An enzyme-mimic CeO2-based multi-active-site catalyst, a preparation method and application thereof, an electrolytic cell and a battery

Abstract

The present application relates to an enzyme-like CeO2-based multi-active site catalyst and a preparation method and application thereof, an electrolytic cell and a battery. The present application synthesizes CeO2 nanorods through hydrothermal and high-temperature pyrolysis, and then anchors metal ions to the surface of the CeO2 nanorods through strong carrier interaction; synthesizes metal nanoclusters and nanoparticles with specific sizes, and then obtains an enzyme-like nanocatalyst through a chemical vapor deposition reaction with sodium hypophosphite, which has multiple active sites. The multi-active site catalyst material of the present application has high selectivity, ammonia production efficiency and Faraday efficiency for nitrate reduction when used as a cathode. When used as an anode, in an alkaline water electrolysis reaction, the overpotential is 288 mV at a current density of 50 mA / cm 2 2, which is much better than a commercial RuO2. Based on excellent oxidation and reduction performance, the zinc nitrate battery of the present application has high power density, ammonia production rate and good charge-discharge cycle stability, and can simultaneously remove nitrate, produce ammonia and supply power.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical catalysts, in particular to a kind of nanozyme CeO2 Load X (X=Fe, Co, Cu or Mn) Nanocluster and X (X=Fe, Co, Cu or Mn) Doped Nickel Phosphide Nanoparticle Multi-active Site Catalyst and its preparation method and application. BACKGROUND

[0002] Green power-driven electrochemical nitrate ammonia production is a sustainable ammonia production path, which can avoid the high energy consumption and high carbon dioxide emission problems of the traditional Haber-Bosch process for synthesizing ammonia. However, the nitrate electrocatalytic ammonia production process involves an eight-electron and nine-proton reaction, and the anode oxygen evolution (OER) reaction involves a complex four-electron transfer process, resulting in slow kinetics and high overpotential (1.23 eV), which seriously restricts its industrial application. In order to improve the efficiency of electrocatalytic ammonia production and reduce the energy barrier of the reaction, it is urgent to develop low-cost, high-efficiency and stable multi-active site functional catalyst materials to address the high adsorption energy and activation energy problems caused by the kinetic mismatch between single active site and different intermediates.

[0003] Currently, commercial catalyst materials are mainly platinum group metals and their oxides. However, the scarcity of noble metal materials and the high cost limit their large-scale practical application. In recent years, research on low-cost catalyst materials has mainly focused on non-noble metal sulfides, nitrides and phosphides, which often have excellent platinum-like electrocatalytic performance. However, the single crystal phase exhibits specific electronic structure and physical and chemical properties, which limits its application in electrocatalysis. It has been reported that doping with transition metal element Fe can effectively regulate the electronic structure of Ni2P and serve as a new active site to participate in electrocatalytic reactions. Patent publication CN109201094 B reports the application of porous nanoflower-like Ni2P material in OER. Patent publication CN 113061929 A reports the application of doped nickel phosphide iron three-site ultrathin nanosheet material in overall water splitting.

[0004] However, this Ni2P metal-doped material based on Ni2P metal-doped material has the following problems in practical application: first, it has not found a suitable attachment matrix, which makes its processing cost and use cost high; second, the material activity is insufficient, and the problems of low power of zinc nitrate battery, small ammonia production current, low ammonia yield and poor stability have not been well solved.

[0005] Therefore, in order to meet the high-efficiency ammonia production Faraday efficiency, high ammonia yield and good charge-discharge stability of zinc nitrate battery, it is urgent to develop a nanozyme electrocatalyst with excellent electrocatalytic nitrate reduction performance and OER activity. SUMMARY

[0006] Therefore, the present application aims to overcome the deficiencies in the prior art, and provides an enzyme-mimicking CeO2-based multi-active site catalyst, a preparation method and application thereof, an electrolytic cell and a battery. Specifically, the present application anchors ultrafine X (X=Fe, Co, Cu or Mn) nanoclusters and X (X=Fe, Co, Cu or Mn) doped Ni2P nanoparticles on the substrate of CeO2, exhibits excellent nitrate ammonia and OER performance, and excellent zinc nitrate battery performance.

[0007] To achieve the above-mentioned purpose, the present application first provides an enzyme-mimicking CeO2-based multi-active site catalyst, wherein CeO2 nanorods load X nanoclusters and X doped Ni2P nanoparticles, and X is Fe, Co, Cu or Mn.

[0008] In a preferred embodiment, the total mass of X is 0.1% to 50% of CeO2; the mass of Ni2P is 0.1% to 50% of CeO2.

[0009] The present application also provides a preparation method of an enzyme-mimicking CeO2-based multi-active site catalyst, which comprises the following steps:

[0010] Step 1: uniformly mix cerium salt and ammonia water, obtain CeO2 nanorods by one-step hydrothermal method, centrifugal washing, vacuum drying and air atmosphere heat treatment;

[0011] Step 2: uniformly stir the aqueous solution of X salt, nickel salt, reducing material and template material to obtain a mixed solution; wherein the X salt is iron salt, cobalt salt, copper salt or manganese salt;

[0012] Step 3: add the CeO2 nanorods obtained in step 1 to the mixed solution of step 2, and use the strong interaction of the metal carrier to anchor the metal ions on the CeO2 nanorods to form a precursor;

[0013] Step 4: obtain CeO2 nanorod loaded X nanoclusters and X doped Ni2P nanoparticles by sodium hypophosphite phosphating reaction of the precursor synthesized in step 3;

[0014] When the iron salt is used in step 2, a multi-active site Fe-Fe x Ni 2-x P / CeO2 biomimetic nanoscale enzyme electrocatalyst is obtained.

[0015] Or, when the cobalt salt is used in step 2, a multi-active site Co-Co x Ni 2-x P / CeO2 biomimetic nanoscale enzyme electrocatalyst is obtained.

[0016] or, when the copper salt is used in step 2, a Cu-Cu x Ni 2-x P / CeO2 biomimetic nanoscale enzyme electrocatalyst;

[0017] or, when the manganese salt is used in step 2, a Mn-Mn x Ni 2-x P / CeO2 biomimetic nanoscale enzyme electrocatalyst.

[0018] In the preferred embodiment, in the step 1 of synthesizing the CeO2 nanorod, the cerium salt is at least one of nitrate, chloride or sulfate; the synthesis of the CeO2 nanorod in step 1 is carried out in an alkaline environment with pH=10~14;

[0019] The temperature of the hydrothermal reaction is 100~200 degrees, and the duration is 5~30 hours; the air atmosphere heat treatment temperature is 300~700 degrees, and the time is 1~10 hours;

[0020] In step 2, the iron salt and the nickel salt are at least one of nitrate, chloride or sulfate;

[0021] The reducing material is at least one of sodium citrate, glucose, ethylene glycol or glycerol; the template material is at least one of hexamethylene tetramine, polyvinylpyrrolidone or ethylenediamine;

[0022] In step 4, the reaction temperature of the phosphating reaction is 200-300 degrees, and the reaction time is 1~5 hours.

[0023] In the preferred embodiment, the adding amount of the reducing material is 0.1%~50% of the cerium salt; the adding amount of the template material is 1~10 times of the cerium salt; the adding amount of sodium hypophosphite is 1%~300% of the cerium oxide; the adding amount of the nickel salt is 1~10 times of the cerium oxide; and the adding amount of the X salt is 1%~300% of the cerium oxide.

[0024] The multi-active site Fe-Fe x Ni 2-x In the preparation method of the multi-active site Fe-Fe

[0025] (1) In the above step 1, under the premise of mixing the cerium salt and ammonia water, the alkaline environment (pH: 10~14) can induce the directional growth of the crystal, and the rod-shaped structure is obtained, i.e. the CeO2 nanorod of the present application is obtained;

[0026] (2) In step 3 above, after the iron salt and the nickel salt are placed in the mixed solution containing CeO2 nanorods, under the action of the reduction material and the template material, the surface of CeO2 can be activated, and the adsorption of metal ions can be driven, and the key is to regulate the proportion of metal ions, so that the controllable growth of nanoclusters and nanoparticles can be realized.

[0027] (3) In step 4 above, the prepared cerium-based X nanoclusters and X-doped Ni2P nanoparticle composite materials are subjected to a gas phase deposition reaction by sodium hypophosphite, and a multi-active site X-X x Ni 2-x P / CeO2 biomimetic nanoscale enzyme electrocatalyst.

[0028] According to the multi-active site Fe-Fe x Ni 2-x The preparation method of the P / CeO2 biomimetic nanoscale enzyme electrocatalyst optimizes the adsorption configuration of the nitrogen-containing intermediate and the water splitting rate by designing a multi-active center site, reduces the energy barrier of nitrate reduction to ammonia and improves the hydrogenation rate of the nitrogen-containing intermediate, thereby improving the selectivity and yield of electrocatalytic ammonia production.

[0029] The application further provides a use of the above-mentioned enzyme-mimicking CeO2-based multi-active site catalyst as a cathode material for electrolysis of nitrate to produce ammonia.

[0030] The application further provides a use of the above-mentioned enzyme-mimicking CeO2-based multi-active site catalyst as an anode material for an alkaline electrolytic cell.

[0031] The application further provides a nitrate-based electrolytic cell, which comprises an anode material, a cathode material and a reference electrode; the cathode material uses the above-mentioned enzyme-mimicking CeO2-based multi-active site catalyst, the reference electrode is a mercury / mercury oxide electrode, and the anode material is a Pt sheet.

[0032] The application further provides an alkaline electrolytic cell, which comprises an anode material, a cathode material and a reference electrode; the anode material uses the above-mentioned enzyme-mimicking CeO2-based multi-active site catalyst, the reference electrode is a mercury / mercury oxide electrode, and the cathode material is a Pt sheet.

[0033] The application further provides a zinc nitrate battery, which comprises a positive electrode material and a negative electrode material; the positive electrode material uses the above-mentioned enzyme-mimicking CeO2-based multi-active site catalyst, and the negative electrode material is a zinc sheet.

[0034] The application uses the above technical solution, and has the following advantages compared with the prior art:

[0035] 1.The CeO2 nanorod is used as a substrate in the application, metal ions in the mixed solution are anchored on the surface of the CeO2 nanorod through strong mutual interaction of the metal carrier, and under the action of the reduction material and the template material, synthesis of ultrafine X nanoclusters and X doped Ni2P nanoparticle materials with high activity, high stability, low cost and controllable morphology is realized. x Ni 2-x P / CeO2, Co-Co x Ni 2-x P / CeO2, Cu-Cu x Ni 2-x P / CeO2 and Mn-Mn x Ni 2-x P / CeO2.

[0036] 2.The prepared multi-active-site ultrafine X (X=Fe, Co, Cu or Mn) nanoclusters and X (X=Fe, Co, Cu or Mn) doped Ni2P nanoparticle materials effectively increase the number of active centers, optimize the adsorption configuration of nitrogen-containing intermediates, and reduce the reaction barrier of electrocatalytic nitrate to ammonia.

[0037] 3.The multi-active-site Fe-Fe x Ni 2-x P / CeO2 biomimetic nanoscale enzyme electrocatalyst provided by the application can be used as a cathode material for electrolysis of nitrate to ammonia, and can realize industrial current density ammonia production application. In a 1 mol / L KOH and 0.5 mol / L KNO3 solution, at a potential of-0.7 V vs. RHE, a faradic efficiency of 91.2% and an ammonia yield as high as 43.76 mgh -1 cm -2 are achieved.

[0038] 5.The multi-active-site Fe-Fe x Ni 2-x P / CeO2 biomimetic nanoscale enzyme electrocatalyst provided by the application can be used as an anode material for alkaline electrolysis. In the OER reaction, when the current density is 50 mA / cm 2 , the overpotential is only 288 mV, which is much better than the commercial noble metal material RuO2.

[0039] 6.The multi-active-site Fe-Fe x Ni 2-x P / CeO2 biomimetic nanoscale enzyme electrocatalyst provided by the application can be used as a positive electrode material for zinc nitrate batteries, and can simultaneously realize nitrate to ammonia and power output. Notably, the maximum power density of the assembled battery can reach 21.1 mW / cm 2Therefore, the multi-active site Fe-Fe x Ni 2-x The P / CeO2 biomimetic nanoscale enzyme electrocatalyst has great economic value.

[0040] 7. Similarly, the material Co-Co x Ni 2-x P / CeO2, Cu-Cu x Ni 2-x P / CeO2 and Mn-Mn x Ni 2-x P / CeO2 also has similar properties to Fe-Fe x Ni 2-x P / CeO2 similar properties, which are compared in the following data. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings required to be used in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0042] Figure 1 X-ray diffraction (XRD) patterns of the present application Example 1, Comparative Example 1, Comparative Example 2, experimental product CeO2, standard card Ni2P (PDF #21-0590), standard card CeO2 (PDF #34-0394) corresponding to;

[0043] Figure 2 Multi-active site Fe-Fe x Ni 2-x P / CeO2 biomimetic nanoscale enzyme electrocatalyst high-resolution transmission electron microscopy (HR-TEM) image provided by the present application Example 1;

[0044] Figure 3 Linear sweep voltammetry (LSV) curves of the present application Example 1, Comparative Example 1 and Comparative Example 2 in 1 mol / L KOH and 0.5 mol KNO3 mixed solution;

[0045] Figure 4 Multi-active site Fe-Fe x Ni 2-x P / CeO2 biomimetic nanoscale enzyme electrocatalyst Faraday efficiency and ammonia yield of electrocatalytic nitrate to ammonia at-0.4 V vs. RHE potential cycle 16 times provided by the present application Example 1;

[0046] Figure 5 LSV plots for Example 1 of the present invention, Comparative Example 1 and Comparative Example 2 in 1 mol / L KOH;

[0047] Figure 6 Multi-active site Fe-Fe x Ni 2-x Discharge curves and corresponding power density plots of the zinc nitrate batteries assembled with P / CeO2 biomimetic nanoszyme electrocatalysts;

[0048] Figure 7 Multi-active site Fe-Fe x Ni 2-x Discharge and charge plots of the zinc nitrate batteries assembled with P / CeO2 biomimetic nanoszyme electrocatalysts at 3 mA / cm 2 Constant current density. DETAILED DESCRIPTION

[0049] The present invention will be further described in details with reference to the accompanying drawings, tables and specific experimental procedures, which can be easily understood by those skilled in the art according to the present specification. It is worth noting that, if not otherwise specified, all are conventional methods, and the instruments and materials can be commercially available.

[0050] The end point values of the ranges described in the present specification are not limited to the exact ranges or values, and the ranges should be understood to include values close to the ranges. For the specific synthesis procedures, it should be the combination of individual points within each range to obtain one or more procedures, and the values should be considered as specifically disclosed in the present patent.

[0051] Example 1:

[0052] A low-cost multi-active site Fe-Fe x Ni 2-x The preparation method of the P / CeO2 biomimetic nanoszyme electrocatalyst comprises the following steps:

[0053] CeCl3·7H2O as a material for synthesizing CeO2 nanorods, NaH2PO2·H2O as a raw material; 25% NH3·H2O is selected as a modifier for synthesizing CeO2 nanorods, wherein the amount of NH3·H2O is 20% of CeCl3·7H2O; Ni(NO3)2·6H2O and Fe(NO3)3·6H2O are selected as raw materials for preparing Fe-Fe x Ni 2-x The raw materials of the P / CeO2 biomimetic nanoszyme electrocatalyst.

[0054] Preparation of CeO2 nanorods:

[0055] CeCl3·7H2O 6.93%, ultrapure water 74.45%, NH3·H2O 18.62% by mass percentage, after stirring at 1000 rpm for 1 hour, transferred to a hydrothermal reactor, 180 degrees for 24 hours, using a mixture of ultrapure water and ethanol (volume ratio 1:1), washed by centrifugation 5 times, vacuum dried at 60 degrees, transferred to a muffle furnace and heat treated at 600 degrees for 4 hours, to obtain CeO2 nanorods.

[0056] Fe-Fe x Ni 2-x Synthesis of P / CeO2 biomimetic nanoscale enzyme electrocatalyst:

[0057] Fe-Fe x Ni 2-x The specific details of the synthesis of P / CeO2 biomimetic nanoscale enzyme electrocatalyst are as follows: 0.6684 g of the above-prepared CeO2 nanorods were dispersed in 30.0 mL of ultrapure water, then 0.291 g of sodium citrate, 4.2 g of hexamethylenetetramine, 2.9 g of Ni(NO3)2·6H2O and 0.404 g of Fe(NO3)3·6H2O were added to the solution, and stirred at 600 rpm for 30 minutes to form a uniform solution. Subsequently, the mixed solution was heated in an 80-degree oil bath for 5 hours, and stirred at 400 rpm. The resulting precipitate was washed with ultrapure water and anhydrous ethanol by centrifugation 3 times, then dried in a vacuum oven at 60 degrees, to obtain FeNi / CeO2. 0.15 g of FeNi / CeO2 and 0.5 g of NaH2PO2·H2O were placed in separate corundum magnetic boats. NaH2PO2·H2O is located upstream of the double-temperature-zone tube furnace, while FeNi / CeO2 is located downstream. Under a nitrogen atmosphere, the temperature was raised to 300 degrees at a rate of 2 degrees / minute and held for 2 hours, then naturally cooled to room temperature, to obtain multi-active site Fe-Fe x Ni 2- x P / CeO2 electrocatalytic material.

[0058] The multi-active site Fe-Fe x Ni 2-x X-ray diffraction pattern (XRD) of the P / CeO2 biomimetic nanoscale enzyme electrocatalyst prepared in this example is shown in Figure 1 From the figure, it can be observed that the prepared Fe-Fe x Ni 2-xThe diffraction peaks of the P / CeO2 biomimetic nanozyme electrocatalyst correspond to those of the experimental product CeO2, and compared with the standard card CeO2 (PDF #34-0394) and Ni2P (PDF #21-0590), no other extra peaks are found, and no Fe-based and Ni-based diffraction peaks can be observed, indicating that the ultrafine Fe nanoclusters and nanoparticles with Fe-doped Ni2P are successfully prepared; at the same time, by Figure 2 It can be observed from the HR-TEM image that the crystal face spacing of 0.195 nm corresponds to the (111) crystal face of CeO2, and the surface of the CeO2 nanorod is distributed with ultrafine Fe nanoclusters with a size of about 1.8 nm and nanoparticles with a size of about 10.0 nm, wherein the crystal lattice spacing of the nanoparticles is 0.208 nm, which is smaller than the (111) crystal face spacing of Ni2P (0.222 nm), indicating that the lattice strain caused by the Fe doping into the Ni2P lattice, and the surface layer is amorphous CeO2.

[0059] Example 2:

[0060] Electrocatalytic nitrate reduction test:

[0061] Preparation of working electrode: 2.0 mg of the catalytic material prepared in Example 1 was dispersed in a mixed solution containing 200 ul of perfluorosulfonic acid-based polymer (Nafion 117), 1.6 mL of water and 3.2 mL of isopropyl alcohol, and then ultrasonic treatment was performed for 1 hour to obtain a uniform slurry. The slurry was uniformly coated on a 0.2 cm 2 clean carbon paper with a loading of 1 mg / cm 2 , and dried as a working electrode using an infrared lamp.

[0062] The performance of the working electrode in Example 1 was tested using a CHI760E electrochemical workstation of Shanghai Chenhua Instrument Co., Ltd. A three-electrode system H-type electrolytic cell was used, and the anode chamber and the cathode chamber were separated by an anion exchange membrane (FAA-3-PK-130). Hg / HgO was used as the reference electrode, Pt sheet was used as the counter electrode, and the carbon paper coated with the above-prepared catalytic material was used as the working electrode. The electrolyte was 30 mL of a mixed solution of 1.0 mol / L KOH and 0.5 mol / L KNO3, and all the electrochemical tests were performed under the blowing environment of Ar gas. Before the electrocatalytic nitrate reduction test, the electrolyte was purged with Ar gas for 30 minutes to remove the air in the solution.

[0063] The specific details of the test are as follows: first, activate to stability by cyclic voltammetry (CV) from +0.1 V to -1.0 V vs. RHE for 50 cycles, and then test by linear sweep voltammetry from 0 V to -1.0 V vs. RHE, with a scan rate of 5 mv / s, and record the ammonia current density atFigure 3 , the ammonia current density reached 287.5 mA / cm 2 At last, the chronoamperometry method was used to test the ammonia production performance of the catalyst under different potentials. The electrolyte after the reaction was collected, and the corresponding Q value was recorded.

[0064] The measured potential was corrected to the reversible hydrogen electrode by the following formula:

[0065] E RHE = E Hg / HgO + 0.059*pH +0.098 V (1);

[0066] E Hg / HgO is the actual implementation potential, E RHE is the relative potential of the reversible hydrogen electrode.

[0067] Ammonia product detection: The collected electrolyte was first diluted with a mixed solution of 1.0 mol / L KOH and 0.5 mol / L KNO3, and then neutralized and diluted with a mixed solution of 0.5 mol / L H2SO4 and 0.5 mol / L KNO3, and then the indigo blue method was used to quantitatively determine the concentration of ammonia. Specifically, the absorption spectrum of the obtained solution in the range of 500 nm to 800 nm and the absorbance at 655 nm were measured by a UV-3900 ultraviolet visible spectrophotometer produced by Hitachi Company, Japan, and the concentration was quantitatively determined by the standard curve of ammonia. Table 2 below is the ammonia yield and ammonia Faraday efficiency of the electrocatalytic material for ammonia production from nitrate at -0.7 V vs. RHE, and the ammonia Faraday efficiency is as high as 91.2%, and the ammonia yield is 43.5 mg h -1 cm -2 , showing excellent electrocatalytic performance for ammonia production from nitrate.

[0068] Example 3:

[0069] Different from Example 2, the Fe-Fe x Ni 2-x P / CeO2 biomimetic nanoscale enzyme electrocatalyst was tested for 16 cycles at -0.4 V vs. RHE. Figure 4 The results show that the ammonia production Faraday efficiency of the catalyst material is maintained at about 90%, further showing good stability.

[0070] Example 4:

[0071] Different from Example 2, the prepared catalyst was used as an anode in the electrocatalytic OER reaction (oxygen evolution reaction).

[0072] Specific details are as follows: based on Fe-Fex Ni 2-x The working electrode was prepared according to the same method of the cathode working electrode. A single electrolytic cell with a three-electrode system was used, with Hg / HgO as the reference electrode and a Pt sheet as the counter electrode. The Fe-Fe x Ni 2-x The P / CeO2bionic nanoscale enzyme electrocatalyst-coated carbon paper was used as the working electrode anode. The electrolyte was 100 mL of 1.0 mol / L KOH solution. Before the electrocatalytic OER test, the working electrode was first activated by cyclic voltammetry (CV) from +1.0 V to 1.8 V vs. RHE for 50 cycles, and then linear voltammetry was performed at a scan rate of 5 mV / s, with a scan potential range of 1.0 V to 1.8 V vs. RHE. The recorded OER current density curve is shown in Figure 5 , the current density of the catalyst was 50 mA / cm 2 , and the overpotential was only 288 mV, which was much better than the performance of the commercially available RuO2, indicating excellent OER performance.

[0073] Example 5:

[0074] Application of zinc nitrate batteries:

[0075] Battery assembly: Fe-Fe x Ni 2-x The excellent nitrate ammonia production and OER performance of the P / CeO2bionic nanoscale enzyme electrocatalyst was prepared according to the method of Example 2 above to prepare the working electrode as the positive electrode, and a zinc sheet with a thickness of 5 mm as the negative electrode; the electrolyte of the positive electrode was a mixed solution of 30 mL of 1.0 mol / L KOH and 0.5 or 1.0 mo / L KNO3, and the electrolyte of the negative electrode was a mixed solution of 1.0 mol / L KOH and 0.02 mo / L (CH3COO)2Zn. The positive electrode and the negative electrode were separated by an anion exchange membrane (FAA-3-PK-130).

[0076] The electrochemical workstation CHI760E was used to first test the performance of the zinc nitrate battery, and the discharge curve and power density were Figure 6 , in 1.0 M KOH and 0.5 M potassium nitrate solution, the Fe-Fe x Ni 2-x The maximum power density of the P / CeO2bionic nanoscale enzyme electrocatalyst was as high as 21.1 mW / cm 2 .

[0077] Example 6:

[0078] Zinc nitrate battery charge-discharge stability test:

[0079] The difference between this embodiment and embodiment 5 is that the assembled zinc nitrate battery is subjected to long-term charge-discharge cycle test evaluation at 3 mA / cm 2 The working curve is recorded as shown in Figure 7 The cycle stability reaches 8 hours.

[0080] Embodiment 7:

[0081] A low-cost multi-active-site Co-Co x Ni 2-x The preparation method of the P / CeO2 biomimetic nano-enzyme electrocatalyst comprises the following steps:

[0082] The difference between embodiment 7 and embodiment 1 is that equal-molar Co(NO3)2·6H2O is used to replace Fe(NO3)3·6H2O in the mixed solution, and the rest of the preparation process and steps are the same as those of embodiment 1.

[0083] Embodiment 8:

[0084] The sample of embodiment 7 is subjected to electrocatalytic nitrate reduction test in the manner of embodiment 2, and the ammonia current density is recorded. The ammonia current density at different potentials is shown in Table 1, and the current density at a potential of-0.7 V vs. RHE can approach 500 mA / cm 2 , which realizes the industrial-level current density standard. Further, the sample of embodiment 7 is subjected to constant-current nitrate reduction for ammonia production test at different potentials in the manner of embodiment 2, and the ammonia yield and ammonia Faraday efficiency of the electrocatalytic material at different potentials are recorded. As shown in Table 2 below, the ammonia Faraday efficiency of the sample of embodiment 7 at a voltage of-0.7 V vs. RHE reaches 90.4%, and the ammonia yield is 42.7 mg h -1 cm -2 .

[0085] Further, the sample of embodiment 7 is subjected to electrocatalytic OER performance test in the manner of embodiment 4. As shown in Table 3, the overpotential of the sample of embodiment 7 at 50 mA / cm 2 is 296 mV, and the actual OER performance is better than that of the prior art commercial RuO2.

[0086] Further, the sample of embodiment 7 is subjected to zinc nitrate battery assembly in the manner of embodiment 5, and the difference between embodiment 7 and embodiment 5 is that the sample of embodiment 7 is used as the positive electrode of the battery. In a 1.0 M KOH and 0.5 M potassium nitrate solution, the maximum power density of the sample of embodiment 7 is 19.3 mW / cm 2 .

[0087] Embodiment 9:

[0088] A low-cost, multi-active-site Cu-Cu x Ni 2-x Preparation method of P / CeO2 biomimetic nanozyme electrocatalyst.

[0089] Unlike Example 1, in Example 9, an equimolar amount of Cu(NO3)2·3H2O was added to the mixed solution instead of Fe(NO3)2·6H2O, and the rest of the preparation process and steps were the same as in Example 1.

[0090] Example 10:

[0091] The sample from Example 9 was subjected to electrocatalytic nitrate reduction testing as described in Example 2, and the ammonia current density was recorded. As shown in Table 1, the sample from Example 9 exhibited the highest ammonia current density of 654.3 mA / cm² at a potential of -0.7 V vs. RHE. 2 Furthermore, the sample from Example 9 was subjected to constant-current nitrate reduction to ammonia production at different potentials, following the method described in Example 2. The ammonia yield and ammonia Faradaic efficiency of the electrocatalytic material at different potentials were recorded. As shown in Table 2, at a voltage of -0.7 V vs. RHE, its ammonia production Faradaic efficiency exceeded 95%, and the ammonia yield was 47.6 mg h⁻¹. -1 cm -2 .

[0092] Furthermore, the electrocatalytic OER performance of the sample from Example 9 was tested according to the method described in Example 4. As shown in Table 3, the sample from Example 9 achieved an OER performance of 50 mA / cm². 2 The overpotential was 373 mV. This indicates that Example 9 could not simultaneously achieve both excellent electrocatalytic nitrate to ammonia production and OER reactions.

[0093] Furthermore, the sample from Example 9 was assembled into a zinc nitrate battery according to the method of Example 5. The difference from Example 5 is that the sample from Example 9 was used as the positive electrode of the battery. In a 1.0 M KOH and 0.5 M potassium nitrate solution, the maximum power density of the sample from Example 9 reached as high as 27.3 mW / cm³. 2 However, its charge / discharge performance is limited by the poor OER performance of the sample in Example 9.

[0094] Example 11:

[0095] A low-cost multi-active-site Mn-Mn x Ni 2-x Preparation method of P / CeO2 biomimetic nanozyme electrocatalyst.

[0096] Different from example 1, example 11 replaces Fe(NO3)2·6H2O with equimolar amount of Mn(NO3)2·4H2O in the mixed solution, and the rest of the preparation process and steps are the same as example 1.

[0097] Example 12:

[0098] The sample of example 11 is tested for electrocatalytic nitrate reduction according to the method of example 2, and the ammonia current density is recorded. As shown in Table 1, the current density of example 11 reaches -563.7 mA / cm 2 at a potential of -0.7 V vs. RHE, achieving the standard of industrial current density. Further, the sample of example 11 is tested for constant current nitrate reduction to ammonia at different potentials according to the method of example 2, and the ammonia yield and ammonia Faraday efficiency of the electrocatalytic material for nitrate to ammonia at different potentials are recorded. As shown in Table 2, the ammonia Faraday efficiency of the sample of example 11 is 87.8% and the ammonia yield is 40.8 mg h -1 cm -2 at a voltage of -0.7 V vs. RHE.

[0099] Further, the sample of example 11 is tested for electrocatalytic OER performance according to the method of example 4, and as shown in Table 3, the overpotential of the sample of example 11 is 298 mV at 50 mA / cm 2 .

[0100] Further, the sample of example 11 is assembled into a zinc nitrate battery according to the method of example 5, and the difference from example 5 is that the sample of example 11 is used as the positive electrode of the battery. In 1.0 M KOH and 0.5 M potassium nitrate solution, the maximum power density of the sample of example 11 can reach 15.7 mW / cm 2 .

[0101] Comparative example 1:

[0102] A method for preparing a single active site Ni2P / CeO2 electrocatalytic material, comprising the following steps:

[0103] Different from example 1, no Fe(NO3)2·6H2O is added in comparative example 1, and the rest of the preparation process and steps are the same as example 1.

[0104] Further, comparative example 1 is tested by XRD, and the diffraction peak of the sample is shown in Figure 2. Figure 1As can be seen, the XRD diffraction peaks of the Ni2P / CeO2 electrocatalytic material prepared according to the application correspond to the peaks of the experimental product CeO2, and compared with the standard card CeO2 (PDF #34-0394) and Ni2P (PDF #21-0590), no other peaks are found, and no Ni-based diffraction peaks can be observed, indicating that the nanoparticles of Ni2P are successfully prepared.

[0105] Further, the sample of Comparative Example 1 was subjected to the electrocatalytic nitrate reduction test in the manner of Example 2, and as shown in Table 1, the current density of the sample of Comparative Example 1 at a potential of -0.7 V vs. RHE was only -337.5 mA / cm 2 . Further, the sample of Comparative Example 1 was subjected to the constant current nitrate reduction test at different potentials to prepare ammonia, and the ammonia yield and ammonia Faraday efficiency of the electrocatalytic material at different potentials were recorded. As shown in Table 2, the ammonia Faraday efficiency of the sample of Comparative Example 1 at a voltage of -0.7 V vs. RHE was only 78.9%, and the ammonia yield was 35.8 mg h - 1 cm -2 . The ammonia yield and Faraday efficiency of the sample of Comparative Example 1 were both much lower than those of the multi-active site catalyst, indicating the limitations of such a single active site in the multi-step electrochemical reaction for ammonia production.

[0106] Further, the sample of Comparative Example 1 was subjected to the electrocatalytic OER performance test in the manner of Example 4, and as shown in Table 3, the overpotential of the sample of Comparative Example 1 at 50 mA / cm 2 was 340 mV. The poor OER performance of the sample of Comparative Example 1 further verifies the superiority of the multi-active site catalyst.

[0107] Comparative Example 2:

[0108] A preparation method of a Fe / CeO2 electrocatalytic material, comprising the following steps:

[0109] Different from Example 1, no Ni(NO3)2·6H2O was added in Comparative Example 2, and the rest of the preparation process and steps were the same as those of Example 1.

[0110] Further, Comparative Example 2 was subjected to XRD test, and by Figure 1 As can be seen, the XRD diffraction peaks of the Fe / CeO2 electrocatalytic material prepared according to the application correspond to the peaks of the experimental product CeO2, and compared with the standard card CeO2 (PDF #34-0394) and Ni2P (PDF #21-0590), no other peaks are found, and no Fe-based diffraction peaks can be observed, indicating that the ultrafine Fe nanoclusters are successfully prepared.

[0111] Furthermore, the sample of Comparative Example 2 was subjected to electrocatalytic nitrate reduction testing according to the method of Example 2. As shown in Table 1, the current density of the sample of Comparative Example 2 at a potential of -0.7V vs. RHE was only -265.1mA / cm². 2 Furthermore, the sample of Comparative Example 2 was subjected to constant current reduction of nitrate to ammonia at different potentials, following the method described in Example 2. The ammonia yield and ammonia Faradaic efficiency of the electrocatalytic material at different potentials were recorded. As shown in Table 2, the sample of Comparative Example 2, at a voltage of -0.7 V vs. RHE, exhibited an ammonia Faradaic efficiency of 75.3% and an ammonia yield of 28.5 mg h⁻¹. -1 cm -2 .

[0112] Furthermore, the electrocatalytic OER performance of the sample from Comparative Example 2 was tested according to the method described in Example 4. As shown in Table 3, the sample from Comparative Example 2 performed at 50 mA / cm². 2 The overpotential exceeds 500 mV, which is greater than the overpotential of the multi-active-site biomimetic nanoenzyme electrocatalyst in Example 1.

[0113] The above examples and comparative examples demonstrate the versatility of synthesizing this multi-active-site biomimetic nanozyme electrocatalyst, encompassing nanoclusters and nanoparticles. They also highlight the advantages of this multi-active-site biomimetic nanozyme electrocatalyst in the synergistic tandem catalysis of nitrate-to-ammonia electrocatalysis. Furthermore, electrochemical performance tests and zinc nitrate battery tests confirm the superior performance of the multi-active-site components in the tandem ammonia production and OER reactions, providing a good demonstration for achieving highly efficient and stable biomimetic nanozyme electrocatalysts.

[0114] Table 1:

[0115]

[0116] Table 2:

[0117]

[0118] Table 3:

[0119]

[0120] The results of sample testing obtained from the different embodiments and comparative examples described above are further explained below with reference to the accompanying drawings.

[0121] pass Figure 1 It can be seen that the multi-active-site Fe-Fe prepared using this invention... x Ni 2-xThe XRD diffraction peak of the P / CeO2 biomimetic nano-enzyme electrocatalyst corresponds to the peak of the experimental product CeO2, compared with the standard card CeO2 (PDF #34-0394) and Ni2P (PDF #21-0590), no other peaks are found, and no Fe-based and Ni-based diffraction peaks can be observed, indicating that the ultrafine Fe nanoclusters and nanoparticles with Fe-doped Ni2P are successfully prepared.

[0122] By Figure 2 It can be seen that the multi-active site Fe-Fe x Ni 2-x The P / CeO2 biomimetic nano-enzyme electrocatalyst presents a structure in which Fe nanoclusters coexist with Fe-doped Ni2P nanoparticles on CeO2 nanorods.

[0123] By Figure 3 It can be seen that the multi-active site Fe-Fe x Ni 2-x The P / CeO2 biomimetic nano-enzyme electrocatalyst has a current density as high as 623.5 mA / cm 2 , as shown in Table 1 and Table 2, the multi-active site Fe-Fe x Ni 2-x The P / CeO2 biomimetic nano-enzyme electrocatalyst has an ammonia yield of 43.5 mg h -1 cm -2 , an ammonia faradaic efficiency of 91.2%, and an ammonia current density of an industrial level. At the same time, the same type of multi-active site catalysts all have better ammonia yield and faradaic efficiency than single-phase, highlighting the advantages of this multi-active site nano-enzyme structure in optimizing the adsorption process of nitrogen-containing intermediates in nitrate ammonia production, which is conducive to accelerating the advantages of hydrogenation of nitrogen-containing intermediates to ammonia.

[0124] By Figure 4 It can be seen that the multi-active site Fe-Fe x Ni 2-x The P / CeO2 biomimetic nano-enzyme electrocatalyst can be stably cycled for 16 times at a potential of-0.4 V vs. RHE, achieving stable removal of nitrate while also achieving ammonia production.

[0125] By Figure 5 It can be seen that the multi-active site Fe-Fe x Ni 2-x The P / CeO2 biomimetic nano-enzyme electrocatalyst has a current density of 50 mA / cm 2At current density, it exhibits a lower OER reaction overpotential of 288 mV compared to single-active-site catalytic materials and commercially available RuO2.

[0126] pass Figure 6 It can be seen that the multi-active-site Fe-Fe of the present invention x Ni 2-x The P / CeO2 biomimetic nanozyme electrocatalyst exhibited a maximum power density of 21.1 mW / cm³ in a mixed solution of 1.0 M KOH and 0.5 M KNO₃. 2 .

[0127] pass Figure 7 It can be seen that the multi-active-site Fe-Fe of the present invention x Ni 2-x The P / CeO2 biomimetic nano-enzyme electrocatalyst exhibits good charge-discharge cycle stability at 3 mA / cm². 2 It can operate stably for 8 hours at current density.

[0128] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical solution of the present invention, various simple modifications can be made to the synthesis scheme of the present invention, including but not limited to adjusting the proportion of each additive and combining various suitable methods. These modifications and combinations should be considered as the content disclosed in the present invention and all fall within the protection scope of the present invention.

Claims

1. A method for preparing an enzyme-mimicking CeO2-based multi-active-site catalyst, characterized in that, Includes the following steps: Step 1: Mix cerium salt with ammonia water evenly, and obtain CeO2 nanorods by one-step hydrothermal method, centrifugal washing, vacuum drying, and air atmosphere heat treatment. Step 2: Stir the aqueous solutions of X salt, nickel salt, reducing material and template material evenly to obtain a mixed solution; wherein, X salt is an iron salt, cobalt salt, copper salt or manganese salt; Step 3: By adding the CeO2 nanorods obtained in Step 1 to the mixed solution in Step 2, the strong interaction between the metal and the support is used to anchor the metal ions onto the CeO2 nanorods to form a precursor. Step 4: The precursor synthesized in Step 3 is subjected to sodium hypophosphite phosphating reaction to obtain CeO2 nanorods supported on X nanoclusters and X-doped Ni2P nanoparticles. When iron salts are used in step 2, a multi-active-site Fe-Fe composite is obtained, consisting of CeO2 nanorods supporting Fe nanoclusters and Fe-doped Ni2P nanoparticles. x Ni 2-x P / CeO2 biomimetic nano-enzyme electrocatalyst; Alternatively, when cobalt salts are used in step 2, a multi-active-site Co-Co structure is obtained, consisting of CeO2 nanorods supporting Co nanoclusters and Co-doped Ni2P nanoparticles. x Ni 2-x P / CeO2 biomimetic nano-enzyme electrocatalyst; Alternatively, when copper salt is used in step 2, a Cu-Cu composite with multiple active sites is obtained, consisting of CeO2 nanorods supporting Cu nanoclusters and Cu-doped Ni2P nanoparticles. x Ni 2-x P / CeO2 biomimetic nano-enzyme electrocatalyst; Alternatively, when manganese salt is used in step 2, a multi-active-site Mn-Mn composite is obtained, consisting of CeO2 nanorods supporting Mn nanoclusters and Mn-doped Ni2P nanoparticles. x Ni 2-x P / CeO2 biomimetic nanoenzyme electrocatalyst.

2. The method for preparing the enzyme-mimicking CeO2-based multi-active-site catalyst according to claim 1, characterized in that, In step 1, the CeO2 nanorods are synthesized as follows: the cerium salt is at least one of nitrate, chloride, or sulfate; the synthesis of CeO2 nanorods in step 1 is carried out in an alkaline environment at pH 10-14. The hydrothermal reaction temperature is 100~200 degrees Celsius, lasting 5~30 hours; the air atmosphere heat treatment temperature is 300~700 degrees Celsius, lasting 1~10 hours. In step 2, the X salt and the nickel salt are at least one of nitrate, chloride, or sulfate; The reducing agent is at least one of sodium citrate, glucose, ethylene glycol, and glycerol; the template material is at least one of hexamethylenetetramine, polyvinylpyrrolidone, and ethylenediamine. In step 4, the phosphating reaction is carried out at a temperature of 200-300 degrees Celsius for 1-5 hours.

3. The method for preparing the enzyme-mimicking CeO2-based multi-active-site catalyst according to claim 2, characterized in that, The amount of reducing material added is 0.1% to 50% of the cerium salt; the amount of template material added is 1 to 10 times that of the cerium salt. The amount of sodium hypophosphite added is 1% to 300% of cerium oxide, the amount of nickel salt added is 1 to 10 times that of cerium oxide, and the amount of X salt added is 1% to 300% of cerium oxide.

4. An enzyme-mimicking CeO2-based multi-active-site catalyst obtained by the preparation method according to any one of claims 1-3, characterized in that: CeO2 nanorods loaded with X nanoclusters and X-doped Ni2P nanoparticles, wherein X is Fe, Co, Cu or Mn.

5. The enzyme-mimicking CeO2-based multi-active-site catalyst according to claim 4, characterized in that, The total mass of X is 0.1% to 50% of CeO2; the mass of Ni2P is 0.1% to 50% of CeO2.

6. An application of the enzyme-mimicking CeO2-based multi-active-site catalyst as described in claim 4 or 5 as a cathode material for the electrolysis of nitrate to produce ammonia.

7. An application of the enzyme-mimicking CeO2-based multi-active-site catalyst as described in claim 4 or 5 as the anode material of an alkaline electrolyzer.

8. A nitrate-based electrolytic cell, characterized in that, It includes an anode material, a cathode material, and a reference electrode; the cathode material is an enzyme-mimicking CeO2-based multi-active-site catalyst as described in claim 4 or 5, the reference electrode is a mercury / mercury oxide electrode, and the anode material is a Pt sheet.

9. An alkaline electrolytic cell, characterized in that, It includes an anode material, a cathode material, and a reference electrode; the anode material is an enzyme-mimicking CeO2-based multi-active-site catalyst as described in claim 4 or 5, the reference electrode is a mercury / mercury oxide electrode, and the cathode material is a Pt sheet.

10. A zinc nitrate battery, characterized in that, It includes a positive electrode material and a negative electrode material, wherein the positive electrode material is an enzyme-mimicking CeO2-based multi-active-site catalyst as described in claim 4 or 5, and the negative electrode material is a zinc sheet.

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