A method for electrocatalytic oxygen reduction for hydrogen peroxide production

Abstract

The application discloses a method for preparing hydrogen peroxide through electrocatalytic oxygen reduction, wherein an oligolayer graphene wrapped Ni catalyst is dispersed in a solvent and dropped on the surface of a rotating ring disc glassy carbon electrode, and after drying, the catalyst is used as a working electrode for preparing hydrogen peroxide through electrocatalytic oxygen reduction. The application adopts the oligolayer graphene wrapped Ni catalyst to produce hydrogen peroxide through electrocatalytic oxygen reduction, the catalyst is simple to prepare and easy to implement, and raw materials are cheap and easy to obtain. The obtained oligolayer graphene wrapped Ni catalyst has excellent selectivity and stability in the process of preparing hydrogen peroxide through electrocatalytic oxygen reduction in an acidic environment, and has important significance for industrialization of electrochemical preparation of hydrogen peroxide in an acidic environment.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials, and in particular to a method for preparing hydrogen peroxide by electrocatalytic oxygen reduction using a Ni catalyst encapsulated in oligolayer graphene. Background Technology

[0002] Hydrogen peroxide (H2O2) is widely recognized as one of the world's 100 most important chemicals. Due to its combined oxidizing and reducing properties, it is widely used in chemical synthesis, pharmaceutical preparation, industrial bleaching, military applications, food, and the environment. It produces no secondary pollution after use and is thus defined as a green chemical product. Currently, over 95% of hydrogen peroxide is produced in concentrated form using the anthraquinone process (see: Catal. Sci. Technol. 2016, 6 (6), 1593-1610). The industrial synthesis process involves hydrogenation, O2 oxidation of anthraquinone, and extraction purification, a multi-step process that increases energy consumption and production costs. Furthermore, the production process involves the use of toxic additives such as acid auxiliaries and halide ions. In addition, the current industrial applications consume a large amount of hydrogen peroxide in a 30% aqueous solution, and the concentration and purification process also generates a large amount of waste. The product distribution process also presents safety issues related to storage and transportation. Therefore, reducing the transportation costs of hydrogen peroxide and developing an economical, green, efficient, and sustainable method for its production is urgently needed.

[0003] In recent years, with the widespread application of renewable energy power generation, the electrochemical synthesis of hydrogen peroxide (through the input of renewable electricity to electrocatalyze 2e) has become increasingly important. - The ORR (Organic Reduction) synthesis of hydrogen peroxide has attracted widespread attention. This electrochemical method uses oxygen or water as raw materials, producing only water as a byproduct. It is environmentally friendly and has high atomic efficiency, providing a green, economical, and sustainable approach for in-situ hydrogen peroxide production. Currently, much research focuses on the electrocatalytic oxygen reduction to hydrogen peroxide production under alkaline conditions (see: CN 115505957 A, CN 117144395 A). However, in practical applications, the acidic environment method for producing hydrogen peroxide is more valuable. First, the acid dissociation constant of hydrogen peroxide (pKa = 11.7) means that its main form in acidic media is H₂O₂ rather than HO₂. -H2O2 exhibits stronger oxidizing power in acidic environments, enabling its effective utilization in various industrial processes. Secondly, hydrogen peroxide is more stable in acidic environments because higher pH values ​​promote its decomposition (see: J. Energy Chem. 2022, 67, 432-450). Furthermore, wastewater treatment and environmental remediation can also benefit from the direct electrosynthesis of hydrogen peroxide under acidic conditions. The optimal operating pH for the electro-Fenton process is approximately 3, which converts the generated hydrogen peroxide into more potent 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 hydrogen peroxide in acidic environments, most reported catalysts are noble metal-based catalysts, such as Pt and Pd. Although these catalysts have high activity and selectivity, the scarcity and high price of noble metals greatly affect their practical industrial applications. In recent years, carbon materials, with advantages such as low cost, good conductivity, and strong modifiability, have received widespread attention in the field of electrocatalytic oxygen reduction to hydrogen peroxide. CN 116043266 A discloses a CoPSe / C catalyst synthesized using MOF as a precursor and template through high-temperature annealing, simultaneous selenization, and phosphating. Under the conditions of 0.1M HClO4 as electrolyte and a potential range of 0.0–0.5V (vs. RHE), its selectivity for hydrogen peroxide is approximately 80%. CN 114892197 A discloses a series of carbon-supported transition metal catalysts. The optimal catalyst (Co supported on carbon black) exhibits approximately 90% selectivity for hydrogen peroxide under conditions of 0.1 M HClO4 as the electrolyte and a potential range of 0.0–0.6 V (vs. RHE), and can operate stably for 15 h. Based on the above research reports, there is still room for improvement in the selectivity of electrochemical oxygen reduction for hydrogen peroxide production in acidic systems. Therefore, developing a low-cost, efficient, and stable catalyst is of great significance for realizing the industrial process of electrochemical hydrogen peroxide production. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing hydrogen peroxide through electrocatalytic oxygen reduction.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing hydrogen peroxide by electrocatalytic oxygen reduction, wherein a Ni catalyst encapsulated in oligolayer graphene is dispersed in a solvent and dropped onto the surface of a rotating ring disk glassy carbon electrode, and after drying, it is used as a working electrode for the electrocatalytic oxygen reduction reaction to prepare hydrogen peroxide.

[0007] Furthermore, the Ni catalyst encapsulated in oligolayer graphene consists of Ni particles encapsulated within oligolayer graphene, wherein the Ni particles are 1–50 nanometers in size and have a mass content of 5%–90%, and the number of oligolayer graphene layers is 1–3.

[0008] Furthermore, the precursor of the oligolayer graphene-encapsulated Ni catalyst was obtained by hydrothermal treatment using metal salts, organic amines, and carbon sources as raw materials. The precursor was then calcined in an N2 atmosphere and treated with sulfuric acid solution to obtain the final product.

[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 metal salt, organic amine, and carbon source is 1:(0.5~2.0):(2.5~5.5).

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

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

[0013] Furthermore, the electrolyte for the electrocatalytic oxygen reduction reaction was a 0.1 M HClO4 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] This invention utilizes a Ni catalyst encapsulated in oligolayer graphene for electrocatalytic oxygen reduction to produce hydrogen peroxide. The catalyst preparation method is simple and easy to implement, using inexpensive and readily available raw materials. This catalytic route is environmentally friendly, operates under mild conditions, is highly controllable, utilizes renewable energy, and offers high economic benefits. The resulting oligolayer graphene-encapsulated Ni catalyst is low-cost and exhibits excellent selectivity and stability in the electrocatalytic oxygen reduction to hydrogen peroxide production process under acidic conditions, which is of great significance for the industrialization of electrochemical hydrogen peroxide production under acidic environments. Attached Figure Description

[0015] Figure 1 The images show typical XRD patterns of the Ni catalyst encapsulated in oligolayer graphene obtained in specific embodiments 1-4 of this invention.

[0016] Figure 2 These are typical transmission electron microscope (TEM) images of the Ni catalyst encapsulated in oligolayer graphene obtained in specific embodiments 1-4 of this invention.

[0017] Figure 3 These are typical high-resolution transmission electron microscope images of the Ni catalyst encapsulated in oligolayer graphene obtained in specific embodiments 1-4 of this invention.

[0018] Figure 4 Linear scanning curves of the oligolayer graphene-encapsulated Ni catalyst prepared in specific embodiments 1-4 of this invention for electrocatalytic oxygen reduction reaction.

[0019] Figure 5 The diagram shows the selectivity of the oligolayer graphene-encapsulated Ni catalyst prepared in specific embodiments 1-4 of this invention for the electrocatalytic oxygen reduction reaction to produce hydrogen peroxide.

[0020] Figure 6 The electron transfer figures for the oligolayer graphene-encapsulated Ni catalyst prepared in specific embodiments 1-4 of this invention for electrocatalytic oxygen reduction reaction are shown.

[0021] Figure 7 The current-time curve of the Ni catalyst encapsulated in oligolayer graphene prepared in specific embodiment 3 of the present invention for constant potential testing is shown. Detailed Implementation

[0022] 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 with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0023] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product or device.

[0024] Example 1

[0025] This embodiment describes a method for preparing an oligolayer graphene-encapsulated Ni catalyst for the electrocatalytic oxygen reduction reaction to produce hydrogen peroxide, specifically including the following steps.

[0026] (1) Weigh 1.0 mmol nickel nitrate, 1.5 mmol ethanolamine, 0.5 mmol glycerol and 1.0 mmol glucose into 60 mL deionized water, stir to dissolve, and place the resulting solution in a polytetrafluoroethylene hydrothermal reactor. After sealing, place the reactor in a 100℃ oven for hydrothermal treatment for 24.0 h. After the hydrothermal reaction is completed, centrifuge to separate the obtained solid product. Wash the obtained solid product three times each with deionized water and anhydrous ethanol, and finally dry it in an 80℃ oven for 12.0 h.

[0027] (2) The dried solid product obtained in (1) was placed in an Ar atmosphere and heated to 450 °C at 5 °C / min and kept 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, and then washed with deionized water and anhydrous ethanol and dried at 80 °C to obtain Ni@1.5Gr catalyst.

[0029] Example 2

[0030] This embodiment describes a method for preparing an oligolayer graphene-encapsulated Ni catalyst for the electrocatalytic oxygen reduction reaction to produce hydrogen peroxide, specifically including the following steps.

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

[0032] (2) The dried solid product obtained in (1) was placed in an Ar atmosphere and heated to 500 °C at 5 °C / min and kept 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 Ni@2.5Gr catalyst.

[0034] Example 3

[0035] This embodiment describes a method for preparing an oligolayer graphene-encapsulated Ni catalyst for the electrocatalytic oxygen reduction reaction to produce hydrogen peroxide, specifically including the following steps.

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

[0037] After the hydrothermal reaction was completed, the solid product obtained by centrifugation was washed three times each with deionized water and anhydrous ethanol, 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 and heated to 600 °C at 5 °C / min and kept 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 Ni@3.5Gr catalyst.

[0040] Example 4

[0041] This embodiment describes a method for preparing an oligolayer graphene-encapsulated Ni catalyst for the electrocatalytic oxygen reduction reaction to produce hydrogen peroxide, specifically including 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 into 60 mL deionized water, stir to dissolve, and place the resulting solution in a polytetrafluoroethylene hydrothermal reactor. After sealing, place the reactor in an oven at 180 °C for hydrothermal treatment for 12.0 h. After the hydrothermal reaction is completed, centrifuge to separate the obtained solid product. Wash the obtained solid product three times each with deionized water and anhydrous ethanol, and finally dry it in an oven at 80 °C for 12.0 h.

[0043] (2) The dried solid product obtained in (1) was placed in an Ar atmosphere and heated to 700 °C at 5 °C / min and kept 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, and then washed with deionized water and anhydrous ethanol and dried at 80 °C to obtain Ni@4.5Gr catalyst.

[0045] Figure 1The XRD patterns of the catalysts Ni@1.5Gr, Ni@2.5Gr, Ni@3.5Gr, and Ni@4.5Gr prepared in Examples 1-4 are shown. The figures show a broad peak at approximately 26°, indicating the presence of a graphitic carbon structure in all four catalysts. The diffraction peaks at 44.5°, 51.9°, and 76.8° indicate that Ni is retained in all four catalysts after strong acid washing, and that Ni is in a metallic state.

[0046] Figure 2 Transmission electron microscopy (TEM) images of the catalysts Ni@1.5Gr, Ni@2.5Gr, Ni@3.5Gr, and Ni@4.5Gr prepared in Examples 1-4. The images show that all four catalysts exhibit a flower-like structure with Ni particles uniformly distributed within it.

[0047] Figure 3 These are high-resolution transmission electron microscopy (TEM) images of the catalysts Ni@1.5Gr, Ni@2.5Gr, Ni@3.5Gr, and Ni@4.5Gr prepared in Examples 1-4. The images show that the Ni in all four catalysts is encapsulated in oligolayer graphene.

[0048] Example 5

[0049] This embodiment describes the production of hydrogen peroxide through an electrocatalytic oxygen reduction reaction using a Ni catalyst encapsulated in oligolayer graphene, and specifically includes the following steps.

[0050] (1) After grinding the obtained oligolayer graphene-coated Ni catalyst (Ni@1.5Gr, Ni@2.5Gr, Ni@3.5Gr, Ni@4.5Gr) evenly, 5 mg of the catalyst was dispersed in 1970. L isopropanol and 30 In a mixed solution of 5 wt% Nafion at a concentration of 2.5 mg / mL, the solution was sonicated for 30 min to obtain a homogeneous catalyst ink.

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

[0052] (3) During 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. The test was conducted in 0.1 M HClO4 saturated with oxygen. The rotation speed was 1600 rpm and the scan rate was 10 mV / s during the linear scan curve test. The test potential on the disk electrode was 0~0.9 V (vs. RHE). The test potential on the ring electrode was 1.2 V (vs. RHE). The formulas for calculating the hydrogen peroxide selectivity and the number of transferred electrons n are as follows:

[0053]

[0054]

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

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

[0057] Ni@1.5Gr exhibits a selectivity of 77.9% to 83.1% for H2O2, with an electron transfer number n of 2.33 to 2.45.

[0058] Ni@2.5Gr exhibits a selectivity of 79.5% to 83.2% for H2O2, with an electron transfer number n of 2.33 to 2.41.

[0059] Ni@3.5Gr exhibits a selectivity of 92.6% to 99.6% for H2O2, with an electron transfer number n of 2.04 to 2.16.

[0060] Ni@4.5Gr exhibits a selectivity of 92.7–96.3% for H2O2, with an electron transfer number n of 2.07–2.14.

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

[0062] Example 6

[0063] This embodiment describes the use of the constant potential method to test the stability of the electrocatalytic oxygen reduction reaction of oligolayer graphene-encapsulated Ni catalyst (Ni@3.5Gr) to produce hydrogen peroxide, specifically including 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, resulting in a concentration of 2.5 mg / mL. The solution was then added dropwise to a 1 cm × 1 cm (1 cm) droplet. 2 ) Carbon paper surface (catalyst loading of 150 µg / cm) 2 After drying, a constant potential test was performed. The test was conducted in oxygen-saturated 0.1 M HClO4, with the electrolyte stirred using a magnetic stirrer and oxygen continuously introduced during the test. The potential was controlled at 0.23 V (vs. RHE).

[0065] Figure 6The constant potential test of the catalyst obtained in Example 3 shows that the obtained Ni@3Gr catalyst exhibits excellent stability, and no obvious deactivation phenomenon was observed after 200.0 h of testing.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for the electrocatalytic oxygen reduction for the production of hydrogen peroxide, characterized in that: The oligolayer 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, the oligolayer graphene wrapped Ni catalyst is used as a working electrode for electrocatalytic oxygen reduction reaction to prepare hydrogen peroxide; The oligolayer graphene wrapped Ni catalyst is prepared by using a metal salt, an organic amine and a carbon source as raw materials, through hydrothermal treatment to obtain a precursor, and then through calcination in a N2 atmosphere and treatment with a sulfuric acid solution.

2. The method of electrocatalytic oxygen reduction for hydrogen peroxide production according to claim 1, characterized in that: The oligolayer graphene wrapped Ni catalyst is a Ni particle wrapped in an oligolayer graphene, wherein the size of the Ni particle is 1-50 nm, the mass content of the Ni particle is 5%-90%, and the number of layers of the oligolayer graphene is 1-3.

3. The method of electrocatalytic oxygen reduction for hydrogen peroxide production according to claim 1, characterized in that: 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.

4. The method of electrocatalytic oxygen reduction for hydrogen peroxide production according to claim 1, wherein: The molar ratio of the metal salt, the organic amine and the carbon source is 1:(0.5-2.0):(2.5-5.5).

5. The method of electrocatalytic oxygen reduction for hydrogen peroxide production according to claim 1, wherein: The reaction conditions of the hydrothermal treatment are 100-180 ℃ for 2.0-24.0 h; the calcination conditions are 3.0-5.0 ℃ / min to 400-800 ℃, and then maintaining at 400-800 ℃ for 2.0-8.0 h; the concentration of the sulfuric acid solution is 0.1-2.0 M, the temperature is 25-80 ℃, and the treatment time is 2.0-24.0 h.

6. The method of electrocatalytic oxygen reduction for hydrogen peroxide production according to claim 1, wherein: The solvent is a mixed solution of isopropyl alcohol and 5 wt% Nafion, and the concentration of the oligolayer graphene wrapped Ni catalyst in the solvent is 2.5 mg / mL.

7. The method of electrocatalytic oxygen reduction for hydrogen peroxide production according to claim 1, wherein: 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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