Method for in-situ growth of carbon nanotube / graphdiyne electrocatalyst

Abstract

The application discloses a method for preparing a carbon nanotube / oxidized graphdiyne electrocatalyst in situ. The application is based on an in-situ anchoring-growth strategy, selects graphdiyne as a carbon material base for functionalization, utilizes stable and uniform dispersion of acetylenic bond of the graphdiyne to anchor metal atoms, and grows carbon nanotubes on the graphdiyne in situ with the metal atoms as catalysts, so that the connection between the graphdiyne and the carbon nanotubes can be observed, and a stable structure can be obtained. The carbon nanotube / graphdiyne structure is mildly oxidized by concentrated nitric acid, so that selective oxidation of the graphdiyne is realized, only the graphdiyne structure is oxidized, meanwhile, the carbon nanotube structure is not oxidized, the obtained functional groups are single, and a carbon nanotube / oxidized graphdiyne structure mainly with epoxy bond functional groups is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of preparation of nanocarbon material-based electrocatalysts, and particularly relates to a method for preparing a carbon nanotube / graphdiyne electrocatalyst by in-situ growth. BACKGROUND

[0002] Hydrogen peroxide (H2O2) as a green oxidant has a very wide application in the fields of industry, medicine and environmental protection, and has a large demand. At present, the preparation of H2O2 mainly depends on the anthraquinone method with high energy consumption and high waste, and the process needs a complex impurity separation process. Meanwhile, the instability of H2O2 brings high safety hazards in the storage and transportation process. Therefore, it has high application value to develop a direct, effective and economic method for in-situ preparation of H2O2. In recent years, the method for preparing H2O2 based on two-electron oxygen reduction (2e - ORR) has attracted attention. The two-electron oxygen reduction method for preparing H2O2 is not only environmentally friendly and low in consumption, but also can avoid the safety hazards in the transportation and storage process, and is an efficient and green alternative to the commercial anthraquinone method.

[0003] However, due to the existence of four-electron oxygen reduction competition, especially under neutral or acidic conditions, the selectivity of the two-electron oxygen reduction process is low. Generally, the oxidation of carbon materials can achieve high selectivity, but there are many problems: 1. The oxidation process often introduces multiple oxygen-containing functional groups at the same time, and the catalytic site is difficult to determine. 2. The reported oxidation carbon materials are mainly sp 2-Prepared on C substrate, the oxidation function mainly grows in the defect or edge position, and cannot form sufficient active sites. 3, due to the decrease of hydrophobicity of the material caused by oxidation, the three-phase interface gradually decreases in long-term operation, resulting in the decrease of catalytic stability (<200h). For example, the literature《Lim, June Sung, et al. Designing highly active nanoporous carbon H2O2 production electrocatalysts through active site identification[J]. Chem 2021(7):3114-3130.》 pointed out that only the edge or defect of the graphene sheet can be activated by the functional group, and the internal structure cannot realize effective functionalization. In addition, the literature《Wang, Yulin, et al. Electrocatalytic oxygen reduction to hydrogen peroxide: From homogeneous to heterogeneous electrocatalysis[J]. Advanced Energy Materials 2021(11):2003323.》 pointed out that the carbon-based material-based electrocatalyst for oxygen reduction to hydrogen peroxide is generally not ideal in stability, and most of them are less than 50h. Therefore, it is still a challenge to achieve high efficiency and excellent stability by selecting a suitable substrate and defining the functional group. SUMMARY

[0004] In view of the deficiencies of the prior art, the technical problem to be solved by the present application is to provide a method for in-situ growth and preparation of carbon nanotube / oxidized graphdiyne electrocatalyst.

[0005] The technical solution of the present application to solve the technical problem is to provide a method for in-situ growth and preparation of carbon nanotube / oxidized graphdiyne electrocatalyst, characterized in that the method comprises the following steps:

[0006] (1) adding graphdiyne powder and substance A into solvent A to obtain a mixed solution; then drying to remove solvent A in the mixed solution to obtain a mixed powder;

[0007] The substance A is a soluble cobalt salt, a soluble iron salt or a soluble nickel salt; the solvent A is a solvent capable of dissolving the substance A and not dissolving the graphdiyne;

[0008] (2) Put the mixed powder into a closed heating environment, heat to 600-900 DEG C in inert gas atmosphere; then continuously introduce inert gas carrying carbon source into the closed heating environment, carry the carbon source to the powder by inert gas, and carry out metal catalytic direct growth of carbon nanotubes; after the growth is completed, stop introducing the carbon source; then naturally cool to room temperature, stop introducing the inert gas; then remove the substance A, dry to obtain carbon nanotube / graphdiyne powder;

[0009] (3) Soak the carbon nanotube / graphdiyne powder in concentrated nitric acid, oxidize at a temperature of 0-30 DEG C for at most 48h; then remove the concentrated nitric acid, dry to obtain carbon nanotube / oxidized graphdiyne electrocatalyst.

[0010] Compared with the prior art, the beneficial effects of the present application are:

[0011] (1) Based on the in-situ growth-mild oxidation strategy, the present application innovatively prepares stable carbon nanotube / graphdiyne structure, and by controlling the oxidation conditions, selectively oxidized and relatively single functional group carbon nanotube / oxidized graphdiyne material with high selectivity and high stability two-electron oxygen reduction activity is obtained.

[0012] (2) Based on the in-situ anchoring-growth strategy, the present application selects graphdiyne as the carbon material substrate for functionalization, utilizes the alkyne bond of graphdiyne to stably and uniformly disperse and anchor metal atoms, and grows carbon nanotubes on the graphdiyne in-situ by using the metal atoms as catalysts, the connection between graphdiyne and carbon nanotubes can be observed, which is different from simple physical mixing, and stable structure can be obtained to provide stable catalytic performance.

[0013] (3) The present application realizes selective oxidation of graphdiyne (i.e. only the graphdiyne structure is oxidized, while the carbon nanotube structure is not oxidized) by mild oxidation of carbon nanotube / graphdiyne structure with concentrated nitric acid, the oxidation obtained functional group is single, and the carbon nanotube / oxidized graphdiyne structure mainly with epoxy bond functional group is obtained. By X-ray photoelectron spectroscopy and electron energy loss spectroscopy characterization, the oxygen content in the material after oxidation is 17.28%, and the proportion of epoxy bond is 85%, which confirms the selectivity and single nature of the oxidation process.

[0014] (4) The oxidized graphdiyne part in the electrocatalyst obtained by the present application can act as a catalytic active site for two-electron oxygen reduction, and the 3D carbon nanotube structure can effectively protect the active sites of the oxidized graphdiyne structure from being soaked, thereby improving the stability. By contact angle characterization, the contact angle of the material after oxidation to water is 128 DEG, and the hydrophobicity is obviously improved compared with the oxidized graphdiyne without growing carbon nanotubes.

[0015] (5) The carbon nanotube / oxidized graphdiyne material obtained by the application can be used as an oxygen reduction electrocatalyst to achieve high selectivity to hydrogen peroxide in alkaline and neutral electrolyte. Specifically, the selectivity in alkaline can reach 87%, and the initial potential is 0.78 V. In neutral phosphate buffer solution, the selectivity to hydrogen peroxide can reach 81%, and the initial potential is 0.49 V.

[0016] (6) The carbon nanotube / oxidized graphdiyne material obtained by the application can be used as an oxygen reduction electrocatalyst to achieve high stability of electrocatalytic production of hydrogen peroxide in alkaline and neutral electrolyte. Specifically, in alkaline, through the rotating disk electrode test, after 4.8 h of catalysis, the current still maintains 91% of the initial current. In neutral electrolyte, through the H electrolytic cell test, the material shows excellent stability, and can maintain stable operation for up to 330 h at a voltage of 0.05 V, and the operating current is basically unchanged, maintaining at 20 mA·cm -2 around. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The XRD pattern of the carbon nanotube / graphdiyne prepared in Example 1 of the application;

[0018] Figure 2 The SEM side view of the carbon nanotube / graphdiyne prepared in Example 1 of the application;

[0019] Figure 3 The SEM top view of the carbon nanotube / graphdiyne prepared in Example 1 of the application;

[0020] Figure 4 The SEM side view of the carbon nanotube / oxidized graphdiyne prepared in Example 1 of the application;

[0021] Figure 5 The high-magnification TEM image of the carbon nanotube / oxidized graphdiyne prepared in Example 1 of the application;

[0022] Figure 6 The electron energy loss spectrum of the carbon nanotube / oxidized graphdiyne prepared in Example 1 of the application;

[0023] Figure 7 The O1s XPS spectrum of the carbon nanotube / graphdiyne and the carbon nanotube / oxidized graphdiyne prepared in Example 1 of the application;

[0024] Figure 8 The contact angle photo of the carbon nanotube / oxidized graphdiyne prepared in Example 1 of the application and water;

[0025] Figure 9 The contact angle photo of the oxidized graphdiyne and water;

[0026] Figure 10 Linear sweep curve of carbon nanotube / oxidized graphdiyne prepared for the present application embodiment 1 for electrocatalytic production of H2O2 in alkaline electrolyte;

[0027] Figure 11 Selectivity result graph of carbon nanotube / oxidized graphdiyne prepared for the present application embodiment 1 for electrocatalytic production of H2O2 in alkaline electrolyte;

[0028] Figure 12 Stability test curve of carbon nanotube / oxidized graphdiyne prepared for the present application embodiment 1 for electrocatalytic production of H2O2 in alkaline electrolyte;

[0029] Figure 13 Linear sweep curve of carbon nanotube / oxidized graphdiyne prepared for the present application embodiment 1 for electrocatalytic production of H2O2 in neutral electrolyte;

[0030] Figure 14 Selectivity result graph of carbon nanotube / oxidized graphdiyne prepared for the present application embodiment 1 for electrocatalytic production of H2O2 in neutral electrolyte;

[0031] Figure 15 Stability test curve and corresponding Faraday efficiency graph of carbon nanotube / oxidized graphdiyne prepared for the present application embodiment 1 for electrocatalytic production of H2O2 in neutral electrolyte;

[0032] Figure 16 SEM graph of carbon nanotube / oxidized graphdiyne obtained for the present application embodiment 2;

[0033] Figure 17 Selectivity result graph of carbon nanotube / oxidized graphdiyne obtained for the present application embodiment 2 for electrocatalytic production of H2O2 in alkaline environment;

[0034] Figure 18 SEM graph of carbon nanotube / oxidized graphdiyne obtained for the present application embodiment 3;

[0035] Figure 19 Selectivity result graph of carbon nanotube / oxidized graphdiyne obtained for the present application embodiment 3 for electrocatalytic production of H2O2 in alkaline environment;

[0036] Figure 20 SEM graph of carbon nanotube / oxidized graphdiyne obtained for the present application embodiment 4;

[0037] Figure 21 Selectivity result graph of carbon nanotube / oxidized graphdiyne obtained for the present application embodiment 4 for electrocatalytic production of H2O2 in alkaline environment;

[0038] Figure 22 SEM graph of carbon nanotube / oxidized graphdiyne obtained for the present application embodiment 5;

[0039] Figure 23 Figure 4 is a graph showing the selectivity of the carbon nanotube / oxidized graphdiyne obtained from Example 5 for electrocatalytic production of H2O2 in an alkaline environment. DETAILED DESCRIPTION

[0040] The following specific examples are given to further illustrate the present application. The specific examples are not intended to limit the scope of the claims of the present application.

[0041] The present application provides a method for in-situ growth of carbon nanotube / oxidized graphdiyne electrocatalyst (hereinafter referred to as the method), characterized in that the method comprises the following steps:

[0042] (1) adding graphdiyne powder and substance A into solvent A to obtain a mixed solution; and then drying to remove solvent A in the mixed solution to obtain a mixed powder;

[0043] The substance A is a soluble cobalt salt, a soluble iron salt or a soluble nickel salt; and the solvent A is a solvent capable of dissolving the substance A and not dissolving the graphdiyne.

[0044] Preferably, in step (1), the mass ratio of the graphdiyne to the substance A is 0.5-5:100 (preferably 1:100).

[0045] Preferably, in step (1), the substance A is cobalt nitrate, cobalt chloride, cobalt acetate, cobalt sulfate, iron nitrate, iron chloride, nickel chloride, nickel nitrate or nickel sulfate; and the solvent A is ethanol or isopropyl alcohol.

[0046] Preferably, in step (1), the mixed solution is first evaporated by a rotary evaporation device such as a vacuum rotary evaporator, and then completely dried to remove the solvent A, to obtain the mixed powder. Such an operation makes the metal distribution more uniform.

[0047] Preferably, step (1) is specifically as follows: dissolving the substance A in the solvent A to obtain a homogeneous salt solution; then mixing and stirring the graphdiyne powder with the salt solution until uniform to obtain the mixed solution; and then drying to remove the solvent A in the mixed solution to obtain the mixed powder; the mixing and stirring time is > 12 h.

[0048] Preferably, in step (1), the drying process is vacuum drying in a vacuum oven at 60-90℃ for 5-12 h.

[0049] (2) placing the mixed powder into a closed heating environment (preferably at the thermal center of the closed heating environment), continuously supplying inert gas, heating to 600-900℃ in the inert gas atmosphere; then changing the gas path, continuously supplying inert gas carrying carbon source into the closed heating environment, carrying the carbon source onto the powder by the inert gas, and carrying out metal-catalyzed direct growth of carbon nanotubes; after the growth is completed, stopping the supply of carbon source and retaining the supply of inert gas; then naturally cooling to room temperature, stopping the supply of inert gas; and then removing the substance A, drying to obtain carbon nanotube / graphdiyne powder;

[0050] Preferably, in step (2), the closed heating environment uses a tube furnace. The inert gas uses nitrogen or argon, preferably argon.

[0051] Preferably, in step (2), the temperature is raised from room temperature to 600-900℃ at a rate of 3-10℃ / min, preferably 5℃ / min.

[0052] Preferably, in step (2), the carbon source is an organic alcohol small molecule compound, specifically ethanol, methanol or isopropyl alcohol.

[0053] Preferably, in step (2), the flow rate of the inert gas carrying carbon source is 200-1000sccm.

[0054] Preferably, in step (2), the time for metal-catalyzed direct growth is 0.5-5h.

[0055] Preferably, in step (2), the removal of the substance A uses a cleaning method with hydrochloric acid or sulfuric acid with a concentration of 1M-3M.

[0056] (3) soaking the carbon nanotube / graphdiyne powder in concentrated nitric acid, oxidizing at a temperature of 0-30℃ (preferably 20-30℃) for up to 48h (preferably 10-20h, more preferably 12h) ; then removing the concentrated nitric acid, drying to obtain carbon nanotube / oxidized graphdiyne electrocatalyst.

[0057] Preferably, in step (3), the mass fraction of the concentrated nitric acid is 60-70wt% (preferably 65-68wt%, more preferably 65wt%).

[0058] Preferably, in step (3), the amount of the concentrated nitric acid is sufficient to immerse the carbon nanotube / graphdiyne powder or is in excess.

[0059] Preferably, in step (3), the powder can be dispersed by ultrasonic or stirring during the oxidation process to increase effective contact.

[0060] Preferably, in step (3), the removal of the concentrated nitric acid uses a centrifugation or suction filtration method, using a centrifuge or suction filtration equipment, and finally making the pH 7.

[0061] Preferably, in step (3), the drying is performed by vacuum drying or freeze drying.

[0062] Example 1

[0063] (1) 0.2 mg of Co(N03)2-6H20 was dissolved in 20 mL of anhydrous ethanol to form a uniform salt solution; 20 mg of graphdiyne powder was then dispersed in the salt solution and stirred at room temperature for 12 h to obtain a mixture; the ethanol was removed by a vacuum rotary evaporator, and the mixture was then dried at 60 °C for 6 h to obtain a mixed powder;

[0064] (2) The mixed powder was placed in a quartz boat and put into a sealed heating tube furnace; the temperature was raised to 800 °C at a rate of 5 °C / min under an argon atmosphere with a flow rate of 200 seem; then the ethanol passage was opened, and argon flowed through the ethanol and carried the ethanol into the tube furnace to contact the mixed powder, and the ethanol molecules were cracked under the catalysis of the metal to grow carbon nanotubes; after 1 h of growth, the ethanol passage was closed, and the argon flow was maintained; then the argon was turned off after natural cooling to room temperature; the product powder was collected and soaked in 1 M dilute hydrochloric acid for 6 h to remove the metal particles in the powder; then the carbon nanotube / graphdiyne powder was obtained by freeze drying;

[0065] (3) The carbon nanotube / graphdiyne powder was soaked in 5 mL of 65 wt% concentrated nitric acid at 30 °C for 12 h; then the concentrated nitric acid was removed by repeated washing with ultrapure water until the pH of the system was 7; after drying, the carbon nanotube / oxidized graphdiyne electrocatalyst was obtained.

[0066] From Figure 1 As can be seen, the main diffraction peaks of the carbon nanotube / graphdiyne obtained in step 2 can well correspond to the PDF #75-1621 card of graphite carbon.

[0067] From Figure 2 As can be seen, in step 2, the in-situ grown carbon nanotubes are spatially distributed on the graphdiyne film, and the size of the carbon nanotubes is uniform, with a diameter of about 100 nm.

[0068] From Figure 3 As can be seen, the in-situ grown carbon nanotubes in step 2 are uniformly distributed.

[0069] From Figure 4 As can be seen, the 3D morphology of the carbon nanotube / oxidized graphdiyne obtained in step 3 is well preserved.

[0070] From Figure 5 As can be seen, the carbon nanotube / oxidized graphdiyne has obvious connection between the carbon nanotubes and the graphdiyne.

[0071] From Figure 6It can be seen that the material obtained in step 3 shows obvious oxidation of graphdiyne in the electron energy loss spectrum, and the oxidation is mainly in the form of an epoxy bond. The carbon nanotube has no obvious oxygen-containing signal, indicating that the carbon nanotube is not oxidized under the experimental conditions.

[0072] By Figure 7 It can be seen that the content of C=O remains basically unchanged before and after the oxidation treatment, and the content of C-O group obviously increases after the oxidation. Figure 6 It can be seen that the experimental oxidation conditions can obtain an oxidation structure of graphdiyne mainly in the form of an epoxy bond, which is protected by the unoxidized carbon nanotube.

[0073] By Figures 8-9 It can be seen that, compared with the oxidized graphdiyne without growth of carbon nanotube (the contact angle of water is 18°, Figure 9 , the contact angle of water of the carbon nanotube / oxidized graphdiyne (CNTs / GDY-O, Figure 8 ) prepared in Example 1 is 128°, which has good hydrophobicity.

[0074] The CNTs / GDY-O prepared in Example 1 is used for 2e - electrocatalytic oxygen reduction to prepare H2O2, and the specific steps are as follows:

[0075] (1) 5 mg of CNTs / GDY-O is added to 950 μL of anhydrous ethanol, 50 μL of a nafion (5 wt%) solution is added, and after ultrasonic dispersion, it is dropped and coated on the disk electrode of the rotating disk electrode, and the loading amount is 0.2 mg·cm -2 , which is used as a negative working electrode; a platinum sheet is used as a counter electrode, and a saturated calomel electrode is used as a reference electrode;

[0076] (2) During the electrochemical test, 0.1M potassium hydroxide solution (pH=13.8) is used as an electrolyte, and the test is carried out on the rotating disk electrode. During the test, O2 is continuously introduced to form a saturated solution. In the voltage range of 0.1V~1V, the ring current and the disk current density are measured, and the selectivity of the catalyst to hydrogen peroxide in the alkaline environment is calculated;

[0077] (3) After replacing the new electrolyte and re-preparing the electrode sample, oxygen is continuously introduced to test the stability of the catalytic performance;

[0078] (4) Replace the 0.1M phosphate buffer solution (pH=7.4) electrolyte, and continuously introduce O2 to form a saturated solution during the test. In the voltage range of 0.1V~1V, the ring current and the disk current density are measured, and the selectivity of the catalyst to hydrogen peroxide in the alkaline environment is calculated;

[0079] (5) In 0.1M phosphate buffer solution (pH = 7.4) electrolyte, the saturated solution is formed by continuously passing O2 during the test, and the electrochemical oxygen reduction is carried out at 0.05V voltage to prepare H2O2; the electrolyte is replaced every 20h; the product content is determined by ultraviolet spectrophotometry;

[0080] (6) The effective catalytic life of the accumulated catalyst can be maintained by continuously updating the electrolyte.

[0081] The electrochemical performance of the two-electron electrocatalytic oxygen reduction is as shown in Figures 10-15 .

[0082] It can be seen from Figure 10 that in the alkaline electrolyte, the initial potential of oxygen reduction is 0.78V, and the overall oxygen reduction current density can reach 3mA·cm -2 , wherein the yield of hydrogen peroxide is monitored by a ring electrode, and the calculation shows that the yield of hydrogen peroxide can reach 2mA·cm -2 .

[0083] Figure 11 It can be seen from Figure 10 that the two-electron selectivity of the carbon nanotube / oxidized graphdiyne converted according to the formula can reach 87% at 0.4V voltage, and the overall selectivity is maintained above 80%, indicating that the material has good electrocatalytic hydrogen peroxide production performance in alkaline.

[0084] It can be seen from Figure 12 that the oxygen reduction stability of the material in alkaline is measured by a rotating disk electrode at 0.35V voltage, and the overall current of the material remains unchanged after maintaining the test for 4.7h, and the selectivity remains stable.

[0085] It can be seen from Figure 13 that in the neutral electrolyte, the current density can reach 3.1mA·cm -2 in the test range of 0.1-0.7V voltage, wherein the yield of hydrogen peroxide is monitored by a ring electrode, and the calculation shows that the yield of hydrogen peroxide can reach 1.67mA cm -2 .

[0086] Figure 14 It can be seen from Figure 13 that the two-electron selectivity of the carbon nanotube / oxidized graphdiyne converted according to the formula in a neutral environment can be calculated according to the formula, and the overall selectivity is above 80% on average, indicating that the material has good electrocatalytic hydrogen peroxide production performance in a neutral environment.

[0087] The two-electron oxygen reduction stability test (time-current-Faraday efficiency) of the carbon nanotube / oxidized graphdiyne in the neutral electrolyte is as shown in Figure 15 . Figure 15It can be seen that the catalyst can maintain approximately 20 mA·cm at a voltage of 0.05 V. -2 The reduction current density was maintained, and the catalyst operated stably for over 330 hours, indicating that the prepared catalyst possesses good electrocatalytic stability. Meanwhile, from... Figure 15 It can be seen that during the catalytic process of 330 h, the average Faraday efficiency of oxygen reduction to H2O2 production can reach 91.8%, indicating that the material has good catalytic selectivity in neutral electrolyte.

[0088] Example 2

[0089] Example 2 differs from Example 1 in that the mass of cobalt nitrate in step (1) is changed to 0.1 mg. Everything else is the same as in Example 1.

[0090] Depend on Figure 16 It can be seen that carbon nanotube / graphyne structures can be grown when the mass of cobalt nitrate is 0.1 mg. The difference is that the amount of carbon nanotubes grown decreases when the cobalt nitrate content decreases.

[0091] Depend on Figure 17 It can be seen that in alkaline electrolyte, the catalyst obtained in Example 2 can maintain approximately 75% H2O2 selectivity within a voltage range of 0.1V to 0.8V, indicating that its 2e... - Catalytic activity.

[0092] Example 3

[0093] Example 3 differs from Example 1 in that the mass of cobalt nitrate in step (1) is changed to 0.4 mg. Everything else is the same as in Example 1.

[0094] Depend on Figure 18 It can be seen that carbon nanotube / graphyne structures can be grown when the mass of cobalt nitrate is 0.4 mg. The difference is that the amount of carbon nanotubes grown increases when the cobalt nitrate content increases.

[0095] Depend on Figure 19 It can be seen that, in an alkaline electrolyte, the catalyst obtained in Example 3 can maintain approximately 65% ​​H2O2 selectivity within a voltage range of 0.1V to 0.8V, indicating that its 2e... - Catalytic activity.

[0096] Example 4

[0097] Example 4 differs from Example 1 in that the growth time in step (2) is changed to 0.5 h. Everything else is the same as in Example 1.

[0098] Depend on Figure 20 It can be seen that carbon nanotube / graphyne structure can be grown when the growth time is 0.5h. The difference is that the amount of carbon nanotubes grown decreases when the growth time is reduced.

[0099] By Figure 21 It can be seen that in the alkaline electrolyte, the catalyst obtained in Example 4 can maintain about 75% selectivity of H2O2 in the voltage range of 0.1V-0.8V, indicating that the 2e - catalytic activity.

[0100] Example 5

[0101] Example 5 is different from Example 1 in that the growth time in step (2) is changed to 2h. The others are the same as Example 1.

[0102] By Figure 22 It can be seen that when the growth time is 2h, carbon nanotube / graphdiyne structures can be grown, and the difference is that the amount of carbon nanotube growth increases when the growth time is extended.

[0103] By Figure 23 It can be seen that in the alkaline electrolyte, the catalyst obtained in Example 5 can maintain about 82% selectivity of H2O2 in the voltage range of 0.1V-0.8V, indicating that the 2e - catalytic activity.

[0104] The unmentioned part of the present application is applicable to the prior art.

Claims

1. A method for in-situ growth preparation of carbon nanotube / graphdiyne electrocatalyst, characterized in that, The method comprises the following steps: (1) adding the graphdiyne powder and a substance A into a solvent A to obtain a mixed solution; removing the solvent A in the mixed solution by drying to obtain a mixed powder; the mass ratio of the graphdiyne to the substance A is 0.5-5:100; The substance A is a soluble cobalt salt, a soluble iron salt or a soluble nickel salt; the solvent A is a solvent capable of dissolving the substance A and not dissolving the graphdiyne; (2) placing the mixed powder into a closed heating environment, heating to 600-900℃ in an inert gas atmosphere; then continuously introducing the inert gas carrying a carbon source into the closed heating environment, carrying the carbon source onto the powder by the inert gas to perform metal-catalyzed direct growth of carbon nanotubes; after the growth is completed, the introduction of the carbon source is stopped; then, after natural cooling to room temperature, the introduction of the inert gas is stopped; then, the substance A is removed, and after drying, a carbon nanotube / graphdiyne powder is obtained; the carbon source is ethanol, methanol or isopropyl alcohol; (3) soaking the carbon nanotube / graphdiyne powder in concentrated nitric acid with a mass fraction of 60-70wt% at a temperature of 0-30℃ for 10-12h; then removing the concentrated nitric acid, and after drying, a carbon nanotube / oxidized graphdiyne electrocatalyst is obtained. 2.The method for in-situ growth preparation of carbon nanotube / graphdiyne electrocatalyst according to claim 1, characterized in that, In step (1), the substance A is cobalt nitrate, cobalt chloride, cobalt acetate, cobalt sulfate, iron nitrate, iron chloride, nickel chloride, nickel nitrate or nickel sulfate; and the solvent A is ethanol or isopropyl alcohol. 3.The method for in-situ growth preparation of carbon nanotube / graphdiyne electrocatalyst according to claim 1, characterized in that, In step (1), the mixed solution is first evaporated by a rotary evaporation device to evaporate the solvent A, and then completely removed by drying to obtain the mixed powder. 4.The method for in-situ growth preparation of carbon nanotube / graphdiyne electrocatalyst according to claim 1, characterized in that, In step (2), the heating rate is 3-10℃ / min.

5. The method for in-situ growth preparation of carbon nanotube / graphdiyne electrocatalyst according to claim 1, characterized in that, In step (2), the flow rate of the inert gas carrying the carbon source is 200-1000sccm.

6. The method for in-situ growth preparation of carbon nanotube / graphdiyne electrocatalyst according to claim 1, characterized in that, In step (2), the time for the metal-catalyzed direct growth is 0.5-5h.

7. The method for in-situ growth preparation of carbon nanotube / graphdiyne electrocatalyst according to claim 1, characterized in that, In step (3), the concentrated nitric acid is removed by centrifugation or suction filtration to make the pH be 7.

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