Foamed nickel supported bimetallic phosphide / sulfide heterostructure hydrogen evolution catalyst and preparation method thereof

Abstract

The application discloses a foam nickel loaded bimetallic phosphide / sulfide heterostructure hydrogen evolution catalyst and a preparation method thereof. Different from a preparation method of a general high-temperature phosphorization or sulfuration treatment corresponding precursor, the application adopts a mild and simple two-step electrodeposition method, taking nickel salt and cobalt salt as metal sources, taking thiourea as a sulfur source, and taking sodium hypophosphite as a phosphorus source. First, foam nickel with good conductivity is selected as a substrate, and nickel cobalt sulfide nanosheet arrays are directly grown on the foam nickel through cyclic voltammetry electrodeposition; then, nickel cobalt phosphorus nanoparticles are in-situ coated on the surface of the nickel cobalt sulfide nanosheet to obtain an electrocatalytic hydrogen evolution catalyst with a layered heterostructure. The catalyst prepared by the method has low cost, and also exhibits excellent alkaline electrocatalytic hydrogen evolution performance under a large current density, and has great potential in actual large-scale hydrogen production.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis catalyst technology, specifically relating to a nickel foam-supported bimetallic phosphide / sulfide heterostructure hydrogen evolution catalyst and its preparation method. Background Technology

[0002] With the increasing depletion of traditional fossil fuels (oil, coal, etc.) and the growing environmental problems caused by their use, the development of new sustainable energy sources is imperative. Hydrogen, as a clean and sustainable energy carrier, boasts advantages such as high energy density, pollution-free combustion products, and abundant raw materials, and is widely considered one of the most promising alternative energy sources. Among numerous hydrogen production methods, electrocatalytic water splitting technology driven by renewable energy sources (such as solar or wind power) is considered a very promising approach because it produces high-purity hydrogen, uses only water as a raw material, and the process is pollution-free. The hydrogen evolution reaction (HER) is the cathode half-reaction of the water splitting reaction. To achieve large-scale industrial hydrogen production, HER requires highly efficient catalysts to achieve rapid reaction kinetics (especially under alkaline conditions), thereby reducing energy consumption. To date, Pt group noble metals remain the most active electrocatalysts for HER. However, their limited reserves and high prices significantly restrict their large-scale application. Therefore, developing efficient and low-cost non-noble metal-based electrocatalysts is crucial.

[0003] In recent years, 3d transition metal compounds (TMCs), including transition metal oxides, carbides, sulfides, phosphides, and selenides, have been extensively designed, with some catalysts exhibiting hydrogen evolution performance even superior to noble metals. Among them, transition metal sulfides and phosphides have shown high electrocatalytic activity due to their tunable electronic structure and high conductivity, attracting considerable research attention. Furthermore, due to the synergistic effect of bimetallic ions, bimetallic compounds exhibit better intrinsic electrocatalytic activity and structural stability compared to monometallic catalysts.

[0004] At the same time, although at small current densities such as 10 mA cm⁻¹ -2 Significant progress has been made, but in high-current-density applications such as alkaline electrolyzers, current densities typically exceeding 200 mA / cm² are required. -2 The performance of these catalysts is not outstanding, which is crucial for practical industrial applications. For industrial applications, high current density means high hydrogen production rates, ensuring the economic viability of hydrogen production. To date, most reported transition metal-based catalysts, even Pt, still fail to meet practical requirements in terms of catalytic activity and stability at high current densities. This is because electrode polarization is severe at high current densities, and the mechanical and chemical stability of the electrode material deteriorates under intense electrochemical reaction conditions.

[0005] Studies have shown that constructing heterostructures with interfacial interactions can effectively increase active sites, accelerate electron transport and hydrogen evolution reaction kinetics, regulate the adsorption free energy of hydrogen ions, inhibit material aggregation, and facilitate the release of bubbles. This is one of the effective strategies for adjusting catalyst performance under high current densities. Summary of the Invention

[0006] Based on the above background, the purpose of this invention is to provide a nickel foam-supported bimetallic phosphide / sulfide heterostructure hydrogen evolution catalyst and its preparation method. It not only has the advantages of simple preparation method, low cost, and direct construction of self-supporting electrode, but also has excellent electrocatalytic hydrogen evolution performance under alkaline high current conditions.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a nickel foam-supported bimetallic phosphide / sulfide heterostructure hydrogen evolution catalyst includes the following steps:

[0009] (1) The nickel foam was ultrasonically cleaned and then vacuum dried to remove the oxides on its surface;

[0010] (2) Add a pre-prepared electrolyte containing NiCl2, CoCl2 and CH4N2S to an electrolytic cell. Use nickel foam, platinum sheet and saturated calomel electrode as working electrode, counter electrode and reference electrode respectively. Electrodeposition is carried out by cyclic voltammetric electrodeposition under stirring. The obtained electrodes are washed with deionized water and ethanol respectively and vacuum dried to obtain nickel foam supported nickel cobalt sulfide nanosheet array.

[0011] (3) Add a pre-prepared electrolyte containing CoCl2, NiCl2, C6H5Na3O7 and NaH2PO2 to the electrolytic cell. Use the nickel foam supported nickel cobalt sulfide nanosheet array obtained in step (2) as the working electrode, and the graphite rod and Ag / AgCl electrode as the counter electrode and reference electrode, respectively. Electrodeposit phosphide by chronoamperometry under stirring. Wash the obtained electrodes with deionized water and ethanol, and vacuum dry them to obtain the nickel foam supported bimetallic phosphide / sulfide heterostructure hydrogen evolution catalyst.

[0012] As a preferred embodiment of the present invention, in step (1), the nickel foam is ultrasonically cleaned for 10-20 minutes in acetone, hydrochloric acid solution with a concentration of 2-4M, anhydrous ethanol and deionized water, respectively.

[0013] The electrodeposition conditions in step (2) are as follows: magnetic stirring at a speed of 200-400 rpm; voltage range of –1.3 to 0.3 V; and electrodeposition scan rate of 5 mV / s. -1 The scanning cycle count is 4.

[0014] Furthermore, the electrodeposition conditions in step (3) are as follows: the stirring is magnetic stirring, the stirring speed is 200-400 rpm; the deposition potential is -1.2V, and the deposition time is 10-30 minutes.

[0015] Furthermore, in step (2), the electrolyte is a solution containing 0.05M NiCl2, 0.125M CoCl2 and 0.25-1M CH4N2S.

[0016] Furthermore, in step (3), the electrolyte is a solution containing 55mM CoCl2, 33mM NiCl2, 20mM C6H5Na3O7 and 0.2M NaH2PO2.

[0017] Furthermore, in steps (1), (2), and (3), the vacuum drying temperature is 40-60℃ and the drying time is 4-6 hours.

[0018] As a preferred embodiment of the present invention, the preparation method of the present invention provides a nickel foam supported bimetallic phosphide / sulfide heterostructure hydrogen evolution catalyst, wherein the bimetallic compounds are nickel and cobalt.

[0019] As a preferred embodiment of the present invention, the application of the nickel foam-supported bimetallic phosphide / sulfide heterostructure catalyst in the electrocatalytic hydrogen evolution reaction is described.

[0020] This invention employs two different electrodeposition methods to combine nickel-cobalt sulfides and nickel-cobalt phosphides to grow catalysts in situ on a nickel foam substrate, achieving controllable hierarchical heterogeneous structures and morphologies. The synergistic effect of combining sulfides and phosphides with different properties helps improve the electrocatalytic hydrogen evolution performance.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The catalyst prepared by the present invention is a non-precious metal catalyst, and the transition metal materials required in the preparation process are easy to obtain and have low cost.

[0023] (2) The present invention adopts a simple and mild two-step electrodeposition method. First, a layer of nickel cobalt sulfide nanosheet array is directly grown on the nickel foam substrate, and then a layer of nickel cobalt phosphide nanoparticles is coated. This layered heterostructure can not only increase the specific surface area and provide sufficient mass transfer channels, but also improve the mechanical stability of the electrode to withstand bubble disturbance under high current density. The preparation conditions are mild, do not require high temperature and high pressure, and are short in time.

[0024] (3) The present invention uses nickel foam as a substrate growth catalyst to directly construct a self-supporting electrode without the need for additional binders, and has better mechanical stability.

[0025] (4) The 3D hierarchical heterostructure exposes abundant active sites, the interface effect realizes the adjustment of electronic structure and the increase of conductivity, and the synergistic effect between the two components optimizes the hydrogen adsorption free energy, thereby improving the electrocatalytic performance.

[0026] (5) The catalyst prepared in this invention exhibits high activity and long-term stability in alkaline electroelectrolysis, especially at high current densities such as 500 mA cm⁻¹. -2 It still exhibits high hydrogen evolution performance, which is superior to most current catalysts. Attached Figure Description

[0027] To more clearly explain the features, objectives, and advantages of the present invention, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0028] Figure 1 Physical images of pretreated nickel foam and samples prepared in Examples 1 and 3.

[0029] Figure 2 Scanning electron microscope (SEM) images of pretreated nickel foam and samples prepared in Examples 1, 3, and 4.

[0030] Figure 3 High-magnification scanning electron microscope images of the samples prepared in Examples 1, 3 and 4.

[0031] Figure 4 The XPS spectrum of the sample prepared in Example 1 is shown.

[0032] Figure 5 This is a high-magnification spectrum of the sample prepared in Example 1.

[0033] Figure 6 The graph shows the hydrogen evolution polarization curves and overpotential values ​​at different current densities of the samples prepared in Examples 1-3 in 1M KOH solution, with nickel foam and commercial Pt / C supported nickel foam serving as comparative samples.

[0034] Figure 7 This is a stability test curve of Example 1 in 1M KOH solution. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. The embodiments described are exemplary, but not all of them, and the scope of protection of the present invention is not limited thereto.

[0036] Example 1

[0037] (1) Cut the nickel foam into small pieces of 1cm*2cm and then place them in acetone, 3M hydrochloric acid solution, anhydrous ethanol and deionized water for ultrasonic cleaning for 15 minutes. Then, vacuum dry at 40℃ for 6 hours to remove the oxides on its surface.

[0038] (2) Weigh NiCl2·6H2O, CoCl2·6H2O, and CH4N2S to prepare an electrolyte containing 0.05M NiCl2, 0.125M CoCl2, and 0.5M CH4N2S; add the prepared electrolyte to the electrolytic cell; use nickel foam, platinum sheet, and saturated calomel electrode as the working electrode, counter electrode, and reference electrode, respectively; perform electrodeposition using cyclic voltammetry (CV) electrodeposition with magnetic stirring at 400 rpm, the voltage range being –1.3–0.3V, and a 5mV s⁻¹ interval. -1 The scanning cycle was repeated 4 times at a certain speed. The resulting electrodes were rinsed and washed with deionized water and ethanol, respectively, and then vacuum dried at 40°C for 6 hours to obtain a nickel foam-supported nickel-cobalt sulfide nanosheet array with a loading area of ​​1 cm². 2 ;

[0039] (3) Weigh CoCl2·6H2O, NiCl2·6H2O, C6H5Na3O7·2H2O and NaH2PO2 to prepare an electrolyte containing 55 mM CoCl2, 33 mM NiCl2, 20 mM C6H5Na3O7 and 0.2 M NaH2PO2. Add the prepared electrolyte to the electrolytic cell. Use the nickel foam supported sample obtained in step (2) as the working electrode, and the graphite rod and Ag / AgCl electrode as the counter electrode and reference electrode, respectively. Electrodeposit nickel cobalt phosphide by chronoamperometry under magnetic stirring at 400 rpm. Wash the obtained electrodes with deionized water and ethanol, and vacuum dry at 40℃ for 6 hours to obtain a nickel foam supported bimetallic nickel cobalt phosphide / sulfide heterostructure hydrogen evolution catalyst with a loading area of ​​1 cm². 2 .

[0040] Example 2

[0041] (1) Cut the nickel foam into small pieces of 1cm*2cm and place them in acetone, 3M hydrochloric acid solution, anhydrous ethanol and deionized water respectively for ultrasonic cleaning for 15 minutes. Then, vacuum dry at 40℃ for 6 hours to remove the oxides on its surface.

[0042] (2) Weigh out CoCl2·6H2O, NiCl2·6H2O, C6H5Na3O7·2H2O, and NaH2PO2 to prepare an electrolyte containing 55 mM CoCl2, 33 mM NiCl2, 20 mM C6H5Na3O7, and 0.2 M NaH2PO2. Add the prepared electrolyte to the electrolytic cell. Using nickel foam as the working electrode, and a graphite rod and an Ag / AgCl electrode as the counter electrode and reference electrode, respectively, electrodeposit nickel-cobalt phosphide using a chronoamperometry method under magnetic stirring at 400 rpm. Rinse and wash the resulting electrodes with deionized water and ethanol, and vacuum dry at 40°C for 6 hours to obtain a nickel foam-supported nickel-cobalt phosphide catalyst with a loading area of ​​1 cm². 2 .

[0043] Example 3

[0044] Step (3) in Example 1 was removed, while the remaining steps were the same as in Example 1, resulting in a nickel foam-supported nickel-cobalt sulfide nanoarray with a loading area of ​​1 cm². 2 .

[0045] Example 4

[0046] (1) Cut the nickel foam into small pieces of 1cm*2cm and place them in acetone, 3M hydrochloric acid solution, anhydrous ethanol and deionized water respectively for ultrasonic cleaning for 15 minutes. Then, vacuum dry at 40℃ for 6 hours to remove the oxides on its surface.

[0047] (2) Weigh NiCl2·6H2O and CH4N2S to prepare an electrolyte containing 0.05M NiCl2 and 0.5M CH4N2S; add the prepared electrolyte to the electrolytic cell, using nickel foam, platinum sheet, and saturated calomel electrode as the working electrode, counter electrode, and reference electrode, respectively, and perform electrodeposition using cyclic voltammetry (CV) electrodeposition with magnetic stirring at 400 rpm. The voltage range is –1.3-0.3V, and the electrodeposition frequency is 5mV s. -1 The scanning cycle was repeated 4 times at the specified scanning speed. The resulting electrodes were rinsed with deionized water and ethanol, respectively, and then vacuum-dried at 40°C for 6 hours to obtain a nickel foam-supported nickel sulfide nanosheet array with a loading area of ​​1 cm². 2 ;

[0048] The catalysts prepared in Examples 1-4 above were characterized in terms of morphology, structure and chemical properties.

[0049] Figure 1 The images show pretreated nickel foam and the catalysts prepared in Examples 1 and 3. By comparison, it can be seen that after gradual electrodeposition, the surface color of the nickel foam changes from silver-white to black.

[0050] Scanning electron microscopy (SEM) images are used to characterize the morphology and structure of samples, from... Figure 2 It can be seen that the surface of the nickel foam skeleton is smooth, but becomes rough after electrodeposition. The catalyst prepared in Example 4 is loaded on the nickel foam in large, broken pieces, while the catalysts in Examples 1 and 3 are loaded on the nickel foam more tightly.

[0051] Figure 3 a shows the amorphous morphology of Example 4, while in contrast, after adding cobalt chloride to the deposited electrolyte, Comparative Example 2 exhibited a 3D wrinkled nanosheet morphology. Figure 3 As shown in b, the phosphates grow uniformly and vertically across the entire nickel foam surface, forming cross-links. After electrodeposition of the phosphates, as shown... Figure 3 As shown in Figure c, the nickel-cobalt sulfide nanosheets are observed to be tightly coated by the phosphide microsphere array, indicating the formation of a hierarchical heterostructure. This hierarchical heterostructure not only increases the specific surface area and provides sufficient mass transfer channels, but also improves the mechanical stability of the electrode to withstand bubble disturbances under high current densities.

[0052] X-ray photoelectron spectroscopy (XPS) is used to study the chemical valence state of catalysts. Figure 4 The XPS spectrum of Example 1 confirms the presence of Ni, Co, P and S elements in the catalyst.

[0053] Figure 5 In the high-resolution XPS spectrum of Ni2p, the two doublets at 855.89 / 873.39 eV and 857.59 / 875.59 eV correspond to Ni 2+ and Ni 3+ The weak peaks at 853.05 and 870.56 eV originate from the Ni on the nickel substrate. 0 The peaks at 780.24 and 795.88 eV of Co2p are related to the Co-P bond. 3 / 2 782.40 eV and Co 2p 1 / 2 The two peaks at 797.64 eV indicate that Co in the sample 2+ and Co 2+ Coexistence. The XPS spectrum of P2p can be divided into three peaks, of which the peak at 133.20 eV can be attributed to the oxidation state of surface oxidation. The S2p spectrum can be separated at 161.81 (S2p 3 / 2 ) and 163.23 eV (S2p 1 / 2 The peaks are attributed to metal sulfur bonds (Ni-S and Co-S).

[0054] The catalysts prepared in Examples 1-4 above were tested for their electrocatalytic hydrogen evolution performance in a three-electrode system.

[0055] Hydrogen evolution tests were performed using an electrochemical workstation, with 1M KOH alkaline solution as the electrolyte. Samples prepared in Examples 1-4 were used as 1cm samples.2 The working electrodes were tested using a graphite rod and a Hg / HgO electrode as the counter and reference electrodes, respectively. Linear sweep voltammetry was employed at 5 mV / s. -1 The scan rate is [missing information]. All electrode potentials are iR compensated and converted to the reversible hydrogen electrode (RHE) potential according to the Nernst equation: E [missing information]. RHE =E Hg / HgO +0.098V +0.0591×pH, where E RHE E is relative to the reversible hydrogen electrode potential. Hg / HgO The potential of the mercury / mercury oxide standard electrode is given, and the pH of the 1M KOH solution is approximately 14.

[0056] The chronopotentiometric method (CP) was used to test at 10, 100, and 500 mA cm⁻¹. -2 Electrocatalytic hydrogen evolution stability of Example 1 at current density. Furthermore, a comparative electrode was prepared by drop-coating 20 wt% commercial Pt / C onto nickel foam of the same area.

[0057] from Figure 6 The polarization curves show that, thanks to the strong interfacial interaction between the bimetallic nickel-cobalt sulfide and nickel-cobalt phosphide, Example 1 exhibits significantly enhanced hydrogen evolution catalytic activity. Example 1 at 10 and 100 mA cm⁻¹ -2 The minimum overpotentials at current densities of 68 and 144 mV were significantly lower than those in Examples 2 (182 and 258 mV), 3 (163 and 288 mV), and nickel foam (303 and 496 mV). Furthermore, Example 1 maintained high catalytic activity in the high current region, at 500 mA cm⁻¹. -2 The overpotential is only 222mV. Figure 6 b lists the corresponding 10, 100, and 500 mA cm -2 The overpotential value below.

[0058] Table 1. Comparison of the electrocatalytic hydrogen evolution activity of the catalyst in Example 1 with that in other literature in 1M KOH electrolyte:

[0059] Table 1

[0060]

[0061] The table lists a comparison of the electrocatalytic hydrogen evolution activity of Example 1 of this patent with that of catalysts in some other literature in 1M KOH electrolyte. It can be seen that the hydrogen evolution activity of Example 1 (especially at high current density) is better than that of catalysts reported in other literature, which indicates that this catalyst is a catalyst with great application prospects.

[0062] Figure 7The stability test graph for Example 1 shows the results at 10, 100, and 500 mA cm⁻¹. -2 The stability under current density shows that Example 1 has good alkaline electrocatalytic hydrogen evolution stability. After running for 110 hours at both low and high current densities, its potential did not change significantly.

[0063] Finally, it should be noted that the above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not limited to the specific implementation methods described above. Those skilled in the art can make changes, modifications, substitutions, and variations within the scope of the claims, which do not affect the substantive content of the present invention. The specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. All equivalent changes and modifications made within the scope of the claims of this invention should be considered within the scope of this invention.

Claims

1. A method for preparing a nickel foam-supported bimetallic phosphide / sulfide heterostructure hydrogen evolution catalyst, characterized in that, Includes the following steps: (1) The nickel foam was ultrasonically cleaned and then vacuum dried to remove the oxides on its surface; (2) Add a pre-prepared electrolyte containing NiCl2, CoCl2 and CH4N2S to an electrolytic cell. Use nickel foam, platinum sheet and saturated calomel electrode as working electrode, counter electrode and reference electrode respectively. Electrodeposition is carried out by cyclic voltammetric electrodeposition under stirring. The obtained working electrode is washed with deionized water and ethanol respectively. Vacuum drying is used to obtain nickel foam supported nickel cobalt sulfide nanosheet array. (3) Add a pre-prepared electrolyte containing CoCl2, NiCl2, C6H5Na3O7 and NaH2PO2 to the electrolytic cell. Use the nickel foam supported nickel cobalt sulfide nanosheet array obtained in step (2) as the working electrode, and the graphite rod and Ag / AgCl electrode as the counter electrode and reference electrode, respectively. Electrodeposit phosphide by chronoamperometry under stirring. Wash and vacuum dry the obtained working electrode to obtain the nickel foam supported bimetallic phosphide / sulfide heterostructure hydrogen evolution catalyst.

2. The preparation method according to claim 1, characterized in that, In step (1), the nickel foam is ultrasonically cleaned for 10-20 minutes in acetone, 2-4M hydrochloric acid solution, anhydrous ethanol and deionized water, respectively.

3. The preparation method according to claim 1, characterized in that, In step (2), the electrodeposition conditions are as follows: magnetic stirring at a speed of 200-400 rpm; voltage range of –1.3 to 0.3 V; and electrodeposition scan rate of 5 mV / s. -1 The scanning cycle count is 4.

4. The preparation method according to claim 1, characterized in that, In step (3), the electrodeposition conditions are: magnetic stirring with a stirring speed of 200-400 rpm; deposition potential of -1.2V; and deposition time of 10-30 minutes.

5. The preparation method according to claim 1, characterized in that, In step (2), the electrolyte is a solution containing 0.05M NiCl2, 0.125M CoCl2 and 0.25-1M CH4N2S.

6. The preparation method according to claim 1, characterized in that, In step (3), the electrolyte is a solution containing 55mM CoCl2, 33mM NiCl2, 20mM C6H5Na3O7 and 0.2M NaH2PO2.

7. The preparation method according to claim 1, characterized in that, In steps (1), (2), and (3), the vacuum drying temperature is 40-60℃ and the drying time is 4-6 hours.

8. A nickel foam-supported bimetallic phosphide / sulfide heterostructure hydrogen evolution catalyst prepared by the method according to any one of claims 1–7.

9. The nickel foam-supported bimetallic phosphide / sulfide heterostructure hydrogen evolution catalyst according to claim 8, characterized in that: The bimetal is nickel and cobalt.

10. The application of the nickel foam supported bimetallic phosphide / sulfide heterostructure catalyst as described in claim 8 in the electrocatalytic hydrogen evolution reaction.

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