting the requirements of industrial applications.

[0005] Therefore, how to obtain stable electrocatalytic materials at high current densities at the ampere level through simple and efficient preparation methods is of great significance for industrial hydrogen production. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a simple preparation method of a Ni2P / Fe3P electrocatalyst and its application in industrial hydrogen production.

[0007] A simple preparation method of Ni2P / Fe3P electrocatalyst comprises the following steps:

[0008] (1) dissolving nickel nitrate hexahydrate and ferric nitrate nonahydrate in deionized water to obtain solution A;

[0009] (2) dissolving terephthalic acid in N,N-dimethylformamide to obtain solution B;

[0010] (3) Solution A and Solution B are mixed and stirred at a speed of 120-200 r / min for 20-60 min to obtain a reaction precursor solution; the reaction precursor solution is transferred to an autoclave and placed at 120-180° C. for reaction for 12-24 h. After naturally cooling to ambient temperature, the mixture is centrifuged, washed, and dried to obtain the product Fe1Ni1-MOF;

[0011] (4) The Fe1Ni1-MOF obtained in step (3) was placed in a tubular furnace, nitrogen was passed through, and sodium hypophosphite was placed 1-10 cm upstream of the Fe1Ni1-MOF along the nitrogen flow direction. The nitrogen flow rate was 50-80 ml / min, and the reaction was constant temperature calcined at 350°C for 2-4 hours. After cooling to room temperature, the Ni2P / Fe3P electrocatalyst was obtained.

[0012] Preferably, the molar ratio of nickel nitrate hexahydrate to ferric nitrate nonahydrate in step (1) is 1:1;

[0013] Preferably, the concentration of nickel nitrate hexahydrate in the solution A in step (1) is 0.2 mol / L;

[0014] Preferably, the concentration of terephthalic acid in the solution B in step (2) is 0.53 mol / L;

[0015] Preferably, the volume ratio of solution A to solution B in step (3) is 1:1;

[0016] Preferably, the volume of the reaction precursor solution in step (3) accounts for 50-75% of the volume of the autoclave;

[0017] Preferably, the mass ratio of Fe1Ni1-MOF and sodium hypophosphite in step (4) is 1:(5-15);

[0018] Preferably, the heating rate of the tubular furnace in step (4) is 1-2°C / min, and the cooling rate is 2-5°C / min.

[0019] The present invention also provides an application of a Ni2P / Fe3P electrocatalyst in industrial hydrogen production.

[0020] Beneficial effects of the present invention:

[0021] The present invention obtains a bimetallic Fe1Ni1-MOF through a simple hydrothermal reaction, and then obtains a Ni2P / Fe3P electrocatalyst through gas phase phosphating. The Ni2P / Fe3P electrocatalyst prepared by the present invention has an overpotential of only 1.35V without compensation. Compared with the same FeNi-based electrocatalytic material, the Ni2P / Fe3P electrocatalyst synthesized by the present invention has an activity increased by about 1.5 times at low current. More importantly, the Ni2P / Fe3P electrocatalyst prepared by the present invention has high stability at ampere-level current density and can be used in ampere-level industrial current scenarios.

[0022] In summary, the Ni2P / Fe3P electrocatalyst material prepared in the present invention has a simple preparation method, low cost, and good reproducibility. It not only has good performance under low current, but also has good stability and electrocatalytic performance under ampere-level industrial current. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 : X-ray diffraction (XRD) pattern of Fe1Ni1-MOF prepared in Example 1 and simulated theoretical XRD pattern.

[0024] Figure 2: High-resolution transmission electron microscopy (HERTEM) images of the Ni2P / Fe3P electrocatalyst prepared in Example 1: (a)

[111] crystal plane of Ni2P; (b)

[301] crystal plane of Fe3P.

[0025] Figure 3 : (a) is a scanning electron microscope (SEM) image of the Fe1Ni1-MOF electrocatalyst prepared in Example 1; (b) is a scanning electron microscope (SEM) image of the Ni2P / Fe3P electrocatalyst prepared in Example 1.

[0026] Figure 4 : Transmission electron microscopy (TEM) images of the Ni2P / Fe3P electrocatalyst prepared in Example 1: (a) 500nm; (b) 50nm.

[0027] Figure 5 : Scanning linear voltammetry performance test diagram of Fe1Ni1-MOF and Ni2P / Fe3P electrocatalysts in Test Example 1: (a) HER process; (b) OER process; the ordinate is the current density on the working electrode surface, and E is the voltage on the working electrode converted by the Nernst equation.

[0028] Figure 6 :The Ni2P / Fe3P electrocatalyst prepared in Example 1 is -2 Stability test at current density.

[0029] Figure 7 : Electrochemical impedance spectroscopy (EIS) of the Ni2P / Fe3P electrocatalyst prepared in Example 1. DETAILED DESCRIPTION

[0030] N,N-dimethylformamide: CAS number: 681-22-1.

[0031] Sodium hypophosphite: CAS number: 7681-53-0.

[0032] Example 1

[0033] A simple preparation method of Ni2P / Fe3P electrocatalyst comprises the following steps:

[0034] (1) dissolving nickel nitrate hexahydrate and ferric nitrate nonahydrate in deionized water to obtain solution A;

[0035] (2) dissolving terephthalic acid in N,N-dimethylformamide to obtain solution B;

[0036] (3) Solution A and Solution B were mixed and stirred at 160 r / min for 30 min to obtain a reaction precursor solution; the reaction precursor solution was transferred to an autoclave and reacted at 120°C for 12 h. After naturally cooling to ambient temperature, the product Fe1Ni1-MOF was obtained by centrifugation, washing, and drying.

[0037] (4) The Fe1Ni1-MOF obtained in step (3) was placed in a tubular furnace, nitrogen was passed through, and sodium hypophosphite was placed 3 cm upstream of the Fe1Ni1-MOF along the nitrogen flow direction. The nitrogen flow rate was 60 ml / min, and the reaction was constant temperature calcined at 350°C for 3 hours. After cooling to room temperature, the Ni2P / Fe3P electrocatalyst was obtained.

[0038] The molar ratio of nickel nitrate hexahydrate to ferric nitrate nonahydrate in step (1) is 1:1;

[0039] The concentration of nickel nitrate hexahydrate in the solution A of step (1) is 0.2 mol / L;

[0040] The concentration of terephthalic acid in the solution B in step (2) is 0.53 mol / L;

[0041] The volume ratio of solution A to solution B in step (3) is 1:1;

[0042] The volume of the reaction precursor solution in step (3) accounts for 70% of the volume of the autoclave;

[0043] The mass ratio of Fe1Ni1-MOF and sodium hypophosphite in step (4) is 1:5;

[0044] The heating rate of the tubular furnace in step (4) is 2°C / min, and the cooling rate is 2°C / min.

[0045] Test Case

[0046] The purity and morphology of the Fe1Ni1-MOF and Ni2P / Fe3P electrocatalysts prepared in Example 1 were determined by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HERTEM), and scanning electron microscopy (SEM) tests.

[0047] The electrocatalytic performance of the Fe1Ni1-MOF and Ni2P / Fe3P electrocatalysts prepared in Example 1 was determined by electrochemical performance testing, and the specific steps were as follows:

[0048] Preparation of working electrode: Cut the nickel sheet into a 2 cm × 3 cm rectangle. First, remove the surface oxide layer with a 2 mol / L hydrochloric acid solution. Then, ultrasonically wash the nickel sheet with deionized water and ethanol once, each for 30 minutes. After washing, place it in an oven to dry. At the same time, 0.04g Fe1Ni1-MOF electrocatalyst and 0.04g Ni2P / Fe3P electrocatalyst were taken, mixed with 2g carbon black respectively, and ground for 20min, then 0.005g polyvinylidene fluoride and 0.3g pyrrolidone were added respectively, and grinding was continued for 20min to obtain Fe1Ni1-MOF electrode slurry and Ni2P / Fe3P electrode slurry; the Fe1Ni1-MOF electrode slurry and Ni2P / Fe3P electrode slurry were uniformly coated on the washed and dried nickel sheet, the coated slurry mass was 0.1g, and the coated area was 0.5cm×0.5cm. After drying, the Fe1Ni1-MOF working electrode and Ni2P / Fe3P working electrode were obtained respectively.

[0049] Electrolyte: The electrolyte used in this experiment is a 1 mol / L potassium hydroxide aqueous solution.

[0050] After all preparations are completed, start the CHI 660D electrochemical workstation and connect the working electrode, counter electrode (carbon rod), and reference electrode (saturated calomel) to form a three-electrode system.

[0051] The test results are shown in the attached figure of the instruction manual.

[0052] Depend on Figure 1 It can be seen that the product prepared in Example 1 has the same XRD pattern as the simulated theoretical XRD pattern. Figure 1 As a result, the product prepared in Example 1 is a pure phase Fe1Ni1-MOF catalyst.

[0053] Depend on Figure 2 As can be seen, the interplanar spacing of the

[111] plane of Ni2P (PDF#03-0953) is 0.22nm, and the interplanar spacing of the

[301] plane of Fe3P (PDF#19-0617) is 0.251nm. Although the low crystallinity of the phosphide results in weak XRD peaks and its composition cannot be determined, HERTEM confirms that the phosphide product is Ni2P / Fe3P.

[0054] Depend on Figure 3 It can be seen that the Fe1Ni1-MOF and Ni2P / Fe3P electrocatalysts prepared in Example 1 have a nanorod-like structure with a length of 3-10 μm and a width of 0.5-1 μm.

[0055] Depend on Figure 5It can be seen that both Fe1Ni1-MOF and Ni2P / Fe3P electrocatalysts can be used in ampere-level industrial current working scenarios, and the catalytic performance of Ni2P / Fe3P electrocatalyst is better than that of Fe1Ni1-MOF electrocatalyst. -2 At a current density of 100 mA cm, the overpotential is 148.2 mV; at a current density of 100 mA cm -2 At a current density of 500 mA cm, the overpotential is 232.2 mV. -2 The overpotential at the current density of 10mAcm is 301.2mV; in the OER test, -2 At a current density of 100 mA cm, the overpotential is 242.8 mV; at a current density of 100 mA cm -2 At a current density of 500 mA cm, the overpotential is 303.8 mV. -2 The overpotential at the current density of 334.8mV is 334.8mV. The FeNiP composite obtained after phosphating has a HER of 10mAcm -2 At a current density of 100 mA cm, the overpotential is 118.2 mV. -2 At a current density of 500 mA cm, the overpotential is 206.2 mV; at a current density of 500 mA cm -2 The overpotential at a current density of 279.2mV is 279.2mV; at 1000mAcm -2 At a current density of 10 mA cm, the overpotential is 301.2 mV, and the OER -2 At a current density of 100 mA cm, the overpotential is 90.8 mV; at a current density of 100 mA cm -2 At a current density of 500 mA cm, the overpotential is 285.8 mV. -2 The overpotential at the current density of 1000 mA cm is 331.8 mV. -2 At a current density of 1.5 Å, the overpotential is 332.3 mV. It can be clearly shown that after phosphating Fe1Ni1-MOF, the overpotential obtained in both the HER process and the OER process is significantly reduced, indicating that its electrocatalytic performance is significantly improved.

[0056] Depend on Figure 6 It can be seen that the Ni2P / Fe3P electrocatalyst remains stable for a long time under the ampere-level industrial current scenario.

[0057] Depend on Figure 7 It can be seen that the Ni2P / Fe3P electrocatalyst presents a smaller semicircle in the low-frequency region compared with the Fe1Ni1-MOF electrocatalyst, which means a smaller charge transfer resistance (Rct). Therefore, the Ni2P / Fe3P electrocatalyst has better electrochemical performance.

[0058] Of course, the above description is only a specific embodiment of the present invention and is not intended to limit the scope of implementation of the present invention. Any equivalent changes or modifications made based on the structure, features and principles described in the scope of the patent application of the present invention should be included in the scope of the patent application of the present invention.

Claims

1. A simple preparation method of Ni2P / Fe3P electrocatalyst, characterized in that: The following steps are involved: (1) dissolving nickel nitrate hexahydrate and ferric nitrate nonahydrate in deionized water to obtain solution A; (2) dissolving terephthalic acid in N,N-dimethylformamide to obtain solution B; (3) Solution A and Solution B are mixed and stirred at a speed of 120-200 r / min for 20-60 min to obtain a reaction precursor solution; the reaction precursor solution is transferred to an autoclave and placed at 120-180° C. for reaction for 12-24 h. After naturally cooling to ambient temperature, the mixture is centrifuged, washed, and dried to obtain the product Fe1Ni1-MOF; (4) The Fe1Ni1-MOF obtained in step (3) was placed in a tubular furnace, nitrogen was passed through, and sodium hypophosphite was placed 1-10 cm upstream of the Fe1Ni1-MOF along the nitrogen flow direction. The nitrogen flow rate was 50-80 ml / min, and the reaction was constant temperature calcined at 350°C for 2-4 hours. After cooling to room temperature, the Ni2P / Fe3P electrocatalyst was obtained.

2. The simple preparation method of Ni2P / Fe3P electrocatalyst according to claim 1, characterized in that: The molar ratio of the nickel nitrate hexahydrate to the ferric nitrate nonahydrate in step (1) is 1:

1.

3. The simple preparation method of Ni2P / Fe3P electrocatalyst according to claim 1, characterized in that: The concentration of nickel nitrate hexahydrate in the solution A in step (1) is 0.2 mol / L.

4. The simple preparation method of Ni2P / Fe3P electrocatalyst according to claim 1, characterized in that: The concentration of terephthalic acid in the solution B in step (2) is 0.53 mol / L.

5. The simple preparation method of Ni2P / Fe3P electrocatalyst according to claim 1, characterized in that: The volume ratio of solution A and solution B in step (3) is 1:

1.

6. The simple preparation method of Ni2P / Fe3P electrocatalyst according to claim 1, characterized in that: The volume of the reaction precursor solution in step (3) accounts for 50-75% of the volume of the autoclave.

7. The simple preparation method of Ni2P / Fe3P electrocatalyst according to claim 1, characterized in that: The mass ratio of the Fe1Ni1-MOF and sodium hypophosphite in step (4) is 1:(5-15).

8. The simple preparation method of Ni2P / Fe3P electrocatalyst according to claim 1, characterized in that: The heating rate of the tubular furnace in step (4) is 1-2°C / min, and the cooling rate is 2-5°C / min.

9. A Ni2P / Fe3P electrocatalyst, characterized in that The Ni2P / Fe3P electrocatalyst is prepared by the simple preparation method of any one of claims 1 to 8.

10. Use of the Ni2P / Fe3P electrocatalyst according to claim 9 in the field of industrial hydrogen production.

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