Synthesis of an in-situ grown amorphous NiO-coated PtNi three-dimensional network structure and its application in electrocatalytic hydrogen production from seawater

Abstract

The present invention belongs to the technical field of electrolysis of water for hydrogen production, and specifically relates to the synthesis of an in-situ grown amorphous NiO-coated PtNi three-dimensional network structure and its application in electrocatalytic seawater hydrogen production. The present invention first prepares a PtNi three-dimensional network structure by a simple room temperature reduction method, and then in-situ grows a layer of amorphous NiO on the metal surface of the three-dimensional network structure by an air calcination method to obtain an in-situ grown amorphous NiO-coated PtNi three-dimensional network structure. Compared with the simple composite of PtNi and NiO, this in-situ generated amorphous NiO can be firmly coated on the PtNi surface, and thus can resist the corrosion of chloride ions in seawater, improve the stability of the material, promote the water dissociation step during the electrolysis of seawater, and accelerate the hydrogen evolution reaction. Therefore, the PtNi / NiO composite material prepared by the method of the present invention can greatly improve the material's electrolysis of seawater for hydrogen evolution performance, and is expected to be applied to industrial large-scale electrolysis of seawater for hydrogen production.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen production by electrolysis of water, and specifically relates to the synthesis of an in-situ grown amorphous NiO-coated PtNi three-dimensional network structure and its application in electrocatalytic seawater hydrogen production. Background Art

[0002] As a clean energy source, hydrogen produces only water when burned and does not emit any greenhouse gases. It has high energy density and is widely available. It is considered an important component of the future sustainable energy system. Electrolysis of seawater to produce hydrogen is considered an ideal method for hydrogen production. This is because the electrolysis of fresh water requires a high-quality water source, which may increase competition for already scarce fresh water resources. The use of seawater can reduce the demand for fresh water resources; moreover, seawater is an almost inexhaustible source of water. However, seawater contains a large amount of salt and other chemicals, which can corrode metal electrode materials, reduce the service life of equipment, and increase maintenance costs. Therefore, the development of efficient and stable metal electrode materials is crucial.

[0003] Platinum (Pt)-based nanomaterials are recognized as the most efficient catalysts for the cathode hydrogen evolution reaction (HER) in water electrolysis. Developing three-dimensional network structures is considered one of the methods to construct high-performance Pt-based nanomaterials. This is because the three-dimensional pore structure is conducive to the transport of substances in the catalytic reaction and accelerates the electrode reaction. However, the low stability of Pt-based nanomaterials is a problem that restricts their widespread application. The combination of NiO and Pt-based nanoalloys can effectively improve the seawater HER performance of the material. This is because, on the one hand, NiO itself is also an efficient HER catalyst because it can accelerate the dissociation of water molecules and increase the kinetics of hydrogen production; on the other hand, NiO can directionally transfer electrons to the Pt-based alloy, increasing the negative charge of the Pt surface, which is used to resist the negative Cl that is widely present in seawater. - It can be seen that the development of NiO / Pt-based three-dimensional network structure nanocomposites can effectively improve the seawater hydrogen production performance of the material.

[0004] However, conventional simple compounding of NiO and Pt-based alloys (e.g., mechanical stirring) has the following problems. First, simple compounding results in weak bonding between NiO and Pt-based alloys, which easily peels off and falls off during catalytic reactions, resulting in a decrease in catalyst performance. Second, conventional simple compounding can only ensure "point-to-point" contact between the two materials, and NiO cannot effectively wrap the Pt-based material, making it difficult to form a comprehensive and effective protection against Cl - Therefore, a new composite method of Pt-based materials and NiO is urgently needed to improve the seawater hydrogen production performance of Pt-based materials. Summary of the Invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the present invention provides a method for in situ growth of amorphous NiO on the surface of a PtNi three-dimensional network structure, and utilizes NiO to coat the PtNi three-dimensional network structure to achieve comprehensive and effective coating of Pt-based nanomaterials, thereby enabling the Pt-based nanomaterials to effectively resist seawater corrosion, improve their performance in hydrogen production by electrolysis of seawater, and ultimately achieve the purpose of efficient and stable hydrogen evolution by electrolysis of seawater.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A first aspect of the present invention provides a method for in-situ growth of an amorphous NiO-coated PtNi three-dimensional network structure, the method comprising the following steps:

[0008] S1. Add chloroplatinic acid, nickel chloride, potassium bromide and polyvinyl pyrrolidone into water, stir, and then dropwise add sodium borohydride. After the reaction, centrifuge, wash and dry to obtain a PtNi three-dimensional network structure;

[0009] S2. The PtNi three-dimensional network structure obtained in step S1 is placed in an air atmosphere for high-temperature calcination reaction, and amorphous NiO is in situ grown on the surface of the PtNi three-dimensional network structure, thereby obtaining an in-situ grown amorphous NiO-coated PtNi three-dimensional network structure.

[0010] The present invention first prepares a PtNi three-dimensional network structure by a simple room temperature reduction method, and then in situ grows a layer of amorphous NiO on the metal surface of the three-dimensional network structure by an air calcination method to prepare an in-situ grown amorphous NiO-coated PtNi three-dimensional network structure. The obtained material has a PtNi alloy structure, a three-dimensional network morphology and in-situ amorphous NiO coating characteristics.

[0011] Preferably, in step S1, the molar ratio of chloroplatinic acid, nickel chloride and potassium bromide is 1:(0.2-5):(20-200), and the concentration of chloroplatinic acid in water is 0.05-0.20 mmol / 30 mL.

[0012] Preferably, in step S1, the ratio of polyvinyl pyrrolidone to water is 20-200 mg / 30 mL.

[0013] Preferably, in step S1, the sodium borohydride is prepared into a solution before being added dropwise, and the concentration of the sodium borohydride solution is 0.5 to 5 mg·mL -1 The dosage ratio of the sodium borohydride solution to water is 10-50 mg / 30 mL.

[0014] 5. The method for in-situ growth of an amorphous NiO-coated PtNi three-dimensional network structure according to claim 1, characterized in that in step S1, sodium borohydride is added dropwise for 20-40 minutes based on 30 mL of water.

[0015] Preferably, in step S2, the temperature of the high temperature calcination reaction is 200-500°C, the time is 1-5 hours, and the heating rate is 2-4°C·min -1 .

[0016] The second aspect of the present invention provides an in-situ grown amorphous NiO-coated PtNi three-dimensional network structure prepared by the method described in the first aspect.

[0017] The third aspect of the present invention provides the application of the in-situ grown amorphous NiO-coated PtNi three-dimensional network structure described in the second aspect in electrocatalytic seawater hydrogen production.

[0018] Research has found that compared with the simple composite of PtNi and NiO, the amorphous NiO generated in situ in the present invention can be firmly coated on the PtNi surface, thereby being able to resist the corrosion of chloride ions in seawater, improve the stability of the material, and promote the water dissociation step during seawater electrolysis, accelerating the hydrogen evolution reaction. Therefore, the preparation of PtNi / NiO composite materials by the method of the present invention can greatly improve the material's hydrogen evolution performance in seawater electrolysis, and is expected to be applied to industrial large-scale seawater electrolysis for hydrogen production.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention discloses a method for in-situ growth of amorphous NiO coating a PtNi three-dimensional network structure. First, a PtNi three-dimensional network structure is prepared by a simple room temperature reduction method. The rich three-dimensional pore structure of the structure is conducive to efficient material transport during the catalytic reaction process. Then, amorphous NiO is in-situ grown on the surface of the PtNi three-dimensional network structure by air calcination. This method of in-situ growth of amorphous NiO on the surface of a Pt-based material has the following advantages: (1) amorphous NiO has better coating ability and corrosion resistance than crystalline NiO, which can effectively improve the stability of the Pt-based material; (2) the in-situ grown NiO can fully and effectively coat the PtNi, effectively resisting Cl in seawater - (3) This in-situ growth method allows PtNi and NiO to be chemically bonded, resulting in a strong and reliable bond that is not easily peeled off or detached during the catalytic reaction. Therefore, the in-situ growth of amorphous NiO on the surface of the PtNi three-dimensional network structure can significantly improve the material's performance in hydrogen evolution from seawater electrolysis, and is expected to be applied to industrial large-scale hydrogen production from seawater electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a scanning electron microscope image of the in-situ grown amorphous NiO-coated PtNi three-dimensional network structure;

[0022] Figure 2 Transmission electron microscopy image of in-situ grown amorphous NiO-coated PtNi three-dimensional network structure;

[0023] Figure 3 This is the energy spectrum scanning of the in-situ grown amorphous NiO-coated PtNi three-dimensional network structure;

[0024] Figure 4 X-ray diffraction patterns of in-situ grown amorphous NiO coated PtNi three-dimensional network structure, PtNi three-dimensional network structure and PtNi three-dimensional network structure mechanically composited with NiO;

[0025] Figure 5 Activity diagrams for hydrogen production from seawater electrolysis using in-situ grown amorphous NiO-coated PtNi three-dimensional network structure, PtNi three-dimensional network structure, PtNi three-dimensional network structure mechanically composited with NiO and commercial Pt / C catalysts;

[0026] Figure 6 Stability diagram of hydrogen production from seawater using in situ grown amorphous NiO coated PtNi three-dimensional network structure, PtNi three-dimensional network structure, PtNi three-dimensional network structure mechanically composited with NiO and commercial Pt / C catalyst. DETAILED DESCRIPTION

[0027] The following is a further description of specific embodiments of the present invention. It should be noted that the description of these embodiments is intended to facilitate understanding of the present invention and does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0028] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0029] Example: Preparation of in-situ grown amorphous NiO-coated PtNi three-dimensional network structure

[0030] (1) Preparation of PtNi three-dimensional network structure: 0.4 mL of chloroplatinic acid solution (0.2 mol·L -1 )、0.2mL nickel chloride solution (0.2mol·L -1 ), 3mL potassium bromide solution (2.5mol·L -1) and 120 mg of polyvinyl pyrrolidone (molecular weight K30) were added to 30 mL of deionized water and stirred for 30 minutes. Then, 36 mL of sodium borohydride solution (2 mg mL -1 ), the addition time is 20 minutes, and the sample is immediately centrifuged at a speed of 10,000 rpm for 10 minutes after the addition is completed. After removing the supernatant, the solid product is washed with deionized water. The centrifugation and washing process are repeated 5 times, and finally the PtNi three-dimensional network structure (abbreviated as PtNi) is obtained by drying at 60°C.

[0031] (2) Calcination: The PtNi three-dimensional network structure (50 mg) obtained in step (1) was placed in a corundum boat, and the corundum boat was placed in a tube furnace. The tube furnace was then heated from room temperature to 300 °C at a heating rate of 3 °C min -1 , and maintained at 300℃ for 2h in air atmosphere to obtain an in-situ grown amorphous NiO-coated PtNi three-dimensional network structure (abbreviated as PtNi@NiO).

[0032] Comparative Example: Preparation of PtNi three-dimensional network structure mechanically composited NiO

[0033] 0.1 g of the PtNi three-dimensional network structure synthesized in step (1) of the embodiment and 0.1 g of commercial NiO powder were dispersed in 20 mL of deionized water, stirred for 2 h, and then centrifuged to obtain a PtNi three-dimensional network structure mechanical composite NiO (abbreviated as PtNi / NiO).

[0034] Experimental example: Characterization and water electrolysis hydrogen production performance test

[0035] (1) Morphological characterization of PtNi@NiO materials

[0036] The PtNi@NiO prepared in the example was observed using a scanning electron microscope (HITACHI S-4800). Figure 1 As shown, it can be seen that the synthesized material exhibits a clear three-dimensional network structure, and the gaps between the materials are clearly visible. At the same time, the PtNi@NiO prepared in the embodiment was observed using a transmission electron microscope (FEI Talos). The transmission electron microscope image is shown in FIG. Figure 2 As shown, it can be seen that the material exhibits two distinct contrasts ( Figure 2 a), where the PtNi alloy has a darker contrast and exhibits a three-dimensional network structure composed of nanoparticles. The Fourier transform results show that it has a distinct crystal structure, corresponding to the (111) crystal plane of the PtNi alloy ( Figure 2 b area i); the area with lighter contrast is amorphous NiO, showing a film-like structure. The Fourier transform results show that it has an obvious amorphous structure ( Figure 2b region ii). Therefore, the scanning electron microscopy and transmission electron microscopy results demonstrate that the PtNi@NiO material synthesized in the embodiment has a three-dimensional network structure and an amorphous NiO-coated PtNi alloy structure.

[0037] (2) Characterization of element distribution of PtNi@NiO materials

[0038] The element distribution of PtNi@NiO prepared in the embodiment was analyzed by X-ray energy spectrometer. Figure 3 a is the scanning transmission electron microscopy image of PtNi@NiO, from which the element distribution map of Pt, Ni, and O is obtained. Figure 3 b and c are the element distributions of Pt and Ni, respectively. It can be seen that Pt and Ni elements are evenly distributed on the surface of the three-dimensional network structure, proving the PtNi alloy characteristics of the three-dimensional network structure; the distribution range of Ni element is wider than that of Pt element, proving that Ni still exists outside the three-dimensional network structure of PtNi alloy. Figure 3 d is the elemental distribution of O, which shows that the O element is not only distributed on the three-dimensional network structure, but also widely distributed outside the three-dimensional network structure. Combined with the elemental distribution of Ni and O, it can be concluded that NiO uniformly covers the outside of the three-dimensional network structure of the PtNi alloy, proving that the in-situ grown amorphous NiO can firmly wrap the PtNi alloy.

[0039] (3) X-ray diffraction characterization of NiO and PtNi composite materials

[0040] The PtNi@NiO, PtNi and PtNi / NiO prepared in the example were analyzed by X-ray diffraction analysis using a Bruker D8 Advance. Figure 4 As shown, it can be seen that the X-ray diffraction peaks of PtNi@NiO, PtNi and PtNi / NiO are between Pt (PDF card number: 04-0802) and Ni (PDF card number: 04-0850), proving that all three materials have PtNi alloy characteristics. Among them, PtNi / NiO has additional diffraction peaks at 37.2, 43.3, 62.9, 75.4 and 79.4°, corresponding to crystalline NiO (PDF card number: 47-1049), proving the composite characteristics of PtNi and NiO in this material. However, there is no obvious NiO phase in the diffraction peak of PtNi@NiO, proving that the NiO generated after calcination is an amorphous structure. At the same time, the diffraction peak of PtNi@NiO has a significant high-angle shift feature compared to the diffraction peaks of PtNi and PtNi / NiO, indicating that NiO is incorporated into the PtNi lattice, causing the lattice parameter of the PtNi alloy to increase.

[0041] (4) Performance test of NiO and PtNi composite materials catalyzing hydrogen production from seawater

[0042] The PtNi@NiO prepared in the embodiment was used to test the catalytic performance of seawater electrolysis, and PtNi, PtNi / NiO and commercial Pt / C catalysts (Shanghai Hesen Electric Co., Ltd., with a Pt content of 20wt%) were used as comparison samples. The model of the electrochemical workstation used for the electrochemical test is Autolab AUT88171, and the electrochemical test adopts a three-electrode system, in which the working electrode is a rotating disk electrode coated with a catalyst, the reference electrode is an Ag / AgCl electrode, the counter electrode is a carbon rod, and the electrolyte is alkaline seawater (1MKOH+seawater). The seawater was taken from the waters of Zhuhai City, China (113.60° east longitude, 22.34° north latitude); the seawater hydrogen production test used linear sweep voltammetry, the potential range was set to -1.023~-1.323V, the scan rate was 5mV / s, and the rotating disk electrode speed was 1600rpm. The potential in the polarization curve diagram was converted from the Ag / AgCl electrode to the standard hydrogen electrode E RHE , the conversion relationship is: E RHE =(E Ag / AgCl +0.197+0.059pH)V.

[0043] Linear sweep voltammetry LSV curves of PtNi@NiO, NiO, PtNi / NiO and commercial Pt / C catalysts are shown in Figure 2. Figure 5 As shown in a. As can be seen from the figure, with the increase of potential, PtNi@NiO always shows a current density greater than that of PtNi, PtNi / NiO and commercial Pt / C catalysts, proving that the hydrogen evolution reaction activity of PtNi@NiO in alkaline seawater is higher than that of PtNi, PtNi / NiO and commercial Pt / C. The overpotentials of PtNi@NiO, PtNi, PtNi / NiO and commercial Pt / C catalysts are shown in Figure 5 As shown in b, it can be seen that PtNi@NiO only needs an overpotential of 43mV to drive 10mA·cm -2 The current density is much lower than that of PtNi (104mV), PtNi / NiO (72mV) and commercial Pt / C (130mV). These results show that PtNi@NiO has better performance in hydrogen evolution in seawater electrolysis than PtNi, PtNi / NiO and commercial Pt / C catalysts.

[0044] In addition, the time of the catalytic performance test of seawater electrolysis was gradually increased to characterize the catalyst stability of the NiO and PtNi composite materials. The electrocatalytic stability curves of PtNi@NiO, NiO, PtNi / NiO and commercial Pt / C catalysts in alkaline seawater are shown in Figure 2. Figure 6As shown in the figure, with the increase of reaction time, PtNi@NiO exhibits excellent stability, and its current density is always higher than that of NiO, PtNi / NiO and commercial Pt / C catalysts, proving that the in situ grown NiO can effectively resist chloride ions in seawater and enhance the catalytic stability of the material.

[0045] In summary, compared with the simple composite of PtNi and NiO, the amorphous NiO generated in situ in the present invention can be firmly coated on the surface of PtNi, thereby being able to resist the corrosion of chloride ions in seawater, improve the stability of the material, and promote the water dissociation step during the electrolysis of seawater, thereby accelerating the hydrogen evolution reaction. Therefore, the preparation of the PtNi / NiO composite material by the method of the present invention can greatly improve the hydrogen evolution performance of the material in the electrolysis of seawater, and is expected to be applied to industrial large-scale electrolysis of seawater for hydrogen production.

[0046] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations of these embodiments may be made without departing from the principles and spirit of the present invention, and the changes still fall within the scope of protection of the present invention.

Claims

1. A method for in-situ growth of an amorphous NiO-coated PtNi three-dimensional network structure, characterized in that: The following steps are involved: S1. Add chloroplatinic acid, nickel chloride, potassium bromide and polyvinyl pyrrolidone into water, stir, and then dropwise add sodium borohydride. After the reaction, centrifuge, wash and dry to obtain a PtNi three-dimensional network structure. S2. The PtNi three-dimensional network structure obtained in step S1 is placed in an air atmosphere for high-temperature calcination reaction, and amorphous NiO is in situ grown on the surface of the PtNi three-dimensional network structure, thereby obtaining an in-situ grown amorphous NiO-coated PtNi three-dimensional network structure.

2. The method for in-situ growth of an amorphous NiO-coated PtNi three-dimensional network structure according to claim 1, characterized in that: In step S1, the molar ratio of the chloroplatinic acid, nickel chloride and potassium bromide is 1:(0.2-5):(20-200), and the concentration of the chloroplatinic acid in water is 0.05-0.20 mmol / 30 mL.

3. The method for in-situ growth of an amorphous NiO-coated PtNi three-dimensional network structure according to claim 1, characterized in that: In step S1, the dosage ratio of polyvinyl pyrrolidone to water is 20-200 mg / 30 mL.

4. The method for in-situ growth of an amorphous NiO-coated PtNi three-dimensional network structure according to claim 1, characterized in that: In step S1, the sodium borohydride solution is prepared before being added dropwise. The concentration of the sodium borohydride solution is 0.5 to 5 mg mL -1 The dosage ratio of the sodium borohydride solution to water is 10-50 mg / 30 mL.

5. The method for in-situ growth of an amorphous NiO-coated PtNi three-dimensional network structure according to claim 1, characterized in that: In step S1, sodium borohydride is added dropwise to 30 mL of water for 20-40 minutes.

6. The method for in-situ growth of an amorphous NiO-coated PtNi three-dimensional network structure according to claim 1, characterized in that: In step S2, the high temperature calcination reaction temperature is 200-500°C, the time is 1-5h, and the heating rate is 2-4°C·min -1 .

7. An in-situ grown amorphous NiO-coated PtNi three-dimensional network structure prepared by the method according to any one of claims 1 to 6.

8. Use of the in-situ grown amorphous NiO-coated PtNi three-dimensional network structure according to claim 7 in electrocatalytic hydrogen production from seawater.

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