Nickel oxide doped manganese dioxide catalyst as well as preparation method and application thereof

Abstract

The invention discloses a nickel oxide doped manganese dioxide catalyst and a preparation method and application thereof.The catalyst is formed by in-situ growth of nickel oxide doped manganese dioxide on a carbon felt substrate through a solvothermal method. An aromatic compound as a reaction substrate is dissolved in an acidic solution as an anode reaction solution. A counter electrode is used in the cathode chamber, an acidic solution is used as a cathode reaction solution, and after the reaction is finished, aromatic aldehyde or aromatic ketone can be prepared through a post-treatment process. The catalyst has a high surface area and a porous structure, the specific surface area of an electrode is increased, a large number of reaction sites and active sites are provided for oxidation of a substrate, in addition, manganese dioxide provides more active sites due to doping of nickel oxide, formation of an intermediate is promoted, meanwhile, desorption of a product aromatic aldehyde is also promoted, and the catalytic activity of the catalyst is improved. Aromatic acid formed by excessive oxidation is prevented, and the nanorod-shaped three-dimensional structure of the catalyst is beneficial to mass transfer.

Description

Technical Field

[0001] The present invention belongs to the field of electrocatalytic materials, and particularly relates to a nickel oxide doped manganese dioxide catalyst, a preparation method thereof, and an application thereof in electrocatalytic oxidation for preparing aromatic aldehydes. Background Art

[0002] Due to their unique structures and reaction activities, aromatic aldehydes play a key role in organic synthesis and are widely used in the fields of chemical engineering, medicine, and materials, especially as important intermediates for spices, dyes, drugs, and polymer materials. However, traditional synthesis methods usually involve multiple steps, high energy consumption, and many by-products, which also pose challenges to the strict control of reaction selectivity and intermediate purity, and are not conducive to achieving the goal of green production.

[0003] The electrochemical oxidation method provides a new green and efficient way for the preparation of aromatic aldehydes: first, the aromatic compound is oxidized to a methyl alcohol intermediate, and then further oxidized to produce the target product aromatic aldehyde. However, the core challenge of this method is that at high current densities, the methyl alcohol intermediate is easily over-oxidized to by-products such as aromatic acids, thereby reducing the selectivity and yield of aromatic aldehydes. Therefore, optimizing the electrolysis conditions, selecting suitable electrode materials, and electrolyte systems become crucial.

[0004] At present, using nickel oxide doped manganese dioxide catalysts to improve this problem has potential advantages because such catalysts are expected to effectively inhibit the over-oxidation reaction of intermediates by increasing active sites and optimizing electron transfer, and achieve the preparation of aromatic aldehydes with high selectivity and high yield. However, there are no reports on the related applications of this catalytic system, which provides a new direction for future research. Summary of the Invention

[0005] Aiming at the above problems existing in the prior art, the purpose of the present invention is to overcome the problems of easy generation of by-products and low current density in the preparation process of electrocatalytic methylation of aromatic compounds. A nickel oxide doped manganese dioxide catalyst, a preparation method thereof, and an application thereof in electrocatalytic oxidation for preparing aromatic aldehydes are proposed. The nickel oxide doped manganese dioxide catalyst prepared by the present invention does not use precious metals, has a low cost, and by introducing potassium fluoride during the preparation of the catalyst, the disordered stacking is inhibited, the formation of a porous structure is promoted, the specific surface area is increased, and more active sites are exposed. And the reaction conditions of the electrocatalytic oxidation method are mild and the reaction rate and process can be precisely controlled by adjusting the electrolysis conditions, and a relatively large current density can be achieved during the electrolysis process to obtain a higher space-time yield.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A preparation method of a nickel oxide doped manganese dioxide catalyst, comprising the following steps:

[0008] 1) Put the carbon felt into a muffle furnace for high-temperature activation hydrophilic treatment, and then put it into nitric acid, acetone, and ethanol respectively for ultrasonic treatment for 0.5 - 3 h to obtain the pretreated carbon felt;

[0009] 2) Dissolve nickel salt, manganese salt, and potassium fluoride in deionized water to prepare a reaction solution;

[0010] 3) Immerse the pretreated carbon felt in step 1) fully in the reaction solution in step 2), and transfer it to a reaction kettle with a polytetrafluoroethylene liner for solvothermal reaction at high temperature. After the reaction, cool it to room temperature, take out the hydrothermal carbon felt, wash it repeatedly with distilled water and ethanol, and dry it to obtain the catalyst precursor doped with Ni(OH) 2 manganese dioxide;

[0011] 4) After the drying in step 3) is completed, transfer the catalyst precursor to a tubular furnace for heat treatment. Carry out calcination treatment in an air atmosphere, and control the temperature within a specific range to promote its transformation into a manganese dioxide phase with good structural stability, that is, obtain the nickel oxide doped manganese dioxide catalyst.

[0012] Furthermore, in step 1), the temperature for high-temperature activation in the muffle furnace is 300 - 600 °C, and the treatment time is 0.5 - 3 h; in step 3), the temperature of the solvothermal reaction is 120 - 180 °C, and the time of the solvothermal reaction is 6 - 24 h; in step 2), the molar ratio of the manganese salt to the nickel salt is 3 - 8:1, preferably 3 - 4:1, the air flow rate is 10 - 90 mL / min, in step 4), the heat treatment temperature is 300 - 500 °C, preferably 400 - 500 °C, and the heat preservation duration is 1 - 5 h, preferably 2 - 3 h.

[0013] Furthermore, the manganese salt is manganese nitrate tetrahydrate, potassium permanganate, manganese chloride, manganese acetylacetonate, or manganese sulfate; the nickel salt is nickel chloride, nickel acetylacetonate, or nickel nitrate hexahydrate.

[0014] The present invention also provides a nickel oxide doped manganese dioxide catalyst prepared by the above preparation method.

[0015] The present invention also defines the application of the above-mentioned nickel oxide-doped manganese dioxide catalyst in the electrocatalytic oxidation for preparing aromatic aldehydes. Using an aromatic compound (a) as the reaction substrate, a flow-type diaphragm electrolytic cell is adopted during the constant current electrolysis process, and an electrochemical workstation is used to control the current magnitude. The anode chamber and the cathode chamber of the flow-type diaphragm electrolytic cell are separated by an ion exchange membrane. The nickel oxide-doped manganese dioxide catalyst electrode serves as the anode chamber electrode, and the aromatic compound (a) is dissolved in an acidic solution as the anolyte; a cathode chamber electrode is arranged in the cathode chamber, and an acidic solution is used as the catholyte to carry out the constant current electrolysis reaction. The reaction time is 0.5 - 3 h. After the reaction, the anolyte is post-treated to obtain the product of formula (b). The reaction equation is as follows:

[0016]

[0017] In the formula, R on the intermediate 1 is a benzene ring-containing group and R 2 represents a benzene ring-containing group or hydrogen.

[0018] Further, the main solvent of the acidic solution used for the anode and the cathode is hydrochloric acid solution, sulfuric acid solution, nitric acid solution, acetic acid, methanesulfonic acid or perchloric acid, preferably sulfuric acid solution, and its concentration is 0.05 - 2.0 mol / L.

[0019] Further, the present invention also defines that the secondary solvent in the anode chamber is one of tetrahydrofuran, dichloromethane, acetonitrile or acetone, and the volume ratio of the main solvent to the secondary solvent is 3:7 - 7:3. The above-mentioned main solvent serves as the main electrolyte for the electrolysis reaction, and the secondary solvent is used to dissolve the aromatic compound reactant.

[0020] Further, the present invention also defines that the total volume of the cathode chamber and the anode chamber is 50 - 250 mL.

[0021] Further, the present invention also defines that the concentration of the aromatic compound in the anolyte is 10 - 50 mmol / L, preferably 10 - 30 mmol / L.

[0022] Further, the present invention also defines that during the constant current electrolysis reaction, the current density is 20 - 200 mA / cm 2 ; the cathode chamber electrode is a carbon felt.

[0023] Further, the present invention also defines that during the constant current electrolysis process, the pH of the anodic reaction solution is stable at 0 - 4; the temperature of the constant temperature water bath during the reaction is 30 - 70 °C, the voltage between the cathode and the anode is 1 - 10 V, and the reaction time is 0.5 - 3 h.

[0024] Further, the present invention also defines that the organic solvent for extraction is ethyl acetate, dichloromethane, chloroform or carbon tetrachloride.

[0025] Furthermore, in the method for electrocatalytic oxidation of nickel oxide doped manganese dioxide catalyst to prepare aromatic aldehyde, the nickel oxide doped manganese dioxide catalyst electrode is prepared by in-situ growth of nickel oxide doped manganese dioxide catalyst on the surface of a carbon felt as an electrode substrate through a solvothermal method. The loading amount of the nickel oxide doped manganese dioxide catalyst on the carbon felt is 10-20 mg / cm 2 .

[0026] Furthermore, after the reaction is completed, the post-treatment process of the anolyte is as follows: after the electro-oxidation reaction, first use 0.5 M sodium hydroxide solution to neutralize the reaction solution and adjust the pH to neutral; then, transfer the solution to a separatory funnel, add an organic solvent for extraction to obtain an organic phase extract, and then take the organic phase extract for rectification to obtain the target product; the organic solvents used for extraction are ethyl acetate, toluene, dichloromethane, chloroform or carbon tetrachloride.

[0027] By adopting the above technologies, compared with the prior art, the beneficial effects obtained by the present invention are as follows:

[0028] By implementing the above technical solutions, compared with the prior art, the present invention shows significant advantages in terms of catalytic performance, environmental friendliness and economy, specifically reflected in the following aspects:

[0029] (1) The present invention uses nickel oxide doped manganese dioxide (NiO-MnO 2 ) nanorods as an electrocatalyst. Its unique doping strategy combined with a three-dimensional porous structure significantly increases the specific surface area and active site density of the catalyst, thereby enhancing the mass transfer efficiency of reactants and electrocatalytic activity. In the electrocatalytic oxidation reaction of 4-methoxytoluene (Example 1), under the conditions of a current density of 100 mA / cm 2 and a reaction time of 8000 s, the conversion rate of the substrate reaches 99.99%, the selectivity of the product aromatic aldehyde is as high as 95.53%, and a space-time yield of 5.85 kg / (m 3 ·h) is achieved, and the generation amount of the by-product aromatic acid is less than 1%. In contrast, the undoped catalyst (GF, Example 8) only shows a conversion rate of 68.21% and a selectivity of 69.30%, further confirming the key role of the NiO-MnO 2 doping structure in improving the reaction selectivity.

[0030] (2) The present invention provides an efficient and environmentally friendly electrocatalyst based on carbon felt and its application method. The carbon felt is used as the carrier of the catalyst, which has excellent liquid retention performance and can significantly extend the residence time of the reaction substrate, thereby ensuring sufficient reaction occurrence. On this basis, by in-situ growing nickel oxide-doped manganese dioxide nanorods on the surface of the carbon felt, the catalyst prepared by the present invention exhibits a large specific surface area, providing abundant reaction active sites for the oxidation of the substrate. At the same time, the doping of nickel oxide optimizes the performance of the catalyst. On the one hand, it improves the reaction selectivity by regulating the adsorption behavior of reaction intermediates, and on the other hand, it effectively promotes the rapid transfer of charges, enabling the catalyst to operate stably for a long time at a relatively high current density. Compared with traditional heavy metal catalysts, the catalyst system of the present invention is environmentally friendly, significantly reducing the potential pollution to the ecosystem and conforming to the sustainable development concept of green chemistry.

[0031] (3) The present invention uses a diaphragm flow-type electrolytic cell for the reaction, which can obtain a relatively high space-time yield. The aromatic aldehyde is directly obtained by electrocatalytic oxidation. The reaction steps are simple, the reaction process is at normal temperature and pressure, and the reaction conditions are mild and controllable. In addition, the catalyst does not use expensive noble metals and has a relatively low cost, with great economic value.

[0032] In summary, the present invention uses carbon felt as the catalyst carrier and in-situ grows nickel oxide-doped manganese dioxide nanorods on its surface, enabling the catalyst to have a high surface area and a porous structure, increasing the specific surface area of the electrode, providing a large number of reaction sites and active sites for the oxidation of the substrate. In addition, the doping of nickel oxide enables manganese dioxide to provide more active sites, promotes the formation of intermediates, and also promotes the desorption of the product aromatic aldehyde, preventing the formation of aromatic acids due to over-oxidation. Moreover, the nanorod-like three-dimensional structure of the catalyst is beneficial to mass transfer. Description of the Drawings

[0033] Figure 1 SEM observation image of the NiO-MnO 2 / GF catalyst in Example 1 at 20 μm;

[0034] Figure 2 SEM observation image of the NiO-MnO 2 / GF catalyst in Example 1 at 10 μm;

[0035] Figure 3 SEM observation image of the NiO-MnO 2 / GF catalyst in Example 1 at 5 nm;

[0036] Figure 4 Relative concentration change diagram of raw materials and products during the reaction in Example 1;

[0037] Figure 5NiO-MnO of Example 1 2 / GF-V1 catalyst in 0.5M H 2 SO 4 Linear sweep voltammetry curve of whether there is a substrate 4-methylanisole in the solution;

[0038] Figure 6 NiO-MnO of Example 1 2 and MnO 2 BET analysis. Inset in the figure: pore volume of NiO-MnO 2 ;

[0039] Figure 7 Conversion rate and yield changes of the 8th cycle reaction in Example 7. Detailed implementation mode

[0040] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other implementation manners obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope protected by the present invention.

[0041] Example 1: Synthesis of nickel oxide doped manganese dioxide catalyst and its application in electrocatalytic oxidation of 4-methylanisole

[0042] 1) Cut the carbon felt into a rectangle with a size of 3 cm × 3.5 cm, put it into a muffle furnace for 1 h of high-temperature hydrophilic treatment at 500 °C, and then ultrasonically treat the carbon felt with concentrated nitric acid, acetone and ethanol for 0.5 h.

[0043] 2) Subsequently, weigh 3.5 mmol of potassium permanganate, 1 mmol of nickel nitrate hexahydrate, and 2 mmol of potassium fluoride respectively, mix and dissolve them in 60 mL of deionized water, place them in an ultrasonic bath, and stir to dissolve them fully.

[0044] 3) Immerse the hydrophilic carbon felt obtained in step 1) fully in the solution obtained in step 2) and transfer it to a reaction kettle with a polytetrafluoroethylene lining, and carry out a solvothermal reaction at a high temperature. The reaction temperature is 140 °C and the time is 12 h. After the reaction, a manganese dioxide precursor doped with Ni(OH) 2 is obtained, and it is transferred to an oven for further drying to obtain a catalyst precursor.

[0045] 4) After drying, transfer the catalyst precursor to a tubular furnace for heat treatment. Conduct calcination treatment under an air atmosphere with a flow rate of 60 mL / min. Heat it at a rate of 5 °C / min to 450 °C and then keep it at a constant temperature for 2 h. Cool it to room temperature. The loading amount of the obtained nickel oxide-doped manganese dioxide catalyst on the carbon felt is 10 mg / cm 2 , labeled as NiO-MnO 2 / GF-V1, and its scanning electron microscope images are as shown in Figure 1 and Figure 2 . It can be found from Figure 1 and Figure 2 that the NiO-MnO 2 / GF-V1 catalyst grows uniformly on the surface of the carbon felt in the shape of nanorods, with a size of about 1 micron. At the same time, the high-resolution transmission electron microscope (HRTEM) image is as shown in Figure 3 , showing that the catalyst has lattice fringes of NiO and MnO 2 , and there is a hybrid interface between the two, which helps to regulate the electronic structure of MnO 2 and optimize its oxidation activity.

[0046] Test the catalytic performance of the NiO-MnO 2 / GF-V1 catalyst electrode prepared in Example 1. The specific method is as follows:

[0047] Figure 5 is the linear sweep voltammetry curve of the NiO-MnO 2 / GF-V1 catalyst in Example 1 in 0.5 M H 2 SO 4 solution to determine whether there is a substrate of 4-methylanisole. The LSV curve shows that after adding 4-methylanisole (1a) to NiO-MnO 2 / GF-V1, the anodic current density increases to 15.8 mA cm-2 at 1.2 V vs. RHE, and the oxidation onset potential shifts negatively from 1.15 V to 1.05 V vs. RHE (ΔE = 100 mV). This performance improvement is due to the synergistic effect of the NiO-MnO 2 heterostructure, which jointly optimizes charge transfer and substrate adsorption and significantly reduces the reaction energy barrier.

[0048] Systematically characterize the pore structures of NiO-MnO Figure 6 prepared in Example 1 and pure MnO 2 by nitrogen adsorption-desorption isotherms ( 2 ). The results show that NiO-MnO 2 presents a typical Type IV isotherm with an H3-type hysteresis loop, indicating that it has a hierarchical pore structure mainly composed of mesopores; while pure MnO 2It exhibits an approximate type-II isotherm characteristic, reflecting its microporous-nonporous property. BET specific surface area analysis shows that NiO-MnO 2 has a specific surface area as high as 94.79 m 2 ·g-1, which is about 6 times higher than that of pure MnO 2 (15.67 m 2 ·g-1). This significant difference is due to the regulatory effect of nickel doping on the crystal growth of MnO 2 . By calculating the pore size distribution through the BJH model ( Figure 6 inset), the pore size of NiO-MnO 2 is concentrated in the range of 2 - 30 nm (mesoporous range), and the cumulative pore volume reaches 0.43 cm 3 ·g-1, further confirming the formation of its three-dimensional interconnected porous network. This multi-level pore structure optimizes mass transfer and promotes the rapid diffusion of reactants and products.

[0049] Taking the above-obtained NiO-MnO 2 / GF-V1 catalyst directly as the anode, using an electrochemical workstation to control the current magnitude, and carrying out the reaction in a flow-type diaphragm electrolytic cell. The anode chamber and cathode chamber of the flow-type diaphragm electrolytic cell are separated by an ion exchange membrane. Weigh 20 mmol of 4-methylanisole (denoted as 1a) as the reaction substrate, dissolve it in 100 mL of acidic mixed solvent as the anode solution, where the main solvent is 0.5 mol / L sulfuric acid solution and the secondary solvent is acetonitrile, with a volume ratio of 4:6. Use carbon felt as the counter electrode in the cathode chamber and 0.5 mol / L sulfuric acid solution as the cathode liquid. Use a pH meter to monitor and maintain the pH of the anodic reaction solution at 0.5 - 1.5, the reaction system temperature at 30 °C, and the current density at 100 mA / cm 2 . After constant current electrolysis for 8000 s, when the anodic electrolytic solution is cooled to room temperature, it is repeatedly extracted 3 times with dichloromethane, and then the dichloromethane phase is evaporated and separated to obtain 4-methoxybenzaldehyde (denoted as 1b). As the reaction time increases, the raw material 1a gradually decreases and the main product 1b gradually increases. When the reaction reaches 8000 s, the conversion rate of 1a can reach 99.99%, the selectivity of 1b is 95.53%, and the calculated space-time yield can reach 5.85 Kg / (m 3 ·h).

[0050] Example 2: Synthesis of nickel oxide-doped manganese dioxide catalyst and its application in electrocatalytic oxidation of 4-nitrotoluene

[0051] 1) Cut the carbon felt into rectangles with a size of 3 cm × 3.5 cm, place it in a muffle furnace for 1 h of high-temperature hydrophilic treatment at 500 °C, and then ultrasonically treat the carbon felt with concentrated nitric acid, acetone, and ethanol for 0.5 h.

[0052] 2) Subsequently, 8 mmol of manganese nitrate tetrahydrate, 2 mmol of nickel acetylacetonate hexahydrate, and 2 mmol of potassium fluoride were weighed separately, mixed and dissolved in 60 mL of deionized water, placed in an ultrasonic bath, and ultrasonically stirred to ensure complete dissolution.

[0053] 3) The hydrophilic carbon felt obtained in step 1) was fully immersed in the solution obtained in step 2) and transferred to a reaction kettle with a polytetrafluoroethylene lining for solvothermal reaction at a high temperature. The reaction temperature was 180 °C and the time was 16 h. After the reaction, a manganese dioxide precursor doped with Ni(OH) 2 was obtained, which was transferred to an oven for further drying to obtain a catalyst precursor.

[0054] 4) After drying, the catalyst precursor was transferred to a tubular furnace for heat treatment. Under an air atmosphere with a flow rate of 60 mL / min, it was calcined. It was heated to 450 °C at a rate of 5 °C / min and then held at a constant temperature for 3 h, and then cooled to room temperature. The loading amount of the nickel oxide-doped manganese dioxide catalyst on the carbon felt was 10 mg / cm 2 , labeled as NiO-MnO 2 / GF-V2.

[0055] The catalytic performance of the NiO-MnO 2 / GF-V2 catalyst prepared in Example 2 was tested. The specific method was as follows:

[0056] The above-obtained NiO-MnO 2 / GF-V2 catalyst was directly used as the anode. The electrochemical workstation was used to control the current magnitude, and a flow-type diaphragm electrolytic cell was used for the reaction. The anode chamber and the cathode chamber of the flow-type diaphragm electrolytic cell were separated by an ion exchange membrane. 15 mmol of 4-nitrotoluene (denoted as 2a) was weighed as the reaction substrate and dissolved in 100 mL of an acidic mixed solvent as the anode solution. The main solvent was 1.0 mol / L nitric acid solution, and the secondary solvent was acetonitrile, with a volume ratio of 3:7. A carbon felt was used as the counter electrode in the cathode chamber, and 1.0 mol / L nitric acid solution was used as the cathode solution. The pH meter was used to monitor and maintain the pH of the anode reaction solution at 0 - 1.5, the reaction system temperature was 40 °C, and the current density was 100 mA / cm 2 , and constant current electrolysis was carried out for 5800 s. After the anode electrolytic solution was cooled to room temperature, it was repeatedly extracted 3 times with dichloromethane, and then the dichloromethane phase was evaporated and separated to obtain 4-nitrobenzaldehyde (denoted as 2b). As the reaction time increased, the raw material 2a gradually decreased, and the main product 2b gradually increased. When the reaction reached 5800 s, the conversion rate of 2a could reach 93.32%, the selectivity of 2b was 95.33%, and the calculated space-time yield could reach 6.26 Kg / (m 3 ·h).

[0057] Example 3: Synthesis of Nickel Oxide Doped Manganese Dioxide Catalyst and Its Application in Electrochemical Oxidation of 4-Fluorotoluene

[0058] 1) Cut the carbon felt into rectangles with a size of 3 cm × 3.5 cm, place it in a muffle furnace for high-temperature hydrophilic treatment at 500 °C for 2 h, and then ultrasonically treat the carbon felt with concentrated nitric acid, acetone, and ethanol for 0.5 h respectively.

[0059] 2) Subsequently, weigh 3 mmol of manganese chloride, 1 mmol of nickel sulfate, and 1 mmol of potassium fluoride respectively, mix them and dissolve them in 60 mL of deionized water, place them in an ultrasonic bath, and stir to dissolve them fully.

[0060] 3) Immerse the hydrophilic carbon felt obtained in step 1) fully in the solution obtained in step 2), transfer it to a reaction kettle with a polytetrafluoroethylene lining, and carry out a solvothermal reaction at a high temperature. The reaction temperature is 120 °C and the time is 12 h. After the reaction, a manganese dioxide precursor doped with Ni(OH) 2 is obtained, and it is transferred to an oven for further drying to obtain a catalyst precursor.

[0061] 4) After drying, transfer the catalyst precursor to a tubular furnace for heat treatment. Under an air atmosphere with a flow rate of 80 mL / min, carry out calcination treatment. Heat it to 450 °C at a rate of 5 °C / min and then keep it at a constant temperature for 4 h, and cool it to room temperature. The loading amount of the obtained nickel oxide doped manganese dioxide catalyst on the carbon felt is 8 mg / cm 2 , marked as NiO-MnO 2 / GF-V3.

[0062] Test the catalytic performance of the NiO-MnO 2 / GF-V3 catalyst prepared in Example 3. The specific method is as follows:

[0063] Use the above-obtained NiO-MnO 2 / GF-V3 catalyst directly as the anode, control the current size using an electrochemical workstation, and carry out the reaction using a flow-type diaphragm electrolytic cell. The anode chamber and the cathode chamber of the flow-type diaphragm electrolytic cell are separated by an ion exchange membrane. Weigh 50 mmol of 4-fluorotoluene (denoted as 3a) as the reaction substrate, dissolve it in 100 mL of an acidic mixed solvent as the anode solution, where the main solvent is 0.5 mol / L methanesulfonic acid solution and the secondary solvent is acetone, and the volume ratio is 1:1. Use a carbon felt as the counter electrode in the cathode chamber and 0.5 mol / L methanesulfonic acid solution as the cathode liquid. Use a pH meter to monitor and maintain the pH of the anode reaction solution at 0.5 - 2, the reaction system temperature is 30 °C, and the current density is 200 mA / cm 2, Constant current electrolysis was carried out for 10,000 s. After the anodic electrolytic solution was cooled to room temperature, it was repeatedly extracted with ethyl acetate three times, and then the ethyl acetate phase was evaporated and separated to obtain 4-fluorobenzaldehyde (denoted as 3b). As the reaction time increased, the raw material 3a gradually decreased and the main product 3b gradually increased. When the reaction reached 10,000 s, the conversion rate of 3a could reach 99.99%, the selectivity of 3b was 91.30%, and the calculated space-time yield could reach 20.40 Kg / (m 3 ·h).

[0064] Example 4: Synthesis of nickel oxide doped manganese dioxide catalyst and its application in electrocatalytic oxidation of diphenylmethane

[0065] 1) The carbon felt was cut into rectangles with a size of 3 cm × 3.5 cm, placed in a muffle furnace for high-temperature hydrophilic treatment at 500 °C for 2 h, and then the carbon felt was ultrasonically treated with concentrated nitric acid, acetone and ethanol for 0.5 h respectively.

[0066] 2) Subsequently, 6 mmol of manganese acetylacetonate, 2 mmol of nickel chloride, and 1 mmol of potassium fluoride were weighed and mixed and dissolved in 60 mL of deionized water, placed in an ultrasonic bath, and ultrasonically stirred to dissolve them fully.

[0067] 3) The hydrophilic carbon felt obtained in step 1) was fully immersed in the solution obtained in step 2) and transferred to a reaction kettle with a polytetrafluoroethylene lining, and a solvothermal reaction was carried out at a high temperature. The reaction temperature was 160 °C and the time was 24 h. After the reaction, a manganese dioxide precursor doped with Ni(OH) 2 was obtained, and it was transferred to an oven for further drying to obtain a catalyst precursor.

[0068] 4) After drying, the catalyst precursor was transferred to a tubular furnace for heat treatment. Under an air atmosphere of 80 mL / min, it was calcined, heated to 500 °C at a rate of 5 °C / min and then kept at a constant temperature for 4 h, and cooled to room temperature. The loading amount of the obtained nickel oxide doped manganese dioxide catalyst on the carbon felt was 15 mg / cm 2 , marked as NiO-MnO 2 / GF-V4.

[0069] The catalytic performance of the NiO-MnO 2 / GF-V4 catalyst prepared in Example 4 was tested. The specific method was as follows:

[0070] The NiO-MnO 2The / GF-V4 catalyst is directly used as the anode. The electrochemical workstation is used to control the current magnitude, and the reaction is carried out in a flow-through diaphragm electrolytic cell. The anode chamber and the cathode chamber of the flow-through diaphragm electrolytic cell are separated by an ion exchange membrane. Weigh 50 mmol of diphenylmethane (denoted as 4a) as the reaction substrate, dissolve it in 100 mL of acidic mixed solvent as the anode solution, where the main solvent is 2.0 mol / L acetic acid solution and the secondary solvent is tetrahydrofuran with a volume ratio of 7:3. A carbon felt is used as the counter electrode in the cathode chamber, and 2.0 mol / L acetic acid solution is used as the cathode solution. Use a pH meter to monitor and maintain the pH of the anode reaction solution at 2 - 4, the reaction system temperature is 60 °C, and the current density is 200 mA / cm 2 , for constant current electrolysis for 9700 s. After the anode electrolytic solution is cooled to room temperature, it is repeatedly extracted 3 times with ethyl acetate, and then the ethyl acetate phase is evaporated and separated to obtain benzophenone (denoted as 4b). As the reaction time increases, the raw material 4a gradually decreases, and the main product 4b gradually increases. When the reaction reaches 10000 s, the conversion rate of 4a can reach 99.99%, the selectivity of 4b is 96.50%, and the calculated space-time yield can reach 16.38 Kg / (m 3 ·h).

[0071] Example 5: Synthesis of nickel oxide doped manganese dioxide catalyst and its application in electrocatalytic oxidation of 4-trifluorotoluene

[0072] 1) Cut the carbon felt into rectangles with a size of 3 cm × 3.5 cm, put it into a muffle furnace for 2 h of high-temperature hydrophilic treatment at 500 °C, and then ultrasonically treat the carbon felt with concentrated nitric acid, acetone, and ethanol for 0.5 h respectively.

[0073] 2) Subsequently, weigh 6 mmol of manganese sulfate, 1 mmol of nickel chloride, and 1 mmol of potassium fluoride respectively, mix and dissolve them in 60 mL of deionized water, place them in an ultrasonic bath, and stir to fully dissolve them.

[0074] 3) Immerse the hydrophilic carbon felt obtained in step 1) fully in the solution obtained in step 2), and transfer it to a reaction kettle with a polytetrafluoroethylene lining for solvothermal reaction at a high temperature. The reaction temperature is 180 °C and the time is 8 h. After the reaction, a manganese dioxide precursor doped with Ni(OH) 2 is obtained, and it is transferred to an oven for further drying to obtain a catalyst precursor.

[0075] 4) After drying, transfer the catalyst precursor to a tubular furnace for heat treatment. Under an air atmosphere of 90 mL / min, it is calcined, heated to 450 °C at a rate of 5 °C / min and then kept at a constant temperature for 4 h, and cooled to room temperature. The loading amount of the nickel oxide doped manganese dioxide catalyst on the carbon felt is 5 mg / cm 2, labeled as NiO-MnO 2 / GF-V5.

[0076] For the NiO-MnO 2 / GF-V5 catalyst prepared in Example 5, the catalytic performance was tested, and the specific method is as follows:

[0077] The obtained NiO-MnO 2 / GF-V5 catalyst was directly used as the anode. Using an electrochemical workstation to control the current magnitude, a flow-type diaphragm electrolytic cell was used for the reaction. The anode chamber and the cathode chamber of the flow-type diaphragm electrolytic cell were separated by an ion exchange membrane. 20 mmol of 4-trifluoromethyltoluene (denoted as 5a) was weighed as the reaction substrate and dissolved in 100 mL of an acidic mixed solvent as the anode solution. The main solvent was 1.0 mol / L hydrochloric acid solution, and the secondary solvent was acetonitrile, with a volume ratio of 3:7. A carbon felt was used as the counter electrode in the cathode chamber, and 1.0 mol / L hydrochloric acid solution was used as the cathode solution. A pH meter was used to monitor and maintain the pH of the anodic reaction solution at 1 - 3, the reaction system temperature was 50 °C, and the current density was 50 mA / cm 2 , and constant current electrolysis was carried out for 8000 s. After the anodic electrolytic solution was cooled to room temperature, it was repeatedly extracted 3 times with dichloromethane, and then the dichlorotoluene phase was separated to obtain 4-trifluoromethylbenzaldehyde (denoted as 5b). As the reaction time increased, the raw material 5a gradually decreased, and the main product 5b gradually increased. When the reaction reached 8000 s, the conversion rate of 5a could reach 98.5%, the selectivity of 5b was 96.5%, and the calculated space-time yield could reach 7.53 Kg / (m 3 ·h).

[0078] Example 6: Synthesis of nickel oxide-doped manganese dioxide catalyst and its application in electrocatalytic oxidation of 4-methoxyethylbenzene

[0079] 1) Cut the carbon felt into rectangles with a size of 3 cm × 3.5 cm, put it into a muffle furnace for 2 h of high-temperature hydrophilic treatment at 500 °C, and then ultrasonically treat the carbon felt with concentrated nitric acid, acetone, and ethanol for 0.5 h.

[0080] 2) Subsequently, 8 mmol of manganese acetylacetonate, 1 mmol of nickel chloride, and 1 mmol of potassium fluoride were weighed respectively, mixed and dissolved in 60 mL of deionized water, placed in an ultrasonic bath, and ultrasonically stirred to fully dissolve them.

[0081] 3) Immerse the hydrophilic carbon felt obtained in step 1) fully in the solution obtained in step 2) and transfer it to a reaction kettle with a polytetrafluoroethylene lining, and carry out a solvothermal reaction at a high temperature. The reaction temperature was 180 °C and the time was 12 h. After the reaction, Ni(OH)-doped 2The manganese dioxide precursor is transferred into an oven for further drying to obtain the catalyst precursor.

[0082] 4) After the drying is completed, the catalyst precursor is transferred to a tubular furnace for heat treatment. Under an air atmosphere with a flow rate of 90 mL / min, it is calcined. It is heated to 450 °C at a rate of 5 °C / min and then held at a constant temperature for 4 h, and then cooled to room temperature. The loading amount of the obtained nickel oxide-doped manganese dioxide catalyst on the carbon felt is 12 mg / cm 2 , labeled as NiO-MnO 2 / GF-V6.

[0083] The catalytic performance of the NiO-MnO 2 / GF-V6 catalyst prepared in Example 6 was tested. The specific method is as follows:

[0084] The obtained NiO-MnO 2 / GF-V6 catalyst was directly used as the anode. The size of the current was controlled by an electrochemical workstation, and a flow-type diaphragm electrolytic cell was used for the reaction. The anode chamber and the cathode chamber of the flow-type diaphragm electrolytic cell were separated by an ion exchange membrane. 30 mmol of 4-methoxyethylbenzene (denoted as 6a) was weighed as the reaction substrate and dissolved in 100 mL of an acidic mixed solvent as the anode solution. The main solvent was 1.0 mol / L perchloric acid solution, and the secondary solvent was acetonitrile, with a volume ratio of 3:7. A carbon felt was used as the counter electrode in the cathode chamber, and 1.0 mol / L hydrochloric acid solution was used as the cathode solution. The pH meter was used to monitor and maintain the pH of the anodic reaction solution at 1-3, the reaction system temperature was 50 °C, and the current density was 200 mA / cm 2 , and constant current electrolysis was carried out for 5800 s. After the anodic electrolytic solution was cooled to room temperature, it was repeatedly extracted 3 times with dichloromethane, and then the dichlorotoluene phase was separated to obtain 4-methoxyacetophenone (denoted as 6b). As the reaction time increased, the raw material 6a gradually decreased, and the main product 6b gradually increased. When the reaction reached 5800 s, the conversion rate of 6a could reach 96.32%, the selectivity of 6b was 98.64%, and the calculated space-time yield could reach 26.57 Kg / (m 3 ·h).

[0085] Example 7: Preparation of nickel oxide-doped manganese dioxide catalyst and its electrocatalytic oxidation of 4-methylanisole

[0086] The preparation steps of the nickel oxide-doped manganese dioxide catalyst electrode in Example 7 were repeated in Example 1.

[0087] The catalytic performance of the NiO-MnO 2 / GF-V1 prepared in Example 1 was tested after 7 reactions. The specific method is as follows:

[0088] The NiO-MnO after 7 reactions 2 / GF-V1 catalyst was directly used as the anode. The current magnitude was controlled using an electrochemical workstation, and the reaction was carried out in a flow-through diaphragm electrolytic cell. The anode chamber and the cathode chamber of the flow-through diaphragm electrolytic cell were separated by an ion-exchange membrane. 20 mmol of 4-methylanisole was weighed as the reaction substrate and dissolved in 100 mL of an acidic mixed solvent as the anode solution. The main solvent was 0.5 mol / L sulfuric acid solution, and the secondary solvent was acetonitrile, with a volume ratio of 4:6. A carbon felt was used as the counter electrode in the cathode chamber, and 0.5 mol / L sulfuric acid solution was used as the cathode solution. A pH meter was used to monitor and maintain the pH of the anodic reaction solution at 0.5 - 1.5, the reaction system temperature was 30 °C, and the current density was 100 mA / cm 2 , and constant current electrolysis was carried out for 8000 s. After the anodic electrolytic solution was cooled to room temperature, it was repeatedly extracted with dichloromethane 3 times, and then the dichloromethane phase was evaporated and separated to obtain the 4-methoxybenzaldehyde product. After detection, the conversion rate was 99.9%, and the selectivity was 93.5%.

[0089] Example 7 was a cyclic reuse test of the nickel oxide-doped manganese dioxide catalyst. The yields and conversion rates of these eight reactions were as Figure 7 shown. At the same time, the yield of the oxidation product 4-methoxybenzaldehyde (1b) in the eighth reaction did not decrease significantly, proving the excellent stability of this catalyst.

[0090] Comparative Example 1: The catalytic performance of GF was tested. The specific method was as follows:

[0091] GF was directly used as the anode. The current magnitude was controlled using an electrochemical workstation, and the reaction was carried out in a flow-through diaphragm electrolytic cell. The anode chamber and the cathode chamber of the flow-through diaphragm electrolytic cell were separated by an ion-exchange membrane. 20 mmol of 4-methylanisole (denoted as 1a) was weighed as the reaction substrate and dissolved in 100 mL of an acidic mixed solvent as the anode solution. The main solvent was 0.5 mol / L sulfuric acid solution, and the secondary solvent was acetonitrile, with a volume ratio of 4:6. A carbon felt was used as the counter electrode in the cathode chamber, and 0.5 mol / L sulfuric acid solution was used as the cathode solution. A pH meter was used to monitor and maintain the pH of the anodic reaction solution at 0.5 - 1.5, the reaction system temperature was 30 °C, and the current density was 100 mA / cm 2 , and constant current electrolysis was carried out for 8000 s. After the anodic electrolytic solution was cooled to room temperature, it was repeatedly extracted with dichloromethane 3 times, and then the dichloromethane phase was evaporated and separated to obtain 4-methoxybenzaldehyde (denoted as 1b). As the reaction time increased, the raw material 1a gradually decreased, and the main product 1b gradually increased. When the reaction reached 8000 s, the conversion rate of 1a could reach 68.21%, the selectivity of 1b was 69.30%, and the calculated space-time yield could reach 2.90 Kg / (m3 · h)

[0092] For the electrocatalytic methyl oxidation reaction of aromatic compounds, compare the six catalysts prepared above

[0093] (NiO - MnO 2 / GF, GF) under different instances in terms of conversion rate, selectivity and space - time yield. The results are shown in Table 1

[0094] Comparative Example 2: Test the catalytic performance of MnO 2 / GF. The specific method is as follows

[0095] 1) Cut the carbon felt into rectangles with a size of 3 cm × 3.5 cm, put it into a muffle furnace for 1 h of high - temperature hydrophilic treatment at 500 °C, and then ultrasonically treat the carbon felt with concentrated nitric acid, acetone and ethanol for 0.5 h

[0096] 2) Subsequently, weigh 3.5 mmol of potassium permanganate and 2 mmol of potassium fluoride respectively, mix them and dissolve them in 60 mL of deionized water in an ultrasonic bath, and stir to dissolve them fully

[0097] 3) Immerse the hydrophilic carbon felt obtained in step 1) fully into the solution obtained in step 2) and transfer it to a reaction kettle with a polytetrafluoroethylene lining, and carry out a solvothermal reaction at a high temperature. The reaction temperature is 140 °C and the time is 12 h. After the reaction, obtain the manganese dioxide precursor, transfer it to an oven for further drying to obtain the catalyst precursor

[0098] 4) After drying, transfer the catalyst precursor to a tubular furnace for heat treatment. Carry out calcination treatment under an air atmosphere with a flow rate of 60 mL / min. Heat it to 450 °C at a rate of 5 °C / min and then keep it at a constant temperature for 2 h, and cool it to room temperature. The loading amount of the nickel - doped manganese dioxide catalyst on the carbon felt is 9 mg / cm 2 , labeled as MnO 2 / GF

[0099] Transfer the obtained MnO 2The / GF catalyst is directly used as the anode. The size of the current is controlled by an electrochemical workstation, and the reaction is carried out in a flow-through diaphragm electrolytic cell. The anode chamber and the cathode chamber of the flow-through diaphragm electrolytic cell are separated by an ion-exchange membrane. 20 mmol of 4-methylanisole (denoted as 1a) is weighed as the reaction substrate and dissolved in 100 mL of an acidic mixed solvent as the anode solution. The main solvent is 0.5 mol / L sulfuric acid solution, and the secondary solvent is acetonitrile, with a volume ratio of 4:6. A carbon felt is used as the counter electrode in the cathode chamber, and 0.5 mol / L sulfuric acid solution is used as the cathode solution. A pH meter is used to monitor and maintain the pH of the anodic reaction solution at 0.5 - 1.5, the temperature of the reaction system is 30 °C, and the current density is 100 mA / cm 2 , and electrolysis is carried out at a constant current for 8000 s. After the anodic electrolytic solution is cooled to room temperature, it is repeatedly extracted 3 times with dichloromethane, and then the dichloromethane phase is evaporated and separated to obtain 4-methoxybenzaldehyde (denoted as 1b). As the reaction time increases, the raw material 1a gradually decreases, and the main product 1b gradually increases. When the reaction reaches 8000 s, the conversion rate of 1a can reach 96.4%, the selectivity of 1b is 80.6%, and the calculated space-time yield can reach 4.75 Kg / (m 3 ·h).

[0100] Table 1 Conversion rate, selectivity and space-time yield of the catalyst under different examples

[0101] Serial number Catalyst Conversion rate Selectivity <![CDATA[Spatial-time yield Kg / (m 3 ·h)]]> Example 1 <![CDATA[NiO-MnO 2 / GF-V1]]> 99.99％ 95.53％ 5.85 Example 2 <![CDATA[NiO-MnO 2 / GF-V2]]> 93.32％ 95.33％ 6.26 Example 3 <![CDATA[NiO-MnO 2 / GF-V3]]> 99.99％ 91.30％ 20.40 Example 4 <![CDATA[NiO-MnO 2 / GF-V4]]> 99.99％ 96.50％ 16.38 Example 5 <![CDATA[NiO-MnO 2 / GF-V5]]> 98.50％ 94.23％ 7.35 Example 6 <![CDATA[NiO-MnO 2 / GF-V6]]> 96.32％ 98.64％ 26.57 Example 7 <![CDATA[NiO-MnO 2 / GF-V1]]> 99.99％ 93.50％ 5.73 Comparative example 1 GF 68.21％ 69.30％ 2.90 Comparative example 2 <![CDATA[MnO 2 / GF]]> 96.4％ 80.6％ 4.75

[0102] As shown in Table 1, under different reaction conditions, NiO-MnO 2 / GF shows excellent conversion rate, selectivity and space-time yield in the electrocatalytic methyl oxidation reaction of aromatic compounds. In contrast, in Comparative Example 1, unloaded GF is used, and in Comparative Example 2, MnO 2 / GF is used. Although the substrate and other reaction conditions remain the same, their conversion rate, selectivity and space-time yield are significantly lower than those in Example 1. This shows that NiO-MnO 2 / GF has significantly better electrocatalytic activity than pure GF and MnO 2 / GF. Its performance advantage stems from the synergistic effect of nickel oxide and manganese dioxide doped on the catalyst surface, effectively increasing the number of active sites in the catalytic process, thus promoting the generation of key intermediates. In addition, the rod-shaped three-dimensional structure of this catalyst not only enhances the contact between the substrate and the catalyst, but also helps the timely desorption of the product aromatic aldehyde, thus inhibiting the generation of acid by-products caused by over-oxidation. This structural feature provides strong support for the high efficiency and selectivity of the reaction.

[0103] As described above, only some embodiments of the present invention are provided and are not used to limit the present invention. However, all equivalent changes and modifications made to the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a nickel oxide-doped manganese dioxide catalyst, characterized in that: The steps include: 1) placing the carbon felt in a muffle furnace for high temperature activation and hydrophilic treatment, and then placing it in nitric acid, acetone, and ethanol for ultrasonic treatment for 0.5-3 hours to obtain pretreated carbon felt; 2) dissolving nickel salt, manganese salt and potassium fluoride in deionized water to prepare a reaction solution; 3) fully immersing the carbon felt pretreated in step 1) in the reaction solution of step 2), and transferring it to a reactor lined with polytetrafluoroethylene to perform a solvent thermal reaction at high temperature, cooling it to room temperature after the reaction, taking out the hydrothermal carbon felt, repeatedly washing it with distilled water and ethanol, and drying it to obtain a catalyst precursor of Ni(OH)2 doped with manganese dioxide; 4) After the drying in step 3) is completed, the catalyst precursor is transferred to a tubular furnace for a heat treatment process, and calcined in an air atmosphere. The temperature is controlled within a specific range to promote its conversion into a manganese dioxide phase with good structural stability, thereby obtaining the nickel oxide-doped manganese dioxide catalyst.

2. The method for preparing a nickel oxide-doped manganese dioxide catalyst according to claim 1, characterized in that: In step 1), the temperature for high temperature activation in the muffle furnace is 300-600° C., and the treatment time is 0.5-3 h; in step 3), the temperature for the solvent thermal reaction is 120-180° C., and the solvent thermal reaction time is 6-24 h; in step 2), the ratio of the molar amount of manganese salt to the molar amount of nickel salt is 3-8:1, preferably 3-4:1, the air flow rate is 10-90 mL / min, and the heat treatment temperature in step 4) is 300-500° C., preferably 400-500° C., and the insulation time is 1-5 h, preferably 2-3 h.

3. The method for preparing a nickel oxide-doped manganese dioxide catalyst according to claim 1, characterized in that: The manganese salt is manganese nitrate tetrahydrate, potassium permanganate, manganese chloride, manganese acetylacetonate or manganese sulfate; the nickel salt is nickel chloride, nickel acetylacetonate or nickel nitrate hexahydrate.

4. A nickel oxide-doped manganese dioxide catalyst, characterized in that: The method is prepared according to any one of claims 1 to 3.

5. The use of a nickel oxide-doped manganese dioxide catalyst in electrocatalytic oxidation to produce aromatic aldehydes as claimed in claim 4, characterized in that: The aromatic compound (a) is used as a reaction substrate, a flow-type diaphragm electrolyzer is used in the constant current electrolysis process, and the current is controlled by an electrochemical workstation. The anode chamber and cathode chamber of the flow-type diaphragm electrolyzer are separated by an ion exchange membrane, and a nickel oxide-doped manganese dioxide catalyst electrode is used as an anode chamber electrode. The aromatic compound (a) is used as a reaction substrate and dissolved in an acidic solution as an anode liquid; a cathode chamber electrode is set in the cathode chamber, and an acidic solution is used as a cathode liquid to perform a constant current electrolysis reaction, and the reaction time is 0.5-3h. After the reaction is completed, the anode liquid is post-treated to obtain a product of formula (b). The reaction equation is as follows: In the formula, R1 on the intermediate is a benzene ring-bearing group and R2 represents a benzene ring-bearing group or hydrogen.

6. The use of a nickel oxide-doped manganese dioxide catalyst in electrocatalytic oxidation to produce aromatic aldehydes according to claim 5, characterized in that: The main solvent of the acid solution used in the anode and cathode is hydrochloric acid solution, sulfuric acid solution, nitric acid solution, acetic acid, phosphoric acid, methanesulfonic acid solution or perchloric acid solution, preferably sulfuric acid solution, and the concentration thereof is 0.05-2.0 mol / L; the secondary solvent in the anode chamber is one of tetrahydrofuran, dichloromethane, acetonitrile or acetone, and the volume ratio of the main solvent to the secondary solvent is 3:7-7:

3.

7. The use of a nickel oxide-doped manganese dioxide catalyst in electrocatalytic oxidation to produce aromatic aldehydes according to claim 5, characterized in that: The concentration of aromatic compounds in the anolyte is 10-50 mmol / L, preferably 10-30 mmol / L.

8. The use of a nickel oxide-doped manganese dioxide catalyst in electrocatalytic oxidation to produce aromatic aldehydes according to claim 5, characterized in that: When the constant current electrolysis reaction is carried out, the current density is 20-200mA / cm2; the cathode chamber electrode is carbon felt; during the constant current electrolysis process, the pH of the anode reaction liquid is 0-4; during the reaction, the temperature of the constant temperature water bath is 30-70°C, the cell voltage of the electrolytic cell is 1-10V, and the reaction time is 0.5-3h.

9. The use of a nickel oxide-doped manganese dioxide catalyst in electrocatalytic oxidation to produce aromatic aldehydes according to claim 5, characterized in that: After the reaction is completed, the process of post-treatment of the anolyte is as follows: after the electro-oxidation reaction, firstly, the reaction solution is neutralized with a 0.5M sodium hydroxide solution to adjust the pH to neutral; then, the solution is transferred to a separatory funnel, an organic solvent is added for extraction to obtain an organic phase extract, and then the organic phase extract is taken for distillation to obtain the target product; the organic solvent used for extraction is ethyl acetate, toluene, dichloromethane, chloroform or carbon tetrachloride.

10. The use of a nickel oxide-doped manganese dioxide catalyst in electrocatalytic oxidation to produce aromatic aldehydes according to claim 5, characterized in that: The nickel oxide doped manganese dioxide catalyst electrode is formed by in-situ growth of nickel oxide doped manganese dioxide catalyst on a carbon felt substrate by a solvothermal method. The loading amount of the nickel oxide doped manganese dioxide catalyst on the carbon felt is 10-20 mg / cm 2 .

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