Preparation method of nickel phosphide / cerium dioxide catalyst with three-dimensional ordered macroporous structure

Abstract

The invention discloses a preparation method of a nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure, which comprises the following steps: firstly, preparing MMA (Methyl Methacrylate) microsphere emulsion, then preparing PMMA (Polymethyl Methacrylate) template microspheres, then preparing NiO / CeO2, and finally obtaining a Ni2P / CeO2 catalyst. According to the three-dimensional ordered Ni2P / CeO2 catalyst disclosed by the invention, a heterogeneous catalyst with uniformly distributed metals is synthesized by adopting a template method, and the method has universality. The three-dimensional ordered macroporous Ni2P / CeO2 catalyst provided by the invention has abundant edges, thin walls, interconnected mesopores / macropores and a conductive network, and can more quickly promote the quick transfer of mass and charges in the OER catalytic reaction process. The catalyst obtained in the invention shows excellent OER reaction activity and dynamic characteristics when used in an OER reaction, and the invention points out a direction for monitoring the dynamic reconstruction process of the OER catalyst and clarification of a real catalytic mechanism.

Description

Technical Field

[0001] The invention belongs to the technical field of new materials, and specifically is a method for preparing a nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure. Background Art

[0002] The rational application of transition metal phosphides (TMPs) catalysts is an effective way to solve the current bottleneck of water electrolysis research. In particular, nickel phosphide with a special pore structure is a pioneer in TMPs due to its good properties such as cost-effectiveness, natural abundance and unique electronic structure. In recent years, nickel phosphide-based electrocatalytic materials have been widely used in the field of oxygen evolution reaction (OER).

[0003] However, due to the high electronegativity of phosphorus atoms in phosphides, the transfer of electrons in metals is severely hindered, reducing the electron transfer rate. It is particularly noteworthy that severe leaching of elemental phosphorus usually occurs during the OER process, while the actual effect of residual phosphate on OER is still unclear, and there is a lack of in-depth research on the relationship between catalyst construction rules, electronic properties, and performance. Moreover, it is difficult to achieve significant catalytic activity improvement using only single metal phase TMPs.

[0004] Therefore, introducing multiphase interface engineering and pore structure engineering into the same catalyst provides a new strategy for accelerating electron transfer within the material and regulating the internal electronic structure of the catalyst. It also provides ideas for designing new TMPs-based electrocatalytic materials with clear mechanisms. Summary of the invention

[0005] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a method for preparing a nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure.

[0006] The technical solution of the present invention to solve the technical problem is to provide a method for preparing a nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure, characterized in that the method comprises the following steps:

[0007] (1) Preparation of MMA microsphere emulsion: After deionized water and MMA are uniformly mixed, they are heated to the reaction temperature in an oxygen-free environment. After the temperature stabilizes, an initiator is added and the reaction is stirred until the solution becomes a milky emulsion to obtain an MMA microsphere emulsion;

[0008] (2) Preparation of PMMA template microspheres: The MMA microsphere emulsion of step (1) is subjected to low-speed centrifugation to remove the supernatant and take out the middle layer emulsion; the middle layer emulsion is then mixed with deionized water, and then subjected to low-speed centrifugation to remove the supernatant and take out the middle layer emulsion; after repeating the mixing and low-speed centrifugation process at least 3 times, the middle layer emulsion obtained is a mixed emulsion with uniform PMMA particle size; the mixed emulsion is then subjected to high-speed centrifugation to arrange the microspheres, and the PMMA template microspheres are obtained after drying;

[0009] (3)NiO / CeO 2 Preparation: Methanol, ethylene glycol, concentrated nitric acid and deionized water are mixed evenly to obtain a mixed solvent; cerium salt, nickel salt and pore-forming agent are dissolved in the mixed solvent to obtain a mixed solution; PMMA template microspheres in step (2) are added to the mixed solution and allowed to stand until the gaps of the PMMA template microspheres are completely filled with the mixed solution, and solid products are collected by suction filtration; the solid products are calcined to remove the PMMA template microspheres to obtain NiO / CeO 2 ;

[0010] (4)Ni 2 P / CeO 2 Catalyst preparation: NiO / CeO 2 The phosphorus source is placed in an oxygen-free environment, and the phosphine gas is carried to the NiO / CeO 2 A phosphating reaction is carried out on the catalyst, and after the reaction is completed, a black product, namely a nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure, is obtained.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] (1) The three-dimensional ordered Ni 2 P / CeO 2 The catalyst uses a template method to synthesize a heterogeneous catalyst with uniform metal distribution, which is universal. 2 P and cubic fluorite CeO 2 The overall morphology and structure are three-dimensional ordered macroporous structures (140-160 nm) with a wall thickness of 10-15 nm. The adjacent template balls can be calcined to produce micropores with a diameter of 50-60 nm.

[0013] (2) The three-dimensional ordered macroporous N i2 P / CeO 2 The catalysts have abundant edges, thin walls, interconnected meso / macropores, and conductive networks, which can facilitate the rapid transfer of mass and charge during the OER catalytic reaction.

[0014] (3) The three-dimensional ordered macroporous N i2 P / CeO2 The catalyst used in the OER reaction can produce a "structural self-optimization effect". 2 P was reconstructed in situ to nickel oxyhydroxide (NiOOH), accompanied by the leaching and oxidation of elemental P to phosphate (PO 4 3- ) and then adsorbed onto the catalyst surface, finally generating PO 4 3+ -NiOOH / CeO 2 The catalyst acts as the real active phase.

[0015] (4) PO of the present invention 4 3+ -NiOOH / CeO 2 The catalyst is generated as a real active phase accompanied by a large number of oxygen vacancies (V o ) is generated. The final self-optimized PO 4 3+ -NiOOH / CeO 2 _V o The structure has abundant active sites and exhibits excellent OER reaction activity and kinetic characteristics when used in OER reactions. The present invention points out the direction for monitoring the dynamic reconstruction process of OER catalysts and elucidating the true catalytic mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Ni prepared in Examples 1-5 of the present invention 2 P / CeO 2 X-ray diffraction pattern of the catalyst;

[0017] Figure 2 Ni prepared in Examples 1-4 of the present invention 2 P / CeO 2 Scanning electron microscope image of the catalyst;

[0018] Figure 3 Ni prepared in Example 2 of the present invention 2 P / CeO 2 Transmission electron microscope image of the -10 catalyst;

[0019] Figure 4 Ni prepared in Examples 1-5 of the present invention 2 P / CeO 2 OER performance curve of the catalyst;

[0020] Figure 5 The OER kinetic curves of the catalysts prepared in Examples 2, 4 and 5 of the present invention;

[0021] Figure 6 Ni prepared in Example 2 of the present invention2 P / CeO 2 -10 Transmission electron microscopy and element distribution images of catalyst after OER test;

[0022] Figure 7 Ni prepared in Example 2 of the present invention 2 P / CeO 2 Raman image of -10 catalyst after OER test. DETAILED DESCRIPTION

[0023] The specific embodiments of the present invention are given below. The specific embodiments are only used to further illustrate the present invention in detail and do not limit the protection scope of the present invention.

[0024] The present invention provides a method for preparing a nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure (hereinafter referred to as the method), characterized in that the method comprises the following steps:

[0025] (1) Preparation of MMA (methyl methacrylate) microsphere emulsion: After deionized water and MMA are uniformly mixed, they are heated to the reaction temperature in an oxygen-free environment. After the temperature stabilizes, an initiator is added, and the reaction is continued by stirring until the solution completely turns into a milky emulsion, thereby obtaining an MMA microsphere emulsion;

[0026] Preferably, in step (1), the volume ratio of deionized water to MMA is 34:4-5.

[0027] Preferably, in step (1), the oxygen-free environment is an inert gas environment or a nitrogen environment (preferably nitrogen), and the inert gas is argon.

[0028] Preferably, in step (1), the reaction temperature is 75-85°C (preferably 80°C), and the reaction time is 45-60 min.

[0029] Preferably, in step (1), the initiator is potassium persulfate (K 2 S 2 O 8 ) solution.

[0030] Preferably, in step (1), the concentration of the potassium persulfate solution is 3.8-5.7 mol / L; and the molar ratio of potassium persulfate to MMA is 1:170-255.

[0031] Preferably, in step (1), the stirring speed is 900 to 1500 r / min.

[0032] (2) Preparation of PMMA (polymethyl methacrylate) template microspheres: The MMA microsphere emulsion of step (1) is subjected to low-speed centrifugation to remove the supernatant and take out the middle layer emulsion; the middle layer emulsion is then mixed with deionized water, and then subjected to low-speed centrifugation to remove the supernatant and take out the middle layer emulsion; after repeating the mixing and low-speed centrifugation process at least 3 times, the middle layer emulsion obtained is a mixed emulsion with uniform PMMA particle size; the mixed emulsion is then subjected to high-speed centrifugation to arrange the microspheres, and the PMMA template microspheres are obtained after drying;

[0033] Preferably, in step (2), the low-speed centrifugation process is: centrifugation at 2500-3000 rpm for 0.5-1 h.

[0034] Preferably, in step (2), ultrasonic treatment is used for uniform mixing; the ultrasonic treatment temperature is 20 to 30° C. (preferably 25° C.), the power is 220 to 250 W, and the time is 0.5 to 1 h.

[0035] Preferably, in step (2), the volume ratio of deionized water to supernatant is 1:1 to 1.5.

[0036] Preferably, in step (2), the ultrasonic treatment and low-speed centrifugation process are repeated 3 to 5 times.

[0037] Preferably, in step (2), the high-speed centrifugation process is: centrifugation at 5500-6000 rpm for 3-4 hours.

[0038] Preferably, in step (2), the drying process is: drying at 55-65° C. for 5-10 hours under vacuum conditions.

[0039] Preferably, in step (2), the particle size of the PMMA template microspheres is 220 to 280 nm.

[0040] (3)NiO / CeO 2 Preparation: Methanol, ethylene glycol, concentrated nitric acid and deionized water are mixed uniformly to obtain a mixed solvent; cerium salt, nickel salt and pore-forming agent are dissolved in the mixed solvent to obtain a clear and uniform mixed solution; PMMA template microspheres in step (2) are added to the mixed solution and allowed to stand until the gaps between the PMMA template microspheres are completely filled with the mixed solution, and solid products are collected by suction filtration; the solid products are calcined to remove the PMMA template microspheres to obtain NiO / CeO 2 ;

[0041] Preferably, in step (3), the volume ratio of methanol, ethylene glycol, concentrated nitric acid and deionized water is 7:1 to 2:1:10.

[0042] Preferably, in step (3), concentrated nitric acid is commercially available concentrated nitric acid, and its mass fraction is 68 wt%.

[0043] Preferably, in step (3), the cerium salt is Ce(NO 3 ) 3 、Ce(NO 3 ) 3 6H 2 O、CeCl 3 and CeCl 3 6H 2 O; nickel salt is Ni(NO 3 ) 2 ,Ni(NO 3 ) 2 6H 2 O、NiCl 2 and NiCl 2 6H 2 O; the pore-forming agent is ascorbic acid.

[0044] Preferably, in step (3), in the mixed solution, the total concentration of cerium salt and nickel salt is 0.7-0.9 mol / L (preferably 0.83 mol / L), and the ratio between the two is arbitrary; the concentration of the pore-forming agent is 0.7-0.8 mol / L.

[0045] Preferably, in step (3), the standing time is 2 to 3 hours; and the filtration time is 1 to 2 hours.

[0046] Preferably, in step (3), calcination is carried out in a muffle furnace at a temperature of 350-400° C., for 4-5 hours, and at a heating rate of 1-1.5° C. / min.

[0047] (4)Ni 2 P / CeO 2 Catalyst preparation: NiO / CeO 2 The phosphorus source is placed in an oxygen-free environment, and the phosphine gas is carried to the NiO / CeO 2 A phosphating reaction is carried out on the catalyst, and after the reaction is completed, a black product, namely a nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure, is obtained.

[0048] Preferably, in step (4), the phosphorus source and NiO / CeO 2 The mass ratio is 60:1~2.

[0049] Preferably, in step (4), the phosphorus source is sodium hypophosphite (NaH 2 PO 2 ) and potassium hypophosphite (KH 2 PO 2 ).

[0050] Preferably, in step (4), the oxygen-free environment is an inert gas environment or a nitrogen environment (preferably nitrogen), and the inert gas is argon.

[0051] Preferably, in step (4), the flow rate of the inert gas or nitrogen is 0.05 to 0.2 NI / min.

[0052] Preferably, in step (4), the temperature of the phosphating reaction is 350-400° C., the reaction time is 120-150 min, and the heating rate is 1.5-2° C. / min.

[0053] Preferably, step (4) specifically comprises: mixing NiO / CeO 2 and phosphorus source are placed in two containers (preferably porcelain boats) that are resistant to high temperatures and do not react with them; then NiO / CeO 2 The method comprises placing the phosphorus source at the airflow outlet of a closed heating environment (preferably a tube furnace) at normal pressure, placing the phosphorus source at the airflow inlet, and purging with an inert gas or nitrogen to remove air to form an oxygen-free environment; then, at normal pressure, heating the tube furnace to 350-400° C. at a heating rate of 1.5-2° C. / min in an inert gas or nitrogen atmosphere with a constant flow rate of 0.05-0.2 NI / min, and carrying the phosphine gas generated by the decomposition of the phosphorus source to the NiO / CeO 2 The phosphating reaction is carried out for 120 to 150 minutes. After the reaction is completed, the mixture is naturally cooled to room temperature to obtain a black product, namely a nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure.

[0054] The invention also provides a nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure prepared by the preparation method.

[0055] The present invention also provides an application of the nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure, characterized in that the catalyst is used for electrocatalytic alkaline oxygen evolution reaction.

[0056] In the embodiment, the product is represented by Ni 2 P / CeO 2 -x, where x represents the molar ratio of Ni to Ce is x:1. The molar ratios of Ni to Ce are 5:1, 10:1, and 20:1, respectively, and are marked as Ni 2 P / CeO 2 -5. Ni 2 P / CeO 2 -10. Ni 2 P / CeO 2 -20.

[0057] Example 1

[0058] (1) Add 255 mL of H 2O and 30 mL of MMA were placed in a three-necked flask, and the operation of "nitrogen filling for 2 min-vacuuming for 10 min" was performed three times to ensure that the system was in an oxygen-free environment; then the system was heated to 80 °C and maintained for 10 min, and 0.35 g of K 2 S 2 O 8 K 2 S 2 O 8 4 mL of the solution was stirred for 45 min to obtain a milky emulsion; after cooling to room temperature, an MMA microsphere emulsion was obtained;

[0059] (2) The MMA microsphere emulsion was centrifuged at 2500 rpm for 0.5 h to remove the supernatant and take out the middle layer emulsion; the middle layer emulsion was then mixed with 50 mL of H 2 O ultrasonic treatment for 0.5h, then centrifuged at 2500rpm for 0.5h to remove the supernatant and take out the middle layer emulsion; after repeating the mixing and low-speed centrifugation process for 3 times, the obtained middle layer emulsion was centrifuged at 5500rpm for 3h, and then dried at 60℃ for 5h under vacuum conditions to obtain PMMA template microspheres with a diameter of about 230nm and uniform arrangement;

[0060] (3) 4.31 mL of methanol, 0.92 mL of ethylene glycol, 0.62 mL of 68 wt% nitric acid, and 6.15 mL of deionized water were stirred until uniform to obtain a mixed solvent; 0.723 g of Ce(NO 3 ) 3 6H 2 O, 2.423 g of Ni(NO 3 ) 2 6H 2 O, 1.6g ascorbic acid were added to the mixed solvent and stirred until clear to obtain a clear and uniform mixed solution; 2g PMMA template microspheres with a diameter of 230nm were added to the mixed solution and allowed to stand for 2h, and then the product was collected by suction filtration for 1h; the solid was dried and placed in a muffle furnace, heated to 400℃ at a heating rate of 1℃ / min, calcined at 400℃ for 4h to remove the PMMA template microspheres, and naturally cooled to obtain a three-dimensional ordered macroporous NiO / CeO 2 -5;

[0061] (4) 15 mg of NiO / CeO 2 -5 and 0.9 g of phosphorus source were placed in two porcelain boats respectively; then NiO / CeO 2-5 was placed at the gas flow outlet of the tube furnace, the phosphorus source was placed at the gas flow inlet, and nitrogen was purged to remove air to form an oxygen-free environment; then, under normal pressure, the tube furnace was heated to 350°C at a heating rate of 2°C / min in a nitrogen atmosphere with a constant flow rate of 0.1NI / min, and the phosphine gas generated by the decomposition of the phosphorus source was carried to the NiO / CeO 2 -5 for phosphating reaction for 120 min; after the reaction, the mixture was cooled to room temperature naturally to obtain a black product, namely Ni 2 P / CeO 2 -5 catalyst.

[0062] Example 2

[0063] This embodiment is exactly the same as embodiment 1, except that in step (3), the molar ratio of Ni to Ce is 10:1, and a three-dimensional ordered macroporous structure NiO / CeO is obtained. 2 -10; Step (4) to obtain a three-dimensional ordered macroporous structure Ni 2 P / CeO 2 -10 catalyst.

[0064] Example 3

[0065] This embodiment is exactly the same as embodiment 1, except that in step (3), the molar ratio of Ni to Ce is 20:1, and a three-dimensional ordered macroporous structure NiO / CeO is obtained. 2 -20; Step (4) to obtain a three-dimensional ordered macroporous structure Ni 2 P / CeO 2 -20 catalyst.

[0066] Example 4

[0067] This embodiment is completely the same as the embodiment 1, except that: in step (3), the concentration of Ni is 0.83 mol / L, Ce is not added, and a three-dimensional ordered macroporous structure NiO is obtained; step (4) obtains a three-dimensional ordered macroporous structure Ni 2 P catalyst.

[0068] Example 5

[0069] This embodiment is exactly the same as embodiment 1, except that in step (3), the concentration of Ce is 0.83 mol / L, and no Ni is added to obtain a three-dimensional ordered macroporous structure CeO 2 ; Step (4) obtains a three-dimensional ordered macroporous structure CeO 2 catalyst.

[0070] The Ni prepared in Example 1-5 2 P / CeO 2The catalyst was electrochemically tested, using the OER catalytic oxidation experiment as the reaction model. The preparation and specific testing steps of the OER working electrode were as follows:

[0071] (1) Take 3 mg Ni 2 P / CeO 2 -x catalyst was added to 290 μL of 50% ethanol aqueous solution, followed by 10 μL of naphthol solution (5 wt.%). After ultrasonication for 15 min, a uniform electrode slurry was obtained. 100 μL of the above slurry was taken out and dropped on a hydrophilic carbon paper (1 cm×1 cm, 1 mg cm -2 ), and after drying, Ni 2 P / CeO 2 -x electrode pads.

[0072] (2) The test was carried out on a CHI 760E workstation (Shanghai Chenhua Instrument Co., Ltd.) using a standard three-electrode system. The working electrode was Ni 2 P / CeO 2 -x electrode sheet, the reference electrode is Ag / AgCl electrode (filled with 1.0M KCl solution), and the counter electrode is a platinum electrode (1cm×1cm). The electrolyte is 1.0M KOH. In the present invention, linear sweep voltammetry (LSV) is used to test the electrochemical performance, and the final data are converted into the standard reversible hydrogen electrode potential (E RHE ):

[0073] E RHE =E Ag / AgCl +0.059×pH+0.2223V

[0074] Depend on Figure 1 It can be seen that the phase is composed of hexagonal crystal structure Ni 2 P and cubic fluorite CeO 2 composition, indicating the successful synthesis of the catalyst.

[0075] Depend on Figure 2 It can be seen that the synthesized catalyst has a three-dimensional macroporous structure with uniform and orderly pores, and the average pore size of the macropores is about 140-160nm.

[0076] Depend on Figure 3 It can be seen that there is an obvious interface between the two phase compounds, and the lattice spacing of 0.22nm and 0.31nm represents Ni 2 P and CeO 2 The (111) crystal plane of the heterostructure was successfully synthesized.

[0077] Depend on Figure 4 It can be seen that the catalysts with different Ni and Ce ratios exhibit different catalytic activities.2 P / CeO 2 -10 performs best, surpassing commercial RuO 2 Catalyst performance.

[0078] Depend on Figure 5 It can be seen that compared with the single-phase catalyst, the heterojunction catalyst Ni 2 P / CeO 2 -10 exhibits the fastest reaction kinetics, indicating that heterojunction engineering and pore structure engineering can synergistically accelerate electron transport during the OER process.

[0079] Depend on Figure 6 It can be seen that after OER test, Ni 2 P will partially reconstruct into amorphous NiOOH in situ, and this NiOOH will participate in the electrochemical reaction as a real active site.

[0080] Depend on Figure 7 Confirmed again 2 P is self-optimized to NiOOH, and the in-situ Raman spectrum is approximately 1050 cm -1 The location shows PO 4 3- Characteristic peaks accompanied by some oxygen vacancies (V o ) is generated.

[0081] The above results show that Ni 2 P / CeO 2 -x catalyst has a "liberalization effect" and can participate in the reaction as a pre-catalyst. During the OER reaction, the pre-catalyst is in situ self-optimized to PO 4 3+ -NiOOH / CeO 2 _V o structure, achieving higher catalytic activity.

[0082] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A method for preparing a nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure, characterized in that: The method comprises the following steps: (1) Preparation of MMA microsphere emulsion: After deionized water and MMA are uniformly mixed, they are heated to the reaction temperature in an oxygen-free environment. After the temperature stabilizes, an initiator is added and stirred to react until the solution becomes a milky emulsion to obtain an MMA microsphere emulsion; (2) Preparation of PMMA template microspheres: The MMA microsphere emulsion of step (1) is subjected to low-speed centrifugation to remove the supernatant and take out the middle layer emulsion; the middle layer emulsion is then mixed with deionized water, and then subjected to low-speed centrifugation to remove the supernatant and take out the middle layer emulsion; after repeating the mixing and low-speed centrifugation process at least 3 times, the middle layer emulsion obtained is a mixed emulsion with uniform PMMA particle size; the mixed emulsion is then subjected to high-speed centrifugation to arrange the microspheres, and the PMMA template microspheres are obtained after drying; (3) Preparation of NiO / CeO2: Methanol, ethylene glycol, concentrated nitric acid and deionized water are mixed uniformly to obtain a mixed solvent; cerium salt, nickel salt and pore-forming agent are dissolved in the mixed solvent to obtain a mixed solution; PMMA template microspheres of step (2) are added to the mixed solution and allowed to stand until the gaps of the PMMA template microspheres are completely filled with the mixed solution, and solid products are collected by filtration; the solid products are calcined to remove the PMMA template microspheres to obtain NiO / CeO2; (4) Preparation of Ni2P / CeO2 catalyst: NiO / CeO2 and a phosphorus source are placed in an oxygen-free environment, and phosphine gas is carried to NiO / CeO2 by continuously introducing an inert gas or nitrogen gas for phosphation reaction. After the reaction is completed, a black product, namely a nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure, is obtained.

2. The method for preparing the nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure according to claim 1, characterized in that: In step (1), the volume ratio of deionized water to MMA is 34:4-5; In step (1) and step (4), the oxygen-free environment is an inert gas environment or a nitrogen environment; In step (1), the reaction temperature is 75-85° C. and the reaction time is 45-60 min.

3. The method for preparing the nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure according to claim 1, characterized in that: In step (1), the initiator is a potassium persulfate solution; In step (1), the concentration of the potassium persulfate solution is 3.8-5.7 mol / L; the molar ratio of potassium persulfate to MMA is 1:170-255.

4. The method for preparing the nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure according to claim 1, characterized in that: In step (2), the low-speed centrifugation process is: centrifugation at 2500-3000 rpm for 0.5-1 h; In step (2), the mixing is carried out by ultrasonic treatment; the ultrasonic treatment temperature is 20 to 30° C., the power is 220 to 250 W, and the time is 0.5 to 1 h; In step (2), the volume ratio of deionized water to supernatant is 1:1 to 1.5; In step (2), the ultrasonic treatment and low-speed centrifugation process are repeated 3 to 5 times; In step (2), the high-speed centrifugation process is: centrifugation at 5500-6000 rpm for 3-4 hours.

5. The method for preparing the nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure according to claim 1, characterized in that: In step (2), the particle size of the PMMA template microspheres is 220 to 280 nm.

6. The method for preparing the nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure according to claim 1, characterized in that: In step (3), the volume ratio of methanol, ethylene glycol, concentrated nitric acid and deionized water is 7:1 to 2:1:10; In step (3), the cerium salt is Ce(NO3)3, Ce(NO3)3·6H2O, CeCl3 and CeCl3·6H2O; the nickel salt is Ni(NO3)2, Ni(NO3)2·6H2O, NiCl2 and NiCl2·6H2O; and the pore-forming agent is ascorbic acid; In step (3), in the mixed solution, the total concentration of the cerium salt and the nickel salt is 0.7-0.9 mol / L, and the ratio between the two is arbitrary; the concentration of the pore-forming agent is 0.7-0.8 mol / L.

7. The method for preparing the nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure according to claim 1, characterized in that: In step (3), the standing time is 2 to 3 hours; the filtration time is 1 to 2 hours; In step (3), the calcination temperature is 350-400°C, the time is 4-5h, and the heating rate is 1-1.5°C / min.

8. The method for preparing the nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure according to claim 1, characterized in that: In step (4), the flow rate of the inert gas or nitrogen is 0.05 to 0.2 NI / min; In step (4), the temperature of the phosphating reaction is 350-400° C., the reaction time is 120-150 min, and the heating rate is 1.5-2° C. / min.

9. The method for preparing the nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure according to claim 1, characterized in that: In step (4), the mass ratio of the phosphorus source to NiO / CeO2 is 60:1-2; In step (4), the phosphorus source is sodium hypophosphite and potassium hypophosphite.

10. The method for preparing the nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure according to claim 1, characterized in that: Step (4) is specifically as follows: placing NiO / CeO2 and a phosphorus source in two containers that are resistant to high temperatures and do not react with the NiO / CeO2; placing the NiO / CeO2 at the airflow outlet of a closed heating environment at normal pressure, placing the phosphorus source at the airflow inlet, and purging with an inert gas or nitrogen to form an oxygen-free environment; then, at normal pressure, heating the tubular furnace to 350-400°C at a heating rate of 1.5-2°C / min in an inert gas or nitrogen atmosphere with a constant flow rate of 0.05-0.2NI / min, and the phosphine gas generated by the decomposition of the phosphorus source is carried by the inert gas or nitrogen to the NiO / CeO2 for a phosphating reaction for 120-150 minutes; after the reaction is completed, the NiO / CeO2 is naturally cooled to room temperature to obtain a nickel phosphide / cerium dioxide catalyst with a three-dimensional ordered macroporous structure.

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