Sulfur-doped nickel monatomic catalyst as well as preparation method and application thereof

Abstract

The invention provides a sulfur-doped nickel monatomic catalyst, and the sulfur-doped nickel monatomic catalyst is obtained by etching a molecular sieve of a molecular sieve precursor loaded with sulfur, nickel and carbon. The invention belongs to the technical field of metal monatomic catalyst preparation. According to the preparation method, sulfur atoms are doped on a nickel monatomic material, adsorption of a carbon dioxide reduction intermediate is adjusted, the performance of electrically reducing carbon dioxide into carbon monoxide is enhanced, nickel, nitrogen and sulfur elements are uniformly distributed on a carbon carrier with a large surface area, and relatively high catalytic efficiency and excellent stability are obtained under high current density. The invention also provides a preparation method of the sulfur-doped nickel monatomic catalyst, and the prepared catalyst has excellent performance of catalyzing carbon dioxide to be electrically reduced into carbon monoxide, and has industrial-grade current density and extremely excellent carbon monoxide Faraday efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of metal single-atom catalyst preparation, and relates to a sulfur-doped nickel single-atom catalyst and a preparation method and application thereof. Background Art

[0002] The rapid development of society has led to a significant increase in greenhouse gas emissions, which has had a significant impact on the global climate and caused frequent extreme weather events. The contradiction between development and protection is a major problem that plagues the world. In order to achieve sustainable development, it is necessary to reduce the amount of carbon dioxide (CO 2 ) as a valuable carbon resource, and use renewable energy to convert it into chemicals, thereby establishing an artificial carbon cycle. In the past few decades, renewable energy technologies such as wind power and hydropower have made significant progress. However, renewable energy sources such as wind, solar and hydropower are intermittently generated and difficult to be directly connected to the power grid, resulting in a large amount of electricity waste. In addition, the mismatch between supply and demand may lead to excess electricity. If excess electricity can be flexibly used to drive the catalytic conversion of carbon dioxide, not only can electrical energy be converted into chemical energy and stored, but also carbon dioxide can be utilized as a resource, and it will help to rationalize the relationship between supply and demand, significantly improve the utilization rate of power equipment and enhance the stability of the power grid.

[0003] Electrocatalytic carbon dioxide reduction is an effective method to solve the problem of excessive carbon dioxide emissions and balance the peak fluctuations of renewable electricity. For electrocatalytic carbon dioxide reduction, carbon monoxide in the gas product is the most valuable product and is also favored by many researchers. In the carbon dioxide electroreduction reaction, metal nanocatalysts have been widely studied because of their easy regulation of electronic states and diverse element combinations; some other precious metal catalysts also have extremely excellent performance, with catalytic activity far exceeding that of ordinary metals, and are also used in the study of carbon dioxide electroreduction. However, since only the surface atoms of the catalyst can participate in the catalytic reaction, the atomic utilization rate is low, resulting in metal waste. In order to solve this problem, single-atom catalysts have gradually become an emerging research hotspot in recent years. Compared with metal nanocatalysts, it can achieve performance that is not inferior to that of metal nanocatalysts with fewer metal elements; on the other hand, due to the easy adjustment of the coordination structure of single-atom catalysts and the simple composition of active centers, single-atom catalysts are widely used in theoretical research on carbon dioxide electroreduction. However, studies have shown that such single-atom catalysts, such as Ni-NC materials, have excellent selectivity for catalyzing the reduction of carbon dioxide to carbon monoxide, but due to the intrinsic activity or physical properties of the material, it is difficult for nickel single-atom materials to achieve stable operation at high current density.

[0004] Therefore, how to design a more suitable metal catalyst to solve the above-mentioned problems of existing catalysts has broad application prospects and is also one of the focuses of attention of many researchers in the industry. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a sulfur-doped nickel single-atom catalyst, its preparation method and application. The catalyst provided by the present invention is a sulfur-doped mesoporous carbon material loaded with different concentrations of nickel atoms, which has a large surface area and intrinsic activity, and can achieve high-selectivity and high-activity conversion of carbon dioxide to carbon monoxide. Moreover, the preparation method is simple, the conditions are mild, the controllability is strong, and it is more suitable for the popularization and application of industrial production.

[0006] The present invention provides a sulfur-doped nickel single-atom catalyst, which is obtained by etching off a molecular sieve after a molecular sieve precursor loaded with sulfur, nickel and carbon.

[0007] Preferably, the molecular sieve precursor loaded with sulfur, nickel and carbon is obtained by calcining a molecular sieve precursor loaded with thiourea, a nickel source and phenanthroline;

[0008] In the molecular sieve precursor loaded with thiourea, a nickel source and phenanthroline, nickel ions form a complex with phenanthroline;

[0009] The molecular sieve includes a mesoporous molecular sieve;

[0010] The mesoporous molecular sieve includes one or more of SBA-15 molecular sieve, SBA-16 molecular sieve, KIT-6 molecular sieve, MCM-41 molecular sieve and MCM-41 molecular sieve.

[0011] Preferably, in the microstructure of the sulfur-doped nickel single-atom catalyst, it has a hexagonal columnar structure;

[0012] In the sulfur-doped nickel single-atom catalyst, the mass content of nickel is 1.7% - 2.7%;

[0013] In the sulfur-doped nickel single-atom catalyst, the mass content of sulfur is 3.0% - 4.7%;

[0014] The particle size of the sulfur-doped nickel single-atom catalyst is 0.2 - 1 μm.

[0015] The present invention provides a preparation method of a sulfur-doped nickel single-atom catalyst, which includes the following steps:

[0016] 1) Dissolve a nickel salt in an organic solvent to obtain solution A;

[0017] Dissolve thiourea in an organic solvent to obtain solution B, and then add phenanthroline to obtain solution C;

[0018] 2) Slowly add solution A obtained in the above step to solution C while mixing to obtain a mixed solution D;

[0019] 3) After remixing the obtained mixed solution D with the molecular sieve and then calcining, the resulting powder is placed in a hydrofluoric acid solution for etching reaction to obtain a sulfur-doped nickel single-atom catalyst.

[0020] Preferably, the nickel salt includes nickel nitrate hexahydrate;

[0021] The organic solvent includes ethanol;

[0022] In the solution A, the concentration of the nickel salt is 1.2 - 2.1 g / L;

[0023] In the solution B, the concentration of thiourea is 10 - 40 g / L.

[0024] Preferably, the mass ratio of o-phenanthroline to thiourea is 4:(2 - 3);

[0025] The mass ratio of the nickel salt to thiourea is (0.16 - 0.2):(0.2 - 0.3);

[0026] The slow addition method includes injection;

[0027] The slow addition rate is 5 - 10 mL / h.

[0028] Preferably, the mixing method includes stirring;

[0029] The mixing speed is 500 - 1500 rpm;

[0030] The molecular sieve includes mesoporous molecular sieve SBA-15;

[0031] The mass ratio of the molecular sieve to the nickel salt is (0.2 - 0.5):(0.15 - 0.21).

[0032] Preferably, the time for the re-mixing is 10 - 30 min;

[0033] After the re-mixing, it also includes a rotary evaporation and / or drying step;

[0034] The temperature of the rotary evaporation is 40 - 60 °C;

[0035] The rotation speed of the rotary evaporation is 0.5 - 2 rpm;

[0036] The calcination is specifically carried out under a protective atmosphere.

[0037] Preferably, the heating rate of the calcination is 5 - 10 °C / min;

[0038] The temperature of the calcination is 600 - 1000 °C;

[0039] The calcination time is 1 to 4 h;

[0040] The mass concentration of the hydrofluoric acid solution is 5% to 15%;

[0041] The etching reaction time is 0.5 to 4 hours.

[0042] The present invention also provides the application of the sulfur-doped nickel single-atom catalyst described in any one of the above technical solutions or the sulfur-doped nickel single-atom catalyst prepared by the preparation method described in any one of the above technical solutions in electrocatalytic carbon dioxide reduction.

[0043] The present invention provides a sulfur-doped nickel single-atom catalyst, which is obtained by etching off the molecular sieve from a molecular sieve precursor loaded with sulfur, nickel and carbon. Compared with the prior art, the present invention creatively designs a sulfur-doped nickel single-atom catalyst with a specific structure and composition. By doping sulfur atoms on the nickel single-atom material, the adsorption of carbon dioxide reduction intermediates is adjusted, the performance of electro-reducing carbon dioxide to carbon monoxide is enhanced, and nickel, nitrogen, and sulfur elements are evenly distributed on a carbon carrier with a large surface area, and high catalytic efficiency and excellent stability are obtained at a large current density.

[0044] The present invention also provides a corresponding preparation method. An ethanol solution of nickel nitrate is injected into an ethanol solution of thiourea and o-phenanthroline at a certain flow rate and ratio and stirred. After stirring, it is rotary evaporated until most of the solvent volatilizes, and then placed in a vacuum oven for further drying. The dried solid is placed in a tubular furnace under an argon atmosphere for sufficient pyrolysis to obtain a sulfur-doped nickel single-atom catalyst. The catalyst prepared by the present invention has excellent performance in electrocatalytic reduction of carbon dioxide to carbon monoxide, with an industrial-grade current density and extremely excellent carbon monoxide Faraday efficiency.

[0045] Experimental results show that the sulfur-doped nickel single-atom catalyst prepared by the present invention has excellent electrochemically carbon dioxide reduction performance. When applied to a flow cell, a carbon monoxide Faraday efficiency of more than 99% is achieved at a large current density of 100 to 800 mA / cm². Moreover, during the constant current electrolysis process of nearly 10 hours, the selectivity, activity and electrolysis potential of the electrocatalyst do not decrease significantly, and the stability is good. Description of the Drawings

[0046] Figure 1 Transmission electron microscope images of different scales of the sulfur-doped nickel single-atom catalyst prepared in Example 1 of the present invention; among them, (a) is a transmission electron microscope image of 200 nm, and (b) is a transmission electron microscope image of 100 nm.

[0047] Figure 2Element mapping images of sulfur-doped nickel single-atom catalyst prepared in Example 1 of the present invention by scanning electron microscope; among them, (a) is the carbon element mapping image, (b) is the nitrogen element mapping image, (c) is the nickel element mapping image, and (d) is the sulfur element mapping image.

[0048] Figure 3 Electron diffraction pattern and high-resolution transmission electron microscope image of sulfur-doped nickel single-atom catalyst prepared in Example 1 of the present invention; among them, (a) is the electron diffraction pattern and (b) is the high-resolution transmission electron microscope image.

[0049] Figure 4 High-angle annular dark-field scanning transmission electron microscope image of sulfur-doped nickel single-atom catalyst prepared in Example 1 of the present invention;

[0050] Figure 5 X-ray diffraction pattern of sulfur-doped nickel single-atom catalyst prepared in Example 1 of the present invention;

[0051] Figure 6 Specific surface area test curve of sulfur-doped nickel single-atom catalyst prepared in Example 1 of the present invention;

[0052] Figure 7 Results of the Faraday efficiency of each product and the relative standard hydrogen electrode potential at different current densities in the electrocatalytic reduction of carbon dioxide by the sulfur-doped nickel single-atom catalyst prepared in Example 1 of the present invention. Detailed implementation manners

[0053] To further understand the present invention, the preferred implementation manners of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the claims of the present invention.

[0054] For all raw materials of the present invention, there is no special limitation on their sources, and they can be purchased on the market or prepared by conventional methods well-known to those skilled in the art.

[0055] For all raw materials of the present invention, there is no special limitation on their purity. The present invention preferably uses analytical pure or the purity conventional in the field of single-atom catalyst preparation.

[0056] The present invention provides a sulfur-doped nickel single-atom catalyst, which is obtained by etching off the molecular sieve from a molecular sieve precursor loaded with sulfur, nickel, and carbon.

[0057] In the present invention, the molecular sieve precursor loaded with sulfur, nickel, and carbon is preferably obtained by calcining a molecular sieve precursor loaded with thiourea, nickel source, and o-phenanthroline.

[0058] In the present invention, in the molecular sieve precursor loaded with thiourea, nickel source and phenanthroline, it is preferred that nickel ions form a complex with phenanthroline.

[0059] In the present invention, the molecular sieve preferably includes a mesoporous molecular sieve.

[0060] In the present invention, the mesoporous molecular sieve preferably includes one or more of SBA-15 molecular sieve, SBA-16 molecular sieve, KIT-6 molecular sieve, MCM-41 molecular sieve and MCM-41 molecular sieve, and more preferably is SBA-15 molecular sieve, SBA-16 molecular sieve, KIT-6 molecular sieve, MCM-41 molecular sieve or MCM-41 molecular sieve.

[0061] In the microstructure of the sulfur-doped nickel single-atom catalyst of the present invention, it preferably has a hexagonal columnar structure.

[0062] In the sulfur-doped nickel single-atom catalyst of the present invention, the mass content of nickel is preferably 1.7% - 2.7%, more preferably 2.0% - 2.7%, more preferably 2.3% - 2.7%, and more preferably 2.5% - 2.7%.

[0063] In the sulfur-doped nickel single-atom catalyst of the present invention, the mass content of sulfur is preferably 3.0% - 4.7%, more preferably 3.4% - 4.3%, and more preferably 3.8% - 3.9%.

[0064] In the sulfur-doped nickel single-atom catalyst of the present invention, the particle size is preferably 0.2 - 1 μm, more preferably 0.35 - 0.85 μm, and more preferably 0.5 - 0.7 μm.

[0065] The present invention provides a preparation method of a sulfur-doped nickel single-atom catalyst, comprising the following steps:

[0066] 1) Dissolve a nickel salt in an organic solvent to obtain solution A;

[0067] Dissolve thiourea in an organic solvent to obtain solution B, and then add phenanthroline to obtain solution C;

[0068] 2) Slowly add solution A obtained in the above step to solution C while mixing to obtain a mixed solution D;

[0069] 3) Mix the mixed solution D obtained in the above step with the molecular sieve again, and after calcination, the obtained powder is placed in a hydrofluoric acid solution for etching reaction to obtain a sulfur-doped nickel single-atom catalyst.

[0070] The present invention first dissolves a nickel salt in an organic solvent to obtain solution A;

[0071] After dissolving thiourea in an organic solvent, solution B is obtained. After adding o-phenanthroline, solution C is obtained.

[0072] In the present invention, the nickel salt preferably includes nickel nitrate hexahydrate.

[0073] In the present invention, the organic solvent preferably includes ethanol.

[0074] In the present invention, in solution A, the concentration of the nickel salt is preferably 1.2 - 2.1 g / L, more preferably 1.4 - 2.1 g / L, still more preferably 1.5 - 2.1 g / L, and even more preferably 1.6 - 2.0 g / L.

[0075] In the present invention, in solution B, the concentration of thiourea is preferably 10 - 40 g / L, more preferably 10 - 30 g / L, still more preferably 10 - 20 g / L, and even more preferably 10 - 15 g / L.

[0076] In the present invention, the mass ratio of o-phenanthroline to thiourea is preferably 4:(2 - 3), more preferably 4:(2.2 - 2.8), and still more preferably 4:(2.4 - 2.6).

[0077] In the present invention, the mass ratio of the nickel salt to thiourea is preferably (0.16 - 0.2):(0.2 - 0.3), more preferably (0.165 - 0.195):(0.22 - 0.28), and still more preferably (0.17 - 0.19):(0.24 - 0.26).

[0078] In the present invention, solution A obtained from the above steps is slowly added to solution C while mixing to obtain mixed solution D.

[0079] In the present invention, mixed solution A is transferred into a syringe, and mixed solution A is slowly injected into mixed solution C and stirred to obtain mixed solution D. Among them, nickel ions in mixed solution A react with o-phenanthroline in C to form a stable complex; thiourea molecules in mixed solution C play a promoting role in the coordination process.

[0080] In the present invention, the preferred manner of slow addition includes injection.

[0081] In the present invention, the rate of slow addition is preferably 5 - 10 mL / h, more preferably 6 - 9 mL / h, and still more preferably 7 - 8 mL / h.

[0082] In the present invention, the preferred manner of mixing includes stirring.

[0083] In the present invention, the mixing speed is preferably 500 - 1500 rpm, more preferably 700 - 1300 rpm, and still more preferably 900 - 1100 rpm.

[0084] Finally, in the present invention, the obtained mixed solution D is mixed with molecular sieve again, and after calcination, the obtained powder is placed in a hydrofluoric acid solution for etching reaction to obtain a sulfur-doped nickel single-atom catalyst.

[0085] In the present invention, the molecular sieve preferably includes mesoporous molecular sieve SBA-15.

[0086] In the present invention, the mass ratio of the molecular sieve to the nickel salt is preferably (0.2~0.5):(0.15~0.21), more preferably (0.25~0.45):(0.16~0.20), and even more preferably (0.3~0.4):(0.18~0.20).

[0087] In the present invention, the time for the re-mixing is preferably 10~30 min, more preferably 14~26 min, and even more preferably 18~22 min.

[0088] In the present invention, after the re-mixing, it preferably further includes a rotary evaporation and / or drying step, more preferably a rotary evaporation and drying step.

[0089] In the present invention, the temperature of the rotary evaporation is preferably 40~60 °C, more preferably 40~55 °C, and even more preferably 40~50 °C.

[0090] In the present invention, the rotation speed of the rotary evaporation is preferably 0.5~2 rpm, more preferably 0.8~1.7 rpm, and even more preferably 1.1~1.4 rpm.

[0091] In the present invention, the calcination is specifically preferably carried out under a protective atmosphere.

[0092] In the present invention, the heating rate of the calcination is preferably 5~10 °C / min, more preferably 5~8 °C / min, and even more preferably 5~6 °C / min.

[0093] In the present invention, the temperature of the calcination is preferably 600~1000 °C, more preferably 650~950 °C, even more preferably 700~900 °C, and even more preferably 750~850 °C.

[0094] In the present invention, the time of the calcination is preferably 1~4 h, more preferably 1.5~3.5 h, and even more preferably 2~3 h.

[0095] In the present invention, the mass concentration of the hydrofluoric acid solution is preferably 5%~15%, more preferably 7%~13%, even more preferably 9%~11%, and specifically may be 10%.

[0096] In the present invention, the time of the etching reaction is preferably 0.5 to 4 hours, more preferably 1 to 3.5 hours, still more preferably 1.5 to 3 hours, and even more preferably 2 to 2.5 hours.

[0097] The present invention provides an application of the sulfur-doped nickel single-atom catalyst described in any one of the above technical solutions or the sulfur-doped nickel single-atom catalyst prepared by the preparation method described in any one of the above technical solutions in electrocatalytic carbon dioxide reduction.

[0098] To complete and refine the overall technical solution of the present invention, better ensure the composition and structure of the sulfur-doped nickel single-atom catalyst, and further improve the catalytic performance of the sulfur-doped nickel single-atom catalyst in electrocatalytic carbon dioxide reduction, the above-mentioned sulfur-doped nickel single-atom catalyst, its preparation method, and application may specifically include the following contents:

[0099] The present invention provides a sulfur-doped nickel single-atom catalyst, which is a sulfur-doped mesoporous carbon material loaded with different concentrations of nickel atoms, and each nickel atom is isolated from each other.

[0100] Specifically, the mass ratio of the nickel atoms is 1.7% to 2.7%.

[0101] Preferably, when the mass atomic ratio of the nickel atoms is 2.7%, a carbon monoxide Faraday efficiency of more than 99% is maintained at a current density of 100 to 800 milliamperes per square centimeter.

[0102] The present invention also provides a preparation method of a sulfur-doped nickel single-atom catalyst, comprising the following steps:

[0103] Step 1: Dissolve nickel nitrate hexahydrate in absolute ethanol to obtain a mixed solution A;

[0104] Step 2: Dissolve thiourea in absolute ethanol and stir for 10 to 30 minutes to obtain a mixed solution B;

[0105] Step 3: Add o-phenanthroline to the mixed solution B and stir well for 10 to 30 minutes to obtain a mixed solution C;

[0106] Step 4: Transfer the mixed solution A into a syringe, slowly inject the mixed solution A into the mixed solution C, and stir to obtain a mixed solution D;

[0107] Step 5: Add 0.3 grams of mesoporous molecular sieve SBA-15 to the mixed solution D and stir for 10 to 30 minutes to obtain a mixed solution E; (filled skeleton)

[0108] Step 6: Transfer the mixed solution E into a single-neck flask, and perform rotary evaporation until the ethanol is completely evaporated, and then place it in an oven for further drying for 6 to 12 hours to obtain a solid powder F;

[0109] Step 7: Calcinate the solid powder F under an argon atmosphere to obtain a black powder G;

[0110] Step 8: Add the black powder G into a 10% hydrofluoric acid solution, let it stand for 0.5 to 4 hours, and then centrifuge, wash, and dry it to obtain the black powder, which is the sulfur-doped nickel single-atom catalyst.

[0111] Specifically, the amount of nickel nitrate hexahydrate used in Step 1 is 0.15 to 0.21 grams, and the volume of ethanol is 100 ml.

[0112] Furthermore, the amount of nickel nitrate hexahydrate used in Step 1 is 0.15 to 0.21 grams, and the volume of ethanol is 100 ml. A higher amount of nickel nitrate hexahydrate will not increase the loading amount of nickel single atoms, but will cause nickel to agglomerate into particles.

[0113] Specifically, the concentration of the mixed solution B in Step 2 is 10 to 40 grams per liter.

[0114] Specifically, the injection rate in Step 4 is 5 to 10 ml per hour, and the stirring speed is 500 to 1500 revolutions per minute.

[0115] Furthermore, during the implementation of the present invention, by using the above-mentioned injection flow rate, a uniformly dispersed nickel single-atom catalyst can be obtained. If the injection is too slow, a large amount of the solvent ethanol solution in the mixed solution C will volatilize; if the injection flow rate is too fast, it will cause difficulty for nickel atoms to fully react with the mixed solution C finally, resulting in the formation of nickel clusters finally.

[0116] Furthermore, the mass of the mesoporous molecular sieve in Step 5 is 0.2 to 0.5 grams.

[0117] Specifically, the rotary evaporation temperature in Step 6 is 40 to 60 °C, and the rotation speed is 0.5 to 2 revolutions per minute.

[0118] Furthermore, a milder rotary evaporation temperature is not conducive to solvent volatilization, and a higher rotary evaporation temperature will easily cause bumping and precipitation of solid components, resulting in a decrease in uniformity.

[0119] Specifically, the calcination temperature in Step 7 is 600 to 1000 °C, the heating rate is 5 to 10 °C per minute, and the calcination time is 1 to 4 hours.

[0120] The present invention also provides the application of the sulfur-doped nickel single-atom catalyst obtained by any of the above methods in the electrocatalytic reduction of carbon dioxide to prepare carbon monoxide.

[0121] Specifically, in the application, the sulfur-doped nickel single-atom catalyst is dispersed in isopropanol, and a Nafion solution is added as a binder, and ultrasonic dispersion is carried out to obtain a uniformly black mixed dispersion; the dispersion is sprayed onto carbon paper and dried on a heating table at 80 °C to obtain a working electrode.

[0122] Specifically, in the application, in the black dispersion, the concentration of the sulfur-doped nickel single-atom catalyst is 5-10 g / L, and the mass concentration of Nafion is 20-40 mg / L.

[0123] The present invention also provides an application of the sulfur-doped nickel single-atom catalyst according to any one of the above technical solutions or the sulfur-doped nickel single-atom catalyst obtained by the preparation method according to any one of the above technical solutions in the electrocatalytic reduction of carbon dioxide to prepare carbon monoxide.

[0124] The above content of the present invention provides a sulfur-doped nickel single-atom catalyst, its preparation method and application. The sulfur-doped nickel single-atom catalyst designed by the present invention has a specific structure and composition. By doping sulfur atoms on the nickel single-atom material, the adsorption of carbon dioxide reduction intermediates is adjusted, the performance of electrochemically reducing carbon dioxide to carbon monoxide is enhanced, and the nickel, nitrogen, and sulfur elements are evenly distributed on the carbon support with a large surface area, and a high catalytic efficiency and excellent stability are obtained at a large current density.

[0125] The present invention also provides a corresponding preparation method. The ethanol solution of nickel nitrate is injected into the ethanol solution of thiourea and o-phenanthroline at a certain flow rate and ratio and stirred. After stirring, it is rotary evaporated until most of the solvent volatilizes, and then placed in a vacuum oven for further drying. The dried solid is placed in a tubular furnace under an argon atmosphere for sufficient pyrolysis to obtain a sulfur-doped nickel single-atom catalyst. The catalyst prepared by the present invention has excellent performance in electrocatalytically reducing carbon dioxide to carbon monoxide, has an industrial-grade current density and extremely excellent carbon monoxide Faraday efficiency.

[0126] Experimental results show that the sulfur-doped nickel single-atom catalyst prepared by the present invention has excellent electrochemical carbon dioxide reduction performance. When applied to a flow cell, a carbon monoxide Faraday efficiency of more than 99% is achieved at a large current density of 100-800 mA / cm². Moreover, during the constant current electrolysis process of nearly 10 hours, the selectivity, activity and electrolysis potential of the electrocatalyst do not decrease significantly, and the stability is good.

[0127] To further illustrate the present invention, the following provides a detailed description of a sulfur-doped nickel single-atom catalyst provided by the present invention, its preparation method, and its application in combination with embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, giving detailed implementation manners and specific operation processes, only to further illustrate the features and advantages of the present invention, rather than limiting the claims of the present invention. The protection scope of the present invention is not limited to the following embodiments either.

[0128] Example 1

[0129] In this example, a sulfur-doped nickel single-atom catalyst was prepared, and the specific steps are as follows:

[0130] Dissolve 200 mg of nickel nitrate hexahydrate in 100 ml of absolute ethanol to obtain a mixed solution A; dissolve 0.2 g of thiourea in 20 ml of absolute ethanol and stir for 20 minutes to obtain a mixed solution B; add 0.4 g of o-phenanthroline to the mixed solution B and stir well for 20 minutes to obtain a mixed solution C; transfer 100 ml of the mixed solution A into a syringe and inject it into the mixed solution C at a rate of 10 ml per hour, and stir to obtain a mixed solution D; add 0.3 g of mesoporous molecular sieve SBA-15 to the mixed solution D and stir for 10 - 30 minutes to obtain a mixed solution E; transfer the mixed solution E into a single-necked flask and rotary evaporate at 40 °C until the ethanol is dried, and then place it in an oven at 60 °C for further drying for 12 hours to obtain a solid powder F; calcine the solid powder F in an argon atmosphere, the calcination temperature is 900 °C, the heating rate is 5 °C per minute, the calcination time is 3 h, and a black powder G is obtained after the calcination; add the black powder G to a 10% hydrofluoric acid solution and let it stand for 0.5 hours, and then centrifuge, wash, and dry. The obtained black powder is the sulfur-doped nickel single-atom catalyst.

[0131] It was determined by inductively coupled plasma atomic emission spectrometry that the proportion of nickel atoms in the sulfur-doped nickel single-atom catalyst obtained in this example was 2.7%.

[0132] See Figure 1 , Figure 1 are transmission electron microscope images of different scales of the sulfur-doped nickel single-atom catalyst prepared in Example 1 of the present invention. Among them, (a) is a transmission electron microscope image of 200 nm, and (b) is a transmission electron microscope image of 100 nm.

[0133] As Figure 1 shown in the transmission electron microscope image, the stripes are the pore channels of the mesoporous carbon after etching off the molecular sieve, and the particle size of the catalyst is about 0.2 - 1.0 microns.

[0134] See Figure 2 , Figure 2Element mapping of carbon, nitrogen, nickel, and sulfur of the sulfur-doped nickel single-atom catalyst prepared in Example 1 of the present invention by scanning electron microscopy. Among them, (a) is the carbon element mapping, (b) is the nitrogen element mapping, (c) is the nickel element mapping, and (d) is the sulfur element mapping.

[0135] As Figure 2 shown in the scanning electron microscopy (SEM) element mapping, nickel and sulfur elements are uniformly distributed on the carbon substrate.

[0136] See Figure 3 , Figure 3 Electron diffraction pattern and high-resolution transmission electron microscopy (HRTEM) image of the sulfur-doped nickel single-atom catalyst prepared in Example 1 of the present invention. Among them, (a) is the electron diffraction pattern, and (b) is the high-resolution transmission electron microscopy image.

[0137] As Figure 3 shown in the electron diffraction pattern and high-resolution transmission electron microscopy image, no crystalline nickel is present.

[0138] See Figure 4 , Figure 4 High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image of the sulfur-doped nickel single-atom catalyst prepared in Example 1 of the present invention.

[0139] As Figure 4 shown in the high-angle annular dark-field scanning transmission electron microscopy image, the circles are isolated nickel single atoms, demonstrating that nickel elements in the sulfur-doped nickel single-atom catalyst exist in the form of single atoms.

[0140] See Figure 5 , Figure 5 X-ray diffraction pattern of the sulfur-doped nickel single-atom catalyst prepared in Example 1 of the present invention.

[0141] As Figure 5 shown in the X-ray diffraction pattern, no diffraction peaks of metallic nickel and its oxides are observed.

[0142] See Figure 6 , Figure 6 Specific surface area test curve of the sulfur-doped nickel single-atom catalyst prepared in Example 1 of the present invention.

[0143] As Figure 6 shown in the specific surface area test curve, it has a large specific surface area of 751.986 square centimeters per gram, which can expose a larger active area.

[0144] The electrocatalytic performance of the sulfur-doped nickel single-atom catalyst obtained in this example was tested using a flow cell reactor. Specifically, 20 mg of the sulfur-doped nickel single-atom catalyst was weighed and dispersed in 2 mL of isopropanol, and 40 μL of Nafion solution was added as a binder. After ultrasonic dispersion, a homogeneous black mixed dispersion was obtained; the dispersion was sprayed onto a 3×3 cm² carbon paper and dried on an 80 °C heating table to obtain a working electrode; the loading of the sulfur-doped nickel single-atom catalyst was about 1 mg per square centimeter, serving as the cathode of the gas diffusion electrode; the working window area of the working electrode was 0.75 cm²; the flow rate of carbon dioxide gas was controlled at 30 mL per minute; the cathode electrolyte was 1 mol / L potassium hydroxide with a flow rate controlled at 1.3 mL per minute; the anode electrolyte was 3 mol / L potassium hydroxide, circulated by a pump; a nickel foam was used as the counter electrode; and a mercury / mercuric oxide electrode was used as the reference electrode.

[0145] In this example, a constant current method was used for testing. The resulting reaction gas-phase products (hydrogen, methane, carbon monoxide, ethylene) were detected by gas chromatography, and then data such as the selectivity and activity of the catalytic reaction were obtained based on the total Coulomb quantity recorded by the electrochemical workstation.

[0146] See Figure 7 , Figure 7 are the results of the Faraday efficiency of each product and the relative standard hydrogen electrode potential at different current densities in the electroreduction of carbon dioxide catalyzed by the sulfur-doped nickel single-atom catalyst prepared in Example 1 of the present invention.

[0147] As Figure 7 shown by the measured Faraday efficiency of each gas product at different current densities, it can be seen that at a current density of 800 mA per square centimeter, the carbon monoxide Faraday efficiency is 99%, and there are no other electroreduction products except for a small amount of hydrogen.

[0148] Example 2

[0149] In this example, a sulfur-doped nickel single-atom catalyst was prepared, and the specific steps are as follows:

[0150] Dissolve 160 mg of nickel nitrate hexahydrate in 100 mL of absolute ethanol to obtain a mixed solution A; dissolve 0.25 g of thiourea in 20 mL of absolute ethanol and stir for 20 minutes to obtain a mixed solution B; add 0.4 g of o-phenanthroline to the mixed solution B and stir well for 20 minutes to obtain a mixed solution C; transfer 100 mL of the mixed solution A into a syringe and inject it into the mixed solution C at a rate of 10 mL per hour, and stir to obtain a mixed solution D; add 0.3 g of mesoporous molecular sieve SBA-15 to the mixed solution D and stir for 10 - 30 minutes to obtain a mixed solution E; transfer the mixed solution E into a single-necked flask and rotary evaporate at 40 °C until the ethanol is dried, and then place it in an oven at 60 °C for further drying for 12 hours to obtain a solid powder F; calcine the solid powder F in an argon atmosphere, the calcination temperature is 900 °C, the heating rate is 10 °C per minute, and the calcination time is 3 h. After the calcination is completed, a black powder G is obtained; add the black powder G to a 10% hydrofluoric acid solution and let it stand for 0.5 hour, and then centrifuge, wash, and dry. The obtained black powder is the sulfur-doped nickel single-atom catalyst.

[0151] The proportion of nickel atoms in the sulfur-doped nickel single-atom catalyst obtained in this example was determined by inductively coupled plasma atomic emission spectrometry to be 1.7%.

[0152] Example 3

[0153] In this example, a sulfur-doped nickel single-atom catalyst was prepared, and the specific steps are as follows:

[0154] Dissolve 180 mg of nickel nitrate hexahydrate in 100 mL of absolute ethanol to obtain a mixed solution A; dissolve 0.3 g of thiourea in 20 mL of absolute ethanol and stir for 20 minutes to obtain a mixed solution B; add 0.4 g of o-phenanthroline to the mixed solution B and stir well for 20 minutes to obtain a mixed solution C; transfer 100 mL of the mixed solution A into a syringe and inject it into the mixed solution C at a rate of 10 mL per hour, and stir to obtain a mixed solution D; add 0.3 g of mesoporous molecular sieve SBA-15 to the mixed solution D and stir for 10 - 30 minutes to obtain a mixed solution E; transfer the mixed solution E into a single-necked flask and rotary evaporate at 40 °C until the ethanol is dried, and then place it in an oven at 60 °C for further drying for 12 hours to obtain a solid powder F; calcine the solid powder F in an argon atmosphere, the calcination temperature is 900 °C, the heating rate is 5 °C per minute, and the calcination time is 3 h. After the calcination is completed, a black powder G is obtained; add the black powder G to a 10% hydrofluoric acid solution and let it stand for 0.5 hour, and then centrifuge, wash, and dry. The obtained black powder is the sulfur-doped nickel single-atom catalyst.

[0155] The nickel atom proportion in the sulfur-doped nickel single-atom catalyst obtained in this example was determined to be 2.0% by inductively coupled plasma atomic emission spectrometry.

[0156] The above provides a detailed introduction to a sulfur-doped nickel single-atom catalyst and its preparation method and application. Specific examples are used herein to elaborate on the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in the technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A sulfur-doped nickel single-atom catalyst, characterized in that: The sulfur-doped nickel single-atom catalyst is obtained by etching away the molecular sieve from a molecular sieve precursor loaded with sulfur, nickel and carbon.

2. The sulfur-doped nickel single-atom catalyst according to claim 1, characterized in that The molecular sieve precursor loaded with sulfur, nickel and carbon is obtained by calcining the molecular sieve precursor loaded with thiourea, nickel source and o-phenanthroline; In the molecular sieve precursor loaded with thiourea, nickel source and o-phenanthroline, nickel ions and o-phenanthroline form a complex; The molecular sieve comprises a mesoporous molecular sieve; The mesoporous molecular sieve includes one or more of SBA-15 molecular sieve, SBA-16 molecular sieve, KIT-6 molecular sieve, MCM-41 molecular sieve and MCM-41 molecular sieve.

3. The sulfur-doped nickel single atom catalyst according to claim 1, characterized in that: The sulfur-doped nickel single-atom catalyst has a hexagonal columnar structure in its microstructure; The mass content of nickel in the sulfur-doped nickel single-atom catalyst is 1.7% to 2.7%; The sulfur-doped nickel single-atom catalyst has a sulfur content of 3.0% to 4.7% by mass; The particle size of the sulfur-doped nickel single-atom catalyst is 0.2-1 μm.

4. A method for preparing a sulfur-doped nickel single-atom catalyst, characterized in that: The following steps are involved: 1) Dissolving nickel salt in an organic solvent to obtain solution A; After dissolving thiourea in an organic solvent, solution B is obtained, and after adding o-phenanthroline, solution C is obtained; 2) slowly adding the solution A obtained in the above step into the solution C while mixing, to obtain a mixed solution D; 3) The mixed solution D obtained in the above step is mixed with the molecular sieve again, and then calcined to obtain a powder, which is placed in a hydrofluoric acid solution for etching reaction to obtain a sulfur-doped nickel single atom catalyst.

5. The preparation method according to claim 4, characterized in that: The nickel salt includes nickel nitrate hexahydrate; The organic solvent includes ethanol; In the solution A, the concentration of nickel salt is 1.2-2.1 g / L; In the solution B, the concentration of thiourea is 10-40 g / L.

6. The preparation method according to claim 4, characterized in that: The mass ratio of o-phenanthroline to thiourea is 4:(2-3); The mass ratio of the nickel salt to thiourea is (0.16-0.2): (0.2-0.3); The slow adding method includes injection; The speed of the slow addition is 5-10 mL / h.

7. The preparation method according to claim 4, characterized in that: The mixing method includes stirring; The mixing speed is 500-1500 rpm; The molecular sieve includes mesoporous molecular sieve SBA-15; The mass ratio of the molecular sieve to the nickel salt is (0.2-0.5): (0.15-0.21).

8. The preparation method according to claim 4, characterized in that: The time of remixing is 10 to 30 minutes; After the remixing, the step of rotary evaporation and / or drying is also included; The temperature of the rotary evaporation is 40-60°C; The rotation speed of the rotary evaporation is 0.5-2 rpm; The calcination is specifically carried out under a protective atmosphere.

9. The preparation method according to claim 4, characterized in that: The heating rate of the calcination is 5-10°C / min; The calcination temperature is 600-1000°C; The calcination time is 1 to 4 hours; The mass concentration of the hydrofluoric acid solution is 5% to 15%; The etching reaction time is 0.5 to 4 hours.

10. Use of the sulfur-doped nickel single-atom catalyst according to any one of claims 1 to 3 or the sulfur-doped nickel single-atom catalyst prepared by the preparation method according to any one of claims 4 to 9 in electrocatalytic carbon dioxide reduction.

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