Carbon composite electrocatalytic material and preparation method thereof, and carbon composite electrocatalytic electrode and preparation method thereof

Abstract

The application discloses a kind of carbon complex electrocatalytic material, its preparation method and the matching electrocatalytic electrode and preparation method.The present application uses worm-like expanded graphite as carrier, sequentially through titanium component preloading, aniline nitrogen doping, multiple strong acid intercalation condensation etching, titanium tetrachloride controllable hydrolysis covalent anchoring TiO2, between carbon base and titanium dioxide, construct stable Ti-O-C covalent bond, simultaneously introduce rutile / anatase mixed crystal titanium active site and nitrogen-doped site;Whole matching alcohol solvent closed loop recovery, acidic mother liquor resource recovery process, reduce three wastes and production cost.The material of the present application has lower Tafel slope, smaller charge transfer impedance, stable potential during long-time electrolysis at constant current, TiO2 is in combined state, not easy to fall off, and the catalytic activity of oxidation, reduction, polymerization and degradation and the cycle life are significantly better than those of traditional EG-PAN-TiO2, suitable for oil and gas comprehensive waste liquid and other oil-containing organic waste liquid electrocatalytic degradation and other industrialization scenarios.

Description

Technical Field

[0001] This invention relates to a carbon composite electrocatalytic material and its preparation method, as well as a carbon composite electrocatalytic electrode and its preparation method, belonging to the field of electrochemical technology. Background Technology

[0002] Titanium dioxide-based electrocatalytic materials possess advantages such as strong chemical stability, environmental friendliness, and low cost, making them the mainstream active component in electrocatalysis. Graphite carbon materials exhibit excellent conductivity and controllable pore structure, often serving as catalytic supports. Polyaniline-modified expanded graphite supported titanium dioxide composite electrocatalytic materials (EG-PAN-TiO2) represent a novel type of carbon-based TiO2 electrocatalytic material. Existing preparation methods typically involve purchasing commercially available expanded graphite powder, utilizing aniline for single-adsorption polymerization to form a polyaniline thin layer on the graphite surface, then loading TiO2 via a tetrabutyl titanate sol-gel method, followed by high-temperature calcination to obtain a carbon / titanium dioxide crystal composite material.

[0003] Existing technologies have many inherent flaws:

[0004] Commercial expanded graphite, after being crushed and stored for a long time, suffers severe damage to its graphite sheets and lacks oxygen-containing functional groups on its surface. TiO2 is physically coated on the carbon surface only by intermolecular forces formed by the polyaniline carbonization layer. There is a lack of chemical bonding between the carbon substrate and TiO2. During electrocatalysis, electrolyte erosion and continuous scouring by electrolytic bubbles will cause titanium dioxide nanoparticles to fall off, resulting in poor long-term cycle stability of the catalyst.

[0005] Without high-temperature expansion and deep etching, the graphite is densely layered, making it difficult for titanium precursors to penetrate between layers, resulting in uneven distribution of active components.

[0006] Aniline is only polymerized and modified on the outer surface of graphite in a single step, and cannot penetrate into the interlayer of graphite, resulting in a limited number of modification sites. At the same time, the expanded graphite powder has an extremely loose texture and a very low bulk density, making solid-liquid separation difficult. The sol-gel process requires a long period of standing to form a gel, which is only suitable for small-scale laboratory tests and is difficult to scale up industrially.

[0007] The product is mainly composed of single-phase anatase titanium dioxide, with a single type of catalytic active site; lacking nitrogen doping modification, the intrinsic electrocatalytic active sites are insufficient; the hydrolysis rate of tetrabutyl titanate is difficult to control precisely, and titanium dioxide particles are prone to agglomeration, reducing the effective catalytic specific surface area.

[0008] The molded electrode lacks a gradient substrate structure, resulting in poor electrolyte penetration and low overall catalytic efficiency.

[0009] The process lacks a solvent recovery system, resulting in the consumption of large quantities of organic solvents such as ethanol, the generation of large amounts of waste, and high production costs.

[0010] Therefore, there is an urgent need to develop a novel process for preparing carbon composite electrocatalytic materials to solve technical problems such as weak interfacial bonding, poor catalyst stability, and difficulty in large-scale production. Summary of the Invention

[0011] To address the shortcomings of existing technologies, this invention provides a novel preparation process that solves technical problems such as catalytic component shedding, insufficient active sites, large raw material loss, and poor electrode mass transfer by high-temperature expansion and layering, graded acidic preloading, aniline nitrogen doping, deep etching of multi-component acids, covalent anchoring of titanium tetrachloride molecules, and gradient hot pressing to form electrodes.

[0012] This invention provides a method for preparing a carbon composite electrocatalytic material, comprising the following steps:

[0013] Step 1, Material preparation and expansion process: Preheat the electric heating furnace to 700-750℃, take 260kg of expandable graphite raw material with a purity of 99.8%, feed it into the electric heating furnace in a closed negative pressure environment, continue heating in the furnace to 800-850℃, keep the temperature constant for 15s, and the graphite volume expands by 260-480 times to obtain worm-shaped expanded graphite;

[0014] Step 2, Volume Reduction and Preloading Process: 260 kg of worm-shaped expanded graphite is transferred to a mixing vessel, along with 9480 kg of a mixture of anhydrous ethanol and n-propanol (volume ratio 1:0.4) and 2.6 kg of rutile powder pretreated with 8.5 kg of 98% concentrated sulfuric acid. The mixture is stirred and suspended to complete the preloading of the titanium component. The mixture is then subjected to solid-liquid separation using a variable-speed centrifugal filter (1500-3000 rpm). The solid filter cake proceeds to the next process, while the liquid phase, the ethanol-n-propanol mixture, is discharged into an ethanol-n-propanol recovery tank for direct recycling.

[0015] In this process, concentrated sulfuric acid dissociates to release H+. + HSO4 - Embedded in the interlayer gaps of expanded graphite sheets, the electrostatic repulsion opens up the graphite interlayer structure, forming a loading channel. Simultaneously, a strongly acidic system is constructed to activate the graphite edge sites, inhibiting titanium dioxide hydrolysis and agglomeration, and improving material mixing and mass transfer efficiency. Anhydrous ethanol and n-propanol in a 1:0.4 mixture are low-polarity organic solvents that do not react violently with concentrated sulfuric acid. This mixture can serve as a two-phase dispersion medium, reducing solid-liquid interfacial tension, uniformly wetting graphite and rutile powders, and preventing powder agglomeration. Ethanol has low viscosity, and the wetting effect of n-propanol helps to uniformly adhere rutile powder to the graphite sheet surface, preventing titanium dioxide agglomeration. As the core active component for electrocatalysis in this project, it is uniformly adsorbed inside and outside the graphite sheets through hydrogen bonds in the acidic alcohol system, completing pre-loading. It also provides physical support for the particles embedded in the interlayer, preventing graphite sheets from re-stacking and providing a composite precursor for subsequent molecular anchoring and high-temperature pyrolysis.

[0016] Step 3, Volume Reduction Nitrogen Doping Process: The volume-reduced solid filter cake is fed into a reactor, and 9480 kg of a mixture of anhydrous ethanol and n-propanol at a volume ratio of 1:0.4, along with 8.5 kg of 98% concentrated sulfuric acid to prepare an acidic system, are added. 4740 kg of 99.9% pure aniline at 0℃ is then slowly added. After stirring and reacting, the material is fed into a variable-speed centrifugal filter (1500-3000 rpm) for solid-liquid separation. The material is washed with a mixture of anhydrous ethanol and n-propanol at a volume ratio of 1:0.4. The mixed mother liquor of ethanol, n-propanol, and aniline is recycled. The filter cake is dried under a slightly negative pressure environment to remove ethanol and n-propanol, becoming a volume-reduced nitrogen-doped graphite-supported material. The volatilized gaseous ethanol and n-propanol are condensed and recovered.

[0017] In this process, concentrated sulfuric acid acts as an acidic catalyst to protonate aniline, enhancing the complexation reaction activity between aniline and graphite (aniline is an aromatic amine that undergoes a weak acid-base protonation reaction under weak acid conditions, producing aniline hydrogen sulfate. Positively charged aniline ions significantly increase reactivity, enabling it to combine with oxygen-containing groups on the graphite surface); maintaining a weakly acidic environment prevents the hydrolysis and shedding of pre-loaded rutile powder, balances the interlayer charge of graphite, and stabilizes the sheet structure. A 1:0.4 mixture of anhydrous ethanol and n-propanol serves as a two-phase dispersion solvent, improving the mixing uniformity of graphite, rutile, and aniline, reducing system viscosity, and promoting aniline penetration. Aniline is the core modifying agent in this process; under sulfuric acid catalysis, it covalently complexes with oxygen-containing sites in the graphite sheets, shrinking the interlayer spacing and physically encapsulating and locking the titanium catalytic components; simultaneously, nitrogen is introduced to provide nitrogen-doped active sites for subsequent electrocatalytic materials.

[0018] Step 4, Condensation Process: The nitrogen-doped graphite-loaded material is added to a mixing vessel, and 3000 kg of distilled water, 800 kg of 31% hydrochloric acid, 120 kg of 98% concentrated sulfuric acid, and 50 kg of ammonium persulfate are added sequentially to form a condensation mother liquor. The temperature is controlled at 0℃ to complete the graphite intercalation condensation. The solid-liquid separation is completed by centrifugation at 6000 rpm. The condensation mother liquor is recycled 3 times and then sent to a triple-effect evaporator to crystallize and recover ammonium sulfate. The remaining concentrated condensation mother liquor is disposed of as hazardous waste. The solid filter cake is dried under slight negative pressure to form the graphite condensation-loaded material.

[0019] In this process, concentrated sulfuric acid is used for secondary intercalation to expand the graphite sheets that have shrunk after volume reduction, opening up internal reaction channels; a strongly acidic environment is created to stabilize the titanium component and prevent it from hydrolyzing and falling off, slowly destroying the aniline coating layer on the graphite surface and exposing a large number of oxygen-containing reaction sites. 31% hydrochloric acid provides chloride ions to dissolve trace metal impurities such as iron and aluminum in the graphite raw material, generating soluble chlorides, which are separated with the mother liquor by centrifugation; a small amount of chloride ions enter the interlayer to balance the charge and improve the penetration effect of the modifier; the acidic system continuously etches the carbon sites at the graphite edges, expanding and widening the interlayer gaps, peeling the thick graphite into a thin carbon substrate; simultaneously, amorphous carbon and mineral impurities on the graphite surface are decomposed and removed, completing the purification of the substrate. Ammonium persulfate, as the core modifier, decomposes under acidic conditions to generate sulfate radicals, which deeply etch inert carbon sites inside graphite and generate a large number of carboxyl and hydroxyl groups, providing key binding sites for the covalent anchoring of tetrabutyl titanate in the subsequent bonding process; at the same time, it decomposes a small amount of free aniline, shrinks the graphite intercalation, and fixes the trace amount of aniline inside the intercalation to the graphite surface.

[0020] Step 5, Titanium Source Molecular Anchoring and Bonding Process: 430 kg of graphite condensation-loaded material is added to a mixing vessel, along with a mixture of anhydrous ethanol and n-propanol (volume ratio 1:0.4), 26 kg of rutile powder, 130 kg of titanium tetrachloride, 100 kg of 98% concentrated sulfuric acid, and 123 kg of 65% nitric acid. The system temperature is 120℃, and the pressure is 2 kg / cm². 2 After maintaining the temperature for 1.5 hours, titanium tetrachloride undergoes controlled hydrolysis in an acidic alcohol system, forming Ti-OC covalent bonds with oxygen-containing groups on the graphite surface through dehydration. After natural cooling, the material is removed, dried under negative pressure, and then calcined at 650°C for 2 hours in an electric baking oven to obtain 500 kg of carbon composite electrocatalytic material.

[0021] In this process, titanium tetrachloride serves as the core molecular anchoring titanium source, undergoing controlled hydrolysis to generate a nano-titanium dioxide precursor. This precursor is slowly hydrolyzed in an acidic ethanol system to produce amorphous hydrated titanium oxide. Numerous -COOH and -OH groups on the graphite surface undergo dehydration condensation with the hydrated titanium oxide, forming stable Ti-OC covalent bonds. This firmly grafts the titanium-based catalytic component onto the carbon framework, unlike simple physical mixing, ensuring it does not detach during electrocatalytic use. The nano-titanium precursor is uniformly distributed within the graphite layer, providing a high density of electrocatalytic active sites. Under electrocatalytic conditions, the titanium catalytic component does not detach, significantly extending electrode lifespan.

[0022] Preferably, the density of the expanded graphite after expansion in step 1 is 0.002-0.004 g / cm³. 3 .

[0023] Preferably, the drying temperature in step 3 is 60-65℃.

[0024] Preferably, in step 4, the evaporation temperature of the triple-effect evaporator is 95-102℃, and the filter cake is sent to a steam-heated negative pressure dryer at a drying temperature of 90℃.

[0025] Preferably, the ratio of distilled water, 31% hydrochloric acid, 98% concentrated sulfuric acid, and ammonium persulfate in the condensation mother liquor in step 4 is 300:80:12:5.

[0026] Preferably, the drying temperature in step 5 is 65°C.

[0027] Preferably, in each step, the ethanol-n-propanol mother liquor generated by centrifugation is uniformly recovered to the ethanol-n-propanol recovery tank for condensation and recycling, and can be directly reused without distillation.

[0028] The present invention also provides a carbon composite electrocatalytic material, which is prepared by the above-described preparation method.

[0029] The present invention also provides a carbon composite electrocatalytic electrode, comprising a substrate and a catalytic composite layer; the substrate is a cold-pressed plate formed by thoroughly mixing worm-shaped expanded graphite obtained by expansion treatment with thermoplastic PVDF nano-sized resin powder and thermoplastic PBT nano-sized resin powder in a mass ratio of 92:4:4; the catalytic composite layer is a powder layer formed by thoroughly mixing the carbon composite electrocatalytic material of claim 8 with thermoplastic PVDF nano-sized resin powder and thermoplastic PBT nano-sized resin powder in a mass ratio of 92:4:4.

[0030] This invention also provides a method for preparing a carbon composite electrocatalytic electrode, comprising the following steps:

[0031] Step 1: Stack the above-mentioned substrate and the above-mentioned catalytic composite layer in a mold of a hot press;

[0032] Step 2: Hot-press and hold at 160-180℃ and 35MPa for 1 hour, then cool for 1 hour. After demolding, the carbon composite electrocatalytic electrode is obtained.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] 1. The expandable graphite used in this invention is formed by sulfuric acid oxidation and intercalation of natural flake graphite. Sulfate-based intercalation substances are sealed between the carbon layers. When the graphite is fed into a high-temperature expansion furnace and heated instantaneously, the intercalation substances rapidly vaporize and decompose, generating a large amount of gas. This creates enormous internal pressure between the graphite flakes, forcing the graphite carbon layers apart and causing an instantaneous volume expansion of approximately 260-480 times, forming a porous, worm-like expanded graphite with a significantly increased specific surface area. The density of the expanded graphite is approximately 0.002-0.004 g / cm³. 3The increased interlayer spacing, continuous layers, and abundant pores of graphite facilitate the intercalation of strong acids and titanium-based catalysts, providing ample reaction sites for intercalation dispersion and surface modification with sufficient oxygen-containing functional groups. In contrast, ordinary commercially available expanded graphite powder suffers from edge structure damage and strong surface inertness due to storage, transportation, and crushing.

[0035] 2. In the volume reduction and preloading process, concentrated sulfuric acid dissociates into H+. + HSO4 - Embedded in the interlayer gaps of expanded graphite sheets, the electrostatic repulsion opens up the graphite interlayer structure, forming a loading channel. Simultaneously, a strongly acidic system is constructed to activate the graphite edge sites, inhibiting titanium dioxide hydrolysis and agglomeration, and improving material mixing and mass transfer efficiency. Anhydrous ethanol and n-propanol in a 1:0.4 mixture are low-polarity organic solvents that do not react violently with concentrated sulfuric acid. This mixture can serve as a two-phase dispersion medium, reducing solid-liquid interfacial tension, uniformly wetting graphite and rutile powders, and preventing powder agglomeration. Ethanol has low viscosity, and the wetting effect of n-propanol helps to uniformly adhere rutile powder to the graphite sheet surface, preventing titanium dioxide agglomeration. As the core active component for electrocatalysis in this project, it is uniformly adsorbed inside and outside the graphite sheets through hydrogen bonds in the acidic alcohol system, completing pre-loading. It also provides physical support for the particles embedded in the interlayer, preventing graphite sheets from re-stacking and providing a composite precursor for subsequent molecular anchoring and high-temperature pyrolysis.

[0036] 3. In the nitrogen doping process, concentrated sulfuric acid acts as an acidic catalyst to protonate aniline, enhancing the complexation reaction activity between aniline and graphite (aniline is an aromatic amine, undergoing a weak acid-base protonation reaction under weak acid conditions, producing aniline hydrogen sulfate. Positively charged aniline ions significantly increase reactivity, enabling it to bind with oxygen-containing groups on the graphite surface); maintaining a weakly acidic environment prevents the hydrolysis and shedding of pre-loaded rutile powder, balances the interlayer charge of graphite, and stabilizes the sheet structure. A 1:0.4 mixture of anhydrous ethanol and n-propanol serves as a two-phase dispersion solvent, improving the mixing uniformity of graphite, rutile, and aniline, reducing system viscosity, and promoting aniline penetration. Aniline is the core modifying agent in this process; under sulfuric acid catalysis, it covalently complexes with oxygen-containing sites in the graphite sheets, shrinking the interlayer spacing and physically encapsulating and locking the titanium catalytic components; simultaneously, nitrogen is introduced, providing nitrogen-doped active sites for subsequent electrocatalytic materials.

[0037] 4. In the graphite modification process, concentrated sulfuric acid is used for secondary intercalation to expand the graphite sheets that have shrunk after volume reduction, opening up internal reaction channels; a strongly acidic environment is created to stabilize the titanium component and prevent it from hydrolyzing and falling off, slowly destroying the aniline coating layer on the graphite surface and exposing a large number of oxygen-containing reaction sites. 31% hydrochloric acid provides chloride ions to dissolve trace metal impurities such as iron and aluminum in the graphite raw material, generating soluble chlorides, which are separated with the mother liquor by centrifugation; a small amount of chloride ions enter the interlayer to balance the charge and improve the penetration effect of the modifier; the acidic system continuously etches the carbon sites at the graphite edge, expanding and widening the interlayer gaps, peeling the thick graphite into a thin carbon substrate; simultaneously decomposes and removes amorphous carbon and mineral impurities from the graphite surface, completing the purification of the substrate. Ammonium persulfate, as the core modifier, decomposes under acidic conditions to generate sulfate radicals, which deeply etch inert carbon sites inside graphite and generate a large number of carboxyl and hydroxyl groups, providing key binding sites for the covalent anchoring of titanium tetrachloride in subsequent bonding processes; at the same time, it decomposes a small amount of free aniline, shrinks the graphite intercalation, and fixes the trace amount of aniline inside the intercalation to the graphite surface.

[0038] 5. In the prior art, aniline is adsorbed and polymerized in one step, forming a thin polyaniline layer only on the outer surface of graphite, and the graphite interlayer cannot be effectively modified; in the present invention, aniline reacts in two stages: the first stage: wetting worm graphite to achieve pre-modification, shrinkage, and preliminary nitrogen doping of the sheets; the second stage: oxidative polymerization in an acidic system, polyaniline penetrates into the graphite interlayer, and the inner and outer surfaces are modified simultaneously, providing a large number of hydroxyl and amino anchoring sites.

[0039] 6. A revolutionary improvement in the titanium loading mechanism during the titanium source molecular anchoring process: upgrading from "physical coating" to "covalent bond anchoring". In existing technologies, the PAN carbonization layer is merely an "intermediate buffer layer," with TiO2 particles attached to the carbon surface and bound by electrostatic forces between crystalline microparticles. During long-term electrocatalysis, electrolyte scouring, bubble disturbance, and volume stress can cause TiO2 nanoparticles to detach, leading to rapid catalyst decay. In this invention, titanium tetrachloride serves as the core molecular anchoring titanium source, controllably hydrolyzing to generate nano-titanium dioxide precursors. These precursors are slowly hydrolyzed in an acidic ethanol system to generate amorphous hydrated titanium oxide. Numerous -COOH and -OH groups on the graphite surface undergo dehydration condensation with the hydrated titanium oxide, forming stable Ti-OC covalent bonds, firmly grafting the titanium-based catalytic component onto the carbon framework. Unlike simple physical mixing, this method prevents detachment during electrocatalysis. The nano-titanium precursors are uniformly distributed within the graphite layer, providing a high density of electrocatalytic active sites. Under electrocatalytic conditions, the titanium catalytic components do not detach, significantly extending the electrode's lifespan. Simultaneously, rutile is introduced as a rigid framework to inhibit the sintering and agglomeration of TiO2 nanoparticles.

[0040] 7. The catalyst of this patent is modified by multi-level layer expansion, resulting in high density of active sites: high-temperature expansion layer expansion + deep etching with multi-component strong acid, graphite is exfoliated into thin carbon layers, and a large number of oxygen-containing sites are superimposed with nitrogen-doped sites inside and outside the layers, which significantly improves the catalytic reaction efficiency.

[0041] 8. Closed-loop recycling of raw materials, economical and environmentally friendly: Ethanol is recycled throughout the entire process without the need for distillation; the acidic mother liquor is recycled three times and then evaporated to recover ammonium sulfate byproducts, reducing hazardous waste and lowering production costs.

[0042] 9. Gradient electrode structure with high mass transfer efficiency: The expanded graphite cold-pressed plate substrate forms a continuous electrolysis channel for the electrolyte, and the hot-pressed catalytic layer has both high catalytic activity and mechanical strength, making it suitable for industrial continuous electrocatalytic equipment.

[0043] 10. High purity of substrate: Hydrochloric acid removes metallic impurities from graphite raw materials, eliminating the interference of impurities on electrocatalytic reactions.

[0044] 11. The cathode made with the carbon composite electrocatalytic material of the present invention has an oleophobic surface, is resistant to waste liquid with high oil content, and will not have any oil solidify on the electrode surface to contaminate the electrode. The electrode surface does not form scale, is resistant to high hardness petroleum waste liquid, and has an extended service life.

[0045] 12. The cathode made of the carbon composite electrocatalytic material of the present invention is used for oxidation, which has low voltage, no hydrogen, oxygen or chlorine gas is released, safe operation, low current density and energy saving.

[0046] 13. The cathode made using the carbon composite electrocatalytic material of the present invention has its cathode oxidation coupled in situ with the bottom of the nanobubbles, which significantly improves the efficiency of demulsification, oil removal and degradation of organic matter. Attached Figure Description

[0047] Figure 1 HER linear scan LSV curves of samples S1 (Scheme 1) and S2 (Scheme 2)

[0048] Figure 2 Tafel slope fitting curves for samples S1 and S2

[0049] Figure 3 Electrochemical impedance spectroscopy (EIS) Nyquist plots of samples S1 and S2

[0050] Figure 4 Long-term cycling stability curves of constant current (it) for samples S1 and S2

[0051] Figure 5 XRD diffraction patterns of samples S1 and S2

[0052] Figure 6 XPS high-resolution Ti 2p spectrum of sample S1

[0053] Figure 7 XPS high-resolution Ti 2p spectrum of sample S2

[0054] Figure 8 TEM morphology comparison image

[0055] Figure 9 Cathode plate product photos

[0056] Figure 10 Photos of other types of cathode products Detailed Implementation

[0057] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0058] Example 1 (corresponding to scheme S1 in the attached figure)

[0059] A method for preparing a carbon composite electrocatalytic material includes the following steps:

[0060] Step 1, Material preparation and expansion process: Preheat the electric heating furnace to 700-750℃, take 260kg of expandable graphite raw material with a purity of 99.8%, feed it into the electric heating furnace in a closed negative pressure environment, continue heating in the furnace to 800-850℃, keep the temperature constant for 15s, and the graphite volume expands by 260-480 times to obtain worm-shaped expanded graphite;

[0061] Step 2, Volume Reduction and Preloading Process: 260 kg of worm-shaped expanded graphite is transferred into a mixing vessel, and 9480 kg of anhydrous ethanol and n-propanol mixture at a volume ratio of 1:0.4 and 2.6 kg of rutile powder pretreated with 8.5 kg of 98% concentrated sulfuric acid are added. The mixture is stirred and suspended to complete the preloading of the titanium component. The mixture is then separated into solid and liquid phases using a variable speed centrifugal filter (1500-3000 rpm). The solid filter cake is sent to the next process, while the liquid phase ethanol-n-propanol mixture is discharged into an ethanol-n-propanol recovery tank for direct recycling.

[0062] Step 3, Volume Reduction Nitrogen Doping Process: The volume-reduced solid filter cake is fed into a reactor, and 9480 kg of a mixture of anhydrous ethanol and n-propanol at a volume ratio of 1:0.4 is added. 8.5 kg of 98% concentrated sulfuric acid is added to prepare an acidic system, and 4740 kg of 99.9% pure aniline at 0℃ is slowly added. After stirring and reacting, the material is fed into a variable speed centrifugal filter (1500-3000 rpm) for solid-liquid separation. The material is washed with a mixture of anhydrous ethanol and n-propanol at a volume ratio of 1:0.4. The mixed mother liquor of ethanol, n-propanol, and aniline is recycled. The filter cake is dried under a slight negative pressure environment to remove ethanol and n-propanol, becoming a volume reduction nitrogen-doped graphite-supported material. The volatilized gaseous ethanol and n-propanol are condensed and recovered.

[0063] Step 4, Condensation Process: The nitrogen-doped graphite-loaded material is added to a mixing vessel, and 3000 kg of distilled water, 800 kg of 31% hydrochloric acid, 120 kg of 98% concentrated sulfuric acid, and 50 kg of ammonium persulfate are added sequentially to form a condensation mother liquor. The temperature is controlled at 0℃ to complete the graphite intercalation condensation. The solid-liquid separation is completed by centrifugation at 6000 rpm. The condensation mother liquor is recycled 3 times and then sent to a triple-effect evaporator to crystallize and recover ammonium sulfate. The remaining concentrated condensation mother liquor is disposed of as hazardous waste. The solid filter cake is dried under slight negative pressure to form the graphite condensation-loaded material.

[0064] Step 5, Titanium Source Molecular Anchoring and Bonding Process: 430 kg of graphite condensation-loaded material is added to a mixing vessel, along with a mixture of anhydrous ethanol and n-propanol (volume ratio 1:0.4), 26 kg of rutile powder, 130 kg of titanium tetrachloride, 100 kg of 98% concentrated sulfuric acid, and 123 kg of 65% nitric acid. The system is maintained at 120°C and 2 kg / cm² for 1.5 h. Titanium tetrachloride undergoes controlled hydrolysis in the acidic alcohol system, forming Ti-OC covalent bonds with oxygen-containing groups on the graphite surface through dehydration. After natural cooling, the material is removed, dried under negative pressure, and then calcined at 650°C for 2 h in an electric baking oven to obtain 500 kg of carbon-based electrocatalytic material.

[0065] Example 2

[0066] A carbon composite electrocatalytic electrode comprises a substrate and a catalytic composite layer; the substrate is a cold-pressed plate formed by thoroughly mixing worm-shaped expanded graphite obtained through expansion treatment with thermoplastic PVDF nano-sized resin powder and thermoplastic PBT nano-sized resin powder in a mass ratio of 92:4:4; the catalytic composite layer is a powder layer formed by thoroughly mixing the carbon composite electrocatalytic material of Example 1 with thermoplastic PVDF nano-sized resin powder and thermoplastic PBT nano-sized resin powder in a mass ratio of 92:4:4.

[0067] The carbon composite electrocatalytic electrode was prepared by the following steps:

[0068] Step 1: Stack the above-mentioned substrate and the above-mentioned catalytic composite layer in a mold of a hot press;

[0069] Step 2: Hot-press and hold at 160-180℃ and 35MPa for 1 hour, then cool for 1 hour. After demolding, the carbon composite electrocatalytic electrode is obtained.

[0070] Comparative example (corresponding scheme S2 in the attached figure)

[0071] Preparation of EG-PAN-TiO2 electrocatalytic materials:

[0072] (1) After ultrasonic cleaning of expanded graphite powder with ultrapure water and a 1:0.4 mixture of anhydrous ethanol and n-propanol for 30 min, it was placed in a vacuum drying oven and dried at 80℃ for 8 h.

[0073] (2) Place 10g of pretreated expanded graphite powder into an aniline-ethanol (volume ratio 1:4) solution and sonicate at 60HZ for 30min.

[0074] (3) The expanded graphite powder that has been washed with ultrapure water is added to 750 mL of HCl / H2SO4 (0.5 M / 1 M) mixed acid solution. While stirring, 7.6325 g of ammonium persulfate is added. After stirring at 6 °C for 10 h, the mixture is filtered and dried at 80 °C for 10 h to obtain EG-PAN powder.

[0075] (4) Mix 1g of EG-PAN powder, 7.5ml of tetrabutyl titanate, 22.5ml of anhydrous ethanol and n-propanol in a 1:0.4 ratio and stir with a magnetic stirrer for 20min to form mixed solution A.

[0076] (5) Mix 22.5 ml of anhydrous ethanol and n-propanol in a 1:0.4 ratio, 3 ml of deionized water and 0.6 ml of concentrated nitric acid, and stir with a magnetic stirrer for 20 min to form mixed solution B.

[0077] (6) Add mixed solution B dropwise to mixed solution A at a volume ratio of 1:1, mix them thoroughly and evenly, and then let them stand at 20°C for a period of time until a non-flowing gel system is formed.

[0078] (7) Place it in an oven at 105℃ and dry for 8 hours to obtain blackish-gray particles.

[0079] (8) Grind it into powder using a glass mortar and calcine it in a muffle furnace at 500°C for 2 hours to obtain self-supporting carbon-based TiO2 electrocatalytic material—EG-PAN-TiO2 powder. This is denoted as sample S2.

[0080] Comparative example of blank sample (pure expanded graphite) (corresponding scheme SO in the attached figure)

[0081] HER linear scans were performed on Example 1 (S1) and Comparative Example (S2) to obtain... Figure 1 The LSV HER curves are shown. Curve ①: Blank sample S0; Curve ②: Comparative example S2 (EG-PAN-TiO2); Curve ③: Example S1 (carbon composite material of the present invention). As can be seen from the graphs, 10 mA·cm⁻¹ is achieved. -2 At the current density, the overpotential of S1 is significantly lower than that of S2, proving that the electrocatalytic activity of the present invention is superior.

[0082] Figure 2These are the Tafel slope fitting curves for samples S1 and S2. Curve ① S2; Curve ② S1. The smaller Tafel slope in S1 indicates a lower kinetic barrier to the electrocatalytic reaction and a faster interfacial electron transport rate.

[0083] Electrochemical impedance spectroscopy was performed on samples S1 and S2 to obtain... Figure 3 EIS Nyquist plot. The origin on the left represents the high-frequency region, and the arc diameter represents the charge transfer impedance Rct; the impedance arc diameter of S1 is significantly smaller than that of S2. This confirms that the Ti-OC covalent bond effectively reduces the interfacial contact resistance between the carbon substrate and TiO2.

[0084] Constant current long-term cyclic experiment was performed on samples S1 and S2 to obtain... Figure 4 The long-term cycling stability curves for constant current (It) are shown in curve ①S2 and curve ②S1. Under constant current density, the potential of S2 increases significantly and continuously; the potential of S1 fluctuates little and decays only slightly. This proves that TiO2 in S1 is anchored by covalent bonds, making it difficult to detach during long-term electrolysis, thus greatly improving cycling stability.

[0085] Figure 5 These are the XRD diffraction patterns of samples S1 and S2. Curve ① S1; Curve ② S2. S1 shows characteristic diffraction peaks of both rutile TiO2 and anatase TiO2 (mixed crystal structure); S2 only shows characteristic peaks of anatase TiO2.

[0086] Figure 6 The XPS high-resolution Ti 2p spectrum of sample S1 shows the characteristic binding energy peaks corresponding to the Ti-OC chemical bonds, proving that the carbon substrate and titanium oxide form covalent bonds. Figure 7 This is the high-resolution XPS spectrum of Ti 2p from sample S2. Only Ti is present. 4 +(TiO2) characteristic peak, no Ti-OC characteristic signal, indicating that titanium dioxide and carbon substrate are only physically bonded.

[0087] Figure 8 This is a comparison of the TEM morphology of samples S1 and S2. From... Figure 8 It can be clearly seen from the text.

[0088] (a)S1: TiO2 nanoparticles are tightly anchored to the surface of the carbon sheet, with tight interfacial bonding and no obvious gaps;

[0089] (b)S2: TiO2 particles are locally agglomerated, and there are clear gaps at the interface between carbon and TiO2, which is a physical coating structure.

Claims

1. A method for preparing a carbon composite electrocatalytic material, characterized in that, The process includes the following steps: Step 1: Material preparation and expansion process: Preheat the electric heating furnace to 700-750℃, take 260kg of expandable graphite raw material with a purity of 99.8%, feed it into the electric heating furnace in a closed negative pressure environment, continue heating in the furnace to 800-850℃, keep the temperature constant for 15s, and the graphite volume expands by 260-480 times to obtain worm-shaped expanded graphite. Step 2: Volume Reduction and Preloading Process: 260 kg of worm-shaped expanded graphite is transferred into a mixing vessel, and 9480 kg of anhydrous ethanol and n-propanol mixture at a volume ratio of 1:0.4 and 2.6 kg of rutile powder pretreated with 8.5 kg of 98% concentrated sulfuric acid are added. The mixture is stirred and suspended to complete the preloading of the titanium component. The mixture is then separated into solid and liquid phases using a variable speed centrifugal filter (1500-3000 rpm). The solid filter cake is sent to the next process, while the liquid phase ethanol-n-propanol mixture is discharged into an ethanol-n-propanol recovery tank for direct recycling. Step 3: Volume-reduced nitrogen doping process: The volume-reduced solid filter cake is fed into a reactor, and 9480 kg of a mixture of anhydrous ethanol and n-propanol at a volume ratio of 1:0.4 is added. 8.5 kg of 98% concentrated sulfuric acid is added to prepare an acidic system, and 4740 kg of 99.9% pure aniline at 0℃ is slowly added. After stirring and reacting, the material is fed into a variable-speed centrifugal filter (1500-3000 rpm) for solid-liquid separation. The material is washed with a mixture of anhydrous ethanol and n-propanol at a volume ratio of 1:0.

4. The mixed mother liquor of ethanol, n-propanol, and aniline is recycled. The filter cake is dried under a slightly negative pressure environment to remove ethanol and n-propanol, becoming a volume-reduced nitrogen-doped graphite-supported material. The volatilized gaseous ethanol and n-propanol are condensed and recovered. Step 4: Condensation process: The nitrogen-doped graphite-loaded material is put into a mixing vessel, and 3000 kg of distilled water, 800 kg of 31% hydrochloric acid, 120 kg of 98% concentrated sulfuric acid, and 50 kg of ammonium persulfate are added in sequence to form a condensation mother liquor. The graphite intercalation condensation is completed by controlling the temperature at 0℃. The solid-liquid separation is completed by centrifugation at 6000 rpm. The condensation mother liquor is recycled 3 times and then sent to a triple-effect evaporator to crystallize and recover ammonium sulfate. The remaining concentrated condensation mother liquor is disposed of as hazardous waste. The solid filter cake is dried under micro-negative pressure to form graphite condensation-loaded material. Step 5: Titanium source molecular anchoring and bonding process: 430 kg of graphite condensation-loaded material is added to a mixing vessel, along with a mixture of anhydrous ethanol and n-propanol (volume ratio 1:0.4), 26 kg of rutile powder, 130 kg of titanium tetrachloride, 100 kg of 98% concentrated sulfuric acid, and 123 kg of 65% nitric acid. The system temperature is 120℃, and the pressure is 2 kg / cm². 2 After maintaining the temperature for 1.5 hours, titanium tetrachloride undergoes controlled hydrolysis in an acidic alcohol system, forming Ti-OC covalent bonds with oxygen-containing groups on the graphite surface through dehydration. After natural cooling, the material is removed, dried under negative pressure, and then calcined at 650°C for 2 hours in an electric baking oven to obtain 500 kg of carbon composite electrocatalytic material.

2. The method for preparing the carbon composite electrocatalytic material according to claim 1, characterized in that, The density of the expanded graphite after expansion in step 1 is 0.001-0.004 g / cm³. 3 .

3. The method for preparing the carbon composite electrocatalytic material according to claim 1, characterized in that, The drying temperature in step 3 is 60-65℃.

4. The method for preparing the carbon composite electrocatalytic material according to claim 1, characterized in that, In step 4, the evaporation temperature of the triple-effect evaporator is 95-102℃, and the filter cake is sent to a steam-heated negative pressure dryer at a drying temperature of 90℃.

5. The method for preparing the carbon composite electrocatalytic material according to claim 1, characterized in that, In step 4, the mass ratio of distilled water, 31% hydrochloric acid, 98% concentrated sulfuric acid, and ammonium persulfate in the condensation mother liquor is 300:80:12:

5.

6. The method for preparing the carbon composite electrocatalytic material according to claim 1, characterized in that, The drying temperature in step 5 is 65℃.

7. The method for preparing the carbon composite electrocatalytic material according to claim 1, characterized in that, In each step, the ethanol-n-propanol mother liquor generated by centrifugation is uniformly recovered to the ethanol-n-propanol recovery tank for condensation and recycling, and can be directly reused without distillation.

8. A carbon composite electrocatalytic material, characterized in that, It is prepared by any one of the preparation methods described in claims 1-7.

9. A carbon composite electrocatalytic electrode, characterized in that, The material comprises a substrate and a catalytic composite layer. The substrate is a cold-pressed plate formed by thoroughly mixing worm-shaped expanded graphite obtained through expansion treatment with thermoplastic PVDF nano-sized resin powder and thermoplastic PBT nano-sized resin powder in a mass ratio of 92:4:

4. The catalytic composite layer is a powder layer formed by thoroughly mixing the carbon composite electrocatalytic material of claim 8 with thermoplastic PVDF nano-sized resin powder and thermoplastic PBT nano-sized resin powder in a mass ratio of 92:4:

4.

10. A method for preparing a carbon composite electrocatalytic electrode, characterized in that, Includes the following steps: Step 1: Stack the substrate described in claim 9 and the catalytic composite layer described in claim 9, and place them in the mold of a hot press; Step 2: Hot-press and hold at 160-180℃ and 35MPa for 1 hour, then cool for 1 hour. After demolding, the carbon composite electrocatalytic electrode is obtained.

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