WO2017012210A1

WO2017012210A1 - Metal oxide-carbon nitride composite material and preparation method and use thereof

Info

Publication number: WO2017012210A1
Application number: PCT/CN2015/091192
Authority: WO
Inventors: 项顼; 王瑞瑞; 潘科成
Original assignee: 北京化工大学
Priority date: 2015-07-21
Filing date: 2015-09-30
Publication date: 2017-01-26
Also published as: CN105032465A; CN105032465B

Abstract

Provided are a metal oxide-carbon nitride composite material and a preparation method and use thereof. The composite material consists of carbon nitride and a composite metal oxide uniformly dispersed on its surface, and the mass ratio of the carbon nitride to the composite metal oxide is 10-200 : 1. The preparation method has a simple process, and mild reaction conditions. The catalytic performance of the composite material can be optimized by adjusting the ratio between the composite metal oxide and the carbon nitride. The composite material can catalyze H₂O and O₂ to cleanly produce H₂O₂ at normal temperature and normal pressure, and the concentration of H₂O₂ is high.

Description

Metal oxide-carbon nitride composite material and preparation method and application thereof

Technical field

The invention relates to a metal oxide-carbon nitride composite material, a preparation method and application thereof, and belongs to the technical field of catalytic materials.

Background technique

The demand for energy in today's society is becoming more and more urgent, but the problems such as energy shortage and environmental degradation are becoming more and more prominent. Developing renewable and clean energy is an important way to solve these problems. Because solar energy has the characteristics of huge energy consumption and clean and pollution-free use process, it is regarded as one of the important targets of new energy utilization. Hydrogen peroxide (H ₂ O ₂ ) is an important form of solar fuel that can be synthesized by light. When used as an energy source, the product is only H ₂ O or O ₂ , and has no carbon emission, which is a promising clean energy source. As a kind of solar fuel, H ₂ O ₂ can achieve full chain green process from the energy source of its production process to the conversion to the final use product. Moreover, H ₂ O ₂ is a clean, green oxidizing agent with a wide range of applications in paper, textile, printing and dyeing, electronics, food, environmental and chemical synthesis.

At present, the main method for industrially producing H ₂ O ₂ is the hydrazine method, which has the advantages that the device is easy to be enlarged, and the yield is high. The shortcoming is that the production system is complex, the energy consumption in the production process is large, and H ₂ O ₂ and organic substances are present in the reaction system at the same time, which is prone to explosion hazard and high toxicity. Therefore, H ₂ O ₂ direct synthesis using H ₂ and O ₂ as raw materials has been developed (Science, 2009, 323, 1037-1041.), which is usually based on the noble metal Au, Pd or bimetallic AuPd. Water is the medium, and H ₂ O ₂ is selectively formed by the reaction of H _{2 and} O ₂ . This method basically does not use organic solvents, and is greener and more environmentally friendly than the hydrazine method. However, the gas mixture system of H ₂ and O ₂ has an explosion risk in a wide concentration range and is difficult to control, and it is necessary to finely adjust the ratio of the two in the synthesis, or to add a diluent (for example, N ₂ gas, Ar gas). However, this has an effect on the reaction, resulting in a low selectivity of H ₂ O ₂ and a low yield.

Document [1] (ACS Catal., 2012, 2, 599-603; J. Am. Chem. Soc., 2010, 132, 7850-7851.) discloses the use of oxides (e.g., TiO ₂ ) or noble metals Au, Ag. The oxide is a catalyst, and the photogenerated electrons generated under photoexcitation reduce oxygen, and then a series of radical conversion processes can form a technical solution of H ₂ O ₂ . However, the catalyst of this method requires the use of precious metals, which are very limited in resources and expensive, and are not suitable for industrial production and promotion.

Document [2] (Energy Environ. Sci., 2014, 7, 4023-4028.) discloses the use of graphene-TiO ₂ composites to promote the rapid conduction of conduction band electrons of TiO ₂ to the surface and participate in the production of H ₂ O ₂ . reaction. However, TiO ₂ easily decomposes H ₂ O ₂ , and an external phosphoric acid solution is required to suppress decomposition of H ₂ O ₂ , thereby increasing production complexity and increasing equipment requirements.

Document [3] (Chem. Commun., 2005, 2627-2629) discloses a technique for reducing the decomposition of H ₂ O ₂ on the surface of TiO ₂ and improving the yield by modifying TiO ₂ with fluoride ion (F ^- ). However, the hydrogen fluoride (HF) used is highly corrosive and has a high operational risk, which increases the cost and risk of industrial production.

Document [4] (Energy Environ. Sci., 2013, 6, 3756-3764.) discloses the use of a Ru complex ([Ru ^II (Me ₂ phen) ₃ ] ²⁺ ) as a photosensitizer, combined with a water oxidation catalyst (Ir A method in which (OH) ₃ or [Co ^III (Cp*)(bpy)(H ₂ O)] ²⁺ ) co-produces H ₂ O ₂ . However, this method requires the use of precious metals (Ru and Ir), which is expensive and not suitable for large-scale production.

Literature [5] (ACS Catal., 2014, 4, 774-780) found that carbon nitride can catalyze the selective formation of H ₂ O ₂ because of the formation of H ₂ O ₂ , the peroxy group (-OO-) The formation of a stable endoperoxide with carbon nitride suppresses the decomposition of H ₂ O ₂ and thus can increase the yield and selectivity of H ₂ O ₂ . However, this method requires the use of organic alcohol to provide a hydrogen source, which significantly increases the production cost, and also causes carbon emission pollution problems, and cannot achieve clean production.

Therefore, the development of a method that uses only water and oxygen as raw materials and mild reaction under the action of a catalyst to cleanly produce H ₂ O ₂ will have a promising prospect and an industrial production prospect.

Summary of the invention

In order to solve the above technical problems, an object of the present invention is to provide a metal oxide-carbon nitride composite material.

Another object of the present invention is to provide a method for preparing the above metal oxide-carbon nitride composite material.

It is also an object of the present invention to provide an application of the above metal oxide-carbon nitride composite for catalyzing the preparation of H ₂ O ₂ from water and oxygen.

In order to achieve the above object, the present invention provides a metal oxide-carbon nitride composite material composed of a composite metal oxide and carbon nitride, which is uniformly dispersed on a surface of a carbon nitride and nitrided. The mass ratio of carbon to composite metal oxide is 10-200:1.

According to a preferred embodiment of the present invention, the composite metal oxide includes a NiFe composite oxide, a CoFe composite oxide, or a CoNiFe composite oxide.

According to a preferred embodiment of the present invention, the NiFe composite oxide, the CoFe composite oxide or the CoNiFe composite oxide are all amorphous.

According to a preferred embodiment of the present invention, the carbon nitride is in the form of a sheet having a size of 30 to 600 nm, and the crystal structure belongs to a graphite phase. The scanning electron micrograph of the carbon nitride used in the present invention is shown in FIG. 3. The above "size" refers to the size of the irregular particles in the scanning electron micrograph in the maximum length direction, which can be observed by scanning electron micrograph of carbon nitride. inferred.

The invention also provides a preparation method of the above metal oxide-carbon nitride composite material, the method comprising the following steps:

a, the metal salt, precipitant, complexing agent dissolved in deionized water, ultrasonic, to obtain a solution A;

b, adding carbon nitride to solution A, stirring uniformly under ultrasonic conditions, carrying out the reaction, after completion of the reaction, cooling, filtering, washing and drying to obtain a composite metal hydroxide-carbon nitride composite material;

c. calcining the composite metal hydroxide-carbon nitride composite material to obtain the metal oxide-carbon nitride composite material.

According to a preferred embodiment of the present invention, in the preparation step a, the present invention does not require the order of addition of the metal salt, the precipitant, and the complexing agent. In addition, the ultrasonic operation in the step a is to make the metal salt, the precipitant and the complexing agent better dissolved in the deionized water. Therefore, those skilled in the art can select an appropriate ultrasonic time according to the needs of the field operation, which is preferred in the present invention. In the embodiment, the time of the ultrasound is 3-30 min.

According to a preferred embodiment of the present invention, in the preparation step b, since carbon nitride is not easily dispersed in water and stirring cannot be dispersed in water, step b must be performed under ultrasonic conditions to uniformly disperse carbon nitride. . A person skilled in the art can also select a suitable ultrasonic stirring time according to the needs of field work. In a preferred embodiment of the present invention, the stirring time in the step b is 10-30 min under ultrasonic conditions.

According to a preferred embodiment of the present invention, in the preparation process, when the metal salt contains a nickel salt, the nickel salt comprises nickel nitrate, nickel sulfate or nickel chloride;

When the metal salt contains an iron salt, the iron salt comprises iron nitrate, iron sulfate or ferric chloride;

When the metal salt contains a cobalt salt, the cobalt salt includes cobalt nitrate, cobalt chloride or cobalt sulfate.

According to a preferred embodiment of the invention, the concentration of the nickel salt and/or the cobalt salt in the solution A during the preparation is from 0.004 to 0.3 mol/L. Wherein, the concentration of the nickel salt and the cobalt salt is 0.004 to 0.3 mol/L, which means that the sum of the concentrations of the nickel salt and the cobalt salt is 0.004 to 0.3 mol/L.

According to a preferred embodiment of the invention, the molar ratio of the nickel salt and/or cobalt salt to the iron salt during the preparation is from 2 to 4:1. Wherein, the molar ratio of the nickel salt and the cobalt salt to the iron salt is 2-4:1, which means that the ratio of the sum of the moles of the nickel salt and the cobalt salt to the mole of the iron salt is 2-4:1.

According to a preferred embodiment of the invention, the molar ratio of carbon nitride to iron salt during the preparation is from 25 to 600:1.

According to a preferred embodiment of the invention, the molar ratio of the precipitating agent to the metal salt during the preparation is from 2 to 8:1. Wherein, when the composite metal oxide is a NiFe composite oxide, the metal salt comprises a nickel salt and an iron salt, and the molar ratio of the precipitant to the metal salt is from 2 to 8:1 means the number of moles of the precipitant and the nickel salt and The ratio of the sum of the moles of iron salt is 2-8:1;

When the composite metal oxide is a CoFe composite oxide, the metal salt includes a cobalt salt and an iron salt, and the molar ratio of the precipitant to the metal salt is 2-8:1, which means the number of moles of the precipitant and the cobalt salt and the iron salt. The ratio of the sum of moles is 2-8:1;

When the composite metal oxide is a CoNiFe composite oxide, the metal salt includes a cobalt salt, a nickel salt and an iron salt, and the molar ratio of the precipitating agent to the metal salt is 2-8:1, which means the molar amount of the precipitating agent and the cobalt salt. The ratio of the sum of the moles of nickel salt and iron salt is 2-8:1.

According to a preferred embodiment of the invention, the precipitating agent comprises urea, hexamethylenetetramine or aqueous ammonia during the preparation. Ammonia water is a conventional reagent used in the art, and the present invention does not require a concentration of ammonia water. The concentration of ammonia water used in a preferred embodiment of the present invention is 25 wt%, which is a concentration generally used in the art.

According to a preferred embodiment of the invention, the molar ratio of the complexing agent to the metal salt during the preparation is from 4 to 10:1. Wherein, when the composite metal oxide is a NiFe composite oxide, the metal salt comprises a nickel salt and an iron salt, and the molar ratio of the complexing agent to the metal salt is 4-10:1 means the number of moles of the complexing agent and nickel The ratio of the sum of the moles of salt and iron salt is 4-10:1;

When the composite metal oxide is a CoFe composite oxide, the metal salt includes a cobalt salt and an iron salt, and the molar ratio of the complexing agent to the metal salt is 4-10:1, which means the molar amount of the complexing agent and the cobalt salt and The ratio of the sum of the moles of the iron salt is 4-10:1;

When the composite metal oxide is a CoNiFe composite oxide, the metal salt includes a cobalt salt, a nickel salt and an iron salt, and the molar ratio of the complexing agent to the metal salt is 4-10:1, which means the number of moles of the complexing agent and The ratio of the sum of the moles of the cobalt salt, the nickel salt and the iron salt is 4-10:1.

According to a preferred embodiment of the invention, the complexing agent comprises ammonium fluoride during the preparation.

According to a preferred embodiment of the invention, during the preparation, the temperature of the reaction in step b is from 100 to 150 ° C and the reaction time is from 10 to 24 h.

According to a preferred embodiment of the invention, the cooling is cooled to room temperature during the preparation.

According to a preferred embodiment of the invention, during the preparation, the washing is to wash the reaction product to a pH of 7. The washing operation is a conventional technical means in the art, and those skilled in the art can wash the reaction product according to the operation requirements to wash the reaction product to a pH of 7. In the preferred embodiment of the present invention, ordinary tap water, deionized can be used. The reaction product is washed with water or the like.

According to a preferred embodiment of the invention, during the preparation, the drying is carried out at 60-80 ° C for 6-12 h.

According to a preferred embodiment of the present invention, during the preparation, the calcination is carried out by heating to 250-400 ° C for 1-8 h in a nitrogen or air atmosphere.

According to a preferred embodiment of the present invention, the temperature increase rate of the temperature rise is 1-10 ° C / min during the preparation.

The present invention also provides the use of the above metal oxide-carbon nitride composite material for catalyzing the preparation of H ₂ O ₂ from water and oxygen.

The metal oxide-carbon nitride composite material provided by the invention is prepared by dissolving a metal salt, a precipitating agent and a complexing agent in water to form a solution, adding carbon nitride thereto, and after ultrasonically stirring sufficiently, The reaction was carried out in a hydrothermal kettle to form a double metal hydroxide-carbon nitride (LDH-C ₃ N ₄ ) composite. Then, it is calcined under air or an inert atmosphere to dehydrate the double metal hydroxide, remove the interlayer anion, and the structure is converted into a composite metal oxide, and the structure of the carbon nitride does not change during the process, and the metal oxide is obtained. - Carbon nitride composite (MMO-C ₃ N ₄ ). The composite material is used as a catalyst for producing H ₂ O ₂ using water and oxygen as raw materials, and the clean production of H ₂ O ₂ can be realized at normal temperature and normal pressure.

The metal oxide-carbon nitride composite material provided by the invention is a composite material composed of a composite oxide and a C ₃ N ₄ composite, wherein the composite oxide is a NiFe composite oxide, which is amorphous and uniformly dispersed on the surface of the carbon nitride; C ₃ N ₄ is in the form of a sheet having a size of ₃₀ to 200 nm; and the mass ratio of C ₃ N ₄ to the NiFe composite oxide is 10 to 200:1.

The method for preparing a metal oxide-carbon nitride composite material (NiFe composite oxide-carbon nitride composite material) provided by the present invention may include the following specific preparation steps:

A. Dissolving nickel salt, iron salt, urea, ammonium fluoride in deionized water, wherein the nickel salt concentration is 0.004-0.3 mol/L, and the molar ratio of nickel salt to iron salt is 2-4:1, urea The molar concentration is 2-8 times the sum of the molar concentration of nickel salt and iron salt, the molar concentration of ammonium fluoride is 4-10 times the sum of the molar concentration of nickel salt and iron salt, ultrasonic 3-30min, to obtain solution A;

The nickel salt is one of nickel nitrate, nickel sulfate, and nickel chloride, and the iron salt is one of iron nitrate, iron sulfate, and ferric chloride;

B. Add C ₃ N ₄ to solution A, wherein the molar concentration ratio of C ₃ N ₄ to iron salt is 25-600, stir while stirring for 10-30 min, and then move to a hydrothermal kettle at 100 ° C - 150 ° C The reaction is carried out for 10-24 hours, cooled to room temperature, washed with suction to pH=7, and dried at 60-80 ° C for 6-12 h to obtain NiFe-LDH-C ₃ N ₄ ; the C ₃ N ₄ is in the form of flakes, size It is 30-200 nm, and the crystal structure is a graphite phase;

C. The NiFe-LDH-C ₃ N ₄ obtained in step B is placed in a muffle furnace, calcined in a nitrogen or air atmosphere, and raised to 250-400 ° C at a heating rate of 1-10 ° C / min, and kept for 1-8 h. , NiFe composite oxide - C ₃ N _{4 was obtained} .

The present invention further provides a metal oxide - carbonitride composite applications, the composite material for water and oxygen as raw materials under sunlight as an energy donor catalyst H _₂ O ₂ production process.

The metal oxide-carbon nitride material prepared by the invention is a composite material composed of an oxide and a carbon nitride (C ₃ N ₄ ), wherein the oxide is a NiFe composite oxide, which is amorphous and uniformly dispersed in nitrogen. Carbonized surface; C ₃ N ₄ is in the form of a sheet having a size of 30-200 nm; and the mass ratio of carbon nitride to NiFe composite oxide is 10-200:1.

The specific preparation steps of the metal oxide-carbon nitride material are as follows:

A. Dissolving nickel salt, iron salt, urea, ammonium fluoride in deionized water, wherein the nickel salt concentration is 0.004-0.3 mol/L, the molar ratio of nickel salt to iron salt is 2-4, and the molar ratio of urea The concentration is 2-8 times the sum of the molar concentrations of the nickel salt and the iron salt, the molar concentration of the ammonium fluoride is 4-10 times the sum of the molar concentrations of the nickel salt and the iron salt, and the ultrasonic solution is 3-30 min to obtain the solution A.

The nickel salt is one of nickel nitrate, nickel sulfate, and nickel chloride, and the iron salt is one of iron nitrate, iron sulfate, and ferric chloride.

B. Add C ₃ N ₄ to solution A, wherein the molar concentration ratio of C ₃ N ₄ to iron salt is 25-600, while ultrasonically stirring for 10-30 min, then moving to a hydrothermal kettle at 100 ° C - 150 ° C conditions The reaction was carried out for 10-24 h, cooled to room temperature, washed with suction to pH = 7, and dried at 60-80 ° C for 6-12 h to obtain NiFe-LDH-C ₃ N ₄ . The C ₃ N ₄ is in the form of a sheet having a size of 30 to 200 nm, and the crystal structure is a graphite phase, and the carbon nitride is disclosed according to the literature (J. Mater. Chem. A, 2014, 2, 4605-4612.). The method of preparation is carried out.

C. The NiFe-LDH-C ₃ N ₄ obtained in the step B is placed in a muffle furnace and calcined in a nitrogen or air atmosphere, and the calcination conditions are as follows: the temperature is raised to 250-400 ° C at a temperature increase rate of 1-10 ° C / min, The temperature was maintained for 1-8 h to obtain a NiFe composite oxide-C ₃ N ₄ .

The obtained sample was characterized by X-ray diffractometry (XRD). The results are shown in Fig. 1. Two diffraction peaks can be found from Fig. 1, which correspond to the (100) and (002) crystal faces of the graphite phase carbon nitride, respectively. There is no diffraction of the metal oxide, indicating that the metal oxide is present in a small amount or in an amorphous state.

The NiFe composite oxide-C ₃ N ₄ prepared above was used as a catalyst for producing H ₂ O ₂ , and the specific method (this method was carried out according to the literature Energy Environ. Sci. 2014, 7, 4023-4028.) was as follows: Add 15mL-2L deionized water to the glass (or stainless steel) reactor, weigh 15mg-10g catalyst into the reactor, and add 0.1M-1M HClO ₄ to pH=3.0 at room temperature under magnetic stirring. In the absence of light, magnetic stirring (rotation speed of 300-1000 rev / min), the purity of more than 99% O ₂ 30min (aeration rate of 5-100mL / min), the solution reached dissolved oxygen saturation, and then use the xenon lamp Irradiation (light intensity 60-120 mW/cm ² ), kept stirring, reaction 3-24 hours, timed sampling test to generate H ₂ O ₂ concentration, the results are shown in Table 1.

The present invention has the following remarkable effects:

(1) The metal oxide-carbon nitride material is prepared by using the rich elements of the earth, nickel, iron and carbon. As a catalyst for the production of H ₂ O ₂ , it has the characteristics of low cost and sustainability, and is suitable for large-scale development.

(2) Producing H ₂ O ₂ only with water and oxygen as raw materials and sunlight as energy source. The whole process does not involve organic reagents, organic solvents, no carbon emissions, mild reaction conditions (normal temperature, normal pressure), and is truly green. The clean production process; and the concentration of the product H ₂ O ₂ is higher than the concentration of the non-precious metal, precious metal catalyst disclosed in the prior art.

(3) The preparation process of the composite material is simple, the reaction conditions are mild, and the equipment requirements are not critical; the ratio between the metal oxide and the carbon nitride can be flexibly modulated to optimize the performance of the catalyst, which is very suitable for the engineering enlargement of the product. .

DRAWINGS

1 is an XRD chart of a metal oxide-carbon nitride product according to Embodiment 1 of the present invention;

2 is an electron micrograph of a metal oxide-carbon nitride composite material prepared in Example 1 of the present invention: (a) is a scanning electron micrograph of C ₃ N ₄ , and (b) is a NiFe composite oxide-C ₃ N ₄ Scanning electron micrograph of the composite material, (c) is a transmission electron micrograph of the NiFe composite oxide-C ₃ N ₄ composite material;

Figure 3 is a scanning electron micrograph of carbon nitride used in the present invention.

detailed description

In order to better understand the technical features, objects, and advantages of the present invention, the embodiments of the present invention and the advantages thereof will be described in detail by the specific embodiments and the accompanying drawings. The spirit and characteristics of the present invention are understood, but are not intended to limit the scope of the invention.

Example 1

The present embodiment provides a method for preparing a NiFe composite oxide-C ₃ N ₄ composite material, wherein the method comprises the following steps:

a, weighing 0.0872g nickel nitrate, 0.0404g iron nitrate, 0.1201g urea, 0.0741g ammonium fluoride dissolved in 50mL deionized water, ultrasonic 5min, to obtain a solution A;

b. Add 2.76 g of C ₃ N ₄ to solution A, stir while stirring for 20 min, transfer to a hydrothermal kettle, react at 120 ° C for 12 h, cool to room temperature, wash by suction to pH = 7, and dry at 70 ° C for 12 h. Obtaining NiFe-LDH-C ₃ N ₄ ;

c. NiFe-LDH-C ₃ N ₄ obtained in step b is placed in a muffle furnace and calcined in air. The calcination conditions are as follows: the temperature is raised to 300 ° C at a heating rate of 5 ° C / min, and the temperature is maintained for 1 h to obtain a NiFe composite oxide. a -C ₃ N ₄ composite in which the mass ratio of C ₃ N ₄ to NiFe composite oxide is 50:1.

The NiFe composite oxide-C ₃ N ₄ composite prepared in Example 1 was analyzed by X-ray diffraction (XRD), and the XRD spectrum thereof is shown in FIG. 1 . From FIG. 1 , the NiFe prepared in Example 1 can be found. The XRD spectrum of the composite oxide-C ₃ N ₄ composite has two diffraction peaks corresponding to the (100) and (002) crystal planes of the graphite phase carbon nitride, and the diffraction of the composite metal oxide does not appear in the XRD spectrum. The peak indicates that the content of the composite metal oxide is small or amorphous.

The NiFe composite oxide-C ₃ N ₄ composite prepared in Example 1 was analyzed by scanning electron microscopy and transmission electron microscopy, and its electron micrograph is shown in Fig. 2. In Fig. 2, (a) is a scan of C ₃ N ₄ . electron micrographs, (b) a composite oxide of NiFe -C ₃ N ₄ SEM images of the composite material, (c) is a -C ₃ N ₄ composite material NiFe composite oxide TEM FIG. It can be seen from (a) and (b) in Fig. 2 that the surface of C ₃ N ₄ is smooth, and the surface of the NiFe composite oxide-C ₃ N ₄ composite is rough due to the complex metal oxide in the nitrogen. It is caused by the deposition of carbon surface; it can be seen from (c) in Fig. 2 that the composite metal oxide particles are distributed on the surface of carbon nitride, and the lattice of NiO can be observed from the lattice image, indicating that there is a crystalline state. NiO exists.

The elemental composition of the NiFe composite oxide-C ₃ N ₄ composite prepared in Example 1 was tested by inductively coupled plasma emission spectrometry (ICP). The concentration of nickel element was 5.27129 mg/L by ICP. The concentration of the element was 2.00255 mg/L, from which the mass ratio of nickel to iron was calculated to be 2.63:1, and then divided by the relative atomic mass of nickel and iron (Ni: 58.693, Fe: 55.845), and finally Example 1 was obtained. The molar ratio of Ni and Fe in the prepared NiFe composite oxide-C ₃ N ₄ composite was 2.50:1. The test results show that NiO is the main component in the NiFe composite oxide-C ₃ N ₄ composite, and Fe The oxide content is less.

Example 2

a weigh 0.1104g nickel sulfate, 0.0735g iron sulfate, 0.1682g urea, 0.2074g ammonium fluoride dissolved in 70mL deionized water, ultrasonic 5min, to obtain a solution A;

b. Add 2.576 g of C ₃ N ₄ to solution A, stir while stirring for 20 min, transfer to a hydrothermal kettle, react at 140 ° C for 12 h, cool to room temperature, wash by suction to pH = 7, and dry at 80 ° C for 10 h. Obtaining NiFe-LDH-C ₃ N ₄ ;

c. NiFe-LDH-C ₃ N ₄ obtained in step b is placed in a muffle furnace and calcined in nitrogen. The calcination conditions are as follows: the temperature is raised to 300 ° C at a heating rate of 5 ° C / min, and the temperature is maintained for 2 h to obtain a NiFe composite oxide. a -C ₃ N ₄ composite in which the mass ratio of C ₃ N ₄ to NiFe composite oxide is 30:1.

Example 3

a weigh 0.1426g of nickel chloride, 0.05418g of ferric chloride, 0.2402g of urea, 0.2963g of ammonium fluoride dissolved in 100mL of deionized water, ultrasonic 5min, to obtain a solution A;

b, adding 5.52g of C ₃ N ₄ to solution A, stirring while stirring for 20min, moving to a hydrothermal kettle, reacting at 120 ° C for 12 h, cooling to room temperature, washing with suction to pH = 7, and drying at 70 ° C for 12 h. Obtaining NiFe-LDH-C ₃ N ₄ ;

c. NiFe-LDH-C ₃ N ₄ obtained in step b is placed in a muffle furnace and calcined in air. The calcination conditions are as follows: the temperature is raised to 400 ° C at a heating rate of 10 ° C / min, and the temperature is maintained for 1 h to obtain a NiFe composite oxide. a -C ₃ N ₄ composite in which the mass ratio of C ₃ N ₄ to NiFe composite oxide is 50:1.

Example 4

a, weighing 0.0872g nickel nitrate, 0.0404g iron nitrate, 0.1201g urea, 0.1482g ammonium fluoride dissolved in 50mL deionized water, ultrasonic 5min, to obtain a solution A;

b. Add 5.52g of C ₃ N ₄ to solution A, stir while stirring for 30 min, transfer to a hydrothermal kettle, react at 120 ° C for 12 h, cool to room temperature, wash by suction to pH = 7, and dry at 70 ° C for 12 h. Obtaining NiFe-LDH-C ₃ N ₄ ;

c. NiFe-LDH-C ₃ N ₄ obtained in step b is placed in a muffle furnace and calcined in air. The calcination conditions are as follows: the temperature is raised to 350 ° C at a heating rate of 5 ° C / min, and the temperature is maintained for 2 h to obtain a NiFe composite oxide. a -C ₃ N ₄ composite in which the mass ratio of C ₃ N ₄ to NiFe composite oxide is 100:1.

Example 5

This embodiment provides a method for preparing a CoFe composite oxide-C ₃ N ₄ composite material, wherein the method comprises the following steps:

a, weighing 0.0873g of cobalt nitrate, 0.0404g of ferric nitrate, 0.0741g of ammonium fluoride dissolved in 50mL of deionized water, adding 0.3mL of ammonia water, ultrasonic 5min, to obtain a solution A;

b. Add 2.576g of C ₃ N ₄ to solution A, stir while stirring for 20 min, transfer to a hydrothermal kettle and react at 140 ° C for 12 h, cool to room temperature, wash by suction to pH = 7, and dry at 80 ° C for 10 h. CoFe-LDH-C ₃ N ₄ ;

c. The CoFe-LDH-C ₃ N ₄ obtained in the step b is placed in a muffle furnace and calcined in nitrogen. The calcination conditions are as follows: the temperature is raised to 300 ° C at a heating rate of 5 ° C / min, and the temperature is maintained for 1 h to obtain a CoFe composite oxide. a -C ₃ N ₄ composite in which the mass ratio of carbon nitride to CoFe composite oxide is 50:1.

Example 6

This embodiment provides a method for preparing a CoNiFe composite oxide-C ₃ N ₄ composite material, wherein the method comprises the following steps:

a weighed 0.0436g of cobalt nitrate, 0.0436g of nickel nitrate, 0.0404g of ferric nitrate, 0.2804g of hexamethylenetetramine, 0.2963g of ammonium fluoride dissolved in 100mL of deionized water, ultrasonic 5min, to obtain a solution A;

b. Add 5.52g of C ₃ N ₄ to solution A, stir while stirring for 20 min, transfer to a hydrothermal kettle and react at 120 ° C for 12 h, cool to room temperature, wash by suction to pH = 7, and dry at 80 ° C for 12 h. CoNiFe-LDH-C ₃ N ₄ ;

c. The CoNiFe-LDH-C ₃ N ₄ obtained in the step b is placed in a muffle furnace and calcined in air. The calcination conditions are as follows: the temperature is raised to 300 ° C at a heating rate of 10 ° C / min, and the temperature is maintained for 1 h to obtain a CoNiFe composite oxide. A -C ₃ N ₄ composite material in which the mass ratio of carbon nitride to CoNiFe composite oxide is 50:1.

Application example 1

In this application example, the NiFe composite oxide-C ₃ N ₄ composite material prepared in each of Examples 1-4 is used for catalyzing the reaction of producing H ₂ O ₂ from water and oxygen as a raw material, and specifically includes the following steps:

0.3 L of deionized water was added to the reactor, and 0.6 g of the catalyst (the NiFe composite oxide-C ₃ N ₄ composite prepared in each of Examples 1-4) was weighed and added to the reactor at room temperature and magnetic force. Under stirring, 1 M HClO ₄ was added dropwise to pH=3.0, and the solution was first dissolved in a dissolved oxygen state by O ₂ 30 min (aeration rate of 10 mL/min) under a light-free magnetic stirring (500 rpm). Then, using a xenon lamp irradiation (light intensity of 100 mW/cm ² ), a time sampling test was performed to generate a concentration of H ₂ O ₂ , and different reaction times were measured to generate a concentration value of H ₂ O ₂ , as shown in Table 1.

Table 1 Different reaction time H ₂ O ₂ concentration value (μmol / L)

	3小时3 hours	6小时6 hours	9小时9 hours	12小时12 hours
实施例1Example 1	120120	181181	298298	330330
实施例2Example 2	117117	175175	289289	322322
实施例3Example 3	118118	179179	292292	325325
实施例4Example 4	105105	171171	272272	318318
对比样品1Comparative sample 1	1818	--	--	--
对比样品2Comparative sample 2	7878	--	--	--
对比样品3Comparative sample 3	100100	150150	185185	--

The relevant data of Comparative Sample 1 (TiO ₂ /CoPi) and Comparative Sample 2 (rGO/TiO ₂ /CoPi) in Table 1 are the data disclosed in the literature [2], and the solution used for the test is 0.1 mol·L ^-1 . Phosphate buffer.

The relevant data of Comparative Sample 3 ([Ru ^II (Me ₂ phen) ₃ ] ^{2+ in combination} with Ir(OH) ₃ ) in Table 1 is the data disclosed in the literature [4], and the solution used for the test is 2 mol·L ^-1 Sulfuric acid.

It can be seen from Table 1 that in the process of catalytically producing H ₂ O ₂ in the NiFe composite oxide-C ₃ N ₄ composite catalyst prepared by the present invention, the concentration of the product H ₂ O _{2 is} the same reaction time. The non-precious metal catalyst disclosed in the prior art has a corresponding concentration of 1.5-6 times, which is 1.2-1.5 times of the corresponding concentration of the noble metal catalyst, and the NiFe composite oxide-C ₃ N ₄ composite catalyst prepared by the invention is used for catalytic production of H. No additional phosphoric acid or a strongly acidic solution is required during the ₂ O ₂ process.

Application example 2

This application example uses the CoFe composite oxide-C ₃ N ₄ composite prepared in Example 5 to catalyze the reaction of producing H ₂ O ₂ from water and oxygen as a raw material, and specifically includes the following steps:

30 mL of deionized water was added to the glass reactor, and 15 mg of the CoFe composite oxide-C ₃ N ₄ composite catalyst prepared in Example 5 was weighed into the reactor, and 1 M HClO was added dropwise at room temperature under magnetic stirring. ₄ to pH=3.0, firstly pass the oxygen for 30 min (with aeration rate of 10 mL/min) under the condition of non-light magnetic stirring (500 rpm) to make the solution reach dissolved oxygen saturation, and then irradiate with xenon lamp (light intensity is 100mW). /cm ² ), reaction for 12 hours, this process is timed sampling test.

Performance evaluation: When the reaction was measured for 12 h, the concentration of the product H ₂ O ₂ was 152 μmol/L.

Application Example 3

In this application example, the CoNiFe composite oxide-C ₃ N ₄ composite prepared in Example 6 is used for catalyzing the reaction of producing H ₂ O ₂ from water and oxygen as a raw material, and specifically includes the following steps:

30 mL of deionized water was added to the glass reactor, and 45 mg of the CoNiFe composite oxide-C ₃ N ₄ composite catalyst prepared in Example 6 was weighed into the reactor, and 1 M HClO was added dropwise at room temperature under magnetic stirring. ₄ to pH=3.0, firstly pass the oxygen for 30 minutes (with aeration rate of 10mL/min) under the condition of non-light magnetic stirring (rotation speed of 700 rev/min) to make the solution reach dissolved oxygen saturation state, and then irradiate with xenon lamp (light intensity is 90mW). /cm ² ), reaction for 9 hours, this process is timed sampling test.

Performance evaluation: When the reaction was carried out for 9 hours, the concentration of the product H ₂ O ₂ was 132 μmol/L.

Claims

A metal oxide-carbon nitride composite material, wherein the composite material is composed of a composite metal oxide and a carbon nitride, the composite metal oxide is uniformly dispersed on a surface of a carbon nitride, a carbon nitride and a composite metal oxide The mass ratio is 10-200:1.
The composite material according to claim 1, wherein the composite metal oxide comprises a NiFe composite oxide, a CoFe composite oxide or a CoNiFe composite oxide.
The composite material according to claim 2, wherein the NiFe composite oxide, the CoFe composite oxide, and the CoNiFe composite oxide are all in an amorphous state.
The composite material according to claim 1, wherein the carbon nitride is in the form of a sheet having a size of 30 to 600 nm, and the crystal structure is a graphite phase.
A method of producing a metal oxide-carbon nitride composite according to any one of claims 1 to 4, wherein the method comprises the steps of:

a, the metal salt, precipitant, complexing agent dissolved in deionized water, ultrasonic, to obtain a solution A;

b, adding carbon nitride to solution A, stirring uniformly under ultrasonic conditions, carrying out the reaction, after completion of the reaction, cooling, filtering, washing and drying to obtain a composite metal hydroxide-carbon nitride composite material;

c. calcining the composite metal hydroxide-carbon nitride composite material to obtain the metal oxide-carbon nitride composite material.
The production method according to claim 5, wherein when the metal salt contains a nickel salt, the nickel salt comprises nickel nitrate, nickel sulfate or nickel chloride;

When the metal salt contains an iron salt, the iron salt comprises iron nitrate, iron sulfate or ferric chloride;

When the metal salt contains a cobalt salt, the cobalt salt includes cobalt nitrate, cobalt chloride or cobalt sulfate.
The production method according to claim 6, wherein the concentration of the nickel salt and/or the cobalt salt in the solution A is from 0.004 to 0.3 mol/L.
The production method according to claim 6, wherein the molar ratio of the nickel salt and/or cobalt salt to the iron salt is 2-4:1.
The production method according to claim 6, wherein the molar ratio of the carbon nitride to the iron salt is from 25 to 600:1.
The production method according to claim 5, wherein the molar ratio of the precipitating agent to the metal salt is from 2 to 8:1.
The production method according to claim 5, wherein the precipitating agent comprises urea, hexamethylenetetramine or aqueous ammonia.
The production method according to claim 5, wherein the molar ratio of the complexing agent to the metal salt is from 4 to 10:1.
The production method according to claim 5, wherein the complexing agent comprises ammonium fluoride.
The production method according to claim 5, wherein the reaction temperature is from 100 to 150 ° C and the reaction time is from 10 to 24 hours.
The production method according to claim 5, wherein the cooling is cooling to room temperature.
The production method according to claim 5, wherein the washing is washing the reaction product to a pH of 7.
The production method according to claim 5, wherein the drying is drying at 60 to 80 ° C for 6 to 12 hours.
The production method according to claim 5, wherein the calcination is carried out by heating to 250 to 400 ° C for 1 to 8 hours in a nitrogen or air atmosphere.
The production method according to claim 18, wherein the temperature increase rate of the temperature rise is 1-10 ° C / min.
Use of the metal oxide-carbon nitride composite according to any one of claims 1 to 4 for catalyzing the preparation of H 2 O 2 from water and oxygen.