PROCESS FOR PRODUCING NANOFLAKES FROM G-C3N4/METAL COMPOSITE MATERIAL

Abstract

The present invention relates to a method for producing g-C.sub.3N.sub.4/metal composite nanoflakes comprising the following steps: (A) providing a starting material comprising or consisting of FePO.sub.4, urea and polyacrylnitrile, wherein the starting material is in the form of a powder having particles having an average particle size of less than 100 nm, (b) dispersing the starting material in a solvent, wherein the solvent is water, (c) removing the solvent to form a premix containing the starting material, (d) heating the premix and pyrolyzing the premix at a pyrolyzing temperature between 200 C. and 700 C., preferably between 400 C. and 600 C. to form a bulk g-C.sub.3N.sub.4 metal composite material, (e) treating the bulk g-C.sub.3N.sub.4 metal composite material with ultrasound to form g-C.sub.3N.sub.4 metal composite material nanoflakes.

Claims

1. A method for producing g-C.sub.3N.sub.4/metal composite material nanoflakes, the method comprising the following steps: a. providing a starting material comprising or consisting of an iron compound, a g-C.sub.3N.sub.4 precursor material and a polymer, i. wherein the iron compound is FePO.sub.4. ii. wherein the g-C.sub.3N.sub.4 precursor material is urea, and iii. wherein the polymer is polyacrylonitrile, wherein the starting material is in the form of powder with particles having an average particle size of less than 100 nm, b. dispersing the starting material in a solvent, wherein the solvent is water, c. removing the solvent to form a premix containing the starting material, d. heating the premix and pyrolyzing the premix at a pyrolysis temperature between 200 C. and 700 C., preferably between 400 C. and 600 C. to form a bulk g-C.sub.3N.sub.4/metal composite material. e. treating the bulk-g-C.sub.3N.sub.4/metal composite material with ultrasound to form g-C.sub.3N.sub.4/metal composite material nanoflakes.

2. The method according to claim 1, characterised in that the amount of the iron compound in step (a) is between 1.0 wt % and 20 wt % with respect to the total amount of the starting material.

3. The method according to claim 1, characterised in that dispersing in step (b) is carried out at a temperature between 80 C. and 100 C., preferably between 90 C. and 100 C., and optionally with ultrasound treatment.

4. The method according to claim 1, characterised in that the heating rate during heating to the pyrolysis temperature in step (d) is greater than or equal to 5 C./min.

5. The method according to claim 1, characterised in that the pyrolysis temperature in step (d) is approximately 450 C., or in that the pyrolysis temperature in step (d) is approximately 550 C.

6. The method according to claim 1, characterised in that the method comprises the following further step after step (d): reducing the iron in the g-C.sub.3N.sub.4/metal composite material.

7. The method according to claim 1, characterised in that in step (a) a further metal compound is added, wherein the further metal compound is selected from an aluminium, lithium, magnesium, titanium, nickel, platinum, palladium, vanadium compound or any mixture of these compounds.

8. The method according to claim 7, characterised in that the amount of the further metal compound in step (a) is between 0.5 wt % and 5.0 wt %, preferably approximately 1.0 wt %, with respect to the total amount of the starting material.

9. The method according to claim 1, characterised in that the pyrolysis in step (d) takes place in an inert gas atmosphere, in particular in a nitrogen atmosphere.

10. A g-C.sub.3N.sub.4/metal composite material in the form of nanoflakes obtainable by a method according to claim 1, wherein g-C.sub.3N.sub.4/nanoflakes are provided on the surface of which iron and/or the iron compound is carried, wherein the iron and/or the iron compound is in the particulate form with a particle diameter of less than 100 nm.

11. The composite material according to claim 10, comprising pores having an average pore size of less than 100 nm.

12. A hydrogen storage material comprising or consisting of g-C.sub.3N.sub.4/metal composite material according to claim 10.

13. An electrocatalyst for water electrolysis comprising or consisting of g-C.sub.3N.sub.4/metal composite material according to claim 10.

14. A photocatalyst for water electrolysis comprising or consisting of g-C.sub.3N.sub.4/metal composite material according to claim 10.

15. A photoelectrocatalyst for water electrolysis comprising or consisting of g-C.sub.3N.sub.4/metal composite material according to claim 10.

16. (canceled)

17. (canceled)

Description

[0059] In the figures:

[0060] FIG. 1 shows the hydrogen storage capacity of a g-C.sub.3N.sub.4/metal composite material according to a first embodiment;

[0061] FIG. 2 shows the hydrogen storage capacity of a g-C.sub.3N.sub.4/metal composite material according to a second embodiment; and

[0062] FIG. 3 shows the hydrogen storage capacity of a g-C.sub.3N.sub.4/metal composite material according to a third embodiment with voltage-assisted loading.

EMBODIMENT 1

[0063] The first embodiment shows the production of a g-C.sub.3N.sub.4/iron composite material, whereby a mixture of 2 wt % iron(III) phosphate, 95 wt % urea and 3 wt % polyacrylonitrile is used as the starting material. The components are mixed and ground in a ball mill for about 45 min at 600 rpm to form a starting material having an average particle size of less than 100 nm.

[0064] The resulting starting material is dispersed in as little water as possible using a disperser and an ultrasonic bath at a temperature of approximately 95 C.

[0065] When the dispersion is complete, the water is removed, and the remaining material is pyrolized in a N.sub.2 atmosphere at a pyrolysis temperature of approximately 550 C. for approximately 5 hours. Until the pyrolysis temperature is reached, the heating rate is approximately 5 C./min.

[0066] A layered bulk g-C.sub.3N.sub.4/composite material is obtained, wherein iron(III) oxide is included between the layers.

[0067] Then the produced bulk g-C.sub.3N.sub.4/composite material is exfoliated by ultrasound treatment to form g-C.sub.3N.sub.4/metal composite nanoflakes.

[0068] The compound can be used as a hydrogen storage material. At up to 25 bar, a hydrogen storage capacity of 9.2 wt % can be achieved at around 20 C. and a hydrogen storage capacity of 6.1 wt % at around 25 C. A substantially complete desorption takes place at approximately 80 C.

[0069] FIG. 1 shows the hydrogen storage capacity of the g-C.sub.3N.sub.4/metal composite material produced according to the first embodiment as a function of pressure and in comparison between approximately 20 C. (black circles) and approximately 25 C. (white circles).

EMBODIMENT 2

[0070] The second embodiment shows the production of a g-C.sub.3N.sub.4/iron-titanium composite material, wherein a mixture of 1% wt % iron(III) phosphate, 95 wt % urea and 3 wt % polyacrylonitrile with the further addition of 1 wt % titanium dioxide is used.

[0071] The further method steps are carried out in the same way as in the first embodiment.

[0072] Ti-doped g-C.sub.3N.sub.4/Fe composite nanoflakes are obtained, which can be used as hydrogen storage material. At up to 25 bar, a hydrogen storage capacity of 9.6 wt % can be achieved at around 20 C. and a hydrogen storage capacity of 6.3 wt % at around 25 C. A substantially complete desorption takes place at approximately 80 C.

[0073] FIG. 2 shows the hydrogen storage capacity of the g-C.sub.3N.sub.4/metal composite material produced according to the second embodiment as a function of pressure and in comparison between approximately 20 C. (black circles) and approximately 25 C. (white circles).

EMBODIMENT 3

[0074] The third embodiment shows the production of a g-C.sub.3N.sub.4/iron-titanium composite material, wherein a mixture of 3 wt % iron(III) phosphate, 90 wt % urea and 5 wt % polyacrylonitrile with the further addition of 1 wt % titanium dioxide is used as starting material. The components are mixed and ground in a ball mill for about 45 min at 600 rpm to form a starting material with an average particle size of less than 100 nm.

[0075] The resulting starting material is dispersed in as little water as possible using a disperser and an ultrasound bath at a temperature of approximately 95 C.

[0076] When the dispersion is complete, the water is removed, and the remaining material is pyrolized in a N.sub.2 atmosphere at a pyrolysis temperature of about 450 C. for about 5 hours. Until the pyrolysis temperature is reached, the heating rate is approx. 5 C./min.

[0077] A layered bulk g-C.sub.3N.sub.4/metal composite material is obtained, wherein iron(III) phosphate is included between the layers.

[0078] Then the produced bulk g-C.sub.3N.sub.4/composite material is exfoliated by ultrasonic treatment to form g-C.sub.3N.sub.4/metal composite nanoflakes.

[0079] The compound can be used as a hydrogen storage material. At up to 25 bar, a hydrogen storage capacity of 7.4 wt % can be achieved.

[0080] If the composite material is loaded under the additional influence of an electric field with a voltage of around 1400 V, a hydrogen storage capacity of 11.7 wt % can be achieved.

[0081] FIG. 3 shows the hydrogen storage capacity of the g-C.sub.3N.sub.4/metal composite material produced according to the third embodiment as a function of pressure, comparing the capacity without voltage-assisted loading (black circles) and with voltage-assisted loading (white circles).

EMBODIMENT 4

[0082] The g-C.sub.3N.sub.4/metal composite material with Ti and Fe produced according to the third embodiment canlike any other composite materials according to the inventionbe used as an electrophotocatalyst in the production of hydrogen and oxygen from water.

[0083] If a dispersion of the g-C.sub.3N.sub.4/metal composite material in water is irradiated using a UV/Vis source, a hydrogen production rate of around 35.3 mmol/(g*h) can be achieved. During the generation of hydrogen, an overvoltage of about 96 mV can be measured. The electrical current density is approximately 2.67 mA/cm.