阅读说明：本技术 六方形氮化硼/石墨烯平面异质结三维多孔碳材料及其制备方法与应用 (Hexagonal boron nitride/graphene planar heterojunction three-dimensional porous carbon material and preparation method and application thereof ) 是由 范孟孟 袁启昕 于 2021-09-28 设计创作，主要内容包括：本发明公开了一种六方形氮化硼/石墨烯平面异质结三维多孔碳材料及其制备方法与应用,材料的B或N的元素百分含量为2％-15％,孔径分布在10-30nm,以多孔h-BN、石墨烯前驱体、Ni纳米微球为原料,利用球磨过程,将多孔h-BN进行破碎,同时在机械化学作用下,使h-BN的边缘官能团与石墨烯前驱体形成共价键；同时加入Ni纳米微球,作为催化剂与模板剂,球磨后将混合材料进行压膜,最终通过退火过程及酸洗过程除去Ni颗粒,制备得到h-BN/石墨烯平面异质结丰富的多孔碳材料。可应用于电催化氧还原反应中。(The invention discloses a hexagonal boron nitride/graphene planar heterojunction three-dimensional porous carbon material and a preparation method and application thereof, wherein the percentage content of B or N element of the material is 2% -15%, the pore diameter is distributed at 10-30nm, porous h-BN, a graphene precursor and Ni nano microspheres are used as raw materials, the porous h-BN is crushed by utilizing the ball milling process, and simultaneously, under the mechanochemical action, the edge functional group of the h-BN and the graphene precursor form a covalent bond; and simultaneously adding Ni nano microspheres as a catalyst and a template agent, performing ball milling, then performing film pressing on the mixed material, and finally removing Ni particles through an annealing process and an acid washing process to prepare the porous carbon material with rich h-BN/graphene planar heterojunction. Can be applied to electrocatalytic oxygen reduction reaction.)

1. A hexagonal boron nitride/graphene planar heterojunction three-dimensional porous carbon material is characterized in that the percentage content of B or N is 2% -15%, the pore size is distributed at 10-30nm, porous h-BN, a graphene precursor and Ni nano microspheres are used as raw materials, the porous h-BN is crushed by utilizing a ball milling process, and meanwhile, under the mechanochemical action, edge functional groups of the h-BN and the graphene precursor form covalent bonds; simultaneously adding Ni nano microspheres serving as a catalyst and a template agent, performing ball milling, then performing film pressing on the mixed material, and finally removing Ni particles through an annealing process and an acid washing process to prepare the porous carbon material rich in h-BN/graphene planar heterojunction, wherein the graphene precursor is a porous carbon material containing-OH and-NH₂The precursor of (1).

2. The hexagonal boron nitride/graphene planar heterojunction three-dimensional porous carbon material of claim 1, wherein the graphene precursor is any one of chitosan, glucose, amino acid and melamine, the deacetylation degree is not less than 95%, and the viscosity is 100-200 mpa.s.

3. The method for preparing the hexagonal boron nitride/graphene planar heterojunction three-dimensional porous carbon material according to claim 1 or 2, characterized in that porous h-BN, a graphene precursor and Ni nano microspheres are used as raw materials, the porous h-BN is crushed by a ball milling process, and simultaneously, under the mechanochemical action, an edge functional group of the h-BN and the graphene precursor form a covalent bond; and simultaneously adding Ni nano microspheres as a catalyst and a template agent, performing ball milling, then performing film pressing on the mixed material, and finally removing Ni particles through an annealing process and an acid washing process to prepare the porous carbon material with rich h-BN/graphene planar heterojunction.

4. The method for preparing the hexagonal boron nitride/graphene planar heterojunction three-dimensional porous carbon material according to claim 3, wherein the specific surface area of the porous h-BN is 500-600m²g^-1The pore size distribution is 10-30 nm.

5. The method for preparing the hexagonal boron nitride/graphene planar heterojunction three-dimensional porous carbon material according to claim 3, wherein the addition mass of the porous h-BN accounts for 0.8-6% of the graphene precursor.

6. The method for preparing the hexagonal boron nitride/graphene planar heterojunction three-dimensional porous carbon material according to claim 3, wherein the addition amount of the Ni microspheres accounts for 20-60% of the mass of the graphene precursor.

7. The method of preparing hexagonal boron nitride/graphene planar heterojunction three-dimensional porous carbon material according to claim 3The method is characterized in that the annealing process is carried out in N₂Under the condition, the temperature rise speed is 10 ℃/min, the temperature rises to 900 ℃ and 1100 ℃, and the annealing is carried out for 2-4 h.

8. The method for preparing the hexagonal boron nitride/graphene planar heterojunction three-dimensional porous carbon material according to claim 3, wherein the tabletting pressure is 10-20Mpa and the time is 10-20 min.

9. The method for preparing hexagonal boron nitride/graphene planar heterojunction three-dimensional porous carbon material as claimed in claim 3, wherein the effective ball milling time during ball milling is 5-12h, the revolution speed is 500-; during ball milling, certain amount of ball milling beads of 5mm and 10mm are added.

10. The use of hexagonal boron nitride/graphene planar heterojunction three-dimensional porous carbon material according to claim 1 or 2 in electrocatalytic oxygen reduction reactions.

The technical field is as follows:

the invention relates to a hexagonal boron nitride (h-BN)/graphene heterojunction three-dimensional porous carbon material, a preparation method and an electrocatalysis application thereof.

Background art:

the h-BN and the graphene have high structural similarity and electrochemical properties with huge difference. For example, h-BN has a wide band gap structure, no conductivity; and the graphene has a zero band gap structure and high conductivity. The similarity and the difference of the h-BN and the graphene enable the h-BN to become a good doping agent for modifying the electrochemical property of the graphene and enabling the graphene to show new electrochemical performance, particularly electrocatalysis performance. The conventional h-BN/graphene planar heterojunction is a typical two-dimensional structure, the preparation method of the conventional h-BN/graphene planar heterojunction is mainly completed by a complex Chemical Vapor Deposition (CVD) method, the yield of materials and the content of the heterojunction are low, and the research and the application of the heterojunction in the fields of electrocatalysis and the like are limited. Therefore, it is necessary to explore a new method for realizing the construction of the rich heterojunction and the modification and application of the heterojunction to the graphene.

At present, patents for constructing two-dimensional h-BN/graphene planar heterojunction are reported, for example, in a patent (patent application number: 2017111130962) published by the inventor, a preparation method of the h-BN/graphene planar heterojunction is disclosed, firstly, a nickel layer with the thickness of nanometer level is deposited on the surface of a copper foil by a mask with a prefabricated pattern; secondly, placing the obtained copper foil substrate in a tube furnace, and uninterruptedly and sequentially depositing graphene and h-BN by a chemical vapor deposition method; and finally, controlling the cooling speed to cool the tube furnace to room temperature. According to the method, on the basis of the growth of a chemical vapor deposition method, the growth mechanism of graphene on the surfaces of copper and copper-nickel alloy is different, under a specific growth condition, the graphene only grows on the surface of the copper, and h-BN grows on the surface of the alloy which is not covered with the graphene, so that the h-BN/graphene planar heterojunction with the prefabricated pattern is prepared by only one chemical vapor deposition step. The preparation process of the method usually needs complicated steps such as pre-patterning and the like, and the content and the yield of the heterojunction are low, so that the heterojunction prepared by the method can only be used for constructing a microelectronic device and researching the basic physical properties of the heterojunction.

At present, a plurality of h-BN/graphene planar heterojunctions are disclosed, and mainly two-dimensional heterojunctions are constructed by a CVD method. In addition, there is a literature report on the reaction of-NH₂Modifying graphene quantum dots as doping precursors, mixing the doping precursors with a growth precursor of h-BN, and then growing the h-BN at the edge of the graphene quantum dots through high-temperature treatment, thereby constructing the h-BN/graphene planar heterojunction. The method has low heterojunction content and quality due to no metal catalyst.

At present, the construction of the h-BN/porous carbon composite material is also reported in documents. The porous carbon/h-BN composite material is finally formed by mainly carrying out physical mixing on h-BN and a porous carbon precursor and then carrying out high-temperature annealing. The method finally forms the amorphous carbon and h-BN composite material with less heterojunction due to the lack of effective growth sites and metal catalysts.

Disclosure of Invention

The invention aims to provide a three-dimensional porous carbon material with rich h-BN/graphene planar heterojunction and a preparation method thereof. The method comprises the steps of crushing porous h-BN by using a ball milling process, and forming covalent bonds between edge functional groups of the h-BN and graphene precursors under the mechanochemical action; meanwhile, Ni nano-microspheres are added to serve as a catalyst and a template agent, and finally the porous carbon material with rich h-BN/graphene planar heterojunction is prepared through an annealing process and an acid washing process.

The technical scheme of the invention is as follows: a hexagonal boron nitride/graphene planar heterojunction three-dimensional porous carbon material comprises 2% -15% of B or N, the pore size is distributed in the range of 10-30nm, porous h-BN, a graphene precursor and Ni nano microspheres are used as raw materials, the porous h-BN is crushed by utilizing the ball milling process, and meanwhile, under the mechanochemical action, the edge functional groups of the h-BN and the graphene precursor form covalent bonds; simultaneously adding Ni nano microspheres serving as a catalyst and a template agent, performing ball milling, then performing film pressing on the mixed material, and finally removing Ni particles through an annealing process and an acid washing process to prepare the porous carbon material rich in h-BN/graphene planar heterojunction, wherein the graphene precursor contains-OH and-NH₂The precursor of (1).

The graphene precursor is any one of chitosan, glucose, amino acid and melamine, and the chitosan contains-OH and-NH₂The degree of deacetylation is more than or equal to 95 percent, and the viscosity is 100-200 mpa.s.

Taking porous h-BN, a graphene precursor and Ni nano microspheres as raw materials, crushing the porous h-BN by utilizing a ball milling process, and simultaneously forming covalent bonds between edge functional groups of the h-BN and the graphene precursor under the action of mechanochemistry; and simultaneously adding Ni nano microspheres as a catalyst and a template agent, performing ball milling, then performing film pressing on the mixed material, and finally removing Ni particles through an annealing process and an acid washing process to prepare the porous carbon material with rich h-BN/graphene planar heterojunction.

The specific surface area of the porous h-BN is 500-600m²g^-1The pore size distribution is 10-30 nm.

The addition mass of the porous h-BN accounts for 0.8-6% of that of the graphene precursor.

The addition amount of the Ni microspheres accounts for 20-60% of the mass of the graphene precursor.

Said annealing process is carried out in N₂Under the condition, the temperature rise speed is 10 ℃/min, the temperature rises to 900 ℃ and 1100 ℃, and the annealing is carried out for 2-4 h.

Tabletting under 10-20Mpa for 10-20 min.

The effective ball milling time during ball milling is 5-12h, the revolution speed is 500 plus 600rpm, and the mode is positive and negative alternate ball milling; during ball milling, certain amount of ball milling beads of 5mm and 10mm are added.

The hexagonal boron nitride/graphene planar heterojunction three-dimensional porous carbon material is applied to catalysis in electrocatalytic oxygen reduction reaction.

Has the advantages that:

1. the preparation method is simple, the heterojunction does not need to be provided with a prefabricated pattern, the h-BN is uniformly distributed and has uniform size, and the formed heterojunction is rich.

2. By a ball milling method, the H-BN edge and the graphene precursor form a B-C, N-C covalent bond by using a mechanochemical action, and the formation of a planar heterojunction is promoted.

3. The h-BN/graphene heterojunction porous carbon composite material electrocatalysis O₂Reduction to produce H₂O₂The average selectivity of the catalyst is 58-83%, and the catalytic activity (expressed by the magnitude of the loop current in the rotating disc test) is 0.26-0.39 mA. The initial potential was 0.64V-0.79V vs. standard hydrogen electrode (@ loop current ═ 0.05 mA). The electrochemical regulation and control effect of the heterojunction on the graphene is regulated and controlled by changing the content of h-BN, and the method is applied to catalytic oxygen reduction reaction. When the content of H-BN is 4%, the H-BN/graphene planar heterojunction composite material shows the optimal catalytic oxygen reduction to generate H₂O₂Performance, including catalytic selectivity up to 80% or more, maximum H₂O₂The yield was 0.39mA (expressed by the loop current measured by rotating the ring disk electrode), the initial potential was 0.79V at the highest relative to the standard hydrogen electrode (@ loop current ═ 0.05mA), and the catalytic performance was maintained above 84% for 10 h.

Drawings

FIG. 1 h-BN/graphene heterojunction porous carbon material high-resolution transmission electron microscope image and corresponding B, N element mapping image. The positions of the two materials and the formation region of the heterojunction can be observed in the electron micrograph. Mapping illustrates that h-BN is uniformly distributed in the carbon material.

FIG. 2 shows an X-ray diffraction spectrogram of the h-BN/graphene heterojunction porous carbon material, when Ni microspheres are added, the crystallinity of the composite material can be improved, and therefore more heterojunctions are formed.

FIG. 3 shows that the composite material with different h-BN doping amounts can be used for electrocatalysis O₂Reduction to produce H₂O₂And (4) performance. With the increase of the doping amount of the porous h-BN, the catalytic activity is increased firstly and then reduced; wherein the composite material shows the optimal catalytic performance when the doping amount is 4 percent, and H₂O₂Selectivity was 83%, with an initial potential of 0.79V versus a standard hydrogen electrode.

The specific implementation mode is as follows:

according to Advanced Energy materials,2014, 4, 1301525, porous h-BN is prepared by dissolving boric acid and dicyandiamide in hot water according to a molar ratio of 1:3, heating to completely evaporate water, grinding the obtained solid, and adding NH₃(50sccm)Then, annealing is carried out at 10 ℃/min and 800 ℃ for 3 h. And finally obtaining porous h-BN for constructing the heterojunction. Specific surface area of 500-600m²g^-1The pore size distribution is 10-30 nm.

The medicines used in the preparation process are all analytically pure. The pharmaceutical manufacturer is Shanghai chemical reagents, Allantin reagents, Inc.

A preparation method of an h-BN/graphene planar heterojunction porous carbon material comprises the steps of crushing porous h-BN by utilizing a ball milling process, and simultaneously forming covalent bonds between edge functional groups of the h-BN and a graphene precursor (chitosan) under the action of mechanochemistry; meanwhile, Ni nano-microspheres are added to serve as a catalyst and a template agent, the mixed material is subjected to film pressing (10-15Mpa for 10-20min) after ball milling, and finally Ni particles are removed through an annealing process and an acid washing process to prepare the porous carbon material rich in h-BN/graphene planar heterojunction.

The specific surface area of the porous h-BN is 500-600m²g^-1The pore size distribution is 10-30 nm.

In the h-BN/graphene heterojunction porous material, the percentage content of B or N is 2-15%, and the pore size is distributed at 10-30 nm.

The addition mass ratio of the porous h-BN is 0.8-6% (relative to the chitosan).

The chitosan contains-OH and-NH₂The degree of deacetylation is more than or equal to 95 percent, and the viscosity is 100-200 mpa.s.

The addition amount of the Ni microspheres is 20-60% (relative to chitosan).

The ball milling method has the effective ball milling time of 5-12h, the revolution speed of 500-600rpm and the mode of positive and negative alternate ball milling (0.5h positive rotation, 0.8h stop and 0.5h reverse rotation). During ball milling, certain amount of ball milling beads of 5mm and 10mm are added.

And tabletting the product of the porous h-BN and the chitosan after ball milling, and keeping the pressure at 10-20Mpa for 10-20 min.

Said annealing process is carried out in N₂Under the condition, the temperature rise speed is 10 ℃/min, the temperature rises to 900 ℃ and 1100 ℃, and the annealing is carried out for 2-4 h.

The h-BN/graphene planar heterojunction enriches the catalytic application of the three-dimensional porous carbon material in the electrocatalytic oxygen reduction reaction.

The h-BN/graphene heterojunction porous carbon composite material electrocatalysis O₂Reduction to produce H₂O₂The average selectivity of the catalyst is 58-83%, and the catalytic activity (expressed by the magnitude of the loop current in the rotating disc test) is 0.26-0.39 mA. The initial potential was 0.64V-0.79V vs. standard hydrogen electrode (@ loop current ═ 0.05 mA).

Example 1: the addition amount of the porous h-BN in the h-BN/graphene heterojunction porous carbon composite material is 0.8 percent

20mg of porous h-BN, 2.5g of chitosan and 1g of Ni microspheres are added into a 150ml ball milling tank, a certain amount of ball milling beads (10mm 5 particles and 5mm 40 particles) are added, then the ball milling tank is placed into a ball mill, the ball milling speed is revolution at 550rpm, the mode is forward rotation for 0.5h, cooling is carried out for 0.8h, then reverse rotation is carried out for 0.5h, and the effective ball milling time is 5 h. Then tabletting the mixed material by a tabletting machine, and keeping the pressure at 10MPa for 10 min. And annealing the pressing sheet material under the conditions of 900 ℃ for 2 hours. Finally, Ni powder in the material is removed by ultrasonic through 0.1M HCl solution, and the material is dried for 6 hours under the vacuum condition of 50 ℃. H of the prepared composite₂O₂The average selectivity was 70%, the loop current was 0.3mA, and the initial potential was 0.65V.

Example 2: the addition amount of the porous h-BN in the h-BN/graphene heterojunction porous carbon composite material is 2 percent

50mg of porous h-BN, 2.5g of chitosan and 1g of Ni microspheres are added into a 150ml ball milling tank, and a certain amount of ball milling beads (10mm 5, 5mm 40) are added. Then placing the mixture into a ball mill, wherein the ball milling speed is revolution at 550rpm, the mode is positive rotation for 0.5h, cooling is carried out for 0.8h, then reverse rotation is carried out for 0.5h, and the effective ball milling time is 10 h. Then tabletting the mixed material by a tabletting machine, and keeping the pressure at 10MPa for 10 min. And annealing the pressing sheet material at 900 ℃ for 3 h. Finally, Ni powder in the material is removed by ultrasonic through 0.1M HCl solution, and the material is dried for 6 hours under the vacuum condition of 50 ℃. The average selectivity of H2O2 for the prepared composite material was 83%, the loop current was 0.39mA, and the initial potential was 0.76V.

Example 3: the addition amount of the porous h-BN in the h-BN/graphene heterojunction porous carbon composite material is 4 percent

100mg of porous h-BN, 2.5g of chitosan and 1g of Ni microspheres are added into a 150ml ball milling tank, and a certain amount of ball milling beads (10mm 5, 5mm 40) are added. Then placing the mixture into a ball mill, wherein the ball milling speed is revolution at 550rpm, the mode is positive rotation for 0.5h, cooling is carried out for 0.8h, then reverse rotation is carried out for 0.5h, and the effective ball milling time is 12 h. Then, the mixed material is tabletted by a tablet machine, and the mixed material is kept for 20min under the pressure of 15 MPa. And annealing the pressing sheet material at 900 ℃ for 3 h. Finally, Ni powder in the material is removed by ultrasonic through 0.1M HCl solution, and the material is dried for 6 hours under the vacuum condition of 50 ℃. The average selectivity of H2O2 of the prepared composite material was 82%, the loop current was 0.38mA, and the initial potential was 0.79V.

Example 4: h-BN/graphene heterojunction porous carbon composite material (Melamine as carbon precursor)

100mg of porous h-BN, 2.5g of melamine and 1g of Ni microspheres are added into a 150ml ball milling tank, and a certain amount of ball milling beads (10mm 5, 5mm 40) are added. Then placing the mixture into a ball mill, wherein the ball milling speed is revolution at 550rpm, the mode is positive rotation for 0.5h, cooling is carried out for 0.8h, then reverse rotation is carried out for 0.5h, and the effective ball milling time is 12 h. Then, the mixed material is tabletted by a tablet machine, and the mixed material is kept for 20min under the pressure of 15 MPa. And annealing the pressing sheet material at 900 ℃ for 3 h. Finally, Ni powder in the material is removed by ultrasonic through 0.1M HCl solution, and the material is dried for 6 hours under the vacuum condition of 50 ℃.

Example 5: h-BN/graphene heterojunction porous carbon composite material (glucose/alanine as carbon precursor)

100mg of porous h-BN, 1.0g of glucose, 1.5g of alanine and 1g of Ni microspheres are added into a 150ml ball milling tank, and a certain amount of ball milling beads (10mm 5, 5mm 40) are added. Then placing the mixture into a ball mill, wherein the ball milling speed is revolution at 550rpm, the mode is positive rotation for 0.5h, cooling is carried out for 0.8h, then reverse rotation is carried out for 0.5h, and the effective ball milling time is 12 h. Then, the mixed material is tabletted by a tablet machine, and the mixed material is kept for 20min under the pressure of 15 MPa. And annealing the pressing sheet material at 900 ℃ for 3 h. Finally, Ni powder in the material is removed by ultrasonic through 0.1M HCl solution, and the material is dried for 6 hours under the vacuum condition of 50 ℃.

Comparative example 1: without addition of porous h-BN

2.5g of chitosan and 1g of Ni microspheres are added into a 150ml ball milling tank, and a certain amount of ball milling beads (10mm 5, 5mm 40) are added. Then placing the mixture into a ball mill, wherein the ball milling speed is revolution at 550rpm, the mode is positive rotation for 0.5h, cooling is carried out for 0.8h, then reverse rotation is carried out for 0.5h, and the effective ball milling time is 12 h. Then, the mixed material is tabletted by a tablet machine, and the mixed material is kept for 20min under the pressure of 15 MPa. And annealing the pressing sheet material at 900 ℃ for 3 h. Finally, Ni powder in the material is removed by ultrasonic through 0.1M HCl solution, and the material is dried for 6 hours under the vacuum condition of 50 ℃. The average selectivity of H2O2 for the prepared composite material was 84%, the loop current was 0.22mA, and the initial potential was 0.64V.

Comparative example 2: without Ni microspheres

100mg of porous h-BN, 2.5g of chitosan and 1g of Ni microspheres are added into a 150ml ball milling tank, and a certain amount of ball milling beads (10mm 5, 5mm 40) are added. Then placing the mixture into a ball mill, wherein the ball milling speed is revolution at 550rpm, the mode is positive rotation for 0.5h, cooling is carried out for 0.8h, then reverse rotation is carried out for 0.5h, and the effective ball milling time is 12 h. Then, the mixed material is tabletted by a tablet machine, and the mixed material is kept for 20min under the pressure of 15 MPa. And annealing the pressing sheet material at 900 ℃ for 3 h. Finally, Ni powder in the material is removed by ultrasonic through 0.1M HCl solution, and the material is dried for 6 hours under the vacuum condition of 50 ℃. The average selectivity of H2O2 of the prepared composite material was 53%, the loop current was 0.2mA, and the initial potential was 0.65V.