Nickel amination-based monatomic catalyst as well as preparation method and application thereof

Abstract

The invention discloses a monatomic catalyst based on aminated nickel and a preparation method and application thereof.The preparation method comprises the steps that a purple blocky precursor is ground and then subjected to hot sintering carbonization, then acid pickling and drying are conducted, and nickel monatomic catalyst Ni-N-C powder is obtained; the method comprises the following steps: physically mixing nickel monatomic catalyst Ni-N-C powder with urea, and pyrolyzing in an ammonia gas atmosphere to obtain catalyst powder; and dipping the obtained catalyst powder in ammonia water, performing centrifugal separation to obtain a precipitate, dispersing the precipitate in the ammonia water, sealing in a high-pressure reaction kettle, performing heating reaction, centrifuging suspension, washing the precipitate, and performing vacuum drying to obtain the nickel amination-based monatomic catalyst. The catalyst has a porous structure and abundant catalytic reaction activation sites, and has excellent catalytic performance in preparation of CO by reducing CO2 through electro-catalysis.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic materials and relates to a single-atom catalyst based on nickel amide and a preparation method and application thereof. Background Art

[0002] Converting renewable energy sources such as solar, wind and tidal energy into electricity and then using electricity to electro-reduce CO2 to high value-added fuels and chemicals is an effective way to alleviate environmental and energy problems. In recent years, single-atom catalysts have been widely used in these reactions due to their high atomic utilization, but their application has received increasing attention due to their low catalytic activity, mild reaction conditions and other reasons. Currently, cheap Ni-based single-atom catalysts have shown comparable performance to precious metals in the electrochemical reduction of CO2 to CO, but they have the disadvantages of low current density of electrochemical reduction reaction and poor reaction selectivity. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a single-atom catalyst based on nickel amide and a preparation method and application thereof. The catalyst has a porous structure and abundant catalytic reaction activation sites, and has excellent catalytic performance in the electrocatalytic reduction of CO2 to produce CO.

[0004] To achieve the above object, the present invention discloses a method for preparing a nickel amide single-atom catalyst, comprising the following steps:

[0005] 1) dissolving 2-methylimidazole in methanol, and then ultrasonically treating it to obtain a uniformly dispersed solution A; dissolving zinc-nickel metal nitrate hydrate in methanol, and then ultrasonically treating it to obtain a solution B;

[0006] 2) Under magnetic stirring, slowly pour solution B into solution A and stir at room temperature to obtain a mixed solution;

[0007] 3) The mixed solution is centrifuged and washed to obtain Ni 2 The doped ZIF precursor, Ni 2 The doped ZIF precursor was vacuum dried overnight to obtain a purple block precursor;

[0008] 4) grinding the purple block precursor, then sintering and carbonizing it, and then acid washing and drying it to obtain nickel single atom catalyst Ni-NC powder;

[0009] 5) physically mixing nickel single atom catalyst Ni-NC powder with urea, and then pyrolyzing the mixture in an ammonia atmosphere to obtain catalyst powder;

[0010] 6) The catalyst powder obtained in step 5) is immersed in ammonia water, and then centrifuged to obtain a precipitate. The precipitate is dispersed in ammonia water, and then sealed in a high-pressure reactor for heating reaction. The suspension is centrifuged, and the precipitate is washed and then vacuum dried to obtain a nickel amide-based single-atom catalyst.

[0011] The further improvement of the preparation method based on nickel amide single atom catalyst of the present invention is:

[0012] Furthermore, in step 1), the zinc metal nitrate hydrate is a mixture of zinc nitrate hexahydrate and nickel nitrate hexahydrate.

[0013] Furthermore, the molar ratio of zinc nitrate hexahydrate to nickel nitrate hexahydrate is 1:2.

[0014] Furthermore, in step 1), the molar ratio of zinc metal nitrate hydrate to 2-methylimidazole is 1:6.

[0015] Furthermore, in step 4), the sintering temperature is 950-1100°C, and the heating rate is 3-10°C min -1 .

[0016] Furthermore, in step 5), the mass ratio of urea to nickel single atom catalyst Ni-NC powder is 1:40 to 1:60.

[0017] Furthermore, in step 6), the catalyst powder and the impregnated ammonia water are in a ratio of 0.1 g: 30 ml to 50 ml.

[0018] Furthermore, in step 6), the temperature of the heating reaction is 120 to 200° C., and the heating time is 10 to 15 hours.

[0019] The invention discloses a nickel amide-based single-atom catalyst, which is prepared based on a preparation method of the nickel amide-based single-atom catalyst.

[0020] The invention discloses an application of a nickel amide-based single-atom catalyst in the electroreduction of carbon dioxide.

[0021] The present invention has the following beneficial effects:

[0022] The nickel amide single-atom catalyst and its preparation method and application described in the present invention are described in the specific operation. The nickel amide single-atom catalyst obtained by the present invention has a porous structure, has a strong adsorption effect on CO2 molecules, and the nickel element is dispersed at the atomic level, exposing abundant catalytic reaction activation sites. And thanks to the modification of amino-NH2, the carbon carrier in the nickel single-atom catalyst can more effectively improve the catalytic activity of CO2 electrochemical reduction. In addition, the present invention uses the transition metal nickel element as the reaction activation site, avoids the use of precious metals, and greatly reduces the cost of catalyst preparation. At the same time, the preparation process is simple, the reaction conditions are easy to control, which is conducive to large-scale production, and has huge commercial potential and economic value. According to the test, the nickel amide single-atom catalyst prepared by the present invention has a Faraday efficiency of CO product maintained at more than 99% under a wide potential of -0.2 to -1.2V vs.RHE, and has excellent catalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 This is a scanning electron microscope (SEM) image of the nickel amide single atom catalyst obtained in the present invention;

[0025] Figure 2 Schematic diagram of a flow-type electrolytic cell for testing the performance of the catalyst obtained in the present invention for electrocatalytic reduction of CO2 to produce CO;

[0026] Figure 3 This is a Faraday efficiency diagram of the nickel amide single-atom catalyst obtained in the present invention in the preparation of CO by CO2 electroreduction;

[0027] Figure 4 The linear sweep voltammetry (LSV) curve of the nickel amide single-atom catalyst Ni-NC-NH2 obtained in Example 1 in the preparation of CO by CO2 electroreduction;

[0028] Figure 5 This is a linear sweep voltammetry (LSV) diagram of the nickel single-atom catalyst Ni-NC obtained in Example 2 in the preparation of CO by CO2 electroreduction. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0031] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0032] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0033] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0034] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0036] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0037] The preparation method of the nickel amide single-atom catalyst according to the present invention comprises the following steps:

[0038] 1) dissolving 2-methylimidazole in methanol, and then sonicating for 15 minutes to obtain a uniformly dispersed solution A; dissolving zinc-nickel metal nitrate hydrate in methanol, and then sonicating for 15 minutes to obtain a solution B;

[0039] 2) Under magnetic stirring, slowly pour solution B into solution A and stir at room temperature for 24 hours to obtain a mixed solution;

[0040] 3) The mixed solution was centrifuged and then washed with methanol for several times to obtain Ni 2 The doped ZIF precursor, Ni 2 The doped ZIF precursor was placed in a vacuum drying oven and vacuum dried overnight to obtain a purple block precursor;

[0041] 4) Grinding the purple block precursor, placing it in a tube furnace for thermal sintering and carbonization, and then acid washing and drying it to obtain nickel single atom catalyst Ni-NC powder;

[0042] 5) Physically mixing nickel single-atom catalyst Ni-NC powder and urea in a stirring mortar for half an hour, and then pyrolyzing in a tube furnace in an ammonia atmosphere to obtain catalyst powder;

[0043] 6) The catalyst powder obtained in step 5) is immersed in ammonia water for 24 hours, and then centrifuged to obtain a precipitate. The precipitate is dispersed in ammonia water, and then sealed in a high-pressure reactor for heating reaction. The suspension is centrifuged, and the precipitate is washed with deionized water, and then vacuum dried to obtain a nickel amide-based single-atom catalyst (Ni-NC-NH2 catalyst).

[0044] In this embodiment, in step 1), the zinc metal nitrate hydrate is a mixture of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and nickel nitrate hexahydrate (Ni(NO3)2·6H2O), wherein the molar ratio of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) to nickel nitrate hexahydrate (Ni(NO3)2·6H2O) is 1:2, and the molar ratio of zinc metal nitrate hydrate to 2-methylimidazole is 1:6.

[0045] In step 2), the rate of magnetic stirring is 600-900 rpm.

[0046] In step 3), the centrifugal speed is 8000-10000 rpm, the methanol washing times are 2-4 times, the vacuum drying temperature is 50-70° C., and the vacuum drying time is greater than or equal to 20 hours.

[0047] In step 4), the grinding time of the purple block precursor is 10 to 20 minutes, and the temperature of the thermal sintering in the inert atmosphere of the tube furnace is 950 to 1100°C, and the heating rate is 3 to 10°C min -1 , and after heating to the highest temperature, keep the constant temperature for 4 hours and then cool down naturally.

[0048] In step 4), the catalyst powder after hot sintering and carbonization is stirred and pickled in a sulfuric acid or hydrochloric acid solution with a concentration of 1 to 2M, and then stirred and pickled in an oil bath for 8 hours with an oil bath temperature of 60 to 90°C. After heating in the oil bath, the temperature is naturally cooled, and the pickling solution with the catalyst suspension is centrifuged and washed 2 to 4 times with methanol and deionized water, and then vacuum dried overnight at 50 to 70°C.

[0049] In step 5), the mass ratio of urea to nickel single-atom catalyst Ni-NC powder is 1:40 to 1:60, and the ammonia flow rate is 100 ml / min.

[0050] In step 6), the catalyst powder and the impregnated ammonia water are in a ratio of 0.1 g: 30 ml to 50 ml.

[0051] In step 6), the temperature of the heating reaction is 120 to 200° C., and the heating time is 10 to 15 hours.

[0052] The present invention also discloses a nickel amide-based single-atom catalyst, which is prepared based on the preparation method of the nickel amide-based single-atom catalyst, and can be used for carbon dioxide electroreduction.

[0053] Compared with the prior art, the present invention improves the synthesis method of the catalyst. The nickel amide single-atom catalyst prepared by the present invention has the nickel element dispersed at the atomic level and has abundant reaction activation sites. At the same time, the introduction of amino-NH2 promotes the electron transfer at the catalytic reaction interface, thereby improving the reaction rate. The catalyst prepared by the present invention uses transition metal nickel and copper elements as the main raw materials, avoids the use of precious metals, greatly reduces the catalyst preparation cost, and has a simple preparation process, and the reaction conditions are easy to control, which is conducive to large-scale production and has huge commercial potential and economic value.

[0054] Embodiment 1

[0055] The preparation method of the Ni-NC-NH2 catalyst described in this embodiment comprises the following steps:

[0056] Dissolve 1.487g of Zn(NO3)2·6H2O and 2.908g of Ni(NO3)2·6H2 in 200mL of methanol, and dissolve 7.872g of 2-methylimidazole in 100mL of methanol. After ultrasonic dispersion for 15 minutes, mix quickly and stir continuously at 700rpm for 24h at room temperature. After the mixture solution was washed with methanol three times and centrifuged at room temperature, the wet precipitate was dried in a vacuum drying oven at 60℃ overnight, and then ground for 15min to obtain a purple powder; the purple powder was placed in a tubular furnace and heated to 1000℃ at a rate of 3℃ / min in a N2 atmosphere (100mL / min), and maintained for 4 hours. After natural cooling, the obtained black powder was acid-washed with 1M hydrochloric acid solution at 80°C for 8 hours under stirring, washed with methanol and deionized water several times until the solution was neutral, centrifuged at room temperature, and the obtained wet precipitate was dried overnight in a vacuum drying oven at 60°C to obtain Ni-NC catalyst powder;

[0057] Take 0.1g of Ni-NC catalyst powder and 5g of urea and mix them physically in a stirring mortar for half an hour, then pyrolyze them in a tubular furnace with an ammonia atmosphere at a flow rate of 100ml / min, and immerse the catalyst powder obtained by pyrolysis in an appropriate amount of ammonia water in a stirring environment for 24 hours. Then, centrifuge and separate the precipitate. Disperse the precipitate in 35ml of ammonia water, then seal it in a high-pressure reactor, and heat it at 150°C for 12 hours. After heating, centrifuge the suspension, wash the precipitate with deionized water, and obtain the Ni-NC-NH2 catalyst after vacuum drying.

[0058] Embodiment 2

[0059] The preparation method of the Ni-NC catalyst described in this embodiment comprises the following steps:

[0060] Dissolve 1.487g of Zn(NO3)2·6H2O and 2.908g of Ni(NO3)2·6H2 in 200mL of methanol, and dissolve 7.872g of 2-methylimidazole in 100mL of methanol. After ultrasonic dispersion for 15 minutes, mix quickly and stir continuously at room temperature at 700rpm for 24h. After the mixture solution is washed with methanol three times and centrifuged at room temperature, the wet precipitate is dried in a vacuum drying oven at 60℃ overnight, and then ground for 15min to obtain a purple powder. Finally, the purple powder is placed in a tubular furnace and heated to 1000℃ at a rate of 3℃ / min in a N2 atmosphere (100mL / min) and maintained for 4 hours. After natural cooling, the obtained black powder was acid-washed with 1M hydrochloric acid solution at 80°C for 8 hours with stirring, washed with methanol and deionized water multiple times until the solution was neutral, centrifuged at room temperature, and the obtained wet precipitate was dried overnight in a vacuum drying oven at 60°C to obtain a Ni-NC catalyst.

[0061] In an example of testing the catalytic performance of different catalysts in CO2RR.

[0062] A three-electrode measurement was performed using a custom-made flow-type electrolytic cell consisting of a cathode, an anode, and a proton exchange membrane, such as Figure 2 As shown. The anode and proton exchange membrane are made of nickel mesh and Nafion 115 membrane respectively, and the reference electrode is an Ag / AgCl electrode with a saturated KCl solution. A hydrophobic carbon paper with a microporous carbon layer is selected as the cathode, i.e., the working electrode. Isopropanol is used as the organic solvent and 5% Nafion117 is used as the adhesive. When preparing the cathode, a catalyst slurry is prepared according to the ratio of 3mg Ni-NC-NH2 or Ni-NC, 500μL isopropanol and 30μL 5% Nafion117. After ultrasonicating the catalyst slurry for 0.5 hours, the evenly mixed slurry is slowly dripped on the microporous layer side of the 1.5×1.5cm hydrophobic carbon paper using a pipette to form a catalytic layer. The catalyst loading in the catalytic layer is approximately 1mgcm -2 During the drop coating process, the slurry was evenly coated and dried in a dryer. The prepared catalyst-containing electrode carbon paper was then left to stand overnight at room temperature for use. A 1.0M KOH solution was used as the cathode and anode electrolyte. A peristaltic pump was used to control the electrolyte to circulate continuously in the cathode chamber and the anode chamber at a rate of approximately 50 mL min-1, so that the catalyst layer was in contact with the flowing electrolyte. The effective geometric surface area of ​​the electrode was 1 cm 2The flow rate of CO2 entering the cathode side is 50sccm. During the test, the voltage applied to the cathode is -0.2~-1.2V vs.RHE, and the linear scanning voltammetric curves of CO2 electrochemical reduction of different catalysts in this voltage range are recorded, and the gas products are passed into the gas chromatograph for testing and analysis to obtain the Faraday efficiency of CO.

[0063] refer to Figure 1 It can be clearly seen that the nickel amide single atom catalyst Ni-NC-NH2 has a rich porous structure and regular crystal configuration, and has a large number of reaction activation sites.

[0064] refer to Figure 2 The flow-type electrolytic cell consists of a cathode, an anode and a proton exchange membrane. A layer of Nafion 115 proton exchange membrane is sandwiched between two polytetrafluoroethylene plates to isolate the cathode and anode electrolyte chambers.

[0065] refer to Figure 3 The CO Faraday efficiency diagram of the nickel amide single-atom catalyst Ni-NC-NH2 prepared by the present invention is tested in the above-mentioned flow-type electrolytic cell. The Faraday efficiency of the CO product is maintained above 99% under a wide potential of -0.2 to -1.2 V vs. RHE, and the CO selectivity is very outstanding.

[0066] refer to Figure 4 and Figure 5 Compared with the nickel single-atom catalyst Ni-NC at -1.2V vs.RHE, the current density of CO2 electrochemical reduction reaction is 165mAcm -2 , while the reaction current density of Ni-NC-NH2 is 226 mA cm -2 , which is 37% higher than that of Ni-NC, indicating that the introduction of amino-NH2 loading increases the CO2 electrochemical reduction activity, enhances electron transfer, and significantly improves the catalytic performance of the catalyst.

[0067] Embodiment 3

[0068] The preparation method of the nickel amide single-atom catalyst according to the present invention comprises the following steps:

[0069] 1) dissolving 2-methylimidazole in methanol, and then sonicating for 15 minutes to obtain a uniformly dispersed solution A; dissolving zinc-nickel metal nitrate hydrate in methanol, and then sonicating for 15 minutes to obtain a solution B;

[0070] 2) Under magnetic stirring, slowly pour solution B into solution A and stir at room temperature for 24 hours to obtain a mixed solution;

[0071] 3) The mixed solution was centrifuged and then washed with methanol for several times to obtain Ni 2The doped ZIF precursor, Ni 2 The doped ZIF precursor was placed in a vacuum drying oven and vacuum dried overnight to obtain a purple block precursor;

[0072] 4) Grinding the purple block precursor, placing it in a tube furnace for thermal sintering and carbonization, and then acid washing and drying it to obtain nickel single atom catalyst Ni-NC powder;

[0073] 5) Physically mixing nickel single-atom catalyst Ni-NC powder and urea in a stirring mortar for half an hour, and then pyrolyzing in a tube furnace in an ammonia atmosphere to obtain catalyst powder;

[0074] 6) The catalyst powder obtained in step 5) is immersed in ammonia water for 24 hours, and then centrifuged to obtain a precipitate. The precipitate is dispersed in ammonia water, and then sealed in a high-pressure reactor for heating reaction. The suspension is centrifuged, and the precipitate is washed with deionized water, and then vacuum dried to obtain a nickel amide-based single-atom catalyst (Ni-NC-NH2 catalyst).

[0075] In this embodiment, in step 1), the zinc metal nitrate hydrate is a mixture of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and nickel nitrate hexahydrate (Ni(NO3)2·6H2O), wherein the molar ratio of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) to nickel nitrate hexahydrate (Ni(NO3)2·6H2O) is 1:2, and the molar ratio of zinc metal nitrate hydrate to 2-methylimidazole is 1:6.

[0076] In step 2), the rate of magnetic stirring is 600 rpm.

[0077] In step 3), the centrifugal speed is 8000 rpm, the methanol washing times are 2 times, the vacuum drying temperature is 50° C., and the vacuum drying time is greater than or equal to 20 hours.

[0078] In step 4), the grinding time of the purple block precursor is 10 minutes, and the sintering temperature in the inert atmosphere of a tube furnace is 950°C, and the heating rate is 3°C min -1 , and after heating to the highest temperature, keep the constant temperature for 4 hours and then cool down naturally.

[0079] In step 4), the catalyst powder after hot sintering and carbonization is stirred and pickled in a sulfuric acid or hydrochloric acid solution with a concentration of 1M, and then stirred and pickled in an oil bath for 8 hours at an oil bath temperature of 60°C. After heating in the oil bath, the temperature is naturally lowered, and the pickling solution with the catalyst suspension is centrifuged and washed twice with methanol and deionized water, and then vacuum dried at 50°C overnight.

[0080] In step 5), the mass ratio of urea to nickel single atom catalyst Ni-NC powder is 1:40, and the ammonia flow rate is 100 ml / min.

[0081] In step 6), the catalyst powder and the impregnated ammonia water are in a ratio of 0.1 g:30 ml.

[0082] In step 6), the heating reaction temperature is 120° C. and the heating time is 10 hours.

[0083] Embodiment 4

[0084] The preparation method of the nickel amide single-atom catalyst according to the present invention comprises the following steps:

[0085] 1) dissolving 2-methylimidazole in methanol, and then sonicating for 15 minutes to obtain a uniformly dispersed solution A; dissolving zinc-nickel metal nitrate hydrate in methanol, and then sonicating for 15 minutes to obtain a solution B;

[0086] 2) Under magnetic stirring, slowly pour solution B into solution A and stir at room temperature for 24 hours to obtain a mixed solution;

[0087] 3) The mixed solution was centrifuged and then washed with methanol for several times to obtain Ni 2 The doped ZIF precursor, Ni 2 The doped ZIF precursor was placed in a vacuum drying oven and vacuum dried overnight to obtain a purple block precursor;

[0088] 4) Grinding the purple block precursor, placing it in a tube furnace for thermal sintering and carbonization, and then acid washing and drying it to obtain nickel single atom catalyst Ni-NC powder;

[0089] 5) Physically mixing nickel single-atom catalyst Ni-NC powder and urea in a stirring mortar for half an hour, and then pyrolyzing in a tube furnace in an ammonia atmosphere to obtain catalyst powder;

[0090] 6) The catalyst powder obtained in step 5) is immersed in ammonia water for 24 hours, and then centrifuged to obtain a precipitate. The precipitate is dispersed in ammonia water, and then sealed in a high-pressure reactor for heating reaction. The suspension is centrifuged, and the precipitate is washed with deionized water, and then vacuum dried to obtain a nickel amide-based single-atom catalyst (Ni-NC-NH2 catalyst).

[0091] In this embodiment, in step 1), the zinc metal nitrate hydrate is a mixture of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and nickel nitrate hexahydrate (Ni(NO3)2·6H2O), wherein the molar ratio of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) to nickel nitrate hexahydrate (Ni(NO3)2·6H2O) is 1:2, and the molar ratio of zinc metal nitrate hydrate to 2-methylimidazole is 1:6.

[0092] In step 2), the rate of magnetic stirring is 900 rpm.

[0093] In step 3), the centrifugal speed is 10000 rpm, the methanol washing times are 4 times, the vacuum drying temperature is 70° C., and the vacuum drying time is greater than or equal to 20 h.

[0094] In step 4), the grinding time of the purple block precursor is 20 minutes, and the sintering temperature in the inert atmosphere of a tube furnace is 1100°C, and the heating rate is 10°C min -1 , and after heating to the highest temperature, keep the constant temperature for 4 hours and then cool down naturally.

[0095] In step 4), the catalyst powder after hot sintering and carbonization is stirred and pickled in a sulfuric acid or hydrochloric acid solution with a concentration of 2M, and then stirred and pickled in an oil bath for 8 hours at an oil bath temperature of 90°C. After heating in the oil bath, the temperature is naturally cooled. The pickling solution with the catalyst suspension is centrifuged and washed 4 times with methanol and deionized water, and then vacuum dried at 70°C overnight.

[0096] In step 5), the mass ratio of urea to nickel single-atom catalyst Ni-NC powder is 1:60, and the ammonia flow rate is 100 ml / min.

[0097] In step 6), the catalyst powder and the impregnated ammonia water are in a ratio of 0.1 g:50 ml.

[0098] In step 6), the heating reaction temperature is 200° C. and the heating time is 15 hours.

[0099] Embodiment 5

[0100] The preparation method of the nickel amide single-atom catalyst according to the present invention comprises the following steps:

[0101] 1) dissolving 2-methylimidazole in methanol, and then sonicating for 15 minutes to obtain a uniformly dispersed solution A; dissolving zinc-nickel metal nitrate hydrate in methanol, and then sonicating for 15 minutes to obtain a solution B;

[0102] 2) Under magnetic stirring, slowly pour solution B into solution A and stir at room temperature for 24 hours to obtain a mixed solution;

[0103] 3) The mixed solution was centrifuged and then washed with methanol for several times to obtain Ni 2 The doped ZIF precursor, Ni 2 The doped ZIF precursor was placed in a vacuum drying oven and vacuum dried overnight to obtain a purple block precursor;

[0104] 4) Grinding the purple block precursor, placing it in a tube furnace for thermal sintering and carbonization, and then acid washing and drying it to obtain nickel single atom catalyst Ni-NC powder;

[0105] 5) Physically mixing nickel single-atom catalyst Ni-NC powder and urea in a stirring mortar for half an hour, and then pyrolyzing in a tube furnace in an ammonia atmosphere to obtain catalyst powder;

[0106] 6) The catalyst powder obtained in step 5) is immersed in ammonia water for 24 hours, and then centrifuged to obtain a precipitate. The precipitate is dispersed in ammonia water, and then sealed in a high-pressure reactor for heating reaction. The suspension is centrifuged, and the precipitate is washed with deionized water, and then vacuum dried to obtain a nickel amide-based single-atom catalyst (Ni-NC-NH2 catalyst).

[0107] In this embodiment, in step 1), the zinc metal nitrate hydrate is a mixture of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and nickel nitrate hexahydrate (Ni(NO3)2·6H2O), wherein the molar ratio of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) to nickel nitrate hexahydrate (Ni(NO3)2·6H2O) is 1:2, and the molar ratio of zinc metal nitrate hydrate to 2-methylimidazole is 1:6.

[0108] In step 2), the rate of magnetic stirring is 700 rpm.

[0109] In step 3), the centrifugal speed is 9000 rpm, the methanol washing times are 3 times, the vacuum drying temperature is 60° C., and the vacuum drying time is greater than or equal to 20 h.

[0110] In step 4), the grinding time of the purple block precursor is 15 minutes, and the sintering temperature in the inert atmosphere of a tube furnace is 1000°C, and the heating rate is 7°C min -1 , and after heating to the highest temperature, keep the constant temperature for 4 hours and then cool down naturally.

[0111] In step 4), the catalyst powder after hot sintering and carbonization is stirred and pickled in a sulfuric acid or hydrochloric acid solution with a concentration of 1.5M, and then stirred and pickled in an oil bath for 8 hours at an oil bath temperature of 75°C. After heating in the oil bath, the temperature is naturally cooled. The pickling solution with the catalyst suspension is centrifuged and washed three times with methanol and deionized water, and then vacuum dried at 60°C overnight.

[0112] In step 5), the mass ratio of urea to nickel single atom catalyst Ni-NC powder is 1:50, and the ammonia flow rate is 100 ml / min.

[0113] In step 6), the catalyst powder and the impregnated ammonia water are in a ratio of 0.1 g:40 ml.

[0114] In step 6), the heating reaction temperature is 160° C. and the heating time is 13 hours.

[0115] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and disclosure of the invention. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0116] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

[0117] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a nickel amide single-atom catalyst, characterized in that: The following steps are involved: 1) dissolving 2-methylimidazole in methanol, and then ultrasonically treating it to obtain a uniformly dispersed solution A; dissolving zinc-nickel metal nitrate hydrate in methanol, and then ultrasonically treating it to obtain a solution B; 2) Under magnetic stirring, slowly pour solution B into solution A and stir at room temperature to obtain a mixed solution; 3) The mixed solution is centrifuged and washed to obtain Ni 2 The doped ZIF precursor, Ni 2 The doped ZIF precursor was vacuum dried overnight to obtain a purple block precursor; 4) grinding the purple block precursor, then sintering and carbonizing it, and then acid washing and drying it to obtain nickel single atom catalyst Ni-NC powder; 5) physically mixing nickel single atom catalyst Ni-NC powder with urea, and then pyrolyzing the mixture in an ammonia atmosphere to obtain catalyst powder; 6) The catalyst powder obtained in step 5) is immersed in ammonia water, and then centrifuged to obtain a precipitate. The precipitate is dispersed in ammonia water, and then sealed in a high-pressure reactor for heating reaction. The suspension is centrifuged, and the precipitate is washed and then vacuum dried to obtain a nickel amide-based single-atom catalyst.

2. The method for preparing the nickel amide single-atom catalyst according to claim 1, characterized in that: In step 1), the zinc metal nitrate hydrate is a mixture of zinc nitrate hexahydrate and nickel nitrate hexahydrate.

3. The method for preparing the nickel amide single-atom catalyst according to claim 2, characterized in that: The molar ratio of zinc nitrate hexahydrate to nickel nitrate hexahydrate is 1:

2.

4. The method for preparing the nickel amide single-atom catalyst according to claim 1, characterized in that: In step 1), the molar ratio of zinc metal nitrate hydrate to 2-methylimidazole is 1:

6.

5. The method for preparing the nickel amide single-atom catalyst according to claim 1, characterized in that: In step 4), the sintering temperature is 950-1100°C, and the heating rate is 3-10°C min -1 .

6. The method for preparing the nickel amide single-atom catalyst according to claim 1, characterized in that: In step 5), the mass ratio of urea to nickel single atom catalyst Ni-NC powder is 1:40 to 1:

60.

7. The method for preparing the nickel amide single-atom catalyst according to claim 1, characterized in that: In step 6), the catalyst powder and the impregnated ammonia water are in a ratio of 0.1 g: 30 ml to 50 ml.

8. The method for preparing the nickel amide single-atom catalyst according to claim 1, characterized in that: In step 6), the temperature of the heating reaction is 120 to 200° C., and the heating time is 10 to 15 hours.

9. A single-atom catalyst based on nickel amide, characterized in that: The catalyst is prepared based on the method for preparing the nickel amide single-atom catalyst according to any one of claims 1 to 8.

10. Use of the nickel amide-based single-atom catalyst according to claim 9 in the electroreduction of carbon dioxide.

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