Halloysite-kaolin derivatized nanoporous carbon materials and their preparation and use

Abstract

The present disclosure relates to heteroatom-doped activated nanoporous carbon materials prepared from a template material comprising natural halloysite-kaolin nanoclay, a carbon precursor, a heteroatom dopant precursor and an activator, which exhibit flake and nanotube morphology and have surface heteroatom functionality.

Description

[Technical field]

[0001] Priority document This application claims priority to Australian Provisional Patent Application No. 2021902019, entitled "Halloysite-Kaolin Derivatized Nanoporous Carbon Materials and Their Preparation and Uses", filed on July 2, 2021, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure generally relates to a derivatized activated nanoporous carbon material, its preparation method and its use. More specifically, the present disclosure relates to an N-doped activated nanoporous carbon material prepared from natural halloysite-kaolin nanoclay, its preparation method and its use. [Background technology]

[0003] Due to the natural abundance of sodium, sodium-ion batteries have attracted much interest and are promising complementary alternatives to lithium-ion batteries. Sodium-ion batteries typically consist of a hard carbon anode and a layered transition metal oxide cathode. One of the challenges is the design of a high-performance, low-cost anode material.

[0004] Supercapacitors can be recharged very quickly and release large amounts of power. Supercapacitors are ideal for energy storage, which undergoes frequent charge and discharge cycles at high currents and short times. They have attracted widespread attention, since they could emerge as a solution for many application-specific power systems, especially due to their promising use in electric vehicles. In this context, great efforts are being made in the development of new materials that can be used in supercapacitors.

[0005] Supercapacitors can be categorized into three types: electric double layer capacitors (EDLCs), pseudocapacitors, and hybrid types formed by the combination of EDLCs and pseudocapacitors. EDLCs do not have a traditional dielectric but use a virtual plate made of two layers of the same substrate, thereby resulting in an effective separation of charge, even though the physical separation of the layers is surprisingly thin (on the order of nanometers). The electrode-electrolyte interface incorporates a double layer formed between the electrolyte ions and the charge on the electrode. EDLCs store energy by electrostatic charge, as opposed to electrochemical reactions. The high porosity of the electrode material in EDLCs allows the plate to have a much larger surface area within a given volume, which in turn results in a high specific capacitance.

[0006] Increasing atmospheric CO2 concentrations are hypothesized to be one of the main reasons behind climate change and other harmful effects on the environment. Attempts have been made towards capturing and utilizing large amounts of CO2 to mitigate its impact on climate change. For example, montmorillonite clays, smectite, sepiolite, hydrotalcite, saponite and hectorite have been applied as CO2 sorbents.

[0007] Porous carbon has been proposed as a candidate material for anode materials, supercapacitors, and adsorbents due to its cost-effectiveness, high surface area, tunable pore structure, thermal and chemical stability, and promising electrochemical performance, etc. In this regard, different techniques have been employed to enhance the surface properties of porous carbon. Chemical activation of carbon with KOH, CO2, NH3, and H2O has led to the development of a 1000m 2High surface areas can be achieved with surface area values ​​exceeding 100 nm / g. (See Peng, Z.; Guo, Z.; Chu, W.; Wei, M. Facilitated Synthesis of High-Surface-Area Activated Carbon from Coal for Supercapacitors and High CO2 Sorption. RSC Adv. 2016, 6, 42019-42028.) Solid-state activation techniques have been developed using solid ZnCl2 or KOH as activators to prepare several activated porous carbon materials with high specific surface areas and large pore volumes that are responsible for very high CO2 sorption capacities.(e.g. Singh, G.;Lakhi,KS;Ramadass,K.;Sathish,CI;Vinu,A.High-Performance Biomass-Derived Activated Porous Biocarbons for Combined Pre-and Post-Combustion CO2Capture.ACS Sustainable Chem.Eng.2019,7,7412-7420;Singh,G.;Lakhi,KS;Sil,S.;Bhosale,SV;Kim,I.;Albahily,K.;Vinu,A.Biomass derived Porous Carbon for CO2Capture.Carbon 2019,148,164-186;Singh,G.;Kim,IY;Lakhi,KS;Joseph,S.;Srivastava,P.;Naidu,R.;Vinu,A.Heteroatom Functionalized Activated Porous Biocarbons and their Excellent Performance for CO2Capture at High pressure. J. Mater. Chem. A 2017, 5, 21196-21204; Singh, G.; Kim, IY; Lakhi, KS; Srivastava, P.; Naidu, R.; Vinu, A. Single Step Synthesis of Activated Bio-Carbons with a High Surface Area and their Excellent CO2 Adsorption Capacity. Carbon 2017, 116, 448-455.) It has also been reported that the morphology of the nanostructure affects the final surface properties of the porous carbon material. In this context, chemical and physical methods such as soft and hard template methods have been used to synthesize several types of porous carbon materials with different structures and morphologies.The most commonly used template for preparing ordered mesoporous carbon with high specific surface area is ordered mesoporous silica (see Peng, L.; Hung, C.-T.; Wang, S.; Zhang, X.; Zhu, X.; Zhao, Z.; Wang, C.; Tang, Y.; Li, W.; Zhao, D. Versatile Nanoemulsion Assembly Approach to Synthesize Functional Mesoporous Carbon Nanospheres with Tunable Pore Sizes and Architectures. J. Am. Chem. Soc. 2019, 141, 7073-7080). However, the synthesis of ordered mesoporous silica requires expensive chemicals and complicated synthetic procedures, which limits its large-scale commercialization.

[0008] Natural halloysite nanotubes (HNTs), a low-cost and naturally available clay material, have been used to prepare activated undoped nanoporous carbons (AHNCs) with flake and nanotube morphology and high specific surface area (see Kavitha Ramadass; CI Sathish; Sujanya Maria Ruban; Gopalakrishnan Kothandam; Stalin Joseph; Gurwinder Singh; Sungho Kim; Wangsoo Cha; Ajay Karakoti; Tony Belperio; Jia Bao Yi; and Ajayan Vinu. Carbon Nanoflakes and Nanotubes from Halloysite Nanoclays and Their Superior Performance in CO2Capture and Energy Storage. ACS Applied Materials&Interfaces 2020 12(10),11922-11933). However, a two-step activation was required for the preparation of AHNCs, which involved initial heating at 600 °C for 5 h, followed by washing with HCl and further heating at 900 °C for 5 h. This procedure was necessary to limit the transformation of kaolinite-halloysite to metakaolin at temperatures above 600 °C. Metakaolin is an ultrastable, complex, amorphous material that is difficult to dissolve using HF. Heating at 900 °C was necessary to increase the degree of graphitization of the carbon walls.

[0009] There remains a need for improved nanoporous carbon materials and / or improved methods for their fabrication having at least one of high specific surface area, large pore volume, surface functionality, and a mixture of micropores and mesopores, which can be used in applications including, but not limited to, anode materials for sodium-ion or lithium-ion batteries, supercapacitors, and / or CO2 adsorption. Summary of the Invention

[0010] In a first aspect, the present disclosure provides a doped activated nanoporous carbon material prepared from a template material comprising natural halloysite-kaolin nanoclay, a carbon precursor, a heteroatom dopant precursor and an activator, the doped activated nanoporous carbon material exhibiting flake and nanotube morphology and having surface heteroatom functionality.

[0011] In some embodiments, the template material is comprised of natural halloysite-kaolin nanoclay. In some further embodiments, the natural halloysite-kaolin nanoclay contains up to about 60% by weight kaolinite and about 40% by weight halloysite. In some further embodiments, the natural halloysite-kaolin nanoclay contains more than about 80% by weight halloysite nanotubes.

[0012] In some embodiments, the carbon precursor is a carbohydrate-based compound. In some further embodiments, the carbohydrate-based compound is a sugar-based compound. In certain of these embodiments, the sugar-based compound is selected from the group consisting of sucrose, glucose, polysaccharides, and fructose. In some exemplary embodiments, the polysaccharide is selected from the group consisting of cellulose, chitosan, and starch.

[0013] In some embodiments, the heteroatom dopant precursor is a nitrogen precursor. The nitrogen precursor can be a compound containing one or more nitrogen atoms. For example, the nitrogen precursor can be selected from the group consisting of aminoguanidine, aminoguanidine hydrochloride, aminotriazole, urea, chitosan, cyanamide, dicyanamide, thiourea, melamine, casein, polyaniline, polypyrrole, aminotetrazole, and aminotriazine. In some further embodiments, the nitrogen precursor is aminotriazole. In certain exemplary embodiments, the nitrogen precursor is 3-amino-1,2,4-triazole. The nitrogen precursor can be a compound containing one or more nitrogen atoms and one or more other heteroatoms, such as sulfur.

[0014] In some embodiments, the heteroatom dopant precursor is a sulfur precursor. The sulfur precursor can be a carbon compound containing one or more sulfur atoms. For example, the sulfur precursor can be selected from the group consisting of diphenyl disulfide, polyphenylene sulfide, bis(trimethylsilyl) sulfide, alkylthiol, and thiophene. Alternatively, the sulfur precursor can be an inorganic compound containing one or more sulfur atoms. For example, the sulfur precursor can be selected from the group consisting of sulfur powder, sodium sulfide, sodium dithionite, and sodium thiosulfate. Alternatively, the sulfur precursor can be a carbon-containing compound containing one or more sulfur atoms and one or more other heteroatoms, such as nitrogen. For example, the sulfur precursor can be selected from the group consisting of thiourea, thioacetamide, L-cysteine, methionine, dithiocarbamate, dithiooxamide, thiazoles, such as 2-aminothiazole, 5-amino-1,3,4-thiadiazole-2-thiol, thiosemicarbazide, and thiocarbohydrazide.

[0015] In some embodiments, the heteroatom dopant precursor is a boron precursor.The boron precursor can be a compound that contains one or more boron atoms.Suitable boron precursors include boric acid, ammonia borane (borazane), diborane, trimethylboron, koulmanite, boron trioxide, trimethoxyborane, sodium borate, borax, sodium borohydride, dimeric diborazane, trimeric triborazane, boron trifluoride, boron trichloride and phenyl borate.

[0016] In some embodiments, the heteroatom dopant precursor is an oxygen precursor. The oxygen precursor can be a compound that contains one or more oxygen atoms. Suitable oxygen precursors include boric acid, boron trioxide, sodium borate and borax.

[0017] The heteroatom dopant precursor can be any combination of two or more of the above precursors, such as a nitrogen precursor and a boron precursor, a nitrogen precursor and a sulfur precursor, a boron precursor, a sulfur precursor, a boron precursor and an oxygen precursor, a nitrogen precursor and an oxygen precursor, a sulfur precursor and an oxygen precursor or a nitrogen precursor, a boron precursor and a sulfur precursor. These combinations, for example, produce boron carbonitride materials.

[0018] In some embodiments, the activator is selected from the group consisting of zinc compounds, phosphoric acid, potassium acetate, sodium hydroxide, potassium carbonate, sodium carbonate, sodium chloride, potassium chloride, calcium chloride, carbon dioxide (CO2), ammonium carbonate, and ammonium persulfate. In some exemplary embodiments, the zinc compound is selected from the group consisting of zinc chloride (ZnCl2) and zinc oxide (ZnO).

[0019] In some embodiments, the carbon precursor and the template material are in a weight ratio of about 2:10 to about 4:10. In some exemplary embodiments, the carbon precursor and the template material are in a weight ratio of about 3:10.

[0020] In some embodiments, the heteroatom dopant precursor and the template material are in a weight ratio of about 1:12 to about 1:4. In some exemplary embodiments, the heteroatom dopant precursor and the template material are in a weight ratio of about 1:10.

[0021] In some embodiments, the activator and template material are in a weight ratio of about 1:6 to about 4:3. In some exemplary embodiments, the activator and template material are in a weight ratio of about 2:3.

[0022] In some embodiments, the doped activated nanoporous carbon material has a heteroatom content of about 0.25% to about 15.00% by weight. The heteroatom content of the doped activated nanoporous carbon material depends, at least in part, on factors such as synthesis method, carbonization temperature, and precursor selection.

[0023] In some embodiments, the doped activated nanoporous carbon material has a nitrogen (N) content of about 0.25% to about 15.00% by weight.

[0024] In some embodiments, the doped activated nanoporous carbon material has a sulfur (S) content of about 0.30% to about 2.28% by weight and a nitrogen (N) content of about (9.25%) to 19.76%.

[0025] In some embodiments, the doped activated nanoporous carbon material has a boron (B) content and oxygen (O) content of about 11.10% to 26.92% by weight.

[0026] In some embodiments, the doped activated nanoporous carbon material has a specific capacitance of greater than about 200 F / g at a current density of 0.3 A / g. In some embodiments, the doped activated nanoporous carbon material has a specific capacitance of about 299 F / g at a current density of 0.3 A / g. In some exemplary embodiments, the doped activated nanoporous carbon material has a specific capacitance of about 299 F / g, about 228 F / g, or about 194 F / g at current densities of 0.3 A / g, 0.5 A / g, and 1 A / g.

[0027] In some embodiments, the doped activated nanoporous carbon material has a molecular weight of about 1350 m. 2 / g~approx. 1700m 2 In some further embodiments, the doped activated nanoporous carbon material has a specific surface area of ​​about 1500 m 2 / g~approx. 1700m 2 In some further embodiments, the doped activated nanoporous carbon material has a specific surface area of ​​about 1600 m 2 / g~approx. 1700m 2 / g.

[0028] In some embodiments, the doped activated nanoporous carbon material has a thickness of about 1.0 cm 3 / g ~ approx. 1.6cm 3In some further embodiments, the doped activated nanoporous carbon material has a pore volume of about 1.3 cm 3 / g ~ approx. 1.6cm 3 In some further embodiments, the doped activated nanoporous carbon material has a pore volume of about 1.4 cm 3 / g ~ approx. 1.6cm 3 / g pore volume.

[0029] In some embodiments, the doped activated nanoporous carbon material has a molecular weight of about 1700 m 2 / g and a specific area of ​​approximately 1.465 cm 3 / g pore volume.

[0030] In some embodiments, the doped activated nanoporous carbon material has a CO2 adsorption capacity of at least about 22.5 mmol / g when determined at 0° C. and 30 bar. In some further embodiments, the doped activated nanoporous carbon material has a CO2 adsorption capacity of about 24.4 mmol / g when determined at 0° C. and 30 bar.

[0031] In a second aspect, the present disclosure provides a method for preparing a doped activated nanoporous carbon material, comprising the steps of: (a) loading a template material comprising natural halloysite-kaolin nanoclay with a carbon precursor and a heteroatom dopant precursor; (b) removing moisture and volatiles from the filled template material resulting from step (a) by heating; (c) preparing a composition comprising the filled template material obtained from step (b) and an activator; (d) activating and carbonizing the composition resulting from step (c) at a temperature of about 600° C. to about 900° C.; and (e) removing the template material and the activator from the composition resulting from step (d). The present invention provides a method comprising:

[0032] In some embodiments, for step (a), the template material consists of natural halloysite-kaolin nanoclay. In some further embodiments, the natural halloysite-kaolin nanoclay contains up to about 60% by weight kaolinite and about 40% by weight halloysite. In some further embodiments, the natural halloysite-kaolin nanoclay contains more than about 80% by weight halloysite nanotubes.

[0033] In some embodiments, for step (a), the carbon precursor is a carbohydrate-based compound. In some further embodiments, for step (a), the carbohydrate-based compound is a sugar-based compound. In certain of these embodiments, the sugar-based compound is selected from the group consisting of sucrose, glucose, fructose, and a polysaccharide. In some exemplary embodiments, the polysaccharide is selected from the group consisting of cellulose, chitosan, and starch.

[0034] In some embodiments, for step (a), the heteroatom dopant precursor is a nitrogen precursor. The nitrogen precursor can be a carbon compound containing one or more nitrogen atoms. For example, the nitrogen precursor can be selected from the group consisting of aminoguanidine, aminoguanidine hydrochloride, aminotriazole, urea, chitosan, cyanamide, dicyanamide, thiourea, melamine, casein, polyaniline, polypyrrole, aminotetrazole, and aminotriazine. In some further embodiments, the nitrogen precursor is aminotriazole. In certain exemplary embodiments, the nitrogen precursor is 3-amino-1,2,4-triazole.

[0035] In some embodiments, for step (a), the heteroatom dopant precursor is a sulfur precursor. The sulfur precursor can be a carbon compound containing one or more sulfur atoms. For example, the sulfur precursor can be selected from the group consisting of diphenyl disulfide, polyphenylene sulfide, bis(trimethylsilyl) sulfide, alkylthiol, and thiophene. Alternatively, the sulfur precursor can be an inorganic compound containing one or more sulfur atoms. For example, the sulfur precursor can be selected from the group consisting of sulfur powder, sodium sulfide, sodium dithionite, and sodium thiosulfate. Alternatively, the sulfur precursor can be a carbon-containing compound containing one or more sulfur atoms and one or more other heteroatoms, such as nitrogen. For example, the sulfur precursor can be selected from the group consisting of thiourea, thioacetamide, L-cysteine, methionine, dithiocarbamate, dithiooxamide, thiazoles, such as 2-aminothiazole, 5-amino-1,3,4-thiadiazole-2-thiol, thiosemicarbazide, and thiocarbohydrazide.

[0036] In some embodiments, for step (a), the heteroatom dopant precursor is a boron precursor. The boron precursor can be a compound that contains one or more boron atoms. Suitable boron precursors include boric acid, ammonia borane (borazane), diborane, trimethylboron, koulmanite, boron trioxide, trimethoxyborane, sodium borate, borax, sodium borohydride, dimeric diborazane, trimeric triborazane, boron trifluoride, boron trichloride and phenyl borate.

[0037] In some embodiments, for step (a), the heteroatom dopant precursor is an oxygen precursor. The oxygen precursor can be a compound that contains one or more oxygen atoms. Suitable oxygen precursors include boric acid, boron trioxide, sodium borate and borax.

[0038] In some embodiments, for step (a), the carbon precursor and the template material are in a weight ratio of about 2:10 to about 4:10. In some exemplary embodiments, the carbon precursor and the template material are in a weight ratio of about 3:10.

[0039] In some embodiments, for step (a), the heteroatom dopant precursor and the template material are in a weight ratio of about 1:12 to about 1:4. In some exemplary embodiments, the heteroatom dopant precursor and the template material are in a weight ratio of about 1:10.

[0040] In some embodiments, for step (a), the heteroatom dopant precursor and the carbon precursor are loaded into the template material by impregnation. In some further embodiments, an aqueous solution of the carbon precursor and an aqueous solution of the heteroatom dopant precursor are prepared separately and then dripped onto the template material to form the loaded template material. In certain of these embodiments, the water and template material used to prepare the solution are in a weight ratio of about 1:1 to about 2:1. In some exemplary embodiments, the water and template material used to prepare the solution are in a weight ratio of about 4:3.

[0041] In some embodiments, the template material is further charged with a dehydration agent prior to step (b), hi some further embodiments, the dehydration agent is selected from the group consisting of sulfuric acid, formic acid, acetic acid, and citric acid.

[0042] In some embodiments, for step (b), the removal of moisture and volatile substances is performed by heating. In some further embodiments, for step (b), the filled template material obtained from step (a) is heated at about 100°C, then at about 160°C to remove moisture and volatile substances therefrom. This process also serves to initiate polymerization between carbon and heteroatom dopant precursors. In some exemplary embodiments, for step (b), the filled template material obtained from step (a) is heated at about 100°C for about 6 hours, then at about 160°C for about 6 hours to remove moisture and volatile substances therefrom.

[0043] In some embodiments, for step (c), the activator is selected from the group consisting of zinc compounds, phosphoric acid, potassium acetate, sodium hydroxide, potassium carbonate, ammonium carbonate, and ammonium persulfate. In some exemplary embodiments, the zinc compound is selected from the group consisting of ZnCl2 and ZnO.

[0044] In some embodiments, for step (c), the activator and the natural halloysite-kaolin nanoclay are in a weight ratio of about 1:6 to about 4:3. In some exemplary embodiments, the activator and the natural halloysite-kaolin nanoclay are in a weight ratio of about 2:3.

[0045] In some embodiments, for step (c), the activator is introduced to the composition as a dry solid.

[0046] In some embodiments, the loaded template material resulting from step (b) or the composition resulting from step (c) is subjected to milling prior to step (d), which is typically required for solid-state activation.

[0047] In some embodiments, for step (d), the composition resulting from step (c) is activated and carbonized at a temperature of about 600° C. to about 900° C. for about 5 hours. In some further embodiments, the composition resulting from step (c) is activated and carbonized at a temperature of about 800° C. for about 5 hours. In some embodiments, for step (d), the activation and carbonization are performed under an inert atmosphere, for example under an inert atmosphere.

[0048] In some embodiments, for step (e), the composition resulting from step (d) is treated with HCl to remove the activating agent and with HF to remove the template material.

[0049] In some embodiments of the second aspect, the doped activated nanoporous carbon material has a heteroatom content of from about 0.25% by weight to about 15.00% by weight.

[0050] In some embodiments, the doped activated nanoporous carbon material has a nitrogen (N) content of about 0.25% to about 15.00% by weight.

[0051] In some embodiments, the doped activated nanoporous carbon material has a sulfur (S) content of about 0.30% to about 2.28% by weight and a nitrogen (N) content of about (9.25%) to 13.19%.

[0052] In some embodiments, the doped activated nanoporous carbon material has a boron (B) content and an oxygen content of about 11.10% to 26.92%.

[0053] In some embodiments, the doped activated nanoporous carbon material has a specific capacitance greater than about 200 F / g at a current density of 0.3 A / g. In some embodiments, the doped activated nanoporous carbon material has a specific capacitance of about 299 F / g at a current density of 0.3 A / g. In some exemplary embodiments, the doped activated nanoporous carbon material has a specific capacitance of about 299 F / g, about 228 F / g, and about 194 F / g at current densities of 0.3 A / g, 0.5 A / g, and 1 A / g.

[0054] In some embodiments, the doped activated nanoporous carbon material has a molecular weight of about 1350 m. 2 / g~approx. 1700m 2 In some further embodiments, the doped activated nanoporous carbon material has a specific surface area of ​​about 1500 m 2 / g~approx. 1700m 2 In some further embodiments, the doped activated nanoporous carbon material has a specific surface area of ​​about 1600 m 2 / g~approx. 1700m 2 / g.

[0055] In some embodiments, the doped activated nanoporous carbon material has a thickness of about 1.0 cm 3 / g ~ approx. 1.6cm 3 In some further embodiments, the doped activated nanoporous carbon material has a pore volume of about 1.3 cm 3 / g ~ approx. 1.6cm 3 In some further embodiments, the doped activated nanoporous carbon material has a pore volume of about 1.4 cm 3 / g ~ approx. 1.6cm 3 / g pore volume.

[0056] In some embodiments, the doped activated nanoporous carbon material has a molecular weight of about 1700 m 2 / g and a specific area of ​​approximately 1.465 cm 3 / g pore volume.

[0057] In some embodiments, the doped activated nanoporous carbon material has a CO2 adsorption capacity of at least about 22.5 mmol / g when determined at 0° C. and 30 bar. In some further embodiments, the doped activated nanoporous carbon material has a CO2 adsorption capacity of about 24.4 mmol / g when determined at 0° C. and 30 bar.

[0058] In a third aspect, the present disclosure provides the use of the doped activated nanoporous carbon material of the first aspect or prepared by the method of the second aspect in an anode material for a sodium-ion or lithium-ion battery.

[0059] In a fourth aspect, the present disclosure provides the use of the doped activated nanoporous carbon material of the first aspect or prepared by the method of the second aspect in an electrode material of a supercapacitor.

[0060] In a fifth aspect, the present disclosure provides the use of the doped activated nanoporous carbon material of the first aspect or prepared by the method of the second aspect in CO2 adsorption.

[0061] In a sixth aspect, the present disclosure provides the use of the doped activated nanoporous carbon material of the first aspect or prepared by the method of the second aspect, for electrochemical energy storage and conversion.

[0062] In a seventh aspect, the present disclosure provides the use of the doped activated nanoporous carbon material of the first aspect or prepared by the method of the second aspect for water / wastewater treatment.

[0063] In an eighth aspect, the present disclosure provides the use of the doped activated nanoporous carbon material of the first aspect or prepared by the method of the second aspect in a fuel cell.

[0064] In a ninth aspect, the present disclosure provides the use of the doped activated nanoporous carbon material of the first aspect or prepared by the method of the second aspect as a catalytic material for thermocatalytic and / or electrocatalytic reactions.

[0065] In a tenth aspect, the present disclosure provides the use of the doped activated nanoporous carbon material of the first aspect or prepared by the method of the second aspect in a sensor, such as an enzyme biosensor.

[0066] In an eleventh aspect, the present disclosure provides the use of the doped activated nanoporous carbon material of the first aspect or prepared by the method of the second aspect, as an antibacterial agent. [Brief description of the drawings]

[0067] [Figure 1] FIG. 1 shows SEM images of natural halloysite-kaolin nanoclay samples from Streaky Bay showing 1%, 70% and 99% halloysite:kaolinite natural mixtures.

[0068] [Diagram 2] FIG. 2 illustrates an exemplary synthesis process of doped activated nanoporous carbon materials by using natural halloysite-kaolin nanoclay as a template.

[0069] [Diagram 3] FIG. 3 shows the FTIR spectra of N-doped activated nanoporous carbon materials carbonized at different temperatures (700, 800 and 900° C.) according to the present disclosure.

[0070] [Figure 4] FIG. 4 shows the XPS survey and high resolution spectrum of the N-doped activated nanoporous carbon material carbonized at 800° C. according to the present disclosure.

[0071] [Diagram 5]FIG. 5 shows an SEM image of one embodiment of an N-doped activated nanoporous carbon material carbonized at 700° C.

[0072] [Figure 6] FIG. 6 shows an SEM image of one embodiment of an N-doped activated nanoporous carbon material carbonized at 800° C.

[0073] [Figure 7] FIG. 7 shows an SEM image of one embodiment of an N-doped activated nanoporous carbon material carbonized at 900° C.

[0074] [Figure 8] Figure 8 shows a) CO2 adsorption isotherms of N-ANCx samples measured in the pressure range of 0-30 bar, b) CO2 adsorption isotherms of N-ANC800 measured at three different temperatures of 0, 10 and 25 °C and at a common pressure range of 0-30 bar, c) isosteric heats of adsorption of N-ANCx samples calculated from the adsorption isotherms obtained at three different temperatures of 0, 10 and 25 °C, and d) comparison of N-ANC800 with K-HNT and other porous carbon materials: HNC derived from K-HNT - porous carbon; N-HNC800 - N-doped porous carbon derived from K-HNT without activation.

[0075] [Figure 9] Figure 9 shows the cyclic voltammograms (CV) of the samples, (a) N-ANC700, (c) N-ANC800 and (e) N-ANC900, measured at a scan rate range of 5–100 mV s-1; galvanostatic charge / discharge (GCD) measurements of the N-ANCx samples, (b) N-ANC700, (d) N-ANC800 and (f) N-ANC900, measured at different current densities ranging from 0.3 to 10 A g-1.

[0076] [Figure 10]Figure 10 shows the specific capacitance data of N-ANCX, (a) cyclic voltammograms (CV) of the samples measured at a scan rate of -10 mV s-1, (b) galvanostatic charge / discharge (GCD) measurements of the N-ANCx samples measured at a current density of 1 A g-1, (c) Nyquist plots of the N-ANCx samples measured at 0.1 hz, and (d) specific capacitance values ​​(Cs) of the N-ANCx samples measured at various current densities.

[0077] [Figure 11] Figure 11 shows the galvanostatic charge / discharge (GCD) measurements of the B-ANCx samples measured at different current densities of 0.5 A g-1 and the cyclic voltammograms (CV) of the samples measured at a scan rate range of 10 mV s-1.

[0078] [Figure 12] FIG. 12 shows the charge and discharge capacity profiles for the 1st, 2nd, 5th and 50th cycles at a current density of 100 mAh g-1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0079] As used herein, the term "nanoporous" refers to pore sizes that are generally less than or equal to 100 nanometers.

[0080] The term "activated," when referring to a carbon material in this disclosure, means that the carbon material has been treated to exhibit small, low volume pores that increase the surface area available for adsorption or ion transport.

[0081] The phrase "natural halloysite-kaolin nanoclay" as used herein refers to low-cost, naturally available clay materials that can be used with or without purification. Examples of these materials are shown in Figure 1. Natural halloysite-kaolin nanoclay is a hybrid blend of halloysite Al2Si2O5(OH)4-2H2O and kaolinite Al2Si2O5(OH)4 clay minerals. Kaolinite has the formula Al2Si2O5(OH)4 and typically exists in a plate-like morphology. Halloysite has a similar composition to kaolinite, except that it contains additional water molecules between the layers and exhibits a nanotube morphology. Halloysite loses its interlayer water very easily and can exist in a partially dehydrated state. Halloysite exists as long tubes with large lumens, the lumens being the inside of the tubes similar to the inside of a straw. For example, natural halloysite-kaolin nanoclay is readily available in the Western region of South Australia. Figure 1 shows an SEM image of a natural halloysite-kaolin nanoclay sample from a deposit in Western South Australia. Natural halloysite-kaolin nanoclay as used herein may contain variable ratios of halloysite and kaolinite, but generally more than about 40% halloysite nanotubes, and up to more than about 80% halloysite nanotubes. Kaolinite, once exfoliated, has a flaky structure that is beneficial for synthesizing N-doped porous carbon with flaky structure, together with the halloysite nanotubes. In other words, the flaky structure of kaolinite, together with the nanotube structure of halloysite, is replicated in N-doped activated nanoporous carbon during the carbonization procedure. The flaky structure of N-doped activated nanoporous carbon provides additional channels for faster diffusion / transport of ions during electrochemical manipulation or adsorption of gases. Furthermore, the availability of natural halloysite-kaolin nanoclay as a template offers the added advantage of low cost and abundance compared to conventional templates such as silica.

[0082] The present invention arises from our finding that halloysite-kaolin nanoclay with a mixture of flake and tubular morphologies can act as a template enabling its morphological features to be replicated in carbon materials, and a simple solid-state one-step activation combined with a template process can be employed to fabricate N-doped activated nanoporous carbon materials with desirable performance in specific capacity, CO2 adsorption, charge and discharge capacity.

[0083] Carbon hosts can be modified by doping with heteroatoms such as phosphorus, boron, sulfur and nitrogen. The introduction of nitrogen improves the electron density or increases the basicity of the carbon framework, which is then believed to anchor the electron-deficient carbon of CO2 to the carbon pore surface via Lewis acid / Lewis base (N atom) interactions.

[0084] However, it has been difficult to control the nitrogen functionality on the surface of nanoporous carbon materials. The post-treatment approaches generally involve complicated processes and the use of toxic nitrogen precursors, such as ammonia or melamine. Also, the porous carbon materials treated with N-containing precursors, such as ammonia and melamine, are less favorable for controlling the dopant distribution and porosity. In addition, the post-treatment approaches can easily collapse the porous structure. In contrast to the post-treatment approaches, the template strategy is now widely adopted to synthesize ordered heteroatom-doped porous carbon with heteroatom-containing carbon precursors or mix them with other carbon sources. This approach also allows the control of the nitrogen content in the final material without using toxic precursors / gases. Nevertheless, it remains difficult to develop an effective strategy to fabricate heteroatom-doped porous carbon with both large surface area and high heteroatom doping.

[0085] It has been found by the inventors that the process disclosed herein can be used to functionalize the surface of nanoporous carbon materials, with the advantage of improving performance in applications such as batteries. Furthermore, the carbonization temperature can be used to tailor the nitrogen content and textural properties of the final product to determine the final performance in electrochemical and adsorption applications.

[0086] Thus, provided herein is a doped activated nanoporous carbon material prepared from a template material comprising natural halloysite-kaolin nanoclay, a carbon precursor, a heteroatom dopant precursor and an activator, the doped activated nanoporous carbon material exhibiting flake and nanotube morphology and having surface heteroatom functionality.

[0087] A method for preparing a doped activated nanoporous carbon material comprising the steps of: (a) loading a template material comprising natural halloysite-kaolin nanoclay with a carbon precursor and a heteroatom dopant precursor; (b) removing moisture and volatiles from the filled template material resulting from step (a); (c) preparing a composition comprising the filled template material obtained from step (b) and an activator; (d) activating and carbonizing the composition resulting from step (c) at a temperature of about 600° C. to about 900° C.; and (e) removing the template material and the activator from the composition resulting from step (d). Also provided herein are methods, including:

[0088] In general, doped activated nanoporous carbon materials are prepared from a template material comprising natural halloysite-kaolin nanoclay by a sacrificial hard template method combined with activation and simple in-situ doping. In some embodiments, the template material consists of natural halloysite-kaolin nanoclay.

[0089] Natural halloysite-kaolin nanoclay is low cost and naturally available, for example, from the Western Region of South Australia. For the purposes of this disclosure, halloysite-kaolin nanoclay can be used immediately after extraction and does not require purification. For example, the halloysite-kaolin nanoclay used herein is commercially available under the trademark ParlaWhite®.

[0090] It is possible to use natural halloysite-kaolin nanoclays containing more than about 40% halloysite nanotubes. In some embodiments, the natural halloysite-kaolin nanoclays contain more than about 80% halloysite nanotubes. It has been found that the natural halloysite-kaolin nanoclays act as templates such that the flake-like structure of the kaolin can be replicated in the doped activated nanoporous carbon material as slit-like pores, and the tube walls of the halloysite are replicated in the doped activated nanoporous carbon material as mesoporous structures. This mechanism is shown in FIG. 2.

[0091] The selection of the carbon precursor may take into consideration high carbon content, cost-effectiveness, and susceptibility to dehydration at relatively low temperatures. In this regard, the carbon precursor used herein may be a carbohydrate-based compound, such as a sugar-based compound, or a mixture thereof. Specifically, the sugar-based compound may include sucrose, glucose, fructose, polysaccharides. If desired, the sugar-based compound may be sourced from materials such as waste fruit juice / pulp and waste carbonated sugar-containing beverages. Examples of polysaccharides include, but are not limited to, cellulose, chitosan, and starch. In a preferred embodiment, sucrose is used as the carbon precursor. It is believed that the heat treatment of the natural halloysite-kaolin nanoclay template with sucrose helps to establish bonds between the outer surface of the nanoclay and the sucrose molecules. This results in the coating of the surface of the nanoclay with carbon derived from sucrose. Furthermore, sucrose is a low-cost, non-toxic, and abundantly available carbon precursor. Sucrose is commercially available, for example, from Sigma-Aldrich with a purity of 99.5% or higher. To prepare doped activated nanoporous carbon materials, the carbon precursor and template material (e.g., natural halloysite-kaolin nanoclay) can be in a weight ratio of about 2:10 to about 4:10, for example, 2:10, 2.5:10, 3:10, 3.5:10, and 4:10. In a preferred embodiment, the carbon precursor and template material are in a weight ratio of about 3:10.

[0092] A heteroatom dopant can be any suitable atom that is not carbon or hydrogen. Non-limiting examples include, but are not limited to, nitrogen (N), sulfur (S), oxygen (O) and boron (B). As used herein, the term "dopant" refers to an impurity that is intentionally introduced into an intrinsic carbon framework for the purpose of adjusting one or more properties of a material, such as its electrical, optical or structural properties. For the purposes of this disclosure, a distinction can be made between "doping", which involves incorporating heteroatoms into the crevices of the carbon framework so that the heteroatoms are intrinsically incorporated into the carbon framework, and "filling", which involves filling the interstitial spaces within the carbon framework with heteroatoms. Those skilled in the art will understand that doping and filling result in different properties in the final material.

[0093] Any suitable heteroatom dopant precursor may be used. Nitrogen precursors with tightly bound nitrogen may not release nitrogen atoms for chemical reaction during thermal carbonization, whereas precursors that can easily donate nitrogen at relatively low temperatures may be desirable for the present disclosure. Furthermore, solid nitrogen-containing precursors that are cost-effective, easy to handle, and contain high content of nitrogen compared to liquid and gaseous nitrogen precursors are suitable for this purpose. The nitrogen precursor used herein may be a compound containing one or more nitrogen atoms. Non-limiting examples of nitrogen precursors include aminoguanidine, aminoguanidine hydrochloride, aminotriazole, urea, chitosan, cyanamide, dicyanamide, thiourea, melamine, casein, polyaniline, polypyrrole, aminotetrazole, and aminotriazine. In some embodiments, the nitrogen precursor is aminotriazole. In certain exemplary embodiments, the nitrogen precursor is 3-amino-1,2,4-triazole. The nitrogen precursor may be a compound containing one or more nitrogen atoms and one or more other heteroatoms, such as sulfur. Suitable nitrogen precursors in this regard include thiourea, thioacetamide, L-cysteine, methionine, dithiocarbamates, dithiooxamides, thiazoles such as 2-aminothiazole, 5-amino-1,3,4-thiadiazole-2-thiol, thiosemicarbazide and thiocarbohydrazide.

[0094] To provide S-doped activated nanoporous carbon materials, sulfur precursors can be used as heteroatom dopant precursors. The sulfur precursors can be carbon compounds containing one or more sulfur atoms, such as diphenyl disulfide, polyphenylene sulfide, bis(trimethylsilyl) sulfide, alkylthiols, and thiophenes. The sulfur precursors can be inorganic compounds containing one or more sulfur atoms, such as sulfur powder, sodium sulfide, sodium dithionite, and sodium thiosulfate. Alternatively, the sulfur precursors can be carbon-containing compounds containing one or more sulfur atoms and one or more other heteroatoms, such as nitrogen. For example, the sulfur precursors can be selected from the group consisting of thiourea, thioacetamide, L-cysteine, methionine, dithiocarbamate, dithiooxamide, thiazoles, such as 2-aminothiazole, 5-amino-1,3,4-thiadiazole-2-thiol, thiosemicarbazide, and thiocarbohydrazide.

[0095] To provide B-doped activated nanoporous carbon materials, boron precursors can be used as heteroatom dopant precursors. The boron precursor can be a compound containing one or more boron atoms, such as boric acid, ammonia borane (borazane), diborane, trimethylboron, koulmanite, boron trioxide, trimethoxyborane, sodium borate, borax, sodium borohydride, dimeric diborazane, trimeric triborazane, boron trifluoride, boron trichloride, phenyl borate.

[0096] To provide O-doped activated nanoporous carbon materials, an oxygen precursor can be used as a heteroatom dopant precursor. The oxygen precursor can be a compound containing one or more oxygen atoms, such as boric acid, boron trioxide, sodium borate, and borax.

[0097] Heteroatom dopant precursors may be sulfur and nitrogen precursors such as thiourea, thioacetamide, L-cysteine, methionine, dithiocarbamates, dithiooxamides, thiazoles such as 2-aminothiazole, 5-amino-1,3,4-thiadiazole-2-thiol, thiosemicarbazide and thiocarbohydrazide.

[0098] Heteroatom dopant precursors may be boron and oxygen precursors, such as boric acid, boron trioxide, sodium borate, and borax.

[0099] The amount of heteroatom dopant precursor varies based on the specific surface area and pore volume of the halloysite template and the purity of the template. In some embodiments, the heteroatom dopant precursor and the template material (e.g., natural halloysite-kaolin nanoclay) are in a weight ratio of about 1:12 to about 1:4. In some exemplary embodiments, the heteroatom dopant precursor and the template material are in a weight ratio of about 1:10.

[0100] For step (a), the heteroatom dopant precursor and the carbon precursor can be loaded into the template material in various ways, for example, by impregnation. For this purpose, a solution of the carbon precursor and a solution of the heteroatom dopant precursor are prepared separately and then impregnated into the template material. Preferably, an aqueous solution of the carbon precursor and an aqueous solution of the heteroatom dopant precursor are prepared separately and then dripped onto the template material. The amount of water used is optimized to allow complete diffusion of the carbon precursor and the heteroatom dopant precursor within the template material, since if too much water is added, polymerized carbon material may form on the outer surface of the template, but not too much to be removed during the subsequent step (b). In certain of these embodiments, the water and the template material (e.g., natural halloysite-kaolin nanoclay) used to prepare the solution are in a weight ratio of about 1:1 to about 2:1. In some exemplary embodiments, the water and the template material used to prepare the solution are in a weight ratio of about 4:3.

[0101] The amount of water used is optimized to achieve complete diffusion of the precursors within the nanochannels of the template material, particularly the natural halloysite-kaolin nanoclay. In some embodiments, the ratio of precursors (i.e., carbon precursor + nitrogen precursor) to water ranges from about 1:2.5 to about 1:6 by weight, preferably about 12:40 by weight. Preferably, a dehydrating agent is also applied to the template material. This can be achieved by introducing the dehydrating agent into an aqueous solution of the sugar-based compound. Suitable dehydrating agents include, but are not limited to, sulfuric acid, formic acid, acetic acid, and citric acid. The amount of dehydrating agent used is readily determined by the amount of carbon and nitrogen precursors used in the template.

[0102] The present disclosure uses an in-situ doping approach, where the carbon precursor and heteroatom dopant precursor are combined prior to heat treatment, which is believed to be advantageous over post-treatment approaches, where the heteroatom dopant precursor is added to already carbonized porous carbon, since the former allows for a uniform distribution of heteroatoms on the porous carbon, whereas the latter can disrupt the structure of the carbon precursor, resulting in changes in pore size and morphology.

[0103] In addition, it has been proposed to further charge the template material with a dehydrating agent to aid in the dehydration of the carbon precursor. For example, a dehydrating agent can be added to the carbon precursor solution for impregnation. The dehydrating agents used herein include sulfuric acid and organic acids, such as formic acid, acetic acid, or citric acid. The amount of dehydrating agent of the carbon precursor and heteroatom dopant precursor added to the template material can have the advantage of increasing the mass yield of carbon after carbonization and reducing the sample shrinkage during carbonization.

[0104] If desired, the filled template material formed from the template material, the carbon precursor, the heteroatom dopant precursor and other components, such as a dehydrating agent (if present), can then be thoroughly mixed.

[0105] Moisture and volatiles are removed from the resulting filled template material without significant decomposition by heating at 100C for 6 hours and then at 160C for 6 hours. This process also serves to initiate polymerization between the carbon and heteroatom dopant precursors. For this purpose, the filled template material obtained from step (a) can be subjected to a low-temperature heat treatment, for example using a hot air oven or a vacuum oven. In some embodiments, for step (b), the filled template material is heated at about 100C and then at about 160C. In some exemplary embodiments, for step (b), the filled template material is heated at about 100C for about 6 hours and then at about 160C for about 6 hours.

[0106] To achieve simultaneous activation and carbonization, the filled template material is combined with an activator. The combination of the heteroatom dopant precursor with an activator significantly increases the pore size of the final product.

[0107] The type of activator can be used to control the nature of the porosity of the doped activated nanoporous carbon material. In some embodiments, the activator is selected from zinc compounds, phosphoric acid, potassium acetate, sodium hydroxide, potassium carbonate, ammonium carbonate, and ammonium persulfate. In some exemplary embodiments, the zinc compound can be selected from ZnCl2 and ZnO. The amount of activator plays a role in achieving some properties of the activated doped nanoporous carbon material, such as surface area, microporous area, and micropore volume. In some embodiments, the activator and template material (e.g., natural halloysite-kaolin nanoclay) are in a weight ratio of about 1:6 to about 4:3. In some exemplary embodiments, the activator and template material are in a weight ratio of about 2:3.

[0108] The activator can be combined with the loaded template material in a dry or solid state. In a preferred embodiment, for step (c), the activator in a dry solid form is combined with the loaded template material. If necessary, the loaded template material processed as described above can be ground into a fine powder before combining with the loaded template material. The solid state procedure has been demonstrated to be more favorable for producing carbon materials with better characteristics than the liquid state or than cases involving immersion of the precursor in a solution of the activator. The solid state procedure also eliminates the need for an additional step of evaporating the solution to dryness before high temperature carbonization.

[0109] It is worth mentioning that in the present disclosure, activation and carbonization are carried out simultaneously, making the preparation process simple and cost-effective. The combined activation and carbonization procedure eliminates the time requirements required for the traditional two-step procedure. This is a more preferred procedure in lieu of considerations such as the energy and labor consumed in the process.

[0110] The composition prepared as described above, including the template material, the carbon precursor, the heteroatom dopant precursor, the activator, and other components such as the dehydrating agent, if present, are then subjected to activation and carbonization at a temperature of about 600°C to about 900°C for step (d). The activation and carbonization can be carried out under an inert atmosphere, such as a nitrogen atmosphere. In some embodiments, the composition is activated and carbonized at a temperature of about 600°C to about 900°C for about 5 hours. Preferably, the composition is activated and carbonized at a temperature of about 800°C. It is believed that the reduction in texture features can be minimized and the activator can exert its full effect at a temperature of about 800°C.

[0111] The activation and carbonization process begins with the polymerization of carbon chains. These carbon chains may undergo breaking, modification, further polymerization, aromatization, etc., ultimately resulting in the production of doped activated nanoporous carbon around the nanoclays. The nanoclays themselves may undergo atomic rearrangements / partial collapse of their structure, but it is speculated that this will not affect their structure too significantly. During carbonization, the carbon precursors enter the empty lumens of the available tubular structures and replicate the tubular structures in the carbon.

[0112] After activation and carbonization, the template material and activator need to be removed from the composition. The activator can be removed by washing with HCl or water, for example by using a 2M HCl solution. The template material can be removed by washing with HF, for example by using a dilute HF solution. In order to completely remove the activator, it is preferable to rinse the composition with water (e.g., distilled water) after the HCl treatment. In some embodiments, the activated and carbonized composition is washed with an HCl solution (e.g., for 2 hours), then rinsed with water, after which the composition is washed with a dilute HF solution (e.g., 5 wt%). This may be followed by filtration, washing with excess ethanol, and then drying to remove most of the impurities from the doped activated nanoporous carbon material.

[0113] Various features such as elemental composition, morphology, specific capacity, specific surface, pore volume, and charge and discharge profiles can be used to characterize the doped activated nanoporous carbon materials obtained as described above.

[0114] In the following description, reference is made to N-doped materials for illustrative purposes only, other heteroatom-doped materials can also be used and tested, if desired, including S-doped and B-doped activated nanoporous carbon materials.

[0115] elemental composition

[0116] The elemental composition of the N-doped activated nanoporous carbon materials can be estimated using a CHNS / O elemental analyzer. Elemental analysis of the N-doped activated nanoporous carbon materials shows that the carbonization temperature strongly affects the carbon and nitrogen contents of the final materials. The carbon and nitrogen contents are different for materials carbonized at different temperatures. Since high temperatures can cause the evaporation of nitrogen species, the nitrogen content in the carbon framework gradually decreases as the carbonization temperature increases from 600 °C to 900 °C. However, the nitrogen content in the carbon framework of the material carbonized at 800 °C (about 10%) is relatively higher than other N-doped materials reported so far (Zhou et al. 2018; Lu et al. 2017; Kim et al. 2019; Zou et al. 2019).

[0117] In some embodiments, the N-doped activated nanoporous carbon material has a nitrogen content of about 0.25% to about 15.00% by weight.

[0118] Figure 3 shows the FTIR spectra of N-doped nanoporous carbon materials synthesized at different temperatures (600, 700, 800 and 900 °C). The C=N bond (approximately 1600 cm -1 ) and NH bonds (approx. 1300 cm -1 Nitrogen in the form of N-doped nanoporous carbon nanotubes (N-doped nanoparticles) is clearly observed on the surface of the material samples. The uniform N-doping of the porous carbon framework enhances wettability in aqueous solutions and provides redox sites, which is believed to play a role in the exceptional performance of the N-doped activated nanoporous carbon materials disclosed herein. Furthermore, the surface nitrogen functionality enhances the surface charge and wettability, thereby facilitating the carbon capture and energy storage performance.

[0119] High temperature nitrogen species such as quaternary nitrogen and pyridine-N-oxide are found on the surface of N-doped activated nanoporous carbon materials, which can be attributed to the high activation temperature used in the process disclosed herein. This can be seen in Figure 4. The amount of nitrogen can be controlled by adjusting the carbonization temperature, since the thermodynamic stability of N in carbon materials is very low.

[0120] form

[0121] Morphological analysis can be performed using FE-SEM and HRTEM. From Figures 5-7, it is observed that the morphology of the materials disclosed herein exhibited a sheet-like structure with porosity composed of numerous uniformly distributed flake-like and tubular particles. These reveal that the morphological features of the template are replicated in the N-doped activated nanoporous carbon material. The N-doped activated porous carbon material carbonized at 900°C exhibited an aggregated morphology of flake-sheet-like morphology (see, for example, Figure 7). It is hypothesized that they aggregated together via simple siloxane bridges at high temperature.

[0122] CO2 adsorption capacity

[0123] A Micromeritics HPVA instrument equipped with a temperature controlled circulator can be used to measure the high pressure CO2 adsorption capacity of the N-doped activated nanoporous carbon material disclosed herein. Adsorption isotherms were recorded at temperatures of 0 °C, 10 °C and 25 °C using a pressure range of 0 to 30 bar. Prior to analysis, the samples were degassed under constant vacuum for 12 hours at a temperature of 200 °C. The results from the CO2 adsorption isotherms shown in Figure 8(d) suggest that the N-doped activated nanoporous carbon material disclosed herein exhibits superior CO2 adsorption capacity compared to the carbon material without doping or activation. From the adsorption isotherms, it can be observed that the N-doped activated nanoporous carbon material disclosed herein exhibits an initial sharp increase in CO2 adsorption followed by a linear increase at higher pressures (pressures of 5 to 30 bar). This clearly demonstrates the robustness of the porous structure of the N-doped activated nanoporous carbon material, which does not collapse even at a higher pressure of 30 bar. In the low pressure regime, the active microporous sites on the surface are filled first, and as the pressure is increased, the CO2 molecules also fill the inner mesoporous centres of the carbon structure.

[0124] In some embodiments, the N-doped activated nanoporous carbon material has a CO2 adsorption capacity of at least about 22.5 mmol / g, determined at 0° C. and 30 bar. In some further embodiments, the N-doped activated nanoporous carbon material has a CO2 adsorption capacity of about 24.4 mmol / g, determined at 0° C. and 30 bar. It is clear from FIG. 8 that the CO2 adsorption capacity of the N-doped activated nanoporous carbon material is higher than that of the non-activated porous carbon material without N doping (about 13.1 mmol / g). At a low pressure of about 1 bar, the adsorption capacity of the N-doped activated nanoporous carbon material is about 3.9 mmol / g, which is relatively better than that of the non-activated nanoporous carbon material without N doping (about 2.4 mmol / g). The CO2 adsorption of N-ANCx was compared with nitrogen-functionalized mesoporous carbon, N-doped activated carbon, and mesoporous carbon nitride (Table 2). The data revealed that N-ANCx had higher CO2 adsorption capacity than the comparative materials due to its superior textural properties and nitrogen doping.

[0125] The specific surface area and pore volume of the material are analyzed by measuring the N2 adsorption and desorption isotherms at -196°C. The measurements can be performed using a micromeritics ASAP 2420 surface area and porosity analyzer. The specific surface area can be determined by utilizing the Brunauer-Emmett-Teller (BET) model. The N-doped activated nanoporous carbon material disclosed herein has a specific surface area of ​​about 1350 m 2 ·g -1 ~about 1700m 2 ·g -1 In some embodiments, the N-doped activated nanoporous carbon material has a specific surface area in the range of about 1500 m 2 ·g -1 ~about 1700m 2 ·g -1 , preferably about 1600m 2 ·g -1 ~about 1700m 2 ·g -1Additionally or alternatively, the N-doped activated nanoporous carbon material disclosed herein has a specific surface area of ​​about 1.000 cm 3 / g ~ approx. 1.600cm 3 In some embodiments, the N-doped activated nanoporous carbon material has a pore volume of about 1.300 cm 3 / g ~ approx. 1.600cm 3 / g, preferably about 1.400 cm 3 / g ~ approx. 1.600cm 3 In a preferred embodiment, the N-doped activated nanoporous carbon material disclosed herein has a specific surface area of ​​about 1700 m 2 ·g -1 and a specific surface area of ​​about 1.465 cm 3 The pore volume in g / g is shown. It is believed that the higher surface area and relatively high pore volume contribute greatly to the higher CO2 adsorption capacity. In addition, the high degree of surface functional groups further contributes to the higher CO2 adsorption capacity.

[0126] The CO2 adsorption properties of N-ANC and other reported porous carbon materials are shown in Table 1.

[0127] Table 1 - Comparison of the performance of N-ANC and other reported porous carbon materials as CO2 high-pressure solid adsorbents. [Table 1]

[0128] Note that CPC-3 is a porous carbon derived from sassane; N-HPC is an N-doped hierarchical porous carbon derived from dicyandiamide and phenolic resin; and G-3.6-1 is an N-doped activated porous carbon derived from glucose, potassium oxalate, and melamine.

[0129] Specific Capacity / Charge and Discharge Profile

[0130] The specific capacity of activated porous carbon (AHNC) derived from halloysite nanotubes without N-doping (see Kavitha Ramadass; CI Sathish; Sujanya Maria Ruban; Gopalakrishnan Kothandam; Stalin Joseph; Gurwinder Singh; Sungho Kim; Wangsoo Cha; Ajay Karakoti; Tony Belperio; Jia Bao Yi; and Ajayan Vinu. Carbon Nanoflakes and Nanotubes from Halloysite Nanoclays and their Superior Performance in CO2 Capture and Energy Storage. ACS Applied Materials&Interfaces 2020 12(10),11922-11933) is relatively lower than the specific capacity of the N-doped activated nanoporous carbon materials disclosed herein. Specifically, the N-doped activated nanoporous carbon material carbonized at 800° C. exhibits a specific capacitance of about 299 F / g at a current density of 0.3 A / g, which is higher than the specific capacitance of AHNC (about 192 F / g). This means that the N-doped activated nanoporous carbon material disclosed herein can store higher energy compared to AHNC, thus suggesting its high potential as a supercapacitor electrode material. In some embodiments, the N-doped activated nanoporous carbon material disclosed herein can have a specific capacitance of more than about 200 F / g at a current density of 0.3 A / g. In some further embodiments, the N-doped activated nanoporous carbon material has a specific capacitance of about 299 F / g at a current density of 0.3 A / g. In some exemplary embodiments, the N-doped activated nanoporous carbon material has a specific capacitance of about 299 F / g, about 228 F / g, about 194 F / g at current densities of 0.3 A / g, 0.5 A / g, and 1 A / g.

[0131] The electrical conductivity, specific surface area, large pore volume and surface nitrogen functionality of the N-doped activated nanoporous carbon materials disclosed herein promote efficient ion / electron transport, which can lead to the formation of more Na+ The N-doped activated nanoporous carbon materials disclosed herein also exhibit good charge storage capability at scan rates as high as 100 mV / s (see, e.g., FIG. 10) and good cycling stability (see, e.g., FIG. 11). Specifically, such electrodes exhibit promising capacity retention after 200 cycles measured at 0.1 A / g. As a result of these properties, the N-doped activated nanoporous carbon materials disclosed herein are well suited for high-performance sodium-ion or lithium-ion batteries.

[0132] As shown in Table 2, it was found that the stabilization of the electrochemical properties occurred more quickly for the N-doped activated nanoporous carbon materials than for the nitrogen-free activated nanoporous carbon samples.

[0133] Table 2-N-ANC 900 Comparison of supercapacitance values ​​with previously reported materials [Table 2]

[0134] Here, NCNF is nitrogen-doped carbon nanofiber; CPC-3 is casein-derived porous carbon; and CP-NA is coffee waste-derived nitrogen-doped carbon.

[0135] It will be apparent from the foregoing description and the following examples that there is provided herein a doped activated nanoporous carbon material prepared from a template material comprising natural halloysite-kaolin nanoclay, a carbon precursor, a heteroatom dopant precursor and an activator, the doped activated nanoporous carbon material exhibiting flake and nanotube morphology and having surface heteroatom functionality.

[0136] In a particular embodiment, the template material consists of natural halloysite-kaolin nanoclay.

[0137] In certain embodiments, the natural halloysite-kaolin nanoclay contains greater than 40% by weight of halloysite nanotubes.

[0138] In certain embodiments, the natural halloysite-kaolin nanoclay contains greater than 80% by weight of halloysite nanotubes.

[0139] In certain embodiments, the carbon precursor is a carbohydrate-based compound.

[0140] In certain embodiments, the carbon precursor is selected from a sugar-based compound.

[0141] In certain embodiments, the sugar-based compound is selected from the group consisting of sucrose, glucose, fructose and polysaccharides.

[0142] In certain embodiments, the polysaccharide is selected from the group consisting of cellulose, chitosan and starch.

[0143] In certain embodiments, the heteroatom dopant precursor is a compound that includes multiple heteroatoms.

[0144] In certain embodiments, the heteroatom dopant precursor is selected from one or more of the group consisting of a nitrogen precursor, a sulfur precursor, a boron precursor, and an oxygen precursor.

[0145] In certain embodiments, the nitrogen precursor is selected from the group consisting of aminoguanidine, aminoguanidine hydrochloride, aminotriazole, urea, chitosan, cyanamide, dicyanamide, thiourea, melamine, casein, polyaniline, polypyrrole, aminotetrazole, and aminotriazine.

[0146] In certain embodiments, the nitrogen precursor is an aminotriazole.

[0147] In certain embodiments, the nitrogen precursor is 3-amino-1,2,4-triazole.

[0148] In certain embodiments, the sulfur precursor is selected from one or more of the group consisting of diphenyl disulfide, polyphenylene sulfide, bis(trimethylsilyl) sulfide, alkylthiols, thiophenes, sulfur powder, sodium sulfide, sodium dithionite, sodium thiosulfate, thiourea, thioacetamide, L-cysteine, methionine, dithiocarbamates, dithiooxamides, thiazoles such as 2-aminothiazole, 5-amino-1,3,4-thiadiazole-2-thiol, thiosemicarbazide, and thiocarbohydrazide.

[0149] In certain embodiments, the boron precursor is selected from one or more of the group consisting of boric acid, ammonia borane (borazane), diborane, trimethylboron, koulmanite, or boron trioxide, trimethoxyborane, sodium borate, borax, sodium borohydride, dimeric diborazane, trimer triborazane, boron trifluoride, boron trichloride, and phenyl borate.

[0150] In certain embodiments, the oxygen precursor is selected from one or more of the group consisting of boric acid, boron trioxide, sodium borate, and borax.

[0151] In certain embodiments, the heteroatom dopant precursors are sulfur and nitrogen precursors, such as thiourea, thioacetamide, L-cysteine, methionine, dithiocarbamates, dithiooxamides, thiazoles, such as 2-aminothiazole, 5-amino-1,3,4-thiadiazole-2-thiol, thiosemicarbazide, and thiocarbohydrazide.

[0152] In certain embodiments, the heteroatom dopant precursors are boron and oxygen precursors, such as boric acid, boron trioxide, sodium borate, and borax.

[0153] In certain embodiments, the activator is selected from the group consisting of zinc compounds, phosphoric acid, potassium acetate, sodium hydroxide, potassium carbonate, ammonium carbonate, and ammonium persulfate.

[0154] In certain embodiments, the zinc compound is selected from the group consisting of ZnCl2 and ZnO.

[0155] In certain embodiments, the doped activated nanoporous carbon material has a heteroatom content of about 0.25% to about 15.00% by weight.

[0156] In certain embodiments, the doped activated nanoporous carbon material has a specific capacitance greater than about 200 F / g at a current density of 0.3 A / g.

[0157] In a particular embodiment, the doped activated nanoporous carbon material has a specific capacitance of about 299 F / g at a current density of 0.3 A / g.

[0158] In certain embodiments, the doped activated nanoporous carbon materials have specific capacitances of about 299 F / g, about 228 F / g, and about 194 F / g at current densities of 0.3 A / g, 0.5 A / g, and 1 A / g.

[0159] In a particular embodiment, the doped activated nanoporous carbon material has a molecular weight of about 1350 m 2 / g~approx. 1700m 2 / g.

[0160] In a particular embodiment, the doped activated nanoporous carbon material has a molecular weight of about 1500 m 2 / g~approx. 1700m 2 / g.

[0161] In a particular embodiment, the doped activated nanoporous carbon material has a molecular weight of about 1600 m 2 / g~approx. 1700m 2 / g.

[0162] In a particular embodiment, the doped activated nanoporous carbon material has a thickness of about 1.000 cm 3 / g ~ approx. 1.600cm 3 / g pore volume.

[0163] In a particular embodiment, the doped activated nanoporous carbon material has a surface area of ​​about 1,300 cm 3 / g ~ approx. 1,600cm 3 / g pore volume.

[0164] In a particular embodiment, the doped activated nanoporous carbon material has a surface area of ​​about 1,400 cm 3 / g ~ approx. 1,600cm 3 / g pore volume.

[0165] In certain embodiments, the doped activated nanoporous carbon material has a CO2 adsorption capacity of at least about 22.5 mmol / g, determined at 0° C. and 30 bar.

[0166] In a particular embodiment, the doped activated nanoporous carbon material has a CO2 adsorption capacity of about 24.4 mmol / g, determined at 0° C. and 30 bar.

[0167] A method for preparing a doped activated nanoporous carbon material comprising the steps of: (a) loading a template material comprising natural halloysite-kaolin nanoclay with a carbon precursor and a heteroatom dopant precursor; (b) removing moisture and volatiles from the filled template material resulting from step (a); (c) preparing a composition comprising the filled template material obtained from step (b) and an activator; (d) activating and carbonizing the composition resulting from step (c) at a temperature of about 600° C. to about 900° C.; and (e) removing the template material and the activator from the composition resulting from step (d). It will be apparent from the foregoing description and examples below that methods are provided herein, including:

[0168] In a particular embodiment, the template material consists of natural halloysite-kaolin nanoclay.

[0169] In certain embodiments, the natural halloysite-kaolin nanoclay contains greater than 40% by weight of halloysite nanotubes.

[0170] In certain embodiments, the natural halloysite-kaolin nanoclay contains greater than 80% by weight of halloysite nanotubes.

[0171] In certain embodiments, for step (a), the carbon precursor is a carbohydrate-based compound.

[0172] In certain embodiments, the carbohydrate-based compound is a sugar-based compound.

[0173] In certain embodiments, the sugar-based compound is selected from the group consisting of sucrose, glucose, fructose and polysaccharides.

[0174] In certain embodiments, the polysaccharide is selected from the group consisting of cellulose, chitosan and starch.

[0175] In certain embodiments, for step (a), the heteroatom dopant precursor is a carbon compound containing multiple heteroatoms.

[0176] In certain embodiments, the heteroatom dopant precursor is selected from one or more of the group consisting of a nitrogen precursor, a sulfur precursor, a boron precursor, and an oxygen precursor.

[0177] In certain embodiments, the nitrogen precursor is selected from the group consisting of aminoguanidine, aminoguanidine hydrochloride, aminotriazole, urea, chitosan, cyanamide, dicyanamide, thiourea, melamine, casein, polyaniline, polypyrrole, aminotetrazole, and aminotriazine.

[0178] In certain embodiments, the nitrogen precursors are selected from aminotriazoles.

[0179] In certain embodiments, the nitrogen precursor is 3-amino-1,2,4-triazole.

[0180] In certain embodiments, the sulfur precursor is selected from one or more of the group consisting of diphenyl disulfide, polyphenylene sulfide, bis(trimethylsilyl) sulfide, alkylthiols, thiophenes, sulfur powder, sodium sulfide, sodium dithionite, sodium thiosulfate, thiourea, thioacetamide, L-cysteine, methionine, dithiocarbamates, dithiooxamides, thiazoles such as 2-aminothiazole, 5-amino-1,3,4-thiadiazole-2-thiol, thiosemicarbazide, and thiocarbohydrazide.

[0181] In certain embodiments, the boron precursor is selected from one or more of the group consisting of boric acid, ammonia borane (borazane), diborane, trimethylboron, koulmanite, or boron trioxide, trimethoxyborane, sodium borate, borax, sodium borohydride, dimeric diborazane, trimer triborazane, boron trifluoride, boron trichloride, and phenyl borate.

[0182] In certain embodiments, the oxygen precursor is selected from one or more of the group consisting of boric acid, boron trioxide, sodium borate, and borax.

[0183] In certain embodiments, the heteroatom dopant precursors are sulfur and nitrogen precursors, such as thiourea, thioacetamide, L-cysteine, methionine, dithiocarbamates, dithiooxamides, thiazoles, such as 2-aminothiazole, 5-amino-1,3,4-thiadiazole-2-thiol, thiosemicarbazide, and thiocarbohydrazide.

[0184] In certain embodiments, the heteroatom dopant precursors are boron and oxygen precursors, such as boric acid, boron trioxide, sodium borate, and borax.

[0185] In certain embodiments, for step (a), the carbon precursor and the template material are in a weight ratio of about 2:10 to about 4:10.

[0186] In a particular embodiment, for step (a), the carbon precursor and the template material are in a weight ratio of about 3:10.

[0187] In certain embodiments, for step (a), the heteroatom dopant precursor and the template material are in a weight ratio of about 1:12 to about 1:4.

[0188] In certain embodiments, for step (a), the heteroatom dopant precursor and the template material are in a weight ratio of about 1:10.

[0189] In certain embodiments, for step (a), the heteroatom dopant precursor and the carbon precursor are loaded into the template material by impregnation.

[0190] In certain embodiments, for step (a), an aqueous solution of a carbon precursor and an aqueous solution of a heteroatom dopant precursor are prepared separately and then dropped onto the template material to form a filled template material.

[0191] In certain embodiments, for step (a), the water and template material used to prepare the solution are in a weight ratio of about 1:1 to about 2:1.

[0192] In certain embodiments, for step (a), the water and template material used to prepare the solution are in a weight ratio of about 4:3.

[0193] In certain embodiments, the template material is further charged with a dehydrating agent prior to step (b).

[0194] In certain embodiments, the dehydrating agent is selected from the group consisting of sulfuric acid, formic acid, acetic acid, and citric acid.

[0195] In certain embodiments, for step (b), the removal of moisture and volatiles is carried out by heating.

[0196] In certain embodiments, for step (b), the filled template material resulting from step (a) is heated at about 100° C. and then at about 160° C. to remove moisture and volatiles therefrom.

[0197] In certain embodiments, for step (b), the filled template material obtained from step (a) is heated at about 100° C. for about 6 hours, and then at about 160° C. for about 6 hours to remove moisture and volatile substances therefrom.

[0198] In certain embodiments, for step (c), the activating agent is selected from zinc compounds, phosphoric acid, potassium acetate, sodium hydroxide, potassium carbonate, ammonium carbonate and ammonium persulfate.

[0199] In certain embodiments, the zinc compound is selected from the group consisting of ZnCl2 and ZnO.

[0200] In certain embodiments, for step (c), the activator and template material are in a weight ratio of about 1:6 to about 4:3.

[0201] In certain embodiments, for step (c), the activator and template material are in a weight ratio of about 2:3.

[0202] In certain embodiments, for step (c), the activator is introduced into the composition as a dry solid.

[0203] In certain embodiments, the loaded template material obtained from step (b) or the composition obtained from step (c) is subjected to grinding prior to step (d).

[0204] In certain embodiments, for step (d), the composition resulting from step (c) is activated and carbonized at a temperature between about 600° C. and about 900° C. for about 5 hours.

[0205] In a particular embodiment, for step (d), the composition resulting from step (c) is activated and carbonized at a temperature of about 800° C. for about 5 hours.

[0206] In certain embodiments, for step (d), the activation and carbonization are carried out under an inert atmosphere.

[0207] In certain embodiments, for step (e), the composition resulting from step (d) is treated with HCl to remove the activating agent and with HF to remove the template material.

[0208] In certain embodiments, the doped activated nanoporous carbon material has a nitrogen content of about 0.25% to about 15.00% by weight.

[0209] In certain embodiments, the doped activated nanoporous carbon material has a specific capacitance greater than about 200 F / g at a current density of 0.3 A / g.

[0210] In a particular embodiment, the doped activated nanoporous carbon material has a specific capacitance of about 299 F / g at a current density of 0.3 A / g.

[0211] In certain embodiments, the doped activated nanoporous carbon material has a specific capacitance of about 299 F / g, about 228 F / g, and about 194 F / g at current densities of 0.3 A / g, 0.5 A / g, and 1 A / g.

[0212] In a particular embodiment, the doped activated nanoporous carbon material has a molecular weight of about 1350 m 2 / g~approx. 1700m 2 / g.

[0213] In a particular embodiment, the doped activated nanoporous carbon material has a molecular weight of about 1500 m 2 / g~approx. 1700m 2 / g.

[0214] In a particular embodiment, the doped activated nanoporous carbon material has a molecular weight of about 1600 m 2 / g~approx. 1700m 2 / g.

[0215] In a particular embodiment, the doped activated nanoporous carbon material has a thickness of about 1.000 cm 3 / g ~ approx. 1.600cm 3 / g pore volume.

[0216] In a particular embodiment, the doped activated nanoporous carbon material has a thickness of about 1.300 cm 3 / g ~ approx. 1.600cm 3 / g pore volume.

[0217] In a particular embodiment, the doped activated nanoporous carbon material has a thickness of about 1.400 cm 3 / g ~ approx. 1.600cm 3 / g pore volume.

[0218] In a particular embodiment, the doped activated nanoporous carbon material has a molecular weight of about 1700 m 2 / g and a specific area of ​​approximately 1.465 cm 3 / g pore volume.

[0219] In certain embodiments, the doped activated nanoporous carbon material has a CO2 adsorption capacity of at least about 22.5 mmol / g, determined at 0° C. and 30 bar.

[0220] In a particular embodiment, the doped activated nanoporous carbon material has a CO2 adsorption capacity of about 24.4 mmol / g, determined at 0° C. and 30 bar.

[0221] Use of the doped activated nanoporous carbon material disclosed herein or prepared by the method disclosed herein in an anode material for a sodium ion battery or a lithium ion battery.

[0222] Use of the doped activated nanoporous carbon material disclosed herein or prepared by the method disclosed herein in an electrode material of a supercapacitor.

[0223] Use of the doped activated nanoporous carbon material disclosed herein or prepared by the method disclosed herein in the absorption of CO2.

[0224] Use of the doped activated nanoporous carbon material disclosed herein or prepared by the method disclosed herein for electrochemical energy storage and conversion.

[0225] Use of the doped activated nanoporous carbon material disclosed herein or prepared by the method disclosed herein for water / wastewater treatment.

[0226] Use of the doped activated nanoporous carbon material disclosed herein or prepared by the method disclosed herein in a fuel cell.

[0227] Use of the doped activated nanoporous carbon material disclosed herein or prepared by the method disclosed herein for thermocatalysis and / or electrocatalysis.

[0228] Use of the doped activated nanoporous carbon material disclosed herein or prepared by the methods disclosed herein in a sensor, such as an enzyme biosensor.

[0229] Use of the doped activated nanoporous carbon material disclosed herein or prepared by the method disclosed herein as an antibacterial agent. EXAMPLES

[0230] Example 1 - Preparation of N-doped activated nanoporous carbon material samples with activation by ZnCl2 and doping by aminoguanidine

[0231] Nitrogen-doped activated nanoporous carbon samples were prepared using 3 g of natural halloysite-kaolin nanoclay with a 40:60 ratio of halloysite (Al2Si2O5(OH)4·2H2O):kaolinite (Al2Si2O5(OH)4) infiltrated with a solution containing sucrose (99.5% or more, 0.9 g), water (4 g), sulfuric acid (95-98%, 0.1008 g) and aminoguanidine hydrochloride (0.35 g). An aqueous solution of sucrose and an aqueous solution of aminoguanidine hydrochloride were prepared separately and then combined with the other starting materials. The mixture thus obtained was dripped onto the halloysite-kaolin nanoclay powder. The halloysite-kaolin nanoclay loaded with sucrose, aminoguanidine hydrochloride and sulfuric acid was thoroughly mixed for about 15-20 min and then heated in a hot air oven at 100 °C for 6 h, the temperature was then increased to 160 °C and this temperature was maintained for another 6 h. After heat treatment, the samples were manually ground into fine powder and thoroughly mixed with zinc chloride as dry salt. The samples containing zinc chloride were activated and carbonized in a horizontal quartz glass tube furnace at different temperatures, 600, 700, 800 and 900 °C, for 5 h using a temperature gradient rate of 3 °C / min under constant nitrogen flow. After activation and carbonization, the zinc chloride and nanoclay needed to be removed. For this purpose, a 2M HCl solution was used to remove the zinc chloride with stirring for about 2 h. The samples were further rinsed with distilled water, filtered, the washing step was repeated twice, filtered and then subjected to drying in an oven at about 100 °C overnight. The samples were then dissolved again in a 5 wt% HF solution and stirred for about 2 h to remove the halloysite-kaolin nanoclay. After this, the samples were filtered, rinsed with excess ethanol and then dried in an oven at about 100 °C overnight. A similar set of samples was prepared without the addition of zinc chloride to compare the effect of activation in improving the textural properties and performance of N-doped porous carbon (NHNC).

[0232] Results and Discussion

[0233] N-doped activated nanoporous carbon materials were synthesized from naturally available clay minerals by a template method combined with activation and simple in situ doping. New nitrogen-rich precursors such as aminoguanidine hydrochloride were used as the nitrogen source, halloysite nanotubes (HNTs) as the sacrificial hard template, and ZnCl2 as the activator. The specific surface area and pore volume of the non-activated N-doped porous carbon samples (NHNCs) prepared from sucrose and aminoguanidine precursors were 561–680 m, respectively. 2 g -1 and 0.822~0.989cm 3 g -1 After activation with zinc chloride, the specific surface area and pore volume of N-ANC are in the range of 1466–1649 m, respectively. 2 g -1 and 1.234~1.576cm 3 g -1 The specific surface area (1649 m) of the sample prepared at 800 °C was increased to 1.0 m, suggesting that the introduction of zinc chloride may help to increase the specific surface area and pore volume. 2 / g) and the largest pore volume (1.576 cm 3 / g), whereas the samples prepared at 600 °C and 700 °C show lower specific surface areas and pore volumes. The specific surface areas of the N-doped nanoporous carbon materials without activation with zinc chloride are much lower than those with activation. However, both activated and non-activated samples yield IV-type isotherms with hysteresis loops (P / P0>0.8), which highlight the mesoporosity of these N-doped carbonaceous materials (Kim et al. 2019). The N2 isotherms indicate the presence of mesopores, and the H3-type hysteresis loops produced at higher relative pressures imply a broad pore size distribution (Cheng et al. 2019).

[0234] The nitrogen content in the carbon framework of the sample carbonized at 800 °C (approximately 10%) is relatively higher than that of other N-doped materials reported so far (Zhou et al. 2018; Lu et al. 2017; Kim et al. 2019; Zou et al. 2019). The morphology and structure of the N-ANC materials were investigated by SEM (see Figures 5–7). The obtained N-doped activated halloysite nanocarbon materials mainly consist of thin carbon sheets with irregular flake-like morphology, and the tubular structure of halloysite can hardly be observed. The observed morphology of the N-doped carbon materials may be attributed to the interaction between the carbon and nitrogen precursors and the halloysite template.

[0235] Example 2 - Preparation of N-doped activated nanoporous carbon material samples with activation by ZnCl2 and doping by 3-amino 1,2,4-triazole

[0236] An N-doped activated nanoporous carbon material sample was prepared using the procedure of Example 1, except that 0.35 g of aminoguanidine hydrochloride was replaced with 0.3 g of 3-amino 1,2,4-triazole.

[0237] Results and Discussion

[0238] N-doped activated nanoporous carbon materials were synthesized from naturally available clay minerals by a template method combined with activation and simple in situ doping. 3-Amino-1,2,4-aminotriazole was used as the nitrogen source, halloysite nanotubes (HNTs) as the sacrificial hard template, and ZnCl2 as the activating agent. The specific surface area and pore volume of the non-activated samples (NHNCx) prepared from sucrose and aminotriazole precursors ranged from 490 to 638 m, respectively. 2 g -1 and 0.77 to 1.00 cm 3 g -1 After activation with zinc chloride, the BET surface area and pore volume of the N-doped activated nanoporous carbon material are in the range of 1360–1695 m, respectively. 2g -1 and 1,087 to 1,464 cm 3 g -1 , suggesting that the introduction of zinc chloride may help increase the specific surface area and pore volume. Similarly, in the aminoguanidine precursor, the sample prepared with 3-amino-1,2,4-triazole at 800 °C had the highest specific surface area (1695 m 2 / g) and the largest pore volume (1,464 cm 3 / g) (Table 3). Samples prepared at lower carbonization temperatures (600 °C and 700 °C) have lower specific surface areas when compared to the materials obtained at 800 °C. The pore volumes are also not as good as those of the carbon materials prepared at 800 °C. The specific surface areas of the N-doped carbon nanoflake materials without activation with zinc chloride are much lower than those with activation. However, both activated and non-activated materials yield IV-type isotherms with hysteresis loops (P / P0>0.8), which highlights the mesoporous nature of these N-doped carbonaceous materials (Kim et al. 2019). The N2 isotherms indicate the presence of mesopores, and the H3-type hysteresis loops produced at higher relative pressures imply a broad pore size distribution (Cheng et al. 2019).

[0239] Table 3 -Textural properties of N-doped activated porous carbons prepared with 3-amino-1,2,4-triazole carbonized at different temperatures [Table 3]

[0240] Control Example - Preparation of doped nitrogen-free activated nanoporous carbon material

[0241] In a typical synthesis of activated nanoporous carbon by the clay templating method, 3 g of natural halloysite-kaolin nanoclay was impregnated with a sucrose solution prepared by dissolving 0.9 g of sucrose in 4 g of water and adding sulfuric acid (0.1008 g). The resulting mixture was mixed thoroughly for about 15-20 min and then transferred to a hot air oven. Initially, the mixture was heated at 100 °C for 6 h, after which the temperature was increased to 160 °C and maintained for another 6 h. After heat treatment, it is ground to a fine powder using a mortar and pestle. ZnCl2 was added as a dry salt to the heated nanoclay-sucrose mixture, which was then mixed thoroughly by crushing and heated again to 600 °C for 5 h using a temperature ramp rate of 3 °C / min under a constant nitrogen flow. The carbonized sample was washed with 2 M HCl to remove ZnCl2, rinsed in distilled water, filtered, dried, and then further heated to 900 °C for 5 h using a temperature ramp rate of 5 °C / min under a constant nitrogen flow. The resulting black powder was then dissolved in 5 wt% dilute HF solution and stirred for about 2 hours, filtered, and washed with excess ethanol. The filtered sample was dried overnight in a hot air oven at 100°C and then characterized.

[0242] Comparison of N-doped activated nanoporous carbon materials with and without nitrogen doping

[0243] Electrodes were fabricated using the N-ANCx samples and the supercapacitor performance was tested using standard electrode testing methods using a three-electrode cell configuration. The electrolyte used for capacitance measurements was 3 M KOH aqueous solution. The scan rates for obtaining cyclic voltammetry (CV) curves were varied from 5 to 100 mV s. -1 The CV curves show a nearly rectangular shape, indicating excellent charge storage capability and high efficiency, which also confirms that the N-ANCx materials have the properties of an ideal electric double layer capacitor (EDLC). 700 The shape of the CV curve of the sample is N-ANC 800 and N-ANC 900 Note that the N-ANC is not as rectangular as the 800 and N-ANC 900The quasi-rectangular shape of the CV curve is due to the scan rate of 100 mV s -1 The current density range selected for the galvanostatic charge-discharge (GCD) cycling process was 0.3–10 A g -1 The GCD profile of the N-ANCx material did not reveal any significant reduction in the IR voltage, and the shape of the profile was nearly linear and symmetric, which indicates that the N-ANC 800 and N-ANC 900 This confirms that the material has a high specific capacitance and can be an efficient electrode for electric double layer capacitors (Figure 9(a-f)).

[0244] Figure 10(a) shows the current at 10mV s -1 The CV curves of the N-ANCx material obtained at a scan rate of 800 and N-ANC 900 The quasi-rectangular shape of the N-ANC 700 It was clearly explained that the CV of the sample was better than 0.3A g -1 N-ANC at a current density of 900 The specific capacitance is 299F g -1 and the current density is 1A g -1 If it increases to 194F g -1 Among the N-ANCx materials studied, N-ANC 900 is N-ANC 800 Although it has the highest specific surface area and pore volume, 1A g -1 In N-ANC 800 (183F g -1 ) and N-ANC 700 (151F g -1 ) with the highest capacitance (194F g -1 ) is shown in Fig. 10(b). Material N-ANC 900 is a material previously reported by the inventors, AHNC (158F g -1 / 1A g -1) (Ramadass et al. 2020) -1 / 1A g -1 ) was shown.

[0245] In general, lower capacitance values ​​are observed at higher current densities because the electrolyte ions have less time to penetrate the electrode material (Yanilmaz, et al. 2017). However, N-ANCs 800 and N-ANC 900 The material provides abundant inner surface for good diffusion of electrolyte ions even at higher current densities, thus achieving a current density of 10 A g -1 At a current density of 148 F g -1 A significantly higher specific capacitance was observed, demonstrating their better capacitance capability at higher current densities.

[0246] Electrochemical impedance (EIS) analysis was also performed to investigate the electrochemical behavior of the electrodes prepared using the N-ANCx samples, and a Nyquist plot was obtained from the EIS analysis (Figure 10(c)). A typical Nyquist plot of an EDLC shows a semicircular curve in the high frequency zone and a vertical straight line in the low frequency zone. 800 and N-ANC 900 The Nyquist plot of N-ANC shows a vertical line in the low frequency region, which also confirms the good electrochemical behavior and the rapid penetration of electrolyte ions at the surface of the material. 800 and N-ANC 900 The semicircular arcs observed in the high frequency Nyquist plots of the samples indicate fast electron transport between the electrodes and the electrolyte. 900 The supercapacitance values ​​obtained for (Figure 10(d)) were found to exceed those reported for commercially available single-walled and multi-walled CNTs, activated carbon, ordered mesoporous carbon, HNT-derived activated carbon-porous carbon, and a few other carbon-based materials reported to date (Mansuer, et al. 2021).

[0247] The data in Table 1 are N-ANC 900The results show that the performance of N-doped porous carbon materials, such as nitrogen-doped carbon nanofibers, casein-derived porous carbon, and coffee waste-derived nitrogen-doped carbon, reported in recent literature, is superior to that of other N-doped porous carbon materials. 900 The exceptional performance of N-ANCs is due to the uniform N-doping on the nanostructure of the porous carbon, which enhances the surface wettability. The combination of high specific surface area and large pore volume originating from the interconnected meso- and microchannels in the tubular network further improves the rate performance. 900 The enhanced electrochemical behavior of N-ANC is due to its perfect nanoarchitecture, which is favorable for increased ion access and fast diffusion. The presence of hierarchical pore distribution provides the advantage of improving the electrochemical behavior. The microporous structure helps to form an electric double layer, and the mesopores shorten the length between the electrolyte-electrode interface (Song et al. 2021). 900 The materials were subjected to cycle performance tests. The specific capacity retention was measured by carrying out a charge / discharge process for a long period (5A g -1 Even after 4000 cycles at a current density of 1000 Hz, the resistance of N-ANC was approximately 91%. 900 These results suggest that the electrodes prepared from the materials are highly stable and have excellent cycle performance. Although it is known that a large amount of heteroatoms can cause the carbon framework to collapse, resulting in a decrease in the stability of the electrodes, in this study, high N doping was successfully achieved by effectively combining the in-situ nanotemplate method and activation technique.

[0248] N-ANC 900 The excellent cycleability of electrodes fabricated from N-ANCs suggests that N atoms are successfully incorporated into the nanoporous carbon framework without affecting its nanostructure (Zhou et al. 2020). 800 has the highest specific surface area, but the specific capacity is 900This can be attributed to the combination of high specific surface area, high nitrogen content, and most importantly, high crystallinity produced at the high carbonization temperature, which contributes to the excellent specific capacity of the material prepared at 900 °C. 900 The excellent performance of N-ANCs reveals the importance of the combined doping, templating and activation treatment employed in this work. The excellent textural parameters, when combined with the crystallinity, uniform distribution of N atoms in the porous carbon structure and oxygen functional groups generated by extensive oxidation, caused by high-temperature carbonization and activation with ZnCl2, are the key to the success of N-ANCs. 900 This helps to achieve excellent specific capacitance.

[0249] Example 3 - Specific capacity of N-doped activated nanoporous carbon material

[0250] Supercapacitor measurements were carried out on a CHI760E (CH instruments) workstation in 6 M KOH aqueous electrolyte solution under a three-electrode assembly using a Pt rod and Ag / AgCl as counter and reference electrodes, respectively. Electrochemical impedance spectroscopy (EIS) measurements were studied by applying an AC voltage with an amplitude of 10 mV in the frequency range of 0.01 Hz to 100 kHz. Galvanostatic charge-discharge (GCD) tests were also performed at different current densities.

[0251] The specific capacity (Csp) was calculated from the CV using the following formula: Csp = (i+-i-) / (m × scanning speed) where i+ and i- are the maximum values ​​of current in the positive and negative scans, respectively, and m is the mass of a single electrode.

[0252] The specific capacity was calculated from the galvanostatic charge-discharge curves using the following equation: Csp = (i) (dt) / (m × dv) In the formula, i is the discharge current and dt / dv is the slope of the discharge curve.

[0253] The electrochemical performance of the N-doped activated nanoporous carbon was investigated by cyclic voltammetry (CV), galvanostatic charge-discharge curves and electrochemical impedance spectroscopy (EIS) in 6 M H2SO4 aqueous electrolyte. Cyclic voltammograms (CV) were measured at different scan rates (5-100 mV / s) and are shown in Figure 10. It is observed that the peak current increases with increasing scan rate. The CV of the N-doped activated nanoporous carbon shows a quasi-rectangular curve indicating the excellent supercapacitive behavior of the material. The specific capacitance obtained from the CV is about 228 F / g at a current density of 0.3 A / g. The galvanostatic charge-discharge curves of the material were measured in a potential window of 0-0.8 V vs Ag / AgCl (3 M KOH). Figure 9 shows the charge-discharge curves measured at different current densities (0.3-5 A / g). The discharge curve appears almost triangular, similar to the discharge curve of an ideal capacitor. In general, with the increase of current density, the specific capacitance gradually decreases due to the presence of aperture restriction, and as the charging time of the capacitor at higher current density becomes shorter, the electrolyte ions cannot fully enter the internal space of the carbon material, resulting in a decrease in the effective specific surface area that reduces the specific capacitance. However, the N-doped carbon material prepared according to the present disclosure showed a specific capacitance of about 153 F / g even at a current density of 5 A / g, demonstrating the good rate performance of the N-doped activated nanoporous carbon material carbonized at 900 ° C.

[0254] Example 4 - CO2 adsorption by N-doped activated nanoporous carbon materials

[0255] CO2 adsorption isotherms were measured over a range of pressures (0–30 bar) on a Micromeritics HPVA equipped with a temperature-controlled circulator. CO2 adsorption was measured at three different temperatures: 0 °C, 10 °C and 25 °C. Prior to all measurements, the samples were degassed at 250 °C for 10 h. The CO2 adsorption capacity of the N-doped activated nanoporous carbon material carbonized at 800 °C was 24.4 mmol g -1 The CO2 adsorption capacity of the N-doped activated nanoporous carbon material carbonized at 700 °C was 21.6 mmol g at 0 °C and 30 bar. -1For the N-doped activated nanoporous carbon material carbonized at 800 °C, CO adsorption experiments were also carried out at different temperatures (0 °C, 10 °C and 25 °C) with pressures varying from 0 to 30 bar (Figure 8(b)). When a CO pressure of 30 bar was applied, the highest CO adsorption was about 24.4 mmol g at 0 °C. -1 However, at low pressures of 0 to 1 bar, the CO2 adsorption capacity was 3.9 mmol g at 0 °C. -1 This increase in CO2 adsorption with increasing pressure suggests that the CO2 adsorption process was exothermic in nature. On the other hand, adsorption decreases with increasing temperature. For example, at low pressures of 0-1 bar, the CO2 adsorption capacity at 25 °C is 2.0 mmol g -1 , which is almost half of the CO2 adsorption capacity at 0°C.

[0256] Example 5 - Preparation of S and N doped activated nanoporous carbon material samples with activation by ZnCl2 and doping by thiourea

[0257] Sulfur and nitrogen doped activated nanoporous carbon samples were prepared using 3 g of natural halloysite-kaolin nanoclay with a 40:60 ratio of halloysite (Al2Si2O5(OH)4·2H2O):kaolinite (Al2Si2O5(OH)4) infiltrated with a solution containing sucrose (99.5% or more, 0.9 g), water (5 g), sulfuric acid (95-98%, 0.1008 g) and thiourea (0.35 g). An aqueous solution of sucrose and an aqueous solution of thiourea were prepared separately and then combined with the other starting materials. The mixture thus obtained was dripped onto the halloysite-kaolin nanoclay powder. The halloysite-kaolin nanoclay loaded with sucrose, thiourea and sulfuric acid was thoroughly mixed for about 15-20 min and then heated in a hot air oven at 100 °C for 6 h, the temperature was then increased to 160 °C and this temperature was maintained for another 6 h. After heat treatment, the samples were manually ground into fine powder and thoroughly mixed with zinc chloride as dry salt. The samples containing zinc chloride were activated and carbonized in a horizontal quartz glass tube furnace at different temperatures, 700 and 800 °C, for 5 h using a temperature gradient rate of 3 °C / min under a constant nitrogen flow. After activation and carbonization, the zinc chloride and nanoclay were removed. For this purpose, a 2M HCl solution was used to remove the zinc chloride with stirring for about 2 h. The samples were further rinsed with distilled water, filtered, the washing step was repeated twice, filtered and then subjected to drying in an oven at about 100 °C overnight. The samples were then dissolved again in a 5 wt% HF solution and stirred for about 2 h to remove the halloysite-kaolin nanoclay. After this, the samples were filtered, rinsed with excess ethanol and then dried in an oven at about 100 °C overnight.

[0258] Table 4 -Textural properties of SN-doped activated porous carbons prepared with thiourea carbonized at different temperatures [Table 4]

[0259] A similar set of samples was prepared without the addition of zinc chloride to compare the effect of activation in improving the textural properties and performance of S- and N-doped porous carbon (SN-HNC).

[0260] Table 5 - Comparison of textural properties between SN-doped activated nanoporous carbon and S- and N-doped nanoporous carbon prepared without activation (SN-HNC). [Table 5]

[0261] Example 6 - Preparation of B-doped activated nanoporous carbon material samples with activation by ZnCl2 and doping by boric acid

[0262] Boron-doped activated nanoporous carbon samples were prepared using 3 g of natural halloysite-kaolin nanoclay with a 40:60 ratio of halloysite (Al2Si2O5(OH)4·2H2O):kaolinite (Al2Si2O5(OH)4), which was infiltrated with a solution containing sucrose (99.5% or more, 0.9 g), water (6 g), sulfuric acid (95-98%, 0.1008 g) and boric acid (0.35 g). An aqueous solution of sucrose and an aqueous solution of boric acid were prepared separately and then combined with the other starting materials. The mixture thus obtained was dripped onto the halloysite-kaolin nanoclay powder. The halloysite-kaolin nanoclay loaded with sucrose, boric acid and sulfuric acid was thoroughly mixed for about 15-20 min, then heated in a hot air oven at 100 °C for 6 h, the temperature was raised to 160 °C and this temperature was maintained for another 6 h. After heat treatment, the samples were manually ground into fine powder and thoroughly mixed with zinc chloride as dry salt. The samples containing zinc chloride were activated and carbonized in a horizontal quartz glass tube furnace at different temperatures, 800 and 900 °C, for 5 h using a temperature ramp rate of 3 °C / min under constant nitrogen flow. After activation and carbonization, the zinc chloride and nanoclay needed to be removed. For this purpose, a 2M HCl solution was used to remove the zinc chloride with stirring for about 2 h. The samples were further rinsed with distilled water, filtered, the washing step was repeated twice, filtered and then subjected to drying in an oven at about 100 °C overnight. The samples were then dissolved again in a 5 wt% HF solution and stirred for about 2 h to remove the halloysite-kaolin nanoclay. After this, the samples were filtered, rinsed with excess ethanol and then dried in an oven at about 100 °C overnight.

[0263] Table 6 -Textural properties of B-doped activated porous carbons prepared with boric acid carbonized at different temperatures [Table 6]

[0264] A similar set of samples was prepared without the addition of zinc chloride to compare the effect of activation in improving the textural properties and performance of B-doped porous carbon (B-HNC).

[0265] Table 7 - Comparison of textural properties between B-doped activated nanoporous carbon and B-doped nanoporous carbon prepared without activation (B-HNC) [Table 7]

[0266] Example 7 - Preparation of N-doped activated nanoporous carbon material samples from different clay templates with activation by ZnCl2 and doping by aminotriazole

[0267] In order to understand the uniqueness of kaolin-halloysite mixed clay as a natural nanotemplate for the preparation of N-doped activated nanoporous carbon, different types of other clay materials were used as templates for the synthesis of N-doped activated nanoporous carbon. Halloysite (100%), kaolinite (100%), attapulgite, and bentonite were used as templates. The experimental procedures were the same as mentioned in Example 1, except for replacing the kaolin-halloysite mixed clay template with other clay templates.

[0268] Table 8 -Textural properties of N-doped activated porous carbons prepared with different clay templates carbonized at different temperatures [Table 8]

[0269] Although embodiments of the invention have been described in the above detailed description, it will be understood that the invention is not limited to the disclosed embodiments, but rather that numerous rearrangements, modifications and substitutions are possible without departing from the scope of the invention.

[0270] Throughout this specification the word "comprise" or variations such as "comprises" or "comprising" are understood to mean the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not to the exclusion of other elements, integers or steps, or group of elements, integers or steps.

[0271] All publications mentioned in this specification are incorporated herein by reference. Any discussion of documents, acts, materials, devices, articles or the like which has been included in this specification is solely for the purpose of providing a context for the present invention. No admission is to be taken as an admission that any or all of such matters formed part of the prior art or were general knowledge in the field relevant to the present invention, as they existed in Australia or anywhere else prior to the priority date of each claim of this application.

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Claims

**Claim 1** A doped activated nanoporous carbon material prepared from a template material comprising natural halloysite-kaolin nanoclay, a carbon precursor, a heteroatom dopant precursor, and an activator, the doped activated nanoporous carbon material exhibiting the form of flakes and nanotubes and having surface heteroatom functionality. **Claim 2** The doped activated nanoporous carbon material according to claim 1, wherein the template material consists of natural halloysite-kaolin nanoclay. **Claim 3** The doped activated nanoporous carbon material according to any one of claims 1 or 2, wherein the natural halloysite-kaolin nanoclay contains more than 40% by weight of halloysite nanotubes. **Claim 4** The doped activated nanoporous carbon material according to claim 3, wherein the natural halloysite-kaolin nanoclay contains more than 80% by weight of halloysite nanotubes. **Claim 5** The doped activated nanoporous carbon material according to claim 1 or 2, wherein the carbon precursor is a carbohydrate-based compound. **Claim 6** The doped activated nanoporous carbon material according to claim 5, wherein the carbon precursor is a sugar-based compound. **Claim 7** The doped activated nanoporous carbon material according to claim 6, wherein the sugar-based compound is selected from the group consisting of sucrose, glucose, fructose, and polysaccharides. **Claim 8** The doped activated nanoporous carbon material according to claim 7, wherein the polysaccharide is selected from the group consisting of cellulose, chitosan, and starch. **Claim 9** The doped activated nanoporous carbon material according to claim 1 or 2, wherein the heteroatom dopant precursor is a compound containing one or more heteroatoms. **Claim 10** The doped activated nanoporous carbon material according to claim 9, wherein the heteroatom dopant precursor is selected from one or more of the group consisting of a nitrogen precursor, a sulfur precursor, a boron precursor, and an oxygen precursor. **Claim 11** The nitrogen precursor is selected from the group consisting of aminoguanidine, aminoguanidine hydrochloride, aminotriazole, urea, chitosan, cyanamide, dicyanamide, thiourea, melamine, casein, polyaniline, polypyrrole, aminotetrazole, and aminotriazine; the sulfur precursor is selected from one or more of the group consisting of diphenyldisulfide, polyphenylene sulfide, bis(trimethylsilyl) sulfide, alkyl mercaptan, thiophene, sulfur powder, sodium sulfide, sodium dithionite, sodium thiosulfate, thiourea, thioacetamide, L-cysteine, methionine, dithiocarbamate, dithioxamide, thiazoles such as 2-aminothiazole, 5-amino-1,3,4-thiadiazole-2-thiol, thiosemicarbazide, and thiocarbohydrazide; and the boron precursor is selected from the group consisting of boric acid, ammonia borane (borazane), diborane, trimethyl boron, colemanite, or boron trioxide, trimethoxyborane, sodium borate, borax, sodium borohydride, dimeric diborazane, trimeric triborazane, boron trifluoride, boron trichloride, and phenyl borate. The doped activated nanoporous carbon material according to claim 10.

12. The doped activated nanoporous carbon material according to claim 11, wherein the nitrogen precursor is 3-amino-1,2,4-triazole.

13. The doped activated nanoporous carbon material according to claim 1 or 2, wherein the activator is selected from the group consisting of zinc compounds, phosphoric acid, potassium acetate, sodium hydroxide, potassium carbonate, ammonium carbonate, and ammonium persulfate.

14. The zinc compound is selected from the group consisting of ZnCl ２ and ZnO, and the doped activated nanoporous carbon material according to claim 13.

15. The doped activated nanoporous carbon material according to claim 1 or 2, having a heteroatom content of about 0.25 wt% to about 15.00 wt%.

16. The doped activated nanoporous carbon material according to claim 1 or 2, having specific capacitances of about 299 F / g, about 228 F / g, and about 194 F / g at current densities of 0.3 A / g, 0.5 A / g, and 1 A / g.

17. About 1350 m ２ / g to about 1700 m ２ The doped activated nanoporous carbon material according to claim 1 or 2, having a specific surface area of / g.

18. About 1.000 cm ３ / g to about 1.600 cm ３ The doped activated nanoporous carbon material according to claim 1 or 2, having a pore volume of / g.

19. When determined at 0 °C and 30 bar, at least about 22.5 mmol / g of CO ２ adsorption capacity, the doped activated nanoporous carbon material according to claim 1 or 2.

20. A method for preparing a doped activated nanoporous carbon material, comprising the following steps: Step (a): filling a template material containing natural halloysite-kaolin nanoclay with a carbon precursor and a heteroatom dopant precursor; Step (b): removing moisture and volatile substances from the filled template material obtained from step (a); Step (c): producing a composition containing the filled template material obtained from step (b) and an activator; Step (d): activating and carbonizing the composition obtained from step (c) at a temperature of about 600 °C to about 900 °C; and Step (e): removing the template material and the activator from the composition obtained from step (d). A method comprising the above steps.

21. The method according to claim 20, wherein the template material consists of natural halloysite-kaolin nanoclay.

22. The method according to claim 20 or 21, wherein the natural halloysite-kaolin nanoclay contains more than 40% by weight of halloysite nanotubes.

23. The method according to claim 22, wherein the natural halloysite-kaolin nanoclay contains more than 80% by weight of halloysite nanotubes.

24. The method according to claim 20 or 21, wherein for step (a), the carbon precursor is a carbohydrate-based compound.

25. The method according to claim 24, wherein the carbohydrate-based compound is a sugar-based compound.

26. The method according to claim 25, wherein the sugar-based compound is selected from the group consisting of sucrose, glucose, fructose, and polysaccharides.

27. The method according to claim 26, wherein the polysaccharide is selected from the group consisting of cellulose, chitosan, and starch.

28. The method according to claim 20 or 21, wherein the heteroatom dopant precursor is selected from one or more of the group consisting of a nitrogen precursor, a sulfur precursor, and a boron precursor.

29. The nitrogen precursor is selected from the group consisting of aminoguanidine, aminoguanidine hydrochloride, aminotriazole, urea, chitosan, cyanamide, dicyanamide, thiourea, melamine, casein, polyaniline, polypyrrole, aminotetrazole and aminotriazine, and the sulfur precursor is selected from the group consisting of diphenyldisulfide, polyphenylene sulfide, bis(trimethylsilyl) sulfide, alkyl mercaptan, thiophene, sulfur powder, sodium sulfide, sodium dithionite, sodium thiosulfate, thiourea, thioacetamide, L-cysteine, methionine, dithiocarbamate, dithioxamide, thiazoles such as 2-aminothiazole, 5-amino-1,3,4-thiadiazole-2-thiol, thiosemicarbazide and thiocarbohydrazide, and the boric acid, ammonia borane (borazane), diborane, trimethylboron, colemanite, or boron trioxide, trimethoxyboron, sodium borate, borax, sodium borohydride, dimeric diborazane, trimeric triborazane, boron trifluoride, boron trichloride and phenyl borate is selected from the group consisting of, the method according to claim 28.

30. The method according to claim 29, wherein the nitrogen precursor is 3-amino-1,2,4-triazole.

31. For step (a), the method according to claim 20 or 21, wherein the carbon precursor and the template material are in a weight ratio of about 2:10 to about 4:

10.

32. For step (a), the method according to claim 20 or 21, wherein the heteroatom dopant precursor and the template material are in a weight ratio of about 1:12 to about 1:

4.

33. The method according to claim 20 or 21, wherein the template material is further filled with a dehydrating agent before step (b).

34. The method according to claim 33, wherein the dehydrating agent is selected from the group consisting of sulfuric acid, formic acid, acetic acid and citric acid.

35. For step (c), the method according to claim 20 or 21, wherein the activator is selected from zinc compounds, phosphoric acid, potassium acetate, sodium hydroxide, potassium carbonate, ammonium carbonate and ammonium persulfate.

36. wherein the zinc compound is selected from the group consisting of ZnCl ２ and ZnO, the method according to claim 35.

37. For step (c), the method according to claim 20 or 21, wherein the activator and the template material are in a weight ratio of about 1:6 to about 4:

3.

38. The method according to claim 20 or 21, wherein the filled template material obtained from step (b) or the composition obtained from step (c) is subjected to grinding before step (d).

39. For step (d), the method according to claim 20 or 21, wherein the composition obtained from step (c) is activated and carbonized at a temperature of about 600 °C to about 900 °C for about 5 hours.

40. For step (d), the method according to claim 20 or 21, wherein the activation and carbonization are carried out in an inert atmosphere.

41. For step (e), the method according to claim 20 or 21, wherein the composition obtained from step (d) is treated with HCl to remove the activator and treated with HF to remove the template material.

42. The doped activated nanoporous carbon material according to claim 1 or 2, or the doped activated nanoporous carbon material prepared by the method according to claim 20 or 21, as an anode material for a sodium-ion battery or a lithium-ion battery, an electrode material for a supercapacitor, CO ２ absorption, electrochemical energy storage and conversion, water / wastewater treatment, fuel cells, thermocatalytic reactions and / or electrocatalytic reactions, use as a sensor such as an enzyme biosensor or an antibacterial agent.

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