G-C3N4 coupled cobalt-nitrogen co-doped hierarchical porous carbon bifunctional light-enhanced catalyst as well as preparation method and application of g-C3N4 coupled cobalt-nitrogen co-doped hierarchical porous carbon bifunctional light-enhanced catalyst

Abstract

The invention relates to a g-C3N4 coupled cobalt-nitrogen co-doped hierarchical porous carbon bifunctional light-enhanced catalyst as well as a preparation method and application thereof. The catalyst is prepared by taking n-type g-C3N4 and p-type cobalt-nitrogen co-doped hierarchical porous carbon as light-assisted monomer materials. The catalyst g-C3N4 and the cobalt-nitrogen co-doped hierarchical porous carbon are spliced in a staggered mode, the specific surface area is large, and the catalyst g-C3N4 and the cobalt-nitrogen co-doped hierarchical porous carbon are directly used as an air electrode to assemble a zinc-air battery, so that ultrahigh power density and charge-discharge stability under light driving can be achieved; the preparation method is simple, raw materials are cheap and easy to obtain, large-scale preparation can be achieved, and good application prospects are achieved.

Description

Technical Field

[0001] The invention belongs to the field of photocatalysis, and particularly relates to a g-C3N4 coupled cobalt-nitrogen co-doped multi-level porous carbon dual-function light-enhanced catalyst and a preparation method and application thereof. Background Art

[0002] The rapid development of the contemporary economy has led to a sharp acceleration of the industrialization process. The global energy crisis and increasingly serious environmental problems have hindered social development. Therefore, clean energy such as solar energy, wind energy, and electrochemical energy have attracted widespread attention. Among them, fuel cells (including zinc-air batteries) have become the focus of researchers due to their safety, reliability, environmental friendliness, low cost, and high theoretical specific energy density. The oxygen catalytic reaction occurring on the air electrode is the key to determining the performance of the fuel cell. Due to its slow oxygen reduction (for hydrogen-air fuel cells) and high overpotential oxygen evolution reaction, the large-scale commercial application of fuel cells (including zinc-air batteries) is severely limited. As a clean energy source, solar energy has the advantages of large energy, strong renewability, and clean and environmental protection. It has great development potential, but the stability of solar power supply is severely limited by weather conditions, making power storage a difficult problem faced by solar power supply. In order to solve the above problems, based on the photoelectric coupling mechanism and synergistic promotion effect, a light-enhanced ORR / OER bifunctional catalyst was designed and prepared, which can effectively reduce the charging overpotential of the air electrode, realize the combination of photochemical and electrochemical energy conversion and storage through solar energy, and provide new development opportunities for the application of photoelectric coupled fuel cells. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a g-C3N4 coupled cobalt-nitrogen co-doped multi-level porous carbon bifunctional light-enhanced catalyst and its preparation method and application, which solves the technical problems in the prior art such as low specific surface area of ​​the catalyst, insufficient exposure of active sites and low electronic conductivity.

[0004] The present invention provides a g-C3N4 coupled cobalt-nitrogen co-doped multi-level porous carbon dual-function light-enhanced catalyst, wherein the catalyst is obtained by using n-type g-C3N4 and p-type cobalt-nitrogen co-doped multi-level porous carbon as light-assisted monomer materials.

[0005] The present invention also provides a method for preparing a g-C3N4 coupled cobalt-nitrogen co-doped multi-level porous carbon dual-function light-enhanced catalyst, comprising the following steps:

[0006] (1) Weighing urea and placing it in a muffle furnace for calcination, and after cooling it to room temperature, grinding it to obtain g-C3N4;

[0007] (2) Weighing Co(NO3)2·6H2O, polyquaternium-7 and silicon dioxide, adding hydrochloric acid, stirring, drying and ball milling to obtain a hierarchical porous carbon precursor;

[0008] (3) calcining the precursor in a tube furnace to obtain a primary carbonization product; taking the carbonized product, alkali washing, acid washing, filtering to neutrality and drying to obtain a product; calcining the product again in a tube furnace to obtain a secondary carbonization product, i.e., cobalt-nitrogen co-doped hierarchical porous carbon;

[0009] (4) Take g-C3N4 and cobalt-nitrogen co-doped hierarchical porous carbon, and obtain g-C3N4 coupled cobalt-nitrogen co-doped hierarchical porous carbon bifunctional light-enhanced catalyst through ball milling.

[0010] Preferably, the calcination heating rate in step (1) is 2-4°C / min, the temperature is raised to 400-600°C, and the holding time is 1-3h.

[0011] Preferably, the mass volume ratio of Co(NO3)2·6H2O, polyquaternium-7, silicon dioxide and hydrochloric acid in step (2) is 5-10g:2-3g:1-5g:85-110ml.

[0012] Preferably, the concentration of hydrochloric acid in step (2) is 0.5-1M.

[0013] Preferably, the calcination temperature of the primary carbonization product obtained in step (3) is 700-1000° C., the atmosphere is nitrogen, the heating rate is 10-20° C. / min, and the insulation time is 1-5 h.

[0014] Preferably, the concentration of the sodium hydroxide solution used in the alkali washing in step (3) is 4 to 8 M, and the alkali washing time is 24 to 96 h; the concentration of the H2SO4 solution used in the acid washing is 0.1 to 1 M, and the acid washing time is 6 to 12 h.

[0015] Preferably, the calcination temperature of the secondary carbonization product obtained in step (3) is 700-1000° C., the atmosphere is nitrogen, the heating rate is 10-20° C. / min, and the holding time is 1-5 h.

[0016] Preferably, the mass ratio of g-C3N4 to co-doped hierarchical porous carbon of cobalt-nitrogen in step (4) is 1:100 to 2:5.

[0017] Preferably, the ball milling treatment time in step (4) is 1 to 10 hours, and the rotation speed is 200 to 400 rpm.

[0018] The present invention also provides an application of a g-C3N4 coupled cobalt-nitrogen co-doped multi-level porous carbon bifunctional light-enhanced catalyst in a light-enhanced zinc-air battery.

[0019] Beneficial Effects

[0020] (1) The present invention can effectively expose active sites by coupling g-C3N4 with cobalt-nitrogen co-doped multi-level porous carbon, thereby improving the shortcomings of single g-C3N4, such as small specific surface area, high recombination rate of photogenerated carriers and low efficiency of visible light utilization, which is beneficial to improving the photocatalytic activity of the catalyst.

[0021] (2) The present invention can adjust the electronic structure or generate new electronic states by doping nitrogen in the multi-level porous carbon, thereby reducing the activation energy and improving the function of the carbon carrier. Cobalt (Co), as a widely used transition metal, is introduced into the carbon lattice and modified by nitrogen doping to form Co-N active centers. These active centers exist not only on the exposed metal atoms, but also in the nitrogen-doped graphite carbon structure on the metal surface. The increase in the number of active sites can significantly improve the ORR catalytic efficiency. At the same time, nitrogen doping can enhance the electronic properties of the material. Combined with the high stability of carbon materials, it effectively enhances the overall stability and service life of the catalyst.

[0022] (3) The present invention introduces an n-type semiconductor g-C3N4 with a suitable band gap width, and co-dopes it with p-type cobalt-nitrogen multi-level porous carbon as a photocatalytically active monomer material of the catalyst, and constructs a light-enhanced catalyst with a suitable energy band structure, strong light absorption ability, and a staggered pn heterostructure through π-π bond reconstruction. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 a is the SEM image (a) and TEM image (b) of g-C3N4@Co-N / MPC prepared in Example 1;

[0024] Figure 2a This is a comparison chart of the ORR performance of the g-C3N4@Co-N / MPC catalyst prepared under different conditions in Examples 1 to 4 and the commercial catalyst Pt / C and IrO2 mixed catalyst in 0.1M KOH;

[0025] Figure 2b A comparison of the OER performance of the g-C3N4@Co-N / MPC catalyst prepared under different conditions in Examples 1 to 4 and the commercial catalyst Pt / C and IrO2 mixed catalyst in 1M KOH;

[0026] Figure 3a The power density curve of the zinc-air battery assembly assembled with the g-C3N4@Co-N / MPC catalyst prepared in Example 1;

[0027] Figure 3b This is the charge and discharge cycle performance diagram of the rechargeable zinc-air battery assembly assembled with the g-C3N4@Co-N / MPC catalyst prepared in Example 1. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0029] The surface morphology of the product of the embodiment of the present invention was characterized by scanning electron microscopy (FESEM, S-4800) and field emission transmission electron microscopy (TEM, JEM-2100F). The elemental composition of the sample was analyzed by X-ray photoelectron spectrometer (XPS, Escalab 250Xi). The electrochemical performance test was carried out on Chenhua CHI760D electrochemical workstation using a three-electrode system. The cycling performance of the light-enhanced zinc-air battery was tested by a blue electric test system.

[0030] Example 1

[0031] Step 1): Weigh urea, grind it and place it in a muffle furnace, heat it to 570°C at 2.5°C / min, keep it for 3 hours, and after cooling it to room temperature, pour it into a mortar and grind it into a light yellow fine powder to obtain g-C3N4;

[0032] Step 2): Weigh 7.32g Co(NO3)2·6H2O, 22.5ml 10%wt polyquaternium-7, 5g silica powder in a beaker, add 85mL 0.7M hydrochloric acid, stir magnetically for 5h, place in an oven at 85°C and dry for 48h, grind to powder to obtain a precursor;

[0033] Step 3): Take the precursor powder into a quartz boat, and in an atmosphere filled with N2, heat it to 800°C at 20°C / min and keep it for 1h to obtain a primary carbonization product;

[0034] Step 4): Place the product after primary carbonization in a 6M NaOH solution and stir for 24 hours, filter until neutral, and dry in an oven at 85°C for 32 hours. After drying, place in a 0.5M H2SO4 solution, heat in a water bath at 85°C and stir for 8 hours, then filter until neutral, and dry in an oven at 85°C for 24 hours to obtain an acid-washed product;

[0035] Step 5): The acid-washed product is placed in a quartz boat, and the temperature is raised to 800°C at 20°C / min in an atmosphere filled with N2 and maintained for 2h to obtain cobalt-nitrogen co-doped multi-level porous carbon, i.e., Co-N / MPC;

[0036] Step 6): Weigh g-C3N4 and Co-N / MPC (mass ratio of 3:10) and ball mill for 2h (300rpm) to obtain g-C3N4 coupled cobalt-nitrogen co-doped multi-level porous carbon bifunctional light-enhanced catalyst, i.e. g-C3N4@Co-N / MPC30.

[0037] Example 2

[0038] Step 1): Weigh urea, grind it and place it in a muffle furnace, heat it to 570°C at 2.5°C / min, keep it for 3 hours, wait for it to cool to room temperature, pour it into a mortar and grind it into a light yellow fine powder to obtain g-C3N4;

[0039] Step 2): Weigh 7.32g Co(NO3)2·6H2O, 22.5ml 10%wt polyquaternium-7, 5g silica powder in a beaker, add 85mL 0.6M hydrochloric acid, stir magnetically for 5h, place in an oven at 85°C and dry for 48h, grind to powder to obtain a precursor;

[0040] Step 3): Take the precursor powder into a quartz boat, and in an atmosphere filled with N2, heat it to 800°C at 20°C / min and keep it for 1h to obtain a primary carbonization product;

[0041] Step 4) The primary carbonization product is placed in a 6M NaOH solution and stirred for 24 hours, filtered to neutrality, and dried in an oven at 85°C for 32 hours. After drying, it is placed in a 0.5M H2SO4 solution, heated in a water bath at 85°C and stirred for 8 hours, then filtered to neutrality, and dried in an oven at 85°C for 24 hours to obtain an acid-washed product;

[0042] Step 5): The acid-washed product is placed in a quartz boat, and the temperature is raised to 800°C at 20°C / min and maintained for 2h in an atmosphere filled with N2 to obtain cobalt-nitrogen co-doped multi-level porous carbon, i.e., Co-N / MPC;

[0043] Step 6): Weigh g-C3N4 and Co-N / MPC (mass ratio of 1:10) and ball mill for 2h (300rpm) to obtain g-C3N4 coupled cobalt-nitrogen co-doped multi-level porous carbon bifunctional light-enhanced catalyst, i.e. g-C3N4@Co-N / MPC10.

[0044] Example 3

[0045] Step 1): Weigh urea, grind it and place it in a muffle furnace, heat it to 570°C at 2.5°C / min, keep it for 3 hours, and after cooling it to room temperature, pour it into a mortar and grind it into a light yellow fine powder to obtain g-C3N4;

[0046] Step 2): Weigh 7.32g Co(NO3)2·6H2O, 22.5ml 10%wt polyquaternium-7, 5g silica powder in a beaker, add 85mL 0.6M hydrochloric acid, stir magnetically for 5h, place in an oven at 85°C and dry for 48h, grind to powder to obtain a precursor;

[0047] Step 3): Take the precursor powder into a quartz boat, and in an atmosphere filled with N2, heat it to 800°C at 20°C / min and keep it for 1h to obtain a primary carbonization product;

[0048] Step 4) The primary carbonization product is placed in a 6M NaOH solution and stirred for 24 hours, filtered to neutrality, and dried in an oven at 85°C for 32 hours. After drying, it is placed in a 0.5M H2SO4 solution, heated in a water bath at 85°C and stirred for 8 hours, then filtered to neutrality, and dried in an oven at 85°C for 24 hours to obtain an acid-washed product;

[0049] Step 5): The acid-washed product is placed in a quartz boat, and the temperature is raised to 800°C at 20°C / min and maintained for 2h in an atmosphere filled with N2 to obtain cobalt-nitrogen co-doped multi-level porous carbon, i.e., Co-N / MPC;

[0050] Step 6): Weigh g-C3N4 and Co-N / MPC (mass ratio of 2:10) and ball mill for 2h (300rpm) to obtain g-C3N4 coupled cobalt-nitrogen co-doped multi-level porous carbon bifunctional light-enhanced catalyst, i.e. g-C3N4@Co-N / MPC20.

[0051] Example 4

[0052] Step 1): Weigh urea, grind it and place it in a muffle furnace, heat it to 570°C at 2.5°C / min, keep it for 3 hours, and after cooling it to room temperature, pour it into a mortar and grind it into a light yellow fine powder to obtain g-C3N4;

[0053] Step 2): Weigh 7.32g Co(NO3)2·6H2O, 22.5ml 10%wt polyquaternium-7, 5g silica powder in a beaker, add 85mL 0.6M hydrochloric acid, stir magnetically for 5h, place in an oven at 85°C and dry for 48h, grind to powder to obtain a precursor;

[0054] Step 3): Take the precursor powder into a quartz boat, and in an atmosphere filled with N2, heat it to 800°C at 20°C / min and keep it for 1h to obtain a primary carbonization product;

[0055] Step 4) The primary carbonization product is placed in a 6M NaOH solution and stirred for 24 hours, filtered to neutrality, and dried in an oven at 85°C for 32 hours. After drying, it is placed in a 0.5M H2SO4 solution, heated in a water bath at 85°C and stirred for 8 hours, then filtered to neutrality, and dried in an oven at 85°C for 24 hours to obtain an acid-washed product;

[0056] Step 5): The acid-washed product is placed in a quartz boat, and the temperature is raised to 800°C at 20°C / min and maintained for 2h in an atmosphere filled with N2 to obtain cobalt-nitrogen co-doped multi-level porous carbon, i.e., Co-N / MPC;

[0057] Step 6): Weigh g-C3N4 and Co-N / MPC (mass ratio of 4:10) and ball mill for 4h (400rpm) to obtain g-C3N4 coupled cobalt-nitrogen co-doped multi-level porous carbon bifunctional light-enhanced catalyst, i.e. g-C3N4@Co-N / MPC40.

[0058] Figure 1 a is the SEM image of the g-C3N4@Co-N / MPC light-enhanced catalyst prepared in Example 1. The image shows that the laver-like g-C3N4 is embedded in the dense and porous Co-N / MPC, indicating that the g-C3N4@Co-N / MPC is successfully coupled with Figure 1 b TEM image corresponding to the above.

[0059] Figure 2a The oxygen reduction performance comparison diagram of the catalyst materials prepared in Examples 1 to 4 and the commercial catalyst Pt / C+IrO2 is shown in Figure 1. It can be seen that the half-wave potential E of g-C3N4@Co-N / MPC under light 1 / 2 The limiting current density is significantly better than that of other materials under dark conditions. 1 / 2 The value is almost the same as that of Pt / C+IrO2 catalyst, indicating that g-C3N4@Co-N / MPC catalyst has excellent ORR electrochemical catalytic activity.

[0060] Figure 2b The oxygen evolution performance comparison diagram of the catalyst materials prepared in Examples 1 to 4 and the commercial catalyst Pt / C+IrO2 is shown in Figure 1. -2 When , the overpotential of the g-C3N4@Co-N / MPC catalyst under light irradiation is significantly reduced, indicating that the g-C3N4@Co-N / MPC catalyst not only has excellent OER electrochemical catalytic activity, but also has excellent OER photocatalytic activity.

[0061] Figure 3a This is the power density diagram of zinc air assembled by g-C3N4@Co-N / MPC catalyst prepared in Example 1. It can be seen that the power density value under illumination conditions is as high as 850mW / cm2 .

[0062] Figure 3b The zinc-air battery assembled with the g-C3N4@Co-N / MPC catalyst prepared in Example 1 was placed under light and dark conditions at 5 mA / cm 2 Comparison of constant current charge and discharge cycle performance. It can be seen that the voltage difference △E of the zinc-air battery tested under light conditions is only 0.74V, which is significantly lower than the test value under dark conditions (△E=0.920V). This shows that the zinc-air battery assembled by g-C3N4@Co-N / MPC catalyst not only exhibits excellent charge and discharge stability under light, but also greatly reduces the overpotential of the charging process, thereby significantly improving the performance of the zinc-air battery.

[0063] The above embodiments are only preferred embodiments of the present invention and are not any formal or substantial limitations of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A gC 3 N 4 Coupling Cobalt-Nitride Co-doped Hierarchical Porous Carbon Bifunctional Photoenhanced Catalyst, Features: The catalyst is n-type gC 3 N 4 The p-type co-doped cobalt-nitrogen multi-level porous carbon is obtained as a light-assisted monomer material.

2. A gC 3 N 4 The preparation method of the coupled cobalt-nitrogen co-doped hierarchical porous carbon bifunctional light-enhanced catalyst comprises the following steps: (1) Weigh urea and place it in a muffle furnace for calcination. After cooling to room temperature, grind it to obtain gC 3 N 4 ; (2) Weigh Co(NO 3 ) 2 6H 2 O, polyquaternium-7 and silicon dioxide, and adding hydrochloric acid, stirring, drying and ball milling to obtain a hierarchical porous carbon precursor; (3) calcining the precursor in a tube furnace to obtain a primary carbonization product; taking the carbonized product, alkali washing, acid washing, filtering to neutrality and drying to obtain a product; calcining the product again in a tube furnace to obtain a secondary carbonization product, i.e., cobalt-nitrogen co-doped hierarchical porous carbon; (4) Take gC 3 N 4 Cobalt-nitrogen co-doped hierarchical porous carbon was ball-milled to obtain gC 3 N 4 Coupled cobalt-nitrogen co-doped hierarchical porous carbon bifunctional photoenhanced catalyst.

3. The preparation method according to claim 2, Features: The calcination heating rate in the step (1) is 2-4°C / min, the temperature is raised to 400-600°C, and the holding time is 1-3h.

4. The preparation method according to claim 2, Features: The Co(NO 3 ) 2 6H 2 The mass volume ratio of O, polyquaternium-7, silicon dioxide and hydrochloric acid is 5-10g:2-3g:1-5g:85-110ml.

5. The preparation method according to claim 2, Features: The calcination temperature of the primary carbonization product obtained in the step (3) is 700-1000° C., the atmosphere is nitrogen, the heating rate is 10-20° C. / min, and the insulation time is 1-5 h.

6. The preparation method according to claim 2, Features: The concentration of the sodium hydroxide solution used in the alkali washing in step (3) is 4 to 8 M, and the alkali washing time is 24 to 96 hours; the H 2 SO 4 The solution concentration is 0.1~1M, and the pickling time is 6~12h.

7. The preparation method according to claim 2, Features: The calcination temperature of the secondary carbonization product obtained in the step (3) is 700-1000° C., the atmosphere is nitrogen, the heating rate is 10-20° C. / min, and the insulation time is 1-5 h.

8. The preparation method according to claim 2, Features: In step (4), gC 3 N 4 The mass ratio of co-doped hierarchical porous carbon with cobalt-nitrogen is 1:100 to 2:

5.

9. The preparation method according to claim 2, Features: The ball milling treatment time in step (4) is 1 to 10 hours, and the rotation speed is 200 to 400 rpm.

10. A gC as claimed in claim 1 3 N 4 Coupled cobalt-nitrogen co-doped hierarchical porous carbon bifunctional photoenhanced catalyst for application in photoenhanced zinc-air batteries.

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