Double-cathode electrochemical oxidation system and method based on boron-doped polyphthalocyanine iron composite cathode material

Abstract

The invention discloses a double-cathode electrochemical oxidation system and method based on a boron-doped polyphthalocyanine iron composite cathode material. The system comprises a double-tank reactor, and an anode, a modified cathode, a catalytic cathode and an aeration head which are arranged in the double-tank reactor, the anode is connected to the positive pole of the direct-current power supply; the modified cathode and the catalytic cathode which are arranged at intervals are connected to the negative electrode of the direct-current power supply; the modified cathode comprises a substrate and a carbon nanotube loaded on the substrate; the catalytic cathode comprises a substrate and boron-doped polyphthalocyanine iron loaded on the substrate; the method comprises the following steps: electrolyzing by using a carbon nanotube as a modified electrode to form hydrogen peroxide; the method comprises the following steps: performing boron doping on polyphthalocyanine iron to obtain a catalytic electrode of a PFePc-B material, and activating hydrogen peroxide to form hydroxyl radicals; therefore, HO in-situ generation and. OH activation can be efficiently and synchronously driven, and efficient degradation of refractory organic pollutants is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical water treatment, and particularly relates to a dual-cathode electrochemical oxidation system and method based on a boron-doped iron phthalocyanine composite cathode material. Background Art

[0002] Electrochemical advanced oxidation technologies represented by electro-Fenton (EF) have broad application prospects in the treatment of refractory organic wastewater. In particular, they have been applied to refractory organic wastewaters such as phenol wastewater, antibiotic wastewater, pesticide wastewater, and landfill leachate. In the electro-Fenton system, oxygen generates H2O2 through a two-electron oxygen reduction reaction (ORR) on the cathode surface, and further reacts with Fe 2+ in the solution to generate ·OH for degrading organic wastewater. In the series of catalytic cycles of electro-Fenton degradation, the catalytic performance of the cathode determines the yield of H2O2 and the catalytic efficiency of Fe 2+ / Fe 3+ and is a key factor for effectively degrading pollutants. The excellent conductivity of carbon paper promotes the rapid transfer of electrons between electrodes, improves the electro-chemical reaction efficiency, helps to continuously generate reactive oxygen species, and its high specific surface area provides abundant active sites, enhancing the catalyst loading and dispersion. The porous structure is conducive to the diffusion of reactants and products, improving the mass transfer efficiency, and is an ideal choice for cathode materials.

[0003] Traditional Fenton technology is based on the reaction between ferrous ions (Fe²⁺) and hydrogen peroxide (H2O2). Fe²⁺ catalyzes H2O2 to generate highly oxidizing hydroxyl radicals (·OH). Its reaction principles are shown in Formula 1 and Formula 2. However, traditional Fenton technology also has many limitations. First, its reaction conditions are relatively harsh, and the optimal reaction pH value is usually between 3 and 9. Beyond this range, the catalytic activity of ferrous ions will be significantly reduced, resulting in a decrease in reaction efficiency. Second, a large amount of iron mud is generated during the reaction. These iron muds not only require subsequent treatment and disposal, increasing the treatment cost, but also may cause secondary pollution if not properly treated. In addition, the utilization rate of hydrogen peroxide in traditional Fenton technology is relatively low, and a large amount of hydrogen peroxide is decomposed without participating in the reaction, causing waste of reagents and further increasing the treatment cost. At the same time, due to the limited rate of free radical generation during the reaction, the reaction rate is slow and the treatment efficiency is low, which is not suitable for large-scale sewage treatment scenarios.

[0004] Fe 2+ +H2O2→Fe 3+ +OH - +HO· (K = 76M -1 ·S -1 ) (1) Fe3+ +H2O2 → Fe 2+ +H + +HO2· (K = 0.01 - 0.02 M -1 ·S -1 )(2) Heteroatom doping can effectively adjust the local structure and electron cloud density of two-dimensional materials, improving their optical, electrical, and catalytic properties. Introducing heteroatoms with specific atomic radii, electronegativities, and electron orbital structures into the material can induce structural distortion, lattice defects, and redistribution of local charges. On the one hand, atomic doping can regulate local Lewis acidity and basicity, interacting better with reactants; on the other hand, the introduction of heteroatoms can induce surface / lattice defects as new active sites, usually showing a synergistic effect on catalytic performance. Therefore, heteroatom doping can rationally regulate the physical and chemical properties of catalysts at the atomic level, improving the inherent catalytic performance of catalysts. Summary of the Invention

[0005] The object of the present invention is to use carbon nanotubes and boron-doped iron phthalocyanine (PFePc-B) to respectively load carbon paper to obtain a modified cathode and a catalytic cathode; the modified cathode can efficiently produce H2O2, and the catalytic cathode can effectively produce active substances such as hydroxyl radicals. Both electrodes have excellent stability and can be recycled multiple times. In addition, a direct-current dual-cathode electro-Fenton reactor is constructed by combining the two cathodes with a device containing a side aeration system, which has a good degradation effect on organic pollutants.

[0006] In the first aspect, the present invention provides a dual-cathode electrochemical oxidation system based on a boron-doped iron phthalocyanine composite cathode material, which includes a dual-chamber reactor, and an anode, a modified cathode, a catalytic cathode, and an aeration head arranged in the dual-chamber reactor; the anode is connected to the positive pole of a direct-current power supply; the mutually spaced modified cathode and catalytic cathode are both connected to the negative pole of the direct-current power supply; the modified cathode includes a substrate and carbon nanotubes loaded on the substrate; the catalytic cathode includes a substrate and boron-doped iron phthalocyanine loaded on the substrate; the aeration head supplies oxygen to the modified cathode. The modified cathode reacts to produce hydrogen peroxide. The catalytic cathode immediately activates hydrogen peroxide to produce hydroxyl radicals for degrading organic pollutants.

[0007] Preferably, the boron-doped iron phthalocyanine is obtained by mixing iron phthalocyanine with sodium borohydride and then calcining, so that sodium borohydride undergoes co-pyrolysis, and boron atoms are embedded in the iron phthalocyanine skeleton in a substitution and / or interstitial form.

[0008] Preferably, the mass ratio of iron phthalocyanine to sodium borohydride is (5 - 6):(2 - 4).

[0009] Preferably, the temperature for calcining after mixing iron phthalocyanine and sodium borohydride is greater than or equal to 300°C to 400°C.

[0010] Preferably, the iron phthalocyanine is obtained by mixing pyromellitic dianhydride, ferrous chloride tetrahydrate, urea, ammonium chloride, and ammonium molybdate in a mass ratio of (83 - 85) : (26 - 28) : (162 - 164) : (40 - 42) : 1, grinding them, and then calcining.

[0011] Preferably, the substrates of the modified cathode and the catalytic cathode are both made of carbon paper. The carbon nanotubes in the modified cathode are bonded to the surface of the carbon paper through a conductive binder. The boron-doped iron phthalocyanine in the modified cathode is bonded to the surface of the carbon paper through a conductive binder.

[0012] Preferably, the distance between the modified cathode and the catalytic cathode is 0.5 cm to 1 cm; the aeration head is arranged on the side of the modified cathode away from the catalytic cathode.

[0013] In a second aspect, the present invention provides an organic wastewater dual-cathode electrochemical oxidation method, which uses the aforementioned dual-cathode electrochemical oxidation system; the method is as follows: the organic wastewater to be treated added with an electrolyte is introduced into the cathode reaction chamber of the dual-chamber reactor; a voltage is applied between the anode and the cathode through a DC power supply, and hydrogen peroxide is generated by electrolytic reaction of the modified cathode. The catalytic cathode immediately activates hydrogen peroxide to generate hydroxyl radicals. The hydroxyl radicals oxidize and degrade the organic pollutants in the organic wastewater.

[0014] Preferably, the potential applied by the DC power supply between the cathodes is 0.9 to 0.7 V vs. Ag / AgCl.

[0015] In a third aspect, the present invention provides an application of a boron-doped iron phthalocyanine composite material as a catalytic electrode in a dual-cathode electrochemical oxidation system; wherein, the boron-doped iron phthalocyanine composite material is obtained by bonding boron-doped iron phthalocyanine to a substrate; the boron-doped iron phthalocyanine is obtained by mixing iron phthalocyanine and sodium borohydride and then calcining, so that sodium borohydride undergoes co-pyrolysis, and boron atoms are embedded in the iron phthalocyanine skeleton in a substitution or interstitial form.

[0016] The beneficial effects of the present invention are as follows: 1. The present invention boron-dopes iron phthalocyanine to obtain the PFePc-B material. The high conductivity and extended conjugated structure of PFePc-B (enhanced by boron doping) form an efficient electron transport network under an applied electric field. In addition, under an applied electric field, the high-conductivity framework of PFePc-B (conductivity ≥ 10 S / cm) forms a fast electron channel, and the current density increases to 20 mA / cm² (only 3 mA / cm² for traditional PFePc). The electron-deficient property of boron (electronegativity 2.04) combines with the conjugated framework of iron phthalocyanine to form a gradient energy band structure, significantly reducing the electron transport barrier. Boron atoms act as electron traps, inhibiting electron-hole recombination. Moreover, the synergistic effect between the boron doping sites and the Fe-N4 active centers increases the charge separation efficiency by more than 50%.

[0017] 2. The present invention uses carbon nanotubes as a modified electrode to electrolyze and form hydrogen peroxide; uses a catalytic electrode of the PFePc-B material obtained by boron-doping iron phthalocyanine to activate hydrogen peroxide to form hydroxyl radicals; under electrocatalytic conditions, the PFePc-B material can significantly increase the reaction kinetic electron transport speed; therefore, the present invention can efficiently drive the in-situ generation of H2O2 and the activation of ·OH synchronously, achieving the efficient degradation of refractory organic pollutants.

[0018] 3. Compared with the prior art, the advantage of metallic iron lies in the matching between its redox potential and the efficient activation ability of H2O2. The standard reduction potential of Fe³⁺ / Fe²⁺ is +0.77 V vs. SHE (standard hydrogen electrode), while the potential range for H2O2 to decompose into ·OH is +0.38~+0.50 V vs. SHE. This potential difference is sufficient to drive the activation of H2O2 and avoid the potential being too high, which makes it difficult for Fe³⁺ to be reduced and regenerated; while the potential of metallic Cu is relatively low, resulting in insufficient activation efficiency of H2O2 and it is difficult for Cu⁺ to be regenerated after being easily oxidized to Cu²⁺; the potentials of metals such as Mn and Co are too high, which will directly oxidize H2O2 into O2 rather than ·OH.

[0019] 4. Fe 2+ 's d 6 electron configuration enables it to have a relatively high antibonding orbital filling degree in the coordination field, and it is easy to form a σ coordination with the O-O bond of H2O2, promoting the cleavage of the O-O bond. Fe 3+ 's d 5 configuration efficiently regenerates Fe²⁺ through a single-electron transfer mechanism to maintain the catalytic cycle. Low-spin state stability In acidic media, Fe²⁺ tends to form a low-spin state (coordinated by strong-field ligands such as H2O), and the d electron distribution is concentrated, which is conducive to rapid electron transfer. Description of the Drawings

[0020] Figure 1Schematic diagram of the dual-cathode electrochemical oxidation system provided for Example 2.

[0021] Figure 2 SEM images of iron phthalocyanine and boron-doped iron phthalocyanine used in Examples 2-5 of the present invention (where (a) and (b) both correspond to undoped iron phthalocyanine; (c), (d), (e), and (f) correspond to boron-doped iron phthalocyanine in Examples 3, 4, 5, and 2 respectively).

[0022] Figure 3 Comparison chart of in-situ production of H2O2 for Comparative Examples 1, 2, and 3.

[0023] Figure 4 Comparison chart of the degradation effects of BPA for Examples 2, 3, 4, 5 and Comparative Example 4.

[0024] Figure 5 Comparison chart of the degradation effects of BPA for Example 2 and Comparative Example 5.

[0025] Figure 6 Comparison chart of the degradation effects of BPA for Example 2 and Comparative Examples 6 and 7.

[0026] Figure 7 Comparison chart of the degradation effects of BPA for Examples 2, 6, 7, and 8.

[0027] Figure 8 Comparison chart of XRD patterns of PFePc and PFePc-B prepared in Examples 2, 3, 4, and 5.

[0028] Figure 9 Test result chart of the cyclic stability of the catalytic electrode in the dual-cathode electrochemical oxidation system provided for Example 2. Detailed implementation manners

[0029] The following will be described in conjunction with the drawings and examples, but the present invention is not limited to the following representative embodiments.

[0030] Example 1 A preparation method of a boron-doped iron phthalocyanine-carbon paper composite cathode material (PFePc-B) includes the following steps: (1) Weigh 1.26 g of pyromellitic dianhydride, 0.404 g of ferrous chloride tetrahydrate, 2.46 g of urea, 0.6 g of ammonium chloride, and 15 mg of ammonium molybdate. Use a mortar to fully grind and mix the accurately weighed medicines; place the obtained mixed powder in a muffle furnace and heat it to 400 °C at a rate of 5 °C / min and calcine for 3 hours. After washing and drying, obtain iron phthalocyanine (PFePc) powder.

[0031] (2) Mix the PFePc obtained in step (1) with NaBH4 at a mass ratio of 5:2 and grind them. Then, heat them to 400 °C at a rate of 5 °C / min under a nitrogen atmosphere and calcine for 4 hours. After washing and drying, boron-doped polyphthalocyanine (PFePc-B 400 ) is obtained. After the calcination is completed, wait for the tubular furnace to cool to room temperature and take out the product. Wash and centrifuge it several times with ethanol and ultrapure water until the centrifuged supernatant is clear. Then, put it into a vacuum drying oven for drying (80 °C, 12 h). In this step, boron doping is achieved through the co-pyrolysis of NaBH4. Boron atoms are embedded in the polyphthalocyanine iron skeleton in a substitutional or interstitial form, inducing lattice distortion and local charge redistribution.

[0032] (3) Mix 10 mg of the boron-doped polyphthalocyanine iron (PFePc-B 400 ) obtained in step (2) with a Nafion solution and ethanol at a volume ratio of 0.01:1. After ultrasonic dispersion, uniformly coat it on the surface of the pretreated carbon paper to form a composite catalytic cathode with a self-built electric field and electron-rich iron active sites. The composite catalytic cathode obtained in this step has a three-dimensional porous structure, a specific surface area ≥ 200 m² / g, and a pore size distribution of 2 nm - 50 nm, significantly improving the heterogeneous electron transfer efficiency of H2O2.

[0033] The boron-doped polyphthalocyanine iron material prepared in this example has a large π-bond conjugated structure that can promote electron transfer at the catalytic interface. The unique electron-rich property of the iron center and the reversible redox potential are expected to enable it to exhibit good catalytic activation performance for hydrogen peroxide.

[0034] Boron doping causes the crystal plane diffraction peak of polyphthalocyanine iron (PFePc) to shift to a lower angle (from 25° to 24.1°), indicating that the entry of boron atoms causes lattice distortion and an increase in the interlayer spacing, further confirming that boron doping introduces more structural defects and increases the active sites. Compared with the introduction of boron into ordinary carbon materials, polyphthalocyanine iron has rich reactivity, a strong coordination ability with metal ions, and excellent conductivity. Therefore, it performs more excellently in electrochemical reactions than ordinary carbon materials. After doping boron, it provides electrons to the Fe center of PFePc, optimizing the electronic configuration of Fe. XPS data shows that the binding energy of Fe decreases, indicating an increase in the electron density of Fe, thus enhancing the interaction between Fe and O2 (such as filling the antibonding orbital) and promoting the cleavage of the O - O bond.

[0035] In this embodiment, a polymerization network is formed through the covalent connection of iron phthalocyanine units, and boron atoms are doped in the phthalocyanine ring or the linking group. Therefore, the boron hybrid orbitals will expand the conjugated system of polyiron phthalocyanine: the polymerization structure enhances the π-π conjugation, promotes electron delocalization, and improves the overall conductivity of the material; boron participates in the synergistic doping effect to form multiple electron transport channels, enhancing the charge transfer efficiency through sp² hybridization, and the boron in the polyphthalocyanine ring further regulates the electronic state of the Fe active center. Moreover, the covalently connected polymerization structure has higher mechanical strength and chemical stability. Especially under strong acid / strong base or high potential conditions, the corrosion resistance and cycle life of PFePc-B are significantly better than those of monomeric materials.

[0036] Example 2 A dual-cathode electrochemical oxidation system based on a boron-doped polyiron phthalocyanine composite cathode material is constructed through the following process: (1) Prepare the carbon paper substrate: Cut the carbon paper with a thickness of 3 mm into a rectangle with dimensions of 1.5 cm × 2 cm, ultrasonically clean the carbon paper with absolute ethanol for 20 min to complete degreasing; ultrasonically clean the carbon paper with ultrapure water for 20 min to remove the residual absolute ethanol; place the carbon paper in an oven and dry it, marked as the pretreated carbon paper substrate.

[0037] (2) Prepare the modified cathode: Mix 4 mL of ethanol with 40 μL of Nafion, and then add 10 mg of carbon nanotubes (CNTs) to configure a uniformly dispersed mixed system; perform ultrasonic treatment on the mixed solution for 1 h to ensure the full dispersion of the Nafion polymer and the uniform distribution of the carbon nanotubes in the solution; finally, uniformly load the mixed solution obtained from the above treatment in this step onto the surface of the pretreated carbon paper substrate obtained in step (1) by titration to obtain the modified cathode; clamp it with an electrode clip and place it in the cathode chamber. In some other embodiments, Nafion can be replaced by other conductive binders. The modified cathode obtained in this step has a self-built electric field and electron-rich iron active sites.

[0038] (3) Prepare the catalytic cathode: Introduce 10 mg of the boron-doped polyiron phthalocyanine (PFePc-B 400 ) prepared in Example 1 as the functional material into a mixed system of 2 mL of ethanol and 40 μL of Nafion solution, and then transfer it to an ultrasonic reactor for 1 h of high-intensity dispersion treatment to ensure that PFePc-B 400 and Nafion form a homogeneous and stable composite dispersion system in the solvent. Finally, use a micropipette to uniformly coat the dispersion drop by drop on the surface of the pretreated carbon paper in step (1) to obtain a boron-doped polyiron phthalocyanine (PFePc-B 400 )-based catalytic cathode, clamp it with an electrode clip and place it in the cathode chamber.

[0039] (4)Construct a dual-cathode electro-chemical oxidation system: As Figure 1 shown, the dual-cathode electro-chemical oxidation system includes a dual-chamber reactor 1, a DC power supply 2, the modified cathode 3 prepared in step (2), the catalytic cathode 4 prepared in step (3), an anode 5, a cathode-side aeration system 6, an aeration head 7, and an ion exchange membrane 8.

[0040] The dual-chamber reactor 1 includes a cathode reaction chamber and an anode reaction chamber. An exchange channel is connected between the cathode reaction chamber and the anode reaction chamber. An ion exchange membrane 8 is provided in the exchange channel. The anode 5 is disposed in the anode reaction chamber; the modified cathode 3 and the catalytic cathode 4 are both disposed in the cathode reaction chamber. The modified cathode 3 is used to in-situ generate hydrogen peroxide; the catalytic cathode 4 is used to generate hydroxyl active components.

[0041] The aeration head 7 is disposed at the bottom of the cathode reaction chamber and is connected to the external cathode-side aeration system 6 through a gas pipe. The cathode-side aeration system 6 is used to continuously supply high-purity oxygen (purity ≥ 99.9%) to the aeration head 7, so as to continuously aerate the water body in the cathode reaction chamber, thereby constructing a gas-liquid-solid three-phase reaction interface to enhance the mass transfer efficiency.

[0042] The DC power supply 2 is provided with a positive terminal and two negative terminals; the positive terminal is connected to the anode 5; the two negative terminals are respectively connected to the modified cathode 3 and the catalytic cathode 4; the modified cathode 3 is adjacent to the aeration head 7; the catalytic cathode 4 is located on the side of the modified cathode 3 away from the aeration head 7. The distance between the catalytic cathode and the modified cathode is maintained between 0.5 cm and 1 cm. The dual-cathode spatial separation design helps to inhibit the consumption of H2O2 by the anodic oxygen evolution side reaction.

[0043] In this embodiment, the distance between the cathode reaction chamber and the anode reaction chamber is set to 5 cm.

[0044] In this embodiment, the material of the anode 5 is platinum (Pt).

[0045] In this embodiment, the electrolyte in the dual-chamber reactor 1 is a 0.5 mol / L sodium sulfate (Na2SO4) solution.

[0046] In some embodiments, an oxygen cylinder is provided in the cathode-side aeration system 6.

[0047] The dual-cathode electrochemical oxidation system constructed in this example is used for the degradation of polluted water; in this example, the pollutant in the polluted water to be treated is bisphenol A (BPA); the polluted water is introduced into the cathode reaction chamber; the aeration flow rate of oxygen is 0.5 L / min; the DC power supply 2 is started, and the potential difference between the anode and the cathode is regulated. A potential of -0.9 V vs. Ag / AgCl is applied to both cathodes. The production of H2O2 and the concentration of BPA are detected at different times, and the results Figure 4 are shown. The degradation efficiency of BPA is observed after 2 h.

[0048] In the reaction, hydrogen peroxide is in-situ generated on the modified cathode 3; the catalytic cathode 4 further generates hydroxyl active components based on hydrogen peroxide; among them, by controlling the voltage of the modified cathode (-0.9 V vs. Ag / AgCl), the oxygen reduction reaction (ORR) occurs on the surface of the modified cathode, continuously generating H2O2; by controlling the voltage of the catalytic cathode (-0.9 V vs. Ag / AgCl), the heterogeneous electron transfer process of H2O2 (H2O2 + e⁻ → ·OH + OH⁻) is selectively triggered to achieve the continuous in-situ generation of ·OH, and then the deep mineralization of pollutants is achieved through radical attack (·OH + pollutant → CO2 + H2O). Therefore, the dual-cathode electrochemical oxidation system provided in this example can synchronously drive the in-situ generation of H2O2 and the activation of ·OH, and achieve a degradation rate of bisphenol A (BPA) greater than or equal to 95% within 120 minutes in the pH range of 3 to 9.

[0049] Through the dual-chamber spatial separation design in this example, the competitive consumption of the accumulation of H2O2 by the anodic oxidation side reaction (such as oxygen evolution on the Pt anode) in the traditional single-chamber system is effectively avoided, and the generation kinetics of ·OH is significantly enhanced.

[0050] Comparative Example 1 A single-cathode electrochemical oxidation system, the difference between this example and Example 1 is that: the catalytic electrode is not provided.

[0051] A sodium sulfate (Na2SO4) solution with a concentration of 0.5 mol / L is loaded into the dual-chamber reactor 1 as the electrolyte; oxygen aeration is carried out at a flow rate of 0.5 L / min; the DC power supply is started, and the potential difference between the anode and the cathode is regulated. A potential of -0.9 V (vs. Ag / AgCl) is applied to both cathodes. The production of H2O2 is detected at different times, and the results are as Figure 3 shown.

[0052] Comparative Example 2 A single-cathode electrochemical oxidation system, the difference between this example and Comparative Example 1 is that: the material of the catalytic electrode is different. In this comparative example, the original carbon paper is directly used as the catalytic electrode.

[0053] In the dual-cell reactor 1, a sodium sulfate (Na2SO4) solution with a concentration of 0.5 mol / L was loaded as the electrolyte; oxygen aeration was carried out at a flow rate of 0.5 L / min; the DC power supply was started, and the potential difference between the anode and the cathode was regulated. A potential of -0.9 V vs. Ag / AgCl was applied to both cathodes, and the production of H2O2 was detected at different times. The results are as Figure 3 shown.

[0054] Comparative Example 3 A single-cathode electrochemical oxidation system. The difference between this example and Comparative Example 1 is that the material of the catalytic electrode is different. In this comparative example, conductive carbon black (CB) was used as the catalytic electrode.

[0055] In the dual-cell reactor 1, a sodium sulfate (Na2SO4) solution with a concentration of 0.5 mol / L was loaded as the electrolyte; oxygen aeration was carried out at a flow rate of 0.5 L / min; the DC power supply was started, and the potential difference between the anode and the cathode was regulated. A potential of -0.9 V (vs. Ag / AgCl) was applied to both cathodes, and the production of H2O2 was detected at different times. The results are as Figure 3 shown.

[0056] From Figure 3 it can be seen that the production of H2O2 of the original carbon paper and conductive carbon black (CB) is relatively low without the loading of carbon nanotubes (CNTs); it shows that the carbon nanotube-loaded carbon paper as a modified electrode helps to increase the production of H2O2.

[0057] Example 3 A dual-cathode electrochemical oxidation system based on a boron-doped iron phthalocyanine composite cathode material. The difference between this example and Example 2 is that the catalytic electrode used is different; in this example, the catalytic electrode is PFePc-B100; The difference between the preparation method of this catalytic electrode and the preparation method provided in Example 1 is only that the calcination temperature after mixing iron phthalocyanine (PFePc) powder with NaBH4 is 100 °C.

[0058] Example 4 A dual-cathode electrochemical oxidation system based on a boron-doped iron phthalocyanine composite cathode material. The difference between this example and Example 2 is that the catalytic electrode used is different; in this example, the catalytic electrode is PFePc-B200; The difference between the preparation method of this catalytic electrode and the preparation method provided in Example 1 is only that the calcination temperature after mixing iron phthalocyanine (PFePc) powder with NaBH4 is 200 °C.

[0059] Example 5 A dual-cathode electrochemical oxidation system based on a boron-doped iron phthalocyanine composite cathode material. The difference between this example and Example 2 lies in the different catalytic electrodes used. In this example, the catalytic electrode is PFePc-B300. The difference between the preparation method of this catalytic electrode and the preparation method provided in Example 1 is only that: the calcination temperature after mixing iron phthalocyanine (PFePc) powder and NaBH4 is 300 °C.

[0060] The overall microstructure and local microstructure of undoped boron iron phthalocyanine (PFePc) are shown in parts (a) and (b) of Figure 2 respectively; it can be seen from the figure that the micro surface of PFePc presents a smooth two-dimensional layered structure with a small specific surface area. The microstructure of boron-doped iron phthalocyanine (PFePc-B 100 ) in the catalytic electrode of Example 3 is shown in part (c) of Figure 2 respectively; the microstructure of boron-doped iron phthalocyanine (PFePc-B 200 ) in the catalytic electrode of Example 4 is shown in part (d) of Figure 2 respectively; the microstructure of boron-doped iron phthalocyanine (PFePc-B 300 ) in the catalytic electrode of Example 5 is shown in part (e) of Figure 2 respectively; the microstructure of boron-doped iron phthalocyanine (PFePc-B 400 ) in the catalytic electrode of Example 2 is shown in part (f) of Figure 2 respectively; among them, Figure 2 the magnification ratio of part (a) in

[0061] is 50,000 times, and the magnification ratios of parts (b), (c), (d), (e), and (f) are 100,000 times. Figure 2 Comparing parts (c), (d), (e), and (f) in Figure 2 , it can be seen that boron doping makes the micro surface of the material appear a broken structure, increasing the specific surface area of the material, and within the range of 100 °C to 400 °C, as the calcination temperature increases, the broken structure gradually increases. For example,

[0062] In part (f) of Figure 8 , it can be seen that there are many broken structures of different sizes on the surface of the sample when the calcination temperature is 400 °C. Figure 8It can be seen that two characteristic peaks appear at 28° and 29.5° for the iron boride-doped polyphthalocyanine used in Examples 2-5, indicating that iron and boron atoms have been successfully introduced into the crystal structure of the polymer.

[0063] Comparative Example 4 A dual-cathode electrochemical oxidation system based on an iron boride-doped polyphthalocyanine composite cathode material. The difference between this example and Example 2 is that the catalytic electrode used is different; in this example, the catalytic electrode is stainless steel (SSM). The comparison of the 120-minute degradation efficiency of BPA in Examples 2, 3, 4, 5 and Comparative Example 4 is as Figure 4 shown; from Figure 4 it can be seen that when the PFePc-B catalytic electrode (Example 3) calcined at 100 °C was used, only 19.5% of BPA was degraded after 120 minutes of treatment. When the PFePc-B catalytic electrode (Example 4) calcined at 200 °C was used, only 32% of BPA was degraded after 120 minutes of treatment. When stainless steel (SSM) was used as the catalytic electrode (Comparative Example 3), only about 45% of BPA was degraded after 120 minutes of treatment. When the PFePc-B catalytic electrode (Example 5) calcined at 300 °C was used, only 68% of BPA was degraded after 120 minutes of treatment. While when the PFePc-B catalytic electrode (Example 2) calcined at 400 °C was used, only about 74% of BPA was degraded after 120 minutes of treatment.

[0064] It can be seen that introducing the PFePc-B catalytic electrode calcined at 400 °C helps to significantly improve the degradation efficiency of the dual-cathode electrochemical oxidation system for BPA pollutants.

[0065] Comparative Example 5 A dual-cathode electrochemical oxidation system based on an iron boride-doped polyphthalocyanine composite cathode material. The difference between this example and Example 2 is that no electricity is supplied during the working process.

[0066] The comparison of the 120-minute degradation efficiency of BPA in Example 2 and Comparative Example 5 is as Figure 5 shown; from Figure 5 it can be seen that current has a great influence on the degradation efficiency of BPA pollutants.

[0067] Comparative Example 6: A dual-cathode electrochemical oxidation system based on an iron boride-doped polyphthalocyanine composite cathode material. The difference between this example and Example 2 is that the catalytic electrode used is different; in this example, the catalytic electrode is boron-doped copper phthalocyanine PCuPc-B400; The difference between the preparation method of boron-doped copper phthalocyanine PCuPc-B400 in this comparative example and the preparation method provided in Example 1 is only that: iron phthalocyanine (PFePc) is replaced by copper phthalocyanine (PCuPc). The synthesis process of copper phthalocyanine (PCuPc) is as follows: pyromellitic dianhydride, copper dichloride dihydrate, urea, ammonium chloride, and ammonium molybdate are mixed and ground according to the mass ratio of (82-84):(22-23):164:40:1. Specifically, in the experiment, 1.26 g of pyromellitic dianhydride, 0.341 g of copper dichloride dihydrate, 2.46 g of urea, 0.6 g of ammonium chloride, and 15 mg of ammonium molybdate are placed in a muffle furnace and heated to 400 °C at a rate of 5 °C / min and calcined for 3 hours. After washing and drying, copper phthalocyanine (PCuPc) powder is obtained.

[0068] Comparative Example 7: A dual-cathode electrochemical oxidation system based on a boron-doped iron phthalocyanine composite cathode material. The difference between this example and Example 2 is that: the catalytic electrode used is different; in this example, the catalytic electrode is boron-doped cobalt phthalocyanine PCoPc-B400; The difference between the preparation method of boron-doped cobalt phthalocyanine PCoPc-B400 in this comparative example and the preparation method provided in Example 1 is only that: iron phthalocyanine (PFePc) is replaced by cobalt phthalocyanine (PCoPc). The synthesis process of cobalt phthalocyanine (PCoPc) is as follows: pyromellitic dianhydride, cobalt chloride hexahydrate, urea, ammonium chloride, and ammonium molybdate are mixed and ground according to the mass ratio of (82-84):(30-32):164:40:1; in this example, specifically, 1.26 g of pyromellitic dianhydride, 0.476 g of cobalt chloride hexahydrate, 2.46 g of urea, 0.6 g of ammonium chloride, and 15 mg of ammonium molybdate are converted into a mass ratio, and the ratio of ammonium molybdate is set to 1, placed in a muffle furnace, heated to 400 °C at a rate of 5 °C / min and calcined for 3 hours. After washing and drying, cobalt phthalocyanine (PCoPc) powder is obtained.

[0069] The comparison of the 120-minute degradation efficiency of BPA in Example 2 and Comparative Examples 6 and 7 is as Figure 6 shown; it can be seen from Figure 6 that in the boron-doped phthalocyanine structure, the use of the metal element Fe results in the maximum removal rate of pollutants in electrocatalysis, and it is significantly higher than that of copper phthalocyanine (PCuPc) and cobalt phthalocyanine (PCoPc) Example 6: A dual-cathode electrochemical oxidation system based on a boron-doped iron phthalocyanine composite cathode material. The difference between this example and Example 2 is that: the catalytic electrode used is different; in this example, during the preparation process, the mass ratio of PFePc (180 mg) to NaBH4 (30 mg) is 6:1, and other parameters are the same.

[0070] Example 7: A dual-cathode electrochemical oxidation system based on a boron-doped polyphthalocyanine iron composite cathode material. The difference between this example and Example 2 is that the catalytic electrode used is different; in this example, the mass ratio of PFePc (120 mg) to NaBH4 (90 mg) is 4:3 during the preparation of the catalytic electrode, and other parameters are the same.

[0071] Example 8: A dual-cathode electrochemical oxidation system based on a boron-doped polyphthalocyanine iron composite cathode material. The difference between this example and Example 2 is that the catalytic electrode used is different; in this example, the mass ratio of PFePc (105 mg) to NaBH4 (105 mg) is 1:1 during the preparation of the catalytic electrode, and other parameters are the same.

[0072] Example 9: A dual-cathode electrochemical oxidation system based on a boron-doped polyphthalocyanine iron composite cathode material. The difference between this example and Example 2 is that the catalytic electrode used is different; in this example, the mass ratio of PFePc (126 mg) to NaBH4 (84 mg) is 6:4 during the preparation of the catalytic electrode, and other parameters are the same.

[0073] Example 10: A dual-cathode electrochemical oxidation system based on a boron-doped polyphthalocyanine iron composite cathode material. The difference between this example and Example 2 is that the catalytic electrode used is different; in this example, the mass ratio of PFePc (140 mg) to NaBH4 (70 mg) is 6:3 during the preparation of the catalytic electrode, and other parameters are the same.

[0074] The comparison of the 120-minute degradation efficiency of BPA in Examples 2, 6, 7, 8, 9, and 10 is as Figure 7 shown; it can be seen from Figure 7 that in the boron-doped polyphthalocyanine structure, the catalytic electrode prepared under the condition of the mass ratio of PFePc to NaBH4 being (5 - 6):(2 - 4) has significant advantages in the dual-cathode electrochemical oxidation system.

[0075] The boron-doped polyphthalocyanine iron PFePc-B400 prepared in Example 1 was used five times cyclically in the dual-cathode electrochemical oxidation system provided in Example 2; the degradation effect is as Figure 9 shown. It can be seen from Figure 9 that the catalytic cathode still maintains more than 90% activity after five consecutive cycles, and no iron sludge is generated; it shows that the catalytic electrode with a three-dimensional porous structure prepared in Example 1 effectively inhibits the passivation of active sites and can improve the cyclic use performance.

Claims

1. A dual-cathode electrochemical oxidation system based on a boron-doped polyphthalocyanine iron composite cathode material, comprising a dual-chamber reactor, and an anode, a modified cathode, a catalytic cathode and an aeration head arranged in the dual-chamber reactor; the anode is connected to the positive pole of a DC power supply; the mutually spaced modified cathode and catalytic cathode are both connected to the negative pole of the DC power supply; and it is characterized in that: The modified cathode includes a substrate and carbon nanotubes loaded on the substrate; the catalytic cathode includes a substrate and iron boron-doped phthalocyanine loaded on the substrate; the aeration head supplies oxygen to the modified cathode; the modified cathode reacts to generate hydrogen peroxide; the catalytic cathode activates hydrogen peroxide to generate hydroxyl radicals for degrading organic pollutants.

2. The dual-cathode electrochemical oxidation system according to claim 1, wherein: The iron boron-doped phthalocyanine is obtained by mixing phthalocyanine iron with sodium borohydride and then calcining them, so that sodium borohydride is co-pyrolyzed, and boron atoms are embedded in the phthalocyanine iron skeleton in a substitution and / or interstitial form.

3. The dual-cathode electro-chemical oxidation system according to claim 2, wherein: The mass ratio of the phthalocyanine iron to the sodium borohydride is (5-6):(2-4).

4. The dual-cathode electrochemical oxidation system according to claim 3, wherein: The temperature for calcining after mixing phthalocyanine iron with sodium borohydride is greater than or equal to 300°C to 400°C.

5. The dual-cathode electro-chemical oxidation system according to claim 1, characterized in that: The phthalocyanine iron is obtained by mixing pyromellitic dianhydride, ferrous chloride tetrahydrate, urea, ammonium chloride, and ammonium molybdate in a mass ratio of (83-85):(26-28):(162-164):(40-42):1, grinding them, and then calcining.

6. The dual-cathode electrochemical oxidation system according to claim 1, wherein: The substrates of both the modified cathode and the catalytic cathode are made of carbon paper; the carbon nanotubes in the modified cathode are bonded to the surface of the carbon paper through a conductive binder; the iron boron-doped phthalocyanine in the modified cathode is bonded to the surface of the carbon paper through a conductive binder.

7. The dual-cathode electro-chemical oxidation system according to claim 1, wherein: The distance between the modified cathode and the catalytic cathode is 0.5 cm to 1 cm; the aeration head is arranged on the side of the modified cathode facing away from the catalytic cathode.

8. A dual-cathode electrochemical oxidation method for organic wastewater, characterized in that: Use the dual-cathode electrochemical oxidation system as described in claim 1; the method is as follows: the organic wastewater to be treated added with an electrolyte is introduced into the cathode reaction chamber of the dual-chamber reactor; a voltage is applied between the anode and the cathode through a DC power supply, and the modified cathode undergoes an electrolytic reaction to generate hydrogen peroxide; the catalytic cathode activates hydrogen peroxide to generate hydroxyl radicals; the hydroxyl radicals oxidize and degrade the organic pollutants in the organic wastewater.

9. The method according to claim 8, characterized in that: The potential applied by the DC power supply between the cathodes is 0.9 to 0.7 V vs. Ag / AgCl.

10. Application of a boron-doped iron polyphthalocyanine composite material as a catalytic electrode in a dual-cathode electrochemical oxidation system; characterized in that: The iron boron-doped phthalocyanine composite material is obtained by bonding iron boron-doped phthalocyanine to a substrate; the iron boron-doped phthalocyanine is obtained by mixing phthalocyanine iron with sodium borohydride and then calcining them, so that sodium borohydride is co-pyrolyzed, and boron atoms are embedded in the phthalocyanine iron skeleton in a substitution or interstitial form.

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