WO2011117657A2

WO2011117657A2 - Carbon materials comprising nano structures

Info

Publication number: WO2011117657A2
Application number: PCT/GB2011/050621
Authority: WO
Inventors: Shenmin Zhu; Di Zhang; Qinglei Liu; Wang ZHANG; Jiajun Gu
Original assignee: Shanghai Jiao Tong University; The Morgan Crucible Company Plc
Priority date: 2010-03-26
Filing date: 2011-03-28
Publication date: 2011-09-29
Also published as: WO2011117657A3

Abstract

A method is disclosed of making a nano-structured carbon material by:- A)i)providing a porous carbon material having porosity; ii)impregnating a metallic material capable of catalyzing carbon nano structure growth within the porosity of the porous carbon material of step i) to provide an impregnated porous carbon material; or, B)providing an impregnated porous carbon material produced bysteps i) and ii); and, C)heating the impregnated porous carbon material to a temperature sufficient to promote carbon nano structure growth within the porosity of the carbon material to provide a nano-structured carbon material. The resulting material can be loaded with metal oxides.

Description

CARBON MATERIALS COMPRISING NANO STRUCTURES

This invention relates to carbon materials comprising nano-structures. Background

Carbon comes in many forms, including as: amorphous materials; diamond or diamond-like materials; graphite and graphitic materials; as nano-structured materials such as graphene, nanofibres, nanotubes or fullerenes; and as combinations thereof.

Activated carbon is one kind of carbon material used for many industrial and civil applications. Activated carbon is generally produced from carbonaceous source materials, for example nutshells, peat, wood, coir, lignite, coal and petroleum pitch. Activated carbon has a very strong adsorptive capacity for inorganic or organic matter because it has a well-developed hole structure and a high specific surface area. A typical specific surface area might be of the order of 500m². g ¹ to 1500 m².g^_1

[although the present invention is not limited to this range].

Therefore, activated carbon is traditionally used in gas and water treatment. Activated carbon removes deleterious substances from gas or solution by absorbing them onto its interfaces and surfaces. The absorptive mechanism of activated carbon includes physical absorption and chemical absorption. Physical absorption is the primary mechanism for conventional activated carbon. In recent years, there has been increasing interest in enhancing the chemical absorption of activated carbon by introducing functional groups onto the interfaces and surfaces of the activated carbon via a strong acid or alkali treatment method.

Besides environmental protection and water treatment, porous carbon is also used in other industrial applications, such as catalyst support and energy storage, for their advantages of high porosity, good resistance to corrosion, electrochemical stability, high temperature resistance. In recent years, technologies for loading functional organic or inorganic particles or membranes onto interfaces or surfaces of porous carbons have been explored to realize new applications of porous carbons. Electrochemical supercapacitors are a new type of energy storage device with capabilities between those of a normal capacitor and a secondary battery.

Supercapacitors combine the features of high energy density, high power density, and long life. They have a wide range of working temperature, rapid charge and discharge, and long cycle life. Since no emissions are associated with the release of energy stored in a supercapacitor, supercapacitors have a wide range of potential applications in communication technology, information technology, home appliances, electric vehicles and aerospace.

By their working principles, supercapacitors can be divided into two types:

• Electric double layer capacitors established on the basis of interface double electrical layers, and Faraday pseudo capacitor established by an oxidation and reduction process on two or three dimensional material surface. Carbon electrode materials with high specific surface area are typical electric double layer capacitors, but their specific capacitance is relatively lower

(e.g. 50-100F g^"1).

• Faraday pseudo capacitors are based on Faraday processes, and in particular on the electrochemical process of Faraday charge transfer. This not only happens in the surface of electrode, but also goes into the deep interior of the electrode, so it can achieve a capacitance and energy density higher than that of an electric double layer capacitor.

Some metal oxides and hydrates are very good electrode materials for supercapacitor. Ruthenium (Ru) oxide and hydrate has a good performance as supercapacitor material, but Ru is a precious metal and expensive. There is therefore a need for other cheaper metal oxides in place of Ru. For example, manganese oxide, tin oxide, nickel oxide, cobalt oxide, vanadium pentoxide are some of the potential material for a supercapacitor. However, in the oxidation and reduction process, an oxide material can have a change in the valence state which may be accompanied by structural change: consequently the electrochemical performance can decay with use. In contrast, carbon material with electrical double layer capacitor performance is very stable in its own. So, the hybrid supercapacitor, a composite of nano metal oxide and carbon composite material, combines the strength of both and makes a composite electrode material with better electrochemical performance.

In the area of hybrid supercapacitor, Chinese Patent 200410013069.4 reported a preparation method to evenly coat nano metal oxide on the surface of carbon nanotubes. Carbon nanotubes have a graphite-like chemical bond, high crystallization, good conductivity, and a quasi one-dimensional electrical structure which allows them to carry high current, so they are regarded as suitable materials for

supercapacitor. However, carbon nanotubes have a high production cost.

The invention

The applicants have realised that activated carbon materials can provide a suitable substrate for growth of nano-structured carbon within the porosity of the carbon and that the resultant materials are useful in a wide range of applications.

Accordingly, in a first aspect, the present invention provides a method of making a nano-structured carbon material by:-

A) i) providing a porous carbon material having porosity; and

ii) impregnating a metallic material capable of catalyzing carbon nano structure growth within the porosity of the porous carbon material of step i) to provide an impregnated porous carbon material;

or,

B) providing an impregnated porous carbon material produced by steps i) and ii);

and,

C) heating the impregnated porous carbon material to a temperature

sufficient to promote carbon nano structure growth within the porosity of the carbon material to provide a nano-structured carbon material.

By nano-structured carbon material is meant a material in which a porous matrix carbon comprises carbon nano structures within the porosity of the material. Further features and aspects of the invention are evident in the appended claims and in the light of the following illustrative but non- limitative description and the drawings in which :-

Fig. 1 is a transmission electron microscope micrograph of a tin oxide/in-situ self growth nano carbon composite material; and

Fig. 2 is an X-ray diffraction trace of a tin oxide/in-situ self growth nano carbon composite material.

Chinese patent application 201010133489.1, from which this application claims priority, discloses :-

1) Carbonising a biological precursor under vacuum or an inert atmosphere at temperatures between 400-1000°C.

2) Activating the carbonized material via an appropriate physical or chemical activation process to adjust its porous structure;

3) Impregnating the porous carbons made in step 2) with an element M precursor solution, and filtering and desiccating the mixture;

4) Calcining the resulting mixture between 300-1000°C under a vacuum or inert atmosphere to get porous carbons loaded with a functional oxide M_xO_y, where M is one or two of Ti, Fe, Ni,Co, Zn, Cu, Mn, Zr, Cr, Al, Sn, Y, Ce, La, Pb, Pd, Ru, Sr, In, Ga, Bi or Si, X is one of the 1 ,2 or 3, Y is one of 1,2,3 or 4.

The activation step 2) comprises either:

• heating samples at 300-1000°C for 1-12 h under a C0₂, steam or air

atmosphere;

or

• mixing an activator KOH, ZnCl₂ or Fe(N0₃)₂ with the carbonised material and heating the mixture 300-1000°C for 1-12 h under a vacuum or inert atmosphere.

Chinese patent application 201010204539.0 , from which this application claims priority, discloses carbon materials produced by a process comprising the steps of:- a) The preparation of in-situ self growth nano carbon matrix material; b) The surface treatment of the carbon matrix material;

c) The preparation of metal oxide precursor;

d) Placing the carbon material of step (b) into the precursor of step (c), and

treating ultrasonically to make the material.

In detail:

Step a) comprised:

i) a porous carbon material having porosity [e.g. activated carbon] is provided; ii) a metallic material capable of catalyzing carbon nano structure growth from the carbon of the carbon material is impregnated into the porosity of the porous carbon material [e.g. Fe(N03)3'9H₂0];

iii) the impregnated porous carbon material is heated to a temperature sufficient to promote carbon nano structure growth within the porosity of the carbon material to provide a nano-structured carbon material.

Step b) comprised treating the resultant material with concentrated nitric acid to oxidise the carbon surface

Step c) comprised making a metal salt solution.

Step d) comprised ultrasonically treating a suspension of the material of step b) in the solution of step c).

It will be evident by comparison that steps 1) and 2) of Chinese patent application 201010133489.1 and steps a) and b) of Chinese patent application 201010204539.0 are capable of providing a nano-structured carbon material as the activator of Chinese patent application 201010133489.1 includes iron nitrate which is used to promote nanostructure growth in Chinese patent application 201010204539.0.

By nano-structured carbon material is meant a material in which a porous matrix carbon comprises carbon nano structures within the porosity of the material. By carbon nano structures is meant carbon structures different in form from the porous carbon matrix and having nanometric scale [e.g. less than ΙΟμιη, or less than Ιμιη, or even less than 0.1 μιη] . The disclosure of Chinese patent application 201010133489.1

Chinese patent application 201010133489.1 states that it uses biomass material as a source, including as examples agricultural wastes or aquatic plants such as straw, rice husk, coconut shell, husk shell, cotton fibre, fruit stone, wheat straw, corn cob, sawdust, bamboo or water bamboo, algae and water hyacinth.

By using biomass materials as a precursor, it is disclosed as possible to provide both inexpensive starting materials, and materials whose morphology may be chosen to meet the demands of the application.

Traditional activated carbon normally has a large amount of micro-pores [pore diameter <2 nm] so it is difficult to introduce and load functional oxide materials into the holes.

By carbonizing biological materials, the texture morphology and porous structure of the raw materials is to some extent inherited in the carbonized material. Since plant materials are abundant and vary in morphology, texture, and structure on a range of scales it is possible to select an appropriate biomass material whose morphology, texture and structure are likely to be beneficial, in carbonised form, to the intended application.

Porous carbon may be obtained that not only has relatively large surface area, but also has a high proportion of mesopores [e.g. pore diameter 2-50nm] and macropores [pore diameter >50nm] through selecting the appropriate material and controlling the activation process.

The above mentioned M precursor of Chinese patent application

201010133489.1 may include, for example, one or more of the nitrate, chloride, sulphate, acetate or alkoxide of the element M, and may be, or include, ferric nitrate, cobaltous nitrate, nickel nitrate, zinc nitrate, cerium nitrate, cupric nitrate, aluminium nitrate, yttrium nitrate, manganous nitrate, zirconium nitrate, chromic nitrate, lanthanum nitrate, tin nitrate, lead nitrate, palladium nitrate, ruthenium nitrate, strontium nitrate, indium nitrate, gallium nitrate, bismuth nitrate, titanium trichloride, titanium tetrachloride, zinc chloride, cerium chloride, cupric chloride, aluminium chloride, tin tetrachloride, yttrium chloride, manganese chloride, zirconium chloride, chromic chloride, ferric chloride, ferrous chloride, nickel chloride, cobaltous chloride, lanthanum chloride, lead chloride, palladium chloride, ruthenium chloride, strontium chloride, indium chloride, gallium chloride, bismuth chloride, titanium sulphate, aluminium sulphate, zinc sulphate, ferrous sulphate, chromic sulphate, nickel sulphate, cupric sulphate, palladous sulphate, cerous sulphate, indium sulphate, manganese sulphate, gallium sulphate, bismuth sulphate, zinc acetate, cerium acetate, cupric acetate, aluminium acetate, yttrium acetate, manganese acetate, zirconium acetate, ferrous acetate, ferric acetate, nickel acetate, cobalt acetate, lanthanum acetate, lead acetate, palladium acetate, ruthenium acetate, strontium acetate, indium acetate, gallium acetate, bismuth acetate, tetrabutyl titanate, tetrabutoxide, titanium tetraethoxide (TEOT), metatitanic acid, titanic acid, isopropyl titanate or tetraethyl orthosilicate (TEOS).

The above mentioned functional oxide MxOy may include, for example, one or more of Ti0₂, Fe₃0₄, Fe₂0₃, FeO, NiO, Ni₂0₃, Co₃0₄, CoO, ZnO, CuO, MnO, Mn0₂, Zr0₂, Cr₂0₃, Cr0₂, A1₂0₃, Sn0₂, Y₂0₃, Ce0₂, La₂0₃, PbO, Pb0₂, PdO, Pd0₂, Ru0₂, Ru0₄, SrO, Sr0₂, ln₂0₃, Ga₂0₃, Bi₂0₃ and Si0₂.

Example one

Rice husk is cleaned, dried and crushed to powder. The powder is then carbonized at 400°C for 6 hours at an increasing rate of l°C/min under a vacuum condition. The obtained powder is mixed with KOH by a weight ratio of 1 :0.1 , and the mixture is activated by increasing temperature to 1000°C for 1 hour at an increasing rate of 5°C/min under the protection of nitrogen atmosphere to produce porous carbon. Porous carbon is impregnated with a nitric acid titanium solution for 12 hours, and is filtered and dried. Then, the mixture is heat-treated at 1000 ^c for half an hour at an increasing rate of 20°C /min under the protection of nitrogen atmosphere to produce porous carbon loaded Ti0₂.

Example two

Wheat straw is cleaned, dried and crushed to powder. The powder is then carbonized at 1000°C for half an hour at an increasing rate of 10°C/min under a vacuum condition. The obtained powder is mixed with ZnCl₂ by a weight rate of 1 :3, and the mixture is activated by increasing temperature to 650°C for 6 hours at an increasing rate of 10°C/min under the protection of nitrogen atmosphere to produce porous carbon. Porous carbon is impregnated with a tin nitrate solution for 12 hours, and is filtered and dried. Then, the mixture is heat-treated at 400°C for 3 hours at an increasing rate of 10°C /min under the protection of nitrogen atmosphere to produce porous carbon loaded Sn0₂.

Example three

Coconut shell is cleaned, dried and crushed to powder. The powder is then carbonized at 1000 °C for 2 hours at an increasing rate of 20°C/min under a vacuum condition. The obtained powder is mixed with KOH by a weight rate of 1 :3, and the mixture is activated by increasing temperature to 300°C for 12 hours at an increasing rate of 10°C /min under the protection of nitrogen atmosphere to produce porous carbon. Porous carbon is impregnated with a nickel nitrate solution for 12 hours, and is filtered and dried. Then, the mixture is heat-treated at 400°C for 6 hours at an increasing rate of 1°C /min under the protection of nitrogen atmosphere to produce porous carbon loaded NiO.

Example four

Bamboo is cleaned, dried and crushed to powder. The powder is then carbonized at 650°C for 3.5 hours at an increasing rate of 5°C /min under a vacuum condition. The obtained powder is mixed with KOH by a weight rate of 1 :3, and the mixture is activated by increasing temperature to 900 °C for 5 hours at an increasing rate of 5 °C /min under the protection of nitrogen atmosphere to produce porous carbon. Porous carbon is impregnated with a ferric acetate solution for 12 hours, and is filtered and dried. Then, the mixture is heat-treated at 300 °C for 6 hours at an increasing rate of 1 °C /min under the protection of nitrogen atmosphere to produce porous carbon loaded Fe₃0₄.

Example five

Cotton fibre is cleaned and dried. The fibre is then carbonized at 650°C for 4 hours at an increasing rate of 15 ^c/min under a vacuum condition. The obtained sample is mixed with KOH by a weight rate of 1 :5, and the mixture is activated by increasing temperature to 900 °C for 3 hours at an increasing rate of 15 °C /min under the protection of nitrogen atmosphere to produce porous carbon. Porous carbon is impregnated with a copper acetate solution for 12 hours, and is filtered and dried. Then, the mixture is heat-treated at 600°C for 1 hours at an increasing rate of 10°C /min under the protection of nitrogen atmosphere to produce porous carbon loaded CuO.

Such metal loaded porous carbons may have use in the area of environmental protection, water treatment, photocatalyst support and energy storage

The disclosure of Chinese patent application 201010204539.0

Chinese patent application 201010204539.0 uses porous carbon materials such as activated carbon and, as discussed above, treats them to promote in-situ growth of carbon nano structure material from the carbon of the carbon material, the in-situ grown material having a graphite- like structure.

Chinese patent application 201010204539.0 goes on to then generate and distribute nano metal oxide on the surface of carbon by ultrasonic reaction.

To solve the low specific capacitance of electric double layer capacitor and Faraday pseudo capacitor, and the low conductivity of electrode material, this aspect of the invention permits the use of porous activated carbon as a matrix, with in-situ grown nano carbon with graphite-like layer structure in the porous carbon, the use of ultrasonic chemical reaction to create nano metal oxide on the surface of the base carbon. This process distributes the produced metal oxide uniformly on the surface of the matrix carbon material uniformly by preventing metal oxide agglomeration via the local high temperature and high pressure produced by ultrasonic reaction: this improves the specific capacitance. The nano carbon with graphite-like layer structure significantly improves the material conductivity. The porous carbon [such as activated carbon] provides channels for the flow of metal oxide and electrolytes. A higher specific surface area and conductivity also gives the produced material a higher energy density and power density, making it suitable material for a supercapacitor. The relatively low cost of activated carbon and in particular biologically produced porous carbons makes the invention still more useful. Disclosed examples include :- Example 6

(1) The preparation of in-situ self growth nano carbon matrix material

a. Add activated carbon of 1.0- 10 g into the aqueous solution of 2.2- 100 ml water and 0.55 -10 g Fe(N03)3'9H₂0, mix uniformly and dry.

b. To put above dried mixture into sinter furnace for heat treatment: raise temperature to 450 °C, preserve for half hour, then raise temperature to 700-1000 °C, preserve for one hour, and then cool to room temperature naturally.

c. Put above material into the 10-15 % hydrochloric acid solution, 50 °C mix 5h, then filter, 80 °C dry, then the solid material is in-situ self growth nano carbon matrix material.

(2) Carbon matrix material surface treatment

To evenly distribute the metal oxide on the surface of carbon material, before the preparation of composite material, treat the surface of carbon matrix material by concentrated nitric acid, 80 °C reflex 3 hours, and then 80 °C dry. The resulting carbon matrix material has an oxidised/carboxylated surface.

(3) Make the metal oxide precursor

Make metal salt into an aqueous solution or alcohol solution, solution concentration is 0.01- 1 M, reserve after agitation.

(4) Put the 0.2g carbon matrix material of Step (2) into the precursor of Step (3), ultrasonic 1-6 hours, rinse, rinse gently, dry, under nitrogen protection, sinter 5h at 450 °C. Nano metal oxide / in-situ self growth nano carbon composite material is made.

(5) Mix the nano metal oxide / in-situ self growth nano carbon composite material of Step (4) with adhesive uniformly and coat on electrode, then the polarizing electrode for supercapacitor is made. Typical ultrasonic powers of 100-600 W, frequency of 20-60KHz, and duration of 1-6 hours are effective, but the invention in this aspect is not limited to these ranges.

Further specific examples include :-

Example 7

Add l .Og carbon into 2.2 ml water and 0.55 g Fe(N03)3'9H₂0, mix uniformly, dry and reserve.

Put above mixture into sintering furnace, in vacuum condition, raise temperature to 450 °C, preserve for half hour, raise temperature to 700 °C, preserve for one hour, and cool to room temperature naturally.

Put above material into 10-15% hydrochloric acid solution, at 50 °C, mix 5h, filter, dry at 80 °C, the produced solid material is in-situ self growth nano carbon matrix material.

Then, treat carbon matrix material surface by concentrated nitric acid, 80 °C reflux 3h, 80 °C dry, then carbon matrix material with carboxylation surface is made.

Prepare stannous chloride alcohol-water solvent (1.000 g SnCl₂, 10 ml alcohol, 20ml water), solution concentration is 0.1 M, agitation and reserve.

Put the produced carbon material into the produced SnCl₂ water solution, ultrasonic 6 hours, rinse gently, dry, under nitrogen protection, sinter at 450 °C 5 hours, nano Sn0₂/in-situ self growth nano carbon composite material is made.

The material made is measured by thermogravimetry to have tin oxide content 30%. By nitrogen adsorption test, the specific surface area is 190 m²/g. XRD shows Sn0₂, transmission electron microscope analysis (Fig. 1) shows nano tin oxide distributed evenly in carbon matrix, particle size is 3-5 nanometre. Electrochemical test shows 50mA/g initial discharge capacity to reach 760mAh/g, and maintain 335 niAh/g after 40 cycles.

Example 8 Add 5g carbon material into 50 ml water and 5 g Ρε(Ν03)3·9Η₂0, mix uniformly, dry and reserve.

Put above mixture into sintering furnace, in vacuum condition, raise temperature to 450 °C, preserve half hour, then raise temperature to 850 °C, preserve one hour, cool to room temperature naturally.

Put above material into 10-15% hydrochloric acid solution, at 50 °C, mix 5 hours, filter, 80 °C dry, the produced solid substance is in-situ self growth nano carbon matrix material.

Prepare stannous chloride alcohol- water solvent (5.000 g SnCl₂, 10 ml alcohol, 20ml water) solution concentration is 0.5 M, agitation and reserve. Add the produced carbon material into the produced SnCl₂ water solution, ultrasonic 3 hours, rinse gently, dry, under nitrogen protection, sinter at 450 °C for 5 h. The nano Sn0₂/in-situ self growth nano carbon composite material is made. TG test shows the material produced has tin oxide content of 35%. Nitrogen adsorption test shows specific surface area 165 m²/g. Electrochemical test shows 50mA/g initial discharge capacity to reach 770mAh/g, and maintain 310 niAh/g after 40 cycles.

Example 9

Add lOg carbon material into 100 ml water and 10 g Fe(N03)3^»9H₂0, mixing uniformly, dry and reserve.

Put above mixture into sintering furnace, in vacuum condition, raise temperature to 450 °C, preserve half hour, then raise temperature to 1000 °C, preserve one hour, cool to room temperature naturally.

Treat the carbon matrix material surface with concentrated nitric acid, 80 °C reflux 3h, 80 °C dry, then carbon matrix material with carboxylation surface is made.

Prepare stannous chloride alcohol-water solvent (10.000 g SnCl₂, 10 ml alcohol, 20ml water) solution concentration is 1 M, agitation and reserve. Add the produced carbon material into the produced SnCl₂ water solution, ultrasonic 1 hours, rinse gently, dry, under nitrogen protection, sinter at 450 °C for 5 h. The nano Sn0₂/in-situ self growth nano carbon composite material is made. TG test shows the material produced has tin oxide content of 40%. Nitrogen adsorption test shows specific surface area 90 m²/g. Electrochemical test shows 50mA/g initial discharge capacity to reach 800mAh/g, and maintain 305 niAh/g after 40 cycles

Example 10

Add l .Og carbon material into 50 ml water and 0.55 g Fe(N03)3^»9H₂0, mixing uniformly, dry and reserve.

Put above mixture into sintering furnace, in vacuum condition, raise temperature to 450 °C, preserve half hour, then raise temperature to 700 °C, preserve one hour, cool to room temperature naturally.

Put above material into 10-15% hydrochloric acid solution, at 50 °C, agitation 5 hours, filter, 80 °C dry, the produced solid substance is in-situ self growth nano carbon matrix material.

Prepare potassium permanganate aqueous solution concentration is 0.01 M, mix and reserve.

Add the produced carbon matrix material into the produced precursor, ultrasonic 6 hours, rinse gently, dry, under nitrogen protection, sinter at 450 °C for 5 h. The nano manganese oxide/in-situ self growth nano carbon composite material is made. TG test shows the material produced has manganese oxide content of 45%. Nitrogen adsorption test shows specific surface area 226 m²/g.

Example 11

Add 5.0g carbon material into 100 ml water and 5 g Fe(N0₃)3^»9H₂0, mix uniformly, dry and reserve.

Put above mixture into sintering furnace, in vacuum condition, raise temperature to 450 °C, preserve half hour, then raise temperature to 800 °C, preserve one hour, cool to room temperature naturally.

Put above material into 10-15% hydrochloric acid solution, at 50 °C, agitation 5 hours, filter, 80 °C dry, the produced solid substance is in-situ self growth nano carbon matrix material. Treat the carbon matrix material surface with concentrated nitric acid, 80 °C reflux 3h, 80 °C dry, then carbon matrix material with carboxylation surface is made.

Prepare aqueous potassium permanganate solution, solution concentration is 0.5 M, mix and reserve.

Add 0.2g of the produced carbon matrix material into the produced precursor, ultrasonic 3 hours, rinse gently, dry, under nitrogen protection, sinter at 450 °C for 5 h. The nano manganese oxide/in-situ self growth nano carbon composite material is made. TG test shows the material produced has manganese oxide content of 38%. Nitrogen adsorption test shows specific surface area 291 m²/g.

General applicability of nano structured carbon

In addition to the uses disclosed in Chinese patent applications 201010133489.1 and 201010204539.0; nano structured carbon materials, by virtue of their improved electrical conductivity over activated carbon will have a wide range of uses in electrical and electrochemical applications.

The use of biological precursors to make the activated carbon enables a wide range of microstructures to be achieved which too will provide advantage in a wide range of uses in electrical and electrochemical applications.

Claims

1. A method of making a nano-structured carbon material by:-

A) i) providing a porous carbon material having porosity; ii) impregnating a metallic material capable of catalyzing carbon nano structure growth within the porosity of the porous carbon material of step i) to provide an impregnated porous carbon material;

or,

and,

C) heating the impregnated porous carbon material to a

temperature sufficient to promote carbon nano structure growth within the porosity of the carbon material to provide a nano- structured carbon material.

2. A method as claimed in Claim 1 , in which the porous carbon material is

activated carbon.

3. A method as claimed in Claim 1, in which the porous carbon material is

produced by carbonising a biological precursor.

4. A method as claimed in any one of Claims 1 to 3, in which the heating step is to a temperature in the range between 300-1200°C, preferably 300-1000°C.

5. A method as claimed in any one of Claims 1 to 4, in which the carbon nano structures grown have a graphitic layer structure.

6. A method as claimed in any one of Claims 1 to 5, further comprising the step of treating the surface of the nano-structured carbon material.

7. A method as claimed in Claim 6, further comprising incorporating a metal oxide precursor into porosity of the nano-structured carbon material.

8. A method as claimed in Claim 7, in which the incorporation involves

ultrasonic agitation of the nano-structured carbon material in a solution of the metal oxide precursor.

9. A method as claimed in Claim 7 or Claim 8, in which the metal oxide

precursor comprises a precursor for one or more oxides of Ti, Zr, V, Sn, Cr, Co, Fe, Ni, Mn, or Ru.

10. A method as claimed in Claim 8 or Claim 9 as dependent on Claim 8, in which an ultrasonic power of 100-600 W, frequency of 20-60KHz, and duration of 1- 6 hours is used.

11. A nano structured carbon material comprising a porous carbon material having nano-structured carbon within the porosity and capable of being produced by the method of any preceding claim.

12. A method of making porous carbons comprising oxides within the porosity, the comprising the steps of:

• selecting a biomass material and carbonizing at a temperature of 400- 1000°C under vacuum or inert conditions

• activating the carbonized material via a appropriate physical or chemical activation process

• impregnating the resultant material with a precursor to one or more elements M and drying the resultant product

• calcining the resultant mixture under a vacuum or inert atmosphere to get porous carbon loaded with functional oxide M_xO_y, where M is one or more of Ti, Fe, Ni, Co, Zn, Cu, Mn, Zr, Cr,

Al, Sn, Y, Ce, La, Pb, Pd, Ru, Sr, In, Ga, Bi or Si, X is one of the 1,2 or 3, Y is one of 1,2,3 or 4.

13. A method as claimed in Claim 12 in which the activation step comprises

heating a porous carbon material impregnated with a metallic material to a temperature sufficient to promote carbon nano structure growth within the porosity of the carbon material to provide a nano-structured carbon material.

14. A method as claimed in any of Claims 1 to 10 or 12 to 13, in which the

metallic material comprises one or more salts of one or more transition metals.