Iron-nickel-phosphorus catalyst, preparation method and application thereof, and method for producing aqueous hydrogen peroxide solution through electro-catalysis

Abstract

The invention belongs to the technical field of catalyst preparation, and provides an iron-nickel-phosphorus catalyst, a preparation method and application thereof, and a method for producing an aqueous hydrogen peroxide solution through electro-catalysis. The preparation method comprises the following steps: mixing nickel chloride, ferric chloride, elemental phosphorus and alcohol amine, and carrying out solvothermal reaction to obtain the iron-nickel-phosphorus catalyst. The iron-nickel-phosphorus catalyst containing iron phosphide, nickel phosphide and iron-doped nickel phosphide is obtained by taking a nickel salt, an iron salt, a phosphorus simple substance and a reducing solvent as raw materials and carrying out solvothermal reaction. The iron-nickel-phosphorus catalyst obtained by the invention can efficiently generate hydrogen peroxide through electro-catalysis in an electrolyte with the pH value of 5-9, so that the pH value range of the prepared hydrogen peroxide aqueous solution is wide, and the application range and field are wider; compared with selenium-doped cobalt phosphide in the prior art, the prepared hydrogen peroxide aqueous solution is wider in application.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and particularly relates to an iron-nickel-phosphorus catalyst, a preparation method and application thereof, and a method for electrocatalytic production of an aqueous hydrogen peroxide solution. Background Art

[0002] Hydrogen peroxide (H2O2) is an environmentally friendly oxidant, disinfectant and bleaching agent, and is widely used in the fields of chemical industry, agriculture, medicine, industry and energy globally. The traditional industrial method for producing H2O2 is the anthraquinone method, which uses a noble metal palladium catalyst and is carried out under high temperature and high energy consumption conditions, and at the same time, harmful organic compounds will be produced. In addition, the storage and transportation of high-concentration aqueous H2O2 may bring safety problems. Therefore, the development of environmentally friendly and low-energy-consuming H2O2 production methods (such as electrocatalytic technology) has become a research hotspot. Through the electrocatalytic method, H2O2 can be generated through a two-electron oxygen reduction reaction (2e - ORR) pathway. A typical 2e - ORR process can usually be easily operated at a low external voltage and does not produce other by-products, so it has great application potential in industrial H2O2 production. However, oxygen (O2) may be reduced through a four-electron pathway (4e - ORR) on the cathode surface, thereby reducing the yield of H2O2. Therefore, the development of a catalyst with high catalytic activity and selectivity for 2e - ORR remains a challenge.

[0003] In recent years, transition metal phosphide (TMP) catalysts have attracted extensive attention in the field of ORR due to their high conductivity, stability and quasi-metallic properties. The valence state of the slightly positively charged transition metal element is close to zero valence, and it can have both metallic and non-metallic properties at the same time; the electronegative phosphorus also plays the role of an electron donor in the ORR process. It is reported that nickel phosphide shows strong electrocatalytic activity in the production of H2O2, and its Faraday efficiency (FE) exceeds 95%. In addition, the electronic configuration of TMP can be adjusted by methods such as doping heterogeneous structures, adjusting morphologies, and generating vacancy defects. Among them, the construction of heterogeneous structures is a common way to construct 2e - ORR catalysts. It can change the electronic structure of the main active sites by doping another metal and regulate the charge density between the active sites. The re-distributed atomic coordination and covalent bonds can provide a suitable binding strength for the reaction intermediate *OOH. When the binding energy of *OOH is too weak, the formation of *OOH from O2 will be restricted; while when the binding energy of *OOH is too strong, the desorption of *OOH on the catalyst surface will be blocked, thereby turning 2e - ORR into 4e -Water (H2O) is generated by ORR. It has been found in the prior art that the heterostructure of cobalt phosphide selenide (CoPSe) has an ORR selectivity of 76-85% in an acidic medium (pH value of 1-3), which is 27-113% higher than that of single cobalt phosphide (CoP). However, the commonly used fields of hydrogen peroxide aqueous solution are medical and chemical disinfectants at present, and a neutral hydrogen peroxide aqueous solution is required; while the hydrogen peroxide aqueous solution electrocatalytically generated with cobalt phosphide selenide as the catalyst is acidic, and its application range is small. - The present invention provides an iron-nickel-phosphorus catalyst, a preparation method and an application thereof, and a method for electrocatalytic production of hydrogen peroxide. The iron-nickel-phosphorus catalyst prepared by the preparation method provided by the present invention can efficiently electrocatalytically produce hydrogen peroxide in an electrolyte with a pH value of 5-9, and the obtained hydrogen peroxide aqueous solution has a wide pH value range, that is, the pH value is 5-9, so that the application range of the hydrogen peroxide aqueous solution is wider. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an iron-nickel-phosphorus catalyst, a preparation method and an application thereof, and a method for electrocatalytic production of hydrogen peroxide. The iron-nickel-phosphorus catalyst prepared by the preparation method provided by the present invention can efficiently electrocatalytically produce hydrogen peroxide in an electrolyte with a pH value of 5-9, and the obtained hydrogen peroxide aqueous solution has a wide pH value range, that is, the pH value is 5-9, so that the application range of the hydrogen peroxide aqueous solution is wider.

[0005] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of an iron-nickel-phosphorus catalyst, comprising the following steps:

[0007] Mix a nickel salt, an iron salt, elemental phosphorus and a reducing solvent, and carry out a solvothermal reaction to obtain the iron-nickel-phosphorus catalyst;

[0008] The nickel salt is nickel chloride;

[0009] The iron salt is iron chloride;

[0010] The reducing solvent is alkanolamine.

[0011] Preferably, the mass ratio of the nickel salt to the iron salt is 5-9.8:5-0.2.

[0012] Preferably, the nickel salt is a nickel salt hydrate; the iron salt is an iron salt hydrate.

[0013] Preferably, the molar ratio of the elemental phosphorus to the nickel salt is 1.5-2.5:1.

[0014] Preferably, the elemental phosphorus is red phosphorus.

[0015] Preferably, the alkanolamine is ethanolamine.

[0016] Preferably, the temperature of the solvothermal reaction is 160-220 °C, and the heat preservation time is 8-12 h.

[0017] The present invention also provides an iron-nickel-phosphorus catalyst prepared by the preparation method described in the above technical solution. The iron-nickel-phosphorus catalyst includes iron phosphide, nickel phosphide, and iron-doped nickel phosphide.

[0018] The present invention also provides the application of the iron-nickel-phosphorus catalyst described in the above technical solution in the electrocatalytic production of hydrogen peroxide.

[0019] The present invention also provides a method for electrocatalytically producing hydrogen peroxide, which includes the following steps:

[0020] Using a graphite electrode loaded with a catalyst as the cathode, a graphite electrode as the anode, and an Ag / AgCl reference electrode as the reference electrode, an electrocatalytic reaction is carried out in an electrolyte solution to obtain the hydrogen peroxide, and the hydrogen peroxide exists in the form of an aqueous hydrogen peroxide solution;

[0021] The catalyst is the iron-nickel-phosphorus catalyst described in the above technical solution;

[0022] The electrolyte of the electrolyte solution includes sodium sulfate;

[0023] The pH value of the electrolyte solution is 5-9.

[0024] The present invention provides a preparation method for an iron-nickel-phosphorus catalyst.

[0025] The present invention uses a nickel salt, an iron salt, elemental phosphorus, and a reducing solvent as raw materials to carry out a solvothermal reaction to obtain an iron-nickel-phosphorus catalyst. The iron-nickel-phosphorus catalyst includes iron phosphide, nickel phosphide, and iron-doped nickel phosphide. The obtained iron-nickel-phosphorus catalyst can efficiently electrocatalytically produce hydrogen peroxide in an electrolyte solution with a pH value of 5-9. The obtained hydrogen peroxide exists in the form of an aqueous hydrogen peroxide solution, so that the pH value range of the aqueous hydrogen peroxide solution is wide, that is, 5-9, and the application range and field are wider. Compared with cobalt phosphide doped with selenium in the prior art, the aqueous hydrogen peroxide solution obtained in the present invention has a wider application. Description of the Drawings

[0026] Figure 1 It is a surface morphology characterization diagram of the catalyst;

[0027] Figure 2 It is the XRD spectrum and XPS spectrum of the catalyst;

[0028] Figure 3 It is the LSV curve of the catalyst;

[0029] Figure 4 It is the Tafel slope of the catalyst;

[0030] Figure 5 It is the EIS curve of the catalyst;

[0031] Figure 6Concentration diagram of hydrogen peroxide aqueous solution produced by electrocatalysis of Fe-Ni-P-180 at different applied voltages;

[0032] Figure 7 Concentration diagram of hydrogen peroxide aqueous solution produced by electrocatalysis of Fe-Ni-P-180 in electrolytes with different pH values;

[0033] Figure 8 Hydrogen peroxide aqueous solution concentration and FEs of the catalyst;

[0034] Figure 9 Specific energy consumption of the catalyst;

[0035] Figure 10 Stability test diagram of Fe-Ni-P-180;

[0036] Figure 11 Comparison diagram of electrocatalytic activity and energy consumption of different catalysts;

[0037] Figure 12 Diagram of the change of hydrogen peroxide aqueous solution concentration produced by electrocatalysis of catalysts with different phosphorus contents over time;

[0038] Figure 13 Diagram of the change of hydrogen peroxide aqueous solution concentration produced by electrocatalysis of catalysts with different iron-nickel contents over time. Specific implementation mode

[0039] The present invention provides a preparation method of an iron-nickel-phosphorus catalyst, comprising the following steps:

[0040] Mix nickel salt, iron salt, phosphorus element and a reducing solvent, and carry out a solvothermal reaction to obtain the iron-nickel-phosphorus catalyst;

[0041] The nickel salt is nickel chloride (NiCl2);

[0042] The iron salt is iron chloride (FeCl3);

[0043] The reducing solvent is alkanolamine.

[0044] Unless otherwise specified, the raw materials used in the present invention are preferably commercially available products.

[0045] In the present invention, the nickel salt is preferably a nickel salt hydrate, specifically preferably nickel chloride hexahydrate (NiCl2·6H2O). In the present invention, the iron salt is preferably an iron salt hydrate, specifically preferably iron chloride hexahydrate (FeCl3·6H2O).

[0046] In the present invention, the mass ratio of the nickel salt to the iron salt is preferably 5-9.8:5-0.2, more preferably 8.5-9.6:1.5-0.4, still more preferably 9-9.5:1-0.5, and specifically can be 5:5, 6:4, 7:3, 8:2, 8.5:1.5, 9:1, 9.5:0.5 or 9.8:0.2. In the present invention, the mass ratio of the nickel salt to the iron salt affects the contents of nickel and iron in the final iron-nickel-phosphorus catalyst, and thus affects the electrocatalytic activity of the iron-nickel-phosphorus catalyst for producing hydrogen peroxide.

[0047] In the present invention, the elemental phosphorus is preferably red phosphorus.

[0048] In the present invention, the molar ratio of the elemental phosphorus to the nickel salt is preferably 1.5-2.5:1, more preferably 2.1:1, and specifically can be 1.5:1, 1.8:1, 2:1, 2.1:1, 2.3:1 or 2.5:1. In the present invention, the molar ratio of the elemental phosphorus to the nickel salt affects the phosphorus content in the iron-nickel-phosphorus catalyst, and thus affects the catalytic activity of the iron-nickel-phosphorus catalyst.

[0049] In the present invention, the alkanolamine is preferably ethanolamine.

[0050] In the present invention, the mixing is preferably carried out under ultrasonic conditions, and the ultrasonic time is preferably 2-4 h, more preferably 3 h.

[0051] In the present invention, the temperature of the solvothermal reaction is preferably 160-220 °C, more preferably 180-200 °C, and specifically preferably 160 °C, 180 °C, 200 °C or 220 °C; the heat preservation time is preferably 8-12 h, more preferably 10 h. In the present invention, the atmosphere of the solvothermal reaction is preferably nitrogen. In the present invention, the solvothermal reaction is preferably carried out in a reaction kettle. In the present invention, during the solvothermal reaction, the reaction kettle is preferably in a closed state. In a specific embodiment of the present invention, the specific process of the solvothermal reaction preferably includes: placing the nickel salt, iron salt, elemental phosphorus and reducing solvent in the quartz inner lining of the reaction kettle, closing the reaction kettle, introducing nitrogen for 30 min, and then heating up for the solvothermal reaction.

[0052] After the solvothermal reaction, the present invention preferably further includes: after cooling the obtained feed liquid to room temperature, centrifuging, and washing and drying the obtained precipitate in sequence to obtain the iron-nickel-phosphorus catalyst. In the present invention, the rotation speed of the centrifugation is preferably 6000-10000 rpm, more preferably 8000 rpm; the time is preferably 5-15 min, more preferably 10 min. In the present invention, the washing preferably includes ethanol washing and water washing in sequence, the number of times of ethanol washing is preferably 1-2 times, the number of times of water washing is preferably 1-2 times, and the reagent for water washing is preferably deionized water. In the present invention, the drying temperature is preferably 60-100 °C, more preferably 80 °C; the time is preferably 4-6 h, more preferably 5 h; the drying is preferably carried out in an oven.

[0053] In the present invention, during the solvothermal reaction, elemental phosphorus, nickel salt, and iron salt undergo a redox reaction under the conditions of a reducing solvent, heating, and sealing to obtain an iron-nickel-phosphorus catalyst containing iron phosphide, nickel phosphide, and iron-doped nickel phosphide; the temperature of the solvothermal reaction can affect the crystallinity of the catalyst and the content of metal phosphides in the catalyst, thereby affecting the catalytic activity of the iron-nickel-phosphorus catalyst.

[0054] The present invention also provides an iron-nickel-phosphorus catalyst prepared by the preparation method described in the above technical solution, and the iron-nickel-phosphorus catalyst includes iron phosphide, nickel phosphide, and iron-doped nickel phosphide.

[0055] The present invention also provides an application of the iron-nickel-phosphorus catalyst described in the above technical solution in electrocatalytic production of hydrogen peroxide.

[0056] The present invention also provides a method for electrocatalytic production of hydrogen peroxide, including the following steps:

[0057] Using a graphite electrode loaded with the catalyst as the cathode, a graphite electrode as the anode, and an Ag / AgCl reference electrode as the reference electrode, an electrocatalytic reaction is carried out in the electrolyte to obtain the hydrogen peroxide, and the hydrogen peroxide exists in the form of an aqueous hydrogen peroxide solution;

[0058] The catalyst is the iron-nickel-phosphorus catalyst described in the above technical solution;

[0059] The electrolyte of the electrolyte includes sodium sulfate;

[0060] The pH value of the electrolyte is 5-9.

[0061] In the present invention, the method for preparing the graphite electrode loaded with the catalyst preferably comprises the following steps: mixing the catalyst, Nafion solution and aqueous ethanol solution, uniformly coating the obtained mixture liquid onto the graphite electrode, and naturally drying to obtain the graphite electrode loaded with the catalyst. In the present invention, the concentration of the Nafion solution is preferably 5 wt%, the concentration of the aqueous ethanol solution is preferably 60 wt%, and the dosage ratio of the catalyst, Nafion solution and aqueous ethanol solution is preferably 5-10 mg: 20 μL: 0.5 mL, specifically it can be 8 mg: 20 μL: 0.5 mL.

[0062] In the present invention, the concentration of the electrolyte in the electrolyte solution is preferably 0.5 mol / L.

[0063] In the present invention, the pH value of the electrolyte solution is 5-9, specifically 5, 7 or 9.

[0064] In the present invention, the voltage of the electrocatalysis is preferably -0.3 to -0.6 V vs. Ag / AgCl, specifically preferably -0.3 V vs. Ag / AgCl, -0.4 V vs. Ag / AgCl, -0.5 V vs. Ag / AgCl or -0.6 V vs. Ag / AgCl.

[0065] The iron-nickel-phosphorus catalyst provided by the present invention, its preparation method and application, and the method for electrocatalytic production of hydrogen peroxide will be described in detail below with reference to the examples, but they cannot be understood as limiting the protection scope of the present invention.

[0066] Examples and Comparative Examples

[0067] The catalyst was prepared by a solvothermal method:

[0068] Red phosphorus (40 mM), nickel chloride hexahydrate (NiCl2·6H2O, 20 mM) and 300 mL of ethanolamine (C2H7NO) were ultrasonically mixed for 3 h, then the suspension was placed in a 500 mL quartz inner liner of a hydrothermal tank, the reaction kettle was closed, nitrogen was filled into the reaction kettle for 30 min, heated to 180 °C and maintained for 10 h, cooled to room temperature, the mixture was centrifuged at 8000 rpm for 10 min, the precipitate was washed twice with ethanol and deionized water by centrifugation, and the obtained solid was dried in an oven at 80 °C for 5 h to obtain the Ni-P catalyst.

[0069] The Fe-Ni-P catalyst was prepared in the same way, while replacing part of NiCl2·6H2O with ferric chloride hexahydrate (FeCl3·6H2O), and the mass ratio of nickel salt to iron salt was 9.5:0.5. The effects of different solvothermal temperatures (160 °C, 180 °C, 200 °C, 220 °C) were studied, and the obtained iron-nickel-phosphorus catalysts were denoted as Fe-Ni-P-160, Fe-Ni-P-180, Fe-Ni-P-200, and Fe-Ni-P-220, respectively.

[0070] Performance test

[0071] The surface morphology of the catalyst was characterized, and the results are as Figure 1 shown. Figure 1 It is the surface morphology characterization diagram of the catalyst. Figure 1 Among them, a is the scanning electron microscope image of Ni-P, b is the scanning electron microscope image of Fe-Ni-P-160, c is the scanning electron microscope image of Fe-Ni-P-180, d is the scanning electron microscope image of Fe-Ni-P-200, e is the scanning electron microscope image of Fe-Ni-P-220, f is the high-resolution transmission electron microscope (TEM) image of Ni-P, g is the selected area electron diffraction (TEM-SEAD) image corresponding to Ni-P, h is the high-resolution transmission electron microscope image of Fe-Ni-P-180, and i is the selected area electron diffraction (TEM-SEAD) image corresponding to Fe-Ni-P-180. It can be seen from Figure 1 that: Fe-Ni-P-160 is a granular structure, and Ni-P and Fe-Ni-P-180 are flaky structures. With the continuous increase of the solvothermal temperature, more small particles appear in Fe-Ni-P-200 and Fe-Ni-P-220, indicating that the higher the synthesis temperature, the better the crystallinity of the catalyst. The high-resolution transmission electron microscope photos Figure 1 (f and h in Figure 1 ) show clear lattice spacings. According to the TEM-SEAD image Figure 1 (g in

[0072] ), the lattice spacings of the Ni-P catalyst are 0.160, 0.203, and 0.221 nm, corresponding to the (102), (201), and (111) crystal planes of the Ni2P crystal, respectively. For Fe-Ni-P-180

[0073] Table 1 Element content of the catalyst

[0074] Ni / at% Fe / at% P / at% O / at% Ni-P 27.88 - 35.7 36.43 Fe-Ni-P-160 35.60 1.19 46.57 16.65 Fe-Ni-P-180 53.74 1.87 20.60 23.80 Fe-Ni-P-200 58.43 0.93 18.92 21.71 Fe-Ni-P-220 60.05 0.28 21.81 17.87

[0075] As can be seen from Table 1, Ni-P contains Ni and P, and Fe is successfully doped into the Fe-Ni-P catalyst. In addition, due to exposure to air during operations such as oven drying, the catalysts all contain O element. The content of Ni in Ni-P is 27.88 at%, and after adding Fe element, the Ni content in Fe-Ni-P all increases, indicating that the doping of Fe can improve the crystallization of Ni element. With the increase of the solvothermal reaction temperature, the Ni content in Fe-Ni-P gradually increases, proving that the higher the solvothermal reaction temperature, the better the crystallinity of the catalyst, which is consistent with the SEM results mentioned above. Among all the catalysts, Fe-Ni-P-180 has the highest Fe ratio, which is 1.87 at%.

[0076] The analysis of the catalyst structure is as follows Figure 2 shown. Figure 2 are the XRD patterns and XPS spectra of the catalysts. Figure 2 Among them, a is the XRD pattern of each catalyst, b is the high-resolution XPS spectrum of the Ni 2p 3 / 2 spectrum of the catalyst, c is the high-resolution XPS spectrum of the Fe2p spectrum of the catalyst, and d is the high-resolution XPS spectrum of the P 2p spectrum of the catalyst. As can be seen from a in Figure 2 , compared with the standard PDF card, Ni-P is composed of Ni2P (PDF#74-1385), Ni3P (PDF#74-1384), Ni 12 P5 (PDF#74-1381) and metallic Ni (PDF#87-0712). The FeNi2P peak (PDF#51-1367) appears in the Fe-Ni-P catalyst. This is consistent with the TEM-SEAD results mentioned above. With the increase of the solvothermal temperature, the metallic Ni spectral peak decreases significantly, and the spectral peaks of Ni2P, Ni 12 P5 and FeNi2P increase significantly (except for the peak of Fe-Ni-P-200). The results show that Fe can promote the transformation of metallic Ni to Ni-P, and the increase of the solvothermal temperature is beneficial to the crystallization of metal phosphides. The elemental state of the catalyst was studied by XPS. Figure 2 The high-resolution XPS Ni 2p 3 / 2 in b of δ+ can be deconvoluted into 3 peaks. Among them, the peak at ~852.95 eV is Ni 3 / 2 2p in the Ni-P bond. The Ni δ+ in the Ni-P catalyst is 15.66%, while in the Fe-Ni-P catalyst it is 19-21%, indicating that the doping of Fe can promote the formation of metal phosphides, especially Ni-P. Figure 2In the high-resolution XPS Fe 2p deconvolution spectrum of c, ~706.50 and ~717.30 eV correspond to Fe in iron phosphide respectively δ+ 2p 3 / 2 and Fe δ+ 2p 1 / 2 . Figure 2 In d, the valence state analysis of P element is carried out, where 129.55 and ~130.50 eV are P in phosphide δ- . The P δ- peak area percentage and peak intensity of Fe-Ni-P-180 are the highest among all catalysts, further indicating that a small amount of Fe is more conducive to the synthesis of metal phosphide at 180 °C

[0077] 8 mg of catalyst, 20 μL of 5 wt% Nafion solution and 0.5 mL of 60 wt% ethanol aqueous solution are mixed, and the obtained mixed system is drop-coated on a graphite substrate to prepare an electrode for electrochemical performance testing, and graphite is used as a blank control group. The results are as Figures 3 - 5 shown Figure 3 is the LSV curve of the catalyst Figure 4 is the Tafel slope of the catalyst Figure 5 is the EIS curve of the catalyst. It can be seen from Figure 3 that within the scanning range, the LSV current density of the graphite electrode is much lower than that of Ni-P (control group) and Fe-Ni-P electrodes, while the current density of Fe-Ni-P-180 is the highest, indicating that Fe-Ni-P-180 has stronger electrochemical activity and the contribution of the electrode substrate graphite is smaller Figure 4 The Tafel slope of Fe-Ni-P-180 in d is the lowest, 9.95 mV / dec, which is 34.8 - 56.9% lower than that of Ni-P and graphite, indicating that the electron transfer in Fe-Ni-P-180 is faster Figure 5The Nyquist plot of the EIS curve is fitted by an equivalent circuit consisting of an ohmic resistance (R1) and an additional R-CPE (resistive constant phase element) loop. The R1 of graphite, Fe-Ni-P-180, Fe-Ni-P-200, and Fe-Ni-P-220 is close (11 - 18 Ω), while the R1 of Ni-P and Fe-Ni-P-160 is higher (46.33 Ω and 103.10 Ω respectively). The charge transfer resistance R2 of graphite is the highest, at 25581 Ω, while the R2 of other catalysts is less than 8000 Ω. After Fe doping, both R1 and R2 of the Fe-Ni-P catalyst are reduced by 28 - 75% compared to Ni-P (except for the R1 of Fe-Ni-P-160), indicating that Fe doping can significantly improve the conductivity and catalytic activity. Among them, the R2 of Fe-Ni-P-180 is the lowest, indicating that Fe-Ni-P-180 has the best electron transfer ability. The electrochemically active area of the electrode at different scan rates was measured by CV test, and the C of graphite and Ni-P catalysts was calculated to be 1.18 and 0.479 mF / cm² respectively. The C of the Fe-Ni-P catalyst is 0.260 - 0.355 mF / cm². The lower C indicates that the electrical contact between the Fe-Ni-P surface and the electrolyte is limited, which may be due to the higher adsorption of O2 bubbles on the Fe-Ni-P surface. Therefore, the limitation of obtaining O2 for the production of H2O2 on the Fe-Ni-P surface is smaller. dl were 1.18 and 0.479 mF / cm² respectively 2 , and the C of the Fe-Ni-P catalyst dl was 0.260 - 0.355 mF / cm² 2 . The lower C dl indicates that the electrical contact between the Fe-Ni-P surface and the electrolyte is limited, which may be due to the higher adsorption of O2 bubbles on the Fe-Ni-P surface. Therefore, the limitation of obtaining O2 for the production of H2O2 on the Fe-Ni-P surface is smaller.

[0078] The test was carried out using a three-electrode system. The graphite electrode was used as the counter electrode, the graphite electrode modified with the catalyst was used as the working electrode, Ag / AgCl was used as the reference electrode, and 0.5 mol / L Na2SO4 solution was used as the electrolyte. Under the conditions of 0.6 mL-O2 / min, electrolyte pH = 7, and voltages of -0.3, -0.4, -0.5, or -0.6 V vs. Ag / AgCl, an electrocatalytic experiment was carried out using the Fe-Ni-P-180 modified electrode, and the results are as Figure 6 shown. Figure 6 is the concentration diagram of electrocatalytic hydrogen peroxide aqueous solution of Fe-Ni-P-180 at different applied voltages. It can be seen from Figure 6 that: the activity of Fe-Ni-P-180 is lower at -0.3 V vs. Ag / AgCl, and the production of hydrogen peroxide is the highest at -0.4 V vs. Ag / AgCl, at 0.60 ± 0.03 mM, and the optimal voltage for 2e ORR is -0.4 V vs. Ag / AgCl. - The optimal voltage for 2e ORR is -0.4 V vs. Ag / AgCl.

[0079] The test was carried out using a three - electrode system. The graphite electrode was used as the counter electrode, the graphite electrode modified with the catalyst was used as the working electrode, Ag / AgCl was used as the reference electrode, and 0.5 mol / L Na2SO4 solution was used as the electrolyte. Under the conditions of - 0.4 V vs. Ag / AgCl, 0.6 mL - O2 / min, and the electrolyte pH = 3, 5, 7 or 9, the electrocatalytic experiment was carried out using the Fe - Ni - P - 180 modified electrode, and the results are as Figure 7 shown. Figure 7 It is the concentration diagram of hydrogen peroxide aqueous solution electrocatalytically produced by Fe - Ni - P - 180 in electrolytes with different pH values. From Figure 7 it can be seen that: Fe - Ni - P - 180 has a relatively high catalytic efficiency in a wide pH range of 5 - 9, and the optimal initial pH for the 2e - ORR is 7.

[0080] The test was carried out using a three - electrode system. The graphite electrode was used as the counter electrode, the graphite electrode modified with the catalyst was used as the working electrode, Ag / AgCl was used as the reference electrode, and 0.5 mol / L Na2SO4 solution was used as the electrolyte. Under the conditions of - 0.4 V vs. Ag / AgCl, 0.6 mL - O2 / min, and the electrolyte pH = 7, the electrocatalytic experiment was carried out using different catalyst - modified electrodes, and the results are as Figures 8 - 9 shown. Figure 8 They are the hydrogen peroxide aqueous solution concentration and FEs of the catalysts, Figure 9 and the specific energy consumption of the catalysts. From Figure 8 it can be seen that within 30 min, graphite can only produce 0.18 ± 0.10 mM of H2O2, while the H2O2 produced by the Ni - P catalyst is more than twice that of graphite. After Fe doping, the H2O2 concentration produced by Fe - Ni - P - 160 is 0.54 ± 0.07 mM, and the H2O2 concentration produced by Fe - Ni - P - 180 is 0.60 ± 0.03 mM, which are 42.1% and 57.9% higher than that of Ni - P respectively. It shows that Fe and P δ- play an important role in the 2e - ORR and can promote the generation of H2O2 when the solvothermal temperature is lower than 180℃. Due to the high electrocatalytic activity and low electron transfer resistance of Fe - Ni - P - 180, the FE of Fe - Ni - P - 180 is also the highest (94.38 ± 4.68%). As the solvothermal temperature increases, the concentration of hydrogen peroxide aqueous solution gradually decreases. As Figure 9 shown, at the - 0.4 V vs. Ag / AgCl potential, the specific energy consumption of the electrode modified with the Fe - Ni - P - 180 catalyst to produce hydrogen peroxide aqueous solution is lower, which is 0.42 ± 0.02 kWh / kg - H2O2, meaning it can produce more H2O2 with less energy consumption.

[0081] The test was carried out using a three - electrode system. A graphite electrode was used as the counter electrode, a graphite electrode modified with the catalyst was used as the working electrode, Ag / AgCl was used as the reference electrode, and a 0.5 mol / L Na2SO4 solution was used as the electrolyte. Under the conditions of - 0.4 V vs. Ag / AgCl, 0.6 mL - O2 / min, and pH = 7, an electrocatalytic experiment of 10 consecutive cycles was carried out using the Fe - Ni - P - 180 modified electrode, and the results are as Figure 10 shown. Figure 10 This is the stability test diagram of Fe - Ni - P - 180. From Figure 10 it can be seen that: the production rate constant of H2O2 was 10.45 μM / (min·cm 2 ) in the first cycle and remained at about 7 μM / (min·cm 2 ) in the remaining 9 cycles. It shows that Fe - Ni - P - 180 has strong reusability in catalyzing the 2e - ORR and is a very promising material for industrial electrocatalytic production of H2O2.

[0082] The electrocatalytic activity and energy consumption of Fe - Ni - P - 180 for electrocatalytic production of H2O2 were compared with those of some recently reported catalysts, and the results are as Figure 11 shown. Figure 11 This is the comparison diagram of the electrocatalytic activity and energy consumption of different catalysts. From Figure 11 it can be seen that: the Fe - Ni - P - 180 electrode performs excellently, with higher H2O2 production and FE and relatively lower specific energy consumption.

[0083] Research Example 1

[0084] Red phosphorus (40 mM), nickel chloride hexahydrate (NiCl2·6H2O, 19 mM), ferric chloride hexahydrate (FeCl3·6H2O, the mass ratio of NiCl2·6H2O and FeCl3·6H2O is 9.5:0.5), and ethanolamine (C2H7NO, 300 mL) were ultrasonically mixed for 3 h. Then the suspension was placed in a 500 - mL quartz inner liner of a hydrothermal tank, and nitrogen was introduced for 30 min to remove oxygen. Then the temperature was raised to 180 °C and maintained for 10 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm for 10 min. The precipitate was washed twice with ethanol and deionized water by centrifugation, and the obtained solid was dried in an oven at 80 °C for 5 h to obtain the Fe - Ni - P - 180 catalyst, denoted as P×1.

[0085] The effects of different amounts of red phosphorus added were studied. Specifically, the concentrations of red phosphorus were adjusted to 80 mM, 120 mM, 20 mM, and 10 mM, and the obtained iron-nickel-phosphorus catalysts were denoted as P×2 (corresponding to a red phosphorus concentration of 80 mM), P×3 (corresponding to a red phosphorus concentration of 120 mM), P×0.5 (corresponding to a red phosphorus concentration of 20 mM), and P×0.25 (corresponding to a red phosphorus concentration of 10 mM), respectively.

[0086] The tests were carried out using a three-electrode system. A graphite electrode was used as the counter electrode, a graphite electrode modified with the catalyst was used as the working electrode, Ag / AgCl was used as the reference electrode, and a 0.5 mol / L Na2SO4 solution was used as the electrolyte. Under the conditions of -0.4 V vs. Ag / AgCl, 0.6 mL-O2 / min, and pH = 7, electrocatalytic experiments were carried out using electrodes modified with catalysts with different phosphorus contents. The results are as Figure 12 shown. Figure 12 It is a graph showing the change of the concentration of the electrocatalytically produced hydrogen peroxide aqueous solution with time for catalysts with different phosphorus contents. From Figure 12 it can be seen that: Except that the reaction rate of the 3-fold phosphorus content is relatively poor, P×1 is relatively stable, while for the others, although the initial reaction rate is slightly higher, the stability is not good, and the catalyst starts to deactivate after 20 min, and the reaction rate decreases.

[0087] Research Example 2

[0088] The effects of different amounts of ferric chloride hexahydrate added were studied. Specifically, red phosphorus (40 mM), nickel chloride hexahydrate (NiCl2·6H2O, 19 mM), ferric chloride hexahydrate (the mass ratio of FeCl3·6H2O, NiCl2·6H2O and FeCl3·6H2O is 9.5:0.5), and ethanolamine (C2H7NO, 300 mL) were ultrasonically mixed for 3 h, then the suspension was placed in a 500 mL quartz inner lining of a hydrothermal tank, nitrogen was introduced for 30 min to remove oxygen, then the temperature was raised to 180 °C and maintained for 10 h, cooled to room temperature, the mixture was centrifuged at 8000 rpm for 10 min, the precipitate was washed twice with ethanol and deionized water by centrifugation, and the obtained solid was dried in an oven at 80 °C for 5 h to obtain the Fe-Ni-P-180 catalyst, denoted as Fe:Ni = 0.5:9.5.

[0089] The effects of different amounts of hydrated ferric chloride added were studied. Specifically, the concentration of nickel chloride hexahydrate was changed to 18 mM (corresponding to a mass ratio of ferric chloride hexahydrate and nickel chloride hexahydrate of 1:9, and the obtained catalyst was named Fe:Ni = 1:9), 10 mM (corresponding to a mass ratio of ferric chloride hexahydrate and nickel chloride hexahydrate of 1:1, and the obtained catalyst was named Fe:Ni = 1:1), 20 mM (no ferric chloride hexahydrate was added, and the obtained catalyst was named Fe:Ni = 0:1).

[0090] The test was carried out using a three - electrode system. A graphite electrode was used as the counter electrode, a graphite electrode modified with the catalyst was used as the working electrode, Ag / AgCl was used as the reference electrode, and a 0.5 mol / L Na2SO4 solution was used as the electrolyte. Under the conditions of - 0.4 V vs. Ag / AgCl, 0.6 mL - O2 / min, and pH = 7, electrocatalytic experiments were carried out using electrodes modified with catalysts with different iron - nickel contents. The results are as Figure 13 shown. Figure 13 It is a graph showing the change of the concentration of the electrocatalytically produced hydrogen peroxide aqueous solution with time for catalysts with different iron - nickel contents. From Figure 13 it can be seen that the proportion of iron - nickel content in the catalyst will affect the electrocatalytic activity of the catalyst, thus affecting the yield of hydrogen peroxide. The yield of hydrogen peroxide of the iron - nickel - phosphorus catalyst provided by the present invention is higher than that of the nickel - phosphorus catalyst.

[0091] The above - mentioned is only the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of an iron-nickel-phosphorus catalyst, comprising the following steps: Mixing a nickel salt, an iron salt, elemental phosphorus, and a reducing solvent, and performing a solvothermal reaction to obtain the iron-nickel-phosphorus catalyst; The nickel salt is nickel chloride; The iron salt is iron chloride; The reducing solvent is alkanolamine.

2. The preparation method according to claim 1, wherein The mass ratio of the nickel salt to the iron salt is 5-9.8:5-0.

2.

3. The preparation method according to claim 1 or 2, characterized in that The nickel salt is a nickel salt hydrate; the iron salt is an iron salt hydrate.

4. The preparation method according to claim 1, characterized in that, The molar ratio of the elemental phosphorus to the nickel salt is 1.5-2.5:

1.

5. The preparation method according to claim 1 or 4, characterized in that, The elemental phosphorus is red phosphorus.

6. The preparation method according to claim 1, characterized in that, The alkanolamine is ethanolamine.

7. The preparation method according to claim 1, wherein, The temperature of the solvothermal reaction is 160-220 °C, and the heat preservation time is 8-12 h.

8. The iron-nickel-phosphorus catalyst prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The iron-nickel-phosphorus catalyst comprises iron phosphide, nickel phosphide, and iron-doped nickel phosphide.

9. Use of the iron-nickel-phosphorus catalyst according to claim 8 in electrocatalytic production of hydrogen peroxide.

10. A method for electrocatalytic production of hydrogen peroxide, characterized in that, Comprising the following steps: Using a graphite electrode loaded with the catalyst as the cathode, a graphite electrode as the anode, and an Ag / AgCl reference electrode as the reference electrode, and performing an electrocatalytic reaction in an electrolyte solution to obtain the hydrogen peroxide, and the hydrogen peroxide exists in the form of an aqueous hydrogen peroxide solution; The catalyst is the iron-nickel-phosphorus catalyst according to claim 8; The electrolyte of the electrolyte solution comprises sodium sulfate; The pH value of the electrolyte solution is 5-9.

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