Amorphous metal oxide-carbon composites and their use in electrocatalytic oxygen reduction synthesis of h2o2

Abstract

The application discloses an amorphous metal oxide-carbon composite material and application thereof in electrocatalytic oxygen reduction synthesis of H2O2, wherein the amorphous metal oxide-carbon composite material comprises porous carbon PC and amorphous metal oxide MO loaded on the porous carbon x The amorphous metal oxide-carbon composite material has excellent catalytic activity, double-electron ORR selectivity and long-time durability. Moreover, the preparation method of the amorphous metal oxide-carbon composite material has a simple technological process, the amorphous characteristic of the obtained metal oxide is extremely innovative, raw material cost is low, and the amorphous metal oxide-carbon composite material is beneficial to regulation and control, and is favorable to popularization of large-scale industrial utilization of electrocatalytic oxygen reduction preparation of H2O2.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to an amorphous metal oxide-carbon composite material and its application in the electrocatalytic oxygen reduction synthesis of H2O2. Background Technology

[0002] Hydrogen dioxide (H2O2), a multifunctional and environmentally friendly oxidant, is a crucial chemical in modern industry and is considered one of the 100 most important chemicals. It has wide applications in bleaching, textiles, chemical synthesis, wastewater treatment, disinfection, and semiconductor manufacturing. Currently, approximately 95% of H2O2 is synthesized via the anthraquinone process, which is energy-intensive, time-consuming, and produces abundant byproducts. Furthermore, the storage and transportation of high-concentration H2O2 pose serious safety hazards. These high costs and safety concerns have prompted industry and academia to develop alternative methods for synthesizing H2O2.

[0003] Currently, methods for synthesizing H2O2, besides the anthraquinone process commonly used in industry, include direct synthesis of H2 and O2, photocatalytic water oxidation, and electrocatalytic oxygen reduction. Among these, electrocatalytic oxygen reduction has attracted increasing attention due to its environmental friendliness and the ability to produce dilute H2O2 on-site, making it one of the most ideal technologies for H2O2 synthesis. The electrocatalytic oxygen reduction reaction (ORR) is a multi-electron reaction; taking an alkaline solution as an example, H2O is formed via a four-electron pathway (O2 + 2H2O + 4e-). - →4OH - H2O2 (O2 + H2O + 2e-) is formed via a two-electron (2-electron) route. - →HO2 - +OH - Both routes involve the same first intermediate, OOH*. Whether the product is H2O or H2O2 depends on the tendency of the OO bond to break. Further single-electron reduction of OOH* leads to the selective formation of H2O2, but further reduction to H2O is only inhibited on catalysts that can maintain the OO bond. Therefore, the key to achieving efficient and selective two-electron reduction of O2 lies in the rational design of catalysts with appropriate binding strength to OOH*.

[0004] Currently, common catalysts for the oxygen reduction synthesis of H2O2 mainly include noble metals, metal alloys, metal oxides, and carbon-based catalysts. Noble metals, represented by Pt, Au, and Pd, and their alloys are currently the most effective electrocatalysts; however, their large-scale application is limited by their high cost and scarcity. In contrast, metal oxides and carbon-based materials offer ample opportunities to modulate electrocatalytic performance. Reasonable modification can significantly improve catalytic performance, even rivaling that of noble metal catalysts. Amorphous metal oxides exhibit higher catalytic activity because they possess more coordinated unsaturated cation sites available for the reaction and are isotropic. Although research on amorphous metal oxides as two-electron ORR catalysts is very limited, carbon-based materials can improve the conductivity of catalysts, and their use as two-electron ORR electrocatalysts has been extensively studied. The pore characteristics, defect structure, and heteroatom doping of carbon-based materials can significantly alter activity, and the mesoporous structure facilitates mass transfer, promoting the release of generated H2O2 and preventing further reduction to H2O, thus leading to high selectivity for H2O2. Summary of the Invention

[0005] The purpose of this invention is to address the poor catalytic activity of two-electron ORR and the low efficiency of H2O2 preparation in existing technologies by providing an amorphous metal oxide-carbon composite material.

[0006] Another objective of this invention is to provide an application of amorphous metal oxide-carbon composite material in the electrocatalytic oxygen reduction synthesis of H2O2.

[0007] Another objective of this invention is to provide a method for preparing amorphous metal oxide-carbon composite materials.

[0008] The technical solution adopted to achieve the purpose of this invention is:

[0009] An amorphous metal oxide-carbon composite material includes porous carbon PC and an amorphous metal oxide MO supported on the porous carbon. x .

[0010] In the above technical solution, the amorphous metal oxide-carbon composite material is MO. x -PC, where M is a metal, PC is porous carbon, the mass of metal M is 5-40% of the sum of the masses of metal M and PC, and the preparation temperature of PC is 650-800℃, preferably 800℃.

[0011] In the above technical solution, the metal M is Ni, Bi or Cu, and the metal M is preferably Ni, and the mass of Ni is 20% of the sum of the masses of Ni and PC.

[0012] In the above technical solution, the MO xPC is prepared by the following method:

[0013] Step 1, Pyrolysis of sodium citrate to prepare PC: Weigh a predetermined amount of sodium citrate and calcine it. Let the calcined product cool naturally to room temperature.

[0014] Step 2: Grind the calcined product from Step 1 into powder in a mortar, acid wash, then water wash until neutral, and finally dry to obtain PC;

[0015] Step 3: Weigh out the corresponding mass of metal precursor according to the metal / (metal+PC) mass ratio of 5-40%, and disperse them separately in organic solvent to obtain dispersions;

[0016] Step 4: Ultrasonically treat the dispersion obtained in Step 3, then stir the dispersion until it becomes viscous, spread it evenly on aluminum foil, and let it dry to form a precursor film.

[0017] Step 5: Irradiate the precursor film obtained in Step 4 under a UV lamp. After irradiation, MO powder is obtained. x -PC.

[0018] In the above technical solution, the calcination method in step 1 involves placing sodium citrate in a boat and calcining it in a tube furnace under an Ar atmosphere, starting from room temperature and at a rate of 4-6°C per minute. -1 The temperature is increased at a rate of 650-800℃ and held for 0.9-1.1 hours, then cooled with the furnace.

[0019] In the above technical solution, the pickling solution in step 2 is an aqueous solution of H2SO4, the concentration of the aqueous solution of H2SO4 is 0.4-0.6M, the drying temperature is 60-70℃, and the drying time is 24-30h.

[0020] The organic solvent in step 3 is a mixed solution of acetone and n-hexane, wherein the volume of acetone is greater than that of n-hexane, and the mass fraction of PC in the organic solvent is 1.9-2.1 mg / mL. -1 The metal precursor is 2-ethylhexanoate of metal M.

[0021] In the above technical solution, the ultrasonic treatment method in step 4 is to ultrasonically treat the dispersion in an ultrasonic cleaner for 30-35 minutes, the ultrasonic treatment temperature does not exceed 30°C, and ice is used to cool it down during the process.

[0022] The irradiation time in step 5 is 12-13 hours, and the wavelength of the ultraviolet lamp is 185-254 nm.

[0023] In another aspect, the present invention provides the application of the aforementioned amorphous metal oxide-carbon composite material as a catalyst in the electrocatalytic oxygen reduction synthesis of H2O2.

[0024] In the above technical solution, the amorphous metal oxide-carbon composite material is dispersed in isopropanol, water, PC, and Nafion, and ultrasonically treated to prepare ink. Then, the uniformly dispersed ink is dropped onto the RRDE electrode and dried. After drying, Nafion is dropped onto the RRDE electrode and dried to obtain the RRDE electrode loaded with the amorphous metal oxide-carbon composite material. The electrode is placed in KOH solution for electrolysis to prepare H2O2. The counter electrode is a Pt mesh and the reference electrode is Hg / HgO.

[0025] Another aspect of the present invention provides a method for preparing an amorphous metal oxide-carbon composite material, comprising the following steps:

[0026] Step 1, Pyrolysis of sodium citrate to prepare PC: Weigh a predetermined amount of sodium citrate and place it in a boat, calcine it in a tube furnace under an Ar atmosphere, and let the calcined product cool naturally to room temperature;

[0027] Step 2: Grind the calcined product from Step 1 into powder in a mortar, acid wash, then water wash until neutral, and finally dry to obtain PC;

[0028] Step 3: Weigh out the corresponding mass of metal precursor and PC according to the mass ratio of a of metal / (metal+PC) of 5-40%, and disperse them separately in an organic solvent to obtain a dispersion.

[0029] Step 4: Ultrasonically treat the dispersion obtained in Step 3, then stir the dispersion until it becomes viscous, spread it evenly on aluminum foil, and let it dry to form a precursor film.

[0030] Step 5: Irradiate the precursor film obtained in Step 4 under a UV lamp. After irradiation, MO powder is obtained. x -PC;

[0031] Step 6, the MO prepared in step 5 x - PC powder was placed in a boat and calcined in a tube furnace under an Ar atmosphere. After calcination, the calcined product was naturally cooled to room temperature.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] 1. The amorphous metal oxide-carbon composite material of the present invention exhibits excellent catalytic activity, two-electron ORR selectivity, and long-term durability as a catalyst. Furthermore, the preparation method of the amorphous metal oxide-carbon composite material is simple, the amorphous properties of the obtained metal oxide are highly innovative, the raw material cost is low and easily controlled, which is conducive to promoting the large-scale industrial application of electrocatalytic oxygen reduction to prepare H2O2.

[0034] 2. In this invention, amorphous metal oxides are the main components promoting two-electron ORR activity, and the amorphous metal oxide-carbon composite material as a catalyst exhibits higher two-electron ORR selectivity than its crystalline counterpart. To improve the catalyst's conductivity, porous carbon PC with a high specific surface area and mesoporous structure is supported. Its abundant mesoporous structure also facilitates the timely release of generated H2O2 from the catalyst channels, preventing further reduction to H2O.

[0035] 3. The NiO of the present invention x PC composite materials, when used as catalysts, significantly enhance the activity and selectivity of H2O2 formation compared to conventional metal oxide catalysts and carbon material catalysts. The catalyst performance can be further improved by altering the Ni content and the PC preparation temperature. Compared to other types of catalysts, they offer advantages such as low cost, simple preparation methods, high selectivity, high activity, and excellent durability.

[0036] 4. This invention employs the PMOD method to prepare amorphous metal oxide-carbon composite materials. Compared with traditional methods such as impregnation, co-precipitation, and solvothermal methods, this method is simpler to operate. The metal oxides can be well loaded onto the carbon material, and the amorphous nature of the metal oxides, with its abundant unsaturated sites and isotropic characteristics, contributes to improved two-electron ORR selectivity. Furthermore, this method is simple and easy to implement, significantly reducing operational difficulty and improving cost-effectiveness, thus facilitating the practical development of electrocatalytic oxygen reduction synthesis of H2O2. Attached Figure Description

[0037] Figure 1 The NiO of this invention x (20%)-PC(b) composite material, catalytic two-electron ORR performance at different PC preparation temperatures (b = 650-800℃), (a) is the LSV curve tested under O2 atmosphere, scan rate of 10 mV / s, rotation speed of 1600 rpm, (b) is the ratio of the number of transferred electrons n to HO2. - Production relationship diagram.

[0038] Figure 2This is a graph showing the catalytic two-electron ORR performance of PC(b) of the present invention at different PC preparation temperatures (y = 650-800℃). (a) is the LSV curve tested under O2 atmosphere at a scan rate of 10 mV / s and a rotation speed of 1600 rpm. (b) is the curve showing the relationship between the number of transferred electrons n and HO2. - Production relationship diagram.

[0039] Figure 3 The NiO of this invention x (a) Catalytic two-electron ORR performance of PC (800℃) composite material under different Ni contents (a=0, 5-40%), (a) is the LSV curve tested under O2 atmosphere, scan rate of 10mV / s, rotation speed of 1600rpm, (b) is the relationship between the number of transferred electrons n and HO2. - Production relationship diagram.

[0040] Figure 4 (a) is the NiO of the present invention. x Long-term durability test curve of (20%)-PC (800℃) composite material. Figure 4 (b) is the SEM image after the test.

[0041] Figure 5 The NiO of this invention x Catalytic two-electron ORR performance of (20%)-PC (800℃) composite material at different calcination temperatures (200, 400, 600℃). (a) is the LSV curve tested under O2 atmosphere at a scan rate of 10 mV / s and a rotation speed of 1600 rpm. (b) is the relationship between the number of transferred electrons n and HO2. - Production relationship diagram.

[0042] Figure 6 The PC and NiO of this invention x XRD patterns of (20%)-PC (800℃) composite material and its calcined products.

[0043] Figure 7 The NiO of this invention x XPS spectra of (20%)-PC (800℃) composite material and its calcined products: (a) Ni 2p spectrum, (b) O 1s spectrum, (c) C 1s spectrum.

[0044] Figure 8 (a) is a SEM image of carbon material PC(800), and (b) is a NiO loaded using the PMOD process. x NiO after x SEM image of PC composite material, 8(c) shows NiO. xAdsorption isotherms of (20%)-PC (800℃) composite material and its calcined products, 8(d) is NiO x Pore ​​size distribution of (20%)-PC (800℃) composite material and its calcined products.

[0045] Figure 9 The NiO of this invention x S of (20%)-PC (800℃) composite material and its calcined products meso / S BET With HO2 - Production relationship diagram.

[0046] MO above x In (a)-PC(b), 'a' represents the percentage of the mass of metal M in the total mass of metal M and PC, and 'b' represents the preparation temperature of PC. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0048] Example 1

[0049] An amorphous metal oxide-carbon composite material is prepared by the following steps:

[0050] Step 1: Weigh 3g of sodium citrate and calcine it in a tube furnace under an Ar atmosphere for 1 hour. The heating rate of the tube furnace is 5℃ / min. -1 The calcination temperature is 800℃. The calcined product is allowed to cool naturally to room temperature. Compared to potassium citrate, sodium citrate has the following advantages: 1. Alkali metal elements are generated during pyrolysis, and potassium is too reactive, which can damage the instrument. 2. The advantage of sodium citrate pyrolysis PC compared to potassium citrate is that it generates more mesopores, which is beneficial for high selectivity.

[0051] Step 2: The calcined product is washed with 0.5M H2SO4 and deionized water until neutral, and then dried in a vacuum drying oven for 24 hours at a temperature of 60℃. The prepared PC is called PC (800℃).

[0052] Step 3: Weigh 20 mg of nickel 2-ethylhexanoate precursor (Ni mass fraction in the whole organic precursor is 12.5%) and 10 mg of PC according to a mass ratio of a = 20%. Disperse them separately in a mixed solution of 3 mL acetone and 2 mL n-hexane to prepare dispersions.

[0053] Step 4: Sonicate the prepared dispersion in an ultrasonic cleaner for 30 minutes, controlling the ultrasonic temperature at 20-30℃. Afterward, stir the ultrasonically treated dispersion until it becomes viscous, spread it evenly on aluminum foil, and let it air dry.

[0054] Step 5: Irradiate the precursor film under ultraviolet lamps with wavelengths of 185 nm and 254 nm for 12 hours to obtain NiO. x (20%)-PC (800℃) composite powder.

[0055] like Figure 6 As shown, for PC (800℃), due to its low degree of graphitization, it exhibits a broad diffraction peak at 23°. The prepared uncalcined NiO... x -PC and NiO calcined at 200℃ x The XRD spectrum of -PC is similar to that of PC, indicating that NiO x It exhibits amorphous properties. However, as the calcination temperature increases to 400℃, a NiO peak appears, and the intensity of the NiO peak increases with the presence of Ni metal upon calcination at 600℃. This is due to the presence of NiO in the composite material. x Caused by carbon reduction.

[0056] like Figure 7 As shown, (a) is the Ni 2p spectrum. For the uncalcined and calcined composite materials at 200℃, Ni mainly exists as Ni 2+ NiO exists in the form of PC surface, with a binding energy of approximately 856.5 / 874.2 eV. When the calcination temperature increases to 400℃ and 600℃, another peak appears at ~854.3 / 871.9 eV, indicating that NiO exists in this form. x Ni metal was formed by the reduction of carbon in the composite material. (b) shows the O 1s spectrum. For the uncalcined and calcined samples at 200℃, oxygen mainly exists in the carbonate (531.5eV-532eV) and hydroxide (531eV-533eV) on the surface; however, lattice oxygen (~530.0eV) appears in the samples calcined at ≥400℃, which is an indicator of crystallization. (c) shows the C 1s spectrum, which also confirms that the carbonate (binding energy is 288-289eV) is present. The other two peaks with binding energies of 284.8eV and ~286eV are assigned to CC and CO / C-OH, respectively.

[0057] like Figure 8 As shown in (a), the carbon material PC (800℃) has a three-dimensional honeycomb shape assembled from carbon sheets and numerous micron-sized macropores. Furthermore, each carbon sheet contains mesopores and micropores within its structure. Figure 8 Figure (b) shows NiO loaded via PMOD process. x NiO after x- The porosity of PC is significantly reduced, while that of NiO is reduced. x It penetrates into the pores. Nevertheless, mesopores and micropores still exist within each carbon sheet, which facilitates the exposure of active sites and mass transfer during the catalytic process. For example... Figure 8 As shown in (c), both Type I and Type IV isotherms were observed in all samples, indicating the coexistence of micropores and mesopores in the material. Figure 8 As shown in (d), through NiO x The pore size distribution of the (20%)-PC (800℃) composite material and its calcined products further confirms that mesopores and micropores still exist in each carbon sheet.

[0058] Example 2

[0059] By changing the preparation temperature of PC in step 1 of Example 1 to 650, 700, and 750°C, different PC(b) were prepared. The remaining preparation steps and testing conditions were basically the same as in Example 1, yielding NiO. x (20%)-PC(b) composite material.

[0060] Example 3

[0061] In Example 1, step 3, the mass ratio of Ni (x) was changed to 5%, 10%, 30%, and 40%, and the corresponding mass of nickel 2-ethylhexanoate precursor was weighed to prepare a dispersion. The remaining preparation steps and testing conditions were basically the same as in Example 1.

[0062] Comparative Example 1

[0063] Following the preparation steps of Example 1, but without adding the nickel 2-ethylhexanoate precursor, the two-electron ORR catalytic activity of the PC(b) pure carbon material was tested separately under the same preparation conditions.

[0064] Comparative Example 2

[0065] Following the preparation steps in Example 1, the prepared NiO x (20%)-PC (800℃) composite material was calcined in a tube furnace under Ar atmosphere for 1 hour. The heating rate of the tube furnace was controlled at 5℃ / min. -1 The calcination temperatures are 200, 400, and 600℃. The calcined products are then allowed to cool naturally to room temperature.

[0066] Example 5

[0067] The catalytic performance of the materials prepared in Examples 1-2 and Comparative Examples 1-2 was tested. The specific method was as follows: 2 mg of the composite material prepared in step 5 was dispersed in 250 μL isopropanol, 250 μL water, 0.5 mg PC (800℃), and 10 μL Nafion (5 wt%). The mixture was ultrasonically treated for 30 min to prepare ink, with the ultrasonic temperature controlled at 20-30℃. 12.5 μL of the uniformly dispersed ink was dropped onto an RRDE electrode and dried. Then, 4 μL of Nafion (0.5 wt%) was dropped onto the RRDE electrode and dried. PC (800℃) was used to improve the film-forming properties and conductivity of the prepared ink, making the film on the electrode more uniform; Nafion was used to improve the film-forming properties of the prepared ink, making the film on the electrode more uniform. The prepared electrode was tested for LSV to obtain the two-electron catalytic activity of the catalyst, and its durability was also tested. The electrolyte is 0.1M KOH, the counter electrode is a Pt mesh, and the reference electrode is Hg / HgO.

[0068] Based on the number of electrons transferred in ORR and the generation of HO2 - The molar fraction (in alkaline electrolyte) is used as an evaluation index for the selectivity of the catalyst for two-electron ORR. The formula is as follows:

[0069]

[0070]

[0071] In the formula, I disk It is the disk current, I ring It is the ring current, and N is the collection factor, which is determined by the size of the RRDE electrode and is 0.37 here.

[0072] like Figure 1 As shown in (a), the starting voltage is not significantly different without a catalyst, NiO x The (20%)-PC (800℃) composite material exhibits the best ORR catalytic activity, with an onset potential of 0.759V. For example... Figure 1 As shown in (b), the selectivity of different catalysts for H2O2 varies greatly. The selectivity of the catalysts increases almost in line with the increase of the preparation temperature of the PC substrate. NiO x (20%)-PC (800℃) composite material exhibits the best bi-electron ORR selectivity, HO2 - The mole fraction generated can reach 91% at 0.5V. This is also related to the pore structure and large specific surface area of ​​the composite material. When the PC substrate is prepared at a temperature below 650℃, a suitable pore structure is not generated, so discussing its two-electron ORR selectivity is meaningless.

[0073] like Figure 2As shown in (a), as a comparative example of Example 1, the study investigated the use of unsupported NiO. x The catalytic activity of pure PC materials was investigated. The onset voltage of ORR was significantly affected by different PC preparation temperatures, ranging from only 0.688V for PC (650℃) to 0.759V for PC (800℃). The catalytic activity gradually increased from PC (650℃) to PC (800℃), indicating that high-temperature PC preparation resulted in more active sites and a larger specific surface area, thus enhancing catalytic activity. Figure 2 As shown in (b), the selectivity of PC materials for H2O2 varies greatly. The selectivity of the catalyst increases almost with the increase of the preparation temperature of the PC substrate, which is different from that of the supported NiO. x The subsequent changes in catalyst selectivity showed the same trend, indicating that NiO x The loading only improved selectivity but did not affect the relative trends among these catalysts. NiO... x The presence of HO2 greatly enhances the selectivity of the two-electron ORR. Taking PC (800℃) as an example, HO2 - The mole fraction generated was only 68% at 0.5V, while the supported NiO x Afterwards, it can reach 91%, which indicates that NiO x The synergistic effect with PC enhances the selectivity of the catalyst for two-electron ORR.

[0074] like Figure 3 As shown, the supported NiO x Subsequently, the disk current decreased and showed no significant dependence on Ni content. However, for samples with Ni content of 5-20%, the ring current initially increased, indicating increased two-electron ORR selectivity and NiO. x The selectivity for two-electron ORR is significantly enhanced after loading, indicating that NiO x The synergistic effect between Ni and PC is essential for two-electron ORR. The ring current decreases with further increases in Ni content, as the increased metal oxide content affects the catalyst's conductivity. The sample containing 20% ​​Ni exhibits the highest two-electron ORR selectivity, with an onset potential of 0.759 V vs. RHE, HO2. - The mole fraction generated can reach 91% at 0.5V, and the number of transferred electrons n is 2.18. This indicates that NiO... x In the ORR process, the (20%)-PC (800℃) catalyst generates H2O2 almost entirely via a two-electron pathway, demonstrating strong application potential in the electrocatalytic oxygen reduction synthesis of H2O2.

[0075] like Figure 4As shown in (a), after 10,000 CV scans, both disk current and ring current decreased slightly, and the half-wave potential shifted negatively by 20 mV. Furthermore, the two-electron ORR selectivity changed slightly. SEM analysis at the end of the test showed that the microstructure was damaged to some extent, which is likely the reason for the performance degradation. However, the catalyst possesses a certain degree of robustness, combined with its high two-electron ORR selectivity (see...). Figure 4 (b) NiO prepared by this method x (20%)-PCPC (800℃) composite material has strong prospects for practical application.

[0076] like Figure 5 As shown, as a comparative example of Example 1, the study investigated NiO calcined at different temperatures. x The effect of crystallinity of (20%)-PCPC (800℃) composite material on two-electron ORR selectivity. The disk current showed no significant difference between the calcined and uncalcined samples at 200℃; however, calcination at 400℃ and 600℃ led to increased disk current and a positive shift in onset potential (0.80V and 0.78V for the 400℃ and 600℃ samples, respectively), indicating increased ORR activity. Conversely, calcination resulted in a decrease in ring current, indicating a decrease in two-electron ORR selectivity. The uncalcined sample exhibited a constant HO₂ content greater than 88% over a wide potential range of 0.2–0.6V. - The yield and n value were below 2.2, but the samples at 400 °C and 600 °C showed a rapid decrease in HO2 at potentials below 0.3 V. - Yield and the increase in n value. For samples calcined at 200, 400, and 600 °C, HO2 - The yields were 85.4%, 79.4%, and 82.9% at 0.5V, and 84.0%, 74.1%, and 72.0% at 0.2V. These results indicate that amorphous NiO... x -PC composites exhibit higher two-electron ORR selectivity than their crystalline counterparts, even outperforming many reported catalysts. Considering their ease of fabrication and excellent performance, amorphous NiO... x -PC composites can be a promising catalyst for the production of H2O2.

[0077] like Figure 9 As shown, the generated HO2 - mole fraction and S meso / S BET The correlation is almost linear, which proves that the pore structure of the catalyst is highly correlated with the catalytic performance, and also shows that the two-electron ORR selectivity is highly dependent on the proportion of mesopores.

[0078] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An amorphous metal oxide-carbon composite, characterized in that, porous carbon PC and amorphous metal oxide MO supported on the porous carbon x ; The amorphous metal oxide-carbon composite is MO x - PC, wherein the metal M is Ni, PC is porous carbon, the mass of the metal M is 5-40% of the sum of the masses of the metal M and PC, and the preparation temperature of the PC is 650-800°C; The amorphous metal oxide-carbon composite material is prepared by the following method: Step 1, preparing PC by pyrolyzing sodium citrate: weighing a predetermined amount of sodium citrate and calcining, and then naturally cooling the calcined product to room temperature; Step 2, grinding the calcined product of Step 1 into powder in a mortar, acid washing and then water washing to neutral, and finally drying to obtain PC; Step 3, weighing a corresponding amount of metal precursor according to the mass ratio of metal / (metal+PC) of 5-40%, and dispersing the metal precursor in an organic solvent to obtain a dispersion liquid; Step 4, ultrasonic treating the dispersion liquid obtained in Step 3, and then stirring the dispersion liquid to a viscous state, uniformly laying on an aluminum foil, and air-drying to form a precursor film; Step 5: The precursor thin film obtained in Step 4 is irradiated with a UV lamp, and a powder state MO is obtained after the irradiation is completed x - PC.

2. The amorphous metal oxide-carbon composite of claim 1, wherein, The mass of Ni is 20% of the sum of the masses of Ni and PC.

3. The amorphous metal oxide-carbon composite of claim 2, wherein, The method of calcination in step 1 is to place sodium citrate in a capsule, and in an Ar atmosphere, the temperature is raised at a rate of 4-6 ℃ min -1 from room temperature to 650-800 ℃ for 0.9-1.1 h, and then cooled with the furnace.

4. The amorphous metal oxide-carbon composite of claim 2, wherein, The acid washing solution in Step 2 is an aqueous solution of H2SO4, the concentration of the aqueous solution of H2SO4 is 0.4-0.6 M, the drying temperature is 60-70℃, and the drying time is 24-30 h; The organic solvent of step 3 is a mixed solution of acetone and n-hexane, the volume of acetone is greater than n-hexane, the mass fraction of PC in the organic solvent is 1.9-2.1 mg mL -1 , and the metal precursor is 2-ethylhexanoate of metal M.

5. The amorphous metal oxide-carbon composite of claim 2, wherein, The ultrasonic treating method in Step 4 is ultrasonic treating the dispersion liquid in an ultrasonic cleaner for 30-35 minutes, and the ultrasonic treating temperature is not more than 30℃, and ice blocks are used for cooling during the ultrasonic treating; The irradiation time in Step 5 is 12-13 h, and the wavelength of the ultraviolet lamp is 185-254 nm.

6. Application of the amorphous metal oxide-carbon composite material as claimed in any one of claims 1-5 as a catalyst in electrocatalytic oxygen reduction synthesis of H2O2.

7. Use according to claim 6, wherein the compound is ###0002### Taking the amorphous metal oxide-carbon composite material, dispersing in isopropyl alcohol, water, PC and Nafion, ultrasonic treating to prepare ink, and then taking the uniformly dispersed ink and dropping on a RRDE electrode, air-drying, and then taking Nafion and dropping on the RRDE electrode, air-drying to obtain a RRDE electrode loaded with the amorphous metal oxide-carbon composite material, and placing the RRDE electrode in a KOH solution for electrolysis to prepare H2O2, with a Pt mesh as the counter electrode and Hg / HgO as the reference electrode.

8. A method of producing an amorphous metal oxide-carbon composite according to claim 1, characterized by, Comprising the following steps: Step 1, preparing PC by pyrolyzing sodium citrate: weighing a predetermined amount of sodium citrate and placing in a capsule, and calcining in a tube furnace under Ar atmosphere, and then naturally cooling the calcined product to room temperature; Step 2, grinding the calcined product of Step 1 into powder in a mortar, acid washing and then water washing to neutral, and finally drying to obtain PC; Step 3, weighing a corresponding amount of metal precursor and PC according to the mass ratio of a of metal / (metal+PC) of 5-40%, and dispersing the metal precursor and PC in an organic solvent to obtain a dispersion liquid; Step 4, ultrasonic treating the dispersion liquid obtained in Step 3, and then stirring the dispersion liquid to a viscous state, uniformly laying on an aluminum foil, and air-drying to form a precursor film; Step 5: The precursor thin film obtained in Step 4 is irradiated with a UV lamp, and a powder state MO is obtained after the irradiation is completed x - PC; Step 6: The MO prepared in step 5 was calcined in a tube furnace under Ar atmosphere. After calcination, the calcined product was naturally cooled to room temperature. x - PC powder was placed in a canister and calcined in a tube furnace under Ar atmosphere. After calcination, the calcined product was naturally cooled to room temperature.

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