Method for preparing hydrogen peroxide through electrocatalytic oxygen reduction

Abstract

The invention discloses a method for preparing hydrogen peroxide through electro-catalytic oxygen reduction, which comprises the following steps: dispersing a few-layer graphene coated Ni catalyst in a solvent, dripping on the surface of a rotating ring disc glassy carbon electrode, and drying to obtain a working electrode for preparing hydrogen peroxide through electro-catalytic oxygen reduction reaction. The few-layer graphene coated Ni catalyst is used for producing hydrogen peroxide through electro-catalytic oxygen reduction, the preparation method of the catalyst is simple and easy to implement, raw materials are cheap and easy to obtain, and the obtained few-layer graphene coated Ni catalyst has excellent selectivity and stability in the process of preparing hydrogen peroxide through electro-catalytic oxygen reduction in an acid environment; the method has important significance on industrialization of electrochemical preparation of hydrogen peroxide in an acid environment.

Description

Technical Field

[0001] The invention relates to the field of electrocatalytic materials, and in particular to a method for preparing hydrogen peroxide by electrocatalytic oxygen reduction using a few-layer graphene-wrapped Ni catalyst. Background Art

[0002] Hydrogen peroxide (H 2 O 2 ) is recognized as one of the 100 most important chemicals in the world. Due to its oxidizing and reducing properties, it is widely used in chemical synthesis, pharmaceutical preparation, industrial bleaching, military industry, food and environment and other fields. It does not cause secondary pollution after use and is defined as a green chemical product. Currently, more than 95% of hydrogen peroxide is produced in concentrated form using the anthraquinone method (see: Catal. Sci. Technol. 2016, 6 (6), 1593-1610). The industrial synthesis steps include hydrogenation, O 2 The multi-step synthesis process, such as oxidation of anthraquinone and extraction purification, drives up energy consumption and production costs. And the production process involves the use of toxic additives such as acid additives and halogen ions. In addition, the hydrogen peroxide consumed in large quantities in industrial applications at this stage is a 30% mass fraction aqueous solution. The process of concentrating and purifying hydrogen peroxide also produces a large amount of waste, and the product distribution process also has storage and transportation safety issues. Therefore, it is urgent to reduce the transportation cost of hydrogen peroxide and develop an economical, green, efficient and sustainable method to produce hydrogen peroxide.

[0003] In recent years, with the widespread application of renewable energy power generation, electrochemical synthesis of hydrogen peroxide (by inputting renewable electricity to electrocatalyze 2e - -ORR synthesis of hydrogen peroxide) has received widespread attention. This electrochemical method uses oxygen or water as raw materials and only produces water as a by-product. It is environmentally friendly and has high atomic efficiency, providing a green, economical and sustainable development approach for the in situ production of hydrogen peroxide. At present, a large number of studies are still focused on the preparation of hydrogen peroxide by electrocatalytic oxygen reduction in alkaline environments (see: CN 115505957 A, CN 117144395 A). However, in practical applications, the scheme for producing hydrogen peroxide in an acidic environment is more valuable. First, the acid dissociation constant of hydrogen peroxide (pKa=11.7) causes its main form in acidic media to be H 2 O 2 Not HO 2 - . H in acidic environment 2 O 2It has a stronger oxidizing ability, which enables it to be effectively used in various industrial processes. Secondly, hydrogen peroxide is more stable in an acidic environment because higher pH values ​​promote its decomposition (see: J. Energy Chem. 2022, 67, 432-450). In addition, wastewater purification and environmental remediation can also benefit from direct electrosynthesis of hydrogen peroxide under acidic conditions. The electro-Fenton process operates optimally at a pH of about 3, which can convert the produced hydrogen peroxide into more oxidative hydroxyl radicals (•OH) for the removal of persistent bacteria and organic pollutants (see: ACS Energy Lett. 2023, 8 (1), 196-212).

[0004] However, for the electrochemical oxygen reduction to prepare hydrogen peroxide in an acidic environment, most of the catalysts reported so far are precious metal-based catalysts, such as Pt, Pd, etc. Although these catalysts have high activity and high selectivity, the scarcity and high price of precious metals greatly affect their practical industrial applications. In recent years, carbon materials with the advantages of low cost, good conductivity, and strong modifiability have received widespread attention in the field of electrocatalytic oxygen reduction to prepare hydrogen peroxide. CN 116043266 A discloses a CoPSe / C catalyst synthesized by a method of high temperature annealing, simultaneous selenization and phosphating using MOF as a precursor and template. The catalyst has a high conductivity and a low molecular weight. The catalyst has a high molecular weight. 4 The selectivity of the electrolyte to hydrogen peroxide is about 80% under the condition of the potential range of 0.0-0.5V (vs. RHE). CN 114892197 A discloses a series of carbon material-supported transition metal catalysts, among which the best catalyst (Co supported by carbon black) is in 0.1M HClO 4 The selectivity of hydrogen peroxide is about 90% under the condition of the potential range of 0.0-0.6V (vs. RHE) as the electrolyte, and it can run stably for 15 hours. Combined with the above research reports, the selectivity of electrochemical oxygen reduction to produce hydrogen peroxide in acidic systems still has room for improvement. Therefore, the development of a cheap, efficient and stable catalyst is of great significance to the realization of the industrial process of electrochemical preparation of hydrogen peroxide. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing hydrogen peroxide by electrocatalytic oxygen reduction in view of the defects of the prior art.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a method for preparing hydrogen peroxide by electrocatalytic oxygen reduction, wherein a few-layer graphene-wrapped Ni catalyst is dispersed in a solvent and dropped on the surface of a rotating ring-disk glassy carbon electrode, and after drying, it is used as a working electrode for preparing hydrogen peroxide by electrocatalytic oxygen reduction reaction.

[0007] Furthermore, the few-layer graphene-wrapped Ni catalyst is Ni particles wrapped inside the few-layer graphene, wherein the Ni particle size is 1 to 50 nanometers, the mass content is 5% to 90%, and the number of the few-layer graphene layers is 1 to 3 layers.

[0008] Furthermore, the Ni catalyst wrapped with few-layer graphene is prepared by hydrothermal treatment using metal salt, organic amine and carbon source as raw materials to obtain a precursor, and the precursor is placed in N 2 It is prepared by calcining in an atmosphere and then treating with a sulfuric acid solution.

[0009] Furthermore, the metal salt is one or a mixture of two or more of nickel acetate, nickel nitrate, nickel sulfate, and nickel chloride; the organic amine is one or a mixture of two or more of ethanolamine, urea, dicyandiamide, and hexamethylenetetramine; and the carbon source is one or a mixture of two or more of furfural, furfuryl alcohol, glycerol, glucose, fructose, and lactose.

[0010] Furthermore, the molar ratio of the metal salt, the organic amine, and the carbon source is 1:(0.5-2.0):(2.5-5.5).

[0011] Furthermore, the reaction conditions of the hydrothermal treatment are 100~180℃ for 2.0~24.0h; the calcination conditions are heating to 400~800℃ at 3.0~5.0℃ / min and maintaining for 2.0~8.0h; the concentration of the sulfuric acid solution is 0.1~2.0M, the temperature is 25~80℃, and the treatment time is 2.0~24.0h.

[0012] Furthermore, the solvent is a mixed solution of isopropanol and 5 wt% Nafion, and the concentration of the few-layer graphene-wrapped Ni catalyst in the solvent is 2.5 mg / mL.

[0013] Furthermore, the electrolyte for the electrocatalytic oxygen reduction reaction was 0.1 M HClO 4 For the solution, the test potential on the disk electrode was 0~0.9 V (vs. RHE), and the test potential on the ring electrode was 1.2 V (vs. RHE).

[0014] The present invention adopts a few-layer graphene-wrapped Ni catalyst to produce hydrogen peroxide by electrocatalytic oxygen reduction. The preparation method of the catalyst is simple and easy to implement, the raw materials are cheap and easy to obtain, the catalytic route is environmentally friendly, the conditions are mild, the controllability is strong, renewable energy is used, and the economic benefits are high. The obtained few-layer graphene-wrapped Ni catalyst has low cost and has excellent selectivity and stability in the process of preparing hydrogen peroxide by electrocatalytic oxygen reduction in an acidic environment, which is of great significance to the industrialization of electrochemical preparation of hydrogen peroxide in an acidic environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1The typical XRD spectra of the few-layer graphene-wrapped Ni catalysts obtained in specific embodiments 1 to 4 of the present invention.

[0016] Figure 2 Typical transmission electron microscope photos of the few-layer graphene-wrapped Ni catalysts prepared in specific embodiments 1 to 4 of the present invention.

[0017] Figure 3 Typical high-resolution transmission electron microscopy photographs of the few-layer graphene-wrapped Ni catalysts obtained in specific embodiments 1 to 4 of the present invention.

[0018] Figure 4 The linear scanning curve diagram of the few-layer graphene-wrapped Ni catalyst prepared in specific embodiments 1 to 4 of the present invention for electrocatalytic oxygen reduction reaction.

[0019] Figure 5 The selectivity graph of the few-layer graphene-wrapped Ni catalyst prepared in specific embodiments 1 to 4 of the present invention for the electrocatalytic oxygen reduction reaction to produce hydrogen peroxide is shown.

[0020] Figure 6 The electron transfer graph of the few-layer graphene-wrapped Ni catalyst prepared in specific embodiments 1 to 4 of the present invention for electrocatalytic oxygen reduction reaction.

[0021] Figure 7 This is a current-time curve of a few-layer graphene-wrapped Ni catalyst prepared in specific embodiment 3 of the present invention for constant potential testing. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.

[0023] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatuses.

[0024] Example 1

[0025] This embodiment is a method for preparing a few-layer graphene-wrapped Ni catalyst for producing hydrogen peroxide by electrocatalytic oxygen reduction reaction, which specifically includes the following steps.

[0026] (1) Weigh 1.0 mmol nickel nitrate, 1.5 mmol ethanolamine, 0.5 mmol glycerol and 1.0 mmol glucose in 60 mL deionized water, stir and dissolve, then place the resulting solution in a polytetrafluoroethylene hydrothermal reactor, seal it and place it in a 100°C oven for hydrothermal treatment for 24.0 h. After the hydrothermal reaction is completed, separate the solid product by centrifugation, wash it three times with deionized water and anhydrous ethanol, and finally dry it in an 80°C oven for 12.0 h.

[0027] (2) The dried solid product obtained in (1) was placed in an Ar atmosphere, heated to 450 °C at 5 °C / min, and maintained for 3.0 h.

[0028] (3) Finally, the calcined sample was treated with 0.5 M sulfuric acid at 25 °C for 24.0 h. Finally, it was washed with deionized water and anhydrous ethanol and dried at 80 °C to obtain the Ni@1.5Gr catalyst.

[0029] Example 2

[0030] This embodiment is a method for preparing a few-layer graphene-wrapped Ni catalyst for producing hydrogen peroxide by electrocatalytic oxygen reduction reaction, which specifically includes the following steps.

[0031] (1) Weigh 1.0 mmol nickel sulfate hexahydrate, 2.5 mmol urea and 2.5 mmol glucose respectively in 60 mL deionized water, stir to dissolve, and place the resulting solution in a polytetrafluoroethylene hydrothermal reactor, seal it and place it in a 140 ℃ oven for hydrothermal treatment for 18.0 h. After the hydrothermal reaction is completed, separate the solid product by centrifugation, wash the solid product with deionized water and anhydrous ethanol three times each, and finally place it in an 80 ℃ oven to dry for 12.0 h.

[0032] (2) The dried solid product obtained in (1) was placed in an Ar atmosphere, heated to 500 °C at 5 °C / min, and maintained for 3.0 h.

[0033] (3) Finally, the calcined sample was treated with 1.0 M sulfuric acid at 60 °C for 18.0 h, and then washed with deionized water and anhydrous ethanol and dried at 80 °C to obtain the Ni@2.5Gr catalyst.

[0034] Example 3

[0035] This embodiment is a method for preparing a few-layer graphene-wrapped Ni catalyst for producing hydrogen peroxide by electrocatalytic oxygen reduction reaction, which specifically includes the following steps.

[0036] (1) Weigh 1.0 mmol nickel acetate, 2.0 mmol urea, 1.5 mmol dicyandiamide, and 3.5 mmol fructose respectively into 60 mL deionized water and stir to dissolve. Then, place the resulting solution in a polytetrafluoroethylene hydrothermal autoclave, seal it, and place it in a 170 °C oven for hydrothermal treatment for 24.0 h.

[0037] After the hydrothermal reaction, the solid product was separated by centrifugation, washed with deionized water and anhydrous ethanol three times each, and finally dried in an oven at 80 °C for 12.0 h.

[0038] (2) The dried solid product obtained in (1) was placed in an Ar atmosphere, heated to 600 °C at 5 °C / min, and maintained for 3.0 h.

[0039] (3) Finally, the calcined sample was treated with 1.5 M sulfuric acid at 70 °C for 10.0 h, and then washed with deionized water and anhydrous ethanol and dried at 80 °C to obtain the Ni@3.5Gr catalyst.

[0040] Example 4

[0041] This embodiment is a method for preparing a few-layer graphene-wrapped Ni catalyst for producing hydrogen peroxide by electrocatalytic oxygen reduction reaction, which specifically includes the following steps.

[0042] (1) Weigh 0.5 mmol nickel chloride, 0.5 mmol nickel nitrate, 0.5 mmol melamine, 4.0 mmol dicyandiamide and 4.5 mmol lactose respectively in 60 mL deionized water, stir to dissolve, and place the resulting solution in a polytetrafluoroethylene hydrothermal reactor, seal it and place it in a 180 ℃ oven for hydrothermal treatment for 12.0 h. After the hydrothermal reaction is completed, centrifuge the obtained solid product, wash the obtained solid product with deionized water and anhydrous ethanol three times each, and finally place it in an 80 ℃ oven to dry for 12.0 h.

[0043] (2) The dried solid product obtained in (1) was placed in an Ar atmosphere, heated to 700 °C at 5 °C / min, and maintained for 3.0 h.

[0044] (3) Finally, the calcined sample was treated with 2.0 M sulfuric acid at 80 °C for 2.0 h. Finally, it was washed with deionized water and anhydrous ethanol and dried at 80 °C to obtain the Ni@4.5Gr catalyst.

[0045] Figure 1XRD spectra of the catalysts Ni@1.5Gr, Ni@2.5Gr, Ni@3.5Gr, and Ni@4.5Gr prepared in Examples 1 to 4. It can be seen from the figure that the four catalysts all have a broad peak at about 26°, indicating that the catalysts have a graphite carbon structure. The diffraction peaks of 44.5°, 51.9°, and 76.8° indicate that the four catalysts still have Ni retained after strong acid washing, and Ni is in a metallic state.

[0046] Figure 2 Transmission electron microscope photos of the catalysts Ni@1.5Gr, Ni@2.5Gr, Ni@3.5Gr, and Ni@4.5Gr prepared in Examples 1 to 4. It can be seen from the figure that the four catalysts all present a flower cluster structure, and the Ni particles are evenly distributed therein.

[0047] Figure 3 The high-resolution transmission electron microscopy photos of the catalysts Ni@1.5Gr, Ni@2.5Gr, Ni@3.5Gr, and Ni@4.5Gr prepared in Examples 1 to 4 are shown in Figure 1. As can be seen from the figure, Ni in the four catalysts is wrapped by a few-layer graphene.

[0048] Example 5

[0049] This embodiment uses a few-layer graphene-wrapped Ni catalyst to electrocatalyze oxygen reduction reaction to produce hydrogen peroxide, which specifically includes the following steps.

[0050] (1) After the obtained few-layer graphene-wrapped Ni catalysts (Ni@1.5Gr, Ni@2.5Gr, Ni@3.5Gr, Ni@4.5Gr) were ground evenly, 5 mg was dispersed in 1970 L isopropyl alcohol and 30 In the mixed solution of L 5 wt% Nafion, the concentration was 2.5 mg / mL and ultrasonication was performed for 30 min to obtain a uniformly mixed catalyst ink.

[0051] (2) Take the prepared catalyst ink and drop it on the surface of the rotating ring disk glassy carbon electrode (the catalyst loading is 150 g / cm 2 ), and then electrochemical tests were performed after drying.

[0052] (3) In the electrocatalytic oxygen reduction reaction test, the Ag / AgCl electrode was used as the reference electrode and the Pt wire electrode was used as the counter electrode in an oxygen-saturated 0.1 M HClO 4 The linear scan curve test was carried out at a rotation speed of 1600 rpm, a scan rate of 10 mV / s, and a test potential of 0~0.9 V (vs. RHE) on the disk electrode. The test potential on the ring electrode was 1.2 V (vs. RHE). The calculation formula for hydrogen peroxide selectivity and the number of transferred electrons n is as follows:

[0053]

[0054]

[0055] Among them I d and I r are the disk current and ring current, respectively, and N is the collection efficiency (0.383 after calibration).

[0056] Depend on Figures 4 to 6 It can be seen that in the voltage range of 0~0.35 V (vs. RHE):

[0057] Ni@1.5Gr to H 2 O 2 The selectivity can reach 77.9~83.1%; the electron transfer number n is 2.33~2.45.

[0058] Ni@2.5Gr to H 2 O 2 The selectivity can reach 79.5~83.2%; the electron transfer number n is 2.33~2.41.

[0059] Ni@3.5Gr to H 2 O 2 The selectivity can reach 92.6~99.6%; the electron transfer number n is 2.04~2.16.

[0060] Ni@4.5Gr to H 2 O 2 The selectivity can reach 92.7~96.3%; the electron transfer number n is 2.07~2.14.

[0061] Therefore, Ni@3.5Gr has the best catalytic activity for electrocatalytic oxygen reduction to produce hydrogen peroxide.

[0062] Example 6

[0063] This example uses a constant potential method to test the stability of a few-layer graphene-wrapped Ni catalyst (Ni@3.5Gr) in the electrocatalytic oxygen reduction reaction to produce hydrogen peroxide, which specifically includes the following steps.

[0064] 5 mg Ni@3.5Gr was dispersed in a mixed solution of 1970 μL isopropanol and 30 μL 5 wt% Nafion at a concentration of 2.5 mg / mL and added dropwise to a 1 cm×1 cm (1 cm 2 ) carbon paper surface (catalyst loading of 150 µg / cm 2 ), and then dried and subjected to constant potential test. The test was carried out in oxygen-saturated 0.1 M HClO 4The test was carried out in a , and the electrolyte was stirred with a magnetic stirrer and oxygen was continuously introduced during the test. The potential during the test was controlled at 0.23 V (vs. RHE).

[0065] Figure 6 This is a constant potential test of the catalyst obtained in Example 3. It can be seen that the obtained Ni@3Gr catalyst exhibits excellent stability and no obvious deactivation phenomenon occurs after 200.0 h of testing.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing hydrogen peroxide by electrocatalytic oxygen reduction, characterized in that: The few-layer graphene-wrapped Ni catalyst was dispersed in a solvent and dropped on the surface of a rotating ring-disk glassy carbon electrode. After drying, it was used as a working electrode for the electrocatalytic oxygen reduction reaction to prepare hydrogen peroxide.

2. The method for preparing hydrogen peroxide by electrocatalytic oxygen reduction according to claim 1, characterized in that: The few-layer graphene-wrapped Ni catalyst is Ni particles wrapped inside the few-layer graphene, wherein the Ni particle size is 1 to 50 nanometers, the mass content is 5% to 90%, and the few-layer graphene has 1 to 3 layers.

3. The method for preparing hydrogen peroxide by electrocatalytic oxygen reduction according to claim 2, characterized in that: The few-layer graphene-wrapped Ni catalyst is prepared by using metal salt, organic amine and carbon source as raw materials and hydrothermally treating the precursor, and then calcining the precursor in a N2 atmosphere and treating the catalyst with a sulfuric acid solution.

4. The method for preparing hydrogen peroxide by electrocatalytic oxygen reduction according to claim 3, characterized in that: The metal salt is one of nickel acetate, nickel nitrate, nickel sulfate, and nickel chloride, or a mixture of two or more thereof; the organic amine is one of ethanolamine, urea, dicyandiamide, and hexamethylenetetramine, or a mixture of two or more thereof; and the carbon source is one of furfural, furfuryl alcohol, glycerol, glucose, fructose, and lactose, or a mixture of two or more thereof.

5. The method for preparing hydrogen peroxide by electrocatalytic oxygen reduction according to claim 3, characterized in that: The molar ratio of the metal salt, the organic amine and the carbon source is 1:(0.5-2.0):(2.5-5.5).

6. The method for preparing hydrogen peroxide by electrocatalytic oxygen reduction according to claim 3, characterized in that: The reaction conditions of the hydrothermal treatment are 100-180°C for 2.0-24.0h; the calcination conditions are heating to 400-800°C at 3.0-5.0°C / min and maintaining for 2.0-8.0h; the concentration of the sulfuric acid solution is 0.1-2.0M, the temperature is 25-80°C, and the treatment time is 2.0-24.0h.

7. The method for preparing hydrogen peroxide by electrocatalytic oxygen reduction according to claim 1, characterized in that: The solvent is a mixed solution of isopropanol and 5 wt% Nafion, and the concentration of the few-layer graphene-wrapped Ni catalyst in the solvent is 2.5 mg / mL.

8. The method for preparing hydrogen peroxide by electrocatalytic oxygen reduction according to claim 1, characterized in that: The electrolyte for the electrocatalytic oxygen reduction reaction is a 0.1 M HClO4 solution, the test potential on the disk electrode is 0-0.9 V (vs. RHE), and the test potential on the ring electrode is 1.2 V (vs. RHE).

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