CN114808018A - Monoatomic iron-doped nitrogen-carbon material and preparation method and application thereof - Google Patents
Monoatomic iron-doped nitrogen-carbon material and preparation method and application thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
- C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
- C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
- C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/23—Carbon monoxide or syngas
Abstract
The invention discloses a nitrogen-carbon material doped with monoatomic iron and a preparation method and application thereof, wherein the preparation method comprises the following steps: mixing iron salt, biochar and water, drying until solid is formed, heating the solid to 300-650 ℃ in an inert gas or nitrogen environment, keeping the temperature for 1-3 hours, heating to 900-1100 ℃ again, keeping the temperature for 1-2 hours, and cooling to room temperature to obtain the nitrogen-carbon material. The nitrogen-carbon material is used as a catalyst and is in the range of 0.1M KHCO 3 Electrocatalytic reduction of CO in electrolytes 2 Shows higher catalytic activity, and the Tafel slope is 70mv dec ‑1 The composition of the active center Fe-Nx and the porous structure of the material ensure that the FECO of the catalyst reaches 93 percent under the lower over potential of-0.6V; has good material stability.
Description
Technical Field
The invention belongs to the technical field of environment functional materials, and particularly relates to a monoatomic iron-doped nitrogen-carbon material, and a preparation method and application thereof.
Background
With a greenhouseThe environmental problems caused by gases are becoming more severe, and the reserves of non-renewable energy sources such as fossil energy and the like are reduced, so that the capture and utilization of carbon dioxide are extremely important, and the development of efficient technology for converting carbon dioxide into valuable chemical energy sources for utilization is urgently needed. The electrocatalytic reduction method is to add electric energy to CO 2 The method is reduced into a value-added product, has the advantages of simple operation, controllable reaction conditions and the like, and the electric energy required by the electrocatalysis process can be provided by renewable energy sources such as solar energy, wind energy and the like, thereby realizing green sustainable development. However, high bond energy of C ═ O (750kJ mol) -1 ) This means that the CO is activated 2 The molecules require a high overpotential. Thus, an effective electrocatalyst is enhanced electrocatalytic CO 2 RR performance requirements.
In past research, researchers have developed a series of catalysts for the electrocatalytic reduction of CO 2 Such as simple metal, metal oxide, metal alloy, carbon-based material, N-doped carbon-based material, etc., but the catalytic effect of the catalyst is not ideal, and the proposed monatomic catalyst has attracted much research interest. The monatomic metal has higher surface energy, and the monatomic catalyst has the characteristics of high selectivity, high stability, repeated recycling and the like. Sui et al studied the preparation of monoatomic Ag-N by loading noble metal silver (Ag) onto the surface of nitrogen-doped carbon materials 3 the/PCNC can convert CO at a lower overpotential 2 The carbon dioxide is converted into CO, has higher CO Faraday Efficiency (FECO), but has the problems of high price, limited resources, poor stability and the like, and greatly restricts large-scale commercial application.
At present, research has been made to propose a catalyst of an M-N-C structure, which enhances the activity of the monatomic transition metal (M) by doping N and supporting a carbon material (C). Fe-N-C catalyst has excellent performance in a variety of transition metal catalysts, and Zouiao et al disclose a method for preparing Fe-N-C nanowire catalyst (Zouiao, Van dab, Huanggui Mei, Ponga lyre, Bin Mytilus, Wen Lijia et al. A method for preparing Fe-N-C nanowire catalyst, 202111262456.1), however, the raw material for preparing Fe-N-C includes Zn (NO) 3 ) 2 ·nH 2 O、FeCl 2 ·mH 2 O, 2-methylimidazole, potassium iodide and methanol, wherein the slow dripping, stirring, separation and the like in the preparation step are used for obtaining a precursor of the ZIF-8 doped with Fe, and then the precursor is calcined to obtain the Fe-N-C structural material. Similarly, Wangjide et al disclose an iron-nitrogen co-doped carbon nanocatalysis material for improving the electro-catalytic oxygen reduction performance (Wangjide, Von super, Guo, Xiyuehong, Zuli, Chenting Xiang, etc. (2020). an iron-nitrogen co-doped carbon nanocatalysis material for improving the electro-catalytic oxygen reduction performance CN111082084A), wherein the related Fe @ N-C structure needs to utilize lone pair electron competition coordination action on nitrogen atom in 2-methylimidazole or benzimidazole to successfully obtain the nitrogen-enriched Fe @ N-C material. Therefore, the preparation of the Fe-N-C structure at present usually needs a mode of firstly coordinating the Fe-N precursor and then carbonizing the Fe-N-C at high temperature, and the preparation process is complex. And the same kind of materials are mostly used for anode materials, and the oxygen reduction capability (ORR) of the anode materials is tested.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a preparation method of a monatomic iron-doped nitrogen-carbon material.
The invention also aims to provide the monatomic iron-doped nitrogen-carbon material obtained by the preparation method.
Another object of the present invention is to provide the above nitrogen-carbon material as a catalyst for improving the electrocatalytic reduction of CO 2 In the faraday efficiency of CO.
The purpose of the invention is realized by the following technical scheme.
A preparation method of a monatomic iron-doped nitrogen-carbon material comprises the following steps: mixing ferric salt, biochar and water, drying at 10-105 ℃ to form a solid, heating the solid to 300-650 ℃ in an inert gas or nitrogen environment, keeping the temperature for 1-3 hours, heating to 900-1100 ℃ again, keeping the temperature for 1-2 hours, and cooling to room temperature to obtain a nitrogen-carbon material, wherein the ratio of iron to biochar to water in the ferric salt is (0.001-0.01): 1: 15.
in the technical scheme, the solid is heated to 300-650 ℃ at a heating rate of 2-10 ℃/min.
In the technical scheme, the heating rate of heating to 900-1100 ℃ is 2-15 ℃/min.
In the technical scheme, the ratio of iron, biochar and water in the ferric salt is (0.002-0.009): 1:15, preferably (0.003-0.008): 1:15, more preferably (0.004 to 0.006): 1: 15.
the nitrogen-carbon material obtained by the preparation method.
The nitrogen-carbon material is used as a catalyst for improving the electrocatalytic reduction of CO 2 In the faraday efficiency of CO.
In the technical scheme, the highest faradaic efficiency of CO is 93%.
In the technical scheme, the nitrogen-carbon material is used as a catalyst for electrocatalytic reduction of CO 2 The method comprises the following steps: uniformly mixing 5-7 parts by mass of a catalyst, 190-210 parts by volume of deionized water, 360-380 parts by volume of anhydrous ethanol and 20-40 parts by volume of a 5% Nafion solution to obtain a solution, dropwise adding the solution on the surface of carbon cloth, drying the solution to serve as a working electrode, putting the working electrode, a reference electrode and a counter electrode into an electrolyte for electrolysis, wherein the overpotential is-0.3V-1.1V, and the electrolyte is water and KHCO 3 Mixture of (1), KHCO in electrolyte 3 The concentration of (A) is 0.1-0.3M, the unit of volume fraction is mu L, and the unit of mass fraction is mg.
In the technical scheme, the overpotential is-0.4V to-0.8V, and is preferably-0.5V to-0.7V.
In the technical scheme, KHCO is contained in the electrolyte 3 The concentration of (A) is 0.1-0.15M.
The invention constructs the Fe-Nx active center directly by forming a coordination bond between the biochar rich in N and the transition metal, and prepares the active center for effectively improving CO 2 The reduction efficiency of (1).
The invention successfully prepares the nitrogen-carbon material doped with the monatomic iron by the dipping and calcining method, and has simple preparation method and low raw material cost. The nitrogen-carbon material is used as a catalyst and is in the range of 0.1M KHCO 3 Electrocatalytic reduction of CO in electrolytes 2 Shows higher catalytic activityGood, Tafel slope is 70mv dec -1 The composition of the active center Fe-Nx and the porous structure of the material ensure that the FECO of the catalyst reaches 93 percent under the lower over potential of-0.6V (RHE); has good material stability.
Drawings
FIG. 1 is an XRD of the nitrogen-carbon materials obtained in example 1 and comparative example 1;
FIG. 2 is SEM, EDS, TEM and HAADF-STEM of a nitrocarbon material, wherein a is SEM of a nitrocarbon material obtained in comparative example 1, b is SEM of a nitrocarbon material obtained in example 1, c is EDS of a nitrocarbon material obtained in example 1, d is TEM of a nitrocarbon material obtained in example 1, and e is HAADF-STEM of a nitrocarbon material obtained in example 1;
FIG. 3a shows the electrocatalytic reduction of CO in examples 6 to 8 and comparative example 2 2 The FECO of (1);
FIG. 3b shows the electrocatalytic reduction of CO in examples 6 to 8 and comparative example 2 2 FEH of 2 ；
FIG. 4a shows the electrocatalytic reduction of CO in examples 6, 9 and 10 and comparative example 2 2 The FECO of (1);
FIG. 4b shows the electrocatalytic reduction of CO in examples 6, 9 and 10 and comparative example 2 2 FEH of 2 ；
FIG. 5a shows the electrocatalytic reduction of CO for examples 6, 11 and 12 2 The FECO of (1);
FIG. 5b shows the electrocatalytic reduction of CO for examples 6, 11 and 12 2 FEH of 2 ；
FIG. 6a is a diagram illustrating the electrocatalytic reduction of CO by the monatomic iron-doped nitrogen-carbon material obtained in examples 1 to 3 2 Linear current-voltage characteristic of (d);
FIG. 6b shows the electrocatalytic reduction of CO by the monoatomic iron-doped N-carbon material obtained in examples 1, 4 and 5 2 Linear current-voltage characteristic of (d);
fig. 6c is the Tafel slope for the monatomic iron-doped nitrocarbon material obtained in example 1 and the nitrocarbon material obtained in comparative example 1.
Detailed Description
The technical scheme of the invention is further explained by combining specific examples.
The raw material of the biochar can be straw, wood chips, animal wastes, sludge and the like. In the following examples, the raw material of the biochar is wheat straw. The method for preparing the biochar comprises the following steps: the method comprises the steps of airing and crushing the wheat straws until the particle size is less than 5mm, weighing 20g of the crushed wheat straws in a ceramic crucible, and putting the crushed wheat straws into an oven (DGG-9023A, Shanghai Sensin laboratory instruments Co., Ltd., China) to be dried for 24 hours at 80 ℃. The dried wheat straw is put into a ceramic crucible, covered and then placed into an atmosphere box (SQFL-1200, Shanghai Bijing, China) to be subjected to lower limit oxygen cracking for 2 hours at the temperature of 500 ℃. And after the cracking is finished, obtaining the biochar, and sealing for later use.
Example 1
A method of making a monatomic iron-doped nitrogen-carbon material (Fe-N-C), comprising: mixing ferric nitrate nonahydrate (ferric salt), biochar and deionized water, drying at 80 ℃ for 24 hours to form a solid, heating the solid to 550 ℃ at the speed of 6 ℃/min in a vacuum atmosphere furnace in a nitrogen environment, keeping the temperature for 2 hours, heating to 900 ℃ at the speed of 2 ℃/min, keeping the temperature for 1 hour, cooling to room temperature of 20-25 ℃, and obtaining the nitrogen-carbon material, wherein the ratio of iron, biochar and water in the ferric nitrate nonahydrate is 0.005:1:15 in parts by mass.
Example 2
A method of making a monatomic iron-doped nitrogen-carbon material (Fe-N-C), comprising: mixing ferric nitrate nonahydrate, biochar and deionized water, drying at 80 ℃ for 24 hours to form a solid, heating the solid to 550 ℃ at the speed of 6 ℃/min in a vacuum atmosphere furnace in a nitrogen environment, keeping the temperature for 2 hours, heating to 1000 ℃ at the speed of 2 ℃/min, keeping the temperature for 1 hour, cooling to room temperature of 20-25 ℃, and obtaining the nitrogen-carbon material, wherein the ratio of iron, biochar and water in the ferric nitrate nonahydrate is 0.005:1:15 in parts by mass.
Example 3
A method of making a monatomic iron-doped nitrogen-carbon material (Fe-N-C), comprising: mixing ferric nitrate nonahydrate, biochar and deionized water, drying at 80 ℃ for 24 hours to form a solid, heating the solid to 550 ℃ at the speed of 6 ℃/min in a vacuum atmosphere furnace in a nitrogen environment, keeping the temperature for 2 hours, heating to 1100 ℃ at the speed of 2 ℃/min, keeping the temperature for 1 hour, and cooling to room temperature of 20-25 ℃ to obtain a nitrogen-carbon material, wherein the ratio of iron, biochar and water in the ferric nitrate nonahydrate is 0.005:1:15 in parts by mass.
Example 4
A method of making a monatomic iron-doped nitrogen-carbon material (Fe-N-C), comprising: mixing ferric nitrate nonahydrate, biochar and deionized water, drying at 80 ℃ for 24 hours to form a solid, heating the solid to 550 ℃ at the speed of 6 ℃/min in a vacuum atmosphere furnace in a nitrogen environment, keeping the temperature for 2 hours, heating to 900 ℃ at the speed of 2 ℃/min, keeping the temperature for 1 hour, cooling to room temperature of 20-25 ℃, and obtaining the nitrogen-carbon material, wherein the ratio of iron, biochar and water in the ferric nitrate nonahydrate is 0.001:1:15 in parts by mass.
Example 5
A method of making a monatomic iron-doped nitrogen-carbon material (Fe-N-C), comprising: mixing ferric nitrate nonahydrate, biochar and deionized water, drying at 80 ℃ for 24 hours to form a solid, heating the solid to 550 ℃ at the speed of 6 ℃/min in a vacuum atmosphere furnace in a nitrogen environment, keeping the temperature for 2 hours, heating to 900 ℃ at the speed of 2 ℃/min, keeping the temperature for 1 hour, cooling to room temperature of 20-25 ℃, and obtaining the nitrogen-carbon material, wherein the ratio of iron, biochar and water in the ferric nitrate nonahydrate is 0.01:1:15 in parts by mass.
Comparative example 1
A method of making a nitrocarbon material, comprising: mixing biochar and deionized water, drying at 80 ℃ for 24 hours to form a solid, heating the solid to 550 ℃ at the speed of 6 ℃/min in a vacuum atmosphere furnace in a nitrogen environment, keeping the temperature for 2 hours, heating to 900 ℃ at the speed of 2 ℃/min, keeping the temperature for 1 hour, and cooling to room temperature of 20-25 ℃ to obtain the nitrogen-carbon material, wherein the ratio of the biochar to the water is 1:15 in parts by mass.
As shown in fig. 1, the XRD pattern of the nitrogen-carbon material obtained in example 1 has two distinct peaks at 25.9 ° and 42.9 °, corresponding to (002) and (100) planes of graphitic carbon, respectively. In addition, no other significant peak was detected in the XRD pattern, which means that Fe atoms may appear in an amorphous phase, in an atomic form, or embedded in an N — C skeleton. The carbon-based material after calcination has a certain degree of graphitization, and it is noted that the nitrogen-carbon material obtained in example 1 has one more graphite carbon peak (100) at 42.9 ° than the nitrogen-carbon material obtained in comparative example 1, which is probably due to the influence of iron doping on the natural periodic arrangement of the carbon matrix. The degree of graphitization also affects the conductivity of the material.
As shown in fig. 2, it can be observed from fig. 2 that the surface of the nitrogen-carbon material obtained in comparative example 1 has a similar spherical structure (a of fig. 2), which is probably because the pores of the surface of the material are closed by sintering at the end of calcination, and thus the surface of the material assumes an approximately spherical structure. The nitrocarbon material obtained in example 1 (b of fig. 2) had a rich porous structure compared to the nitrocarbon material obtained in comparative example 1. This is probably due to the fact that the addition of metallic iron during calcination changes the original morphology of the material, reducing the grain size and the degree of order of the carbon material. The corresponding EDS (C of fig. 2) results show that Fe, C and N are uniformly dispersed throughout the material surface, no bright aggregation sites are observed, demonstrating that no metal clusters are formed during Fe doping. The TEM image shows the amorphous carbon appearance of the nitrogen-carbon material obtained in example 1, and as shown in d of fig. 2, no significant black shadow aggregation was observed, which demonstrates that the Fe-doped material can be uniformly dispersed on the surface of the carbon-based material or doped into the carbon nitrogen skeleton, and that the clusters are not formed on the carbon-based material. In addition, bright spots of high density were observed in the HAADF-STEM image (e of fig. 2), which indicate the presence of monoatomic Fe.
Electrocatalytic reduction of CO was performed using one of the nitrogen-carbon materials obtained in examples 1 to 5 and comparative document 1 as a catalyst 2 Electrocatalytic reduction of CO 2 The method comprises the following steps: weighing 6mg of catalyst, 200 mu L of deionized water, 370 mu L of absolute ethyl alcohol and 30 mu L of 5% Nafion solution (Tianjin Jiangtian chemical technology Co., Ltd.), mixing, carrying out ultrasonic treatment for 4h to obtain a solution, dropwise adding 600 mu L of the solution on the surface of 1 cm-1 cm carbon cloth, naturally air-drying, thereby loading the catalyst on the surface of the carbon cloth to be used as a working electrode, and respectively using a Saturated Calomel Electrode (SCE) and a graphite electrode (purchased from Kamad Tianjin chemical technology Co., Ltd.) as a working electrodeA reference electrode and a counter electrode. The electrolysis process is carried out in an electrolyte from-0.3V (RHE) to-1.1V (RHE), wherein the electrolyte is water and KHCO 3 Mixture of (1), KHCO in the electrolyte 3 The concentration of (2) is C M, and the catalyst used and the value of C are shown in the following table.
| Examples | Catalyst and process for preparing same | C |
| Example 6 | Example 1 | 0.1 |
| Example 7 | Example 2 | 0.1 |
| Example 8 | Example 3 | 0.1 |
| Example 9 | Example 4 | 0.1 |
| Example 10 | Example 5 | 0.1 |
| Comparative example 2 | Comparative example 1 | 0.1 |
| Example 11 | Example 1 | 0.2 |
| Example 12 | Example 1 | 0.3 |
Electrocatalytic reduction of CO by comparative examples 6-8 and comparative example 2 2 As a result, it was found that the optimum overpotential of CO at-0.6V (RHE) increases as the carbonization temperature increases from 900 ℃ to 1100 ℃ 2 The reduction product of (2) (i.e., CO Faraday efficiency, FE) CO ) From 93% down to 54% (FIG. 3a), and examples 6-8 and comparative example 2 electrolyze H 2 O by-product H 2 Is (i.e. H) 2 Faraday efficiency, FE H2 ) The increase from 7% to 62% (FIG. 3b) illustrates that the use of the 900 ℃ nitrocarbon material in example 6 is more beneficial for CO conversion 2 Reducing the CO into CO and reducing the side reaction of the CO and water. The reason is that the carbonization temperature is increased, the coking degree of the material surface is serious, the abundant pore diameter structure is damaged, and metal atoms are gathered on the material surface, so that the catalytic efficiency of the catalyst is reduced. This result also confirms that 900 ℃ in example 1 is the optimum carbonization temperature.
Electrocatalytic reduction of CO by means of comparative examples 6, 9, 10 and comparative example 2 2 As a result, the maximum FECO concentration was-0.6V (RHE) for all three metal additions, but the FE concentration in example 6 was found to be within the entire overpotential range CO Highest (FIG. 4a), corresponding FE H2 Lowest (fig. 4 b). This is because when the loading ratio of Fe is low, the composition of the active center Fe — Nx decreases, and the intended catalytic effect cannot be achieved; when the load content of Fe is higher, because Fe single atom has higher specific surface energy, metal atoms are gathered on the surface of the material, and the two conditions can catalyzeThe catalytic efficiency of the agent decreases. This also confirmed that "the mass ratio of iron, biochar, and water was 0.005:1: 15", CO 2 The electrocatalytic activity of the electrocatalytic reduction is the best Fe adding amount for preparing the catalyst.
Electrocatalytic reduction of CO by means of comparative examples 6, 11, 12 2 As a result, it was found that FE was generated in a high potential region with an increase in the concentration of the electrolyte CO Significantly reduced (FIG. 5a) with corresponding FE' s H2 Increased (fig. 5b), probably because of the KHCO associated therewith 3 The concentration increases and other ions adsorb to the surface of the working electrode, and with the increase of the potential, CO is blocked 2 Binding with protons such that FE CO And decreases. Through research, 0.1M KHCO is found to be compared with electrolytes with other concentrations 3 The aqueous solution shows less hydrogen evolution reaction. Thus 0.1M KHCO 3 The aqueous solution is most preferred as the electrolyte.
In order to examine the conductivity of the catalyst, the nitrogen-carbon materials obtained in examples 1 to 3 and 4 to 5 were subjected to linear voltammetry measurements. The Linear Sweep Voltammetry (LSV) results are shown in fig. 6a and 6 b). As shown in FIG. 6a, as the carbonization temperature increases, from example 1 to example 3, the electrical conductivity of the monatomic iron-doped nitrogen-carbon material gradually decreased as the maximum current density decreased from 11 to 8.3mA cm -2 This may be due to the fact that the degree of densification of the monatomic iron-doped nitrogen-carbon material sintering decreases with increasing temperature. The conductivity for different iron mass percentages in the reaction is shown in figure 6 b. With the "mass ratio of iron, biochar and water" from 0.001:1:15 (example 4) is increased to 0.005:1:15 (example 1) the conductivity of the monatomic iron-doped nitrocarbon material gradually increased as indicated by an increase in the maximum current density from 8.1 to 11mA cm -2 ,. And when the mass ratio of the iron to the biochar to the water is increased to 0.01:1: conductivity of the nitrocarbon material did not increase significantly at 15 (example 5) (maximum current density increased from 11 to 11.7mA cm) -2 )。
The Tafel slope can describe the transfer rate of the first electron, the smaller the slope, the CO 2 The faster the initial electron transfer rate. As shown in FIG. 6c, it was found that example 1 was 0.56V to 0.6VA linear interval exists between the two, the Tafel slope is 68mV dec -1 Lower than 13368mV dec of comparative example 1 -1 It is demonstrated that the formation of relevant intermediates such as COOH has a higher kinetic rate when the overpotential is moderately increased.
The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.
Claims (10)
1. A preparation method of a monatomic iron-doped nitrogen-carbon material is characterized by comprising the following steps: mixing ferric salt, biochar and water, drying at 10-105 ℃ to form a solid, heating the solid to 300-650 ℃ in an inert gas or nitrogen environment, keeping the temperature for 1-3 hours, heating to 900-1100 ℃ again, keeping the temperature for 1-2 hours, and cooling to room temperature to obtain a nitrogen-carbon material, wherein the ratio of iron to biochar to water in the ferric salt is (0.001-0.01): 1: 15.
2. the method according to claim 1, wherein the solid is heated to 300 to 650 ℃ at a heating rate of 2 to 10 ℃/min.
3. The method according to claim 2, wherein the temperature rise rate of the temperature rise to 900 to 1100 ℃ is 2 to 15 ℃/min.
4. The preparation method according to claim 3, wherein the ratio of the iron in the iron salt to the biochar to the water is (0.002-0.009): 1:15, preferably (0.003-0.008): 1:15, more preferably (0.004 to 0.006): 1: 15.
5. a nitrocarbon material obtained by the production method according to any one of claims 1 to 4.
6. Such as rightUse of the nitrogen-carbon material of claim 5 as a catalyst in the enhanced electrocatalytic reduction of CO 2 In the faraday efficiency of CO.
7. Use according to claim 6, wherein the CO Faraday efficiency is at most 93%.
8. Use according to claim 6, characterised in that the nitrogen-carbon material acts as a catalyst for the electrocatalytic reduction of CO 2 The method comprises the following steps: uniformly mixing 5-7 parts by mass of a catalyst, 190-210 parts by volume of deionized water, 360-380 parts by volume of anhydrous ethanol and 20-40 parts by volume of a 5% Nafion solution to obtain a solution, dropwise adding the solution on the surface of carbon cloth, drying the solution to serve as a working electrode, putting the working electrode, a reference electrode and a counter electrode into an electrolyte for electrolysis, wherein the overpotential is-0.3V-1.1V, and the electrolyte is water and KHCO 3 Mixture of (1), KHCO in electrolyte 3 The concentration of (A) is 0.1-0.3M, the unit of volume fraction is mu L, and the unit of mass fraction is mg.
9. Use according to claim 8, characterized in that the overpotential is-0.4V to-0.8V, preferably-0.5V to-0.7V.
10. Use according to claim 8 or 9, wherein the electrolyte is KHCO 3 The concentration of (A) is 0.1-0.15M.
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