Description:FIELD OF INVENTION
[001] The present disclosure belongs to the technical field of organic aerogels. More particularly, the present disclosure relates to an activated carbon aerogel. Further, the present disclosure also relates to a method of preparation of an activated carbon aerogel. The synthesised activated carbon are used as electrode material in batteries and supercapacitors, hydrogen storage devices, materials for CO2 sequestration, and catalyst support systems.

BACKGROUND OF THE INVENTION
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[003] Numerous methods including physical activation (using suitable oxidising gases like steam, carbon dioxide etc. at high temperatures of 600-1200 ºC) and chemical activation (using chemical activating agents like potassium hydroxide (KOH), zinc chloride (ZnCl2), phosphoric acid (H3PO4), sodium hydroxide (NaOH), ferric chloride (FeCl3)) have been reported for the synthesis of activated carbon with high surface area. Chemical activation is usually preferred over physical activation due to better yield, high porosity/surface area along with well-developed/interconnected pore structures. Activated carbon is quite extensively used in various fields and their applicability/efficiency is highly dependent on the surface area and porosity which in turn is related to the activating agent used. However, the toxic nature of these activating agents, tedious and time consuming steps involved in removing them from the product and their high cost are the major limitations.
[004] In the case of chemical activation, a wide variety of materials (activating agents) are commonly used including acids, bases and salts (e.g., H3PO4, KOH, NaOH, ZnCl2, FeCl3 etc.) followed by heating at different activation temperatures (Tact) to produce activated carbon material. Francisco and Yavic Buss (CA1334192C) disclosed the activation of carbonaceous cellulose materials with ZnCl2. Aqueous ZnCl2 was mixed with carbon material in the ratio 1:4 followed by carbonization temperatures between 400-700 ºC. The synthesised activated carbon had a specific surface area of 1800 m2∙g-1 and bulk density of 0.35 g∙cm-3. Mondragon et al. (US5614459A) disclosed a similar method for the synthesis of activated carbon using ZnCl2 and SnCl2 and obtained a maximum surface area of 1047 m2∙g-1. Toan et al. (WO1994000382A1) revealed the synthesis of activated carbon from lignite using KOH /NaOH as activating agent and claimed an improvement in hexane absorption properties. Geramita et al. (US2013028061) discussed the synthesis of activated carbon aerogel (with a surface area of 898 m2∙g-1) through physical activation using CO2 gas at temperatures ranging from 800-1000 ºC. Hashisho et al. (US8563467B2) disclosed the synthesis of activated carbon from petroleum coke using microwave irradiation in the presence of water.
[005] Thus the prior arts related to activated carbon synthesis have serious issues which include high cost, long duration for activation tedious steps in removing the activating agent, environmental pollution and toxicity. The present invention arose from research directed to resolving these problems.

OBJECTS OF THE INVENTION
[006] An objective of the present disclosure is to provide an activated carbon aerogel.
[007] Another objective of the present disclosure is to provide an activated carbon aerogel through eco-friendly route without the usage of any toxic chemicals.
[008] Still another objective of the present disclosure is to provide a method of preparation of an activated carbon aerogel.
[009] Yet another objective of the present disclosure is to provide an improved method for one shot synthesis of activated carbon aerogel with ultra-high surface area and porosity.

SUMMARY
[0010] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
[0011] Accordingly, in one aspect, the present disclosure relates to an activated carbon aerogel has highly porous structure with a uniform dispersion of the MnO and has an ultra-high surface area ranging from 500 to 5000 m2∙g-1 and a porosity ranging from 0.1 cm3∙g-1 to 6.0 cm3∙g-1.
[0012] Another aspect of the present disclosure relates to a method of preparation of an activated carbon aerogel comprising: a) reacting a carbon precursor and a crosslinking agent to a polycondensation reaction in the presence of a catalyst to obtain a first solution; b) adding a doping agent to the solution with stirring to obtain a second solution; c) processing the second solution by conversion into a gel; d) strengthening the gel under heating to obtain a strengthened gel; e) subjecting the strengthened gel to solvent exchange followed by drying to obtain a xerogel; and f) subjecting the xerogel to pyrolysis to obtain an activated carbon aerogel.
[0013] Various objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing FIGs. in which like numerals represent like features.

BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The accompanying drawing(s) are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. The diagrams are for illustration only, which thus is not a limitation of the present disclosure.
[0015] FIG. 1 illustrates (a) reaction between resorcinol and formaldehyde, (b) schematic representation of the synthesis of carbon aerogel.
[0016] FIG. 2 illustrates (a) SEM and (b) TEM images for the synthesized activated carbon with 10 wt% of dopant.

DETAILED DESCRIPTION OF THE INVENTION
[0017] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0018] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0019] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0020] In some embodiments, numbers have been used for quantifying weights, percentages, ratios, and so forth, to describe and claim certain embodiments of the invention and are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.
[0021] The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0022] Unless the context requires otherwise, throughout the specification which follows, the word “comprise” and variations thereof, such as “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0023] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0024] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. Furthermore, the ranges defined throughout the specification include the end values as well, i.e., a range of 1 to 10 implies that both 1 and 10 are included in the range. For the avoidance of doubt, the applicant shall be entitled to any equivalents according to applicable law.
[0025] All methods described herein can be performed in a suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples or exemplary language (e.g., “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0026] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified.
[0027] The description that follows, and the embodiments described therein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.
[0028] It should also be appreciated that the present disclosure can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.
[0029] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0030] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[0031] The term “or”, as used herein, is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[0032] The terms “weight percent,” “wt-%,” “percent by weight,” “% by weight,” and variations thereof, as used herein, refer to the concentration of a substance as the weight of that substance divided by the total weight of the composition and multiplied by 100. It is understood that, as used here, “percent,” “%,” and the like are intended to be synonymous with “weight percent,” “wt-%,” etc.
[0033] Various terms are used herein to the extent a term used is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0034] Simple, efficient and eco-friendly route for the preparation of activated carbon having very high specific surface area and porosity through a single step route is detailed in the present embodiment. Featured with the usage of non-toxic chemicals, the synthesised activated carbon is proposed for application in batteries, supercapacitors and hydrogen storage devices. The synthesised activated carbon has very high specific surface area of 2350 m2·g-1 which is dependent on the amount of dopant used.
[0035] An embodiment of the present disclosure is to provide an activated carbon aerogel has highly porous structure with a uniform dispersion of the MnO and has an ultra-high surface area ranging from 500 m2∙g-1 to 5000 m2∙g-1 and a porosity ranging from 42% to 92%. Preferably, the ultra-high surface area ranging from 1500 m2∙g-1 to 4000 m2∙g-1 and the porosity ranging from 60% to 85%.
[0036] In some embodiment, said activated carbon aerogel has a pore diameter ranging from 1 nm to 20 nm. Preferably, the pore diameter ranging from 5 nm to 20 nm.
[0037] In some embodiment, said activated carbon aerogel has a pore volume ranging from 0.1 cm3∙g-1 to 6.0 cm3∙g-1. Preferably, the pore volume ranging from 1.62 cm3∙g-1 – 5.76 cm3∙g-1.
[0038] In some embodiment, said activated carbon aerogel has a low density ranging from 0.03 g/cc to 0.5 g/cc. preferably, the low density ranging from 0.05 g/cc to 0.3 g/cc.
[0039] In some embodiment, said activated carbon aerogel has an X-ray powder diffraction pattern (CuKα) comprising peaks at 2-theta about 39.94º, 40.6º, 58.57º, 70.19º.
[0040] Another embodiment of the present disclosure is to provide a method of preparation of an activated carbon aerogel comprising: a) reacting a carbon precursor and a crosslinking agent to a polycondensation reaction in the presence of a catalyst to obtain a first solution; b) adding a doping agent to the solution with stirring to obtain a second solution; c) processing the second solution by conversion into a gel; d) strengthening the gel under heating to obtain a strengthened gel; e) subjecting the strengthened gel to solvent exchange followed by drying to obtain a xerogel; and f) subjecting the xerogel to pyrolysis to obtain an activated carbon aerogel.
[0041] In some embodiment, the carbon precursor is selected from a group comprising of resorcinol, melamine, phenol-formaldehyde and combination thereof and has an amount ranging from 5 to 35 wt%. Preferably, the carbon precursor is resorcinol and has an amount ranging from 10 to 35 wt%.
[0042] In some embodiment, the crosslinking agent is selected from a group comprising of formaldehyde, melamine, APTES and combination thereof and has an amount ranging from 15 to 30 wt%. Preferably, the crosslinking agent is formaldehyde and has an amount ranging from 15 to 25 wt%.
[0043] In some embodiment, the catalyst is selected from a group comprising of sodium carbonate, sodium hydroxide, hydrochloric acid and combination thereof and has an amount ranging from 0.1 to 3 wt%. Preferably, the catalyst is sodium carbonate and has an amount ranging from 0.5 to 3 wt%.
[0044] In some embodiment, the doping agent is selected from a group comprising of manganese (II) acetate tetrahydrate, zinc chloride and combination thereof and has an amount ranging from 5 to 20 wt%. Preferably, the doping agent is manganese (II) acetate tetrahydrate and has an amount ranging from 5 to 15 wt%.
[0045] In some embodiment, the second solution in step c) is stirred at a speed ranging from 200 to 800 RPM for a time period of 0.1 h to 2 h. Preferably, the speed ranging from 500 to 800 RPM for a time period ranging from 02 to 2 h.
[0046] In some embodiment, the solvent in step e) is selected from a group comprising of acetic acid, acetone, water, ethanol and combination thereof. Preferably, the solvent is acetic acid and acetone and combination thereof.
[0047] In some embodiment, the drying in step e) is carried out at a temperature range from 50 to 70 °C for a time period ranging from 1 to 3 days. Preferably, the drying temperature is 60 °C for a time period is 2 days.
[0048] In some embodiment, the pyrolysis in step f) is carried out at a temperature range from 900 to 1100 °C for a time period ranging from 0.1 h to 2 h. Preferably, the pyrolysis temperature is 1000 °C for a time period ranging from 0.2 to 2 h.
[0049] Interestingly, the present embodiment introduces a novel cost effective, eco-friendly and less time consuming route for the synthesis of activated carbon aerogels.
[0050] Aerogels are highly porous materials with 100% open pore structure having pore diameters in the sub nanometre scales combined with low density. Surface areas of carbon aerogels vary between 900-1300 m2/g. Sol-gel formation followed by super critical drying and carbonization under inert atmosphere is usually adopted for the synthesis of carbon aerogels. Sol-gel process involving the reaction between resorcinol and formaldehyde in presence of a suitable catalyst followed by ambient pressure drying is usually adopted for the synthesis aerogels. The synthesized aerogels are then carbonized at specific carbonization temperature under inert atmosphere as shown in the FIG 1.
[0051] Carbon aerogel with density between 1.5-2.7 g/cc is used quite extensively in the development of supercapacitors, batteries, catalyst support systems, adsorbent for various gases including volatile organic gases, hydrogen storage devices, photocatalyst etc.
[0052] Aerogels are highly porous materials with pore diameter in the sub nanometric scale combined with high surface area usually exceeding 1000 m2/g and very low densities in the range 0.008 to 0.1 g/cc. The synthesis of carbon aerogels involves polycondensation reaction between resorcinol and formaldehyde to form a gel as shown in FIG. 1(a). The solvent is then removed from gel through ambient pressure drying technique as shown in FIG. 1(b). The aerogels are then carbonized or pyrolysed at different temperatures to produce porous carbon aerogels. The porous carbon aerogels are then activated using suitable activating agent to increase the surface area and porosity. Wide varieties of activating agents are commonly used to achieve an increase in surface area and porosity. Few of the commonly used activating agents and their limitations are listed in Table 1.
Table 1: Activating agents commonly used for the synthesis of porous carbon with high surface area and porosity.
Activating agent (s) Molar ratio Advantages Limitations
Potassium Hydroxide (KOH) 1:1, 1:2, 1:3, 1:4 Most widely used activating agent, High surface area, porosity Difficulty in removing potassium from the carbon matrix.
Zinc Chloride (ZnCl2) 1:4 Formation of aromatic graphitic structure. Increased carbon yield. Highly corrosive and usually destroys the chamber of the furnace. Highly toxic.
o-Phosphoric Acid (H3PO4) 1:4 Low temperature activating agent used for carbon from biosource. Toxic and difficulty in cleaning the furnace
ZnCl2-H3PO4 mixture 1:4 High surface area and porosity Highly corrosive and difficulty in cleaning the activated carbon

[0053] Activation of carbon aerogel using KOH proceeds through:
(a) Redox reaction between various potassium compounds and carbon resulting in an etching of carbon framework.
(b) The formation of H2 and CO2 provides physical activation.
(c) Intercalation of potassium in the carbon matrix and its removal by washing leaves micro/meso pores in the lattice.
[0054] Steps involved in the synthesis of insitu activated carbon aerogels
1. Preparation of sol by mixing required quantity of resorcinol, formalin and catalyst system.
2. Dissolution of required quantity of Mn(OAc)4.4H2O (In the present embodiment, the loading was fixed with respect to the quantity of resorcinol) with constant stirring so as to obtain a homogenous sol.
3. Conversion of the sol to gel at ambient conditions followed by solvent exchange using acetic acid solution (2%) and acetone.
4. Drying of the gel at 60 ºC for 24 h and 90 ºC (3 days).
5. Carbonization of the aerogel at 1000 ºC with heating rate of 3 ºC∙min-1, and residence time of 1h under argon atmosphere.

APPLICATIONS
[0055] As insulation systems for use in launch vehicles.
[0056] As electrode material for lithium ion batteries, other types of batteries and supercapacitors.
[0057] As the best material for hydrogen storage. Hydrogen storage capacity is directly related to specific surface area.
[0058] As photocatalyst for the waste water purification.
[0059] As effective adsorbent for CO2 sequestration process.
[0060] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person skilled in the art.
EXAMPLES
[0061] The present invention is further explained in the form of following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the invention.
Example 1:
(A) Method of preparation of an activated carbon aerogel
[0062] The present embodiment reveals the synthesis of activated carbon aerogels through an in-situ doping process. The polycondensation reaction between resorcinol and formaldehyde was carried out in the presence of sodium carbonate (Na2CO3) catalyst. To this solution, different quantities of manganese (II) acetate tetrahydrate (Mn(OAc)4.4H2O) was added. Loading of Mn(OAc)4.4H2O was fixed with respect to resorcinol. Accordingly 0, 5, 10, 15, and 20 wt% of the weight of Mn(OAc)4.4H2O was added to the sol followed by stirring for 1h and allowed to gel in room temperature. The gel was strengthened at 50 ºC (for 1 day) and 90 ºC (3 days), respectively. The strengthened gel was subjected to solvent exchange using 1% acetic acid and acetone followed by drying the gel at 60 ºC (for 2 days). The xerogel was subjected to pyrolysis at 1000 ºC for 1 h under inert (argon) atmosphere. The synthesized porous activated carbon was subjected to detailed analysis.
(B) Characterization
[0063] Morphology: Morphology of the synthesized activated carbon aerogel analysed using scanning electron microscopy (SEM0) confirms a pearl and neck morphology (as presented in FIG. 2(a).
[0064] The TEM images presented in FIG. 2 (b) confirm a highly porous structure with a uniform dispersion of the MnO. X-ray diffraction studies confirmed the presence of MnO. The XRD spectra consisted of peaks at 39.94º, 40.6º, 58.57º, 70.19º with the intensity of the peaks increasing as a function of MnO loading. Raman spectra of activated carbon consist of two main peaks. One at 1332 cm-1 corresponding to defect band and arise due to edge induced structural defects. The second peak is centred around 1587 cm-1 correspond to G band and arise due to the zone centre vibration of C atoms against each other in the layer plane. In addition to this a broad band can be observed around 640 cm-1 which corresponds to Mn-O vibration modes. BET studies shows a combination of type I and type IV isotherms confirming the microporous nature of the synthesised aerogels. The surface area increases with increase in Mn(OAc)4.4H2O loading attaining a maximum of 4764 m2∙g-1 for the 20 wt% doped system as given in Table 2. However, Mn(OAc)4.4H2O loading beyond this limit is not possible due to practical difficulties.
Table 2: Surface area porosity and pore volume obtained from BET studies
Amount of Mn(OAc)4.4H2O Surface area (m2∙g-1) Pore volume (cm3∙g-1) Average pore diameter (nm)
0% doped 965.4 1.067 4.423
5 wt% doped 1399 1.627 4.653
10 wt% doped 2351 2.867 4.877
15 wt% doped 2287 2.773 4.850
20 wt% doped 4764 5.767 4.842

[0065] TGA studies prove two stage decomposition with the first stage decomposition centred on 275 ºC and second stage decomposition around 390 ºC.
Example 3: Comparative data
[0066] A comparison between the present invention and other samples are given in Table 3 below indicating better properties. The activated carbon aerogel of the present invention having a surface area 1399 – 4764 m2∙g-1, pore volume 1.62 – 5.76 cm3∙g-1 and average pore diameter is 4.65 – 4.87.
Table 3: Comparative analysis.
Sample Name Surface area (m2∙g-1) Pore volume (cm3∙g-1) Average pore diameter (nm) Disadvantages
PWAC-0 to 4 (Int. J. Hydrogen Energy, 2024, 50, 324-336) 363.76 – 3728.06 0.32 – 2.21 0.65 – 1.2 KOH activation (Corrosive and hazardous nature, post treatment challenges)
NSCA 600-900 (Int J Biol Macromol., 2024, 274, 133282) 214 – 1035 0.14 – 0.76 0.7 – 1.2 Low pore features
PAC 3:1 – 6:1 (Int. J. Hydrogen Energy, 2025, 141, 803-810) 2845.4 – 3170.7 1.16 – 2.12 1.98 – 2.15 KOH activation
SBACCA (Chemosphere, 2024, 355, 141748) 414 – 497 0.1 – 0.2 1.15 -1.16 Low surface area
Present work 1399 – 4764 1.62 –5.76 4.65 – 4.87

ADVANTAGES OF THE INVENTION
[0067] The activated carbon aerogel has ultra-high surface area ranging from 1399 m3∙g-1 to 4764 m3∙g-1 and a porosity ranging from 76% to 92%.
[0068] The activated carbon aerogel is produced through an eco-friendly route without the usage of any toxic chemicals.
, Claims:1. An activated carbon aerogel has highly porous structure with a uniform dispersion of the MnO and has an ultra-high surface area ranging from 500 m3∙g-1 to 5000 m3∙g-1 and a porosity ranging from 42% to 92%.
2. The activated carbon aerogel as claimed in claim 1, wherein said activated carbon aerogel has a pore diameter ranging from 1 nm to 20 nm and the pore volume ranging from 0.1 cm3∙g-1 to 6.0 cm3∙g-1.
3. The activated carbon aerogel as claimed in claim 1, wherein said activated carbon aerogel has a low density ranging from 0.03 g/cc to 0.5 g/cc.
4. The activated carbon aerogel as claimed in claim 1, wherein said activated carbon aerogel has an X-ray powder diffraction pattern (CuKα) comprising peaks at 2-theta about 34.9º, 40.6º, 58.57º, 70.19º, 73.8°
5. A method of preparation of an activated carbon aerogel comprising:
a) reacting a carbon precursor and a crosslinking agent to a polycondensation reaction in the presence of a catalyst to obtain a first solution;
b) adding a doping agent to the solution with stirring to obtain a second solution;
c) processing the second solution by conversion into a gel;
d) strengthening the gel under heating to obtain a strengthened gel;
e) subjecting the strengthened gel to solvent exchange followed by drying to obtain a xerogel; and
f) subjecting the xerogel to pyrolysis to obtain an activated carbon aerogel.
6. The method as claimed in claim 5, wherein the carbon precursor is selected from a group comprising of resorcinol, melamine, phenol-formaldehyde and combination thereof and has an amount ranging from 5 to 35 wt%.
7. The method as claimed in claim 5, wherein the crosslinking agent is selected from a group comprising of formaldehyde, melamine, APTES and combination thereof and has an amount ranging from 15 to 30 wt%.
8. The method as claimed in claim 5, wherein the catalyst is selected from a group comprising of sodium carbonate, sodium hydroxide, hydrochloric acid and combination thereof and has an amount ranging from 0.1 to 3 wt%.
9. The method as claimed in claim 5, wherein the doping agent is selected from a group comprising of manganese (II) acetate tetrahydrate, zinc chloride and combination thereof and has an amount ranging from 5 to 20 wt%.
10. The method as claimed in claim 5, wherein the second solution in step c) is stirred at a speed ranging from 200 to 800 RPM for a time period of 0.1 h to 2 h.
11. The method as claimed in claim 5, wherein the strengthening in step d) by drying the gel at a temperature ranging from 40 to 60 °C for a time period ranging from 20 to 28 hrs followed by drying at a temperature ranging from 80 to 100 °C for a time period ranging from 2 to 4 days.
12. The method as claimed in claim 5, wherein the solvent in step e) is selected from a group comprising of acetic acid, acetone, water, ethanol and combination thereof.
13. The method as claimed in claim 5, wherein the drying in step e) is carried out at a temperature range from 50 to 70 °C for a time period ranging from 1 to 3 days.
14. The method as claimed in claim 5, wherein the pyrolysis in step f) is carried out at a temperature range from 900 to 1100 °C for a time period ranging from 0.1 h to 2 h.