Preparation method of cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis

Abstract

The application discloses a preparation method of a cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis, and belongs to the technical fields of catalysts and batteries. Foam nickel is soaked in an aqueous solution containing nickel nitrate, urea and ammonium fluoride to perform a hydrothermal reaction, the foam nickel after the hydrothermal reaction is washed, dried, and Ni(OH)2 is obtained; a phosphorus source and the Ni(OH)2 are subjected to a phosphorization reaction under an inert atmosphere to obtain Ni2P nanometer arrays; the phosphorus source is sodium hypophosphite; cerium nitrate is added to distilled water, stirred and dissolved at normal temperature to obtain an A solution; the Ni2P nanometer arrays are used as a working electrode, soaked in the A solution to perform an electrodeposition reaction, the reaction product is washed with deionized water, dried, and a cerium hydroxide / nickel phosphide nanometer array heterostructure oxygen evolution electrode material for seawater electrolysis is obtained. The application promotes the rearrangement of an electronic structure at a heterojunction, optimizes adsorption energy of an intermediate, and thus improves the water electrolysis catalytic efficiency, has a short preparation cycle, good controllability, and good stability in seawater.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalyst and battery technology, in particular to a preparation method of a cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis. BACKGROUND

[0002] Hydrogen energy is considered as the most ideal energy carrier due to its clean, efficient, safe, storable and transportable advantages. Hydrogen produced by water electrolysis has the advantages of high product purity and green low carbon. The existing water electrolysis method currently relies on high-purity water, but the global freshwater resources are increasingly scarce and severely polluted. The seawater resources on earth are extremely abundant, so electrolysis of seawater may become the most promising hydrogen production technology. Direct electrolysis of seawater to produce hydrogen gas, and hydrogen gas as fuel to produce high-purity freshwater, will achieve the purpose of seawater purification and hydrogen production at the same time. However, the composition of seawater is very complex, and the high concentration of Cl - Ions not only compete with the oxygen evolution reaction (OER) at the anode, but also severely corrode most catalysts containing metal elements. In addition, the complex four-electron transfer process at the anode leads to slow kinetics. Traditional noble metal catalysts (Pt, IrO2, RuO2) exhibit excellent activity and stability, but their high price and scarce reserves limit their widespread use. Therefore, designing and developing low-cost, efficient and stable oxygen evolution catalysts is the key to improving the performance of water electrolysis for hydrogen production.

[0003] Transition metal phosphides exhibit superior electrocatalytic activity due to their adjustable electronic structure and enhanced electrical conductivity. However, the strong adsorption strength of oxygen-containing intermediates on Ni metal active sites severely hinders the improvement of their oxygen evolution performance. Adjusting the electronic structure is an effective strategy to optimize the binding energy and improve the activity of transition metal phosphide catalysts. Heterojunction engineering can promote the redistribution of surface charges in the interface region, adjust the adsorption energy of intermediates on active sites, and thus optimize the catalytic performance. The existing technology for building heterostructures has a complex preparation process, mainly involving high-temperature calcination process, which can easily cause sintering of the catalyst and produce many by-products. In addition, there is no further explanation of its regulation effect on the catalytic stability of the oxygen evolution reaction in seawater.

[0004] Therefore, it is very important to build a heterojunction through a simple and easy strategy to solve the above problems and achieve excellent electrocatalytic performance and stability of the material. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis, which can promote the redistribution of electronic structure at the heterojunction interface, optimize the adsorption energy of intermediates, and thus improve the catalytic efficiency of water electrolysis.

[0006] To achieve the above object, the application provides a preparation method of a cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis, comprising the following steps:

[0007] (1) soaking the nickel foam in an aqueous solution containing nickel nitrate, urea and ammonium fluoride to perform a hydrothermal reaction, washing the nickel foam after the hydrothermal reaction, drying to obtain Ni(OH)2;

[0008] (2) performing a phosphating reaction on the phosphorus source and the Ni(OH)2 in an inert atmosphere to obtain a Ni2P nano array; the phosphorus source is sodium hypophosphite;

[0009] (3) adding cerium nitrate into distilled water, stirring and dissolving at room temperature to obtain an A solution;

[0010] (4) taking the Ni2P nano array obtained in (2) as a working electrode, soaking into the A solution obtained in (3) to perform an electrodeposition reaction, washing the reaction product with deionized water, drying to obtain a cerium hydroxide / nickel phosphide nano array heterostructure oxygen evolution electrode material for seawater electrolysis.

[0011] Preferably, the molar ratio of the nickel nitrate, urea and ammonium fluoride in step (1) is 1:5:3.

[0012] Preferably, the temperature of the hydrothermal reaction in step (1) is 120 DEG C, and the hydrothermal reaction time is 12 h.

[0013] Preferably, the mass ratio of the Ni(OH)2 to the phosphorus source in step (2) is 1:3.

[0014] Preferably, the temperature of the phosphating treatment in step (2) is 350 DEG C, and the phosphating treatment time is 2 h.

[0015] Preferably, the concentration of the A solution in step (3) is 0.02-0.06 mmol / mL.

[0016] Preferably, the electrodeposition time in step (4) is 380-420 s, the deposition voltage is-1.0 V, and the reference electrode is Ag / AgCl.

[0017] Therefore, the application has the following beneficial effects by using the above preparation method of the cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis:

[0018] (1) The preparation method of the cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis has the advantages of simple preparation process, short preparation period and good controllability compared with the traditional preparation method.

[0019] (2) The strong interaction between the cerium hydroxide / nickel phosphide heterostructure and the optimized adsorption energy of intermediate products proposed in this invention improve the catalytic performance of the catalyst in the oxygen evolution reaction during seawater decomposition.

[0020] (3) The heterostructure catalyst prepared by the present invention exhibits good stability in seawater due to the introduction of cerium hydroxide with excellent corrosion resistance and the enhanced repulsion ability of phosphate ions generated during the reaction process against chloride ions.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 The SEM image of the sample prepared in Example 1 of this invention;

[0023] Figure 2 The XRD pattern of the sample prepared in Example 1 of this invention;

[0024] Figure 3 This is a polarization curve of the sample prepared in Example 1 of the present invention;

[0025] Figure 4 The SEM image of the sample prepared in Example 2 of this invention;

[0026] Figure 5 The XRD pattern of the sample prepared in Example 2 of this invention;

[0027] Figure 6 The SEM image of the sample prepared in Example 3 of this invention;

[0028] Figure 7 The XRD pattern of the sample prepared in Example 3 of this invention;

[0029] Figure 8 The SEM image of the sample prepared in Example 4 of this invention;

[0030] Figure 9 The XRD pattern of the sample prepared in Example 4 of this invention;

[0031] Figure 10 The SEM image of the sample prepared in Example 5 of this invention;

[0032] Figure 11 The XRD pattern of the sample prepared in Example 5 of this invention. Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0035] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. These other embodiments are also covered within the scope of protection of this invention.

[0036] Example 1

[0037] A method for preparing a cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis includes the following steps:

[0038] (1) Weigh out 1 mmol of nickel nitrate, 5 mmol of urea, and 3 mmol of ammonium fluoride and dissolve them in 50 mL of deionized water; pour 2 × 4 cm 2 The nickel foam was placed in the above solution and transferred to a reaction vessel. It was heated to 120°C in an oven and kept at that temperature for 12 hours. The treated nickel foam was then washed repeatedly with deionized water and ethanol, and dried at 60°C for 12 hours.

[0039] (2) 400 mg of sodium hypophosphite and the above-mentioned dried nickel foam were placed at the upstream and downstream positions of a tube furnace and kept at 350 °C for 2 h in an argon atmosphere to finally obtain Ni2P nanoarray.

[0040] (3) Add cerium nitrate to distilled water to prepare a 0.02 mmol / L solution A;

[0041] (4) Cut the Ni2P nanoarray obtained in (2) into 2×1cm 2 The electrode sheet is used as the working electrode and is immersed in the 0.02 mmol / mL A solution described in (3) for electrodeposition. The deposition time is 400 s, thus obtaining the cerium hydroxide / nickel phosphide heterostructure.

[0042] Figure 1 This is a SEM image of the cerium hydroxide / nickel phosphide heterostructure catalyst prepared in Example 1 of this invention. As can be seen from the image, Ce(OH)3 particles are uniformly modified on both sides of the Ni2P nanosheets, exhibiting a nanosheet morphology similar to Ni2P. The formed open porous structure enhances the accessibility of active sites and sufficient contact with the electrolyte, which is beneficial for promoting the improvement of the oxygen evolution reaction activity of the cerium hydroxide / nickel phosphide heterostructure.

[0043] Figure 2This is the XRD pattern of the cerium hydroxide / nickel phosphide heterostructure catalyst prepared in Example 1 of this invention. The crystalline phases of Ni2P (PDF#03-0953), Ce(OH)3 (PDF#19-0284), and nickel foam (PDF#04-0850) can be observed in the figure, proving the presence of Ce(OH)3 nanoparticles and the formation of the cerium hydroxide / nickel phosphide heterostructure.

[0044] Figure 3 This is a linear sweep voltammetry curve of the cerium hydroxide / nickel phosphide heterostructure catalyst prepared in Example 1 of this invention. The polarization curve shows that the cerium hydroxide / nickel phosphide heterostructure requires only 265 mV overpotential to achieve 100 mA cm⁻¹. -2 The high current density indicates that it possesses excellent oxygen evolution reaction (OER) catalytic activity. The hierarchical porous structure facilitates the exposure of active sites. Furthermore, the strong synergistic effect between Ni₂P and Ce(OH)₃ enhances electron transport capacity and reaction kinetics, thereby promoting its OER catalytic activity.

[0045] Example 2

[0046] A method for preparing a cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis includes the following steps:

[0047] (1) Weigh out 1 mmol of nickel nitrate, 5 mmol of urea, and 3 mmol of ammonium fluoride, and dissolve them in 50 mL of deionized water. (The remaining text appears to be incomplete and requires further context.) 2 The nickel foam was placed in the above solution and transferred to a reaction vessel, heated to 120°C in an oven, and held at that temperature for 12 hours. The hydrothermally heated nickel foam was then repeatedly washed with deionized water and ethanol, and dried at 60°C for 12 hours.

[0048] (2) 400 mg of sodium hypophosphite and the above-mentioned dried nickel foam were placed at the upstream and downstream positions of a tube furnace and kept at 350 °C for 2 h in an argon atmosphere to finally obtain Ni2P nanoarray.

[0049] (3) Cut the Ni2P nanoarray obtained above into 2×1cm 2 The electrode sheet was used as the working electrode and immersed in a 0.03 mmol / mL cerium nitrate solution for electrodeposition. The deposition time was 390 s, thus obtaining a cerium hydroxide / nickel phosphide heterostructure.

[0050] Figure 4 This is a SEM image of the cerium hydroxide / nickel phosphide heterostructure catalyst prepared in Example 2 of this invention.

[0051] Figure 5 This is the XRD pattern of the cerium hydroxide / nickel phosphide heterostructure catalyst prepared in Example 2 of this invention.

[0052] Example 3

[0053] A method for preparing a cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis includes the following steps:

[0054] (1) Weigh out 1 mmol of nickel nitrate, 5 mmol of urea, and 3 mmol of ammonium fluoride and dissolve them in 50 mL of deionized water; pour 2 × 4 cm 2 The nickel foam was placed in the above solution and transferred to a reaction vessel, heated to 120°C in an oven, and held at that temperature for 12 hours. The treated nickel foam was then repeatedly washed with deionized water and ethanol, and dried at 60°C for 12 hours.

[0055] (2) 400 mg of sodium hypophosphite and the above-mentioned dried nickel foam were placed at the upstream and downstream positions of a tube furnace and kept at 350 °C for 2 h in an argon atmosphere to finally obtain Ni2P nanoarray.

[0056] (3) Cut the Ni2P nanoarray obtained above into 2×1cm 2 The electrode sheet was used as the working electrode and immersed in a 0.04 mmol / mL cerium nitrate solution for electrodeposition. The deposition time was 380 s, thus obtaining a cerium hydroxide / nickel phosphide heterostructure.

[0057] Figure 6 This is a SEM image of the cerium hydroxide / nickel phosphide heterostructure catalyst prepared in Example 3 of this invention.

[0058] Figure 7 This is the XRD pattern of the cerium hydroxide / nickel phosphide heterostructure catalyst prepared in Example 3 of this invention.

[0059] Example 4

[0060] A method for preparing a cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis includes the following steps:

[0061] (1) Weigh out 1 mmol of nickel nitrate, 5 mmol of urea, and 3 mmol of ammonium fluoride and dissolve them in 50 mL of deionized water; pour 2 × 4 cm 2 The nickel foam was placed in the above solution and transferred to a reaction vessel, heated to 120°C in an oven, and held at that temperature for 12 hours. The treated nickel foam was then repeatedly washed with deionized water and ethanol, and dried at 60°C for 12 hours.

[0062] (2) 400 mg of sodium hypophosphite and the above-mentioned dried nickel foam were placed at the upstream and downstream positions of a tube furnace, respectively, and Ni2P nanoarrays were finally obtained in an argon atmosphere.

[0063] (3) Cut the Ni2P nanoarray obtained above into 2×1cm 2 The electrode sheet was used as the working electrode and immersed in a 0.05 mmol / mL cerium nitrate solution for electrodeposition. The deposition time was 410 s, thus obtaining a cerium hydroxide / nickel phosphide heterostructure.

[0064] Figure 8 This is a SEM image of the cerium hydroxide / nickel phosphide heterostructure catalyst prepared in Example 4 of this invention.

[0065] Figure 9 This is the XRD pattern of the cerium hydroxide / nickel phosphide heterostructure catalyst prepared in Example 4 of this invention.

[0066] Example 5

[0067] A method for preparing a cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis includes the following steps:

[0068] (1) Weigh out 1 mmol of nickel nitrate, 5 mmol of urea, and 3 mmol of ammonium fluoride and dissolve them in 50 mL of deionized water; pour 2 × 4 cm 2 The nickel foam was placed in the above solution and transferred to a reaction vessel, heated to 120°C in an oven, and held at that temperature for 12 hours. The treated nickel foam was then repeatedly washed with deionized water and ethanol, and dried at 60°C for 12 hours.

[0069] (2) 400 mg of sodium hypophosphite and the above-mentioned dried nickel foam were placed at the upstream and downstream positions of a tube furnace, respectively, and Ni2P nanoarrays were finally obtained in an argon atmosphere.

[0070] (3) Cut the Ni2P nanoarray obtained above into 2×1cm 2 The electrode sheet was used as the working electrode and immersed in a 0.06 mmol / mL cerium nitrate solution for electrodeposition. The deposition time was 420 s, thus obtaining a cerium hydroxide / nickel phosphide heterostructure.

[0071] Figure 10 This is a SEM image of the cerium hydroxide / nickel phosphide heterostructure catalyst prepared in Example 5 of this invention.

[0072] Figure 11 This is the XRD pattern of the cerium hydroxide / nickel phosphide heterostructure catalyst prepared in Example 5 of this invention.

[0073] Electrochemical tests were performed on the samples prepared in Examples 1-5, and the results are shown in Table 1:

[0074] Samples prepared in Examples 1-5 at 100 mA / cm² -2 Overpotential numerical statistics table

[0075] Item Overpotential @ 100 (mV) Example 1 265 Example 2 268 Example 3 270 Example 4 273 Example 5 276

[0076] As shown in Table 1, the electrode sheets prepared in Examples 1-5 have a performance of 100 mA cm⁻¹ -2 The overpotential at the current density remains within the range of 265-276 mV. Figure 1 It can be seen that after 400s electrodeposition, the ultrafine cerium hydroxide nanoparticles are uniformly dispersed on both sides of the nickel phosphide nanosheets, which is beneficial to the exposure of active sites and promotes the catalytic reaction.

[0077] Comparative Example 1

[0078] The preparation method of this comparative cerium hydroxide / nickel phosphide heterostructure catalyst is exactly the same as that of the cerium hydroxide / nickel phosphide heterostructure catalyst in Example 1. The difference is that the electrodeposition time is 200s.

[0079] Comparative Example 2

[0080] The preparation method of this comparative cerium hydroxide / nickel phosphide heterostructure catalyst is exactly the same as that of the cerium hydroxide / nickel phosphide heterostructure catalyst in Example 1. The difference is that the electrodeposition time is 600s.

[0081] Comparative Example 3

[0082] The preparation method of this comparative cerium hydroxide / nickel phosphide heterostructure catalyst is exactly the same as that of the cerium hydroxide / nickel phosphide heterostructure catalyst in Example 1. The difference is that the electrodeposition time is 800s.

[0083] The cerium hydroxide / nickel phosphide heterostructure catalysts for seawater electrolysis prepared in Examples 1 and Comparative Examples 1-3 were subjected to an amplitude of 100 mA cm⁻¹. -2 The overpotential values ​​were compared, and the test results are shown in Table 2:

[0084] Table 2. Samples prepared in Examples 1 and 1-3 at 100 mA cm⁻¹ -2 Overpotential numerical statistics table

[0085] Item Overpotential @ 100 (mA) Example 1 265 Comparative Example 1 335 Comparative Example 2 342 Comparative Example 3 353

[0086] Combined with Examples 1, 1, 2 and 3, it can be seen that changing the electrodeposition time affects the specific surface area and pore size distribution of the heterostructure catalyst, thereby reducing the activity of the cerium hydroxide / nickel phosphide catalyst as an anode electrode material for seawater electrolysis.

[0087] Therefore, the present invention adopts the above-mentioned preparation method of cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis, which improves the catalytic efficiency of water electrolysis by promoting the rearrangement of electronic structure at the heterostructure interface and optimizing the adsorption energy of intermediates. The preparation cycle is short, the controllability is good, and it exhibits good stability in seawater.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis, characterized in that, Includes the following steps: (1) The foamed nickel was immersed in an aqueous solution containing nickel nitrate, urea and ammonium fluoride to carry out a hydrothermal reaction. The hydrothermally reacted foamed nickel was washed and dried to obtain Ni(OH)2. (2) Phosphating reaction of phosphorus source and Ni(OH)2 under an inert atmosphere to obtain Ni2P nanoarray; the phosphorus source is sodium hypophosphite; (3) Add cerium nitrate to distilled water and stir to dissolve at room temperature to obtain solution A; (4) The Ni2P nanoarray obtained in (2) is used as the working electrode and immersed in the A solution obtained in (3) for electrodeposition reaction. The reaction product is washed with deionized water and dried to obtain the oxygen evolution electrode material of cerium hydroxide / nickel phosphide nanoarray heterostructure for seawater electrolysis. In step (4), the electrodeposition time is 380-420s, the deposition voltage is -1.0V, and the reference electrode is Ag / AgCl.

2. The method for preparing the cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis according to claim 1, characterized in that, In step (1), the molar ratio of nickel nitrate, urea and ammonium fluoride is 1:5:

3.

3. The method for preparing the cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis according to claim 1, characterized in that, In step (1), the hydrothermal reaction temperature is 120℃ and the hydrothermal reaction time is 12h.

4. The method for preparing the cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis according to claim 1, characterized in that, In step (2), the mass ratio of Ni(OH)2 to phosphorus source is 1:

3.

5. The method for preparing the cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis according to claim 1, characterized in that, In step (2), the phosphating temperature is 350℃ and the phosphating time is 2h.

6. The method for preparing the cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis according to claim 1, characterized in that, In step (3), the concentration of solution A is 0.02-0.06 mmol / mL.

Images