Cobalt / black phosphorus quantum dot catalyst supported on three-dimensional carbon network, preparation method and application

Abstract

The present invention belongs to the field of nanomaterials and electrocatalytic technology, and discloses a three-dimensional carbon network supported cobalt / black phosphorus quantum dot catalyst and a preparation method thereof, comprising the following steps: respectively weighing zinc salt and cobalt salt, adding them into 2-methylimidazole and an organic solvent, and mixing and stirring; quickly mixing the two obtained solutions and heating them to react to obtain a metal precursor; placing the dried precursor in a high-temperature tubular furnace under an argon atmosphere and heating to obtain cobalt metal particles supported by a three-dimensional carbon network; placing bulk black phosphorus in a DMF solution, performing ultrasonic treatment and centrifuging twice, and taking the upper light yellow clear solution; placing the cobalt metal particles supported by the three-dimensional carbon network in the yellow clear solution of black phosphorus, stirring evenly, and then placing them in a reaction kettle for heating reaction to finally obtain a three-dimensional carbon network supported transition metal / black phosphorus quantum dot heterojunction. The prepared catalyst promotes the electron transfer between the metal and the semiconductor through the Schottky heterojunction, presenting high electrocatalytic activity and good stability.

Description

Technical Field

[0001] The present invention belongs to the field of nanomaterials and electrocatalytic water splitting catalysts, and particularly relates to a three-dimensional carbon network supported cobalt / black phosphorus quantum dot catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] In order to solve the increasingly severe environmental and energy problems, the development of clean, renewable, and low-cost sustainable energy has become a research hotspot. Among all potential candidates, hydrogen is considered an ideal clean energy carrier because it can generate energy without emitting harmful chemicals. Electrochemical overall water splitting is a very promising technology for hydrogen production at present. As is well known, platinum-based materials are considered the best catalysts for the hydrogen evolution reaction (HER); while RuO 2 and IrO 2 are considered the best catalysts for the oxygen evolution reaction (OER) in water electrolysis. However, the high cost and low reserves of noble metals limit their large-scale industrial applications. In addition, HER and OER catalysts require different instruments and synthesis methods, which is not conducive to cost savings. Therefore, the exploration of earth-abundant electrocatalysts with low overpotential and long-term stability is a current research hotspot.

[0003] Transition metals have become the most promising substitutes for noble metal-based catalysts due to their numerous types, rich electron layer structures, and variable valence states. Using porous carbon materials with low price, high chemical stability, good electrical conductivity, and large specific surface area as carriers can improve the stability of transition metal materials. By constructing a metal-semiconductor Schottky junction and utilizing the difference in their work functions, the formation of a curved energy band structure at the metal-semiconductor contact interface is achieved, thereby improving the electrocatalytic performance. Among many semiconductor materials, layered black phosphorus (BP), as a two-dimensional non-metallic material with high electrical conductivity, has an adjustable direct bandgap, unique anisotropy, strong optical absorption, and high carrier mobility. However, the poor stability of BP catalysts during the OER process hinders their practical applications.

[0004] At present, there are certain difficulties in preparing transition metal-doped carbon materials. It is often necessary to select a suitable transition metal-containing precursor, and the processes and methods for preparing transition metal-doped carbon materials are complex and costly. Secondly, there is no report on the preparation and application of a metal cobalt / black phosphorus quantum dot Schottky heterojunction grown on a three-dimensional carbon material in electrocatalysis. Summary of the Invention

[0005] The purpose of the present invention is to provide a three-dimensional carbon network supported cobalt / black phosphorus quantum dot catalyst, a preparation method thereof, and an application thereof, which solves the problems of high electrocatalytic overpotential of current transition metal catalysts and poor electrocatalytic performance of black phosphorus.

[0006] The present invention is realized through the following technical solutions:

[0007] A preparation method of a cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network includes the following processes:

[0008] Weigh zinc salt and 2-methylimidazole, dissolve them in an organic solvent, mix and stir to obtain a zinc ion solution;

[0009] Weigh cobalt salt and 2-methylimidazole, dissolve them in an organic solvent, mix and stir to obtain a cobalt ion solution;

[0010] Mix and stir the zinc ion solution and the cobalt ion solution. After stirring evenly, heat and react at 100-140 °C for 6-24 h, wash and dry to obtain a metal-organic framework precursor;

[0011] Under a protective atmosphere, heat the metal-organic framework precursor to 800 °C and keep it warm for 3-5 h to obtain cobalt metal particles supported on a three-dimensional carbon network;

[0012] Place massive black phosphorus in a DMF solution and ultrasonicate for 1-3 h. After standing and centrifuging, take the upper light yellow clear black phosphorus solution;

[0013] Place the cobalt metal particles supported on the three-dimensional carbon network in the black phosphorus solution. After stirring evenly, heat and react at 180-220 °C for 6-24 h, wash and dry to obtain a cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network.

[0014] Furthermore, the concentration of the zinc salt in the organic solvent is 0.1 mol / L - 0.3 mol / L;

[0015] The concentration of the cobalt salt in the organic solvent is 0.1 mol / L - 0.3 mol / L.

[0016] Furthermore, the volume ratio of the zinc ion solution to the cobalt ion solution is 1:1 - 1:3.

[0017] Furthermore, the concentration of the massive black phosphorus in the DMF solution is 0.001 - 1 g / L.

[0018] Furthermore, centrifuge twice. The first centrifugation is carried out at a rotation speed of 5000-10000 r / min for 5-10 min, and the precipitate is taken. The second centrifugation is carried out at a rotation speed of 13000-17000 r / min for 5-10 min.

[0019] The present invention also discloses a cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network prepared by the above preparation method. The carbon network of the cobalt / black phosphorus quantum dot catalyst supported on the three-dimensional carbon network is composed of nitrogen-doped porous carbon and carbon nanotubes and presents a dodecahedral morphology;

[0020] The carbon network is loaded with nano cobalt and black phosphorus quantum dots, and the nano cobalt and the black phosphorus quantum dots form a Schottky heterojunction.

[0021] Furthermore, the size of the nano cobalt particles is 2 - 5 nm, and the size of the black phosphorus quantum dots is 1 - 3 nm.

[0022] The present invention also discloses the application of the three - dimensional carbon network - supported cobalt / black phosphorus quantum dot catalyst as a catalyst material in the electrocatalytic hydrogen evolution reaction.

[0023] The present invention also discloses the application of the three - dimensional carbon network - supported cobalt / black phosphorus quantum dot catalyst as a catalyst material in the electrocatalytic oxygen evolution reaction.

[0024] The present invention also discloses the application of the three - dimensional carbon network - supported cobalt / black phosphorus quantum dot catalyst as a catalyst material in the electrocatalytic overall water splitting reaction.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] The present invention discloses a preparation method of a three - dimensional carbon network - supported cobalt / black phosphorus quantum dot catalyst. First, a zinc ion solution and a cobalt ion solution are mixed, and 2 - methylimidazole provides a carbon source. After heating and reacting, a metal - organic framework precursor is obtained; during the high - temperature calcination of the metal - organic framework precursor at 800 °C, cobalt ions first exist in the form of Co - N 4 , and then the Co - N bond gradually breaks to form cobalt nanoparticles and is uniformly dispersed on the carbon network; too high a calcination temperature will cause the nano cobalt particles to agglomerate and grow, while a decrease in the calcination temperature will reduce the graphitization degree of the precursor after carbonization. When calcined at 800 °C, zinc in the precursor will evaporate to form a porous - structure carbon, and the high catalytic activity of nano cobalt will form carbon nanotubes. The edges of the black phosphorus quantum dots after ultrasonic centrifugation have rich lone - pair electrons. Driven by the solvothermal method (heating and reacting at 180 - 220 °C for 6 - 24 h), the black phosphorus quantum dots are easily combined with nano cobalt to form a Schottky heterojunction. Due to the difference in their work functions, the electron transfer between the metal Co and the semiconductor BP in the heterojunction occurs. Interface electrons will spontaneously transfer from Co to BP, forming an internal electric field at the heterojunction interface, which can accelerate the charge transfer in the electrocatalytic reaction; due to the interface electron transfer, the electronic structure of BP is regulated, increasing its electrochemical activity and stability, making it exhibit good catalytic activity as an electrocatalytic overall water - splitting catalyst.

[0027] The present invention also discloses a three-dimensional carbon network supported cobalt / black phosphorus quantum dot catalyst prepared by the above preparation method. The carbon network mainly has a dodecahedral shape and is composed of nitrogen-doped porous carbon and carbon nanotubes. Nitrogen doping can improve the conductivity of the carbon network and anchor cobalt nanoparticles. Carbon nanotubes have more excellent conductive properties. This three-dimensional carbon network has a large specific surface area, which can effectively disperse the cobalt / black phosphorus quantum dot heterojunction and ensure its conductivity and electrocatalytic stability. The size of cobalt particles in the catalyst is 2-5 nm, and the size of black phosphorus quantum dots is 1-3 nm. The formed ultra-fine nanoheterojunction has a large specific surface area and abundant active sites, which is one of the main reasons for its excellent electrocatalytic performance. Description of the Drawings

[0028] Figure 1 SEM photograph of the three-dimensional carbon network supported cobalt / black phosphorus quantum dot catalyst prepared in Example 1 of the present invention;

[0029] Figure 2 SEM photograph of the three-dimensional carbon network supported cobalt / black phosphorus quantum dot catalyst prepared in Example 2 of the present invention;

[0030] Figure 3 SEM photograph of the three-dimensional carbon network supported cobalt / black phosphorus quantum dot catalyst prepared in Example 3 of the present invention;

[0031] Figure 4 TEM image of cobalt metal nanoparticles / black phosphorus quantum dots supported on the three-dimensional carbon network prepared in Example 1 of the present invention; Figure 4 a is the TEM image of cobalt metal nanoparticles / black phosphorus quantum dots supported on the three-dimensional carbon network, Figure 4 b is the high-resolution TEM photograph of the cobalt / black phosphorus quantum dot heterojunction;

[0032] Figure 5 TEM image of cobalt metal nanoparticles / black phosphorus quantum dots supported on the three-dimensional carbon network prepared in Example 4 of the present invention; Figure 5 a is the TEM image of cobalt metal nanoparticles / black phosphorus quantum dots supported on the three-dimensional carbon network; Figure 5 b- Figure 5 c is the high-resolution TEM photograph of the cobalt / black phosphorus quantum dot heterojunction;

[0033] Figure 6 LSV curve graph of the hydrogen evolution reaction of the cobalt metal nanoparticles / black phosphorus quantum dot heterojunction catalyst supported on the three-dimensional carbon network prepared in the present invention;

[0034] Figure 7 LSV curve graph of the oxygen evolution reaction of the cobalt metal nanoparticles / black phosphorus quantum dot heterojunction catalyst supported on the three-dimensional carbon network prepared in the present invention;

[0035] Figure 8 The LSV curve diagram of the overall water splitting of the cobalt metal nanoparticle / black phosphorus quantum dot heterojunction catalyst supported by the three-dimensional carbon network prepared by the present invention. Detailed implementation manners

[0036] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments.

[0037] The components described and illustrated in the accompanying drawings and embodiments of the present invention can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed present invention, but only represents a selected embodiment of the present invention. Based on the accompanying drawings and embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention.

[0038] It should be noted that the terms "comprising", "including" or any other variants are intended to cover non-exclusive inclusion, so that a process, element, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to the process, element, method, article or device.

[0039] The features and performance of the present invention are further described in detail in conjunction with the embodiments below.

[0040] Example 1

[0041] The present invention discloses a preparation method of a cobalt / black phosphorus quantum dot catalyst supported by a three-dimensional carbon network, including the following steps:

[0042] (1) Weigh 0.003 mol of zinc nitrate and 0.05 mol of 2-methylimidazole, dissolve them in 10 ml of methanol solution, mix and stir to obtain a zinc solution.

[0043] (2) Weigh 0.003 mol of cobalt nitrate and 0.05 mol of 2-methylimidazole, dissolve them in 10 ml of methanol solution, mix and stir to obtain a cobalt solution.

[0044] (3) Mix the two obtained solutions in a ratio of 1:1, stir evenly, place them in a reaction kettle, heat at 100 °C for 6 h, and wash and dry with methanol to obtain a metal-organic framework precursor.

[0045] (4) The dried metal-organic framework precursor was placed in a high-temperature tubular furnace filled with argon and heated to 800 °C at a heating rate of 1 °C / min and held for 3 h to obtain cobalt metal particles supported on a three-dimensional carbon network.

[0046] (5) Bulk black phosphorus was placed in a 50 ml DMF solution at a concentration of 0.2 g / L and sonicated for 1 h. It was centrifuged for the first time at a speed of 5000 r / min for 5 min, and the precipitate was taken. Then it was centrifuged for the second time at a speed of 13000 r / min for 5 min, and the upper light yellow clear black phosphorus solution was taken.

[0047] (6) The cobalt metal particles supported on the three-dimensional carbon network were placed in the yellow clear black phosphorus solution, stirred evenly, then placed in a reaction kettle and heated at 180 °C for 6 h, and washed and dried with DMF to obtain a cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network.

[0048] Figure 1 This is the SEM photograph of the cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network prepared in Example 1 of the present invention. It can be seen that the catalyst particles present a dodecahedral morphology.

[0049] Figure 4 a is the TEM image of cobalt metal nanoparticles / black phosphorus quantum dots supported on a three-dimensional carbon network. Carbon nanotubes and nitrogen-doped carbon can be seen. Figure 4 b is the high-resolution TEM photograph of the cobalt / black phosphorus quantum dot heterojunction; the size of the cobalt particles is about 3 nm, and the size of the black phosphorus quantum dots is about 2 nm. It is obvious to see the heterojunction interface between the cobalt particles and the black phosphorus quantum dots.

[0050] As Figure 6 shown, for the hydrogen evolution reaction of the cobalt / black phosphorus quantum dot heterojunction catalyst supported on a three-dimensional carbon network prepared in Example 1, the overpotential at 100 mA / cm 2 is 124 mV.

[0051] As Figure 7 shown, for the oxygen evolution reaction of the cobalt / black phosphorus quantum dot heterojunction catalyst supported on a three-dimensional carbon network prepared in Example 1, the overpotential at 100 mA / cm 2 is 370 mV.

[0052] As Figure 8 shown, for the overall water splitting reaction of the cobalt / black phosphorus quantum dot heterojunction catalyst supported on a three-dimensional carbon network prepared in Example 1, the voltage at 100 mA / cm 2 is 1.35 V.

[0053] In summary, it shows that the cobalt / black phosphorus quantum dot heterojunction catalyst supported on a three-dimensional carbon network prepared by the present invention has excellent electrocatalytic water splitting performance.

[0054] Example 2

[0055] The present invention discloses a preparation method of a cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network, comprising the following steps:

[0056] (1) Weigh 0.002 mol of zinc nitrate and 0.05 mol of 2-methylimidazole, dissolve them in 10 ml of methanol solution, and mix and stir to obtain a zinc solution;

[0057] (2) Weigh 0.002 mol of cobalt nitrate and 0.05 mol of 2-methylimidazole, dissolve them in 10 ml of methanol solution, and mix and stir to obtain a cobalt solution;

[0058] (3) Mix the two obtained solutions in a ratio of 1:2, stir evenly, place them in a reaction kettle, heat at 110 °C for 12 h, and wash and dry with methanol to obtain a metal-organic framework precursor;

[0059] (4) Place the dried metal-organic framework precursor in a high-temperature tubular furnace filled with argon, heat it at a heating rate of 3 °C / min to 800 °C, and keep it warm for 5 h to obtain cobalt metal particles supported on a three-dimensional carbon network;

[0060] (5) Place massive black phosphorus in 50 ml of DMF solution at a concentration of 0.001 g / L, ultrasonicate for 1 h, centrifuge for the first time at a speed of 7000 r / min for 8 min, take the precipitate, and centrifuge for the second time at a speed of 15000 r / min for 8 min;

[0061] (6) Place the cobalt metal particles supported on the three-dimensional carbon network in the yellow clear solution of black phosphorus, stir evenly, place them in a reaction kettle, heat at 200 °C for 9 h, and wash and dry with DMF to obtain a three-dimensional carbon network supported cobalt / black phosphorus quantum dot heterojunction.

[0062] Figure 2 This is the SEM photograph of the cobalt / black phosphorus quantum dot catalyst supported on the three-dimensional carbon network prepared in Example 2 of the present invention. It can be seen that the catalyst particles present a dodecahedral morphology.

[0063] Example 3

[0064] The present invention discloses a cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network and its preparation method, comprising the following steps:

[0065] (1) Weigh 0.001 mol of zinc nitrate and 0.05 mol of 2-methylimidazole, dissolve them in 10 ml of methanol solution, and mix and stir;

[0066] (2) Weigh 0.001 mol of cobalt nitrate and 0.05 mol of 2-methylimidazole, dissolve them in 10 ml of methanol solution, and mix and stir;

[0067] (3) Mix the two obtained solutions at a ratio of 1:3 and stir them evenly. Then place them in a reaction kettle and heat at 130 °C for 24 h, and wash and dry with methanol to obtain a metal precursor;

[0068] (4) Place the dried precursor in a high-temperature tube furnace filled with argon and heat it to 800 °C at a heating rate of 5 °C / min and hold for 4 h to obtain cobalt metal particles supported on a three-dimensional carbon network.

[0069] (5) Place bulk black phosphorus in a 50 ml DMF solution at a concentration of 1 g / L and ultrasonicate for 1 h. Centrifuge for the first time at a speed of 10000 r / min for 10 min, and take the precipitate. Centrifuge for the second time at a speed of 17000 r / min for 10 min;

[0070] (6) Place the cobalt metal particles supported on the three-dimensional carbon network in the yellow clear solution of black phosphorus, stir evenly, then place them in a reaction kettle and heat at 220 °C for 12 h, and wash and dry with DMF to obtain a three-dimensional carbon network supported transition metal / black phosphorus quantum dot heterojunction.

[0071] Figure 3 This is the SEM photograph of the cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network prepared in Example 3 of the present invention. It can be seen that the catalyst particles present a dodecahedral morphology.

[0072] Example 4

[0073] The present invention discloses a cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network and a preparation method thereof, including the following steps:

[0074] (1) Weigh 0.001 mol of zinc nitrate and 0.05 mol of 2-methylimidazole, dissolve them in 10 ml of methanol solution, and mix and stir;

[0075] (2) Weigh 0.001 mol of cobalt nitrate and 0.05 mol of 2-methylimidazole, dissolve them in 10 ml of methanol solution, and mix and stir;

[0076] (3) Mix the two obtained solutions at a ratio of 1:3 and stir them evenly. Then place them in a reaction kettle and heat at 140 °C for 8 h, and wash and dry with methanol to obtain a metal precursor;

[0077] (4) Place the dried precursor in a high-temperature tube furnace filled with argon and heat it to 800 °C at a heating rate of 5 °C / min and hold for 5 h to obtain cobalt metal particles supported on a three-dimensional carbon network.

[0078] (5) Place bulk black phosphorus in a 50 ml DMF solution at a concentration of 1 g / L and ultrasonicate for 1 h. Centrifuge for the first time at a speed of 8000 r / min for 10 min, and take the precipitate. Centrifuge for the second time at a speed of 15000 r / min for 10 min;

[0079] (6) The cobalt metal particles supported on the three-dimensional carbon network were placed in the yellow clear solution of black phosphorus and stirred evenly, then placed in a reaction kettle and heated at 200 °C for 20 h, and washed and dried with DMF to obtain the three-dimensional carbon network supported transition metal / black phosphorus quantum dot heterojunction.

[0080] Figure 5 a is the TEM image of the cobalt metal nanoparticles / black phosphorus quantum dots supported on the three-dimensional carbon network, and carbon nanotubes and nitrogen-doped carbon can be seen; Figure 5 b and Figure 5 c are the high-resolution TEM photos of the cobalt / black phosphorus quantum dot heterojunction; the size of the cobalt particles is about 3 nm, and the size of the black phosphorus quantum dots is about 2 nm. It is obvious to see the heterojunction interface between the cobalt particles and the black phosphorus quantum dots.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the specific implementation manners of the present invention can still be modified or equivalently replaced, and any modification or equivalent replacement without departing from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. Preparation method of cobalt / black phosphorus quantum dot catalyst supported on three-dimensional carbon network, characterized in that, it includes the following processes: Weigh zinc salt and 2-methylimidazole, dissolve them in an organic solvent, mix and stir to obtain a zinc ion solution; Weigh cobalt salt and 2-methylimidazole, dissolve them in an organic solvent, mix and stir to obtain a cobalt ion solution; Mix and stir the zinc ion solution and the cobalt ion solution. After stirring evenly, heat and react at 100-140 °C for 6-24 h, wash and dry to obtain a metal-organic framework precursor; Under a protective atmosphere, heat the metal-organic framework precursor to 800 °C and keep it warm for 3-5 h to obtain cobalt metal particles supported on a three-dimensional carbon network; Place bulk black phosphorus in DMF solution and ultrasonicate for 1-3 h. After standing and centrifuging, take the upper light yellow clear black phosphorus solution; Place the cobalt metal particles supported on the three-dimensional carbon network in the black phosphorus solution. After stirring evenly, heat and react at 180-220 °C for 6-24 h, wash and dry to obtain a cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network.

2. The preparation method of the cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network according to claim 1, characterized in that, the concentration of the zinc salt in the organic solvent is 0.1 mol / L - 0.3 mol / L; the concentration of the cobalt salt in the organic solvent is 0.1 mol / L - 0.3 mol / L.

3. The preparation method of the cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network according to claim 1, characterized in that, the volume ratio of the zinc ion solution to the cobalt ion solution is 1:1 - 1:

3.

4. The preparation method of the cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network according to claim 1, characterized in that, the concentration of the bulk black phosphorus in the DMF solution is 0.001 - 1 g / L.

5. The cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network and its preparation method according to claim 1, characterized in that, centrifuge twice. The first centrifugation is carried out at a rotation speed of 5000 - 10000 r / min for 5 - 10 min, and the precipitate is taken. The second centrifugation is carried out at a rotation speed of 13000 - 17000 r / min for 5 - 10 min.

6. A cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network prepared by the preparation method described in any one of claims 1-5, characterized in that, the carbon network of the cobalt / black phosphorus quantum dot catalyst supported on the three-dimensional carbon network is composed of nitrogen-doped porous carbon and carbon nanotubes and presents a dodecahedral morphology; nano cobalt and black phosphorus quantum dots are supported on the carbon network, and nano cobalt and black phosphorus quantum dots form a Schottky heterojunction.

7. The cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network according to claim 6, characterized in that, the size of the nano cobalt particles is 2 - 5 nm, and the size of the black phosphorus quantum dots is 1 - 3 nm.

8. Application of the cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network described in claim 6 or 7 as a catalyst material in the electrocatalytic hydrogen evolution reaction.

9. Application of the cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network described in claim 6 or 7 as a catalyst material in the electrocatalytic oxygen evolution reaction.

10. Use of the cobalt / black phosphorus quantum dot catalyst supported on a three-dimensional carbon network according to claim 6 or 7 as a catalyst material in an electrocatalytic overall water splitting reaction.

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