KR101563346B1 - Method for preparing reduced graphene oxide-titanium dioxide photocatalyst composite and method for producing hydrogen peroxide as a solar fuel using the same - Google Patents

Abstract

Provided are a photocatalyst composite containing titanium dioxide (TiO_2) and reduced graphene oxide (rGO); or a photocatalyst composite additionally containing phosphate or cobalt phosphate (CoPi) with the photocatalyst; and a method for producing hydrogen peroxide as solar fuel using the same. The photocatalyst composite in accordance with the present invention: has excellent production efficiency of the hydrogen peroxide by the titanium dioxide carrying the reduced graphene oxide which is replaced for precious metals; increases the production efficiency of the hydrogen peroxide since a phosphate group inhibits degradation of the hydrogen peroxide generated as a protective substance on the surface of the titanium dioxide; and produces the hydrogen peroxide without an organic electron donor due to in-situ formation by the cobalt phosphate, thereby providing an economical method for producing hydrogen peroxide at low process cost.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method for producing a reduced graphene oxide-titanium dioxide photocatalytic composite, and a method for producing hydrogen peroxide as a solar fuel using the method. BACKGROUND ART [0002]

The present invention relates to a reduced graphene oxide-titanium dioxide photocatalyst composite and a process for preparing hydrogen peroxide using the same, and more particularly, to a photocatalytic composite having reduced graphene oxide And a method for producing hydrogen peroxide by irradiating light using the photocatalytic composite as a catalyst.

Hydrogen peroxide (H ₂ O ₂ ) is a reaction product produced by water and oxygen. It is an environmentally friendly oxidizer and widely used for organic synthesis, environmental purification, sterilization, and liquid propellant.

Hydrogen peroxide is generally prepared by a process involving the sequential reaction of oxidation of 2-ethly-9,10-dihydroxyanthracene and hydrogenation of 2-ethylanthraquinone. However, since this manufacturing process requires hydrogen gas, organic solvent and high energy, it is not only economical, but also an environmentally friendly method. In addition, although the production of hydrogen peroxide has been suggested as an alternative from the direct reaction between hydrogen and oxygen using a metal-based catalyst (Pd or Pd / Au alloy), the risk of explosion is still sporadic. Production of hydrogen peroxide using photocatalytic reaction is an environmentally friendly and future-oriented method because it requires only water, oxygen and light.

 Although hydrogen peroxide is frequently used as a co-oxidant in the titanium dioxide photocatalyst oxidation system, the hydrogen peroxide produced by the oxygen reduction reaction corresponding mainly to the rate-limiting step is not only slow in production but also decomposes at the same time as it is produced. You can not get a relatively large amount.

In the conventional titanium dioxide photocatalytic system, the production of hydrogen peroxide is carried out by (i) surface protection by fluorination, (ii) the support of gold nanoparticles (Au or Au / Ag alloy) as a promoter, (iii) ^{2 +} ), or (iv) use of benzyl alcohol as an electron donor. However, fluoride has strong toxicity, and the use of noble metals is not economical, so new technologies are needed to replace them.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a titanium dioxide-based photocatalyst system capable of replacing expensive noble metal cocatalyst with reduced graphene oxide, Titanium dioxide photocatalyst composite.

The second task of the present invention is to maximize the production rate of hydrogen peroxide by selectively modifying the surface of titanium dioxide with a phosphate by adding phosphate to the reduced graphene oxide-titanium dioxide photocatalytic composite to effectively prevent the decomposition of hydrogen peroxide generated by the photoreaction To provide a photocatalytic composite.

A third object of the present invention is to provide a reduced graphene oxide-titanium dioxide photocatalytic composite which is superior in efficiency of hydrogen peroxide production by introducing cobalt phosphate into a reduced graphene oxide-photocatalytic complex without an organic electron donor.

According to one aspect of the present invention, as technical means for achieving the above-mentioned technical object, titanium dioxide (TiO ₂ ); And a reduced Graphene Oxide (rGO).

The photocatalytic composite may further include a phosphate group.

The photocatalytic composite may further include cobalt phosphate (CoPi).

In the photocatalytic composite, the reduced graphene oxide may be supported on the surface of the titanium dioxide.

In the photocatalytic composite, the phosphate group may be supported on the surface of the titanium dioxide.

In the photocatalytic composite, the cobalt phosphate may be supported on the surface of the titanium dioxide.

According to another aspect of the present invention, there is provided a process for producing a photocatalyst composite comprising the steps of: (a) preparing a photocatalytic composite comprising titanium dioxide coated with reduced graphene oxide by contacting reduced graphene oxide with titanium dioxide; A method for producing a photocatalytic composite is provided.

Wherein the surface of the titanium dioxide carrying reduced graphene oxide is modified with phosphate (phosphate) to produce titanium dioxide carrying reduced graphene oxide and a phosphate group (phosphoric acid group) on the surface thereof (Step < RTI ID = 0.0 > b). ≪ / RTI >

The method for producing a photocatalytic composite according to the present invention comprises the steps of: (c) preparing a cobalt precursor by introducing a cobalt precursor into titanium dioxide carrying reduced graphene oxide and phosphate groups on its surface to produce titanium dioxide carrying reduced graphene oxide and cobalt phosphate on its surface; . ≪ / RTI >

The phosphate may be any one selected from the group consisting of NaH ₂ PO ₄ , Na ₂ HPO ₄ , Na ₃ HPO ₄ , KH ₂ PO ₄ , K ₂ HPO ₄ , and K ₃ PO ₄ .

The cobalt precursor may be cobalt perchlorate hexahydrate (Co (ClO ₄ ) ₂ .6H ₂ O).

The step (c) may be a step of dispersing the titanium dioxide supported on the surface of the reduced graphene oxide in a phosphate buffer solution and then adding a cobalt precursor solution to prepare titanium dioxide carrying reduced graphene oxide and cobalt phosphate on its surface have.

The step c may be carried out at a pH of 2.0 to 4.0.

According to another aspect of the present invention, there is provided a method for producing hydrogen peroxide comprising the step of preparing hydrogen peroxide by reacting water using the photocatalytic composite as a catalyst under light irradiation.

The light used in the light irradiation may be ultraviolet rays.

Therefore, the present invention can provide a photocatalytic composite which is superior in the production efficiency of hydrogen peroxide by replacing the noble metal and a method for producing the same.

In the photocatalytic composite of the present invention, instead of the noble metal, titanium dioxide carrying reduced graphene oxide enhances the production efficiency of hydrogen peroxide, the phosphoric acid group prevents the decomposition of hydrogen peroxide on the titanium dioxide surface to increase the production efficiency of hydrogen peroxide, There is an effect of producing hydrogen peroxide without an electron donor. Therefore, the photocatalytic composite of the present invention can provide an economical process for producing hydrogen peroxide having a low process cost.

1 is a view showing a hydrogen peroxide generation mechanism of the photocatalytic composite of the present invention.
FIG. 2 is a graph showing the concentration of hydrogen peroxide produced according to the titanium dioxide-borne material of Example 3 and Comparative Examples 1 to 4. FIG.
FIG. 3 is a graph showing the concentration of hydrogen peroxide produced according to the weight ratio of rGO supported on titanium dioxide in Examples 1 to 5 and Comparative Example 1. FIG.
4 is a graph showing the concentration of hydrogen peroxide produced by the presence or absence of a phosphate group in Example 2 and Comparative Examples 1, 5, and 7.
FIG. 5 is a graph showing the concentration of hydrogen peroxide produced according to the weight ratio of rGO supported on titanium dioxide in Examples 6 to 10 and Comparative Example 1 in the presence of phosphoric acid. FIG.
6 is a graph showing the ratio of the concentration of hydrogen peroxide present after decomposition by the photocatalysts in Test Examples 1 to 5 and Comparative Test Examples 1 to 5 against the initial hydrogen peroxide concentration.
Fig. 7 is a graph showing the concentration of hydrogen peroxide generated in the photocatalyst of Examples 11 to 14 measured. Fig.
FIG. 8 is a graph showing Raman spectra in the presence of rGO in Example 2 and Comparative Example 1. FIG.
FIG. 9 is a graph showing X-ray photoelectron spectroscopy (XPS) spectra in the presence of rGO in Example 7 and Comparative Example 5 in the presence of an organic electron donor.
10 is a graph showing an X-ray photoelectron spectroscopy (XPS) spectrum of Example 14 and Comparative Example 9 with or without rGO under the absence of an organic electron donor.
11 is an FE-SEM image, a TEM image, and an EELS mapping photograph of Example 14. Fig.

Hereinafter, the photocatalytic composite of the present invention and the production method thereof will be described.

1, the photocatalytic composite of the present invention comprises titanium dioxide (TiO ₂ ); And reduced Graphene Oxide (rGO), and may further include a phosphate group or cobalt phosphate (CoPi).

The reduced graphene oxide may be supported on the surface of the titanium dioxide.

In the photocatalytic composite, the content of the reduced graphene oxide may be 1 to 20 parts by weight, preferably 1 to 10 parts by weight, based on 100 parts by weight of titanium dioxide.

The phosphate group (phosphate group, PO ₄ ^3- ) can selectively bind to the titanium dioxide surface.

The cobalt phosphate may be supported on the titanium dioxide surface.

The content of the cobalt phosphate in the photocatalytic composite may be 1 part by weight or more, preferably 0.1 to 10 parts by weight based on 100 parts by weight of the titanium dioxide.

Hereinafter, a method for producing the photocatalytic composite will be described.

Reduced graphene oxide  On the surface Bearing  The step of producing titanium dioxide (step a)

According to the present invention, a photocatalytic composite comprising titanium dioxide in which reduced graphene oxide is supported on a surface by contacting reduced graphene oxide with titanium dioxide can be prepared (step a).

The reduced graphene oxide-supported titanium dioxide can be produced at 150 to 300 ° C. Preferably at 150 to < RTI ID = 0.0 > 300 C < / RTI >

Reduction with graphene oxide The phosphate group (phosphoric acid group)  On the surface Bearing  The step of producing titanium dioxide (step b)

The surface of the titanium dioxide carrying the reducing graphene oxide on the surface thereof is modified with phosphate (phosphate) to prepare titanium dioxide carrying the reduced graphene oxide and the phosphate group (phosphoric acid group) on the surface (step b) .

The titanium dioxide on which the reduced graphene oxide is supported can be added to a phosphate buffer solution, preferably a potassium phosphate buffer solution, to selectively substitute the hydroxyl group of the titanium dioxide surface with the phosphate group. The phosphate buffer solution preferably has a pH of 2.0 to 4.0 and a concentration of 0.05 to 0.2 M.

As the phosphate (phosphate) may be used to _{NaH 2 PO 4, Na 2 HPO} 4, Na 3 HPO 4, KH 2 PO 4, K 2 HPO 4, or K ₃ PO _4.

Reduction with graphene oxide Cobalt phosphate  On the surface Bearing  Producing titanium dioxide (step c);

The cobalt precursor may be contacted with the titanium dioxide carrying the reducing graphene oxide and the phosphate group on the surface to prepare titanium dioxide carrying reduced graphene oxide and cobalt phosphate on the surface thereof (step c).

Titanium dioxide supported on the surface of the reduced graphene oxide is dispersed in a phosphate buffer solution and then a cobalt precursor solution is added to prepare titanium dioxide carrying reduced graphene oxide and cobalt phosphate on its surface.

Cobalt perchlorate hexahydrate (Co (ClO ₄ ) ₂ .6H ₂ O) may be used as the cobalt precursor.

Preferably may be in the potassium phosphate solution and a cobalt solution is an aqueous solution, wherein the potassium phosphate solution Potassium phosphate monobasic (Aldrich, 99.99% ) with 1M potassium phosphate buffer solution containing a phosphoric acid group (PO ₄ ^3-) and phosphoric acid ( Aldrich, ≥ 85 wt% in H ₂ O, ≥99.999% trace metal basis. The cobalt solution is a cobalt solution containing cobalt ions (Co ²⁺ ). In 20 ml of purified water, cobalt perchlorate hexahydrate (Aldrich).

The step c may be carried out at a pH of 2.0 to 4.0. The pH of step b may be finally adjusted using HClO ₄ .

The manufacturing method of the photocatalytic composite may further include a step of producing reduced graphene oxide.

The reduced graphene oxide may be prepared at 50 to 150 < 0 > C.

The present invention can provide a method for producing hydrogen peroxide by using the photocatalytic composite as a catalyst and reacting water under light irradiation to produce hydrogen peroxide.

The light used in the light irradiation may be ultraviolet light, preferably light having a wavelength of 300 to 400 nm.

The photocatalytic composite can be used for the production of hydrogen peroxide without an organic electron donor.

[Example]

Hereinafter, preferred embodiments of the present invention will be described. However, this is for illustrative purposes only, and thus the scope of the present invention is not limited thereto.

Reduced graphene oxide  Produce

Graphene oxide was prepared from natural graphite (SP-1 grade 200 mesh, Bay Carbon Inc.) using the modified Hummers method. The graphite oxide was peeled off with single layer graphene oxide (GO) by ultrasonication (JAC 4020, 400 W, Sonic) for 1 hour in water (200 ml) Lt; / RTI > To reduce the GO, 0.4 ml of ammonia solution (Samchun chemicals, 28-30%) and 10 ul of hydrazine hydrate per mg of GO were added to the GO-dispersed solution. The solution was heated to 95 ° C using a reflux condenser, and a reduced graphene oxide was prepared by stirring a glass-coated stirring magnet to keep the reduced graphene oxide (rGO) itself from agglomeration and holding it for 2 hours while stirring slowly.

Example  One : Reduced graphene oxide / Titanium oxide ( rGO / TiO ₂ (One wt %)) And H ₂ O ₂ Manufacturing

After reducing 200 ml of the reduced graphene oxide solution (containing 5 mg of rGO) to room temperature, 0.495 g of titanium dioxide powder (P25, Degussa) was added. To disperse the titanium dioxide powder, the solution was sonicated in an ultrasonic bath, and then 10 ml of 1M hydrochloric acid was added during high-speed stirring. The precipitated rGO / TiO ₂ complex was washed to neutral pH, dried at room temperature and treated at 200 ° C. under an argon gas flow to obtain a reduced graphene oxide / titanium oxide (rGO / TiO ₂₎ with an rGO content of 1 wt% (1 wt%)) photocatalytic composite.

20 mg of the prepared rGO / TiO ₂ (1 wt%) was dispersed in a solution prepared by mixing 2 ml of 2-propanol and 38 ml of purified water, and the pH was finally adjusted to pH 3.0 using HClO ₄ .

Using a 300-W Xe arc lamp (Oriel) as a light source, the reactor was irradiated with light through an IR filter and a cutoff filter (?? 320 nm) while continuously stirring the reactor. H ₂ O ₂ was prepared by purging continuously while bubbling O ₂ during light irradiation.

Example  2 : rGO / TiO ₂ (6 wt %) And H ₂ O ₂ Manufacturing

rGO solution 200ml (rGO containing 5mg) was used instead of 200ml rGO solution was added 0.470g TiO ₂ powder and the manufacture photocatalyst composite rGO / TiO ₂ (1wt%) to the (containing rGO 30mg) instead of addition of the TiO ₂ powder, 0.495g on to and it is carried out as example 1 except for using rGO / TiO ₂ (6wt%) was prepared rGO / TiO ₂ (6wt%) photocatalytic composites and H ₂ O _2.

Example  3: rGO / TiO ₂ (10 wt %) And H ₂ O ₂ Manufacturing

rGO solution 200ml (rGO containing 5mg) was used instead of 200ml rGO solution was added 0.450g TiO ₂ powder and the manufacture photocatalyst composite rGO / TiO ₂ (1wt%) to the (containing rGO 50mg) instead of addition of the TiO ₂ powder, 0.495g on to and it is carried out as example 1 except for using rGO / TiO ₂ (10wt%) was prepared rGO / TiO ₂ (10wt%) photocatalytic composites and H ₂ O _2.

Example  4 : rGO / TiO ₂ (20 wt %) And H ₂ O ₂ Manufacturing

rGO solution 200ml (rGO containing 5mg) was used instead of 200ml rGO solution was added 0.400g TiO ₂ powder and the manufacture photocatalyst composite rGO / TiO ₂ (1wt%) to the (containing rGO 100mg) in place of the addition of the TiO ₂ powder, 0.495g on to and it is carried out as example 1 except for using rGO / TiO ₂ (20wt%) was prepared rGO / TiO ₂ (20wt%) photocatalytic composites and H ₂ O _2.

Example  5: rGO / TiO ₂ (40 wt %) And H ₂ O ₂ Manufacturing

rGO solution 200ml (rGO containing 5mg) was used instead of 200ml rGO solution was added 0.300g TiO ₂ powder and the manufacture photocatalyst composite rGO / TiO ₂ (1wt%) to the (containing rGO 200mg) in place of the addition of the TiO ₂ powder, 0.495g on to and it is carried out as example 1 except for using rGO / TiO ₂ (40wt%) was prepared rGO / TiO ₂ (40wt%) photocatalytic composites and H ₂ O _2.

Example  6: rGO / TiO ₂ / P (1 wt %) And H ₂ O ₂ Manufacturing

After reducing 200 ml of the reduced graphene oxide solution (containing 5 mg of rGO) to room temperature, 0.495 g of titanium dioxide powder (P25, Degussa) was added. To disperse the titanium dioxide powder, the solution was sonicated in an ultrasonic bath, and then 10 ml of 1M hydrochloric acid was added during high-speed stirring. The precipitated rGO / TiO ₂ complex was washed to neutral pH, dried at room temperature and treated at 200 ° C under an argon gas flow to produce rGO / TiO ₂ (1 wt%).

20 mg of the prepared rGO / TiO ₂ (1 wt%) was dispersed in a solution prepared by mixing 4 ml of 1 M potassium phosphate buffer solution and 34 ml of purified water, and 2 ml of 2-propanol (Aldrich) was added to the dispersion solution. The pH of the solution was finally adjusted to pH 3.0 using HClO ₄ to prepare rGO / TiO ₂ / P (1 wt%).

The reactor was irradiated to the reactor with a 300-W Xe arc lamp (Oriel) as a light source while continuously stirring and passing light through an IR filter and a cutoff filter (? During the irradiation of light, O ₂ was continuously purged while bubbling to produce hydrogen peroxide.

Example  7: rGO / TiO ₂ / P (6 wt %) And H ₂ O ₂ Manufacturing

rGO solution 200ml (rGO containing 5mg) was used instead of 200ml rGO solution was added 0.470g TiO ₂ powder and the manufacture photocatalyst composite rGO / TiO ₂ (1wt%) to the (containing rGO 30mg) instead of addition of the TiO ₂ powder, 0.495g TiO ₂ / P (6 wt%) photocatalytic composite and H ₂ O ₂ were prepared in the same manner as in Example 6, except that rGO / TiO ₂ (6 wt%) was used.

Example  8 : rGO / TiO ₂ / P (10 wt %) And H ₂ O ₂ Manufacturing

rGO solution 200ml (rGO containing 5mg) was used instead of 200ml rGO solution was added 0.450g TiO ₂ powder and the manufacture photocatalyst composite rGO / TiO ₂ (1wt%) to the (containing rGO 50mg) instead of addition of the TiO ₂ powder, 0.495g RGO / TiO ₂ / P (10 wt%) photocatalytic composite and H ₂ O ₂ were prepared in the same manner as in Example 6, except that rGO / TiO ₂ (10 wt%) was used.

Example  9: rGO / TiO ₂ / P (20 wt %) And H ₂ O ₂ Manufacturing

rGO solution 200ml (rGO containing 5mg) was used instead of 200ml rGO solution was added 0.400g TiO ₂ powder and the manufacture photocatalyst composite rGO / TiO ₂ (1wt%) to the (containing rGO 100mg) in place of the addition of the TiO ₂ powder, 0.495g TiO ₂ / P (20 wt%) photocatalytic composite and H ₂ O ₂ were prepared in the same manner as in Example 6, except that rGO / TiO ₂ (20 wt%) was used.

Example  10: rGO / TiO ₂ / P (40 wt %) And H ₂ O ₂ Manufacturing

rGO solution 200ml (rGO containing 5mg) was used instead of 200ml rGO solution was added 0.300g TiO ₂ powder and the manufacture photocatalyst composite rGO / TiO ₂ (1wt%) to the (containing rGO 200mg) in place of the addition of the TiO ₂ powder, 0.495g RGO / TiO ₂ / P (40 wt%) photocatalytic composite and H ₂ O ₂ were prepared in the same manner as in Example 6, except that rGO / TiO ₂ (40 wt%) was used.

Example  11: rGO / TiO ₂ (6 wt %) H ₂ O ₂  Manufacturing (no organic electron donor)

After reducing 200 ml of reduced graphene oxide solution (containing 30 mg of rGO) to room temperature, 0.470 g of titanium dioxide powder (P25, Degussa) was added. To disperse the titanium dioxide powder, the solution was sonicated in an ultrasonic bath, and then 10 ml of 1M hydrochloric acid was added during high-speed stirring. The precipitated rGO / TiO ₂ complex was washed to neutral pH, dried at room temperature and treated at 200 ° C under an argon gas flow to produce a rGO / TiO ₂ (6 wt%) photocatalytic complex.

20 mg of the prepared rGO / TiO ₂ (6 wt%) was dispersed in a solution prepared by mixing with 40 ml of purified water. The pH of the solution was finally adjusted to pH 3.0 using HClO ₄ to prepare an organic donor-free rGO / TiO ₂ (6 wt%).

The reactor was irradiated to the reactor with a 300-W Xe arc lamp (Oriel) as a light source while continuously stirring and passing light through an IR filter and a cutoff filter (? During the irradiation of light, O ₂ was continuously purged while bubbling to produce hydrogen peroxide.

Example  12: rGO / TiO ₂ / P (6 wt %) And H ₂ O ₂ (Without organic electron donor)

After reducing 200 ml of reduced graphene oxide solution (containing 30 mg of rGO) to room temperature, 0.470 g of titanium dioxide powder (P25, Degussa) was added. To disperse the titanium dioxide powder, the solution was sonicated in an ultrasonic bath, and then 10 ml of 1M hydrochloric acid was added during high-speed stirring. The precipitated rGO / TiO ₂ complex was washed to neutral pH, dried at room temperature and treated at 200 ° C under an argon gas flow to produce rGO / TiO ₂ (6 wt%).

20 mg of the prepared rGO / TiO ₂ (6 wt%) was dispersed in a solution prepared by mixing 4 ml of 1 M potassium phosphate buffer solution and 36 ml of purified water. The pH of the solution was finally adjusted to pH 3.0 using HClO ₄ to prepare rGO / TiO ₂ / P (6 wt%) free of organic electron donors.

The reactor was irradiated to the reactor with a 300-W Xe arc lamp (Oriel) as a light source while continuously stirring and passing light through an IR filter and a cutoff filter (? During the irradiation of light, O ₂ was continuously purged while bubbling to produce hydrogen peroxide.

Example  13: rGO / TiO ₂ / Co (6 wt %) And H ₂ O ₂ (Without organic electron donor)

After reducing 200 ml of reduced graphene oxide solution (containing 30 mg of rGO) to room temperature, 0.470 g of titanium dioxide powder (P25, Degussa) was added. To disperse the titanium dioxide powder, the solution was sonicated in an ultrasonic bath, and then 10 ml of 1M hydrochloric acid was added during high-speed stirring. The precipitated rGO / TiO ₂ The complex was washed to neutral pH, dried at room temperature and treated at 200 ° C under an argon gas flow to produce a rGO / TiO ₂ (6 wt%) photocatalytic complex.

20 mg of the prepared rGO / TiO ₂ (6 wt%) was dispersed in a solution prepared by mixing 40 ml of purified water, and 0.124 ml of a cobalt solution prepared from 0.2 g of cobalt perchlorate hexahydrate (Aldrich) as a cobalt precursor in 20 ml of purified water was added to the dispersion After the addition, the pH was finally adjusted to pH 3.0 using HClO ₄ to prepare rGO / TiO ₂ / Co (6 wt%) free of organic electron donors.

The reactor was irradiated to the reactor with a 300-W Xe arc lamp (Oriel) as a light source while continuously stirring and passing light through an IR filter and a cutoff filter (? During the irradiation of light, O ₂ was continuously purged while bubbling to produce hydrogen peroxide.

Example  14: rGO / TiO ₂ / CoPi (6 wt %) And H ₂ O ₂ (Without organic electron donor)

After reducing 200 ml of reduced graphene oxide solution (containing 30 mg of rGO) to room temperature, 0.470 g of titanium dioxide powder (P25, Degussa) was added. To disperse the titanium dioxide powder, the solution was sonicated in an ultrasonic bath, and then 10 ml of 1M hydrochloric acid was added during high-speed stirring. The precipitated rGO / TiO ₂ complex was washed to neutral pH, dried at room temperature and treated at 200 ° C under an argon gas flow to produce rGO / TiO ₂ (6 wt%).

20 mg of the prepared rGO / TiO ₂ (6 wt%) was dispersed in a solution prepared by mixing 4 ml of 1 M potassium phosphate buffer and 36 ml of purified water, and 20 ml of purified water was added with cobalt perchlorate hexahydrate (Aldrich) 0.124 ml of the solution was added to the dispersion solution, and the pH was finally adjusted to pH 3.0 using HClO ₄ to prepare rGO / TiO ₂ / CoPi (6 wt%) containing no organic electron donor.

The reactor was irradiated to the reactor with a 300-W Xe arc lamp (Oriel) as a light source while continuously stirring and passing light through an IR filter and a cutoff filter (? During the irradiation of light, O ₂ was continuously purged while bubbling to produce hydrogen peroxide.

Comparative Example  One: TiO ₂ Using H ₂ O ₂  Produce

20 mg of TiO ₂ was dispersed in a solution prepared by mixing 2 ml of 2-propanol with 38 ml of purified water, and the pH was finally adjusted to pH 3.0 using HClO ₄ .

Using a 300-W Xe arc lamp (Oriel) as a light source, the reactor was irradiated with light through an IR filter and a cutoff filter (?? 320 nm) while continuously stirring the reactor. H ₂ O ₂ was prepared by purging continuously while bubbling O ₂ during light irradiation.

Comparative Example  2: Ag / TiO ₂ (One wt %) H ₂ O ₂  Produce

Ag of the light on the TiO ₂ - TiO ₂ is deposited under UV irradiation for 30 minutes using a 200W mercury lamp , Ag / TiO ₂ (1 wt%) was obtained in an aqueous solution containing 0.25 g of distilled water, 480 ml of distilled water, 20 ml of methanol as electron donor and 3.9 mg of silver precursor (AgNO ₃ ).

20 mg of Ag / TiO ₂ (1 wt%) was dispersed in a solution prepared by mixing 2 ml of 2-propanol and 38 ml of purified water, and the pH was finally adjusted to pH 3.0 using HClO ₄ .

Using a 300-W Xe arc lamp (Oriel) as a light source, the reactor was irradiated with light through an IR filter and a cutoff filter (?? 320 nm) while continuously stirring the reactor. H ₂ O ₂ was prepared by purging continuously while bubbling O ₂ during light irradiation.

Comparative Example  3: Au / TiO ₂ (One wt %) H ₂ O ₂  Produce

Au / TiO ₂ (1 wt%) and H ₂ O ₂ were prepared in the same manner as in Comparative Example 2, except that 4.3 mg of HAuCl ₄ was used instead of 3.9 mg of AgNO ₃ .

Comparative Example  4: Pt / TiO ₂ (One wt %) H ₂ O ₂  Produce

Pt / TiO ₂ (1 wt%) and H ₂ O ₂ were prepared in the same manner as in Comparative Example 2, except that 5.3 mg of H ₂ PtCl ₆ was used instead of 3.9 mg of AgNO ₃ .

Comparative Example  5: TiO ₂ / P and H ₂ O ₂ Manufacturing

20 mg of TiO ₂ was dispersed in a solution prepared by mixing 4 ml of 1 M potassium phosphate buffer solution, 2 ml of 2-propanol and 34 ml of purified water. The pH of the solution was finally adjusted to pH 3.0 using HClO ₄ to prepare TiO ₂ / P.

The reactor was irradiated to the reactor with a 300-W Xe arc lamp (Oriel) as a light source while continuously stirring and passing light through an IR filter and a cutoff filter (? During the irradiation of light, O ₂ was continuously purged while bubbling to produce hydrogen peroxide.

Comparative Example  6: Ag / TiO ₂ / P (1 wt %) And H ₂ O ₂ Manufacturing

Light of Ag on TiO ₂ - deposition using a 200W mercury lamp for 30 minutes under UV irradiation TiO ₂ 0.25g, 480ml distilled water, and 20ml of methanol as the electron donor is performed in an aqueous solution containing the precursor (AgNO ₃₎ 3.9mg To obtain Ag / TiO ₂ (1 wt%).

20 mg of Ag / TiO ₂ (1 wt%) was dispersed in a solution prepared by mixing 4 ml of 1 M potassium phosphate buffer solution, 2 ml of 2-propanol and 34 ml of purified water. The pH of the solution was finally adjusted to pH 3.0 using HClO ₄ to prepare Ag / TiO ₂ / P (1 wt%).

The reactor was irradiated to the reactor with a 300-W Xe arc lamp (Oriel) as a light source while continuously stirring and passing light through an IR filter and a cutoff filter (? During the irradiation of light, O ₂ was continuously purged while bubbling to produce hydrogen peroxide.

Comparative Example  7: Au / TiO ₂ / P (1 wt %) And H ₂ O ₂ Manufacturing

AgNO ₃ HAuCl ₄ Au / TiO ₂ / P (1 wt%) and H ₂ O ₂ were prepared in the same manner as in Comparative Example 6,

Comparative Example  8: Pt / TiO ₂ / P (1 wt %) H ₂ O ₂  Produce

Pt / TiO ₂ / P (1 wt%) and H ₂ O ₂ were prepared in the same manner as in Comparative Example 6, except that 5.3 mg of H ₂ PtCl ₆ was used instead of 3.9 mg of AgNO ₃ .

Comparative Example  9: TiO ₂ / CoPi  And H ₂ O ₂ (Without organic electron donor)

20 mg of TiO ₂ was dispersed in a solution prepared by mixing 4 ml of 1 M potassium phosphate buffer and 36 ml of purified water and 0.124 ml of a cobalt solution prepared by dissolving 0.2 g of cobalt perchlorate hexahydrate (Aldrich) as a cobalt precursor in 20 ml of purified water was added to the dispersion solution Then, the pH was finally adjusted to pH 3.0 using HClO ₄ to prepare TiO ₂ / CoPi free of organic electron donors.

The reactor was irradiated to the reactor with a 300-W Xe arc lamp (Oriel) as a light source while continuously stirring and passing light through an IR filter and a cutoff filter (? During the irradiation of light, O ₂ was continuously purged while bubbling to produce hydrogen peroxide.

H ₂ O ₂ Decomposition test of

Test Example  One : rGO / TiO ₂ (6 wt %)On by H ₂ O ₂ Decomposition of

After reducing 200 ml of reduced graphene oxide solution (containing 30 mg of rGO) to room temperature, 0.470 g of titanium dioxide powder (P25, Degussa) was added. To disperse the titanium dioxide powder, the solution was sonicated in an ultrasonic bath, and then 10 ml of 1M hydrochloric acid was added during high-speed stirring. The precipitated rGO / TiO ₂ complex was washed to neutral pH, dried at room temperature and treated at 200 ° C under an argon gas flow to produce a rGO / TiO ₂ (6 wt%) photocatalytic complex.

20 mg of the prepared rGO / TiO ₂ (6 wt%) was dispersed in a solution prepared by mixing 4 ml of 50 mM hydrogen peroxide and 36 ml of purified water, and the pH of the solution was finally adjusted to pH 3.0 using HClO ₄ .

The reactor was irradiated to the reactor with a 300-W Xe arc lamp (Oriel) as a light source while continuously stirring and passing light through an IR filter and a cutoff filter (? During the irradiation of light, O ₂ was continuously purged while bubbling to decompose the hydrogen peroxide.

Test Example  2: rGO / TiO ₂ / P (6 wt %)On by H ₂ O ₂ Decomposition of

After reducing 200 ml of reduced graphene oxide solution (containing 30 mg of rGO) to room temperature, 0.470 g of titanium dioxide powder (P25, Degussa) was added. To disperse the titanium dioxide powder, the solution was sonicated in an ultrasonic bath, and then 10 ml of 1M hydrochloric acid was added during high-speed stirring. The precipitated rGO / TiO ₂ complex was washed to neutral pH, dried at room temperature and treated at 200 ° C under an argon gas flow to produce a rGO / TiO ₂ (6 wt%) photocatalytic complex.

20 mg of the prepared rGO / TiO ₂ (6 wt%) was dispersed in a solution prepared by mixing 4 ml of 1 M potassium phosphate buffer solution, 4 ml of 50 mM hydrogen peroxide and 32 ml of purified water. The pH of the solution was finally adjusted to pH 3.0 using HClO ₄ To prepare rGO / TiO ₂ / P (6 wt%).

The reactor was irradiated to the reactor with a 300-W Xe arc lamp (Oriel) as a light source while continuously stirring and passing light through an IR filter and a cutoff filter (? During the irradiation of light, O ₂ was continuously purged while bubbling to decompose the hydrogen peroxide.

Comparative test example  One : TiO ₂ On by H ₂ O ₂ Decomposition of

20 mg of TiO ₂ was dispersed in a solution prepared by mixing 4 ml of 50 mM hydrogen peroxide and 36 ml of purified water, and the pH of the solution was finally adjusted to pH 3.0 using HClO ₄ .

The reactor was irradiated to the reactor with a 300-W Xe arc lamp (Oriel) as a light source while continuously stirring and passing light through an IR filter and a cutoff filter (? During the irradiation of light, O ₂ was continuously purged while bubbling to decompose the hydrogen peroxide.

Comparative test example  2 : Ag / TiO ₂ (One wt %)On by H ₂ O ₂ Decomposition of

Light of Ag on TiO ₂ - deposition using a 200W mercury lamp for 30 minutes under UV irradiation TiO ₂ 0.25g, 480ml distilled water, and 20ml of methanol as the electron donor is performed in an aqueous solution containing the precursor (AgNO ₃₎ 3.9mg To obtain Ag / TiO ₂ (1 wt%).

20 mg of Ag / TiO ₂ (1 wt%) was dispersed in a solution prepared by mixing 4 ml of 50 mM hydrogen peroxide and 36 ml of purified water, and the pH of the solution was finally adjusted to pH 3.0 using HClO ₄ .

The reactor was irradiated to the reactor with a 300-W Xe arc lamp (Oriel) as a light source while continuously stirring and passing light through an IR filter and a cutoff filter (? During the irradiation of light, O ₂ was continuously purged while bubbling to decompose the hydrogen peroxide.

Comparative test example  3: Au / TiO ₂ (One wt %)On by H ₂ O ₂ Decomposition of

Hydrogen peroxide was decomposed in the same manner as in Comparative Test Example 2 except that 4.3 mg of HAuCl ₄ was used instead of 3.9 mg of AgNO ₃ .

Comparative test example  4 : Pt / TiO ₂ (One wt %)On by H ₂ O ₂ Decomposition of

Hydrogen peroxide was decomposed in the same manner as in Comparative Test Example 2 except that 5.3 mg of H ₂ PtCl ₆ was used instead of 3.9 mg of AgNO ₃ .

compare Test Example  5: TiO ₂ By / P H ₂ O ₂ Decomposition of

20 mg of TiO ₂ was dispersed in a solution prepared by mixing 4 ml of 1 M potassium phosphate buffer solution, 4 ml of 50 mM hydrogen peroxide and 32 ml of purified water, and the pH of the solution was finally adjusted to pH 3.0 with HClO ₄ to prepare TiO ₂ / P .

The reactor was irradiated to the reactor with a 300-W Xe arc lamp (Oriel) as a light source while continuously stirring and passing light through an IR filter and a cutoff filter (? During the irradiation of light, O ₂ was continuously purged while bubbling to decompose the hydrogen peroxide.

compare Test Example  6: Ag / TiO ₂ / P (1 wt %)On by H ₂ O ₂ Decomposition of

Light of Ag on TiO ₂ - deposition using a 200W mercury lamp for 30 minutes under UV irradiation TiO ₂ 0.25g, 480ml distilled water, and 20ml of methanol as the electron donor is performed in an aqueous solution containing the precursor (AgNO ₃₎ 3.9mg To obtain Ag / TiO ₂ (1 wt%).

20 mg of Ag / TiO ₂ (1 wt%) was dispersed in a solution prepared by mixing 4 ml of 1 M potassium phosphate buffer solution, 4 ml of 50 mM hydrogen peroxide, and 32 ml of purified water. The pH of the solution was adjusted to pH 3.0 finally using HClO ₄ Ag / TiO ₂ / P (1 wt%).

The reactor was irradiated to the reactor with a 300-W Xe arc lamp (Oriel) as a light source while continuously stirring and passing light through an IR filter and a cutoff filter (? During the irradiation of light, O ₂ was continuously purged while bubbling to decompose the hydrogen peroxide.

Comparative test example  7: Au / TiO ₂ / P (1 wt %)On by H ₂ O ₂ Decomposition of

Preparation of Au / TiO ₂ / P (1 wt%) and decomposition of hydrogen peroxide were carried out in the same manner as in Comparative Test Example 6, except that 4.3 mg of HAuCl ₄ was used instead of 3.9 mg of AgNO ₃ .

Comparative test example  8 : Pt / TiO ₂ / P (1 wt %)On by H ₂ O ₂ Decomposition of

Pt / TiO ₂ / P (1 wt%) was prepared and hydrogen peroxide was decomposed in the same manner as in Comparative Test Example 6, except that 5.3 mg of H ₂ PtCl ₆ was used instead of 3.9 mg of AgNO ₃ .

DPD  Measurement of concentration of hydrogen peroxide using method

The concentration of hydrogen peroxide was measured using the DPD method. During the light irradiation, 1 mL of sample aliquot was collected with a syringe and filtered with 0.45 um PTFE filter (Millipore). Depending on the concentration of hydrogen peroxide produced, different amounts of the sample were added so as not to exceed the detection limit of the DPD method. A solution of N, N-Diethyl-1,4-Phenylene-Diamine sulfate (DPD, 97%, Aldrich), peroxidase (POD, horseradish, Aldrich) and sodium phosphate buffer was prepared as follows. 0.1 g of DPD was dissolved in 10 ml of 0.1 N H ₂ SO ₄ and 5 mg of POD was dissolved in 5 ml of purified water. POD solution was used once every 5 days.

The sodium phosphate buffer solution was prepared by mixing 99.7 ml of purified water, 87.7 ml of 1 M monobasic sodium phosphate solution, and 12.6 ml of 1 M dibasic sodium phosphate heptahydrate solution. 0.4 ml of phosphoric acid buffer, 1.12 ml of water, 1 ml of sample aliquot, 0.05 ml of DPD, 0.05 ml of POD and 0.05 ml of the sample aliquot were mixed and rapidly stirred for 90 seconds. The ratio of sample aliquots / water was varied according to the concentration of hydrogen peroxide. The calibration curves of hydrogen peroxide concentration were obtained depending on the range of hydrogen peroxide concentration. Absorbance was measured at 551 nm by UV / visible spectrophotometer.

Material property measurement

After the CoPi was deposited directly on the TiO ₂ , it successfully photo-oxidized the water. Changes in functional groups on TiO ₂ , GO, and rGO / TiO ₂ were recorded by the Thermo Scientific iS50 FTIR-ATR. TiO _2, the Raman spectra of GO, and rGO / TiO ₂ was obtained by the Raman microscope BrukerSenterra (BrukerOptics, Inc.) with a laser excitation of 532 nm. X-ray photoelectron spectroscopy (XPS) analysis with an X-ray source using monochromatic Al (1,500 eV) was performed by ESCA LAB250 (VG Scientific). The morphology of rGO / TiO ₂ complexed with cobalt phosphate was investigated by field emission scanning electron microscopy (FE-SEM, JEOL, JSM), transmission electron microscopy (TEM, JEOL, JEM-2200FS) EELS) analysis. The Co K-edge X-ray absorption near-edge structure (XANES) was collected from a Pohang light source (PLS-II) BL8C beam line with a ring current of 200 mA at 3.0 GeV. The monochromatic X-ray beam was obtained from a vacuum undulator radiation source through a Si (111) double crystal monochromator cooled with liquid nitrogen. The X-ray absorption spectra of the powder samples uniformly dispersed at an appropriate thickness were recorded in a fluorescence mode using a 7-element low energy Ge detector (Canberra). To reduce the strong fluorescence signal of TiO ₂ , a 40 mm wide argon filled vinyl pack was placed between the sample and the fluorescence detector. Higher order harmonic contaminants were removed by detuning at X-ray intensity incidence of ~ 30%. Energy calibration was performed simultaneously for each measurement based on the Co metal foil placed in front of the third ion chamber. Experimental spectra The XANES data set-up was performed using standard XAFS procedures.

Photoelectrochemistry  Experiment

The slippery photocurrent was measured by three electrode systems connected to a potentiostat (Gamry, Reference 600). Pt wire, graphite rod, and Ag / AgCl were used as working electrode, counter electrode, and standard electrode, respectively. The photocatalyst suspension (1.0 g / L, 0.1 M NaClO ₄ , pH 1.8) was irradiated with a 300-W Xe arc lamp with an UV cutoff filter (λ320 nm) in the presence of Fe ^{3 +} as an electronic shuttle. Photocurrents were collected with a Pt electrode biased at + 0.7V (vs Ag / AgCl).

The working electrode was fabricated by fixing the sample on the FTO glass by the doctor blade method (Ethanol was utilized) by heating at 200 ° C under an argon gas flow. Pt wire and Ag / AgCl were used as a working electrode and a reference electrode, respectively. The photocurrent response with on-off light was measured by a three electrode system connected to a Potentiostat (Gamry, Reference 600).

All photochemical measurements were performed as follows; Continuous argon gas fuzzing with a bias of pH _i = 3.0, [KClO ₄ ] = 0.1 M, λ> 320 nm, Pt as the counter electrode, +0.86 V (vs.Ag / AgCl).

The linear sweep voltammetry of TiO ₂ , TiO ₂ / CoPi, rGO / TiO ₂ , and rGO / TiO ₂ / CoPi was carried out under a dark, Ar-saturated condition at a scan rate of 20 mV / Buffer solution (pH 7.0). Photolysis of CoPi was performed before measurement.

Photocatalyst Presence or absence of an organic electron donor (2-propanol) (O, X) Concentration of hydrogen peroxide (mM) (after 200 minutes of irradiation) Kinds the graphene weight ratio of rGO / TiO ₂ or the metal weight ratio of metal / TiO ₂ Example 1 rGO / TiO ₂ 1wt% O 0.4 Example 2 rGO / TiO ₂ 6wt% O 0.7 Example 3 rGO / TiO ₂ 10wt% O 0.8 Example 4 rGO / TiO ₂ 20wt% O 0.4 Example 5 rGO / TiO ₂ 40wt% O 0.3 Example 6 rGO / TiO ₂ / P 1wt% O 3.5 Example 7 rGO / TiO ₂ / P 6wt% O 4.3 Example 8 rGO / TiO ₂ / P 10wt% O 3.3 Example 9 rGO / TiO ₂ / P 20wt% O 3.8 Example 10 rGO / TiO ₂ / P 40wt% O 3.0 Example 11 rGO / TiO ₂ 6wt% X 0.001 Example 12 rGO / TiO ₂ / P 6wt% X 0.03 Example 13 rGO / TiO ₂ / Co 6wt% X 0.001 Example 14 rGO / TiO ₂ / CoPi 6wt% X 0.08 Comparative Example 1 TiO ₂ - O 0.2 Comparative Example 2 Ag / TiO ₂ 1wt% O 0.6 Comparative Example 3 Au / TiO ₂ 1wt% O 0.4 Comparative Example 4 Pt / TiO ₂ 1wt% O 0.1 Comparative Example 5 TiO ₂ / P - O 0.015 Comparative Example 6 Ag / TiO ₂ / P 1wt% O 4.7 Comparative Example 7 Au / TiO ₂ / P 1wt% O 4.5 Comparative Example 8 Pt / TiO ₂ / P 1wt% O 0.5 Comparative Example 9 TiO ₂ / CoPi - X 0.02

The rGO / TiO ₂ composites were analyzed by UV-visible spectroscopy, Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS).

Fig. 2 shows the results of the measurement of the concentration of hydrogen peroxide produced in accordance with the material carried on titanium dioxide of Example 3 and Comparative Examples 1 to 4 under UV irradiation ([lambda] > 320 nm) using 2-propanol as the electron donor in the O ₂ equilibrium state As shown in FIG. The rGO-loaded titanium dioxide significantly increased the production of hydrogen peroxide and confirmed that it reached a maximum at 10 wt% rGO content.

FIG. 3 is a graph showing the concentration of hydrogen peroxide produced according to the content of rGO supported on titanium dioxide in Examples 1 to 5 and Comparative Example 1. FIG. Although the photocatalytic activity of rGO itself has been reported for hydrogen production, the hydrogen peroxide photocatalytic activity of rGO / TiO ₂ (40 wt%) can be interpreted as a cocatalytic or electron transfer mediator rather than a photocatalytic as the main role of rGO.

Figure 4 is a graph showing the effect of phosphate groups on the production of photocatalyst of hydrogen peroxide. In the presence of phosphoric acid, the photocatalyst of Example 7 produced hydrogen peroxide above 4.5 mM after 3 hours of light irradiation. In addition, the rate of hydrogen peroxide production in the presence of the phosphoric acid group can be confirmed in FIG.

FIG. 6 is a graph showing the concentration of hydrogen peroxide decomposed according to the presence or absence of a phosphate group in Test Examples 1 and 2 and Comparative Test Examples 1 to 8 according to the material carried on titanium dioxide. Hydrogen peroxide showed the photodegradation effect of Ag / TiO ₂ and Au / TiO ₂ depending on the presence or absence of phosphate groups, and Pt / TiO ₂ showed low activity in the presence of phosphoric acid.

FIG. 7 is a graph showing the concentration of hydrogen peroxide generated in photocatalysts measured in Examples 11 to 14 under respective organic electron donor members. FIG. The hydrogen peroxide production of rGO / TiO ₂ without the phosphoric acid group and the cobalt ion of Example 11 was almost insignificant, and it was confirmed that addition of the single cobalt ion of Example 13 did not improve the formation of hydrogen peroxide at all. On the other hand, in Example 14 in which both the phosphate group and the cobalt ion coexist in the rGO / TiO ₂ suspension, the production of hydrogen peroxide remarkably improved up to 80 uM under the O ₂ bubbling condition.

8 is a graph showing the Raman spectra in the presence of rGO in Example 2 and Comparative Example 1 in the presence of an organic electron donor. G and D bands due to reduced graphene oxide were observed, confirming titanium dioxide carrying reduced graphene oxide.

FIG. 9 is a graph showing X-ray photoelectron spectroscopy (XPS) spectra in the presence of rGO in Example 7 and Comparative Example 5 in the presence of an organic electron donor. The presence of phosphate groups in TiO ₂ / P and rGO / TiO ₂ / P was confirmed by the appearance of P2p spectrum in XPS measurement.

10 is a graph showing X-ray photoelectron spectroscopy (XPS) spectra in the presence of rGO in Example 14 and Comparative Example 9 in the presence of an organic electron donor. The presence of phosphate groups in TiO ₂ / CoPi and rGO / TiO ₂ / CoPi was confirmed by the appearance of P2p spectrum in XPS measurement.

11 is a FE-SEM image (a), a TEM image (b), and an EELS mapping photograph (cf) of Example 14. Fig. The FE-SEM image and the TEM image show rGO supported on the titanium dioxide particle surface. EELS mapping confirmed the presence of carbon, phosphate and cobalt ions in the rGO / TiO ₂ composite, and phosphate and cobalt ions support the in-situ formation of CoPi on the slurry-type titanium dioxide surface rather than the rGO surface. Since CoPi is directly deposited on titanium dioxide, CoPi is considered to photo-oxidize water.

Claims (15)

Contacting the reduced graphene oxide with titanium dioxide to produce titanium dioxide carrying reduced graphene oxide on the surface (step a);
(B) modifying the surface of the titanium dioxide carrying the reducing graphene oxide on its surface with phosphate (phosphate) to produce titanium dioxide carrying reduced graphene oxide and phosphate group (phosphoric acid group) on its surface; And
And a step (c) of preparing a photocatalytic composite comprising a cobalt precursor and titanium dioxide doped with reduced graphene oxide and cobalt phosphate on the surface by introducing the cobalt precursor into the titanium dioxide carrying the reducing graphene oxide and the phosphate group on the surface thereof and,
Wherein the step c is carried out at a pH of 2.0 to 4.0. The method according to claim 1,
Wherein the phosphate is any one selected from the group consisting of NaH ₂ PO ₄ , Na ₂ HPO ₄ , Na ₃ HPO ₄ , KH ₂ PO ₄ , K ₂ HPO ₄ , and K ₃ PO ₄ . The method according to claim 1,
Wherein the cobalt precursor is cobalt perchlorate hexahydrate (Co (ClO ₄ ) ₂ .6H ₂ O). The method according to claim 1,
The step c is a step of dispersing the titanium dioxide supported on the surface of the reduced graphene oxide in a phosphate buffer solution and then adding a cobalt precursor solution to prepare titanium dioxide carrying reduced graphene oxide and cobalt phosphate on the surface thereof Wherein the photocatalytic composite is obtained by a method comprising the steps of: Contacting the reduced graphene oxide with titanium dioxide to produce titanium dioxide carrying reduced graphene oxide on the surface (step a);
(B) modifying the surface of the titanium dioxide carrying the reducing graphene oxide on its surface with phosphate (phosphate) to produce titanium dioxide carrying reduced graphene oxide and phosphate group (phosphoric acid group) on its surface;
A step (c) of preparing a photocatalytic composite comprising a cobalt precursor and titanium dioxide doped with reduced graphene oxide and cobalt phosphate on the surface by introducing the cobalt precursor into the titanium dioxide carrying the reduced graphene oxide and the phosphate group on the surface thereof; And
(Step d) of producing hydrogen peroxide by reacting water using the photocatalytic composite as a catalyst under light irradiation,
Wherein step c is carried out at a pH of 2.0 to 4.0. 6. The method of claim 5,
Wherein the light used in the light irradiation is ultraviolet light. delete delete delete delete delete delete delete delete delete

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