Coal gasification fine ash derived graded porous carbon loaded multi-metal layered hydroxide composite material as well as preparation method and application thereof

Abstract

The invention relates to a coal gasification fine ash derived graded porous carbon loaded multi-metal layered hydroxide composite material as well as a preparation method and application thereof.The preparation method of the material comprises the following steps: mixing coal gasification fine ash and an alkaline substance, performing melting treatment, mixing with a first inorganic acid solution, and performing stirring treatment to obtain a second material; carrying out washing treatment and drying treatment on the second material to obtain ash-removed carbon residues; mixing the ash-removed carbon residues with an activating agent, performing grinding treatment, and then performing heating treatment to obtain an active product; mixing the active product with a second inorganic acid solution, and carrying out stirring treatment, washing treatment and drying treatment to obtain graded porous carbon; mixing the graded porous carbon with metal salt, dispersing the mixture into a solvent, adding a surface modifier, and stirring to obtain a mixture; and carrying out hydrothermal treatment, centrifugal treatment, washing treatment and drying treatment on the mixture. The material is excellent in electrochemical performance and can be used as a high-performance supercapacitor positive electrode material.

Description

Technical Field

[0001] This invention relates to the field of energy storage materials technology, specifically to a method for preparing and applying a graded porous carbon-supported multimetal layered hydroxide composite material derived from coal gasification fine ash. Background Technology

[0002] Currently, the treatment of coal gasification ash is still mainly through landfill and stockpiling. This method not only requires a large amount of land resources and causes soil and air pollution problems, but also the 30% to 60% residual carbon resources in coal gasification ash have not yet been effectively utilized at a high value, creating a dual contradiction of "environmental burden and resource waste".

[0003] Supercapacitors, as energy storage devices combining high power density and long cycle life, are in urgent demand in fields such as start-stop systems for new energy vehicles, peak shaving for smart grids, and emergency power supplies. Their performance hinges on the electrode materials. Among these, multi-metal layered hydroxide / porous carbon coupling materials, combining the high pseudocapacitive properties of multi-metal layered hydroxides with the high conductivity and stability of porous carbon materials, have become a preferred option for supercapacitor cathodes. In recent years, significant progress has been made in the research of preparing carbon-based electrode materials using solid waste.

[0004] While existing technologies have shown that using coal gasification fine ash as raw material, metal oxides and silicon-based impurities are removed by combined HCl-HF acid washing, followed by KOH activation to directly prepare activated carbon for supercapacitors, this process omits the carbonization step in traditional activated carbon preparation and utilizes the porous structure of the coal gasification fine ash residue to achieve a specific surface area of ​​1200~2290 m². 2 / g, meeting the Class I standard for porous carbon for supercapacitors in the national standard GB / T 37386-2019, providing a basic path for high-value utilization of residual carbon in coal gasification fine ash. However, there is still room for optimization in this technology: First, in the traditional HCl-HF combined pickling, HF is highly corrosive, requiring specialized corrosion-resistant equipment, which not only increases production input but also requires additional treatment of fluoride-containing wastewater, increasing environmental costs and process complexity; Second, the pore structure of activated carbon derived from coal gasification fine ash is mostly single-pore-size controlled, which easily leads to the aggregation of metal hydroxides on the carbon substrate surface, reducing the exposure of active sites; Third, during the multi-metal layered hydroxide loading process, the interfacial interaction between the carbon substrate and metal ions is not sufficiently controlled, resulting in insufficient ion transport efficiency and cycle stability of the composite material.

[0005] Therefore, developing a method for preparing a coal gasification fine ash-derived multimetallic layered hydroxide / hierarchical porous carbon composite material with low corrosion ash removal, precise control of hierarchical porous carbon pore structure, and synergistic optimization of loading performance can not only reduce the environmental and economic costs of solid waste treatment, but also further improve the comprehensive performance of energy storage materials. This has important practical significance for promoting the resource utilization of industrial solid waste and the industrialization of electrochemical energy storage technology. Summary of the Invention

[0006] The purpose of this invention is to improve the overall performance of energy storage materials while reducing the environmental and economic costs of solid waste treatment.

[0007] To achieve the above objectives, the present invention is implemented as follows: The first aspect of this invention provides a method for preparing a hierarchical porous carbon-supported multimetal layered hydroxide composite material derived from coal gasification fine ash, the method comprising the following steps: S1. The fine ash from coal gasification is mixed with an alkaline substance and then melted to obtain a first material; the first material is mixed with an inorganic acid solution and then stirred to obtain a second material; the second material is then washed and dried to obtain deashed carbon residue. S2. The deashed carbon residue is mixed with an activator and ground to obtain a first mixture; the first mixture is heated to obtain an active product; the active product is mixed with a second inorganic acid solution and stirred to obtain a third material; the third material is washed and dried to obtain coal gasification fine ash-derived graded porous carbon. S3. The fine ash from coal gasification is used to derive graded porous carbon and metal salt to obtain a second mixture; the second mixture is dispersed in a solvent and a surface modifier is added for a third stirring treatment to obtain a third mixture; the third mixture is subjected to hydrothermal treatment to obtain a fourth material; the fourth material is subjected to centrifugation, a third washing treatment and a third drying treatment in sequence. In step S2, the heating treatment is carried out in an inert atmosphere, and the heating treatment includes a first stage of heating and a second stage of heating. The temperature of the first stage of heating is 400~500℃, and the temperature of the second stage of heating is 700~800℃. In step S3, the metal salt contains a metal element M, which includes at least one element from Group VIIB and / or Group VIII.

[0008] Optionally, the metal salt includes at least one of nickel salt, cobalt salt, manganese salt, and iron salt; optionally, the metal salt is selected from Ni(NO3)2·6H2O, Ni(CH3COO)2, Co(NO3)2·6H2O, (CH3COO)2Co, Mn(NO3)2·6H2O, (CH3COO)2Mn, Fe(NO3)3, Fe(CO2CH3)2, and Fe(NO3)2.

[0009] Optionally, in step S1, the mass ratio of the coal gasification fine ash to the alkaline substance is 1:(1~6); and / or, in step S2, the mass ratio of the deashed carbon residue to the activator is 1:(1~6); and / or, in step S3, the molar ratio of the coal gasification fine ash-derived graded porous carbon to the metal salt is 1:(1~6); and / or, the amount of the surface modifier is 0.3~0.8 mmol per millimole of the second mixture.

[0010] Optionally, in step S1, the alkaline substance includes NaOH. The first inorganic acid solution comprises at least one of KOH, K2CO3, and KHCO3; and / or, the mass fraction of the first inorganic acid solution is 8-15%; optionally, the first inorganic acid solution comprises at least one of HCl solution, HNO3 solution, H2SO4 solution, and CH3COOH solution, preferably HCl solution; and / or, in step S2, the activator comprises at least one of NaOH, KOH, K2CO3, and KHCO3; and / or, the mass fraction of the second inorganic acid solution is 5-30%; optionally, the second inorganic acid solution comprises at least one of HCl solution, HNO3 solution, H2SO4 solution, and CH3COOH solution, preferably HCl solution; and / or, in step S3, the surface modifier comprises at least one of polyethylene glycol, 1-aminopropyl-3-methylimidazolium bromide ionic liquid, polylactic acid, dodecylbenzenesulfonic acid, and sodium citrate; and / or, the solvent is a mixture of water and ethylene glycol; preferably, the volume ratio of the water and the ethylene glycol is 1:(3-5).

[0011] Optionally, in step S1, the D50 of the coal gasification fine ash is ≤100μm; and / or, in step S2, the D50 of the first mixture is ≤5μm.

[0012] Optionally, in step S1, the melting treatment conditions include: a heating rate of 2~10℃ / min, a temperature of 300~500℃, and a time of 0.5~2 h; and / or, the first stirring treatment conditions include: a temperature of 30~60℃, and a time of 1~2 h; and / or, the first washing treatment step includes: washing the second material with water until the pH of the filtrate is 6~7; and / or, the first drying treatment conditions include: a pressure of 0.1~0.3MPa, a temperature of 80~100℃, and a time of 12~24 h.

[0013] Optionally, in step S2, the inert atmosphere includes nitrogen, and the flow rate of the inert atmosphere is 50~80 mL / min; and / or, the heating rate of the first stage of heating is 2~20℃ / min, and the time is 0.5~1 h; and / or, the heating rate of the second stage of heating is 2~20℃ / min, and the time is 1~2 h; and / or, the conditions for the second drying treatment include: a temperature of 80~100℃ and a time of 12~24 h.

[0014] Optionally, in step S3, the conditions for the second stirring treatment include: a temperature of 15~40℃ and a time of 1~1.5h; and / or, the conditions for the hydrothermal treatment include: a temperature of 130~200℃ and a time of 20~48h; and / or, the conditions for the centrifugation treatment include: a rotation speed of 8000~10000 rpm and a time of 10~15 min; and / or, the washing liquid for the third washing includes water and anhydrous ethanol; and / or, the conditions for the third drying treatment include: a temperature of 80~100℃ and a time of 12~24h.

[0015] A second aspect of the present invention provides an energy storage material, wherein the energy storage material is a graded porous carbon-supported multimetal layered hydroxide composite material derived from coal gasification fine ash prepared according to the above method.

[0016] A third aspect of the present invention provides a supercapacitor comprising an energy storage material, wherein the energy storage material is a graded porous carbon-supported multimetal layered hydroxide composite material derived from coal gasification fine ash prepared according to the above method, or the above-described energy storage material.

[0017] The beneficial technical effects of this invention through the above technical solutions are as follows: The preparation method of this application adopts an environmentally friendly alkali fusion process, reducing equipment costs and the difficulty of waste liquid treatment; it precisely constructs a "microporous-mesoporous" hierarchical structure to match the loading requirements of multi-metal hydroxides, reducing agglomeration and increasing the exposure of active sites. The material prepared by this application exhibits excellent electrochemical performance, with a BET specific surface area reaching 758 m². 2The specific capacitance of the material prepared in this application reaches 691 F / g at a current density of 5 A / g in a three-electrode system, and the capacitance retention rate reaches 68.64% at a rate of 3~50 A / g. The material prepared in this application can be used as a positive electrode material for high-performance supercapacitors, achieving the dual goals of high-value utilization of coal gasification fine ash solid waste and performance improvement of energy storage materials.

[0018] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0020] Figure 1 The diagram shown is a process flow chart of the preparation method of the present invention.

[0021] Figure 2 The figure shows the charge-discharge curve of the composite material prepared in Example 1 of the present invention. Detailed Implementation

[0022] This invention discloses a hierarchical porous carbon-supported multimetal layered hydroxide composite material derived from coal gasification fine ash, its preparation method, and its applications. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the same result. It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0023] In the description of this invention, the list of items connected by the term "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0024] The first aspect of this invention provides a method for preparing a hierarchical porous carbon-supported multimetal layered hydroxide composite material derived from coal gasification fine ash, such as... Figure 1As shown, the preparation method includes the following steps: S1. The fine ash from coal gasification is mixed with an alkaline substance and then melted to obtain a first material; the first material is mixed with a first inorganic acid solution and stirred to obtain a second material; the second material is washed and dried to obtain deashed carbon residue. S2. The deashed carbon residue is mixed with an activator and ground to obtain a first mixture; the first mixture is heated to obtain an active product; the active product is mixed with a second inorganic acid solution and stirred to obtain a third material; the third material is washed and dried to obtain coal gasification fine ash-derived graded porous carbon. S3. The fine ash from coal gasification is used to derive graded porous carbon and metal salt to obtain a second mixture; the second mixture is dispersed in a solvent and a surface modifier is added for a third stirring treatment to obtain a third mixture; the third mixture is subjected to hydrothermal treatment to obtain a fourth material; the fourth material is subjected to centrifugation, a third washing treatment and a third drying treatment in sequence. In step S2, the heating treatment is carried out in an inert atmosphere, and the heating treatment includes a first stage of heating and a second stage of heating. The temperature of the first stage of heating is 400~500℃, and the temperature of the second stage of heating is 700~800℃. In step S3, the metal salt contains a metal element M, which includes at least one element from Group VIIB and / or Group VIII.

[0025] The preparation method of this application uses coal gasification fine ash as carbon precursor and prepares multi-metal layered hydroxide / porous carbon composite material through an integrated process of "alkali fusion deashing - gradient heating + activation - surfactant-assisted hydrothermal loading". This application constructs a "microporous-mesoporous" hierarchical porous carbon structure by gradient heating to match the loading requirements of multi-metal layered hydroxide and increase the number of energy storage active sites in the material; it also improves the dispersibility of metal layered hydroxide on the carbon substrate and can enhance the electrochemical performance of the composite material.

[0026] In step S1 of this invention, soluble sodium silicate and sodium aluminate are generated by reacting molten alkali with silicon and aluminum oxides (such as SiO2 and Al2O3) in the fine ash from coal gasification, thus initially removing silicon-based impurities. The first material is then subjected to a first stirring treatment with an inorganic acid solution. Impurities are removed by reacting the inorganic acid solution with metal oxides (such as Fe2O3 and CaO) or activated carbonates. The filtrate is then subjected to a first washing treatment until the pH of the filtrate is 6-7 (free of Cl). - The residue is then subjected to a first drying process to obtain deashed char.

[0027] In step S2 of this invention, the deashed carbon residue is mixed with an activator and then activated by gradient heating. The first stage of heating is at 400-500°C, where the alkaline substance reacts with the functional groups on the surface of the carbon residue at a low temperature, thus completing the initial etching of micropores. The second stage of heating is at 700-800°C, where the alkaline substance further etches the micropores and expands them into mesopores, forming a multi-level structure of "micropores (<2nm) - mesopores (2~50 nm)," thereby preparing a hierarchical porous carbon (active product) with a mesopore volume ratio ≥80%. The active product is then subjected to a second stirring treatment with a second inorganic acid solution to remove residual activator and salts (such as carbonates) generated in the reaction. After filtration, a second washing treatment and a second drying treatment are performed to obtain the hierarchical porous carbon derived from coal gasification fine ash (mesopore volume ratio ≥80%).

[0028] In step S3 of this invention, the second mixture is dispersed in a solvent to form a mixed solvent system to improve dispersibility. This dispersion step may involve magnetic stirring. A surface modifier is then added for a third stirring treatment. The hydroxyl groups of the surface modifier bind to the functional groups on the carbon substrate surface, inhibiting the aggregation of transition metal ions through steric hindrance, resulting in a third mixture. The third mixture is then subjected to hydrothermal treatment, followed by centrifugation, a third washing treatment (to remove unreacted salts and surface modifiers), and a third drying treatment to obtain the multi-metal layered hydroxide / porous carbon composite material of this invention.

[0029] In embodiments of the present invention, the metal salt may include at least one of nickel salt, cobalt salt, manganese salt, and iron salt.

[0030] For example, the metal salt may be selected from Ni(NO3)2・6H2O, Ni(CH3COO)2, Co(NO3)2・6H2O, (CH3COO)2Co, Mn(NO3)2・6H2O, (CH3COO)2Mn, Fe(NO3)3, Fe(CO2CH3)2 and Fe(NO3)2.

[0031] According to the present invention, in step S1, the mass ratio of the coal gasification fine ash and the alkaline substance can be 1:(1~6), preferably, the mass ratio of the coal gasification fine ash and the alkaline substance can be 1:5.

[0032] According to the present invention, in step S2, the mass ratio of the deashed carbon residue to the activator can be 1:(1~6), preferably, the mass ratio of the deashed carbon residue to the activator can be 1:5.

[0033] According to the present invention, in step S3, the molar ratio of the coal gasification fine ash-derived graded porous carbon to the metal salt is 1:(1~6), preferably 1:2; and / or, relative to each millimole of the second mixture, the amount of the surface modifier is 0.3~0.8 mmol, preferably 0.3 mmol.

[0034] For example, the alkaline substance may include at least one selected from NaOH, KOH, K2CO3, and KHCO3. Preferably, the alkaline substance is NaOH.

[0035] According to the present invention, the mass fraction of the first inorganic acid solution can be 8-15%; optionally, the first inorganic acid solution includes at least one of HCl solution, HNO3 solution, H2SO4 solution and CH3COOH solution, preferably HCl solution.

[0036] For example, the activator includes at least one of NaOH, KOH, K2CO3 and KHCO3.

[0037] According to the present invention, the mass fraction of the second inorganic acid solution can be 5-30%; optionally, the second inorganic acid solution includes at least one of HCl solution, HNO3 solution, H2SO4 solution and CH3COOH solution, preferably HCl solution.

[0038] For example, the surface modifier may include at least one of polyethylene glycol (PEG), 1-aminopropyl-3-methylimidazolium bromide ionic liquid, polylactic acid, dodecylbenzenesulfonic acid, and sodium citrate.

[0039] According to the present invention, the solvent may be a mixture of water and ethylene glycol; preferably, the volume ratio of the water to the ethylene glycol is 1:(3~5), and more preferably, the volume ratio of the water to the ethylene glycol is 1:4.

[0040] In step S1 of the present invention, the D50 of the coal gasification fine ash is ≤100μm.

[0041] In step S2 of the present invention, the D50 of the first mixture is ≤5μm.

[0042] In one embodiment of the present invention, in step S1, the conditions for the melting treatment include: a heating rate of 2~10℃ / min, a temperature of 300~500℃, and a time of 0.5~2 h, preferably, the melting treatment temperature is 350℃ and the time is 0.5 h; and / or, the conditions for the first stirring treatment include: a temperature of 30~60℃ and a time of 1~2 h; and / or, the first washing treatment step includes: washing the second material with water until the pH of the filtrate is 6~7; and / or, the conditions for the first drying treatment include: a pressure of 0.1~0.3MPa, a temperature of 80~100℃, and a time of 12~24 h.

[0043] In one embodiment of the present invention, in step S2, the inert atmosphere includes nitrogen gas, and the flow rate of the inert atmosphere is 50~80 mL / min; and / or, the heating rate of the first stage of heating is 2~20℃ / min, and the time is 0.5~1 h; and / or, the heating rate of the second stage of heating is 2~20℃ / min, and the time is 1~2 h; preferably, the temperature of the first stage of heating is 500℃, and the holding time is 0.5 h; the temperature of the second stage of heating is 800℃, and the holding time is 1 h; and / or, the conditions of the second drying treatment include: a temperature of 80~100℃, and a time of 12~24 h.

[0044] In one embodiment of the present invention, in step S3, the conditions for the second stirring treatment include: a temperature of 15~40℃ and a time of 1~1.5h; and / or, the conditions for the hydrothermal treatment include: a temperature of 130~200℃ and a time of 20~48h. In the present invention, a hydrothermal treatment temperature below 130℃ is prone to insufficient loading, and a temperature above 200℃ is prone to damaging the pore structure of the carbon substrate. Preferably, the hydrothermal treatment temperature is 180℃ and the reaction time is 36h; and / or, the conditions for the centrifugation treatment include: a rotation speed of 8000~10000 rpm and a time of 10~15 min; and / or, the washing liquid for the second washing includes water and anhydrous ethanol; and / or, the conditions for the third drying treatment include: a temperature of 80~100℃ and a time of 12~24h.

[0045] A second aspect of the present invention provides an energy storage material, wherein the energy storage material is a graded porous carbon-supported multimetal layered hydroxide composite material derived from coal gasification fine ash prepared according to the above method.

[0046] A third aspect of the present invention provides a supercapacitor comprising an energy storage material, wherein the energy storage material is a graded porous carbon-supported multimetal layered hydroxide composite material derived from coal gasification fine ash prepared according to the above method, or the above-described energy storage material.

[0047] The present invention will be further described in detail below through examples. All raw materials used in the examples are commercially available.

[0048] Example 1 Alkali dissolution deashing: 10 g of coal gasification fine ash was mixed with 40 g of NaOH solution and treated at 350℃ for 1 h. After the reaction, the sample was mixed with 8% HCl solution at a solid-liquid ratio of 1:3 and stirred at 30℃ for 1 h. The mixture was then filtered again and the filter residue was washed with distilled water until the pH of the filtrate was 6-7. The residue was then vacuum dried at 90℃ for 18 h to obtain deashed carbon residue (ash content of 2.15% and carbon residue recovery rate of 92%).

[0049] Gradient temperature activation: 2 g of deashed char residue and 8 g of KOH (mass ratio 1:4) were ground evenly. In a tube furnace, N2 flow rate was 60 mL / min, and the temperature was increased to 500℃ at 5℃ / min and held for 0.5 h, then increased to 750℃ at 10℃ / min and held for 1 h. After cooling, the mixture was washed with 50 mL of 1% (w / w) dilute HCl and dried to obtain 1.29 g of decomposed porous carbon (specific surface area 2010 m²). 2 / g, mesoporous volume percentage 83%).

[0050] PEG-assisted hydrothermal loading: Weigh 0.5 mmol Ni(NO3)2・6H2O (0.145 g) and 0.5 mmol Co(NO3)2・6H2O (0.291 g), add 0.2 g of multi-porous carbon, 8 mL of distilled water and 24 mL of ethylene glycol, and stir for 25 min; add 0.5 mmol PEG-6000 (0.3 g), stir at room temperature for 1 h; transfer to a reactor, keep warm at 160℃ for 36 h; centrifuge and wash, and vacuum dry at 80℃ to obtain 0.55 g of the composite material of this example.

[0051] The composite material of this embodiment was subjected to performance testing: the BET specific surface area was 758 m². 2 / g, total pore volume is 1.05cm³ 3 / g (Detection method: A fully automated specific surface area and porosity analyzer (Micromeritics ASAP2460) was used to measure the specific surface area and pore distribution characteristics of the sample. The specific surface area of ​​the sample was calculated using the Brunauer-Emmett-Teller (BET) method. The average pore volume and pore diameter were measured using the Barrett-Joyner-Halenda (BJH) method.)

[0052] In a three-electrode system, at a current density of 5 A / g, the sample's specific capacitance was 641 F / g. When the current density increased from 3 A / g to 50 A / g, the specific capacitance of the composite material prepared in this embodiment decreased from 641 F / g to 440 F / g, while the capacitance retention rate reached 68.64% (e.g., ...). Figure 2 (As shown). The specific testing method is as follows: 80 wt% of the composite material sample, 10 wt% of carbon black, and 10 wt% of polytetrafluoroethylene (PTFE) were weighed and mixed. Then, a certain mass of the mixture was weighed and adhered to a nickel foam current collector (~1 cm × 1 cm), and vacuum dried at 80℃ for 24 h. Finally, the dried nickel foam electrode was pressed at 10 MPa to obtain the working electrode. The loading mass of the active material on the nickel foam current collector was approximately 1 mg / cm³. 2 In the three-electrode system, 6 M KOH solution was used as the electrolyte, and platinum foil and saturated calomel electrodes were used as the counter and reference electrodes, respectively. The voltage window was set to 0–0.5 V. Based on the GCD curve, the mass specific capacitance of the sample was calculated according to the following formula: C p = IΔt / ΔVm (4) in C p It is the specific capacitance of the sample (F / g). I It is the current (A). Δt It is the discharge time (s). m It is the mass (g) of the active material. ΔV It is the voltage window (V). Example 2 Alkali dissolution deashing: 10 g of coal gasification fine ash was mixed with 30 g of NaOH solution and treated at 350℃ for 1 h. After the reaction, the sample was mixed with 8% HCl solution at a solid-liquid ratio of 1:3 and stirred at 30℃ for 1 h. The mixture was then filtered again and the filter residue was washed with distilled water until the pH reached 6-7. The residue was then vacuum dried at 90℃ for 18 h to obtain deashed carbon residue (ash content of 4.25% and carbon residue recovery rate of 94%).

[0053] Gradient temperature activation: 2 g of deashed char residue was ground evenly with 10 g of KOH (mass ratio 1:5). In a tube furnace, the N2 flow rate was 60 mL / min, and the temperature was increased to 500℃ at 5℃ / min and held for 1 h. Then, the temperature was increased to 800℃ at 10℃ / min and held for 1 h. After cooling, the char was washed with 50 mL of 1% dilute HCl and dried to obtain 1.32 g of decomposed porous char (specific surface area 2165 m²). 2 / g, mesoporous volume percentage 87%).

[0054] PEG-assisted hydrothermal loading: Weigh 1 mmol Ni(NO3)2・6H2O (0.145 g) and 1 mmol Mn(NO3)2・6H2O (0.291 g), add 0.2 g of multi-porous carbon, 8 mL of distilled water and 24 mL of ethylene glycol, and stir for 5 min; add 0.5 mmol PEG-6000 (0.3 g), stir at room temperature for 1 h; transfer to a reaction vessel, keep warm at 160 °C for 36 h; centrifuge and wash, and vacuum dry at 80 °C to obtain 0.57 g of the composite material of this example.

[0055] The composite material of this embodiment was subjected to performance testing: the BET specific surface area was 615 m². 2 / g, total pore volume 0.98cm³ 3 / g; In a three-electrode system, the sample mass specific capacitance is 591 F / g when the current density is 5 A / g.

[0056] Comparative Example 1 Alkali dissolution deashing: 10 g of coal gasification fine ash was mixed with 30 g of NaOH solution and treated at 350℃ for 1 h. After the reaction, the sample was mixed with 8% HCl solution at a solid-liquid ratio of 1:3 and stirred at 30℃ for 1 h. The mixture was then filtered again and the filter residue was washed with distilled water until the pH reached 6-7. The residue was then vacuum dried at 90℃ for 18 h to obtain deashed carbon residue (ash content of 4.25% and carbon residue recovery rate of 94%).

[0057] Without gradient temperature activation: 2 g of deashed char residue was ground evenly with 10 g of KOH (mass ratio 1:5). The mixture was placed directly in a tube furnace at a flow rate of 60 mL / min and kept at 800℃ for 1 h. After cooling, it was washed with 50 mL of 1% dilute HCl and dried to obtain 1.02 g of decomposed porous char (specific surface area 2165 m²). 2 / g, mesoporous volume percentage 87%).

[0058] PEG-assisted hydrothermal loading: Weigh 1 mmol Ni(NO3)2・6H2O (0.145 g) and 1 mmol Mn(NO3)2・6H2O (0.291 g), add 0.2 g of multi-porous carbon, 8 mL of distilled water and 24 mL of ethylene glycol, and stir for 5 min; add 0.5 mmol PEG-6000 (0.3 g), stir at room temperature for 1 h; transfer to a reaction vessel, keep warm at 160 ℃ for 36 h; centrifuge and wash, and vacuum dry at 80 ℃ to obtain 0.45 g of the composite material of this comparative example.

[0059] The performance of the composite material in this comparative example was tested: the BET specific surface area was 603 m². 2 / g, total pore volume 0.87cm³ 3 / g; In a three-electrode system, the sample mass specific capacitance is 471 F / g when the current density is 5 A / g.

[0060] Comparative Example 2 Alkali dissolution deashing: 10 g of coal gasification fine ash was mixed with 30 g of NaOH solution and treated at 350℃ for 1 h. After the reaction, the sample was mixed with 8% HCl solution at a solid-liquid ratio of 1:3 and stirred at 30℃ for 1 h. The mixture was then filtered again and the filter residue was washed with distilled water until the pH reached 6-7. The residue was then vacuum dried at 90℃ for 18 h to obtain deashed carbon residue (ash content of 4.25% and carbon residue recovery rate of 94%).

[0061] Without gradient temperature activation: 2 g of deashed char residue was ground evenly with 10 g of KOH (mass ratio 1:5). The mixture was placed directly in a tube furnace at a flow rate of 60 mL / min and kept at 800℃ for 1 h. After cooling, it was washed with 50 mL of 1% dilute HCl and dried to obtain 1.02 g of decomposed porous char (specific surface area 2165 m²). 2 / g, mesoporous volume percentage 87%).

[0062] Hydrothermal loading without surfactant: Weigh 1 mmol Ni(NO3)2・6H2O (0.145 g) and 1 mmol Mn(NO3)2・6H2O (0.291 g), add 0.2 g of multi-porous carbon, 8 mL of distilled water and 24 mL of ethylene glycol, stir for 5 min, stir at room temperature for 1 h; transfer to a reaction vessel, keep at 160 ℃ for 36 h; centrifuge and wash, vacuum dry at 80 ℃ to obtain 0.65 g of the composite material of this comparative example.

[0063] The performance of the composite material in this comparative example was tested: the BET specific surface area was 417 m². 2 / g, total pore volume 0.57cm³ 3 / g; In a three-electrode system, the sample mass specific capacitance is 369 F / g when the current density is 5 A / g.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a graded porous carbon-supported multimetal layered hydroxide composite material derived from coal gasification fine ash, characterized in that, The preparation method includes the following steps: S1. The fine ash from coal gasification is mixed with an alkaline substance and then melted to obtain a first material; the first material is mixed with a first inorganic acid solution and stirred to obtain a second material; the second material is washed and dried to obtain deashed carbon residue. S2. The deashed carbon residue is mixed with an activator and ground to obtain a first mixture; the first mixture is heated to obtain an active product; the active product is mixed with a second inorganic acid solution and stirred to obtain a third material; the third material is washed and dried to obtain coal gasification fine ash-derived graded porous carbon. S3. The fine ash from coal gasification is used to derive graded porous carbon and metal salt to obtain a second mixture; the second mixture is dispersed in a solvent and a surface modifier is added for a third stirring treatment to obtain a third mixture; the third mixture is subjected to hydrothermal treatment to obtain a fourth material; the fourth material is subjected to centrifugation, a third washing treatment and a third drying treatment in sequence. In step S2, the heating treatment is carried out in an inert atmosphere, and the heating treatment includes a first stage of heating and a second stage of heating. The temperature of the first stage of heating is 400~500℃, and the temperature of the second stage of heating is 700~800℃. In step S3, the metal salt contains a metal element M, which includes at least one element from Group VIIB and / or Group VIII.

2. The preparation method according to claim 1, characterized in that, The metal salt includes at least one of nickel salt, cobalt salt, manganese salt, and iron salt; Optionally, the metal salt is selected from Ni(NO3)2・6H2O, Ni(CH3COO)2, Co(NO3)2・6H2O, (CH3COO)2Co, Mn(NO3)2・6H2O, (CH3COO)2Mn, Fe(NO3)3, Fe(CO2CH3)2 and Fe(NO3)2.

3. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of the coal gasification fine ash to the alkaline substance is 1:(1~6); and / or, In step S2, the mass ratio of the deashed char residue to the activator is 1:(1~6); and / or, In step S3, the molar ratio of the coal gasification fine ash-derived graded porous carbon to the metal salt is 1:(1~6); and / or, the amount of the surface modifier is 1~6 mmol per millimole of the second mixture.

4. The preparation method according to claim 1, characterized in that, In step S1, the alkaline substance includes at least one of NaOH, KOH, K2CO3, and KHCO3; and / or, the mass fraction of the first inorganic acid solution is 8-15%; optionally, the first inorganic acid solution includes at least one of HCl solution, HNO3 solution, H2SO4 solution, and CH3COOH solution, preferably an HCl solution; and / or, In step S2, the activator includes at least one of NaOH, KOH, K2CO3, and KHCO3; and / or, the mass fraction of the second inorganic acid solution is 5-30%; optionally, the second inorganic acid solution includes at least one of HCl solution, HNO3 solution, H2SO4 solution, and CH3COOH solution, preferably an HCl solution; and / or, In step S3, the surface modifier includes at least one of polyethylene glycol, 1-aminopropyl-3-methylimidazolium bromide ionic liquid, polylactic acid, dodecylbenzenesulfonic acid, and sodium citrate; and / or, the solvent is a mixture of water and ethylene glycol; preferably, the volume ratio of the water to the ethylene glycol is 1:(3~5).

5. The preparation method according to claim 1, characterized in that, In step S1, the D50 of the coal gasification fine ash is ≤100μm; and / or, In step S2, the D50 of the first mixture is ≤5μm.

6. The preparation method according to claim 1, characterized in that, In step S1, the melting treatment conditions include: a heating rate of 2~10℃ / min, a temperature of 300~500℃, and a time of 0.5~2 h; and / or, The conditions for the first stirring treatment include: a temperature of 30~60℃ and a time of 1~2 hours; and / or, The first washing process includes: washing the second material with water until the pH of the filtrate is 6-7; and / or, The conditions for the first drying process include: pressure of 0.1~0.3MPa, temperature of 80~100℃, and time of 12~24h.

7. The preparation method according to claim 1, characterized in that, In step S2, the inert atmosphere includes nitrogen gas, and the flow rate of the inert atmosphere is 50~80 mL / min; and / or, The heating rate of the first stage is 2~20℃ / min, and the time is 0.5~1 h; and / or, The heating rate of the second stage is 2~20℃ / min, and the time is 1~2 h; And / or, The conditions for the second drying process include: a temperature of 80~100℃ and a time of 12~24h.

8. The preparation method according to claim 1, characterized in that, In step S3, the conditions for the second stirring treatment include: a temperature of 15~40℃ and a time of 1~1.5h; and / or, The conditions for the hydrothermal treatment include: a temperature of 130~200℃ and a time of 20~48h; and / or, The centrifugation conditions include: a rotation speed of 8000~10000 rpm and a time of 10~15 min; and / or, The washing solution for the third wash includes water and anhydrous ethanol; and / or, The conditions for the third drying process include: a temperature of 80~100℃ and a time of 12~24 h.

9. An energy storage material, characterized in that, The energy storage material is a graded porous carbon-supported multimetal layered hydroxide coupling material derived from coal gasification fine ash prepared by the method according to any one of claims 1 to 8.

10. A supercapacitor, characterized in that, The supercapacitor includes an energy storage material, which is a graded porous carbon-supported multimetal layered hydroxide composite material derived from coal gasification fine ash prepared according to any one of claims 1 to 8, or the energy storage material according to claim 9.

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