Application of niobium pentoxide

Abstract

The present invention relates to an application of niobium pentoxide for the electrocatalytic selective oxidation of alcohol, specifically comprising loading a niobium pentoxide catalyst on a nickel foam substrate to provide a working electrode, dissolving an alcohol as a reaction substrate in a neutral or alkaline aqueous solution as an electrolyte, and selectively oxidizing the alcohol to generate an acid using the niobium pentoxide catalyst in a three-electrode electrolytic cell system, wherein the surface of the niobium pentoxide catalyst has a short Nb-O bond as an active site. According to the application of niobium pentoxide of the present invention, acid is produced by highly selective electrocatalytic oxidation of alcohol by the niobium pentoxide catalyst, with the advantages of low starting potential and high current density. In particular, the present invention clearly defines short Nb-O bonds as active sites, which, when used in selective electrocatalytic oxidation reactions, are conducive to the selective oxidation of alcohol to high-value-added acid, have excellent conversion rate and selectivity, and greatly reduce the production cost and electrolysis energy consumption of electrocatalytic acid production.

Description

Technical Field

[0001] The present invention relates to the fields of electrocatalysis and fine chemical synthesis, and more particularly to an application of niobium pentoxide, which is an electrocatalytic method for anode selective electrocatalytic oxidation of alcohols. Background Art

[0002] With the development of the economy, oil resources have become scarce, which not only brings energy crisis to mankind, but also leads to shortages of various chemical raw materials in life. Therefore, seeking sustainable and renewable alternatives to chemical raw materials is an important goal at present.

[0003] The oxidation of alcohols is currently one of the most important pathways for producing acids, which are essential raw materials and intermediates in the pharmaceutical, specialty chemical, and fine chemical industries. Therefore, the selective oxidation of alcohols to produce acids holds promise for providing a rich source of raw materials for chemical production. However, efficient, environmentally friendly, and practical alcohol oxidation requires not only good product selectivity and high reactivity, but also inexpensive and stable catalysts, and the reaction must proceed under mild conditions. Therefore, developing such catalysts for the selective oxidation of alcohols to produce acids has become a particularly challenging process in green chemistry.

[0004] Traditionally, alcohol oxidation reactions in organic chemistry use strong oxidants such as permanganates and chromates. These strong oxidants can produce numerous side reactions and significant amounts of waste, waste gas, and wastewater, leading to environmental pollution. In recent years, numerous researchers have used precious metal catalysts to accelerate this process, addressing the pollution issues inherent in traditional reactions. However, the high cost and low abundance of precious metals have severely limited the commercial application of these catalysts.

[0005] The key to the electrocatalytic oxidation of methanol to formic acid is the degree of methanol oxidation. However, most methanol oxidation reaction (MOR) electrocatalysts completely oxidize methanol to carbon dioxide, resulting in significant carbon emissions. Currently, a variety of electrocatalysts have been developed, such as precious metal-based electrocatalysts platinum (Pt), palladium (Pd), and ruthenium (Ru). However, these catalysts do not provide selective conversion of methanol to formate. Furthermore, as mentioned above, precious metal-based catalysts are scarce and expensive, making them inadequate for powering the methanol economy. Recently, some non-precious transition metal-based electrocatalysts, particularly nickel (Ni)-based and cobalt (Co)-based catalysts, have been extensively studied for the selective conversion of methanol to formate. However, the current available transition metal-based catalysts for efficient electrocatalytic oxidation of methanol to formic acid remain limited in variety and abundance. Therefore, the development of novel electrocatalysts with excellent catalytic activity and stability is urgently needed.

[0006] The main disadvantages of precious metal materials are high catalyst cost, poor selectivity of formic acid product, high cost of electrosynthesis of formic acid, and cumbersome catalyst preparation. The development of transition metal-based electrocatalysts can effectively reduce catalyst costs and has made initial progress, but their catalytic activity is still lower than that of precious metal-based materials, and most electrocatalysts have high starting potentials (>1.4V), resulting in low operating current density (<50mA cm -2 ), and a high working potential (>1.6 V compared to the reversible hydrogen electrode). In addition, the relatively low current density limits their practical application in the electrosynthesis of formic acid: the current density of electrosynthesis of formic acid is usually required to be no less than 100 mA cm -2 , only then can practical application be possible. Summary of the Invention

[0007] To address the high onset potential issues of the prior art, the present invention provides a low-cost, scalable electrocatalyst for the selective electrocatalytic oxidation of alcohols using niobium pentoxide. This method is simple to operate, low in cost and energy consumption, and exhibits excellent catalytic activity, product selectivity, and stability in the electrochemical oxidation of methanol.

[0008] According to the present invention, the application of niobium pentoxide is used for the electrocatalytic selective oxidation of alcohols, specifically comprising loading a niobium pentoxide catalyst on a nickel foam substrate to provide a working electrode, dissolving an alcohol as a reaction substrate in a neutral or alkaline aqueous solution as an electrolyte, and selectively oxidizing the alcohol to generate an acid using the niobium pentoxide catalyst in a three-electrode electrolytic cell system. The surface of the niobium pentoxide catalyst has short Nb-O bonds as active sites.

[0009] Preferably, the niobium pentoxide catalyst is amorphous niobium pentoxide or high-dimensional niobium pentoxide.

[0010] Preferably, the loading amount of niobium pentoxide catalyst on nickel foam is 0.5-2 mg cm -2 More preferably, the loading amount of niobium pentoxide catalyst on nickel foam is 0.5-1 mg cm -2 .

[0011] Preferably, the voltage of the three-electrode electrolytic cell system is controlled between 1-4V.

[0012] Preferably, the niobium pentoxide catalyst is dispersed in Nafion solution and ethanol to obtain a dispersion, and the dispersion is supported on a nickel foam substrate and dried to provide a working electrode.

[0013] Preferably, the specific surface area of ​​the niobium pentoxide catalyst is 100-300m 2 g -1 .

[0014] Preferably, the aqueous solution is a KHCO 3 or KOH aqueous solution. More preferably, the aqueous solution is an alkaline KOH aqueous solution.

[0015] Preferably, niobium pentoxide catalyst is used to selectively oxidize methanol to produce formic acid.

[0016] Preferably, the operating current density for selective oxidation of alcohol to acid is 100-400 mA cm -2 .

[0017] Preferably, the onset potential for selective oxidation of alcohol to acid does not exceed 1.35 V vs. RHE (relative to reversible hydrogen electrode), and the working potential can be reduced to 1.47 V vs. RHE to achieve 100 mA cm -2 .

[0018] According to the application of niobium pentoxide of the present invention, the highly selective electrocatalytic oxidation of alcohol to acid by a transition metal-based catalyst (i.e., niobium pentoxide catalyst) has the advantages of low starting potential and high current density. In particular, the present invention clearly defines short Nb-O bonds as active sites. During the electrolysis process, for example, by controlling the voltage between 1-4V, more Nb-O bonds can be derived from the surface of niobium pentoxide. In the selective electrocatalytic oxidation reaction of alcohols, it is beneficial to selectively oxidize alcohols (e.g., methanol) to high-value-added acids (e.g., formic acid), with excellent conversion rate and selectivity, greatly reducing the production cost and electrolysis energy consumption of electrocatalytic acid production. Moreover, the niobium pentoxide catalyst of the present invention has a high specific surface area and an amorphous or high-dimensional spatial structure, which can significantly improve the electrocatalytic activity and stability. Its preparation method is simple, low-cost, and easy to control. In addition, the present invention provides basic application research for niobium pentoxide catalysts in the field of electrocatalysis, with broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 (a) Transmission electron microscopy and (b) selected area electron diffraction patterns of amorphous niobium pentoxide.

[0020] Figure 2 The linear scanning curve of amorphous niobium pentoxide 1 / NF catalyst at 1.2-1.8V (relative to reversible hydrogen electrode) (a represents the catalyst at 1 mol L -1 Linear scanning curve in potassium hydroxide + methanol, b represents the catalyst at 1 mol L -1 Linear scan curve in potassium hydroxide).

[0021] Figure 3This is the chronopotentiometry (CP) curve test of amorphous niobium pentoxide 1 / NF catalyst and its Faraday efficiency at different times (Figure a: stability of the catalyst within a certain voltage and current density range; Figure b: Faraday efficiency of the catalyst within 30,000s).

[0022] Figure 4 This is the Raman spectrum of the amorphous niobium pentoxide 1 / NF catalyst during the methanol electrocatalytic oxidation reaction at different applied voltages (potassium hydroxide + methanol).

[0023] Figure 5 (a) X-ray diffraction and (bc) transmission electron microscopy images of amorphous niobium pentoxide 1 / NF catalyst before and after methanol electrocatalytic oxidation reaction.

[0024] Figure 6 (a) Raman spectra and (b) Faraday efficiency diagram (potassium bicarbonate + methanol) of amorphous niobium pentoxide 1 / NF catalyst in the electrocatalytic oxidation of methanol at different applied voltages.

[0025] Figure 7 It is the Raman spectrum (potassium hydroxide + methanol) of monoclinic niobium pentoxide / NF catalyst in the methanol electrocatalytic oxidation reaction at different applied voltages.

[0026] Figure 8 This is a high-angle annular dark-field scanning transmission electron microscopy image of niobium pentoxide in high-dimensional space.

[0027] Figure 9 (a) Raman spectra and (b) linear scan curves (potassium hydroxide + methanol) of the high-dimensional niobium pentoxide / NF catalyst in the methanol electrocatalytic oxidation reaction at different applied voltages.

[0028] Figure 10 It is the Raman spectrum (potassium hydroxide + methanol) of the orthorhombic niobium pentoxide / NF catalyst in the methanol electrocatalytic oxidation reaction at different applied voltages. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0030] The present invention provides a niobium pentoxide catalyst (amorphous Nb2O5, designated Nb2O5-A). In a preferred embodiment, Nb2O5-A is obtained by calcining JRC-NbO-1 (provided by the Japan Society of Catalysis) at 400°C for 2 hours. In another preferred embodiment, Nb2O5-A is prepared in the laboratory by dissolving niobium pentachloride in distilled water to obtain solution A, magnetically stirring solution A for 3 hours to obtain a white precipitate, filtering and washing the white precipitate multiple times, and then drying the precipitate at 80°C for 12 hours to obtain niobic acid. The obtained niobic acid is then calcined in a tube furnace (400°C for 2 hours).

[0031] The present invention also includes preparing a niobium pentoxide electrode. Niobium pentoxide powder and Nafion solution (a perfluorosulfonic acid polymer solution) are dispersed in ethanol and deionized water. The mixture is ultrasonically treated for 30 minutes, and the dispersion is then coated on a nickel foam substrate and air-dried overnight.

[0032] The present invention also includes using a single-cell electrolytic cell for the electrolytic reaction. A niobium pentoxide catalyst-loaded nickel foam electrode serves as the working electrode, an alcohol substrate is dissolved in a neutral or alkaline aqueous solution as the electrolyte, a platinum sheet electrode serves as the counter electrode, and an Ag / AgCl electrode serves as the reference electrode. The electrocatalytic selective oxidation reaction is carried out at room temperature (25-30°C) to produce high-value-added formic acid.

[0033] The present invention also includes performing Raman measurements. In situ Raman spectroscopy was performed on a Horiba LABRAM HR Raman spectrometer. In situ experiments were performed using an electrochemical cell with bare nickel foam as the counter electrode and Ag / AgCl as the reference electrode. The excitation wavelength was 532 nm, and a 50x microscope objective with a numerical aperture of 0.55 was used. Spectra were collected for 60 seconds at each applied potential for the pretreated electrode.

[0034] Example 1 Amorphous Niobium Pentoxide 0.5 / NF

[0035] The purchased JRC-NbO-1 (provided by the Japan Catalysis Society) was calcined at 400 °C for 2 hours to obtain a white powder. The test showed that the powder had a high specific surface area (116 m 2 g -1 ), and through transmission electron microscopy and selected electron diffraction patterns, it was found that it has no lattice structure and presents an amorphous structure ( Figure 1 ), thus obtaining amorphous niobium pentoxide.

[0036] The nickel foam (1 cm×1 cm) was ultrasonically washed in acetone, hydrochloric acid solution, anhydrous ethanol and deionized water in sequence for 5-30 min to remove surface impurities, and then dried to obtain pretreated nickel foam for use.

[0037] 10 mg of amorphous niobium pentoxide powder was weighed and dispersed in 40 μL of Nafion solution (a perfluorosulfonic acid-based polymer solution) and 960 μL of ethanol. The mixture was sonicated for 30 minutes, and then 50 μL of the dispersion was applied to a nickel foam substrate (1 cm × 1 cm) and air-dried overnight. The amorphous niobium pentoxide loading on the nickel foam was 0.5 mg cm -2 , thus obtaining amorphous niobium pentoxide 0.5 / NF catalyst.

[0038] The voltage and current were controlled by a constant current meter. The H-type electrolyzer was used for electrocatalytic oxidation of methanol to formic acid. The cathode and anode chambers were both 15 mL in volume and separated by a Nafion 117 cation exchange membrane. 10 mL of 1 mol L -1 KOH aqueous solution is used as the electrolytic solution in the anode chamber and cathode chamber; in the anode chamber of the electrolytic cell, amorphous niobium pentoxide is added 0.5 / NF catalyst was cut into 2cm×2cm size as working electrode; in the cathode chamber of the electrolytic cell, a platinum electrode was used as the counter electrode; S1: methanol was used as reactant, 0.4mL of methanol was added to the electrolytic solution in the anode chamber and fully dissolved; S2: the electrolytic cell was placed in a constant temperature water bath to maintain the reaction system temperature at 60℃, and stirred in the anode chamber containing methanol. 0.5 / NF catalysts are also effective for methanol oxidation in other systems.

[0039] Example 2 Amorphous Niobium Pentoxide 1 / NF

[0040] Purchased JRC-NbO-1 (provided by the Japan Society of Catalysis) was calcined at 400° C. for 2 hours to obtain a white powder.

[0041] The nickel foam (1 cm×1 cm) was ultrasonically washed in acetone, hydrochloric acid solution, anhydrous ethanol and deionized water in sequence for 5-30 min to remove surface impurities, and then dried to obtain pretreated nickel foam for use.

[0042] 10 mg of amorphous niobium pentoxide powder was weighed and dispersed in 40 μL of Nafion solution (a perfluorosulfonic acid-based polymer solution) and 960 μL of ethanol. The mixture was sonicated for 30 minutes, and then 100 μL of the dispersion was applied to a nickel foam substrate (1 cm × 1 cm) and air-dried overnight. The amorphous niobium pentoxide loading on the nickel foam was 1 mg cm -2 , thereby obtaining an amorphous niobium pentoxide 1 / NF catalyst.

[0043] The performance of the amorphous niobium pentoxide 1 / NF catalyst was tested. The linear sweep value (LSV) curve was used to determine the performance of the amorphous niobium pentoxide catalyst for the selective electrocatalytic oxidation of methanol to formic acid. The specific test method is as follows:

[0044] Using Shanghai Chenhua's CHI660E electrochemical workstation, in a three-electrode electrolytic cell system, the amorphous niobium pentoxide 1 / NF catalyst was used as a working electrode (the electrode size was 1 cm×1 cm), a platinum sheet was used as a counter electrode, and an Ag / AgCl electrode was used as a reference electrode.

[0045] When 50 mL of 1 mol / L KOH aqueous solution was used as the electrolyte, oxygen evolution reaction (OER) test was carried out with a linear sweep voltammetry scan rate of 5 mV s -1 , the LSV curve of oxygen evolution reaction (OER) is as follows Figure 2 shown.

[0046] When the electrolyte is 50 mL of 1 mol L methanol -1 Electrocatalytic methanol oxidation reaction (MOR) test was carried out in KOH aqueous solution, and the scan rate of linear sweep voltammetry was 5 mV s -1 , the LSV curve of the electrocatalytic methanol oxidation reaction (MOR) is as follows Figure 2 shown.

[0047] Figure 2 This is a comparison of the LSV curves of the amorphous niobium pentoxide 1 / NF catalyst in the oxygen evolution reaction test and the electrocatalytic methanol selective oxidation reaction test. Figure 2 The LSV curve comparison shows that the b curve is not - 1 The LSV curves measured when methanol was added to the KOH aqueous solution electrolyte, curve a is at 1 mol L -1LSV curves measured when methanol is added to the KOH aqueous electrolyte. By comparing curves a and b, we can see that when methanol is added, a strong oxidation peak appears on the LSV curve, and it has a very low onset potential (1.35V vs. RHE), and can reach an industrial-grade current density of 100mA cm at a low potential of 1.47V. -2 Therefore, it can be judged that amorphous niobium pentoxide / NF catalyst has excellent effect on methanol oxidation reaction. In the traditional water electrolysis process, the anodic oxidation reaction can only reach 100mAcm at 1.75V. -2 The current density of 100 mA cm can be achieved by replacing the slow anodic oxidation reaction and reducing the working potential of the anode methanol-formic acid to 1.47 V vs. RHE. -2 , such methanol oxidation reaction also reduces the energy consumption of H2 generation in water electrolysis.

[0048] The electrolyte is 50 mL of 1 mol L methanol. -1 In the case of KOH aqueous solution, the amorphous niobium pentoxide 1 / NF catalyst was cut into 1 cm×1 cm size as the working electrode.

[0049] A platinum electrode was used as the counter electrode and Ag / AgCl was used as the reference electrode. The current was controlled to 100 mA, the voltage was controlled in the range of 1-4 V, and the electrolysis reaction lasted for 30,000 seconds. The solution in the electrolytic cell was sampled every 7,500 seconds (sampling volume 500 μL), and 100 μL of heavy water was added to the 500 μL sample solution for nuclear magnetic resonance analysis. A graph showing the change in formic acid product content with reaction time was obtained. The reaction results are shown in FIG. Figure 3 shown. Figure 3 (a) is the chronopotentiometry (CP) curve of methanol oxidation at different current densities. It can be seen that with the increase of reaction time and the voltage measurement at different currents, the amorphous niobium pentoxide 1 / NF catalyst has high stability. Figure 3 (b) is the Faraday efficiency diagram, which shows that the industrial-grade current density of 100-200 mA cm is achieved. -2 When the Faradaic efficiency of formic acid is calculated to be 100%, even at 300-400 mA cm -2 When the reaction temperature is 5000 nm, the Faradaic efficiency of formic acid can still reach 80%, and the amorphous niobium pentoxide 1 / NF catalyst has very good selectivity.

[0050] In situ Raman experiments were performed using a custom electrochemical cell with bare nickel foam as the counter electrode and Ag / AgCl as the reference electrode. The excitation wavelength was 532 nm, and a 50x microscope objective with a numerical aperture of 0.55 was used. Spectra were collected for 60 seconds at each applied potential for the pretreated electrode.

[0051] The Raman spectra at different applied voltages were measured by online Raman spectroscopy. Figure 4 As shown in the results, it is demonstrated that the short Nb-O bonds derived in situ on the amorphous Nb2O51 / NF catalyst are active sites for the selective oxidation of methanol to formic acid. Figure 5 XRD and TEM tests before and after the methanol oxidation reaction also proved that a new lattice was formed on the surface of the amorphous niobium pentoxide after the reaction, and also proved that the short Nb-O bonds generated in situ on the surface were active sites.

[0052] The Raman spectra at different applied voltages were measured by online Raman spectroscopy. Figure 6 As shown, Figure 6 (a) is the Raman spectra of amorphous niobium pentoxide 1 / NF catalyst at different potentials in neutral potassium bicarbonate electrolyte. Figure 6 (b) is a graph of the Faradaic efficiency of the amorphous niobium pentoxide 1 / NF catalyst at different potentials in a neutral potassium bicarbonate electrolyte. It can be seen that as the voltage increases, the short Nb-O bonds on the surface gradually disappear, reaching a significant peak at 1.9 V, while the Faradaic efficiency plummets to 20%. This further demonstrates that the short Nb-O bonds in situ derived on the surface of the amorphous niobium pentoxide 1 / NF catalyst are active sites for the selective oxidation of methanol to formic acid.

[0053] Example 3 Monoclinic niobium pentoxide / NF

[0054] The purchased JRC-NbO-2 (provided by the Japan Catalysis Society) was calcined at 400 ° C for 2 hours to obtain a white powder. The test showed that the specific surface area of ​​the powder was 4m 2 g -1 , and it has a monoclinic morphological structure, thus obtaining monoclinic niobium pentoxide (denoted as Nb2O5-M).

[0055] The nickel foam (1 cm×1 cm) was ultrasonically washed in acetone, hydrochloric acid solution, anhydrous ethanol and deionized water in sequence for 5-30 min to remove surface impurities, and then dried to obtain pretreated nickel foam for use.

[0056] 10 mg of monoclinic niobium pentoxide powder was weighed and dispersed in 40 μL of Nafion solution (a perfluorosulfonic acid polymer solution), 960 μL of ethanol, and 40 μL of deionized water. The mixture was sonicated for 30 minutes, and then 100 μL of the dispersion was applied to a nickel foam substrate (1 cm × 1 cm) and air-dried overnight. The loading of monoclinic niobium pentoxide on the nickel foam was 1 mg / cm 2 , thereby obtaining a monoclinic niobium pentoxide / NF catalyst.

[0057] The electrolyte is 50 mL of 1 mol L methanol. -1 When KOH aqueous solution was used, the monoclinic niobium pentoxide / NF catalyst was cut into 1cm×1cm size as the working electrode. In the in situ Raman experiment, bare nickel foam was used as the counter electrode, Ag / AgCl was used as the reference electrode, and a customized electrochemical cell was used for the in situ experiment. The excitation wavelength was 532nm, and a 50x microscope objective with a numerical aperture of 0.55 was used. The spectrum of the pretreated electrode at each applied potential was collected for 60 seconds. The Raman spectra at different applied voltages were measured by online Raman spectroscopy. Figure 7 As shown, the results are different from those of Example 2, so the monoclinic niobium pentoxide / NF catalyst does not have excellent performance in the electrocatalytic oxidation of methanol.

[0058] A monoclinic niobium pentoxide-loaded nickel foam electrode served as the working electrode, alcohols as the reaction substrate dissolved in an alkaline aqueous solution served as the electrolyte, a platinum electrode served as the counter electrode, and an Ag / AgCl reference electrode. Electrocatalytic selective oxidation reactions were carried out at room temperature (25-30°C) to produce high-value-added formic acid. Raman spectroscopy confirmed that the monoclinic niobium pentoxide surface lacked short Nb-O bonds. Nb2O5-M, with its monoclinic crystal form, exhibited poor electrocatalytic performance, and no short Nb-O bonds were observed on its surface during the methanol electrocatalytic reaction.

[0059] Example 4 High-dimensional space crystal form niobium pentoxide / NF

[0060] Using ammonium niobium oxalate as the raw material, it was placed in a hydrothermal reactor with deionized water. The hydrothermal reactor was placed in an oven and subjected to a hydrothermal reaction at 175°C for 24 hours. The resulting solution was then filtered, thoroughly washed with deionized water, and dried at 80°C overnight to obtain a dry solid. By calcining the dry solid in air at 400°C for 2 hours, a high-dimensional crystalline niobium pentoxide (denoted as HD-Nb2O5) was obtained. The high-angle annular dark field scanning transmission electron microscope image is shown below. Figure 8 The high-dimensional space crystalline niobium pentoxide was loaded on nickel foam by the same steps as in Example 3 to obtain a high-dimensional space crystalline niobium pentoxide / NF catalyst.

[0061] The electrolyte is 50 mL of 1 mol L methanol. -1When KOH aqueous solution was used, the high-dimensional crystalline niobium pentoxide / NF catalyst was cut into 1cm×1cm size as the working electrode. In the in-situ Raman experiment, bare nickel foam was used as the counter electrode, Ag / AgCl was used as the reference electrode, and a customized electrochemical cell was used for the in-situ experiment. The excitation wavelength was 532nm, and a 50x microscope objective lens with a numerical aperture of 0.55 was used. The spectrum of the pretreated electrode at each applied potential was collected for 60 seconds. The Raman spectra at different applied voltages were measured by online Raman spectroscopy. Figure 9 As shown in (a), the results are the same as those in Example 2. Short Nb-O bonds are also derived on the surface of the high-dimensional crystalline niobium pentoxide / NF catalyst. Figure 9 (b) also shows that the high-dimensional crystalline niobium pentoxide / NF catalyst has a good effect on the selective oxidation of methanol to formic acid. Therefore, the high-dimensional crystalline niobium pentoxide / NF catalyst has excellent performance in the electrocatalytic oxidation of methanol to formic acid.

[0062] A high-dimensional crystalline niobium pentoxide loaded with nickel foam served as the working electrode, with alcohols as the reaction substrate dissolved in an alkaline aqueous solution as the electrolyte, a platinum electrode as the counter electrode, and an Ag / AgCl reference electrode. Electrocatalytic selective oxidation reactions were conducted at room temperature (25-30°C) to produce high-value-added formic acid. Raman spectroscopy confirmed the presence of short Nb-O bonds on the surface of the high-dimensional niobium pentoxide. The HD-Nb2O5 crystal structure exhibits a high-dimensional structure, and short Nb-O bonds were observed on its surface during the methanol electrocatalytic reaction.

[0063] Example 5 Orthorhombic Niobium Pentoxide / NF

[0064] Ammonium niobium oxalate was used as the raw material and charged into a hydrothermal reactor with deionized water. The reactor was placed in an oven and subjected to a hydrothermal reaction at 175°C for 24 hours. The resulting solution was then filtered, thoroughly rinsed with deionized water, and dried overnight at 80°C to obtain a dry solid. The dry solid was calcined in air at 650°C for 2 hours to obtain orthorhombic niobium pentoxide (denoted as T-Nb2O5). This orthorhombic niobium pentoxide was then supported on nickel foam using the same procedures as in Example 3 to obtain an orthorhombic niobium pentoxide / NF catalyst.

[0065] The electrolyte is 50 mL of 1 mol L methanol. -1When the KOH aqueous solution was used, the orthorhombic niobium pentoxide / NF catalyst was cut into 1cm×1cm size as the working electrode. In the in-situ Raman experiment, bare nickel foam was used as the counter electrode, Ag / AgCl was used as the reference electrode, and a customized electrochemical cell was used for the in-situ experiment. The excitation wavelength was 532nm, and a 50x microscope objective lens with a numerical aperture of 0.55 was used. The spectrum of the pretreated electrode at each applied potential was collected for 60 seconds. The Raman spectra at different applied voltages were measured by online Raman spectroscopy. Figure 10 As shown, the results are different from those of Example 2, and thus the orthorhombic niobium pentoxide / NF catalyst does not have excellent performance in the electrocatalytic oxidation of methanol.

[0066] An orthorhombic niobium pentoxide-loaded nickel foam electrode served as the working electrode, an alcohol substrate dissolved in an alkaline aqueous solution served as the electrolyte, a platinum electrode served as the counter electrode, and an Ag / AgCl reference electrode was used. Electrocatalytic selective oxidation reactions were carried out at room temperature (25-30°C) to produce high-value-added formic acid. T-Nb2O5 has an orthorhombic crystal form and poor electrocatalytic performance. Short Nb-O bonds were not observed on its surface during the methanol electrocatalytic reaction. This differs from the characteristics and properties of the amorphous niobium pentoxide of this research invention and, therefore, does not possess the same catalytic performance as the present invention.

[0067] The table below compares the electrocatalytic performance of different catalysts.

[0068] Table 1

[0069]

[0070] [1]MIAbdullah,A.Hameed,N.Zhang,MHIslam,M.Ma,BGPollet,ACSAppl.Mater.Interfaces 2021,13,30603.

[0071] [2] K. Xiang, D. Wu, X. Deng, M. Li, S. Chen, P. Hao, X. Guo, J. L. Luo, X. Z. Fu, Adv. Funct. Mater. 2020, 30, 1909610.

[0072] [3] Zeng, Y.; Chen, L.; Chen, R.; Wang, Y.; Xie, C.; Tao, L.; Huang, L.;

[0073] [4]Y.Ding,Q.Xue,QLHong,FMLi,YCJiang,SNLi,Y.Chen,ACS ACSAppl.Mater.Interfaces 2021,13,4026.

[0074] [5]M.Li,X.Deng,Y.Liang,K.Xiang,D.Wu,B.Zhao,H.Yang,J.-L.Luo,X.-Z.Fu,J.Energy Chem.2020,50,314.

[0075] [6]M.Li,X.Deng,K.Xiang,Y.Liang,B.Zhao,J.Hao,JLLuo,XZFu,ChemSusChem 2020,13,914.

[0076] The niobium pentoxide catalyst of the present invention is in the form of a white powder, has a simple preparation method, and is easily commercially applicable. The catalyst of the present invention can be used for the selective electrocatalytic production of high-value-added formic acid at the anode for methanol. The amorphous niobium pentoxide catalyst of the present invention has excellent electrocatalytic performance for the selective oxidation of methanol (1.47 V vs. RHE, 100 mA cm -2 ) and formic acid selectivity (100-200 mA cm -2 , FE = 100%). In situ Raman analysis demonstrates that the surface-derived short Nb-O bonds of the niobium pentoxide of the present invention serve as active sites for the selective electrocatalytic oxidation of methanol to high-value-added formic acid. The niobium pentoxide of the present invention can also be applied to other systems, such as water electrolysis processes.

[0077] The niobium pentoxide catalyst of the present invention has a simple synthesis method, a short reaction cycle, and high reproducibility, and can be widely used in industry in the future. Compared with precious metal catalysts, the catalyst of the present invention is low in cost and relatively abundant in content, and can be used for the selective electrocatalytic oxidation of methanol to formic acid. The catalyst of the present invention has excellent electrocatalytic performance for the selective electrocatalytic oxidation of methanol: a low starting potential (1.35V vs. RHE) and a high electrocatalytic efficiency of 100mA cm at a low operating potential (1.47V vs. RHE). -2 The catalyst of this invention requires 100-200mA cm in actual production. -2 The Faradaic efficiency of formic acid was maintained at 100% at a current density of 300–400 mA cm -2 The Faradaic efficiency of formic acid is still maintained at 80% at a current density of 1.5 %.

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Various modifications are possible. In other words, any simple, equivalent changes and modifications made in accordance with the claims and description of the present invention are within the scope of protection of the patent claims. Anything not fully described in this invention constitutes conventional technology.

Claims

1. An application of niobium pentoxide, characterized in that: The niobium pentoxide is used for the electrocatalytic selective oxidation of alcohol, specifically comprising: loading a niobium pentoxide catalyst on a nickel foam substrate to provide a working electrode; dissolving an alcohol as a reaction substrate in a neutral or alkaline aqueous solution as an electrolyte; and selectively oxidizing methanol to formic acid using the niobium pentoxide catalyst in a three-electrode electrolytic cell system. The niobium pentoxide catalyst is amorphous niobium pentoxide or high-dimensional niobium pentoxide, and has short Nb-O bonds on its surface as active sites.

2. The use according to claim 1, characterized in that The loading amount of niobium pentoxide catalyst on nickel foam is 0.5-2 mg·cm -2 .

3. The use according to claim 1, characterized in that The voltage of the three-electrode electrolytic cell system was controlled between 1 and 4 V.

4. The use according to claim 1, characterized in that A niobium pentoxide catalyst was dispersed in a Nafion solution and ethanol to obtain a dispersion, and the dispersion was supported on a nickel foam substrate and dried to provide a working electrode.

5. The use according to claim 1, characterized in that The specific surface area of ​​niobium pentoxide catalyst is 100-300m 2 ·g -1 .

6. The use according to claim 1, characterized in that The aqueous solution is KHCO3 or KOH aqueous solution.

7. The use according to claim 1, characterized in that The operating current density for selective oxidation of alcohols to acids is 100-400 mA·cm -2 .

8. The use according to claim 1, characterized in that The onset potential of selective oxidation of alcohol to acid does not exceed 1.35 V vs. RHE, the working potential is reduced to 1.47 V vs. RHE can reach 100 mA·cm -2 .

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