Preparation method and application of activated carbon filled modified cathode doped with carbon nitride and phthalocyanine iron

Abstract

The application discloses a preparation method and application of an activated carbon filled modified cathode of carbon nitride doped phthalocyanine iron. The modified cathode is loaded with a binary composite catalyst through immersion and integral calcination, and has the characteristics of simplicity, stability and high efficiency. The modified cathode can be applied to an electrocatalytic microbial fuel cell system to treat coking wastewater, and has the potential of producing H2O2 through electrocatalytic ORR. Experimental verification shows that the modified cathode can effectively degrade TOC, TN and COD in coking wastewater in a coupling system, and the direct effluent can reach the national first direct discharge standard, so that the modified cathode has the potential of industrial application.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment and energy utilization technology in water pollution control. It relates to the preparation of a packed modified cathode, FePc / g-C3N4 / AC, and its application in a photo / electrocatalytic microbial fuel cell coupling system for continuous multi-stage treatment of coking wastewater. This cathode can electrocatalyze the ORR reaction to produce H2O2, efficiently removing pollutants from the water. This provides ideas and references for developing efficient, simple, and industrially producible modified cathode catalysts. Background Technology

[0002] For microbial fuel cell systems, the choice of electrode materials is a key factor determining pollutant treatment efficiency. Excellent electrode materials should possess a large specific surface area for adsorbing recalcitrant organic pollutants and good conductivity for better electron transfer. Activated carbon particles not only have a large specific surface area and porosity, allowing anodic microorganisms to attach and grow well, but also possess excellent conductivity and are inexpensive and readily available. Compared to traditional metal electrodes, they can reduce costs and have potential for industrial applications. Furthermore, a major approach to improving MFC performance is to increase the cathode ORR reaction rate, increase the level of active material, and accelerate the oxidation of pollutants.

[0003] Among numerous semiconductor materials, graphitic carbon nitride (g-C3N4) is a polymer photocatalyst that has attracted considerable attention due to its non-toxicity, high-temperature stability, and low-cost precursor properties. It is suitable for emerging fields such as hydrogen production, carbon dioxide reduction, oxidation of harmful aromatic pollutants, photovoltaic solar cells, and the development of gas sensors. g-C3N4 exhibits high thermal stability, a flexible electronic structure, and good chemical stability in acids, alkalis, and organic solvents. Its mid-bandgap is approximately 2.7 eV, corresponding to the 460 nm visible light region. This suitable bandgap enables g-C3N4 to be active under visible light and provides a flexible channel for photoexcited electron migration. Therefore, g-C3N4 is considered a promising green photocatalyst and also an excellent support.

[0004] Metal-based phthalocyanine (Pc) compounds are promising electrode materials for cathode-catalyzed orthostatic regenerative braking (ORR). Compared to metal ions, metal phthalocyanines (MPcs) can effectively prevent metal ion leakage. Generally, metal-based (Fe, Co, Ni, etc.) Pc compounds have a central transition metal surrounded by four nitrogen atoms, which facilitates electron transfer between active sites. Among transition metals, iron phthalocyanine (FePc) is considered the most electrocatalyst active ORR catalyst. However, FePc molecules often form dimers or polymers. Due to their strong bonding, FePc is poorly soluble in water, reducing the number of active sites and affecting its catalytic performance. Therefore, loading FePc onto porous g-C3N4 not only enhances dispersion and prevents dimer formation, improving catalytic activity, but also reduces catalyst loss.

[0005] The composite catalyst was loaded onto activated carbon using a simple impregnation and calcination method and used as a modified packed cathode. This was applied to a microbial fuel cell system for the treatment of coking wastewater and the electrocatalytic ORR to produce H2O2. This not only effectively improved the system's treatment capacity but also explained the role of the catalyst from a principle perspective. Summary of the Invention

[0006] The purpose of this invention is to prepare a modified activated carbon-filled cathode doped with carbon nitride and ferrophthalocyanine, and to provide methods for its application in both the practical treatment of coking wastewater and the electrocatalytic ORR (Organic Oxygen Reduction) production of H2O2 in a photo / electrocatalytic microbial fuel cell coupling system. Addressing the problems of poor conductivity, slow ORR reaction, poor stability, and high cost of traditional cathode materials, activated carbon particles are selected as the carrier. Utilizing the excellent adsorption properties of activated carbon, g-C3N4 and FePc are loaded onto the activated carbon particles, disclosing a simple method for preparing the modified cathode. Furthermore, efficient treatment of coking wastewater is achieved, the working principle of the system is explained, and the effluent meets direct discharge standards, achieving compliant discharge.

[0007] The technical solution of this invention:

[0008] A method for preparing a carbon nitride-doped ferrophthalocyanine activated carbon-filled modified cathode, comprising the following steps:

[0009] (1) Acid activation pretreatment of activated carbon particles;

[0010] Furthermore, the acid activation pretreatment process includes: ultrasonic washing with deionized water, drying, acid solution activation impregnation, drying, ultrasonic washing with deionized water, and drying.

[0011] Furthermore, the ultrasonic washing with deionized water has an ultrasonic power of 80-100W and a duration of 2-4 hours.

[0012] Furthermore, the drying temperature is 60–80°C, and the drying time is 6–8 hours.

[0013] Furthermore, the acid solution is a nitric acid solution with a mass fraction of 15% to 20%.

[0014] Furthermore, the activation impregnation time is 8–10 hours.

[0015] (2) Preparation of Fe Pc / AC: Iron phthalocyanine was dissolved in anhydrous ethanol, and then loaded onto activated carbon particles after activation pretreatment by impregnation and drying to obtain dried iron phthalocyanine / activated carbon particles.

[0016] Furthermore, the mass fraction of Fe Pc relative to the activated carbon particles is 0.3–0.5 wt%.

[0017] Furthermore, an equal-volume impregnation method is used for 12–24 hours.

[0018] Furthermore, the drying temperature is 60–80°C, and the drying time is 6–8 hours.

[0019] (3) Preparation of Fe Pc / g-C3N4 / AC: Urea was dissolved in deionized water and impregnated onto phthalocyanine iron / activated carbon particles. After drying, it was calcined at high temperature in a muffle furnace to obtain activated carbon doped with carbon nitride and phthalocyanine iron.

[0020] Furthermore, the proportion of urea added is 3-5 wt% relative to ferric phthalocyanine / activated carbon particles.

[0021] Furthermore, an equal-volume impregnation method is used for 12–24 hours.

[0022] Furthermore, the drying temperature is 60–80°C, and the drying time is 6–8 hours.

[0023] Furthermore, the working temperature of the muffle furnace for calcination is 520–550℃, the heating rate is set to 2–5℃ / min, and the calcination time is 3–4h.

[0024] Application of a carbon nitride-doped ferrophthalocyanine activated carbon-filled modified cathode for electrocatalytic ORR production of H2O2.

[0025] An application of activated carbon-filled modified cathodes doped with carbon nitride and ferrocyanide is disclosed for constructing a photocatalytic / electrocatalytic microbial fuel cell coupled system (PEC / EC-MFC). The construction process of the PEC / EC-MFC system is as follows: the system has an upper and lower structure, with a cathode chamber at the top and an anode chamber at the bottom. An isolation layer exists between the anode and cathode chambers, consisting of two layers of filter cloth and sand filling the space between them. The coking wastewater operates with a bottom-in, top-out flow pattern. The anode chamber of the PEC / EC-MFC system is filled with activated carbon particles loaded with Shewanella electrogenic bacteria, and an aerator is used at the bottom to disperse the incoming water. The anode conductive material is a carbon rod, with one end connected to a wire and led outwards. A resistor, an ammeter, and the cathode material are connected in series. The cathode conductive material is also a carbon rod. The cathode chamber is filled with activated carbon doped with carbon nitride and ferrocyanide. A visible light source simulating sunlight is added above the cathode during PEC-MFC construction.

[0026] An application of a carbon nitride-doped ferrophthalocyanine activated carbon-filled modified cathode for constructing an electrocatalytic ORR system is disclosed. The construction of the electrocatalytic ORR system involves two electrolytic cells in a dual-cell electrolytic cell separated by an ion-exchange membrane. The anode electrolyte is a Na₂SO₄ solution, and the cathode electrolyte is also a Na₂SO₄ solution, or the cathode electrolyte is diluted coking wastewater with added Na₂SO₄. A carbon rod is used as the anode, and the prepared carbon nitride-doped ferrophthalocyanine activated carbon is used as the cathode material, connected to the anode via the carbon rod. The cathode material is placed in an insulating container, which is connected to the cathode electrolyte. Continuous aeration of the cathode ensures a continuous oxygen supply, and continuous ORR experiments are conducted in the constructed electrocatalytic ORR system.

[0027] The beneficial effects of this invention are:

[0028] (1) A method for preparing a packed modified cathode for a photo / electrocatalytic microbial fuel cell coupling system (PEC / EC-MFC) is provided, which can be mass-produced by simple impregnation and calcination. The activated carbon itself has excellent adsorption properties and is combined with the catalyst. After calcination, the activated carbon not only has a smooth surface and increased void structure, but also can be more stably and tightly combined with the catalyst material.

[0029] (2) Select inexpensive and readily available activated carbon particles as the cathode material carrier, and load g-C3N4 and Fe Pc, which are easy to prepare and have high performance, as catalyst materials.

[0030] (3) The material was applied to the PEC / EC-MFC coupling system, with a residence time of 10 h, and 50 mg / L of raw water was added. 2- Or 0.03-0.05mMCl -Under the specified conditions, coking wastewater can be effectively treated and meet the indirect discharge standard; after continuous optimization treatment with aeration, light, and PMS addition, it can meet the national Class I direct discharge standard; this confirms that the modified packed cathode has excellent catalytic performance and can improve the system's wastewater treatment capacity.

[0031] (4) The material was applied to the electrocatalytic ORR, and the product was hydrogen peroxide. In the continuous 2-hour experiment, the optimal H2O2 yield reached 62.8 mg / h / g. cat This indicates that in the PEC / EC-MFC system, the modified cathode can generate H2O2, which in turn produces ·OH to oxidize organic pollutants in coking wastewater. Attached Figure Description

[0032] Figure 1 These are data charts showing relevant indicators for the effluent from the two-stage EC-MFC system under raw water conditions; where a is the TOC stability chart; b is the TN stability chart; c is the COD stability chart; and d is the NH4 stability chart. + Stability plots; the horizontal axis of each plot is time (h) and the vertical axis is concentration (mg / L).

[0033] Figure 2 It contains 50mg / L 2- Figure 1 shows the relevant index data of the two-stage effluent from the EC-MFC system under the raw water conditions; where a is the TOC stability diagram; b is the TN stability diagram; c is the COD stability diagram; and d is the NH4 stability diagram. + Stability plots; the horizontal axis of each plot is time (h) and the vertical axis is concentration (mg / L).

[0034] Figure 3 The charts show the relevant index data of the effluent from the two-stage EC-MFC system under the condition of raw water containing 0.03 mMCl; where a is the TOC stability chart; b is the TN stability chart; c is the COD stability chart; and d is the NH4+ stability chart. + Stability plots; the horizontal axis of each plot is time (h) and the vertical axis is concentration (mg / L).

[0035] Figure 4 These are data graphs of relevant indicators in the effluent from PEC-MFC during a 4-day continuous experiment, where the light intensity was 50W and the PMS concentration was 0.1mol / L; a is the TOC stability graph; b is the TN stability graph; the horizontal axis of each graph represents time (d) and the vertical axis represents concentration (mg / L).

[0036] Figure 5 This is a graph showing the H2O2 yield of four comparative experiments on electrocatalytic ORR for H2O2 production. The horizontal axis represents time (min), and the vertical axis represents the H2O2 yield (mg / h / g). cat ).

[0037] Figure 6a This is a scanning electron microscope (SEM) image of activated carbon particles.

[0038] Figure 6b This is a scanning electron microscope (SEM) image of FePc / g-C3N4 / AC at the 10 μm scale.

[0039] Figure 6c This is a scanning electron microscope (SEM) image of FePc / g-C3N4 / AC at the 1μm scale.

[0040] Figure 6d This is a scanning electron microscope (SEM) image of FePc / g-C3N4 / AC at a scale of 500 nm.

[0041] Figure 7 These are X-ray photoelectron spectroscopy (XPS) spectra of Fe Pc / g-C3N4 / AC without calcination treatment; where a is the full spectrum; b is the C1s spectrum; c is the N1s spectrum; and d is the Fe 2p spectrum.

[0042] Figure 8 These are X-ray photoelectron spectroscopy (XPS) spectra of the modified cathode of FePc / g-C3N4 / AC; where a is the full spectrum; b is the C1s spectrum; c is the N1s spectrum; and d is the Fe 2p spectrum.

[0043] Figure 9 These are X-ray photoelectron spectroscopy (XPS) images of Fe Pc / g-C3N4 / AC after the coking wastewater has been treated by the system; where a is the full spectrum; b is the C1s spectrum; c is the N1s spectrum; and d is the Fe 2p spectrum. Detailed Implementation

[0044] The following description, in conjunction with the technical solutions and accompanying drawings, further illustrates specific embodiments of the present invention, but is not intended to limit the scope of protection of the present invention.

[0045] Example 1

[0046] 500g of granular activated carbon was placed in a 1000mL glass beaker, 1000mL of deionized water was added, and the mixture was ultrasonically washed and drained to minimize loss. This ultrasonic washing operation was repeated three times, with the solution becoming clear during the final wash. After washing, the carbon was dried in a forced-air drying oven to obtain activated carbon granules. An equal-volume impregnation method was used, adding sufficient 20% nitric acid solution and activating the carbon for 10 hours. The activated carbon support was then dried in a forced-air drying oven to obtain the acid-activated AC support. The ultrasonic washing operation was repeated three times to remove residual acid from the surface of the activated carbon support. The ultrasonically washed catalyst was then dried in a forced-air drying oven. The ultrasonic power for deionized water ultrasonic washing was 100W, and the time was 3 hours.

[0047] Weigh 1.5g of ferric phthalocyanate and use 500mL of anhydrous ethanol as a solvent. Stir thoroughly until the ferric phthalocyanate is completely dissolved and evenly dispersed. Weigh 500g of pretreated activated carbon granules and soak them in the ferric phthalocyanate solution. Soak for 24 hours and then dry them for later use.

[0048] Weigh 15g of urea and use 500mL of deionized water as a solvent, stirring thoroughly until the urea is completely dissolved. Soak 500g of FePc-loaded dry activated carbon granules in the urea solution for 12 hours and then dry them. Calcine the dried activated carbon granules in a muffle furnace at a high temperature of 520℃ for 4 hours at a heating rate of 5℃ / min. Dry all materials at 80℃ for 6 hours.

[0049] Example 2

[0050] 600g of granular activated carbon was placed in a 1000mL glass beaker, 1000mL of deionized water was added, and the mixture was ultrasonically washed and drained to minimize loss. This ultrasonic washing operation was repeated three times, with the solution becoming clear during the final wash. After washing, the carbon was dried in a forced-air drying oven to obtain activated carbon granules. An equal-volume impregnation method was used, adding sufficient 20% nitric acid solution and activating the carbon for 10 hours. The activated carbon support was then dried in a forced-air drying oven to obtain the acid-activated AC support. The ultrasonic washing operation was repeated three times to remove residual acid from the surface of the activated carbon support. The ultrasonically washed catalyst was then dried in a forced-air drying oven. The ultrasonic power for deionized water ultrasonic washing was 100W, and the time was 3 hours.

[0051] Weigh 2.4g of ferric phthalocyanate and use 600mL of anhydrous ethanol as a solvent. Stir thoroughly until the ferric phthalocyanate is completely dissolved and evenly dispersed. Weigh 600g of pretreated activated carbon granules and soak them in the ferric phthalocyanate solution. After soaking for 24 hours, dry them for later use.

[0052] Weigh 24g of urea and use 600mL of deionized water as a solvent, stirring thoroughly until the urea is completely dissolved. Soak 600g of FePc-loaded dry activated carbon granules in the urea solution for 12 hours and then dry them. Calcine the dried activated carbon granules in a muffle furnace at a high temperature of 520℃ for 4 hours at a heating rate of 5℃ / min. Dry all materials at 80℃ for 6 hours.

[0053] Example 3

[0054] 600g of granular activated carbon was placed in a 1000mL glass beaker, 1000mL of deionized water was added, and the mixture was ultrasonically washed and drained to minimize loss. This ultrasonic washing operation was repeated three times, with the solution becoming clear during the last wash. After washing, the carbon was dried in a forced-air drying oven to obtain activated carbon granules. An equal-volume impregnation method was used, adding sufficient 20% nitric acid solution and activating the carbon for 10 hours. The carbon was then dried in a forced-air drying oven to obtain the acid-activated AC support. The ultrasonic washing operation was repeated three times to remove residual acid from the surface of the activated carbon support. The ultrasonically washed catalyst was then dried in a forced-air drying oven. The ultrasonic washing with deionized water was performed at a power of 100W for 3 hours. 3.0g of ferric phthalocyanate was weighed and dissolved in 600mL of anhydrous ethanol. The mixture was stirred thoroughly until the ferric phthalocyanate was completely dissolved and uniformly dispersed. 600g of the pretreated activated carbon granules were weighed and soaked in the ferric phthalocyanate solution for 24 hours, then dried for later use.

[0055] Weigh 30g of urea and use 600mL of deionized water as a solvent, stirring thoroughly until the urea is completely dissolved. Soak 600g of FePc-loaded dry activated carbon granules in the urea solution for 12 hours and then dry them. Calcine the dried activated carbon granules in a muffle furnace at a high temperature of 520℃ for 4 hours at a heating rate of 5℃ / min. Dry all materials at 80℃ for 6 hours.

[0056] The FePc / g-C3N4 / AC modified cathode prepared as described in Example 1 was characterized by SEM and XPS tests, as well as in Examples 4-8. The aforementioned PEC / EC-MFC reaction system was constructed to treat coking wastewater. The wastewater flowed from the bottom inlet into the anode region filled with activated carbon loaded with Shevar electrogenic bacteria. After treatment by the anode microorganisms, it sequentially flowed into the sand isolation layer and then into the cathode region for further treatment. Examples 4-7 all utilized the above system.

[0057] Example 4

[0058] An electrocatalytic microbial fuel cell (EC-MFC) system was constructed, and the residence time of coking wastewater in the reaction system was controlled to be 10 hours. Sampling and testing were then conducted. Figure 1 a is the TOC data chart; b is the TN data chart; c is the NH4 data chart. + COD data graph; d is the COD data graph.

[0059] Example 5

[0060] The same system as in Example 4 was constructed, but 50 mg / L Na2S was added to the raw water as a supplementary carbon source. The residence time of the wastewater in the reaction system was controlled to be 10 hours, and samples were taken for testing. Figure 2 a is the TOC data chart; b is the TN data chart; c is the NH4 data chart. +Data chart; d is the COD data chart.

[0061] Example 6

[0062] The same system as in Example 4 was constructed, but 0.03 mM NaCl was added to the raw water, and the residence time of the wastewater in the reaction system was controlled to be 10 hours. Samples were then taken for testing. Figure 3 a is the TOC data chart; b is the TN data chart; c is the NH4 data chart. + Data chart; d is the COD data chart.

[0063] Example 7

[0064] A photocatalytic / electrocatalytic microbial fuel cell (PEC / EC-MFC) system was constructed. However, 50 mg / L Na2S was added to the raw coking wastewater as a supplementary carbon source. Subsequently, continuous testing was conducted on the system under various conditions, including aeration, light, and PMS, with daily sampling and monitoring of effluent changes. Figure 4 a) is the degradation stability diagram of TOC in coking wastewater; b) is the degradation stability diagram of TN in coking wastewater.

[0065] As can be seen from this example, after 4 days of continuous treatment, the TOC of the primary effluent has reached the national Class I direct discharge standard, and the TN of the secondary effluent has reached the national Class I direct discharge standard.

[0066] Example 8

[0067] Combination Figure 5 The above-mentioned electrocatalytic ORR system was constructed to conduct four sets of ORR reaction comparison experiments. The anolyte of all four sets of experiments was 0.5M Na2SO4 solution.

[0068] The first group of cathode electrolytes is 0.5M Na2SO4 solution, and the cathode material is FePc / g-C3N4 / AC;

[0069] The second set of cathode electrolytes consisted of coking wastewater diluted 20 times with 0.5M Na2SO4, and the cathode material was FePc / g-C3N4 / AC.

[0070] The third group of cathode electrolytes is 0.5M Na2SO4 solution, and the cathode material is pure activated carbon particles;

[0071] The fourth group of cathode electrolytes consisted of coking wastewater diluted 20 times with 0.5M Na2SO4, and the cathode material was pure activated carbon.

[0072] When the cathode electrolyte is a 0.5M Na2SO4 solution and the cathode material is FePc / g-C3N4 / AC, the system achieves the highest H2O2 yield, reaching 62.8 mg / h / g.cat .

[0073] This example shows that the hydrogen peroxide yield of pure activated carbon is extremely low, indicating that the modified cathode has the ability to electrocatalyze ORR to produce H2O2. When the modified cathode is used as the working electrode, the H2O2 yield is reduced when coking wastewater is used as the electrolyte, compared with 0.5M Na2SO4 solution as the electrolyte.

[0074] This embodiment verifies the principle of FePc / g-C3N4 / AC modified cathode working to treat coking wastewater. During the electrocatalytic process, H2O2 can be generated, thereby generating ·OH to oxidize organic pollutants in the coking wastewater.

[0075] SEM characterization test

[0076] As shown in Figure 6, SEM characterization tests were performed on untreated activated carbon and the prepared modified cathode. It can be observed that the surface of pure activated carbon is rough and exhibits irregular, lamellar, granular and sheet-like structures. The surface of the modified cathode material is smooth and has more regular pore structures, which provide more attachment sites for the catalyst, contribute more reactive sites, and can accelerate the reaction process.

[0077] XPS characterization test

[0078] X-ray photoelectron spectroscopy characterization was performed on Fe Pc / g-C3N4 / AC before calcination, after calcination, and after reaction. The total spectra of the three materials all showed the presence of four elements: C, N, O, and Fe, which is consistent with the composite catalyst. Figure 7 In the diagram, b is the high-resolution spectrum of C1s, showing three peaks at 283.6 eV, 284.8 eV, and 289.7 eV. These peaks represent CC bonds (sp2), the CC / C=C bonds of the amorphous carbon and phthalocyanine rings adsorbed by the instrument, and the typical sp2 carbon of g-C3N4 (NC=N), respectively. c is the high-resolution spectrum of N1s, showing three peaks at 398.8 eV, 400.2 eV, and 401.6 eV, which belong to amino N (N-hx), interatomic bridging and pyrrole interaction, and sp2 hybridization (C=NC), respectively. d is the high-resolution spectrum of Fe 2p. Although the Fe content is low, the Fe 2p spectrum clearly shows four peaks convolved at 708.3 eV, 712.1 eV, 721.8 eV, and 724.7 eV, which are attributed to Fe. 2+ 2p 3 / 2 Fe 3+ 2p 3 / 2 ,Fe 2+ 2p 1 / 2 and Fe 3+ 2p 1 / 2This indicates that Fe in the catalyst 2+ and Fe 3+ The coexistence confirms the formation of aromatic nitrogen-coordinated Fe(III) during the ammonia separation process of urea.

[0079] and Figure 7 compared to, Figure 8 This is the XPS spectrum of FePc / g-C3N4 / AC without calcination treatment. Figure 8 In the middle, no characteristic peaks of g-C3N4 were observed in spectra b and c, indicating that g-C3N4 had not formed in the material at this time.

[0080] and Figure 7 compared to, Figure 9 This is the XPS spectrum of FePc / g-C3N4 / AC after wastewater treatment in the reactor. Figure 9 In the c and d spectra, differences can be observed. Figure 7 The characteristic Fe-N coordination peaks in the c and d spectra indicate that the reaction caused changes in the Fe-N vibration related to pyridine-N, resulting in changes in the peak values.

Claims

1. A method for preparing a carbon nitride-doped ferrophthalocyanine activated carbon-filled modified cathode, characterized in that, The steps are as follows: (1) Acid activation pretreatment of activated carbon particles; (2) Preparation of Fe Pc / AC: Ferric phthalocyanine was dissolved in anhydrous ethanol and impregnated onto pre-treated activated carbon particles, which were then dried to obtain dried ferric phthalocyanine / activated carbon particles; the mass fraction of Fe Pc relative to the activated carbon particles was 0.3~0.5 wt%; (3) Preparation of Fe Pc / g-C3N4 / AC: Urea was dissolved in deionized water and impregnated onto phthalocyanine iron / activated carbon particles. After drying, it was calcined at high temperature in a muffle furnace to obtain activated carbon doped with carbon nitride and phthalocyanine iron.

2. The method for preparing a carbon nitride-doped ferrophthalocyanine activated carbon-filled modified cathode according to claim 1, characterized in that, In step (1), the acid activation pretreatment process includes: ultrasonic washing with deionized water, drying, acid solution activation and impregnation, drying, ultrasonic washing with deionized water, and drying.

3. The method for preparing a carbon nitride-doped ferrophthalocyanine activated carbon-filled modified cathode according to claim 2, characterized in that, In step (1), the ultrasonic power of the deionized water ultrasonic washing is 80~100W, and the time is 2~4h; the drying temperature is 60~80℃, and the time is 6~8h; the acid solution is a nitric acid solution with a mass fraction of 15%~20%; and the activation immersion time is 8~10h.

4. The method for preparing a carbon nitride-doped ferrophthalocyanine activated carbon-filled modified cathode according to claim 1, characterized in that, In step (2), the equal volume impregnation method is used for 12-24 hours; the drying temperature is 60-80℃ and the drying time is 6-8 hours.

5. The method for preparing a carbon nitride-doped ferrophthalocyanine activated carbon-filled modified cathode according to claim 1, characterized in that, In step (3), the proportion of urea added is 3~5wt% relative to ferric phthalocyanate / activated carbon particles; the equal volume impregnation method is used for 12~24h; the drying temperature is 60~80℃ and the drying time is 6~8h.

6. The method for preparing a carbon nitride-doped ferrophthalocyanine activated carbon-filled modified cathode according to claim 1, characterized in that, In step (3), the working temperature of the muffle furnace for calcination is 520~550℃, the heating rate is set to 2~5℃ / min, and the calcination time is 3~4h.

7. The application of the activated carbon-filled modified cathode doped with carbon nitride-based ferrocyanide as described in any one of claims 1-6, characterized in that, Used for electrocatalytic ORR to produce H2O2.

8. The application of the activated carbon-filled modified cathode doped with carbon nitride-based ferrocyanide as described in claim 7, characterized in that, The PEC / EC-MFC system was used to construct a photo / electrocatalytic microbial fuel cell coupling system. The construction process of the PEC / EC-MFC system is as follows: The system has a vertical structure, with the upper part being the cathode chamber and the lower part being the anode chamber. An isolation layer exists between the anode and cathode chambers, consisting of two layers of filter cloth and sand filling the space between them. The coking wastewater operates with a bottom-in, top-out flow pattern. The anode chamber of the PEC / EC-MFC system is filled with activated carbon particles loaded with Shewanella electrogenic bacteria, and the bottom uses an aerator to disperse the incoming water. The anode conductive material is a carbon rod, with one end connected to a wire and led outwards. A resistor, ammeter, and cathode material are connected in series, and the cathode conductive material is also a carbon rod. The cathode chamber is filled with activated carbon doped with carbon nitride and ferrocyanide. A visible light source simulating sunlight is added above the cathode during the construction of the PEC-MFC.

9. The application of the activated carbon-filled modified cathode doped with carbon nitride-based ferrocyanide as described in claim 7, characterized in that, To construct an electrocatalytic ORR system, the two electrolytic cells of a dual-cell electrolytic cell are separated by an ion-exchange membrane. The anode electrolyte is a Na2SO4 solution, and the cathode electrolyte is also a Na2SO4 solution, or the cathode electrolyte is diluted coking wastewater with added Na2SO4. A carbon rod is used as the anode, and activated carbon doped with phthalocyanine iron is used as the cathode material. The cathode is connected to the anode via the carbon rod. The cathode material is placed in an insulating container, which is connected to the cathode electrolyte. Continuous aeration of the cathode ensures a continuous oxygen supply. Continuous ORR experiments are conducted in the constructed electrocatalytic ORR system.

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