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

Abstract

The invention discloses a preparation method of a cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis, and belongs to the technical field of catalysts and batteries. The preparation method comprises the following steps: soaking foamed nickel in an aqueous solution containing nickel nitrate, urea and ammonium fluoride for hydrothermal reaction, and washing and drying the foamed nickel subjected to hydrothermal reaction to obtain Ni (OH) 2; the preparation method comprises the following steps: carrying out phosphating reaction on a phosphorus source and Ni (OH) 2 in an inert atmosphere to obtain a Ni2P nano array; the phosphorus source is sodium hypophosphite; adding cerous nitrate into distilled water, and stirring and dissolving at normal temperature to obtain a solution A; and taking the Ni2P nano array as a working electrode, soaking the Ni2P nano array in the solution A for electrodeposition reaction, and cleaning and drying a reaction product by using deionized water to obtain the cerium hydroxide / nickel phosphide nano array heterostructure oxygen evolution electrode material for seawater electrolysis. By promoting rearrangement of an electronic structure at a heterogeneous interface and optimizing the adsorption energy of an intermediate, the water electrolysis catalysis efficiency is improved, the preparation period is short, the controllability is good, and good stability is shown in seawater.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts and batteries, and in particular to a method for preparing a cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis. Background Art

[0002] Hydrogen is considered the most ideal energy carrier due to its clean, pollution-free, efficient, safe, storable and transportable advantages. Hydrogen produced by water electrolysis has the advantages of high product purity, green and low carbon. The current existing water electrolysis methods rely on high-purity water, but global freshwater resources are increasingly scarce and seriously polluted. The earth's seawater resources are extremely abundant, so the electrolysis of seawater may become the most promising hydrogen production technology. Direct electrolysis of seawater to produce hydrogen, hydrogen as a fuel will produce high-purity fresh water, which will achieve the purpose of seawater purification and hydrogen production at the same time. However, the composition of seawater is very complex, with high concentrations of Cl - Not only will the ions compete with the oxygen evolution reaction (OER) at the anode, but they will 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) show excellent activity and stability, but their high prices and scarce reserves limit their widespread use. Therefore, the design and development of low-cost, efficient and stable oxygen evolution catalysts is the key to improving the performance of hydrogen production from water electrolysis.

[0003] Transition metal phosphides exhibit excellent electrocatalytic activity due to their adjustable electronic structure and enhanced conductivity. However, the strong adsorption strength of oxygen-containing intermediates on the Ni metal active site seriously hinders the improvement of its oxygen evolution performance. Regulation of electronic structure is an effective strategy to optimize binding energy and improve the activity of transition metal phosphide catalysts. Heterointerface engineering can promote the redistribution of surface charge in the interface region and regulate the adsorption energy of intermediates at active sites, thereby optimizing catalytic performance. The construction and preparation process of heterostructures in the prior art is complicated, mainly involving the high-temperature calcination process in which the catalyst is prone to sintering and has many by-products. In addition, there is no further explanation of its regulatory effect on the catalytic stability of oxygen evolution reaction in seawater.

[0004] Therefore, it is very important to construct heterojunctions through simple and easy strategies to solve the above problems and achieve excellent electrocatalytic performance and stability of the materials. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis, which improves the catalytic efficiency of water electrolysis by promoting the rearrangement of the electronic structure at the heterogeneous interface and optimizing the adsorption energy of the intermediate.

[0006] To achieve the above object, the present invention provides a method for preparing 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 hydrothermal nickel foam, and drying it to obtain Ni(OH)2;

[0008] (2) subjecting a phosphorus source and Ni(OH)2 to a phosphating reaction under an inert atmosphere to obtain a Ni2P nanoarray; wherein the phosphorus source is sodium hypophosphite;

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

[0010] (4) The Ni2P nanoarray obtained in (2) is used as a working electrode and immersed in the A solution obtained in (3) to perform an electrodeposition reaction. The reaction product is washed with deionized water and dried to obtain a cerium hydroxide / nickel phosphide nanoarray heterostructure oxygen evolution electrode material for seawater electrolysis.

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

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

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

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

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

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

[0017] Therefore, the present invention adopts the above-mentioned method for preparing the cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis, which has the following beneficial effects:

[0018] (1) The method for preparing the cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis proposed in the present invention has a simple preparation process, a short preparation cycle and good controllability compared to the traditional preparation method.

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

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

[0021] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the SEM image of the sample prepared in Example 1 of the present invention;

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

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

[0025] Figure 4 This is the SEM image of the sample prepared in Example 2 of the present invention;

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

[0027] Figure 6 This is the SEM image of the sample prepared in Example 3 of the present invention;

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

[0029] Figure 8 This is the SEM image of the sample prepared in Example 4 of the present invention;

[0030] Fig. 9 The XRD pattern of the sample prepared in Example 4 of the present invention;

[0031] Fig.10 This is the SEM image of the sample prepared in Example 5 of the present invention;

[0032] Fig.11 This is the XRD pattern of the sample prepared in Example 5 of the present invention. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0034] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0035] In addition, it should be understood that although this specification is described according to the implementation modes, not every implementation mode includes only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. These other implementation modes are also covered within the protection scope of the present invention.

[0036] Embodiment 1

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

[0038] (1) Weigh 1 mmol of nickel nitrate, 5 mmol of urea, and 3 mmol of ammonium fluoride and dissolve them in 50 mL of deionized water; 2 The nickel foam is placed in the above solution and transferred to a reactor, heated to 120°C in an oven and kept warm for 12 hours. The treated nickel foam is then repeatedly washed with deionized water and ethanol in turn and dried at 60°C for 12 hours.

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

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

[0041] (4) Cut the Ni2P nanoarray obtained in (2) into 2×1 cm 2 The electrode sheet was used as the working electrode and immersed in the 0.02 mmol / mL A solution described in (3) for electrodeposition for 400 s to obtain a 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 the present invention. It can be seen from the figure that Ce(OH)3 particles are evenly modified on both sides of the Ni2P nanosheets, which present a nanosheet morphology similar to Ni2P. The formed open porous structure enhances the accessibility of the active sites and the full contact with the electrolyte, which is beneficial to promote the improvement of the oxygen evolution reaction activity of the cerium hydroxide / nickel phosphide heterostructure.

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

[0044] Figure 3 The linear sweep voltammetry curve of the cerium hydroxide / nickel phosphide heterostructure catalyst prepared in Example 1 of the present invention is shown in Figure 2. The polarization curve shows that the cerium hydroxide / nickel phosphide heterostructure can obtain 100 mA cm with an overpotential of only 265 mV. -2 The current density of Ni2P was 2.34 W / m, indicating that it has excellent catalytic activity for oxygen evolution reaction. The hierarchical porous structure is conducive to the exposure of active sites. In addition, the strong synergistic effect between Ni2P and Ce(OH)3 improves the electron transfer capacity and reaction kinetics, thereby promoting the improvement of its catalytic activity for oxygen evolution reaction.

[0045] Embodiment 2

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

[0047] (1) Weigh 1 mmol of nickel nitrate, 5 mmol of urea, and 3 mmol of ammonium fluoride and dissolve them in 50 mL of deionized water. 2 The nickel foam was placed in the above solution and transferred to the reactor, heated to 120°C in an oven and kept warm for 12 hours. The hydrothermal 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 nickel foam after the above drying treatment were placed in the upstream and downstream positions of the tube furnace respectively, and kept at 350° C. for 2 h in an argon atmosphere to finally obtain a Ni2P nanoarray.

[0049] (3) Cut the Ni2P nanoarray obtained above into 2×1 cm 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 to obtain 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 the present invention.

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

[0052] Embodiment 3

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

[0054] (1) Weigh 1 mmol of nickel nitrate, 5 mmol of urea, and 3 mmol of ammonium fluoride and dissolve them in 50 mL of deionized water; 2 The nickel foam was placed in the above solution and transferred to a reactor, heated to 120°C in an oven, and kept warm 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 nickel foam after the above drying treatment were placed in the upstream and downstream positions of the tube furnace respectively, and kept at 350° C. for 2 h in an argon atmosphere to finally obtain a Ni2P nanoarray.

[0056] (3) Cut the Ni2P nanoarray obtained above into 2×1 cm 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 to obtain 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 the present invention.

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

[0059] Embodiment 4

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

[0061] (1) Weigh 1 mmol of nickel nitrate, 5 mmol of urea, and 3 mmol of ammonium fluoride and dissolve them in 50 mL of deionized water; 2 The nickel foam was placed in the above solution and transferred to a reactor, heated to 120°C in an oven, and kept warm 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 nickel foam after the above drying treatment were placed in the upstream and downstream positions of a tube furnace respectively, in an argon atmosphere, and finally a Ni2P nanoarray was obtained.

[0063] (3) Cut the Ni2P nanoarray obtained above into 2×1 cm 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 to obtain 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 the present invention.

[0065] Fig. 9 This is the XRD diagram of the cerium hydroxide / nickel phosphide heterostructure catalyst prepared in Example 4 of the present invention.

[0066] Embodiment 5

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

[0068] (1) Weigh 1 mmol of nickel nitrate, 5 mmol of urea, and 3 mmol of ammonium fluoride and dissolve them in 50 mL of deionized water; 2 The nickel foam was placed in the above solution and transferred to a reactor, heated to 120°C in an oven, and kept warm 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 nickel foam after the above drying treatment were placed in the upstream and downstream positions of a tube furnace respectively, in an argon atmosphere, and finally a Ni2P nanoarray was obtained.

[0070] (3) Cut the Ni2P nanoarray obtained above into 2×1 cm 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 to obtain a cerium hydroxide / nickel phosphide heterostructure.

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

[0072] Fig.11 This is the XRD diagram of the cerium hydroxide / nickel phosphide heterostructure catalyst prepared in Example 5 of the present invention.

[0073] The samples prepared in Examples 1-5 were subjected to electrochemical tests, and the test results are shown in Table 1:

[0074] Example 1-5 Preparation of samples at 100 mA cm -2 Statistics of overpotential values

[0075] project 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 to 5 have a -2 The overpotential at the current density is kept in the range of 265-276 mV. Figure 1 It can be seen that after 400s of electrodeposition, ultrafine cerium hydroxide nanoparticles are evenly 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 the cerium hydroxide / nickel phosphide heterostructure catalyst in this comparative example is exactly the same as the preparation method of the cerium hydroxide / nickel phosphide heterostructure catalyst in Example 1, except that the electrodeposition time is 200 s.

[0079] Comparative Example 2

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

[0081] Comparative Example 3

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

[0083] The cerium hydroxide / nickel phosphide heterostructure catalysts for seawater electrolysis prepared in Example 1 and Comparative Examples 1-3 were heated at 100 mA cm -2 The overpotential values ​​are compared, and the test results are shown in Table 2:

[0084] Table 2 Samples prepared in Example 1 and Example 1-3 at 100 mA cm -2 Statistics of overpotential values

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

[0086] Combining Example 1, Comparative Examples 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 preparation method of the above-mentioned cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis, which improves the catalytic efficiency of water electrolysis by promoting the rearrangement of the electronic structure at the heterogeneous interface and optimizing the adsorption energy of the intermediate. The preparation cycle is short, the controllability is good, and it shows good stability in seawater.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis, characterized in that: The following steps are involved: (1) soaking the nickel foam in an aqueous solution containing nickel nitrate, urea and ammonium fluoride to perform a hydrothermal reaction, washing the hydrothermal nickel foam, and drying it to obtain Ni(OH)2; (2) subjecting a phosphorus source and Ni(OH)2 to a phosphating reaction under an inert atmosphere to obtain a Ni2P nanoarray; wherein the phosphorus source is sodium hypophosphite; (3) adding cerium nitrate into distilled water, stirring and dissolving at room temperature to obtain solution A; (4) The Ni2P nanoarray obtained in (2) is used as a working electrode and immersed in the A solution obtained in (3) to perform an electrodeposition reaction. The reaction product is washed with deionized water and dried to obtain a cerium hydroxide / nickel phosphide nanoarray heterostructure oxygen evolution electrode material for seawater electrolysis.

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: The temperature of the hydrothermal reaction in step (1) is 120° C., and the time of the hydrothermal reaction is 12 h.

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: The temperature of the phosphating treatment in step (2) is 350° C., and the time of the phosphating treatment is 2 h.

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

7. The method for preparing the cerium hydroxide / nickel phosphide heterostructure catalyst for seawater electrolysis according to claim 1, characterized in that: The electrodeposition time in step (4) is 380-420 s, the deposition voltage is -1.0 V, and the reference electrode is Ag / AgCl.

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