FIELD OF THE INVENTION

[0001] The present disclosure relates generally to the field of environmental chemical engineering. Specifically, the disclosure is directed to a process of preparing three-dimensional carbon from Prosopis Juliflora. Said carbon may be employed in a flow field plate in a fuel cell.
BACKGROUND OF THE INVENTION
[0002] 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. [0003] The world is predominantly dependent on non-renewable resources like fossil fuels- coal, petroleum etc. With industrialization and modernization the demand for energy is ever increasing. With the constant depletion of these resources and their finite availability, the need to switch to alternate sources of energy has increased manifold. This is also fueled by the need to decrease global warming and air pollution caused by use of fossil fuels for example - an internal combustion engine generates carbon dioxide, carbon monoxide and other particulate matters that pollute the environment. Research is currently focused on developing alternate sources of energy that are renewable like wind energy, solar energy and hydrothermal energy and involve low optimization costs. Solar cells and fuel cells are some of the extensively studied fields of renewable energy. However, the problem with solar cells is their high fabrication costs, limitations on solar intensity and time of availability.
[0004] Fuel cells convert chemical energy of a fuel to electrical energy and are one of the most promising and eco-friendly energy sources, as they produce only clean water as byproduct. Most fuel cells employ hydrogen and oxygen as fuels. Hydrogen for such cells may be fed to the cell directly or may be synthesized within using a system that generates hydrogen from for example, alcohol. Alcohol, precisely ethanol is effective because it has high specific energy and can be easily produced from bio-waste using microorganisms. In proton exchange

membrane fuel cells (also called PEM) hydrogen gets oxidized at the anode to release hydrogen ions, which cross the membrane into the cathodic chamber where they combine with oxygen to generate water. Electrons move from the anode through an external circuit to the cathode to generate electricity. When flow channels are provided on the electrodes, cathode or anode, for reactants to flow, they are termed as fluid flow field plates. Currently, graphite based compounds are used for preparing the plates. The graphite used is layered natural graphite with thermal and electrical conductivity. However, natural graphite has low, non-uniform porosity and not all graphite is suitable for fuel cells. Further, graphite is not easily renewable in nature. For the ever-growing demand in energy in modern technology combined with global economic growth, there is a need to move to natural recyclable materials. There is a scope for developing synthetic graphite or graphitic structure with desired characteristics-like high porosity and efficacy-from plants.
[0005] Prosopis Juliflora or mesquite is a small tropical plant grown predominantly in the American continent in countries like Brazil and Mexico. It has been known as an invasive plant that grows wildly in open and barren lands. It can be grown in tough environmental conditions. Prosopis Juliflora has been explored for generating alcohol. Processes of preparing carbon from Prosopis Juliflora known in the art are not very efficient or cost-sensitive. [0006] For any application, regular carbon nature is highly desired. Plants carbon biochars have low electrical and thermal conductivity. The development of 3D-carbon network was done using templating methods which are time consuming processes with less cost effectiveness.
[0007] There exists a need for novel approaches that use natural, recyclable sources for producing three-dimensional carbon. The inventors of the present disclosure employ Prosopis Juliflora as a source and provide a process of preparing high efficiency three-dimensional carbon from the same.

OBJECTS OF THE INVENTION
[0008] An object of the present disclosure is to provide a process of preparing three-dimensional carbon from Prosopis Juliflora.
[0009] An object of the present disclosure is to provide a process of preparing three-dimensional carbon from Prosopis Juliflora that is efficient and cost-effective.
[0010] Another object of the present disclosure is to provide a process of preparing three-dimensional carbon that is recyclable and has high porosity and uniformity.
[0011] Still another object of the present disclosure is to provide a process of preparing three-dimensional carbon from Prosopis Juliflora, wherein the carbon has high efficiency in a fuel cell for renewable generation of electricity and water. [0012] Another object of the present disclosure is to utilize the invasive plant Prosopis Juliflora that disrupts the biodiversity of a region.
SUMMARY OF THE INVENTION
[0013] 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.
[0014] Prosopis Juliflora is a weed that has an invasive effect on crops and thus destroys biodiversity. Conversion of these invasive plants to useful materials is not just economic, but is also eco-friendly. The present disclosure provides a process to convert the weed to useful activated carbon. The synthetic carbon is sourced from natural, recyclable plant and can be used in fuel cells to generate electricity and water.
[0015] In an aspect, the present disclosure relates to a process of preparing three-dimensional carbon from Prosopis Juliflora comprising the steps of:
(a) collecting a part of Prosopis Juliflora and hydroxylating with an alkali
hydroxide to produce lignin free cellulose;

(b) carbonizing the cellulose obtained in (a) under hydrogen gas in an inert
atmosphere to produce carbon;
(c) activating the carbon with sodium potassium tartrate and sodium bicarbonate to generate activated carbon; and
(d) depositing metal nano-particles in the activated carbon to give the three-dimensional carbon.
[0016] In an embodiment, the three-dimensional carbon may be fabricated into a number of carbon devices, specifically a flow field plate. The plate may be used in development of an efficient energy harvesting device such as a fuel cell. [0017] In another aspect, the present disclosure relates to three-dimensional carbon obtained by a process comprising the steps of:
(a) collecting a part of Prosopis Juliflora and hydroxylating with an alkali hydroxide to produce lignin free cellulose;
(b) carbonizing the cellulose obtained in (a) under hydrogen gas in an inert atmosphere to produce carbon;

(c) activating the carbon with sodium potassium tartrate and sodium bicarbonate to generate activated carbon; and
(d) depositing metal nano-particles in the activated carbon to give the three-dimensional carbon.
[0018] In another aspect, the present disclosure relates to a fuel cell comprising a flow field plate fabricated from three-dimensional carbon obtained by a process comprising the steps of:
(a) collecting a part of Prosopis Juliflora and hydroxylating with an alkali hydroxide to produce lignin free cellulose;
(b) carbonizing the cellulose obtained in (a) under hydrogen gas in an inert atmosphere to produce carbon;
(c) activating the carbon with sodium potassium tartrate and sodium bicarbonate to generate activated carbon; and
(d) depositing metal nano-particles in the activated carbon to give the three-dimensional carbon.

[0019] Other aspects of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learnt by the practice of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] 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.
[0021] 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. [0022] 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.
[0023] In some embodiments, numbers have been used for quantifying weight, percentages, temperatures, 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. 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.
[0024] Various terms as used herein are shown below. To the extent a term used in a claim 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.
[0025] 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. [0026] Unless the context requires otherwise, throughout the specification which follow, 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."
[0027] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. [0028] All methods described herein can be performed in any 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. [0029] 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.
[0030] 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.
[0031] 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. [0032] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments. [0033] 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.
[0034] Prosopis Juliflora is a fast growing, drought resistant shrub. It can grow in the most arid regions of the world and can prevent soil erosion. Its fruits are

fodder for animals and the trees have healthy green foliage. Its wood is rich in fiber and has been used for household cooking or production of paper. Interestingly, it can capture harmful metals from polluted soil. Therefore, this tree can be grown in polluted areas where industrial waste is dumped or where the soil is polluted.
[0035] Multiple reasons may be cited for usage of invader trees for the present process. There is already a scarcity of drinking water, specifically ground water. Mismanagement of ground water and random growth of invader trees further depletes it. Additionally, the unrestrained growth of Prosopis Juliflora is also a threat to wildlife or biodiversity. Development of carbon or carbon based fuel cells using Prosopis Juliflora is bio degradable, cost effective and environment-friendly. These fuel cells advantageously generate pure water as a byproduct. [0036] In an embodiment, the present disclosure relates to a process of preparing three-dimensional carbon from Prosopis Juliflora comprising the steps of:
(a) collecting a part of Prosopis Juliflora and hydroxylating with alkali hydroxide to produce lignin free cellulose;
(b) carbonizing the cellulose obtained in (a) under hydrogen gas in an inert atmosphere to produce carbon;

(c) activating the carbon with sodium potassium tartrate and sodium bicarbonate to generate activated carbon; and
(d) depositing metal nano-particles in the activated carbon to give three-dimensional carbon.
[0037] In an embodiment, the part of Prosopis Juliflora used may be selected
from the group comprising of root, leaves, shoots, fruits, seed, stem, bark, branch,
flower, bud and combinations thereof. Preferably the part oi Prosopis Juliflora is
the stem, root, branch, or combinations thereof.
[0038] In an embodiment, after collecting the part oi Prosopis Juliflora it may be
washed and soaked in salt water before use.
[0039] In an embodiment, the hydroxylation of Prosopis Juliflora is done to
remove lignin from the cellulose. Lignin has potential value in different polymer
industries and may be employed therein. Lignin is the binding structural tissue in

the cell walls of plants. Hydroxylation has conventionally been performed with
dilute acid treatment. In the present invention, alkali hydroxide is employed for
hydroxylation wherein the alkali hydroxide may be selected from the group
comprising of sodium hydroxide, potassium hydroxide, and combination thereof.
The use of alkali hydroxide provides a cost effective solution and also does not
release any harmful residues.
[0040] In an embodiment, the concentration of alkali hydroxide may range from
about 2M to about 10M.
[0041] In an embodiment, the hydroxylation may be carried out at medium
temperature. The temperature for hydroxylation may fall within the range of about
85°C to about 100°C.
[0042] In an embodiment, the hydroxylation step (a) may be followed by
treatment with hydrogen peroxide along with an oxidizing agent. In an
embodiment, the oxidizing agent may be selected from the group comprising of
oxidanyl, oxalyl chloride, and combinations thereof. In some embodiments, the
oxalyl chloride may be present in a concentration of about 2M in methylene
chloride. Said process step may be employed to improve the surface roughness of
cellulose and for opening of more hydroxyl groups.
[0043] In an embodiment, Prosopis Juliflora may be treated with sodium nitrate
treatment followed by acetone for removal of lignin.
[0044] In an embodiment, the cellulose obtained may be further carbonized using
hydrogen gas under an inert atmosphere, wherein the inert atmosphere may be
selected from nitrogen, argon, helium, or any other noble gas atmosphere. In a
preferred embodiment, the inert atmosphere may be an argon atmosphere.
[0045] In an embodiment, the carbonizing may be performed in the temperature
range of about 600 °C to about 1200°C, preferably it falls in the range of about
950 °C to about 1100°C. In an embodiment, the carbonization may be done at 600
°C in argon atmosphere and thereafter the temperature may be increased up to
900-1000 °C. In the present disclosure, carbonization is carried out at lower
temperatures first. After high temperature carbonization, graphitic carbon gets
generated that has good thermal and electrical conductivity, rather than

amorphous carbon from any bio-mass. The process removes the oxygenated groups from the carbon surface thereby increasing the electrical conductivity, thermal conductivity and graphitic nature of the carbon.
[0046] In this methodology, the fibril structures of cellulose are used as carbon source, after carbonization it gets converted in graphitic high electrical and thermal conducting carbon network. In contrast, the known methods use lignin and ligno cellulose and carbonize the same, resulting in the non-uniformity of the carbon structure with irregular porosity. The technique of the present disclosure is facilitated to make an efficient electrode structure where the catalytic metal precursors easily deposit on the surface of carbon.
[0047] In an embodiment, the activation with sodium potassium tartrate and sodium bicarbonate gives an exfoliation and activation to the carbon to improve the porosity and electrical conductivity. The activation may be carried out in the temperature range of about 250 °C to about 325 °C. This step of activation is performed at a much lower temperature compared to the temperatures of above 700 °C carried out in sodium hydroxide. Thus, the activation step consumes much lesser energy, making the overall process more efficient and economical. [0048] In an embodiment, the activated carbon obtained in step (c) has high surface area and high porosity. Further, the activated carbon also has good thermal and electrical conduction properties.
[0049] In an embodiment, the surface area of the activated carbon may fall in the range of about 400 m2/g to about 3000 m2/g.
[0050] In an embodiment, the activated carbon obtained is further embedded with metal nano-particles in the inter layers. Any metal nano-particles suitable to improve the conductivity of the carbon may be employed. Preferably, the nano-particles are chosen suitably for a direct alcohol fuel cell (DAFC), specifically a direct ethanol fuel cell (DEFC). The metal nano-particles to be deposited may be selected from the group comprising of cobalt, tin, iron, erbium, gold, palladium, platinum, or combinations thereof.
[0051] In an embodiment, the metal nano-particles may be deposited in the activated carbon via any process known in the art, including but not limited to,

electrochemical deposition, chemical reduction, solvothermal deposition, atomic layer deposition method, or their combination.
[0052] In an embodiment, the three-dimensional carbon may be fabricated into a number of carbon devices, specifically a flow field plate. The plate may be used in development of an efficient energy harvesting device such as a fuel cell. [0053] In an embodiment, the three-dimensional carbon obtained via the above process may be further fabricated, using processes well known in the art to produce flow field plates. The functionalized and carbonized wood may be compressed and molded according to requirement into different layers. The pair of fuel cell plate may be set according to the energy requirement. [0054] In an embodiment, the flow field plates may be fabricated with different flow channels, including serpentine, interdigitated, parallel, pin-type, or combinations thereof. Most preferably, the flow channel may be a serpentine channel.
[0055] In an embodiment, the flow field plates may be employed in a fuel cell, especially in a direct methanol fuel cell, or direct ethanol fuel cell (DEFC). In an embodiment, the flow field plates may be used as cathode or anode conductive plate.
[0056] In another embodiment, the three-dimensional carbon is recyclable and has high chemical resistance. The obtained carbon has a regularized structure. The three-dimensional carbon obtained from the present invention may possess high electrical conductivity, suitable for electrode formation for fuel cells. In an embodiment, the electrical conductivity may fall in the range of about 10 to about 300 S/m.
[0057] In an embodiment, the three-dimensional carbon obtained has uniformity, high porosity and high surface to volume ratio. Plant cells are made of cellulose fiber where the lignin holds the fiber tightly. After the removal of lignin, the cellulose fibers remain in plant cell, which are later converted to three-dimensional carbon. Therefore, uniformity is generated in carbonized cellulose fiber by the process and the exfoliation improves the porosity in the carbon structures. The porosity may fall in the range of about 6 to about 10 nm.

[0058] In an embodiment, the three dimensional carbon possesses high thermal conductivity. The thermal conductivity may be about 50 W/mK. [0059] In an embodiment, the three dimensional carbon is stable and highly durable.
[0060] The process of the present disclosure uses natural and renewable source -Prosopis Juliflora and low cost chemicals for its processing into three-dimensional carbon, making it an environmentally friendly and economic process. The process employs Prosopis Juliflora thereby decreasing the invader plants and encouraging biodiversity. The process is conducted in the organic environment, which is not explosive and no toxic gasses are generated.
[0061] In another embodiment, the present disclosure relates to three-dimensional carbon obtained by a process comprising the steps of:
(a) collecting a part of Prosopis Juliflora and hydroxylating with alkali hydroxide to produce lignin free cellulose;
(b) carbonizing the cellulose obtained in (a) under hydrogen gas in an inert atmosphere to produce carbon;
(c) activating the carbon with sodium potassium tartrate and sodium
bicarbonate to generate activated carbon; and
(d) depositing metal nano-particles in the activated carbon to give three-
dimensional carbon.
[0062] In another embodiment, the present disclosure relates to a fluid field plate fabricated by a three-dimensional carbon obtained by a process comprising the steps of:
(a) collecting a part of Prosopis Juliflora and hydroxylating with alkali hydroxide to produce lignin free cellulose;
(b) carbonizing the cellulose obtained in (a) under hydrogen gas in an inert atmosphere to produce carbon;
(c) activating the carbon with sodium potassium tartrate and sodium
bicarbonate to generate activated carbon; and
(d) depositing metal nano-particles in the activated carbon to give three-
dimensional carbon.

[0063] In another embodiment, the present disclosure relates to a fuel cell comprising a flow field plate fabricated from three-dimensional carbon obtained by a process comprising the steps of:
(a) collecting a part of Prosopis Juliflora and hydroxylating with an alkali hydroxide to produce lignin free cellulose;
(b) carbonizing the cellulose obtained in (a) under hydrogen gas in an inert atmosphere to produce carbon;
(c) activating the carbon with sodium potassium tartrate and sodium bicarbonate to generate activated carbon; and
(d) depositing metal nano-particles in the activated carbon to give the
three-dimensional carbon. [0064] In another embodiment, the present disclosure relates to a fuel cell comprising the flow field plate obtained from Prosopis Juliflora. Preferably, the disclosure relates to a direct ethanol fuel cell comprising the flow field plate obtained from Prosopis Juliflora. The fuel cell has low optimization requirements. For the development of ethanol based fuel cell the primary conditions of the device-materials are high electrical conduction and high thermal transportations. These properties are easily available in graphitic carbon, but it suffers from low porosity and is non-recyclable. In contrast, the plants carbon biochars suffer from low electrical and thermal conductivity. The present disclosure overcomes these deficiencies.
[0065] In an embodiment, a membrane separating cathode with anode of the fuel cell may be made of a proton permeable membrane, including but not limited to polybenzimidazole or Nafion™.
[0066] In an embodiment, the fuel cell of the present disclosure may be used to generate pure water. The fuel cell can replace conventional sources of energy including fossil fuels. The fuel cell does not generate green house gases or pollution making it eco-friendly.
[0067] In an embodiment, the direct ethanol fuel cell prepared using the three-dimensional carbon prepared by the process of the present disclosure has higher efficiency. The natural arrangement of cellulose fiber in the present disclosure

helps to create uniform architecture for uniform flow of ethanol however, in other carbons (not aligned) the flow of ethanol is not uniform so efficiency decreases dramatically, the out flow of electrons is irregular. But the 3D carbon of this disclosure has a regular arrangement after carbonization.
[0068] In an embodiment, the fuel cell may be used in the automobile industry such as hybrid vehicles, in portable electronic devices like portable charger, medical devices, space equipment, and as backup power in commercial or residential areas.
[0069] 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 scope of the invention is determined by the claims that follow. 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 having ordinary skill in the art. EXAMPLES
[0070] The disclosure will now be illustrated with working examples, which is intended to illustrate the working of disclosure and not intended to take restrictively to imply any limitations on the scope of the present disclosure. Although methods and materials similar or equivalent to those described herein can be used in the practice of the disclosed methods and compositions, the exemplary methods, devices and materials are described herein. It is to be understood that this disclosure is not limited to particular methods, and experimental conditions described, as such methods and conditions may vary. [0071] MATERIALS AND METHODS: Prosopis Juliflora was obtained from nearby agricultural land in Punjab, India. [0072] EXAMPLE 1
[0073] 80g chunks of wooden pieces were collected from the plant Prosopis Juliflora and soaked in IM table salt (NaCl) solution in water for 24 hours at room temperature in normal environmental conditions. Performed alkali hydroxide treatment with 2M sodium hydroxide for the removal of lignin and for

extraction of cellulose. About 60% of the total weight of wood was extracted as lignin while cellulose was obtained in about 20% of the total weight. The extracted cellulose was carbonized in presence of hydrogen flow in an Argon environment. The temperature was set at 600°C and then gradually raised up to 900°C. The carbonized materials were highly porous, had good thermal and electrical conduction properties. Said carbonized material was subjected to treatment with sodium potassium tartrate and sodium bicarbonate to give activated carbon. Average BET average surface area value of the activated carbon was noted to be around 480 m2/g. 100 mL of 0.01M ascorbic acid and noble metals -Pd, Pt and Au were added to the activated carbon to perform chemical reduction. The required binary ethanol oxidation metals nano-particles were embedded in the interlayer of carbonized cellulose by surface absorption. The metal deposited carbon materials can be used to fabricate flow field plates for ethanol fuel cell. [0074] The three-dimensional carbon was obtained in a yield of about 20% with respect to the amount of wooden pieces used. Electrical conductivity of the carbon was found to be about 280 S/m. The high average surface area and electrical conductivity values indicate that the synthesized carbon is highly porous with a good electrical conductivity.
[0075] From the foregoing, it will be appreciated that, although specific embodiments of the invention have been described herein merely for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention and should not be construed so as to limit the scope of the invention or the appended claims in any way.
ADVANTAGES OF THE PRESENT INVENTION
[0076] The present disclosure provides a process of preparing a three-dimensional
carbon from Prosopis Juliflora.
[0077] The present disclosure converts the invader plants Prosopis Juliflora to
useful three-dimensional carbon thereby conserving biodiversity.
[0078] The present disclosure provides an efficient, cost-effective process of
preparing three-dimensional carbon.

[0079] The process of the present disclosure produces carbon that has high
porosity and high uniformity.
[0080] The process of the present disclosure provides an alternative source of
graphitic carbon, which is made from plant cellulose fiber.
[0081] The three-dimensional carbon of the present disclosure can be employed in
a fuel cell to renewably generate electricity and water.

We Claim:

1. A process of preparing three-dimensional carbon from Prosopis Juliflora
comprising the steps of:
(a) collecting a part of Prosopis Juliflora and hydroxylating with alkali hydroxide to produce lignin free cellulose;
(b) carbonizing the cellulose obtained in (a) under hydrogen gas in an inert atmosphere to produce carbon;

(c) activating the carbon with sodium potassium tartrate and sodium bicarbonate to generate activated carbon; and
(d) depositing metal nano-particles in the activated carbon to give three-dimensional carbon.

2. The process as claimed in claim 1, wherein the part oi Prosopis Juliflora is selected from the group comprising of root, leaves, shoots, fruits, seed, stem, bark, branch, flower, bud and combinations thereof.
3. The process as claimed in claim 1, wherein the alkali hydroxide is selected from the group comprising of sodium hydroxide, potassium hydroxide and combination thereof.
4. The process as claimed in claim 1, wherein temperature for hydroxylation falls within the range of 85°C to 100°C.
5. The process as claimed in claim 1, wherein the inert atmosphere is selected from argon, nitrogen or helium atmosphere.
6. The process as claimed in claim 1, wherein carbonizing is performed in the temperature range of 600 °C to 1200°C.
7. The process as claimed in claim 1, wherein the activation is carried out in the temperature range of 250 °C to 325 °C.
8. The process as claimed in claim 1, wherein the surface area of the activated carbon falls in the range of 400 to 3000 m2/g.
9. The process as claimed in claim 1, wherein the metal nano-particles to be
deposited is selected from the group comprising of cobalt, tin, iron, erbium, gold,
palladium, platinum, or combinations thereof.

10. The process as claimed in claim 1, wherein the metal nano-particles are deposited in the activated carbon by electrochemical deposition, solvothermal deposition, chemical reduction, atomic layer deposition or a combination thereof.
11. The process as claimed in claim 1, wherein the three-dimensional carbon is fabricated into a flow field plate.
12. The process as claimed in claim 1, wherein electrical conductivity of carbon falls in the range of 10 to 300 S/m.
13. The process as claimed in claim 1, wherein porosity of carbon falls in the range of 6 nm to 10 nm.
14. The process as claimed in claim 1, wherein thermal conductivity of carbon is 50 W/mK.
15. A fuel cell comprising a flow field plate fabricated by the three-dimensional carbon obtained by the process as claimed in claim 1.
16. The fuel cell as claimed in claim 15, wherein the fuel cell is a direct ethanol fuel cell.