阅读说明：本技术 碳掺杂的介孔石墨化氮化碳纳米球及其制备方法与应用 (Carbon-doped mesoporous graphitized carbon nitride nanosphere and preparation method and application thereof ) 是由 杨英 李泽霖 顾林 郝世杰 于 2019-11-07 设计创作，主要内容包括：本发明提供一种碳掺杂的介孔石墨化氮化碳纳米球及其制备方法与应用。该碳掺杂的介孔石墨化氮化碳纳米球的制备方法包括：将生物质纤维进行预氧化处理使矿物酸表面生成羟基、羧基官能团；将预氧化处理后的生物质纤维与石墨化氮化碳的前驱体分散到溶剂中,进行溶剂热或水热处理得到产物A；将产物A进行焙烧得到所述碳掺杂的介孔石墨化氮化碳纳米球。该碳掺杂的介孔石墨化氮化碳纳米球可应用于催化剂载体以及电极中。本发明采用先以预氧化生物质纤维与石墨化氮化碳前驱体混合经溶剂热或水热处理实现分散再进行焙烧的简易方法,制备出了一种孔径分布窄、具有极高的分散性和导电性的碳掺杂的介孔石墨化氮化碳纳米球。(The invention provides a carbon-doped mesoporous graphitized carbon nitride nanosphere as well as a preparation method and application thereof. The preparation method of the carbon-doped mesoporous graphitized carbon nitride nanosphere comprises the following steps: carrying out pre-oxidation treatment on the biomass fibers to generate hydroxyl and carboxyl functional groups on the surface of mineral acid; dispersing the biomass fiber subjected to pre-oxidation treatment and a precursor of graphitized carbon nitride into a solvent, and carrying out solvothermal or hydrothermal treatment to obtain a product A; and roasting the product A to obtain the carbon-doped mesoporous graphitized carbon nitride nanosphere. The carbon-doped mesoporous graphitized carbon nitride nanospheres can be applied to catalyst carriers and electrodes. The invention adopts a simple method of mixing preoxidized biomass fibers and a graphitized carbon nitride precursor, realizing dispersion through solvothermal or hydrothermal treatment and then roasting to prepare the carbon-doped mesoporous graphitized carbon nitride nanospheres with narrow pore size distribution and extremely high dispersibility and conductivity.)

1. A preparation method of carbon-doped mesoporous graphitized carbon nitride nanospheres comprises the following steps:

1) carrying out pre-oxidation treatment on the biomass fibers to generate hydroxyl and carboxyl functional groups on the surface of mineral acid;

2) dispersing the biomass fiber subjected to pre-oxidation treatment and a precursor of graphitized carbon nitride into a solvent, and carrying out solvothermal or hydrothermal treatment to obtain a product A;

3) and roasting the product A to obtain the carbon-doped mesoporous graphitized carbon nitride nanosphere.

2. The production method according to claim 1,

the biomass fibers are provided by at least one of paper towels, wet tissues and carbon cloth; preferably, the biomass fibers are provided by a wet wipe; preferably, the biomass fibers are provided from waste material;

the precursor of the graphitized carbon nitride comprises at least one of thiourea, urea, dicyandiamide and melamine.

3. The production method according to claim 1,

the pre-oxidation treatment is carried out by using mineral acid; preferably, the mineral acid comprises at least one of hydrochloric acid, nitric acid and sulfuric acid; more preferably, the concentration of the mineral acid is no greater than 68%.

4. The preparation method according to claim 1, wherein the mass ratio of the biomass fibers subjected to the pre-oxidation treatment to the precursor of the graphitized carbon nitride is 0.01-0.2: 1.

5. The production method according to claim 1,

in step 2), the solvothermal and hydrothermal treatment is carried out at 80 to 160 ℃, preferably at 100 ℃;

in the step 2), the time of the solvothermal and hydrothermal treatment is 12-72h, preferably 24 h;

when the solvent heat treatment is used, the solvent used is a mixture of water and ethanol.

6. The production method according to claim 1,

in the step 3), the roasting temperature is above 400 ℃, preferably 400-700 ℃, and more preferably 500-600 ℃;

in step 3), the heating rate to the calcination temperature is 2-20 ℃/min.

7. The carbon-doped mesoporous graphitized carbon nitride nanosphere prepared by the preparation method of any one of claims 1 to 6;

preferably, the particle size of the carbon-doped mesoporous graphitized carbon nitride nanosphere is 88.3-141.5 nm;

preferably, the pore size is 2.0-4.0 nm;

preferably, the pore volume is 0.053-0.148cm³/g；

Preferably, the BET specific surface area is from 8.1 to 13.3m²/g；

Preferably, the specific surface area of the langmuir is 9.4 to 15.1m²/g。

8. Use of the carbon-doped mesoporous graphitized carbon nitride nanospheres of claim 7 in the preparation of a catalyst support;

preferably, the catalyst support is a catalyst support for electrocatalytic hydrogen evolution reactions.

9. A catalyst, wherein the carbon-doped mesoporous graphitized carbon nitride nanosphere of claim 7 is used as a support, and ruthenium is used as an active component.

10. The use of the carbon-doped mesoporous graphitized carbon nitride nanospheres of claim 7 in the preparation of an electrode.

Technical Field

The invention belongs to the technical field of doping modification of semiconductor materials, and relates to a carbon-doped mesoporous graphitized carbon nitride nanosphere as well as a preparation method and application thereof.

Background

Graphitized carbon nitride (g-C)₃N₄) As a non-metal organic polymer semiconductor, the non-metal organic polymer semiconductor has the characteristics of good chemical stability, easy preparation, low cost, moderate forbidden band width and the like, and is widely applied to the fields of environmental protection, organic synthesis, photocatalysis, catalyst carriers, electrochemistry and the like. However, the graphitized carbon nitride has the characteristics of easy aggregation, poor dispersibility, high resistance and the like, so that the further application of the graphitized carbon nitride in the fields of catalyst carriers and electrochemistry is severely limited. Therefore, it is important to research and develop a method for preparing graphitized carbon nitride having excellent mesopores, dispersibility and conductivity.

Currently, two methods are generally adopted for improving the dispersibility: graphitized carbon nitride with special morphology and the stripped graphitized carbon nitride nanosheet are prepared through a hard template. The former generally adopts a mesoporous molecular sieve, and the precursor of graphitized carbon nitride enters the pore channel of the molecular sieve, and the graphitized carbon nitride with a rod-like structure is obtained after solid-state conversion and template agent removal (Xiufang Chen, Young-Si Jun, Kazuhiro Takanabe, Kazuhiko Maeda, Kazunari Donen, Xianzhi Fu, Markus Antonietti, Xinchen WangA semiconductor host structure for a photonic crystal with visible light, Chemistry of Materials 2009.21(18): 4093-. Or the graphitized carbon nitride hollow sphere is prepared by combining a graphitized carbon nitride precursor with a silicon dioxide nanosphere through solid state conversion and template agent removal (Jianhua Sun, Jinshui Zhuang, Mingwen Zhuang, Markus Antonietti, Xianzhi Fu, Xinchen Wang. Bioinstiled held semiconducting nanoparticles, Nature Communications, 2012.1139). Although the method can prepare the graphitized carbon nitride with mesopores and good dispersibility, the method has the defects of long time and high cost due to a plurality of steps of hard template preparation, dipping, solid-state conversion, hard template removal and the like, and the template agent is required to be removed under HF acid or strong alkaline conditions, so the method is not suitable for large-scale production and application. The exfoliated graphitized nano-sheet is generally subjected to ultrasonic (Xiao one Zhang, Xiao Xie, Hui Wang, Jianjia Zhang, Bicai Pan, YiXie. enhanced photo reactive ultra-high molecular-phase C)₃N₄nanosheets deforming, Journal of the American Chemistry Society,135(1):18-21) or at high temperature (Ping Niu, Lili Zhang, Gang Liu, Hui-Ming Cheng, graphene-like carbon nitride passivation for improved photocatalytic activity, Advanced functional materials,2012.22(22):4763 4770), although mesoporous, well-dispersed graphitized carbon nitride nanoplates are obtained in the end, the former requires long-term ultrasonic treatment and the latter requires high-temperature graphitized carbon nitride etching. However, the stripped graphitized carbon nitride has the characteristic of reaggregation. Obviously, the method determines that the stripping graphitized carbon nitride nanosheet is not suitable for large-scale production, and the prepared graphitized carbon nitride is very limited in application.

Recently, embedding a carbon skeleton into a graphitized carbon nitride frame using a carbon doping method has proven to be an effective method. The carbon doping not only effectively hinders the aggregation of the graphitized carbon nitride, but also improves the conductive capability of the graphitized carbon nitride. Loading trimerization for soft templating agent, for example, using melamine cellular foam resinCyanamide, and calcining to obtain carbon-doped graphitized carbon nitride (Zaiwang ZHao, Yanjuan Sun, Fan Dong, Yuxin Zhang, HanZHao. template synthesis of carbon self-doped g-C)₃N₄with enhanced visual, airborne, and photocatalytic performance, RSC Advances,2015.5(49): 39549-. Or using kapok fiber to carry out hydrothermal or direct impregnation on the graphitized carbon nitride precursor, and obtaining tubular carbon-doped graphitized carbon nitride (Azuwa Mohamad, M.F.M.Zain, Lorna Jeffernyggu, Mohammad B.Kassim, Juhana Jaafr, Nor Aishah Saidina amine, Zul Adlan MohdHir, Mohamad Saufi.Enhance of visible light photocatalytic Hydrogen generation by bio-electrochemical-bonded graphite carbide, International journal of Hydrogen Energy,2019.44(26):13098 and 13105) after roasting.

However, the existing carbon-doped graphitized carbon nitride preparation methods have the defects of complicated steps, high cost, poor dispersibility, poor conductivity and the like.

Disclosure of Invention

The invention aims to provide a preparation method of carbon-doped mesoporous graphitized carbon nitride nanospheres. The preparation method is simple and convenient, and the prepared carbon-doped mesoporous graphitized carbon nitride nanospheres have good dispersion performance and excellent conductivity.

In order to achieve the above object, the present invention provides a method for preparing carbon-doped mesoporous graphitized carbon nitride nanospheres, wherein the method comprises the following steps:

1) carrying out pre-oxidation treatment on the biomass fibers to generate hydroxyl and carboxyl functional groups on the surface of mineral acid;

2) dispersing the biomass fiber subjected to pre-oxidation treatment and a precursor of graphitized carbon nitride into a solvent, and carrying out solvothermal or hydrothermal treatment to obtain a product A;

3) and roasting the product A to obtain the carbon-doped mesoporous graphitized carbon nitride nanosphere.

In the above preparation method, preferably, the biomass fiber is provided by at least one of a tissue, a wet tissue, and a carbon cloth; more preferably, the biomass fibers are provided by a wet wipe. Wherein the biomass fibers are preferably provided from waste materials, such as waste wet wipes, to provide the possibility of reuse of the waste biomass fibers. The main components of the wet tissue are non-woven fabrics, the reproducibility is good in the experimental process, and the wet tissue is more economical compared with a chemical carbon source with a complex synthetic process (such as a chemical carbon source with a complex preparation process of melamine porous resin, graphene oxide and the like) and a biological fiber with a complex composition (such as kapok), so that the whole industrial production chain is simplified.

In the above production method, preferably, the biomass fiber is washed with an organic solvent and an inorganic solvent before use, respectively; wherein, the organic solvent can be at least one of ethanol and acetone, but is not limited thereto; the inorganic solvent may be selected from water, but is not limited thereto.

In the above production method, preferably, the pre-oxidation treatment is performed using a mineral acid. More preferably, the mineral acid comprises at least one of hydrochloric acid, nitric acid and sulfuric acid. Further preferably, the concentration of the mineral acid is not more than 68%. The use of mineral acids enables the functionalization of specific surface structures of biomass fibers more than other types of oxidizing agents. In one embodiment, the pre-oxidation treatment is performed at 60 ℃ for 1 h.

In the above preparation method, the mass ratio of the biomass fiber after the pre-oxidation treatment to the precursor of the graphitized carbon nitride is preferably 0.01-0.2: 1.

In the above preparation method, preferably, the precursor of the graphitized carbon nitride includes at least one of thiourea, urea, dicyandiamide, melamine, and the like.

In the above preparation method, preferably, in step 2), the solvothermal and hydrothermal treatments are performed at 80 to 160 ℃, wherein the treatment time may be 12 to 72 hours; more preferably, the solvothermal and hydrothermal treatment is carried out at 100 ℃, wherein the treatment time may be 24 h.

In the above production method, preferably, in step 2), when the solvent heat treatment mode is used, the solvent used is a mixture of water and ethanol.

In the above preparation method, preferably, in step 2), the biomass fibers subjected to the pre-oxidation treatment and the precursor of the graphitized carbon nitride are dispersed in water, and subjected to hydrothermal treatment to obtain the product a.

In the above production method, preferably, the product a is dried before being calcined.

In the above preparation method, the temperature of the calcination is preferably 400 ℃ or more, more preferably 400-.

In the above preparation method, preferably, the calcination time is 1 to 6 hours.

In the above production method, preferably, the rate of temperature rise to the calcination temperature is 2 to 20 ℃/min.

In the above production method, preferably, the atmosphere of the calcination is an air atmosphere.

In a specific embodiment, the product A is heated to above 400 ℃ at the speed of 2-20 ℃/min in the air atmosphere and is kept at the constant temperature for 1-6h to realize roasting.

In another embodiment, the product A is calcined in an air atmosphere by raising the temperature to 550 ℃ at a rate of 5 ℃/min and maintaining the temperature for 1-6 h.

In the above preparation method, the calcined product generally needs to be cooled to room temperature.

The invention also provides the carbon-doped mesoporous graphitized carbon nitride nanosphere prepared by the preparation method of the carbon-doped mesoporous graphitized carbon nitride nanosphere.

The particle size of the carbon-doped mesoporous graphitized carbon nitride nanosphere is preferably 88.3-141.5 nm.

The pore diameter of the carbon-doped mesoporous graphitized carbon nitride nanosphere is preferably 2.0-4.0nm, and more preferably 2.5 nm.

The preferred pore volume of the carbon-doped mesoporous graphitized carbon nitride nanosphere is 0.053-0.148cm³G, more preferably 0.148cm³/g。

The BET specific surface area of the carbon-doped mesoporous graphitized carbon nitride nanosphere is preferably 8.1-13.3m²(ii) g, more preferably 13.3m²/g。

The langmuir specific surface area of the carbon-doped mesoporous graphitized carbon nitride nanosphere is preferably 9.4-15.1m²A ratio of 15.1 m/g is more preferable²/g。

The invention also provides an application of the carbon-doped mesoporous graphitized carbon nitride nanosphere in preparation of a catalyst carrier. In particular to the preparation of catalyst carrier as catalyst carrier material.

In the above application, preferably, the catalyst support is a catalyst support used in an electrocatalytic hydrogen evolution reaction.

The invention also provides a catalyst, wherein the catalyst takes the carbon-doped mesoporous graphitized carbon nitride nanosphere as a carrier and takes ruthenium as an active component. The catalyst is suitable for electrocatalytic hydrogen evolution reaction.

The invention also provides an application of the carbon-doped mesoporous graphitized carbon nitride nanosphere in preparing an electrode. The material can be used for preparing electrodes particularly as an electrode material.

The carbon-doped mesoporous graphitized carbon nitride nanospheres provided by the invention are added into a ruthenium salt solution to be dipped and thermally treated to prepare the carbon-doped mesoporous graphitized carbon nitride nanospheres (Ru/mpg-C) with monoatomic ruthenium dispersed therein₃N₄Catalyst of/CNS) i.e. the catalysts described above.

According to the preparation method provided by the invention, the surface of the biomass fiber is provided with functional groups such as hydroxyl, carboxyl and the like through pre-oxidation treatment; then combining the precursor of the graphitized carbon nitride with carboxyl and hydroxyl on the surface of the biomass fiber after oxidation pretreatment to uniformly disperse the precursor on the surface of the fiber; performing subsequent solvothermal or hydrothermal reinforcement on the combination of the graphitized carbon nitride precursor and the surface functional groups of the pre-oxidized fibers; and then carrying out subsequent roasting, wherein in the roasting process, the precursor of the graphitized carbon nitride is combined with the surface of the biomass fiber after oxidation pretreatment through a chemical bond with strong binding force, so that carbon combined with the precursor of the graphitized carbon nitride is retained to form the carbon-doped graphitized carbon nitride nanosphere.

The preparation method of the carbon-doped mesoporous graphitized carbon nitride nanosphere provided by the invention combines the functional groups such as carboxyl and hydroxyl on the surface of the graphitized carbon nitride precursor and the preoxidized fiber to generate stronger acting force by combining the preoxidation with the solvothermal or hydrothermal method for the first time, and then removes most of carbon, retains part of carbon and carries out solid-state conversion by roasting, thereby achieving the purpose of carbon doping, and forming a spherical shape under the action of temperature and surface Gibbs free energy.

According to the technical scheme provided by the invention, biomass fibers are used as a dispersing agent and a carbon source for doping, the biomass fibers are mixed with a graphitized carbon nitride precursor after being pre-oxidized, and the carbon-doped mesoporous graphitized carbon nitride nanospheres can be obtained by roasting after solvothermal or hydrothermal treatment. According to the invention, a hard template is not used, and carbon, nitrogen and sulfur elements are uniformly dispersed in the nanospheres during high-temperature roasting, and in-situ solid state conversion is carried out, so that the obtained carbon-doped mesoporous graphitized carbon nitride nanospheres have extremely high conductivity and dispersibility.

The carbon-doped graphitized carbon nitride nanosphere provided by the invention has the following substantial advantages and characteristics:

1. the carbon-doped graphitized carbon nitride nanosphere provided by the invention has excellent dispersibility and conductivity and a certain mesoporous structure; the conductivity of the carbon-doped graphitized carbon nitride nanosphere is obviously superior to that of the existing most carbon-doped graphitized carbon nitride nanospheres, and the carbon-doped graphitized carbon nitride nanospheres can be dispersed uniformly by ultrasonic within a very short time; compared with pure graphitized carbon nitride, the carbon-doped graphitized carbon nitride nanosphere has more excellent electrocatalytic hydrogen evolution activity.

2. The invention adopts the biomass fiber as the dispersant of the graphitized carbon nitride precursor and the carbon source for doping, has no toxicity, small influence on the environment, low cost, easy practical application and good environmental protection benefit.

3. The carbon-doped graphitized carbon nitride nanospheres provided by the invention have excellent performance as a catalyst carrier and an electrode material, simple process equipment, low cost, cleanness, no pollution and very high application value and commercial value.

4. The catalyst provided by the invention has lower overpotential and lower Tafel slope in the electrocatalytic hydrogen evolution reaction, and the performance of the catalyst is superior to that of a catalyst formed by loading ruthenium on a graphitized carbon nitride carrier; in a preferred embodiment, H is used at a concentration of 0.5M₂SO₄Solution at a current density of 10mV/cm²The overpotential was only 118mV, and the Tafel slope was 65 mV/dec.

5. According to the preparation method provided by the invention, the graphitized carbon nitride precursor is combined with functional groups such as carboxyl and hydroxyl on the surface of the pre-oxidized fiber to generate a strong acting force by combining the pre-oxidation with the solvothermal or hydrothermal method, and the graphitized carbon nitride precursor is effectively prevented from crystallizing on other places except the fiber in the subsequent recrystallization process, so that the graphitized carbon nitride precursor is crystallized only on the fiber.

In a word, the technical scheme provided by the invention adopts a simple method of dispersing and then roasting to prepare the carbon-doped mesoporous graphitized carbon nitride nanosphere, the method is low in preparation cost, simple in operation process and mild in condition, the target product is narrow in pore size distribution and extremely high in dispersibility and conductivity, is suitable for being used as a catalyst carrier, an electrode material and the like, can be used for constructing various heterogeneous structures, and has high application value and commercial value in the fields of catalyst carriers, electrolytic water hydrogen production, photocatalysis (such as photocatalytic degradation of organic pollutants, photocatalytic water hydrogen production and the like), and good application prospect.

Drawings

Fig. 1A and 1B are XRD spectra of the carbon-doped mesoporous graphitized carbon nitride nanosphere provided in example 1.

Fig. 2A is an SEM image of carbon-doped mesoporous graphitized carbon nitride nanosphere provided in example 1 at 20000 times magnification.

Fig. 2B is an SEM image of the carbon-doped mesoporous graphitized carbon nitride nanosphere provided in example 1 at 40000 times magnification.

Fig. 3A and 3B are TEM images of the carbon-doped mesoporous graphitized carbon nitride nanospheres provided in example 1.

Fig. 4A is a TEM image of the carbon-doped mesoporous graphitized carbon nitride nanosphere provided in example 1 under a dark field.

Fig. 4B is a surface distribution diagram of the C element in the EDX element distribution diagram result of the carbon-doped mesoporous graphitized carbon nitride nanosphere provided in example 1.

Fig. 4C is a surface distribution diagram of N element in the EDX element distribution diagram result of the carbon-doped mesoporous graphitized carbon nitride nanosphere provided in example 1.

Fig. 4D is a surface distribution diagram of S element in the EDX element distribution diagram result of the carbon-doped mesoporous graphitized carbon nitride nanosphere provided in example 1.

FIG. 5A is a diagram of N of the carbon-doped mesoporous graphitized carbon nitride nanosphere provided in example 1₂Adsorption/desorption isotherm plot.

Fig. 5B is a pore size distribution graph of the carbon-doped mesoporous graphitized carbon nitride nanosphere provided in example 1.

Fig. 6 is a polarization curve diagram of the carbon-doped mesoporous graphitized carbon nitride nanosphere provided in example 1 and the graphitized carbon nitride nanosphere provided in comparative example 1.

FIG. 7 is Tafel plot of carbon-doped mesoporous graphitized carbon nitride nanospheres provided in example 1 and graphitized carbon nitride nanospheres provided in comparative example 1

Fig. 8 is an ac impedance graph of the carbon-doped mesoporous graphitized carbon nitride nanosphere provided in example 1 and the graphitized carbon nitride nanosphere provided in comparative example 1.

FIG. 9 shows Ru/mpg-C provided in example 4₃N₄Polarization plot for/cNS.

FIG. 10 provides Ru/mpg-C from example 4₃N₄Tafel plot for/C NS.

FIGS. 11A and 11B show Ru/mpg-C provided in example 4₃N₄TEM image of/C NS.

FIG. 12 provides Ru/mpg-C from example 4₃N₄The Fourier transform of/C NS expands the X-ray absorption fine structure map.

Fig. 13A and 13B are optical microscope images of the product after the hydrothermal treatment in example 1.

Fig. 14A and 14B are optical microscope images of the product after the hydrothermal treatment in comparative example 2.

Detailed Description

The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.