阅读说明：本技术 泡沫镍负载镍铜锰金属纳米电催化剂及其制备方法 (Foam nickel loaded nickel-copper-manganese metal nano electro-catalyst and preparation method thereof ) 是由 王劲松 李智敏 徐明丽 张正富 辛思思 于 2021-11-03 设计创作，主要内容包括：本发明实施例公开了一种泡沫镍负载镍铜锰金属纳米电催化剂及其制备方法,该制备方法包括如下步骤：⑴对泡沫镍进行预处理,以去除其表面的镍氧化物；⑵将水溶性的锰盐、铜盐和镍盐按预定比例溶于去离子水中,得到前驱体溶液,并调节前驱体溶液的pH为酸性；⑶以预处理过的泡沫镍作为工作电极,在前驱体溶液中进行电沉积而在泡沫镍上负载镍铜锰金属纳米粒子；其中,沉积电位为-0.5～-1.2V。本发明通过掺杂催化惰性的金属Cu优化Ni活性位对*H的吸附能,同时加入电极电位远低于Ni和Cu的Mn元素,促进Ni/Ni(OH)-(2)结构形成,具有制备工艺简单、成本低、效率高的优点,且所制备的催化剂对碱性HER反应具有极佳的电催化性能。(The embodiment of the invention discloses a nickel foam loaded nickel-copper-manganese metal nano electro-catalyst and a preparation method thereof, wherein the preparation method comprises the following steps: pretreating foam nickel to remove nickel oxide on the surface of the foam nickel; dissolving water-soluble manganese salt, copper salt and nickel salt in deionized water according to a predetermined ratio to obtain a precursor solution, and adjusting the precursorThe pH of the bulk solution is acidic; thirdly, taking the pretreated foamed nickel as a working electrode, and carrying out electrodeposition in a precursor solution to load nickel-copper-manganese metal nanoparticles on the foamed nickel; wherein the deposition potential is-0.5 to-1.2V. The invention optimizes the adsorption energy of Ni active sites to H by doping metal Cu with catalytic inertness, and simultaneously adds Mn element with the electrode potential far lower than that of Ni and Cu to promote Ni/Ni (OH) 2 The structure is formed, the preparation method has the advantages of simple preparation process, low cost and high efficiency, and the prepared catalyst has excellent electrocatalytic performance on alkaline HER reaction.)

1. The preparation method of the nickel foam supported nickel-copper-manganese metal nano electro-catalyst comprises the following steps:

pretreating foam nickel to remove nickel oxide on the surface of the foam nickel;

dissolving water-soluble manganese salt, copper salt and nickel salt in deionized water according to a predetermined ratio to obtain a precursor solution, and adjusting the pH of the precursor solution to be acidic;

thirdly, taking the pretreated foamed nickel as a working electrode, and carrying out electrodeposition in the precursor solution to load nickel-copper-manganese metal nanoparticles on the foamed nickel; wherein the deposition potential of the electrodeposition is-0.5 to-1.2V.

2. The preparation method according to claim 1, wherein the pretreatment of step comprises sequentially performing acid washing, water washing and vacuum drying on the nickel foam.

3. The method according to claim 1, wherein the water-soluble manganese, copper and nickel salts are manganese, copper and nickel sulfates, respectively.

4. The preparation method according to claim 1, wherein the molar ratio of manganese, copper and nickel in the precursor solution is 0.9-1.8: 1.5-0.6: 4.

5. the preparation method according to claim 1, wherein the total molar concentration of manganese, copper and nickel in the precursor solution is 3-8 mol/L.

6. The method of claim 1, wherein ammonium sulfate is used as the pH regulator.

7. The preparation method according to claim 1, wherein the pH of the precursor solution is adjusted to 4-5.

8. The preparation method according to claim 1, wherein the electrodeposition time of step three is 300 to 1500 s.

9. The preparation method according to claim 1, wherein step three, electrodeposition is performed under a three-electrode system of: foamed nickel is used as a working electrode, saturated Ag/AgCl is used as a reference electrode, and a graphite rod is used as a counter electrode.

10. A nickel-on-foam nickel-copper-manganese metal nano electrocatalyst for alkaline HER reaction, obtained by the preparation method of any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of electrocatalysis; more particularly, relates to a non-noble metal nano electro-catalyst for hydrogen evolution reaction and a preparation method thereof.

Background

In recent years, hydrogen energy sources have received much attention due to high energy density and high cleanliness. In the existing hydrogen production technology, the hydrogen production by electrolyzing water can be the most developed potential, and because the hydrolysate is only oxygen and hydrogen, the environment is not polluted, and the hydrolysate can also be used as the raw material of a fuel cell, so that the water electrolysis can not only fundamentally reduce the problem of environment pollution, but also solve the energy crisis faced by human beings.

However, Hydrogen Evolution (HER) reactions on the cathode side of electrolyzed water require the provision of much higher than theoretical potentials to overcome reaction kinetic limitations (especially under alkaline conditions), thereby resulting in waste of electrical energy and lower energy conversion efficiency. At present, a relatively high-efficiency hydrogen evolution catalyst is a platinum-based noble metal catalyst, but due to scarcity and high cost, large-scale production cannot be realized. Meanwhile, the activity of the platinum-based catalyst in an alkaline environment is far lower than that in an acidic environment. Therefore, the search for hydrogen evolution reaction electrocatalysts which are abundant in the earth crust and still have high activity and durability in an alkaline environment is of great importance in the scalable application of water electrolysis.

The electrolysis of water to separate out hydrogen is divided into two steps, firstly, H in the electrolyte₂Dissociation of O molecule to form reaction intermediate adsorbed hydrogen (H) and adsorbing on the catalyst surface, and desorption of adsorbed hydrogen from the catalyst surface to form hydrogen (H)₂). Thus, the key to increasing alkaline HER activity is the simultaneous acceleration ofDissociation of water molecules and adsorption/desorption of H. There have been numerous studies and reports of basic HER electrocatalysts based on non-noble and non-metallic materials in which Ni can act as a site for H adsorption/desorption due to the adsorption energy of Ni to H of about-0.3 eV, while nickel hydroxide has excellent water dissociation ability, resulting from Ni and Ni (oh)₂The resulting multicomponent interfacial structure exhibits good basic HER activity and stability. However, prior art preparation of Ni/Ni (OH)₂The structure has the problems of complex process, high cost and low efficiency, and Ni/Ni (OH) is caused by strong adsorption energy of Ni to H₂Further improvement of the activity is required.

Disclosure of Invention

In view of the above defects or improvement needs of the prior art, the main object of the present invention is to provide a nickel foam supported nickel-copper-manganese metal nano electrocatalyst and a preparation method thereof, which not only has the advantages of simple process, low cost and high efficiency, but also has excellent electrocatalytic performance for HER reaction under alkaline conditions.

In order to achieve the above object, a first aspect of the present invention provides a method for preparing a nickel foam supported nickel-copper-manganese metal nano electrocatalyst, comprising the following steps:

pretreating foam nickel to remove nickel oxide on the surface of the foam nickel;

dissolving water-soluble manganese salt, copper salt and nickel salt in deionized water according to a predetermined ratio to obtain a precursor solution, and adjusting the pH of the precursor solution to acidity;

thirdly, taking the pretreated foamed nickel as a working electrode, and carrying out electrodeposition in a precursor solution to load nickel-copper-manganese metal nanoparticles on the foamed nickel; wherein the deposition potential of the electrodeposition is-0.5 to-1.2V.

The pretreatment comprises the steps of carrying out acid washing, water washing and vacuum drying on the foamed nickel in sequence. Wherein, hydrochloric acid, for example, hydrochloric acid with a concentration of 6mol/L, can be used for acid washing.

According to a specific embodiment of the present invention, the water-soluble manganese, copper and nickel salts are manganese, copper and nickel sulfate, respectively.

According to a specific embodiment of the invention, the molar ratio of manganese, copper and nickel in the precursor solution is 0.9-1.8: 1.5-0.6: 4.

according to a specific embodiment of the invention, the total molar concentration of manganese, copper and nickel in the precursor solution is 3-8 mol/L.

According to a specific embodiment of the invention, ammonium sulfate is used as the pH regulator.

According to the specific embodiment of the invention, the pH of the precursor solution is adjusted to be 4-5.

According to a specific embodiment of the invention, the electrodeposition time of step three is 300-1500 s.

In the preparation method, the adsorption energy of Ni active sites to H is optimized by doping metal Cu with catalytic inertness, and Mn element with the electrode potential far lower than that of Ni and Cu is added simultaneously to ensure that Mn exists in the form of hydroxide, so that the one-step synthesis of Ni/Ni (OH) is promoted₂The structure solves the technical problems of complex preparation process, high cost and low efficiency in the prior art, and the prepared catalyst has excellent hydrogen evolution catalytic performance even under alkaline conditions.

In order to achieve the above main object, a second aspect of the present invention provides a nickel foam supported nickel copper manganese metal nano electrocatalyst for alkaline HER reaction, which is obtained according to any one of the preparation methods described above.

The nickel-copper-manganese metal nano electro-catalyst loaded by the foamed nickel is prepared by a one-step electro-deposition technology, has the advantages of simple manufacturing process, low cost and high efficiency, and has excellent electro-catalytic activity and stability even under an alkaline condition.

To more clearly illustrate the objects, technical solutions and advantages of the present invention, the present invention will be further described in detail with reference to the accompanying drawings and detailed description.

Drawings

FIGS. 1a, 1b and 1c are Pourbaix diagrams for three metals, Ni, Cu and Mn, respectively;

FIG. 2 is an electrodeposition map of a NiCuMn catalyst prepared in example 1;

FIGS. 3a and 3b are schematic diagrams of a pretreated porous nickel foam and a NiCuMn catalyst prepared in example 1, respectively;

FIG. 4 is a FESEM and EDS spectra of NiCuMn catalyst prepared in example 1;

FIG. 5 is XRD patterns of a NiCuMn catalyst prepared in example 1 of the present invention, a Ni catalyst prepared in comparative example 1, a NiCu catalyst prepared in comparative example 2, and a NiMn catalyst prepared in comparative example 3;

FIG. 6 is a HAADF-STEM diagram of a NiCuMn catalyst prepared in example 1 of the present invention;

FIGS. 7a and 7b are Ni foil and Ni (OH) as reference samples, respectively₂And the NiCuMn catalyst obtained in example 1 of the present invention, the NiCu catalyst obtained in comparative example 2 and the NiMn catalyst obtained in comparative example 3, the XANES spectrum at Ni K side and the EXAFS data at Ni K side correspond to K³A weighted Fourier transform curve;

FIG. 8 is a spectrum of the valence band of the NiCuMn catalyst obtained in example 1, the Ni catalyst obtained in comparative example 1, and the NiCu catalyst obtained in comparative example 2;

FIG. 9 is a linear sweep voltammogram of the nickel copper manganese catalysts prepared in examples 1 to 5;

FIG. 10 is a plot of linear sweep voltammograms of the NiCuMn catalyst from example 1, the Ni catalyst from comparative example 1, the NiCu catalyst from comparative example 2, the NiMn catalyst from comparative example 3, and pretreated porous Nickel Foam (NF);

FIG. 11 is a graph of stability measurements of the NiCuMn catalyst prepared in example 1.

Detailed Description

The embodiment of the invention discloses a preparation method of a nickel foam loaded nickel-copper-manganese metal nano electro-catalyst, which comprises the following steps:

pretreating foam nickel to remove nickel oxide on the surface of the foam nickel; specifically, the foamed nickel with the size of 1cm x 1cm can be obtained by cutting, and then the cut foamed nickel is put into hydrochloric acid for ultrasonic cleaning to remove NiO on the surface of the foamed nickel_xLayer, then repeatedly cleaned with deionized waterWashing to remove residual acid on the surface, and finally vacuum drying for later use.

Dissolving water-soluble manganese salt, copper salt and nickel salt in deionized water according to a predetermined ratio to obtain a precursor solution, and adjusting the pH of the precursor solution to be acidic. The water-soluble manganese salt, copper salt and nickel salt can be manganese sulfate, copper sulfate and nickel sulfate, ammonium sulfate is used as a pH regulator, and the precursor solution is regulated to be weakly acidic, preferably 4-5. Wherein the molar ratio of manganese to copper to nickel in the precursor solution is preferably 0.9-1.8: 1.5-0.6: 4, the total molar concentration of manganese, copper and nickel is preferably 3-8 mol/L.

And thirdly, taking the pretreated foamed nickel as a working electrode, and carrying out constant potential deposition in the precursor solution to load the nickel-copper-manganese metal nanoparticles on the foamed nickel. Specifically, electrodeposition can be carried out under a three-electrode system as follows: foamed nickel is used as a working electrode, saturated Ag/AgCl is used as a reference electrode, and a graphite rod is used as a counter electrode. Wherein the deposition potential can be-0.5 to-1.2V, and the electrodeposition time can be 300 to 1500 s.

FIGS. 1a, 1b and 1c are Pourbaix diagrams of three metals, Ni, Cu and Mn, respectively, and it can be seen that nickel ions and copper ions can be reduced by providing a low voltage of less than-0.5V under acidic conditions, while manganese metal can be reduced by providing a high voltage of less than-1.2V. Therefore, it is reasonable to consider that in a mixed solution containing metal salts of Ni, Cu and Mn, elementary Ni and Cu are generated at a deposition potential of pH 4-5, -0.5-1.2V, and Mn exists in an ionic state. In the present invention, the potentials described are relative to the standard hydrogen electrode potential.

The embodiment of the invention adopts a simple one-step electrodeposition method, controls the deposition potential to be-0.5 to-1.2V, and enables the electrode potential of Ni with higher value to be acidic by adjusting the pH value of the electrolyte²⁺And Cu²⁺Ni and Cu are also in situ to form NiCu alloy, and the absorption/desorption of Ni to H is optimized; mn with lower electrode potential²⁺In the form of hydroxide, promoting Ni/Ni (OH)₂The structure is formed, thereby improving the catalytic performance of the catalyst.

Hereinafter, the present invention will be described in more detail based on specific examples and comparative examples.

Example 1

The preparation of the nickel foam supported nickel-copper-manganese metal nano electrocatalyst in the embodiment 1 comprises the following steps:

cutting foam nickel into the size of 1cm x 1cm, putting the foam nickel into hydrochloric acid with the concentration of 6mol/L for ultrasonic treatment for 10min, washing the foam nickel with deionized water for a plurality of times, and performing vacuum drying at 60 ℃ for 2 hours for later use. Among them, hydrochloric acid was used for removing oxide (NiO) on the surface_x) The repeated washing with deionized water is to remove residual hydrochloric acid on the foamed nickel.

1.2mmol of copper sulfate pentahydrate (CuSO)₄﹒5H₂O), 1.2mmol of manganese sulfate monohydrate (MnSO)₄﹒H₂O), 4mmol of nickel sulfate hexahydrate (NiSO)₄﹒6H₂O) and 2.6mmol ammonium sulfate ((NH)₄)₂SO₄) And dispersing the electrolyte into 100ml of deionized water, and carrying out ultrasonic treatment for 20 minutes to obtain the electrochemical deposition electrolyte with the pH value of 4-5, wherein the electrolyte is uniformly mixed. Wherein, the main function of the ammonium sulfate is to adjust the pH value of the solution, copper sulfate pentahydrate provides a copper source, manganese sulfate monohydrate provides a manganese source, and nickel sulfate hexahydrate provides a nickel source.

The three-electrode system is adopted, the foam nickel pretreated in the step serves as a working electrode, the graphite rod serves as a counter electrode, the saturated Ag/AgCl serves as a reference electrode, and the electrolyte is placed in the electrolyte in the step two, wherein the electrolyte is-200 mA cm^-2The current density of the catalyst is kept for 800 seconds, and the NiCuMn catalyst is obtained.

As shown in FIG. 2, the electrodeposition potential in example 1 was about-0.5 to-1V, and the deposition condition did not reach Mn²⁺Mn is present in the ionic state and Ni²⁺And Cu²⁺Has been reduced.

Examples 2 to 5

The preparation schemes of examples 2-5 are identical to the NiCuMn catalyst of example 1, except that the ratio of Cu and Mn is changed. Specifically, in examples 2-5, the molar weights of Cu and Mn were adjusted to 1.5mmol and 0.9mmol, 0.9mmol and 1.5mmol, 0.6mmol and 1.8mmol, and 0.3mmol and 2.1mmol, respectively, which are not described herein again.

Comparative examples 1 to 3

Comparative examples 1 to 3 are respectively: nickel metal nano catalyst (Ni) loaded on foamed nickel, nickel copper metal nano catalyst (NiCu) loaded on foamed nickel and nickel manganese metal nano catalyst (NiMn) loaded on foamed nickel.

The specific preparation steps of comparative examples 1 to 3 were the same as those of the NiCuMn catalyst of example 1, except that no copper source (CuSO) was added to the deposition solution in the preparation of the Ni catalyst₄﹒5H₂O) and a manganese source (MnSO)₄﹒H₂O), preparation of corresponding NiCu catalyst without adding manganese source (MnSO)₄﹒H₂O) and no copper source (CuSO) was added to the NiMn catalyst₄﹒5H₂O), which will not be described in detail herein.

Catalyst structure and morphology analysis

FIGS. 3a and 3b are schematic diagrams of pretreated porous nickel foam and the NiCuMn catalyst prepared in example 1, respectively, and comparing the two diagrams shows that a layer of very distinct black material is deposited on the porous nickel foam. Fig. 4 is a FESEM image of the NiCuMn catalyst prepared in example 1, and it can be seen that uniform spherical particles are loaded on the porous nickel foam, the particle size is about 200 nm, and the porous morphology not only provides abundant active sites, but also facilitates charge transport and evacuation of bubbles.

FIG. 5 is an XRD pattern of Ni, NiCu, NiMn, NiCuMn catalysts, from which it can be observed that both NiCu and NiCuMn catalysts exhibit a NiCu alloy diffraction peak at 43.9 °, and that the Ni diffraction peak is also shifted by a small angle in total compared to the Ni diffraction peak in the Ni catalyst, indicating that Cu forms a NiCu alloy with Ni after Cu is added; while the position of the diffraction peak is not changed by adding Mn, the obvious reduction of the intensity of the diffraction peak can be observed, and meanwhile, the NiMn alloy does not show an XRD diffraction peak, which indicates that Mn promotes the formation of an amorphous phase.

Further, it can be seen from the HAADF-STEM diagram (FIG. 6) of the NiCuMn catalyst that the crystalline phase Ni and the amorphous phase Ni (OH) are present in the sample₂；Ni/Ni(OH)₂The structure was further confirmed by synchrotron radiation absorption spectroscopy.

FIGS. 7a and 7b are Ni foil and Ni (OH) as reference samples, respectively₂And NiCu, NiMn and NiCuMn prepared by the inventionCatalyst, XANES spectra at Ni K edge and EXAFS data at Ni K edge corresponding to K³Weighted Fourier transform curves, from FIG. 7a it can be seen that the front line of the XANES spectrum of NiCu is located at 8335eV, close to the reference nickel foil (located at about 8336eV), NiMn is almost identical to Ni (OH) located at 8341eV₂Coincidently, NiCuMn is located at 8337eV between them, demonstrating that the predominant nickel phase of NiCu is metallic nickel, with nickel being present predominantly as hydroxide in NiMn and both divalent nickel (nickel hydroxide) and metallic nickel in NiCuMn; from the 7b plot, it can be seen that the Ni — Ni peak of NiCuMn shows slightly smaller R space than the Ni foil, indicating that one Ni atom is replaced by one Cu atom, resulting in lattice distortion.

Fig. 8 shows the valence band spectra of Ni, NiCu, and NiCuMn catalysts, and it can be seen that the d band center shifts significantly from the other catalysts after NiCu is alloyed, while the position of the d band center has been shown to be related to the adsorption of the H intermediates by the catalysts, and the shift indicates that the adsorption of the H intermediates is impaired, i.e. the adsorption/desorption of Ni to H is optimized after NiCu is alloyed.

Alkaline HER reaction electrocatalytic performance test

The electrocatalysis performance of the prepared catalyst in the embodiment 1 to 5 is tested by taking the prepared catalyst as a working electrode, a graphite rod as a counter electrode and saturated Ag/AgCl as a reference electrode under the conditions that the concentration of a KOH solution is 1mol/L and the scanning speed is 2 mV/s. As shown in fig. 9, it can be seen that the performance of the catalyst is gradually improved when the ratio of Cu is gradually increased, and the performance is deteriorated when the ratio of Mn is increased correspondingly. Wherein when the molar ratio of Ni, Cu and Mn is 0.9-1.8: 1.5-0.6: 4, the catalyst has better HER electrocatalytic activity; when the molar ratio of Mn, Cu and Ni is 1.2: 1.2: the electrocatalytic performance of the catalyst was best at 4 (example 1).

FIG. 10 is a Linear Sweep Voltammogram (LSV) of Ni, NiCu, NiMn, NiCuMn catalysts and pretreated porous Nickel Foam (NF) as seen at a current density of 10mA cm^-2Next, the NiCuMn catalyst prepared in example 1 has a very low overpotential of only 17mV, and the overpotential of commercial Pt/C is generally around 30mV based on previous research data, which shows that the catalyst prepared in example 1 has better performance than commercial Pt/C。

FIG. 11 is a stability test chart of NiCuMn catalyst, which tests 10, 50 and 100mA cm^-2The catalytic performance is almost kept stable with the extension of the test time, and it can be seen that the catalyst prepared in example 1 has excellent stability.

In conclusion, the nickel foam supported nickel-copper-manganese nano electrocatalyst has excellent catalytic activity and stability for HER reaction even under an alkaline environment. In addition, the nickel-copper-manganese nano electrocatalyst loaded on the foamed nickel can be prepared by a one-step electrodeposition method, and has the advantages of simple preparation process, low cost and high efficiency.

Although the invention has been described with reference to specific embodiments, it will be appreciated by those skilled in the art that equivalent variations may be made without departing from the scope of the invention, which is intended to be covered by the appended claims.