A vacancy heteropoly acid and its preparation method and application in electrolysis coupled hydrogen production

Abstract

The present invention discloses a vacancy heteropoly acid and a preparation method thereof and an application in electrolytic coupled hydrogen production, belonging to the field of catalyst technology. The preparation method is: using phosphomolybdic acid as a raw material, preparing the vacancy heteropoly acid by adjusting the pH to 2-6 or adding a high concentration acid for acidification and heating; the high concentration acid is a mixed acid of 0.1-6 M phosphoric acid, or 0.1-3 M phosphoric acid and 0.1-6 M sulfuric acid or 0.1-1 M perchloric acid. The rate of oxidation of biomass and organic wastewater by the vacancy phosphomolybdic heteropoly acid prepared by the present invention is 10-20 times that of the complete Keggin type phosphomolybdic acid. The present invention also provides a coupling process for organic wastewater degradation and electrolytic hydrogen production, which can regenerate and recycle the vacancy heteropoly acid and can couple hydrogen production.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and more specifically, relates to a vacancy heteropoly acid and a preparation method thereof and application thereof in electrolytic coupled hydrogen production. Background Art

[0002] Polyoxometalates are water-soluble molecular metal oxide clusters with well-defined crystal structures and tunable redox properties. 3 PMo 12 O 40 , PMo 12 ) is a typical Keggin-type polyoxometalate, PMo 12 It is soluble in a variety of polar solvents and has super acidity, even stronger than HCl and H 2 SO 4 and HNO 3 The acidity of PMo 12 It has excellent activity in acid-catalyzed reactions and is a highly efficient oxidant and catalyst that can be used in the oxidation of organic matter and the degradation of biomass.

[0003] Lacunar phosphomolybdic acid refers to PMo 12 The molybdenum oxygen octahedron in the Keggin type PMo 12 By removing up to 6 octahedrons from the structure, this vacant polyacid has more active sites and can bind to the substrate faster, thereby accelerating the reaction rate.

[0004] At present, the preparation method of vacant heteropolyacids is mainly to form vacant heteropolyacids by coordination with cations or cationic ligands (quaternary ammonium cations, imidazole cations, pyridinium cations). The operation method is relatively cumbersome and difficult to industrialize. The literature "Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy153, 152-159 (2016), Journal of the Iranian Chemical Society 12, 137-145(2014), Chemical Science 12, 1240-1244 (2021)" reported that PMo was prepared by adjusting the pH of sodium hydroxide solution. 12 Degraded to vacancy phosphomolybdic acid, 12During the alkalization process, the molybdenum oxygen octahedron is separated from the Keggin structure, and different vacant phosphomolybdic heteropoly acids can be obtained under different pH conditions. However, during the alkalization process, the acidity of the vacant phosphomolybdic heteropoly acid solution decreases, and the solution obtained by this method has weak acidity, and it has poor reactivity for acid-catalyzed reactions as an oxidant and catalyst, which is not conducive to improving the rate of acid-catalyzed reactions and limits the application of vacant phosphomolybdic heteropoly acids in acid-catalyzed reactions. In addition, during the pH increase process, with the formation of vacant phosphomolybdic heteropoly acids, many free molybdenum oxygen octahedrons appear in the solution. The oxidizability and reactivity of this part of the molybdenum oxygen compound are weaker than those of the vacant phosphomolybdic heteropoly acids, resulting in a decrease in the utilization rate of active Mo species. Summary of the invention

[0005] The present invention aims at the defects of the prior art that the preparation method of the vacant heteropoly acid is complicated and the activity of the vacant heteropoly acid is reduced, and proposes a vacant heteropoly acid and its preparation method and application in electrolytic coupled hydrogen production. The vacant heteropoly acid is prepared by adjusting pH or acidification and heating, the preparation method is simple, and the prepared vacant heteropoly acid has high activity.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] A method for preparing a lacunarity heteropoly acid, which uses phosphomolybdic acid as a raw material, and prepares the lacunarity heteropoly acid by adjusting the pH to 2-6 or adding a high-concentration acid for acidification and heating; the high-concentration acid is 0.1-6 M phosphoric acid, or a mixed acid of 0.1-3 M phosphoric acid and 0.1-6 M sulfuric acid or 0.1-1 M perchloric acid.

[0008] In the present application, saturated Keggin-type phosphomolybdic acid is used as a raw material and heated under the action of a high concentration of acid to obtain a vacancy heteropoly acid.

[0009] Preferably, the usage ratio of the phosphoric acid to the sulfuric acid or perchloric acid is 1:4 to 6:1.

[0010] Preferably, the heating temperature is 80-120° C. and the heating time is 0.5-2 h.

[0011] Preferably, the phosphomolybdic acid is H 3 PMo 12 O 40 or PMo 12 .

[0012] Preferably, the preparation method of phosphomolybdic acid is: using molybdenum trioxide and phosphoric acid as raw materials, heating and reflux at a temperature of 100-150°C for a time of 2-10 h.

[0013] Preferably, the pH is adjusted by adding any one or more of sodium hydroxide, lithium hydroxide or disodium hydrogen phosphate.

[0014] A lacunay heteropoly acid prepared by the above-mentioned preparation method of lacunay heteropoly acid.

[0015] A use of the above-mentioned occlusive heteropoly acid as an oxidant and / or catalyst and / or adsorbent in the degradation of organic wastewater.

[0016] A coupled process for organic wastewater degradation and electrolytic hydrogen production uses the above-mentioned vacant heteropoly acid as a catalyst and / or oxidant for organic wastewater degradation. The reduced vacant heteropoly acid after the reaction enters the anode pool for oxidation, while hydrogen is produced at the cathode.

[0017] Preferably, the organic wastewater is organic wastewater containing biological sugars.

[0018] An organic wastewater degradation and electrolytic hydrogen production coupling device is used for the above-mentioned electrolytic hydrogen production coupling process, which comprises: an organic wastewater treatment device and an electrolytic hydrogen production device.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention prepares a vacancy heteropoly acid by acidification or pH adjustment, and the preparation method is simple and efficient. The prepared vacancy heteropoly acid exposes more metal Mo atoms as active sites, and it has better reactivity for catalytic reaction as an oxidant and catalyst. It can accelerate the adsorption and activation of organic molecules, capture electrons faster from biomass, and greatly improve the reaction rate. The vacancy phosphomolybdic heteropoly acid obtained by adjusting the ratio of P and Mo by phosphoric acid oxidizes biomass and organic wastewater at a rate 10-20 times that of a complete Keggin type phosphomolybdic acid. The vacancy phosphomolybdic heteropoly acid greatly expands the pH range of the reaction system, expanding the original pH of about 2-4 to a hydrogen ion concentration of 6 mol / L or even to pH = 7, and rapid biomass oxidation reaction can occur.

[0021] The present invention also provides a coupled process and device for organic wastewater degradation and electrolytic hydrogen production, wherein the organic matter, biosaccharide, etc. in the wastewater are oxidized or degraded by the vacant heteropoly acid, and the vacant heteropoly acid after the reaction is introduced into the anode tank of the electrolytic hydrogen production device for oxidation, so that the vacant heteropoly acid can be recycled, and hydrogen is produced at the cathode at the same time, thereby achieving the coupling of biosaccharide or organic wastewater degradation and electrochemical hydrogen production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A process route diagram of a method for preparing a lacuna heteropolyacid in the present invention.

[0023] Figure 2 It is a schematic diagram of a coupling device for organic wastewater degradation and electrolysis hydrogen production in the present invention.

[0024] Figure 3 PMo in the present invention12 The characterization results;

[0025] Among them, (a) PMo 12 NMR P spectrum; (b) PMo 12 Glucose constant current electrolysis curve.

[0026] Figure 4 is the characterization result of PMo-1 in the present invention;

[0027] Among them, (a) NMR P spectrum of PMo-1; (b) constant current electrolysis curve of glucose of PMo-1.

[0028] Figure 5 It is the characterization result of PMo-2 in the present invention;

[0029] Among them, (a) NMR P spectrum of PMo-2; (b) constant current electrolysis curve of glucose of PMo-2.

[0030] Figure 6 It is the characterization result of PMo-3 in the present invention;

[0031] Among them, (a) NMR P spectrum of PMo-3; (b) constant current electrolysis curve of glucose of PMo-3.

[0032] Figure 7 It is the characterization result of PMo-4 in the present invention;

[0033] Among them, (a) NMR P spectrum of PMo-4; (b) constant current electrolysis curve of glucose of PMo-4.

[0034] Figure 8 It is the characterization result of PMo-5 in the present invention;

[0035] Among them, (a) NMR P spectrum of PMo-5; (b) constant current electrolysis curve of glucose of PMo-5.

[0036] Fig. 9 It is the characterization result of PMo-6 in the present invention;

[0037] Among them, (a) NMR P spectrum of PMo-6; (b) constant current electrolysis curve of glucose of PMo-6.

[0038] Fig.10 For PMo 12 and color change diagram and absorbance-time curve of organic wastewater oxidized by PMo-3;

[0039] Among them, (a) PMo 12and PMo-3 oxidation of organic wastewater (1 ppm); (b) absorbance-time curve of organic wastewater (1 ppm); (c) PMo 12 (d) Absorbance-time curve of organic wastewater (10 ppm); (e) PMo 12 (f) Absorbance-time curve of organic wastewater (20 ppm); (g) PMo 12 and color change diagram of organic wastewater (100 ppm) oxidized by PMo-3; (h) kinetic curve of organic wastewater (100 ppm) (obtained from absorbance conversion, the same below).

[0040] Fig.11 Polarization curve and constant current electrolysis curve of PMo-3-organic wastewater solution (100 ppm).

[0041] Fig.12 Polarization curve (left) and constant current electrolysis curve (right) of PMo-3-organic wastewater solution;

[0042] Among them, the organic wastewater concentration in (a) and (b) is 0.5 mol / L; the organic wastewater concentration in (c) and (d) is 1 mol / L; the organic wastewater concentration in (e) and (f) is 1.5 mol / L; the organic wastewater concentration in (g) and (h) is 3 mol / L.

[0043] Fig.13 is the characterization result of MoPA-2;

[0044] Among them, (a) NMR P spectrum of MoPA-2; (b) kinetic curve of MoPA-2-glucose (obtained by absorbance conversion); (c) polarization curve of MoPA-2-glucose; (d) constant current electrolysis curve of MoPA-2-glucose.

[0045] Fig.14 is the characterization result of MoPA-3;

[0046] Among them, (a) NMR P spectrum of MoPA-3; (b) kinetic curve of MoPA-3-glucose (obtained by absorbance conversion); (c) polarization curve of MoPA-3-glucose; (d) constant current electrolysis curve of MoPA-3-glucose.

[0047] Fig.15 is the characterization result of MoPA-4;

[0048] Among them, (a) NMR P spectrum of MoPA-4; (b) kinetic curve of MoPA-4-glucose (obtained by absorbance conversion); (c) polarization curve of MoPA-4-glucose; (d) constant current electrolysis curve of MoPA-4-glucose.

[0049] Fig.16 is the characterization result of MoPA-5;

[0050] Among them, (a) NMR P spectrum of MoPA-5; (b) kinetic curve of MoPA-5-glucose (obtained by absorbance conversion); (c) polarization curve of MoPA-5-glucose; (d) constant current electrolysis curve of MoPA-5-glucose.

[0051] Fig.17 is the characterization result of MoPA-6;

[0052] Among them, (a) NMR P spectrum of MoPA-6; (b) kinetic curve of MoPA-6-glucose (obtained by absorbance conversion); (c) polarization curve of MoPA-6-glucose; (d) constant current electrolysis curve of MoPA-6-glucose.

[0053] Fig.18 is the absorbance-time curve of MoPA-5-different biological sugars;

[0054] Among them, (a) fructose; (b) xylose; (c) arabinose; (d) mannose; (e) maltose; (f) sucrose.

[0055] Fig.19 is the electrolysis curve of PMo-3-glucose cycle experiment;

[0056] Among them, (a) polarization curve in the PMo-3-glucose cycling experiment; (b) constant current electrolysis curve in the PMo-3-glucose cycling experiment. DETAILED DESCRIPTION

[0057] Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited to the specific implementation disclosed below.

[0058] The present invention provides a method for preparing a vacancy heteropoly acid, such as Figure 1 As shown, phosphomolybdic acid is used as a raw material, phosphoric acid or phosphoric acid, sulfuric acid and perchloric acid are added and heated to prepare heteropoly acid.

[0059] In some specific embodiments, Figure 1As shown, the occlusive heteropoly acid can also be prepared by adjusting the pH to 2-6 by adding alkali.

[0060] The present invention also provides the vacant heteropoly acid prepared by the above preparation method.

[0061] Furthermore, the present invention also provides a coupled process for organic wastewater degradation and electrolytic hydrogen production, using the above-mentioned vacant heteropoly acid as a catalyst and / or oxidant for organic wastewater degradation, and the reduced vacant heteropoly acid after the reaction enters the anode tank for oxidation, while hydrogen is produced at the cathode.

[0062] An organic wastewater degradation and electrolytic hydrogen production coupling device is used for the above electrolytic hydrogen production coupling process, such as Figure 2 As shown, it includes: an organic wastewater treatment device and an electrolytic hydrogen production device.

[0063] The vacant heteropoly acid is used as a catalyst and / or oxidant to degrade or oxidize wastewater containing organic matter, thereby removing organic matter and forming a reduced vacant heteropoly acid after the reaction. The liquid after the reaction is transferred to the anode pool of the electrolytic cell, and the cathode is a phosphoric acid solution. The reduced vacant heteropoly acid is oxidized and regenerated in the anode pool and can be used as a catalyst and / or oxidant for the next stage of organic wastewater. The cathode is also used for electrolysis to produce hydrogen. Electrons can be released from the vacant phosphomolybdic heteropoly acid on the surface of a cheap graphite felt electrode, and the energy consumption is extremely low (1.92 kWh / Nm 3 H 2 ) to achieve cathode hydrogen evolution, and the Faraday efficiency of hydrogen production reaches over 97%.

[0064] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. It should be noted that the reagents used in the present embodiment are all common commercial products.

[0065] Example 1

[0066] Weigh 10.368 g MoO 3 The solid was added to 200 mL of water, heated at 80 °C and stirred evenly, then 0.69 g of phosphoric acid (85 wt%) was added dropwise to the solution, and the solution was heated to 140 °C and refluxed until MoO 3 The solution was completely dissolved to obtain a yellow solution. After the solution was cooled and filtered, no obvious solid remained. After that, the solution was evaporated at 80 °C until the solution volume was 20 mL, obtaining 0.3 mol / L PMo 12 Solution. Its NMR P spectrum is as follows Figure 3 As shown in (a), a complete Keggin-type phosphomolybdic acid is formed.

[0067] 1.8 g of glucose was added to the above solution and reacted at 100 °C for 2 h. 12 The degree of reduction of the solution was used to determine the oxidation effect of the substrate glucose. During the reaction, 10 μL of the reaction solution was taken at regular intervals, diluted with 3 mL of water, and its absorbance was measured at a wavelength of 700 nm using a visible spectrophotometer.

[0068] The PMo obtained after the reaction 12 The blue solution and 20 mL of H 3 PO 4 The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump. The polarization curves of the solution at different voltages and 50 mA / cm 2 Constant current electrolysis (electrode area 20 cm 2 ) curve. When the voltage suddenly increases, stop the experiment; Figure 3 As shown in (b), when the voltage reaches the theoretical potential of water electrolysis 1.23 V, the solution electrolysis time is only 57 s. The volume of hydrogen collected at the cathode by the drainage method is 7.11 mL, and the calculated hydrogen production Faraday efficiency is 98.23%.

[0069] Example 2

[0070] Weigh 10.368 g MoO 3 The solid was added to 200 mL of water, heated at 80 °C and stirred evenly, then 0.69 g of phosphoric acid (85 wt%) was added dropwise to the solution, and the solution was heated to 140 °C and refluxed until MoO 3 The solution was completely dissolved to obtain a yellow solution. After the solution was cooled, it was filtered and no obvious solid remained. After that, the solution was evaporated at 80 °C until the solution volume was 10 mL to obtain PMo 12 Solution. 12 2.3 g of phosphoric acid (85 wt%) was added to the solution, and the volume of the solution was fixed to 20 mL. The solution was heated at 100 °C and stirred continuously. After 2 h, the heating was stopped to obtain a vacancy heteropoly acid, named PMo-1 solution. Figure 4 (a) and Figure 3 (a) For comparison, PMo in PMo-1 12 The characteristic NMR signal peak (-3.6ppm) weakened, and new NMR signal peaks appeared at -2.8 ppm and -1 ppm, which were attributed to the vacant heteropoly acid.

[0071] 1.8 g of glucose was added to the above solution and reacted at 100 °C for 2 h. The oxidation effect of the substrate glucose was judged by the reduction degree of the PMo-1 solution. During the reaction, 10 μL of the reaction solution was taken at regular intervals, diluted with 3 mL of water, and its absorbance was measured at a wavelength of 700 nm using a visible spectrophotometer.

[0072] The PMo-1-glucose blue solution obtained after the reaction was mixed with 20 mL H 3 PO 4 The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump. The polarization curves of the solution at different voltages and 50 mA / cm 2 Constant current electrolysis (electrode area 20 cm 2 ) curve. When the voltage suddenly increases, stop the experiment; Figure 4 As shown in (b), when the voltage reaches the theoretical potential of water electrolysis of 1.23 V, the solution electrolysis time is 305 s. The prolonged solution electrolysis time indicates that the vacancy heteropoly acid obtains more electrons from the organic matter, that is, the organic matter is degraded more thoroughly, and the hydrogen production time is longer than that in Example 1. The volume of hydrogen collected at the cathode by the drainage method is 38.04 mL, and the calculated hydrogen production Faraday efficiency is 98.24%.

[0073] Example 3

[0074] Weigh 10.368 g MoO 3 The solid was added to 200 mL of water, heated at 80 °C and stirred evenly, then 0.69 g of phosphoric acid (85 wt%) was added dropwise to the solution, and the solution was heated to 140 °C and refluxed until MoO 3 The solution was completely dissolved to obtain a yellow solution. After the solution was cooled, it was filtered and no obvious solid remained. After that, the solution was evaporated at 80 °C until the solution volume was 10 mL to obtain PMo 12 Solution. 12 4.6 g of phosphoric acid (85 wt%) was added to the solution, and the volume of the solution was fixed to 20 mL. The solution was heated at 100 °C and stirred continuously. After 2 h, the heating was stopped to obtain a vacancy heteropoly acid, named PMo-2 solution. Figure 5 (a) It can be seen that PMo in PMo-2 12 The characteristic NMR signal peak (-3.6ppm) is weaker than that in Example 2, which indicates that more PMo 12 Decomposition occurred; however, the signal peaks of the absent heteropolyacid (-2.8ppm, -1 ppm) were not obvious. This was because the phosphoric acid concentration in the system was relatively high at this time, and the characteristic peak of phosphoric acid (0ppm) masked the signal peaks at (-1ppm, -2.8ppm).

[0075] 1.8 g of glucose was added to the above solution and reacted at 100 °C for 2 h. The oxidation effect of the substrate glucose was judged by the reduction degree of the PMo-2 solution. During the reaction, 10 μL of the reaction solution was taken at regular intervals, diluted with 3 mL of water, and its absorbance was measured at a wavelength of 700 nm using a visible spectrophotometer.

[0076] The PMo-2-glucose blue solution obtained after the reaction was mixed with 20 mL H 3 PO 4 The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump. The polarization curves of the solution at different voltages and 50 mA / cm 2 Constant current electrolysis (electrode area 20 cm 2 ) curve. When the voltage suddenly increases, stop the experiment; Figure 5 As shown in (b), when the voltage reaches the theoretical potential of water electrolysis 1.23 V, the solution electrolysis time is 463 s. The volume of hydrogen collected at the cathode by the drainage method is 57.98 mL, and the calculated hydrogen production Faraday efficiency is 98.64%.

[0077] Example 4

[0078] Weigh 10.368 g MoO 3 The solid was added to 200 mL of water, heated at 80 °C and stirred evenly, then 0.69 g of phosphoric acid (85 wt%) was added dropwise to the solution, and the solution was heated to 140 °C and refluxed until MoO 3 The solution was completely dissolved to obtain a yellow solution. After the solution was cooled, it was filtered and no obvious solid remained. After that, the solution was evaporated at 80 °C until the solution volume was 10 mL to obtain PMo 12 Solution. 12 6.9 g of phosphoric acid (85 wt%) was added to the solution, and the volume of the solution was fixed to 20 mL. The solution was heated at 100 °C and stirred continuously. After 2 h, the heating was stopped to obtain the vacancy heteropoly acid ( Figure 6 (a)), named as PMo-3 solution.

[0079] 1.8 g of glucose was added to the above solution and reacted at 100 °C for 2 h. The oxidation effect of the substrate glucose was judged by the reduction degree of the PMo-3 solution. During the reaction, 10 μL of the reaction solution was taken at regular intervals, diluted with 3 mL of water, and its absorbance was measured at a wavelength of 700 nm using a visible spectrophotometer.

[0080] The PMo-3-glucose blue solution obtained after the reaction was mixed with 20 mL H 3PO 4 The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump. The polarization curves of the solution at different voltages and 50 mA / cm 2 Constant current electrolysis (electrode area 20 cm 2 ) curve. When the voltage suddenly increases, stop the experiment; Figure 6 As shown in (b), when the voltage reaches the theoretical potential of water electrolysis 1.23 V, the solution electrolysis time is 733 s. The volume of hydrogen collected at the cathode by the drainage method is 92.85 mL, and the calculated hydrogen production Faraday efficiency is 99.79%.

[0081] Example 5

[0082] Weigh 10.368 g MoO 3 The solid was added to 200 mL of water, heated at 80 °C and stirred evenly, then 0.69 g of phosphoric acid (85 wt%) was added dropwise to the solution, and the solution was heated to 140 °C and refluxed until MoO 3 The solution was completely dissolved to obtain a yellow solution. After the solution was cooled, it was filtered and no obvious solid remained. After that, the solution was evaporated at 80 °C until the solution volume was 10 mL to obtain PMo 12 Solution. 12 9.2 g of phosphoric acid (85 wt%) was added to the solution, and the volume of the solution was fixed to 20 mL. The solution was heated at 100 °C and stirred continuously. After 2 h, the heating was stopped to obtain the vacancy heteropoly acid ( Figure 7 (a)), named as PMo-4 solution.

[0083] 1.8 g of glucose was added to the above solution and reacted at 100 °C for 2 h. The oxidation effect of the substrate glucose was judged by the reduction degree of the PMo-4 solution. During the reaction, 10 μL of the reaction solution was taken at regular intervals, diluted with 3 mL of water, and its absorbance was measured at a wavelength of 700 nm using a visible spectrophotometer.

[0084] The PMo-4-glucose blue solution obtained after the reaction was mixed with 20 mL H 3 PO 4 The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump. The polarization curves of the solution at different voltages and 50 mA / cm 2 Constant current electrolysis (electrode area 20 cm 2 ) curve. When the voltage suddenly increases, stop the experiment; Figure 7As shown in (b), when the voltage reaches the theoretical potential of water electrolysis of 1.23 V, the solution electrolysis time is only 820 s. The volume of hydrogen collected at the cathode by the drainage method is 102.40 mL, and the calculated hydrogen production Faraday efficiency is 98.37%.

[0085] Example 6

[0086] Weigh 10.368 g MoO 3 The solid was added to 200 mL of water, heated at 80 °C and stirred evenly, then 0.69 g of phosphoric acid (85 wt%) was added dropwise to the solution, and the solution was heated to 140 °C and refluxed until MoO 3 The solution was completely dissolved to obtain a yellow solution. After the solution was cooled, it was filtered and no obvious solid remained. After that, the solution was evaporated at 80 °C until the solution volume was 10 mL to obtain PMo 12 Solution. 12 11.5 g of phosphoric acid (85 wt%) was added to the solution, and the volume of the solution was fixed to 20 mL. The solution was heated at 100 °C and stirred continuously. After 2 h, the heating was stopped to obtain the vacancy heteropoly acid ( Figure 8 (a)), named as PMo-5 solution.

[0087] 1.8 g of glucose was added to the above solution and reacted at 100 °C for 2 h. The oxidation effect of the substrate glucose was judged by the reduction degree of the PMo-5 solution. During the reaction, 10 μL of the reaction solution was taken at regular intervals, diluted with 3 mL of water, and its absorbance was measured at a wavelength of 700 nm using a visible spectrophotometer.

[0088] The PMo-5-glucose blue solution obtained after the reaction was mixed with 20 mL H 3 PO 4 The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump. The polarization curves of the solution at different voltages and 50 mA / cm 2 Constant current electrolysis (electrode area 20 cm 2 ) curve. When the voltage suddenly increases, stop the experiment; Figure 8 As shown in (b), when the voltage reaches the theoretical potential of water electrolysis 1.23 V, the solution electrolysis time is only 813 s. The volume of hydrogen collected at the cathode by the drainage method is 101.42 mL, and the calculated hydrogen production Faraday efficiency is 98.27%.

[0089] Example 7

[0090] Weigh 10.368 g MoO 3The solid was added to 200 mL of water, heated at 80 °C and stirred evenly, then 0.69 g of phosphoric acid (85 wt%) was added dropwise to the solution, and the solution was heated to 140 °C and refluxed until MoO 3 The solution was completely dissolved to obtain a yellow solution. After the solution was cooled, it was filtered and no obvious solid remained. After that, the solution was evaporated at 80 °C until the solution volume was 10 mL to obtain PMo 12 Solution. 12 13.8 g of phosphoric acid (85 wt%) was added to the solution, and the volume of the solution was fixed to 20 mL. The solution was heated at 100 °C and stirred continuously. After 2 h, the heating was stopped to obtain the vacancy heteropoly acid ( Fig. 9 (a)), named as PMo-6 solution.

[0091] 1.8 g of glucose was added to the above solution and reacted at 100 °C for 2 h. The oxidation effect of the substrate glucose was judged by the reduction degree of the PMo-6 solution. During the reaction, 10 μL of the reaction solution was taken at regular intervals, diluted with 3 mL of water, and its absorbance was measured at a wavelength of 700 nm using a visible spectrophotometer.

[0092] The PMo-6-glucose blue solution obtained after the reaction was mixed with 20 mL H 3 PO 4 The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump. The polarization curves of the solution at different voltages and 50 mA / cm 2 Constant current electrolysis (electrode area 20 cm 2 ) curve. When the voltage suddenly increases, stop the experiment; Fig. 9 As shown in (b), when the voltage reaches the theoretical potential of water electrolysis of 1.23 V, the solution electrolysis time is only 774 s. The volume of hydrogen collected at the cathode by the drainage method is 96.37 mL, and the calculated hydrogen production Faraday efficiency is 98.08%.

[0093] Example 8

[0094] Take the PMo-3 solution prepared in Example 4. Add different contents of organic wastewater to the above solution and 0.3 M PMo 12 The concentration of organic wastewater was made to be about 1 ppm, 10 ppm, 20 ppm, and 100 ppm, and the reaction was carried out at 100 °C for 2 h. The oxidation effect of organic wastewater was judged by the degree of reduction of the solution. During the reaction, 10 μL of the reaction solution was taken at regular intervals, diluted with 3 mL of water, and its absorbance was measured at a wavelength of 700 nm using a visible spectrophotometer. The results are as follows: Fig.10As shown, the degradation efficiency of organic matter by vacuous heteropolyacids is obviously higher than that of intact heteropolyacids.

[0095] The blue solution of PMo-3-organic wastewater (100 ppm) obtained after the reaction was mixed with 20 mL of H 3 PO 4 The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump. The polarization curves of the solution at different voltages and 20 mA / cm 2 Constant current electrolysis (electrode area 1 cm 2 ) curve, such as Fig.11 shown. Fig.11 (a) is the polarization curve of the oxidative oxidation of 100ppm organic wastewater solution by the vacancy heteropoly acid. It can be found that the solution can reach 0.01A / cm at a voltage of about 0.4V. 2 The current density is much lower than the electrolysis voltage (1.23V) of water electrolysis. And as the polarization voltage increases, the polarization current also gradually increases. Fig.11 (b) is the constant current electrolysis curve of the solution, the current density is 0.02A / cm 2 When the voltage suddenly increased to more than 1.23V, the reduced vacancy heteropoly acid in the anode solution was completely oxidized and the oxygen evolution reaction began to occur. The experiment was stopped immediately. In this process, the electrolytic hydrogen production time was maintained for 980s, and the electrolysis voltage was less than the voltage of water electrolysis (1.23V), which proved that the vacancy heteropoly acid can oxidize extremely dilute organic wastewater and successfully release the obtained electrons at the anode. When the voltage suddenly increased, the experiment was stopped. The volume of hydrogen collected at the cathode by the drainage method was 2.44 mL (adding PMo 12 The reaction of 100 ppm organic wastewater is very slow and cannot be electrolyzed. The hydrogen production volume can be considered to be 0). The calculated hydrogen production Faraday efficiency is 98%.

[0096] Example 9

[0097] Take the PMo-3 solution prepared in Example 4. Add organic wastewater to the above solution to make the concentration of organic wastewater about 0.5 mol / L, 1.5 mol / L, 2 mol / L, and 3 mol / L, and react at 100 °C for 2 h. Add the blue PMo-3-organic wastewater solution obtained after the reaction and 20 mL H 3 PO 4 The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump. The polarization curves of the solution at different voltages and 50 mA / cm 2 Constant current electrolysis (electrode area 20 cm 2) curve. When the voltage suddenly increases, stop the experiment; when the voltage reaches the theoretical potential of water electrolysis 1.23 V, Fig.12 As shown, the electrolysis time of the solution is 825 s, 2560 s, 3660 s, and 4786 s, respectively. As the concentration of the organic substrate increases, the reaction rate increases in the same time, and the missing phosphomolybdic acid obtains more electrons from the organic substrate, thereby obtaining a longer electrolytic hydrogen production time. The volume of hydrogen collected at the cathode by the drainage method is 102.99 mL, 320.91 mL, 456.95 mL, and 598.44 mL, respectively. The calculated hydrogen production Faraday efficiency is 98.34%, 98.75%, 98.35%, and 98.5%, respectively, which is close to 100%, indicating that the electrons obtained by the missing phosphomolybdic acid from the organic substrate can be successfully released on the electrode surface and participate in the production of hydrogen.

[0098] Example 10

[0099] Weigh 10.368 g MoO 3 The solid was added to 200 mL of water, heated at 80 °C and stirred evenly, then 0.69 g of phosphoric acid (85 wt%) was added dropwise to the solution, and the solution was heated to 140 °C and refluxed until MoO 3 The solution was completely dissolved to obtain a yellow solution. After the solution was cooled, it was filtered and no obvious solid remained. After that, the solution was evaporated at 80 °C until the solution volume was 10 mL to obtain PMo 12 Solution. The pH of the solution was adjusted to about 2 using concentrated sodium hydroxide solution to obtain a uniform and transparent solution. An appropriate amount of water was added until the total volume of the solution was 20 mL. The pH of the test solution was still 2, and a vacancy heteropoly acid was obtained, named MoPA-2 solution. Fig.13 (a) shows that PMo in MoPA-2 12 The characteristic NMR signal peak (-3.6 ppm) weakened, and a new NMR signal peak appeared at -2 ppm, which was attributed to the vacant heteropoly acid.

[0100] Glucose, a typical biological sugar, was added to the above solution, where the concentration of glucose was 1 mol / L, and the reaction was carried out at 100 °C for 2 h. The oxidation effect of glucose was judged by the degree of reduction of the MoPA-2 solution. During the reaction, 10 μL of the reaction solution was taken at regular intervals, diluted with 3 mL of water, and its absorbance was measured at a wavelength of 700 nm using a visible spectrophotometer.

[0101] The 7 mL MoPA-2-glucose blue solution obtained after the reaction was mixed with 20 mL H 3 PO 4The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump. The polarization curves of the solution at different voltages and 50 mA / cm 2 Constant current electrolysis curve. When the voltage suddenly increases, stop the experiment; Fig.13 As shown in (b), when the voltage reaches the theoretical potential of water electrolysis 1.23 V, the solution electrolysis time is 2992 s. The volume of hydrogen collected at the cathode by the drainage method is 18.61 mL (PMo 12 The volume of hydrogen produced is 14.17 mL), and the calculated hydrogen production Faraday efficiency is 98%.

[0102] Embodiment 11

[0103] Weigh 10.368 g MoO 3 The solid was added to 200 mL of water, heated at 80 °C and stirred evenly, then 0.69 g of phosphoric acid (85 wt%) was added dropwise to the solution, and the solution was heated to 140 °C and refluxed until MoO 3 The solution was completely dissolved to obtain a yellow solution. After the solution was cooled, it was filtered and no obvious solid remained. After that, the solution was evaporated at 80 °C until the solution volume was 10 mL to obtain PMo 12 The pH of the solution was adjusted to about 3 using a concentrated sodium hydroxide solution to obtain a uniform and transparent solution. An appropriate amount of water was added until the total volume of the solution was 20 mL. The pH of the test solution was still 3, and a vacancy heteropoly acid (NMR P spectrum as shown in Fig.14 (a)), named as MoPA-3 solution.

[0104] Glucose, a typical biological sugar, was added to the above solution, where the concentration of glucose was 1 mol / L, and the reaction was carried out at 100 °C for 2 h. The oxidation effect of glucose was determined by the degree of reduction of the MoPA-3 solution. During the reaction, 10 μL of the reaction solution was taken at regular intervals, diluted with 3 mL of water, and its absorbance was measured at a wavelength of 700 nm using a visible spectrophotometer. The kinetic curve is shown in Figure 2. Fig.14 (b) shown.

[0105] The 7 mL MoPA-3-glucose blue solution obtained after the reaction was mixed with 20 mL H 3 PO 4 The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump. The polarization curves of the solution at different voltages and 50 mA / cm 2 Constant current electrolysis curve. When the voltage suddenly increases, stop the experiment; Fig.14As shown in (c), when the voltage reaches the theoretical potential of water electrolysis 1.23 V, the solution electrolysis time is 5656 s. The volume of hydrogen collected at the cathode by the drainage method is 35.00 mL, and the calculated hydrogen production Faraday efficiency is 97.5%.

[0106] Example 12

[0107] Weigh 10.368 g MoO 3 The solid was added to 200 mL of water, heated at 80 °C and stirred evenly, then 0.69 g of phosphoric acid (85 wt%) was added dropwise to the solution, and the solution was heated to 140 °C and refluxed until MoO 3 The solution was completely dissolved to obtain a yellow solution. After the solution was cooled, it was filtered and no obvious solid remained. After that, the solution was evaporated at 80 °C until the solution volume was 10 mL to obtain PMo 12 The pH of the solution was adjusted to about 4 using a concentrated sodium hydroxide solution to obtain a uniform and transparent solution. An appropriate amount of water was added until the total volume of the solution was 20 mL. The pH of the test solution was still 4, and a vacancy heteropoly acid (whose NMR P spectrum is as follows) was obtained. Fig.15 (a)), named as MoPA-4 solution.

[0108] Glucose, a typical biological sugar, was added to the above solution, where the concentration of glucose was 1 mol / L, and the reaction was carried out at 100 °C for 2 h. The oxidation effect of glucose was determined by the degree of reduction of the MoPA-4 solution. During the reaction, 10 μL of the reaction solution was taken at regular intervals, diluted with 3 mL of water, and its absorbance was measured at a wavelength of 700 nm using a visible spectrophotometer. The kinetic curve is shown in Figure 1. Fig.15 (b) shown.

[0109] The 7 mL MoPA-4-glucose blue solution obtained after the reaction was mixed with 20 mL H 3 PO 4 The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump. The polarization curves of the solution at different voltages and 50 mA / cm 2 Constant current electrolysis curve. When the voltage suddenly increases, stop the experiment; Fig.15 As shown in (c), when the voltage reaches the theoretical potential of water electrolysis 1.23 V, the solution electrolysis time is 7339 s. The volume of hydrogen collected at the cathode by the drainage method is 45.65 mL, and the calculated hydrogen production Faraday efficiency is 98%.

[0110] Example 13

[0111] Weigh 10.368 g MoO 3The solid was added to 200 mL of water, heated at 80 °C and stirred evenly, then 0.69 g of phosphoric acid (85 wt%) was added dropwise to the solution, and the solution was heated to 140 °C and refluxed until MoO 3 The solution was completely dissolved to obtain a yellow solution. After the solution was cooled, it was filtered and no obvious solid remained. After that, the solution was evaporated at 80 °C until the solution volume was 10 mL to obtain PMo 12 The pH of the solution was adjusted to about 5 using a concentrated sodium hydroxide solution to obtain a uniform and transparent solution. An appropriate amount of water was added until the total volume of the solution was 20 mL. The pH of the test solution was still 5, and a vacancy heteropoly acid (whose NMR P spectrum is as follows) was obtained. Fig.16 (a)), named as MoPA-5 solution.

[0112] Glucose, a typical biological sugar, was added to the above solution, where the concentration of glucose was 1 mol / L, and the reaction was carried out at 100 °C for 2 h. The oxidation effect of glucose was determined by the degree of reduction of the MoPA-5 solution. During the reaction, 10 μL of the reaction solution was taken at regular intervals, diluted with 3 mL of water, and its absorbance was measured at a wavelength of 700 nm using a visible spectrophotometer. The kinetic curve is shown in Fig.16 (b).

[0113] The 7 mL MoPA-5-glucose blue solution obtained after the reaction was mixed with 20 mL H 3 PO 4 The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump. The polarization curves of the solution at different voltages and 50 mA / cm 2 Constant current electrolysis curve. When the voltage suddenly increases, stop the experiment; Fig.16 As shown in (c), when the voltage reaches the theoretical potential of water electrolysis 1.23 V, the solution electrolysis time is 8770 s. The volume of hydrogen collected at the cathode by the drainage method is 54.83 mL, and the calculated hydrogen production Faraday efficiency is 98.5%.

[0114] Embodiment 14

[0115] Weigh 10.368 g MoO 3 The solid was added to 200 mL of water, heated at 80 °C and stirred evenly, then 0.69 g of phosphoric acid (85 wt%) was added dropwise to the solution, and the solution was heated to 140 °C and refluxed until MoO 3 The solution was completely dissolved to obtain a yellow solution. After the solution was cooled, it was filtered and no obvious solid remained. After that, the solution was evaporated at 80 °C until the solution volume was 10 mL to obtain PMo 12The pH of the solution was adjusted to about 6 using a concentrated sodium hydroxide solution to obtain a uniform and transparent solution. An appropriate amount of water was added until the total volume of the solution was 20 mL. The pH of the test solution was still 6, and a vacancy heteropoly acid was obtained, which was named MoPA-6 solution. Fig.17 As shown in (a), in the NMR P spectrum of MoPA-6, PMo 12 The characteristic peak (-3.6 ppm) of PMo completely disappeared, and a new NMR signal peak appeared at about -1 ppm, which was attributed to the vacancy heteropoly acid. 12 decomposition, a large amount of PO 4 3- , HPO 4 2- , H 2 PO 4 3- (1.5 ppm) Fig.17 (a)).

[0116] Glucose, a typical biological sugar, was added to the above solution, where the concentration of glucose was 1 mol / L, and the reaction was carried out at 100 °C for 2 h. The oxidation effect of glucose was determined by the degree of reduction of the MoPA-6 solution. During the reaction, 10 μL of the reaction solution was taken at regular intervals, diluted with 3 mL of water, and its absorbance was measured at a wavelength of 700 nm using a visible spectrophotometer. The kinetic curve is shown in Fig.17 (b).

[0117] The 7 mL MoPA-6-glucose blue solution obtained after the reaction was mixed with 20 mL H 3 PO 4 The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump. The polarization curves of the solution at different voltages and 50 mA / cm 2 Constant current electrolysis curve. When the voltage suddenly increases, stop the experiment; Fig.17 As shown in (c), when the voltage reaches the theoretical potential of water electrolysis 1.23 V, the solution electrolysis time is 5584 s. The volume of hydrogen collected at the cathode by the drainage method is 34.56 mL, and the calculated hydrogen production Faraday efficiency is 97.5%.

[0118] Embodiment 15

[0119] Take the MoPA-5 solution prepared in Example 11. Add typical biosaccharides (fructose, xylose, arabinose, mannose, maltose, sucrose) to different solutions above, where the concentration of biosaccharides is 1 mol / L, and react at 100 °C for 2 h. The oxidation effect of biosaccharides is judged by the degree of reduction of the MoPA-5 solution. During the reaction, take 10 μL of the reaction solution at regular intervals, dilute it with 3 mL of water, measure its absorbance at a wavelength of 700 nm using a visible spectrophotometer, calculate and draw the kinetic curve, and the results are as follows: Fig.18 As shown, within a period of reaction time, the absorbance values ​​increased, indicating that the prepared lacuna heteropolyacid had a good oxidation effect on different types of biological sugars.

[0120] Example 16

[0121] Take the PMo-3 solution prepared in Example 4, add typical biomass sugar (glucose) to it, so that the concentration of glucose is 0.5 M, and react at 100 °C for 2 h. The PMo-3-glucose blue solution obtained after the reaction is mixed with 20 mL H 3 PO 4 The solution (1 mol / L) was pumped into the anode and cathode of the electrolytic cell using a peristaltic pump, and the volume of hydrogen at the cathode was collected using the drainage method. When the voltage suddenly increased, the experiment was stopped.

[0122] Subsequently, the remaining glucose solution in the solution was further oxidized by the oxidatively regenerated vacant PMo-3. After heating for 2 h, the obtained blue solution was continued to be passed into the electrolytic cell for electrolytic hydrogen production experiments. This cycle was repeated six times, and the polarization curves of the solution at different voltages and 50 mA / cm during each electrolysis experiment were recorded. 2 Constant current electrolysis curve, the results are as follows Fig.19 shown. Fig.19 (a) is the test result of polarization current. During the cycle, the polarization current can reach 1A within 1V, indicating that the vacancy heteropoly acid exhibits good oxidation performance in the cycle experiment. Fig.19 (b) is the constant current electrolysis test in the cycle experiment. The working voltage is below 1.23 V, which is lower than the theoretical voltage of water electrolysis (1.23 V). This can greatly reduce the energy consumption of hydrogen production by electrolysis.

[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a vacancy heteropoly acid, characterized in that: The vacancy heteropoly acid is prepared by using phosphomolybdic acid as a raw material, adding a high concentration acid for acidification and heating; the high concentration acid is 0.1-6 M phosphoric acid; the heating temperature is 100-120° C., and the heating time is 0.5-2 h.

2. The method for preparing the vacant heteropoly acid according to claim 1, characterized in that: The phosphomolybdic acid is H3PMo 12 O 40 Solution or PMo 12 Solution.

3. The method for preparing the vacant heteropoly acid according to claim 1, characterized in that: The preparation method of phosphomolybdic acid is as follows: molybdenum trioxide and phosphoric acid are used as raw materials, and the temperature of heating reflux is 100-150° C., and the time is 2-10 h.

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