Method for preparing highly nitrogen-doped mesoporous carbon composites

1. A method of preparing macroscopic composites made of a macroscopic support coated with a thin layer of highly nitrogen-doped mesoporous carbon phase, said method comprising:

(a) providing an aqueous solution of (i) (NH 4 ) 2 CO 3 ; (ii) a carbohydrate as carbon source, selected from aldose monosaccharides and glycosilated forms thereof, disaccharides and oligosaccharides or dextrine deriving from biomass conversion, and (iii) a carboxylic acid source selected from citric acid, and any other mono-, di-, tri-, and poly-carboxylic acid or their ammonium mono-, di-, tri- and poly-basic forms;

(b) providing a macroscopic support made of carbon-, silicon- or aluminum-based material, or binary mixtures thereof; wherein the macroscopic support is a single object or an assembly of smaller objects, wherein the overall dimension of the support ranges from 0.1 μm to 100 cm in three orthogonal directions;

optionally subjecting the maccroscopic support of step (b) to a passivation process comprising steps of:

(a1) providing an aqueous solution of citric acid and a carbohydrate as carbon source, selected from aldose monosaccharides and glycosilated forms thereof, disaccharides and oligosaccharides;

(b1) prior to step (c), immerging/soaking or impregnating the macroscopic support of step (b) in the aqueous solution of step (a1) for a suitable amount of time;

(c1) optionally removing the immerged macroscopic support from the aqueous solution of step (a1) if an excess aqueous solution is used in step (b1);

(d1) optionally subjecting the resulting macroscopic support to a gentle thermal treatment under air at low temperatures from 45 to 55° C.;

(e1) subjecting the resulting macroscopic support to a first thermal treatment under air at moderate temperatures from 110-150° C.±5° C.; and

(f1) subjecting the thermally treated macroscopic support to a second thermal treatment under inert atmosphere at higher temperatures from 600-800° C.±10° C.; thereby generating a macroscopic composite coated with a carbon layer;

(c) immerging/soaking or impregnating the macroscopic support of step (b), or the passivated macroscopic support obtained in step (f1) when a passivation process is used, in the aqueous solution of step (a) for a suitable amount of time;

(d) optionally removing the immerged macroscopic support from the aqueous solution of step (a) if an excess aqueous solution is used in step (c);

(e′) optionally subjecting the resulting macroscopic support to a gentle thermal treatment under air at low temperatures from 45 to 55° C.;

(e) subjecting the resulting macroscopic support to a first thermal treatment under air at moderate temperatures from 110-150° C.±5° C.;

(f) optionally subjecting the thermally treated macroscopic support to a second thermal treatment under air at higher temperatures:

from 400-500° C.±10° C., or

at 300° C.±10° C. for 2 to 4 hours;

thereby generating a macroscopic composite composed of a macroscopic support coated with a 20-200 nm thick layer of highly N-doped mesoporous carbonaceous material; wherein the N atom % in the mesoporous carbonaceous material is 25-40%; and

(g) optionally subjecting the macroscopic composite obtained in step (e) or (f) to a third thermal treatment by heating it to a temperature ranging between 600 to 900° C.±10° C. under inert atmosphere;

thereby generating a macroscopic composite composed of a macroscopic support coated with a 10-100 nm thick layer of highly N-doped mesoporous carbonaceous material; wherein the N atom % in the mesoporous carbonaceous material is 2-35%;

wherein the method comprises at least one of steps (f) or (g).

2. The method of claim 1 , wherein steps (c) through (f) are performed a first time and then repeated at least once prior to carrying out step (g).

3. The method of claim 1 , wherein in the aqueous solution of step (a), (NH 4 ) 2 CO 3 is present at a concentration ranging 1 to 8 mol/L; the carbohydrate carbon source is present at a concentration ranging from 1 to 5 mol/L; and the carboxylic acid source is present at a concentration ranging from 1 to 3 mol/L.

4. The method of claim 1 , wherein the macroscopic support is made of a material selected from β-SiC or α-SiC or SiC-based supports, either pure or doped with foreign elements including TiO 2 or SiO 2 , Al 2 O 3 , alumina, either pure or doped with foreign elements including TiO 2 or SiO 2 ; or carbon, each of which may be in the form of grains, flakes, rings, pellets, extrudates, beads or foam; or carbon nanotubes, carbon nanofibers, graphene or few-layer graphene.

5. The method of claim 1 , wherein the macroscopic support is made of silica (SiO 2 ), SiC, alumina (Al 2 O 3 ) or titania (TiO 2 ).

6. The method of claim 1 , wherein the macroscopic support is made of silica (SiO 2 ), alumina (Al 2 O 3 ) or titania (TiO 2 ), the method further comprising the passivation process.

7. The method of claim 1 , wherein the immerging/soaking or impregnating step (c) is carried out for 1 to 10 minutes.

8. The method of claim 1 , wherein the first thermal treatment step (e) is carried out for 1 to 10 hours.

9. The method of claim 1 , wherein the second thermal treatment step (f) is carried out for 1 to 10 hours.

10. The method of claim 1 , wherein the third thermal treatment step (g) is carried out for 1 to 10 hours.

11. The method of claim 1 , wherein the N-doped carbonaceous material layer:

has an N atom contents of 1-40%;

has an average pore size of 2-50 nm; and

has a thickness of 5 to 200±5 nm.