Preparation method of monatomic nickel catalyst and application of monatomic nickel catalyst in electrocatalytic carbon dioxide reduction reaction

Abstract

The invention relates to a preparation method of a monatomic nickel catalyst. The preparation method comprises the following steps: activating carbon black by concentrated nitric acid, introducing a polar functional group, cleaning and drying; dispersing the activated carbon black in the solvent and ultrasonically forming uniform liquid; adding a nickel source and a nitrogen source, stirring, centrifuging, drying and grinding to obtain a precursor; and wrapping the precursor on a resistive substrate, and carrying out pulse current high-temperature thermal shock treatment to obtain the catalyst. The invention also relates to application of the monatomic nickel catalyst prepared by the preparation method in electrocatalytic carbon dioxide reduction reaction. Rapid, low-consumption and efficient synthesis is realized through a thermal shock technology, metal agglomeration is avoided, rare earth metal is introduced to synergistically dope to regulate and control an electronic structure of a Ni center, selectivity and stability are both considered, rare earth or transition metal auxiliaries are introduced to regulate and control local charge distribution and regulate and control a Ni-Nx structure, electronic structure adaptation is enhanced, and selectivity is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to electrocatalysis and carbon resource conversion, more particularly to a preparation method of single-atom nickel catalyst and its application in electrocatalytic carbon dioxide reduction reaction. BACKGROUND

[0002] By converting greenhouse gas CO2 into high-value-added chemicals, not only energy storage and regulation can be achieved, but also carbon emission pressure can be alleviated. At present, single-atom catalyst (SAC) has become a research hotspot in this field due to its unique electronic structure, maximum atomic utilization rate and clear catalytic center, which exhibits superior catalytic performance in CO2RR.

[0003] However, the preparation process of the existing single-atom catalyst usually relies on a tube furnace for high-temperature treatment in an inert atmosphere, and the high-temperature sintering time of the catalyst is more than 5 hours. The slow heating rate, high energy consumption, long preparation cycle and other problems not only slow down the actual promotion of the catalyst, but also seriously limit the rapid preparation and large-scale application of the catalyst.

[0004] At the same time, for the existing Ni-based single-atom catalyst, most of them only rely on Ni active centers to participate in the reaction, making it difficult to effectively regulate the CO2 reduction path and intermediate stability, resulting in significant side reactions (such as hydrogen evolution reaction), low catalytic selectivity, and poor cycle stability, which cannot meet the actual needs of efficient electrocatalytic CO2 reduction. SUMMARY

[0005] In order to solve the problems of low preparation efficiency and other problems existing in the prior art, the present application aims to provide a preparation method of single-atom nickel catalyst and its application in electrocatalytic carbon dioxide reduction reaction.

[0006] The preparation method of single-atom nickel catalyst according to the present application comprises the following steps: S1, dispersing carbon black in concentrated nitric acid for activation treatment, introducing polar functional groups on the surface of carbon black through the oxidation of nitric acid, then washing to neutral and drying to obtain activated carbon black; S2, dispersing the activated carbon black in a solvent to form a uniform dispersion liquid by ultrasonic treatment; S3, adding a nickel source and a nitrogen source to the dispersion liquid, wherein the nitrogen source is used to provide a nitrogen ligand to form a stable coordination structure with nickel ions, and after mixing, magnetic stirring, centrifugal separation, drying and grinding treatment, a precursor powder is obtained; S4, wrapping the precursor powder in a resistive base material, placing it in a thermal shock device, and performing high-temperature thermal shock treatment by pulse current in vacuum or inert atmosphere, and through the thermal shock process of rapid heating and cooling, the migration and agglomeration of metal ions are inhibited, and after several cycles, a single-atom nickel catalyst is obtained.

[0007] In a preferred embodiment, step S3 further comprises adding an auxiliary metal salt to the dispersion, and the nitrogen ligand forms a stable coordination structure with nickel ions and auxiliary metal ions, and the molar ratio of the auxiliary metal salt to Ni is 0.5-2:1.

[0008] In a preferred embodiment, the auxiliary metal salt is selected from one or more of ScCl3·6H2O, Y(NO3)3·6H2O, Ce(NO3)3·6H2O, CeCl3·7H2O, Gd(NO3)3·6H2O, Fe(NO3)3·9H2O, Co(NO3)2·6H2O, and Pr(NO3)3·6H2O.

[0009] In a preferred embodiment, in step S1, the carbon black is conductive carbon black, the concentration of the concentrated nitric acid is 8-10 mol / L, and the activation treatment temperature is 80-100°C for 2-4 hours.

[0010] In a preferred embodiment, in step S2, the solvent is selected from one or more of anhydrous ethanol, water, isopropyl alcohol, methanol, and ethylene glycol.

[0011] In a preferred embodiment, in step S3, the nickel source is selected from Ni(NO3)2·6H2O, NiCl2·6H2O, or Ni(CH3COO)2·4H2O, and the nitrogen source is selected from one or more of ethylenediamine, dicyanediamine, L-alanine, 2-methylimidazole, melamine, and urea.

[0012] In a preferred embodiment, in step S4, the electrically resistive base material is selected from nickel sheets, tungsten sheets, titanium sheets, zirconium sheets, rhenium sheets, Inconel alloys, iron-aluminum-chromium alloy foils, carbon cloth, carbon fiber felt, or titanium fiber paper, and the thickness is 0.01-0.05 mm.

[0013] In a preferred embodiment, in step S4, the high-temperature thermal shock treatment temperature is 500-1200°C, the holding time in a single treatment is 5-10 seconds followed by cooling, and the cycle number is 5-20 times; the inert atmosphere is selected from argon, nitrogen, or ammonia; and the pulse current temperature rising time is 1-10 seconds.

[0014] The application of the single-atom nickel catalyst prepared by the above preparation method according to the present application in an electrocatalytic carbon dioxide reduction reaction, wherein the single-atom nickel catalyst generates CO with a Faraday efficiency of ≥94% at a voltage of -0.9 to -1.3 V vs. RHE in the electrocatalytic carbon dioxide reduction reaction.

[0015] In a preferred embodiment, when the single-atom nickel catalyst is gadolinium-doped, the Faraday efficiency of generating CO is close to 100%; and when it is praseodymium-doped, the Faraday efficiency of generating CO is ≥99%.

[0016] The method for preparing a single-atom catalyst according to the present application adopts a high-temperature thermal shock method combined with surface functionalization, auxiliary metal doping and nitrogen source regulation technology to quickly achieve high dispersion anchoring of nickel single atoms and improve the catalytic selectivity and stability thereof. Specifically, the thermal shock technology is used to realize rapid, low-consumption and efficient synthesis, avoid metal agglomeration, introduce rare earth metal for synergistic doping regulation of the electronic structure of the Ni center, and take into account the selectivity and stability, introduce rare earth or transition metal additives to regulate the local charge distribution, regulate the Ni-Nx structure, enhance the electronic structure adaptation, and improve the selectivity. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a synthesis flowchart of a single-atom catalyst according to a preferred embodiment of the present application.

[0018] Figure 2 is a transmission electron microscope image of a nickel single-atom catalyst obtained after high-temperature thermal shock treatment of Example 1.

[0019] Figure 3 is a transmission electron microscope image of a Gd-doped nickel single-atom catalyst obtained after high-temperature thermal shock treatment of Example 2.

[0020] Figure 4 is a scanning electron microscope image of a Y-doped nickel single-atom catalyst obtained after high-temperature thermal shock treatment of Example 4.

[0021] Figure 5 is a scanning electron microscope image of a Co-doped nickel single-atom catalyst obtained after high-temperature thermal shock treatment of Example 7.

[0022] Figure 6 is an LSV curve obtained by passing CO2 into an electrolytic cell and performing CO2 electrocatalytic reduction on the catalyst obtained after high-temperature thermal shock treatment of Examples 1 to 7. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0024] As Figure 1As shown, the method for preparing a single-atom catalyst according to the present invention first includes dispersing carbon black (CB) in concentrated nitric acid for activation treatment. The core purpose of this step is to introduce polar functional groups such as hydroxyl (-OH) and carboxyl (-COOH) groups onto the surface of carbon black through the oxidation of nitric acid, thereby enhancing the adsorption and anchoring ability of carbon black for subsequent metal ions and laying the foundation for the stable dispersion of single atoms. Conductive carbon black can be used. In a preferred embodiment, the conductive carbon black is Vulcan XC-72. The concentration of nitric acid can be in the range of 8 to 10 mol / L. In a preferred embodiment, the concentration of nitric acid is 9 mol / L. The ratio of carbon black to nitric acid can be referenced as 2.0 g of carbon black corresponds to 40 to 100 mL of nitric acid, and the mixture is refluxed at 80 to 100 °C for 2 to 4 hours. In a preferred embodiment, the treatment temperature is 90 °C and the treatment time is 3 hours.

[0025] like Figure 1 As shown, the method for preparing a single-atom catalyst according to the present invention further includes washing the activated carbon black to neutral to obtain activated carbon black. This is to remove residual nitric acid from the activation process, avoid interference from residual acid on the subsequent dissolution or coordination of metal ions, and ensure the stability of the functional groups on the carbon black surface. During operation, the carbon black is repeatedly washed with deionized water until the pH of the filtrate reaches neutral (pH≈7). The washed carbon black is then vacuum-dried at 50–70°C for later use. In a preferred embodiment, the drying temperature is 60°C, and the drying time can be adjusted according to the moisture content.

[0026] like Figure 1 As shown, the method for preparing a single-atom catalyst according to the present invention further includes dispersing activated carbon black in a solvent. This step is to form a uniform suspension system, providing a stable reaction environment for the subsequent addition of nitrogen and metal sources, and ensuring sufficient contact between the components. The selected solvent may include anhydrous ethanol, water, isopropanol, etc. In specific operation, 0.2-0.4 g of activated carbon black can be weighed and added to 80-120 mL of solvent, and uniform dispersion can be achieved by ultrasonic treatment for 20-40 minutes. In a preferred embodiment, the amount of activated carbon black is 0.3 g, the solvent volume is 100 mL, and the ultrasonic time is 30 minutes.

[0027] like Figure 1 As shown, the method for preparing a single-atom catalyst according to the present invention further includes adding a nickel source and a nitrogen source to the dispersed system. The nickel source is used to form a single-atom active center, and the nitrogen source provides a nitrogen ligand to form a stable M–N bond with the metal ion. xThe coordination structure assists in anchoring the metal monatomic atom and inhibits agglomeration during high-temperature treatment. The addition sequence of the nickel source and the nitrogen source can be adjusted according to the system, and the coordination effect can be achieved by adding the two in sequence or simultaneously. The selected nickel source can be selected from Ni(NO3)2·6H2O, NiCl2·6H2O, Ni(CH3COO)2·4H2O, etc., and the amount is 0.15-6 mg in terms of Ni element. The selected nitrogen source includes but is not limited to ethylenediamine, dicyanediamine, L-alanine, 2-methylimidazole, melamine, urea, etc. The amount is 0.6-3 g. In a preferred embodiment, the amount of nitrogen source is adjusted according to the type of solvent and the amount of metal source, such as ethylenediamine 3 g, dicyanediamine 1.5 g, etc. In this process, the addition of auxiliary metal salt can also be included to control the electronic structure by introducing auxiliary metals to improve the catalytic performance. The selected auxiliary metal salt includes salts (such as nitrate, chloride) of scandium (Sc), yttrium (Y), cerium (Ce), gadolinium (Gd), praseodymium (Pr), cobalt (Co), etc. In a preferred embodiment, the auxiliary metal salt includes but is not limited to one or more of ScCl3·6H2O, Y(NO3)3·6H2O, Ce(NO3)3·6H2O, CeCl3·7H2O, Gd(NO3)3·6H2O, Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Pr(NO3)3·6H2O, etc. In a preferred embodiment, the molar ratio of auxiliary metal salt to Ni is 0.5-2:1. In a preferred embodiment, the molar ratio of Gd to Ni is 1:1, and the molar ratio of Pr to Ni is 2:1. In the prior art, carbon dioxide is catalytically reduced to carbon monoxide, and the commonly used metal source is usually a single transition metal. In the catalyst of the present application, one or more of scandium, yttrium, cerium, gadolinium, and praseodymium metals are added in addition to the metal nickel to form a monatomic atom, and through the synergistic effect of multiple metals, the dispersion of the nickel monatomic atom is ensured, and the electrocatalytic performance of the catalyst is improved. Compared with the prior art which has poor catalytic selectivity and stability, the method according to the present application introduces Sc, Y, Ce, Gd, Pr, etc. as auxiliary doping elements to form a multi-metal active center with Ni to control the electronic structure, improve the CO selectivity and inhibit the side reaction ability, and compoundly use ethylenediamine, dicyanediamine, L-alanine, 2-methylimidazole, etc. as nitrogen sources to build different M–Nx coordination structures, improve the electronic coupling strength and interface stability of the metal center, and realize precise regulation of the active center.

[0028] As Figure 1As shown, the method for preparing a single-atom catalyst according to the present application next includes magnetic stirring, centrifugal separation, vacuum drying, and grinding treatment of the mixed system to obtain a precursor powder. The components are fully mixed and reacted by stirring to form a precursor complex, centrifugal separation can remove unreacted impurities, and drying provides a stable solid precursor for subsequent thermal shock treatment. In specific operations, the magnetic stirring time is 2-8 hours. In a preferred embodiment, the stirring time is 4 hours. After centrifugal separation, the solid phase is washed with a solvent and dried at 60-90°C for 12 hours. In a preferred embodiment, the drying temperature is 80°C. Finally, the powder is ground into a powder.

[0029] As shown, the method for preparing a single-atom catalyst according to the present application next includes magnetic stirring, centrifugal separation, vacuum drying, and grinding treatment of the mixed system to obtain a precursor powder. The components are fully mixed and reacted by stirring to form a precursor complex, centrifugal separation can remove unreacted impurities, and drying provides a stable solid precursor for subsequent thermal shock treatment. In specific operations, the magnetic stirring time is 2-8 hours. In a preferred embodiment, the stirring time is 4 hours. After centrifugal separation, the solid phase is washed with a solvent and dried at 60-90°C for 12 hours. In a preferred embodiment, the drying temperature is 80°C. Finally, the powder is ground into a powder. Figure 1 As shown, the method for preparing a single-atom catalyst according to the present application next includes magnetic stirring, centrifugal separation, vacuum drying, and grinding treatment of the mixed system to obtain a precursor powder. The components are fully mixed and reacted by stirring to form a precursor complex, centrifugal separation can remove unreacted impurities, and drying provides a stable solid precursor for subsequent thermal shock treatment. In specific operations, the magnetic stirring time is 2-8 hours. In a preferred embodiment, the stirring time is 4 hours. After centrifugal separation, the solid phase is washed with a solvent and dried at 60-90°C for 12 hours. In a preferred embodiment, the drying temperature is 80°C. Finally, the powder is ground into a powder. x As shown, the method for preparing a single-atom catalyst according to the present application next includes magnetic stirring, centrifugal separation, vacuum drying, and grinding treatment of the mixed system to obtain a precursor powder. The components are fully mixed and reacted by stirring to form a precursor complex, centrifugal separation can remove unreacted impurities, and drying provides a stable solid precursor for subsequent thermal shock treatment. In specific operations, the magnetic stirring time is 2-8 hours. In a preferred embodiment, the stirring time is 4 hours. After centrifugal separation, the solid phase is washed with a solvent and dried at 60-90°C for 12 hours. In a preferred embodiment, the drying temperature is 80°C. Finally, the powder is ground into a powder.

[0030] Example 1 Preparation of a Ni single-atom catalyst

[0031] Carbon black pretreatment: Take 2.0 g of conductive carbon black (such as Vulcan XC-72), add 50 mL of 9 mol / L concentrated nitric acid solution; reflux treatment in 90°C water bath for 2 hours; after treatment, wash with deionized water to neutral, 60°C vacuum drying for standby.

[0032] Precursor preparation: take 0.3 g of carbon black pretreated in step (1) in 100 mL of anhydrous ethanol, ultrasonic for 30 minutes to form a dispersion, add 0.1 mmol of nickel nitrate dissolved in ethanol; add 3 g of ethylenediamine as a nitrogen source, stir for 2 hours, and then dry at 60°C to obtain a precursor complex.

[0033] Thermal shock treatment: the dry powder is evenly wrapped in a 0.02 mm thick nickel foil, and placed between the two electrode platforms of a rapid heating furnace. After vacuumizing the inside of the furnace, an argon atmosphere is introduced. A current of 30-50 A is applied to achieve a thermal shock treatment of 500-700°C, and the temperature is kept constant for 5 seconds. After cooling for 30 seconds, the operation of applying current, constant temperature and cooling is repeated for 5-10 times, and finally the Ni-NC single atom nickel catalyst is obtained.

[0034] Figure 2 is the transmission electron microscope image of the obtained Ni-NC single atom nickel catalyst. It can be observed from the figure that the Ni single atom is coordinated with nitrogen (Ni-N x ) to achieve atomic dispersion and stable anchoring of the Ni single atom.

[0035] Performance test: in the performance test of electrochemical reduction of carbon dioxide, the Faraday efficiency of CO can reach more than 97% at-0.9 to-1.3 V vs. RHE.

[0036] Example 2 Preparation of Gd-doped Ni single atom catalyst

[0037] Carbon black pretreatment: take 2.0 g of conductive carbon black and add it to 100 mL of 9 mol / L concentrated nitric acid, reflux at 90°C for 3 hours; wash with deionized water several times until the pH is about 7, and then vacuum dry at 60°C for standby.

[0038] Precursor synthesis: take 0.3 g of pretreated carbon black and add it to 100 mL of an ethanol:water = 1:1 system, ultrasonic for 30 minutes to form a uniform dispersion; add 1.5 g of dicyanediamine as a nitrogen source after dissolution; add 14.54 mg of Ni(NO3)2·6H2O (about 2.93 mg of Ni); then add 22.52 mg of Gd(NO3)3·6H2O (consistent with the molar amount of Ni); after magnetic stirring for 4 hours, centrifuge the solid phase, and dry the solid phase at 80°C under vacuum for 12 hours, and then grind to obtain a precursor powder.

[0039] Thermal shock treatment: the precursor powder is uniformly wrapped in 0.01-0.03 mm thick Inconel alloy sheet, and placed between the two electrode platforms of the fast furnace, and the air inside the fast furnace is vacuumized; pulse current is applied to rapidly raise the temperature to 600-800℃, and after maintaining for 10 seconds, natural cooling is performed, and the heating cycle is repeated for 5-15 times to obtain the Ni-Gd-NC catalyst.

[0040] Figure 3 Figure is a transmission electron microscope image of the obtained Ni-Gd-NC catalyst. As can be observed from the figure, Ni and Gd are uniformly dispersed, and no obvious metal particle aggregation is found.

[0041] Performance test: in the carbon dioxide electrochemical reduction performance test, the Faraday efficiency of CO is close to 100% at -0.9 to -1.3 V vs. RHE.

[0042] Example 3 Preparation of Sc-doped Ni monatomic catalyst

[0043] Carbon black pretreatment: 2.0 g of conductive carbon black is added to 100 mL of 9 mol / L concentrated nitric acid, and refluxed at 90℃ for 3 hours; washed with deionized water for several times until the pH is about 7, and vacuum dried at 60℃ for standby.

[0044] Precursor synthesis: 0.3 g of the pretreated carbon black is added to 100 mL of water, and ultrasonic treatment is performed for 30 minutes to form a uniform dispersion; 1.08 g of urea is added as a nitrogen source and dissolved; 5.70 mg of NiCl2·6H2O (about 1.41 mg of Ni) is added; 9.33 mg of ScCl3·6H2O (1.5 times the molar amount of Ni metal) is added; after magnetic stirring for 4 hours, the solid phase is separated by centrifugation, and the solid phase is vacuum dried at 80℃ for 12 hours, and ground to obtain the precursor powder.

[0045] Thermal shock treatment: the precursor powder is uniformly wrapped in 0.01-0.03 mm thick tungsten metal foil, and placed between the two electrode platforms of the fast furnace, and the fast furnace is vacuumized and then filled with argon atmosphere; pulse current is applied to rapidly raise the temperature to 700-1000℃, and after maintaining for 10 seconds, natural cooling is performed, and the heating cycle is repeated for 5-15 times to obtain the Ni-Sc-NC catalyst.

[0046] Performance test: in the carbon dioxide electrochemical reduction performance test, the Faraday efficiency of CO can reach more than 96% at -0.9 to -1.3 V vs. RHE.

[0047] Example 4 Preparation of Y-doped Ni monatomic catalyst

[0048] Carbon black pretreatment: 2.0 g of conductive carbon black was added to 100 mL of 9 mol / L concentrated nitric acid, and refluxed at 90°C for 3 hours; washed with deionized water several times until the pH was about 7, and vacuum dried at 60°C for standby.

[0049] Precursor synthesis: 0.3 g of pretreated carbon black was added to 100 mL of methanol, and ultrasonic for 30 minutes to form a uniform dispersion; 2.27 g of melamine was added as a nitrogen source after dissolution; 14.86 mg of Ni(NO3)2·6H2O (about 3.00 mg of Ni) was added; 9.79 mg of Y(NO3)3·6H2O (0.5 times the molar amount of Ni metal) was added; after magnetic stirring for 4 hours, the solid phase was separated by centrifugation, and the solid phase was vacuum dried at 80°C for 12 hours, and ground to obtain a precursor powder.

[0050] Thermal shock treatment: the precursor powder was uniformly wrapped in a 0.01-0.03 mm thick rhenium metal foil, and placed between the two electrode platforms of a rapid firing furnace; after vacuumizing the inside of the rapid firing furnace, argon gas was introduced; a pulse current was applied to rapidly raise the temperature to 700-900°C, and after maintaining for 10 seconds, it was naturally cooled, and the cycle was repeated for 10-20 times to obtain a Ni-Y-NC catalyst.

[0051] Figure 4 is a scanning electron microscope image of the obtained Ni-Y-NC catalyst. As can be observed from the figure, the catalyst as a whole has a loose and porous carbon-based structure, and Ni and Y are uniformly dispersed, and no obvious metal particle aggregation is found.

[0052] Performance test: in the performance test of electrochemical reduction of carbon dioxide, the Faraday efficiency of CO can reach more than 95% at-0.9 to-1.3 V vs. RHE.

[0053] Example 5 Preparation of Ce-doped Ni single-atom catalyst

[0054] Carbon black pretreatment: 2.0 g of conductive carbon black was added to 100 mL of 9 mol / L concentrated nitric acid, and refluxed at 90°C for 3 hours; washed with deionized water several times until the pH was about 7, and vacuum dried at 60°C for standby.

[0055] Precursor synthesis: 0.3 g of pretreated carbon black was added to 100 mL of water, and ultrasonic for 30 minutes to form a uniform dispersion; 1.78 g of L-alanine was added as a nitrogen source after dissolution; 20.25 mg of NiCl2·6H2O (about 5.00 mg of Ni) was added; 47.61 mg of CeCl3·7H2O (1.5 times the molar amount of Ni metal) was added; after magnetic stirring for 4 hours, the solid phase was separated by centrifugation, and the solid phase was vacuum dried at 80°C for 12 hours, and ground to obtain a precursor powder.

[0056] Thermal shock treatment: the precursor powder is uniformly wrapped in a 0.01-0.03 mm thick zirconium sheet metal foil, and placed between the two electrode platforms of a rapid firing furnace. After vacuumizing the inside of the rapid firing furnace, an ammonia gas atmosphere is introduced. A pulse current is applied to rapidly raise the temperature to 1000-1200°C, and after maintaining for 10 seconds, natural cooling is performed. The heating cycle is repeated 10-20 times to obtain the Ni-Ce-NC catalyst.

[0057] Performance test: in the carbon dioxide electrochemical reduction performance test, the Faraday efficiency of CO can reach more than 97% at -0.9 to -1.3 V vs. RHE.

[0058] Example 6 Preparation of Pr-doped Ni monatomic catalyst

[0059] Carbon black pretreatment: 2.0 g of conductive carbon black is added to 100 mL of 9 mol / L concentrated nitric acid, and refluxed at 90°C for 3 hours. It is washed with deionized water several times until the pH is about 7, and vacuum dried at 60°C for standby use.

[0060] Precursor synthesis: 0.3 g of the pretreated carbon black is added to 100 mL of ethylene glycol, and ultrasonically dispersed for 30 minutes to form a uniform dispersion; 1.48 g of 2-methylimidazole is added as a nitrogen source and dissolved; 1.02 mg of Ni(CH3COO)2·4H2O (about 0.24 mg of Ni) is added; 3.56 mg of Pr(NO3)3·6H2O (2.0 times the molar amount of Ni metal) is added; after magnetic stirring for 4 hours, the solid phase is separated by centrifugation, and the solid phase is vacuum dried at 80°C for 12 hours. The precursor powder is obtained by grinding.

[0061] Thermal shock treatment: the precursor powder is uniformly wrapped in a 0.01-0.03 mm thick carbon cloth, and placed between the two electrode platforms of a rapid firing furnace. After vacuumizing the inside of the rapid firing furnace, a nitrogen gas atmosphere is introduced. A pulse current is applied to rapidly raise the temperature to 900-1100°C, and after maintaining for 10 seconds, natural cooling is performed. The heating cycle is repeated 10-15 times to obtain the Ni-Pr-NC catalyst.

[0062] Performance test: in the carbon dioxide electrochemical reduction performance test, the Faraday efficiency of CO can reach more than 99% at -0.9 to -1.3 V vs. RHE.

[0063] Example 7 Preparation of Co-doped Ni monatomic catalyst

[0064] Carbon black pretreatment: 2.0 g of conductive carbon black is added to 100 mL of 9 mol / L concentrated nitric acid, and refluxed at 90°C for 3 hours. It is washed with deionized water several times until the pH is about 7, and vacuum dried at 60°C for standby use.

[0065] Precursor synthesis: 0.3 g of pretreated carbon black was added to 100 mL of water and ultrasonically dispersed for 30 minutes to form a uniform dispersion; 1.5 g of dicyandiamide was added as a nitrogen source and dissolved; 14.54 mg of Ni(NO3)2·6H2O (about 2.93 mg of Ni) was added; 14.55 mg of Co(NO3)2·6H2O (consistent with the molar amount of Ni) was added; after magnetic stirring for 4 hours, the solid phase was separated by centrifugation, and the solid phase was dried at 80°C under vacuum for 12 hours, and then ground to obtain a precursor powder.

[0066] Thermal shock treatment: the precursor powder was uniformly wrapped in a 0.01-0.03 mm thick nickel foil sheet and placed between the two electrode platforms of a rapid firing furnace, and the air inside the furnace was subjected to vacuum treatment; a pulse current was applied to rapidly raise the temperature to 600-800°C, and after maintaining for 10 seconds, the temperature was naturally cooled, and the cycle was repeated 5-15 times to obtain a Ni-Co-NC catalyst.

[0067] Figure 5 is a scanning electron microscope image of the obtained Ni-Co-NC catalyst. As can be observed from the figure, the catalyst has a loose and porous carbon-based structure, and Ni and Co are uniformly dispersed, and no obvious large particle metal aggregates are found.

[0068] Performance test: in the electrochemical reduction performance test of carbon dioxide, the Faraday efficiency of CO can reach more than 94% at -0.9 to -1.3 V vs. RHE.

[0069] Figure 6 is the LSV curve of the catalyst obtained by high-temperature thermal shock treatment of Examples 1-7. As can be observed from the figure, the current of the CO2 electrocatalytic reduction reaction in the curve is represented by a negative value, and the greater the absolute value of the current density (the lower the curve), the higher the catalytic activity. The catalysts in the above examples all have good catalytic activity.

[0070] The present application solves the problems of structural instability, complex preparation, poor performance and weak application adaptability of traditional Ni single-atom catalysts through integrated design, and provides a novel, efficient and practical technical path for realizing efficient utilization of CO2 electrocatalysis. The present application aims to provide an efficient synthesis method of metal-doped Ni single-atom catalyst for electrocatalytic carbon dioxide reduction reaction. The method realizes in-situ construction of Ni single-atom active sites on carbon-based carriers by means of precursor design, carbon black surface functionalization, multi-nitrogen source synergistic doping and auxiliary metal introduction, combined with high-temperature thermal shock technology, and regulates the coordination environment and electronic structure of the catalyst, thereby improving the reaction selectivity, stability and atomic utilization efficiency of the catalyst, and solving the problems of metal aggregation, complex preparation process, weak structure control and poor catalytic performance in the synthesis process of existing catalysts. In particular, the activated carbon black with nitric acid is used to introduce polar functional groups such as hydroxyl and carboxyl groups, to enhance the adsorption and anchoring ability of metal ions; the electronic structure is regulated by nitrogen source synergistic effect and rare earth metal doping to enhance the faradic efficiency of carbon monoxide in the electrochemical reduction of carbon dioxide; the high-temperature thermal shock process is used to realize rapid heating, and the combination of precursor and high-resistance material forms the rapid heating of thermal shock method, which effectively reduces metal aggregation and realizes Ni single-atom anchoring; it is suitable for green energy conversion scenarios such as electrocatalytic carbon dioxide reduction reaction (CO2RR), and belongs to the preparation technology of new single-atom electrocatalytic materials.

[0071] The above is only a preferred embodiment of the present application, and is not intended to limit the scope of the present application. The above embodiment of the present application can be variously changed. Any simple, equivalent changes and modifications made in accordance with the content of the claims and description of the present application fall within the scope of the present application. The present application is not described in detail.

Claims

1. A method for producing a monatomic nickel catalyst, characterized by, The preparation method comprises the following steps: S1, the carbon black is dispersed in concentrated nitric acid for activation treatment, and polar functional groups are introduced on the surface of the carbon black by the oxidation of nitric acid, and then washed to neutral and dried to obtain activated carbon black; S2, the activated carbon black is dispersed in a solvent to form a uniform dispersion liquid by ultrasonic treatment; S3, a nickel source and a nitrogen source are added to the dispersion liquid, wherein the nitrogen source is used to provide a nitrogen ligand to form a stable coordination structure with nickel ions, and after mixing, magnetic stirring, centrifugal separation, drying and grinding treatment are performed to obtain a precursor powder; S4, the precursor powder is wrapped in a resistive base material, placed in a thermal shock device, and subjected to high-temperature thermal shock treatment by pulse current in a vacuum or inert atmosphere, and the thermal shock process of rapid heating and cooling is used to inhibit the migration and agglomeration of metal ions, and the cycle operation is repeated for several times to obtain a single-atom nickel catalyst.

2. The production method according to claim 1, characterized by, In step S3, an auxiliary metal salt is also added to the dispersion liquid, and the nitrogen ligand forms a stable coordination structure with nickel ions and auxiliary metal ions, and the molar ratio of the auxiliary metal salt to Ni is 0.5-2:

1.

3. The production method according to claim 2, characterized by, The auxiliary metal salt is selected from one or more of ScCl3·6H2O, Y(NO3)3·6H2O, Ce(NO3)3·6H2O, CeCl3·7H2O, Gd(NO3)3·6H2O, Fe(NO3)3·9H2O, Co(NO3)2·6H2O, and Pr(NO3)3·6H2O.

4. The method of claim 1, wherein, In step S1, the carbon black is conductive carbon black, the concentration of the concentrated nitric acid is 8-10 mol / L, and the activation treatment is performed at a temperature of 80-100°C for 2-4 hours.

5. The preparation method according to claim 1, characterized in that, In step S2, the solvent is selected from one or more of anhydrous ethanol, water, isopropyl alcohol, methanol, and ethylene glycol.

6. The method of claim 1, wherein, In step S3, the nickel source is selected from Ni(NO3)2·6H2O, NiCl2·6H2O, or Ni(CH3COO)2·4H2O, and the nitrogen source is selected from one or more of ethylenediamine, dicyanediamine, L-alanine, 2-methylimidazole, melamine, or urea.

7. The preparation method according to claim 1, characterized in that, In step S4, the resistive base material is selected from nickel sheets, tungsten sheets, titanium sheets, zirconium sheets, rhenium sheets, Inconel alloys, iron-aluminum-chromium alloy foils, carbon cloth, carbon fiber felt, or titanium fiber paper, and the thickness is 0.01-0.05 mm.

8. The method of claim 1, wherein, In step S4, the high-temperature thermal shock treatment is performed at a temperature of 500-1200°C, and the holding time in a single treatment is 5-10 seconds followed by cooling, and the cycle number is 5-20 times; the inert atmosphere is selected from argon, nitrogen, or ammonia; and the temperature rising time of the pulse current is 1-10 seconds.

9. Use of the monatomic nickel catalyst prepared according to the preparation method of any one of claims 1-8 in electrocatalytic carbon dioxide reduction reaction, characterized in that, The single-atom nickel catalyst generates CO with a Faraday efficiency of ≥94% at a voltage of -0.9 to -1.3 V vs. RHE in an electrocatalytic carbon dioxide reduction reaction.

10. Use according to claim 9, characterized in that, When the single-atom nickel catalyst is gadolinium-doped, the Faraday efficiency of generating CO is close to 100%; and when it is praseodymium-doped, the Faraday efficiency of generating CO is ≥99%.

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