CN115064706B - Metal-free porous nitrogen-oxygen doped carbon-based catalyst and preparation method and application thereof - Google Patents
Metal-free porous nitrogen-oxygen doped carbon-based catalyst and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a metal-free porous nitrogen-oxygen doped carbon-based catalyst, and a preparation method and application thereof. The preparation method comprises the following steps: firstly, dissolving a carbon source, a nitrogen source, a complexing agent and sodium chloride in a tris buffer solution, and obtaining first powder by a spray drying method; pre-crosslinking and activating the first powder by low-temperature idle firing to obtain second powder; and calcining the second powder at high temperature in an inert atmosphere to realize pyrolysis carbonization of the powder, and pickling and washing the obtained product to obtain the porous nitrogen-oxygen doped carbon-based catalyst. The preparation method is simple, has rich raw material resources and is suitable for large-scale production. The prepared catalyst has a hierarchical porous morphology, is rich in surface defects, and shows excellent electrocatalytic oxygen reduction performance; the catalyst does not contain metal, so that the problem of metal dissolution in the catalytic reaction can be effectively avoided, and the catalyst has excellent stability; meanwhile, compared with the catalyst participated by transition metal and noble metal, the catalyst has obvious cost advantage.
Description
Technical Field
The invention relates to the field of electrochemistry, in particular to a metal-free porous nitrogen-oxygen doped carbon-based catalyst, and a preparation method and application thereof.
Background
The development of low-carbon, green energy technology and industrial structures is currently a major trend, and green energy conversion and storage technology based on electrochemistry is receiving a great deal of attention from many students. Among them, metal-air batteries and fuel cells in which air participates, because of their extremely high energy density, stable output voltage, and pollution-free byproducts, show great potential in the energy storage field, and fuel cells are also considered as a solution for the ultimate energy source. However, the slow reaction kinetics resulting from the electron transfer in the air positive oxygen reduction (ORR) process 4 becomes a key factor limiting the overall energy conversion efficiency of the fuel cell device, and greatly delays the commercialization process of the device.
At present, platinum carbon catalysts have been successfully applied to the field of commercial hydrogen fuel cells due to their good oxygen reduction activity and excellent stability; however, because of the noble metal characteristics of platinum metal, the catalyst cost is directly increased by times, and the civil promotion of the fuel cell is hindered; and platinum is easy to combine with carbon monoxide, the catalyst performance is gradually deteriorated, and finally the catalyst is deactivated, which is a challenge for commercialization of the platinum carbon catalyst.
In order to reduce the cost of oxygen reduction catalysts, more and more work is being focused on how to reduce the platinum loading, and to use transition metals in place of platinum to achieve improved catalyst performance and reduced cost. For example, transition metal-supported carbon materials (iron, cobalt-supported carbon materials), metal nitrides, sulfides, and transition metal monoatomic materials, noble metal monoatomic catalytic materials, etc. which have recently emerged, are generally used for improving the catalyst activity by controlling the structure-activity relationship between the metal atoms and the carbon support. However, because of the weak tolerance of transition metals in strong alkaline (acid) electrolytes, dissolution of metals occurs over time, which in turn leads to a decrease in catalyst stability and gradual deactivation. Meanwhile, for a single-atom catalyst, the material is easy to deactivate in the storage process due to the higher activity and weaker bonding bond energy with a carbon-based carrier.
To solve the above problems, metal-free supported carbon-based catalysts are gradually coming into the field of view of researchers. Atoms such as nitrogen, oxygen, fluorine, phosphorus and the like are introduced through non-metal heteroatom doping, and the local electronic structure and geometric configuration of the carbon material are changed through manufacturing vacancy defects, so that the regulation and control of catalytic activity are realized. And because no metal participates, the problems of metal dissolution, catalytic activity inactivation and the like can be effectively solved, and the catalyst has extremely high stability. However, the existing preparation method of the material is complex, the raw materials are expensive, the yield is low, the large-scale production cannot be met, and the practical application is severely limited. Thus, there is a need to develop a metal-free carbon-based catalyst process for synthesizing high activity, high durability, high yield ORR catalysts.
Disclosure of Invention
In view of the shortcomings of the prior art, the invention aims to provide a metal-free porous nitrogen-oxygen doped carbon-based catalyst, and a preparation method and application thereof, and aims to solve the problems that the existing metal-free carbon-based catalyst preparation method is complex, raw materials are expensive, and the yield is low and large-scale production cannot be met by developing a metal-free carbon-based catalyst method for synthesizing an ORR catalyst with high activity, high durability and high yield.
The technical scheme of the invention is as follows:
the preparation method of the metal-free porous nitrogen-oxygen doped carbon-based catalyst comprises the following steps:
1.1, respectively dissolving a carbon source, a nitrogen source, a complexing agent and sodium chloride in a tris buffer solution, and then obtaining uniformly mixed first powder through a spray drying process;
1.2, carrying out blank burning treatment on the first powder to obtain second powder;
and 1.3, carrying out high-temperature calcination treatment on the second powder under the condition of inert atmosphere, and carrying out acid washing and water washing treatment on the obtained product to obtain the metal-free porous nitrogen-oxygen doped carbon-based catalyst.
The preparation method of the metal-free porous nitrogen-oxygen doped carbon-based catalyst comprises the steps that a carbon source is tannic acid, a nitrogen source is urea, tris (hydroxymethyl) aminomethane, and a complexing agent is zinc salt.
The preparation method of the metal-free porous nitrogen-oxygen doped carbon-based catalyst comprises the step of preparing the metal-free porous nitrogen-oxygen doped carbon-based catalyst, wherein the mass ratio of tannic acid to urea is (0.5-1.5): 1.
In the preparation method of the metal-free porous nitrogen-oxygen doped carbon-based catalyst, in the spray drying process in the step 1.1, the flow rate of spray gas is 5-15L/min, the temperature of an air inlet is 110-160 ℃, and the temperature of an air outlet is 90-100 ℃.
In the preparation method of the metal-free porous nitrogen-oxygen doped carbon-based catalyst, in the idle firing treatment in the step 1.2, the idle firing temperature is 250-350 ℃, the heating rate is 1 ℃/min, and the idle firing time is 3-8h.
The preparation method of the metal-free porous nitrogen-oxygen doped carbon-based catalyst comprises the following steps of: the temperature rising rate is 3 ℃/min, the temperature is raised to 500-600 ℃, the temperature is kept for 2-4h, then the temperature is raised to 850-1000 ℃ and the temperature is kept for 2-4h.
The preparation method of the metal-free porous nitrogen-oxygen doped carbon-based catalyst comprises the step of preparing the metal-free porous nitrogen-oxygen doped carbon-based catalyst, wherein the inert atmosphere is one of nitrogen, argon, krypton or xenon.
The preparation method of the metal-free porous nitrogen-oxygen doped carbon-based catalyst comprises the following steps of: stirring in 0.1-1mol/L hydrochloric acid solution at room temperature for 1-10h; and then adopting a suction filtration method, and washing with deionized water for 3-5 times.
The metal-free porous nitrogen-oxygen doped carbon-based catalyst is prepared by adopting any one of the preparation methods.
An application of a metal-free porous nitrogen-oxygen doped carbon-based catalyst is characterized in that the metal-free porous nitrogen-oxygen doped carbon-based catalyst is used as a cathode catalyst and applied to a metal-air battery or a fuel battery.
The beneficial effects are that: the invention provides a metal-free porous nitrogen-oxygen doped carbon-based catalyst, and a preparation method and application thereof. The preparation method comprises the following steps: tannic acid is used as a carbon source, zinc chloride is used as a complexing agent, urea and tris (hydroxymethyl) aminomethane are used as nitrogen sources, sodium chloride is used as molten salt and a pore-forming template, and a spray drying method is used to obtain uniformly mixed first powder; then, pre-crosslinking and activating the first powder by low-temperature idle firing to obtain second powder; finally, the second powder is calcined at high temperature under inert atmosphere to realize pyrolysis carbonization of the powder, and the obtained product is washed to obtain the porous nitrogen-oxygen doped carbon-based catalyst. The preparation method provided by the invention has the advantages of rich raw material resources, simple synthesis method and suitability for large-scale production. The prepared catalyst has a hierarchical porous morphology, is rich in surface defects, and shows excellent electrocatalytic oxygen reduction performance; the catalyst does not contain metal, so that the problem of metal dissolution in the catalytic reaction can be effectively avoided, and the catalyst has excellent stability; meanwhile, compared with the catalyst participated by transition metal and noble metal, the catalyst has obvious cost advantage.
Drawings
FIG. 1 is a schematic flow chart of a method for preparing a metal-free porous nitrogen-oxygen doped carbon-based catalyst according to an embodiment of the present invention;
FIG. 2 is an X-ray diffraction pattern of a metal-free porous nitrogen-oxygen doped carbon-based catalyst prepared in example 1 of the present invention;
FIG. 3 is a scanning electron microscope image of the metal-free porous nitrogen-oxygen doped carbon-based catalyst prepared in example 1 of the present invention;
FIG. 4 is a transmission electron microscope image of the metal-free porous nitrogen-oxygen doped carbon-based catalyst prepared in example 1 of the present invention;
FIG. 5 is an elemental distribution diagram of a metal-free porous nitrogen-oxygen doped carbon-based catalyst prepared in example 1 of the present invention;
FIG. 6 is a graph comparing oxygen reduction catalytic performance of catalysts and commercial platinum carbon prepared in example 1 and comparative example 1, respectively, of the present invention;
FIG. 7 is a graph comparing methanol resistance of a metal-free porous nitrogen-oxygen doped carbon-based catalyst prepared in example 1 of the present invention with commercial platinum carbon;
FIG. 8 is a graph comparing oxygen reduction stability of a metal-free porous nitrogen-oxygen doped carbon-based catalyst prepared in example 1 of the present invention and commercial platinum carbon;
FIG. 9 is a graph of polarization curves and power densities of zinc-air cells assembled from a metal-free porous nitrogen-oxygen doped carbon-based catalyst prepared in example 1 of the present invention and commercial platinum carbon;
FIG. 10 is a schematic diagram of a 10mA/cm zinc-air cell assembled with a metal-free porous nitrogen-oxygen doped carbon-based catalyst prepared in example 1 of the present invention 2 Voltage curve under discharge current density.
Detailed Description
The invention provides a metal-free porous nitrogen-oxygen doped carbon-based catalyst, a preparation method and application thereof, and the invention is further described in detail below for making the purposes, technical schemes and effects of the invention clearer and more definite. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The embodiment of the invention provides a preparation method of a metal-free porous nitrogen-oxygen doped carbon-based catalyst, which is shown in figure 1 and comprises the following steps:
s10, dissolving a carbon source, a nitrogen source, a complexing agent and sodium chloride in a tris buffer solution, and then obtaining uniformly mixed first powder through a spray drying process;
s20, performing blank burning treatment on the first powder to obtain second powder;
s30, carrying out high-temperature calcination treatment on the second powder under the condition of inert atmosphere, and carrying out acid washing and water washing treatment on the obtained product to obtain the metal-free porous nitrogen-oxygen doped carbon-based catalyst.
In some embodiments, the carbon source is tannic acid, the nitrogen source is urea, tris, and the complexing agent is a zinc salt.
In some embodiments, the zinc salt is ZnCl 2 、ZnSO 4 But is not limited thereto.
In other embodiments, the carbon source may also be other macromolecular biomass carbon-based, such as lignin, cellulose, etc., with abundant raw material resources.
The invention uses tannic acid, urea and tris (hydroxymethyl) aminomethane as precursors, sodium chloride as molten salt and pore-forming template, the raw material cost is low, and the preparation cost can be greatly reduced. Nitrogen and oxygen atoms are introduced through non-metal heteroatom doping to manufacture vacancy defects, so that the local electronic structure and geometric configuration of the carbon material are changed, and the regulation and control of catalytic activity are realized.
In some embodiments, the tannic acid to urea mass ratio is (0.5-1.5): 1.
According to the invention, different coordination duty ratios of nitrogen are regulated and controlled by regulating and controlling the addition amount of urea and idle firing pre-activation, and finally, the aim of regulating and controlling the nitrogen content and defect content of a carbon material is achieved, so that the carbon-based catalyst with high oxygen reduction catalytic activity and higher graphite nitrogen pyridine nitrogen duty ratio is obtained, the limiting current density can be improved, the four electron transfer paths are accelerated, and more oxygen vacancy defects are manufactured, thereby improving the ORR performance.
In some embodiments, the mass ratio of sodium chloride to carbon source is (20-60): 1.
In some embodiments, the spray drying process of step S10 has a spray gas flow rate of 5-15L/min, a gas inlet temperature of 110-160deg.C, and a gas outlet temperature of 90-100deg.C.
The invention adopts a molten salt method, and the aperture size and the sheet thickness of the carbon material are regulated and controlled by regulating and controlling the addition amount of molten salt. By utilizing an industrialized mature spray drying process, the raw materials can be uniformly mixed. Meanwhile, the process has mild required conditions and is easy to realize; the preparation method is simple and easy to implement, has low energy consumption and is suitable for industrial production.
In some embodiments, in the idle firing process described in step S20, the idle firing temperature is 250-350 ℃, the heating rate is 1 ℃/min, and the idle firing time is 3-8 hours.
In the invention, the idle burning treatment is used for realizing activation in tannin macromolecules and pre-crosslinking with urea, and more oxygen vacancy defects can be manufactured in the idle burning treatment process, so that the finally prepared catalyst shows excellent oxygen reduction catalytic activity and long-term stability. The nitrogen content and defect content of the carbon material can be regulated and controlled by regulating the air-firing pretreatment temperature.
Specifically, the first powder is placed in a muffle furnace for blank burning treatment,
in some embodiments, the high temperature calcination treatment procedure described in step S30 is: the temperature rising rate is 3 ℃/min, the temperature is raised to 500-600 ℃, the temperature is kept for 2-4h, then the temperature is raised to 850-1000 ℃ and the temperature is kept for 2-4h.
In the invention, the high-temperature calcination is used for preparing the porous nitrogen-doped carbon-based catalyst by realizing pyrolysis carbonization of powder. The high-temperature calcination is a traditional carbonization pyrolysis process, and the preparation method is simple and feasible, has low energy consumption and is suitable for industrial production.
In some embodiments, the inert atmosphere is one of nitrogen, argon, krypton, or xenon.
Preferably, the inert atmosphere is nitrogen or argon.
In some embodiments, the pickling and water-washing treatment procedure described in step S30 is: stirring in 0.1-1mol/L hydrochloric acid solution at room temperature for 1-10h; and then adopting a suction filtration method, and washing with deionized water for 3-5 times.
In some embodiments, the preparation method of the metal-free porous nitrogen-oxygen doped carbon-based catalyst provided by the embodiment of the invention specifically comprises the following steps:
s100, taking tannic acid as a carbon source, zinc salt as a complexing agent, urea and tris (hydroxymethyl) aminomethane as nitrogen sources, sodium chloride as molten salt and a pore-forming template, dissolving in a tris (hydroxymethyl) aminomethane buffer solution, and obtaining uniformly mixed powder by a spray drying method;
s200, placing the obtained powder in a muffle furnace for idle burning pretreatment, wherein the idle burning temperature is 250-350 ℃, the heating rate is 1 ℃/min, and the idle burning time is 3-8h;
and S300, calcining the pretreated powder at a high temperature in an argon atmosphere, and washing the obtained product to obtain the metal-free porous nitrogen-oxygen doped carbon-based catalyst.
The preparation method of the metal-free porous nitrogen-oxygen co-doped carbon-based catalyst provided by the invention comprises the steps of taking tannic acid as a carbon source, zinc chloride as a complexing agent, urea and tris (hydroxymethyl) aminomethane as a nitrogen source, sodium chloride as molten salt and a pore-forming template, and firstly obtaining uniformly mixed powder by a spray drying method; then pre-crosslinking and activating the powder by low-temperature idle firing; finally, the pretreated powder is calcined at high temperature in inert atmosphere to realize pyrolysis carbonization of the powder, and the obtained product is washed with water to obtain the metal-free porous nitrogen-oxygen co-doped carbon-based catalyst. The preparation method disclosed by the invention has the advantages of rich raw material resources, simple synthesis method, strong universality and environment friendliness, and is suitable for large-scale production.
The invention also provides a metal-free porous nitrogen-oxygen doped carbon-based catalyst which is prepared by adopting any one of the preparation methods.
The metal-free porous nitrogen-oxygen doped carbon-based catalyst prepared by the invention has a graded porous morphology, is rich in surface defects, and shows excellent electrocatalytic oxygen reduction performance; the catalyst does not contain metal, so that the problem of metal dissolution in the catalytic reaction can be effectively avoided, and the catalyst has excellent stability; meanwhile, compared with the catalyst participated by transition metal and noble metal, the catalyst has obvious cost advantage.
The invention also provides application of the metal-free porous nitrogen-oxygen doped carbon-based catalyst, wherein the metal-free porous nitrogen-oxygen doped carbon-based catalyst is used as a cathode catalyst and is applied to a metal-air battery or a fuel battery.
In some embodiments, the metal-free porous nitrogen-oxygen doped carbon-based catalyst is applied to catalyze an oxygen reduction reaction.
In some embodiments, the battery is a zinc-air battery.
The zinc-air battery assembled by taking the metal-free porous nitrogen-oxygen doped carbon-based catalyst as a cathode catalyst, and the linear volt-ampere curve and the power density curve which are obtained through testing, and the discharge stability test show the performance equivalent to Pt/C, so that the zinc-air battery has potential application value in the fields of metal-air batteries and fuel batteries.
The following is a further explanation of the metal-free porous nitrogen-oxygen doped carbon-based catalyst, the preparation method and the application thereof by specific examples:
example 1
(1) 5.0g of tannic acid, 6.7g of urea, 2.7g of zinc chloride and 267g of NaCl are weighed and added into 500ml of water solution containing 3.6g of tris (hydroxymethyl) aminomethane, and the mixture is stirred for 6 hours at normal temperature to form a mixed solution;
(2) Spray drying the obtained solution, wherein the flow rate of compressed gas is 5-15ml/min, the temperature of the air inlet is kept at 140 ℃, and the temperature of the air outlet is kept at 90 ℃ to obtain powder substances;
(3) Placing the spray-dried powder in a muffle furnace, heating to 300 ℃ at 1 ℃/min, and performing idle burning for 5 hours;
(4) Placing the powder obtained in the step (3) into a tube furnace, heating to 600 ℃ at a heating rate of 3 ℃/min under argon atmosphere, calcining for 2 hours, heating to 900 ℃ at a heating rate of 3 ℃/min, and calcining for 2 hours; cooling to room temperature, and taking out the product; the obtained product is placed in hydrochloric acid with the concentration of 0.2mol/L for 5 hours, the product is obtained through suction filtration and water washing, and the product is dried for 12 hours in a blowing way at the temperature of 60 ℃ to obtain the metal-free porous nitrogen-oxygen doped carbon-based catalyst.
Example 2
The nitrogen content and defect content of the carbon material are regulated and controlled by regulating and controlling the addition amount of urea and the idle burning pretreatment temperature.
(1) Weighing 5.0g of tannic acid, 10g of urea, 2.7g of zinc chloride and 267g of NaCl, adding into 500ml of aqueous solution containing 3.6g of tris (hydroxymethyl) aminomethane, and stirring for 6 hours at normal temperature to form a mixed solution;
(2) Spray drying the obtained solution, wherein the flow rate of compressed gas is 5-15ml/min, the temperature of the air inlet is kept at 140 ℃, and the temperature of the air outlet is kept at 90 ℃ to obtain powder substances;
(3) Placing the spray-dried powder in a muffle furnace, heating to 250 ℃ at a speed of 1 ℃/min, and performing idle firing for 3 hours;
(4) Placing the powder obtained in the step (3) into a tube furnace, heating to 600 ℃ at a heating rate of 3 ℃/min under argon atmosphere, calcining for 2 hours, heating to 900 ℃ at a heating rate of 3 ℃/min, and calcining for 2 hours; cooling to room temperature, and taking out the product; the obtained product is placed in hydrochloric acid with the concentration of 0.2mol/L for 5 hours, the product is obtained through suction filtration and water washing, and the product is dried for 12 hours in a blowing way at the temperature of 60 ℃ to obtain the metal-free porous nitrogen-oxygen doped carbon-based catalyst.
Example 3
The aperture size and the sheet thickness of the carbon material are regulated and controlled by regulating and controlling the addition amount of the molten salt.
(1) Weighing 5.0g of tannic acid, 6.7g of urea, 2.7g of zinc chloride and 150g of NaCl, adding into 500ml of aqueous solution containing 3.6g of tris (hydroxymethyl) aminomethane, and stirring at normal temperature for 6h to form a mixed solution;
(2) Spray drying the obtained solution, wherein the compressed gas flow is 5-15ml/min, the gas inlet temperature is kept at 140 ℃, and the gas outlet temperature is kept at 90 ℃ to obtain powder substances;
(3) Placing the spray-dried powder in a muffle furnace, heating to 300 ℃ at 1 ℃/min, and performing idle burning for 5 hours;
(4) Placing the powder obtained in the step (3) into a tube furnace, heating to 600 ℃ at a heating rate of 3 ℃/min under argon atmosphere, calcining for 2 hours, heating to 900 ℃ at a heating rate of 3 ℃/min, and calcining for 2 hours; cooling to room temperature, and taking out the product; the obtained product is placed in hydrochloric acid with the concentration of 0.2mol/L for 5 hours, the product is obtained through suction filtration and water washing, and the product is dried for 12 hours in a blowing way at the temperature of 60 ℃ to obtain the metal-free porous nitrogen-oxygen doped carbon-based catalyst.
Comparative example 1
Comparative example 1 does not have the precursor obtained by spray drying subjected to idle firing activation as compared with example 1.
(1) 5.0g of tannic acid, 6.7g of urea, 2.7g of zinc chloride and 267g of NaCl are weighed and added into 500ml of water solution containing 3.6g of tris (hydroxymethyl) aminomethane, and the mixture is stirred for 6 hours at normal temperature to form a mixed solution;
(2) Spray drying the obtained solution, wherein the compressed gas flow is 5-15ml/min, the gas inlet temperature is kept at 140 ℃, and the gas outlet temperature is kept at 90 ℃ to obtain powder substances;
(3) Placing the powder obtained by spray drying into a tube furnace, heating to 600 ℃ at a heating rate of 3 ℃/min under argon atmosphere, calcining for 2 hours, heating to 900 ℃ at a heating rate of 3 ℃/min, and calcining for 2 hours; cooling to room temperature, and taking out the product; the obtained product is placed in 0.2mol/L hydrochloric acid for 5 hours, the product is obtained through suction filtration and water washing, the product is dried for 12 hours in a blowing way at 60 ℃, and a comparison sample is obtained and is named as metal-free porous nitrogen doped carbon.
Performance testing
FIG. 2 is an X-ray diffraction chart of example 1, and it can be seen that the peak intensity of graphite is weaker, which indicates that the graphitization degree of the material is weakened, and that the amorphous phase is increased and the defects are increased; and the graphite peak is left-biased, which indicates that nitrogen is successfully doped into the carbon layer.
Fig. 3, fig. 4, and fig. 5 are morphology diagrams of the catalyst prepared in example 1, and it can be seen that the metal-free porous nitrogen-oxygen doped carbon-based catalyst prepared in example 1 has a morphology-graded spherical porous structure. The elemental distribution pattern shown in fig. 5 advantageously demonstrates that N, O elements are uniformly distributed in the carbon matrix.
FIG. 6 is a graph showing the polarization curve of a catalyst in 0.1M KOH aqueous solution. The test conditions were a scan speed of 10mV/s, a rotational speed of 1600 rpm. The half-wave potential of the metal-free porous nitrogen-oxygen co-doped carbon-based catalyst prepared in the example 1 is 0.86V, and the oxygen reduction catalytic performance is excellent; the metal-free porous nitrogen-doped carbon prepared in comparative example 1 showed poor oxygen reduction performance because the precursor powder was not subjected to the idle firing pretreatment and the defect level of the sample was reduced. Meanwhile, as can be seen from fig. 7 and 8, the porous nitrogen-oxygen co-doped carbon-based catalyst prepared in example 1 has good methanol resistance and stability.
Fig. 9 and 10 are linear volt-ampere curves, power density curves and discharge stability tests of zinc-air batteries assembled by using the samples prepared in example 1 as cathode catalysts. The electrolyte is a mixed solution of 6M KOH and 0.2M zinc acetate. The curve shows that the prepared porous nitrogen-oxygen co-doped carbon-based catalyst shows performance equivalent to Pt/C in a zinc-air battery assembly test, and the potential application value of the porous nitrogen-oxygen co-doped carbon-based catalyst in the fields of metal-air batteries and fuel batteries is demonstrated.
In summary, the invention provides a metal-free porous nitrogen-oxygen doped carbon-based catalyst, and a preparation method and application thereof. According to the preparation method provided by the invention, tannic acid is used as a carbon source, zinc chloride is used as a complexing agent, urea and tris (hydroxymethyl) aminomethane are used as nitrogen sources, sodium chloride is used as molten salt and a pore-forming template, and a spray drying method is adopted to obtain uniformly mixed first powder; then, pre-crosslinking and activating the first powder by low-temperature idle firing to obtain second powder; finally, the second powder is calcined at high temperature under inert atmosphere to realize pyrolysis carbonization of the powder, and the obtained product is washed to obtain the porous nitrogen-oxygen doped carbon-based catalyst. According to the preparation method, a molten salt method is adopted, the uniform mixing of raw materials is realized by using an industrially mature spray drying process, and then the preparation of the porous nitrogen-doped carbon-based catalyst is realized by using a subsequent empty burning activation and carbonization pyrolysis process. In addition, tannic acid, urea, naCl and tris (hydroxymethyl) aminomethane are used as precursors, so that the raw material resources are rich, the cost is low, and the preparation cost can be greatly reduced; the preparation method is simple and easy to implement, has low energy consumption and is suitable for large-scale production. The prepared metal-free porous nitrogen-oxygen co-doped carbon-based catalyst has a graded porous morphology, is rich in surface defects, and shows excellent electrocatalytic oxygen reduction performance; the catalyst does not contain metal, so that the problem of metal dissolution in the catalytic reaction can be effectively avoided, and the catalyst has excellent stability; meanwhile, compared with the catalyst participated by transition metal and noble metal, the catalyst has obvious cost advantage. Moreover, the method is also suitable for synthesis of other macromolecular biomass carbon-based catalysts, such as lignin, cellulose and the like, and has wide application prospect.
It is to be understood that the invention is not limited in its application to the examples described above, but is capable of modification and variation in light of the above teachings by those skilled in the art, and that all such modifications and variations are intended to be included within the scope of the appended claims.
Claims (7)
1. The preparation method of the metal-free porous nitrogen-oxygen doped carbon-based catalyst is characterized by comprising the following steps of:
respectively dissolving a carbon source, a nitrogen source, a complexing agent and sodium chloride in a tris buffer solution, and then obtaining first powder through a spray drying process, wherein the carbon source is tannic acid, the nitrogen source is urea and tris, the complexing agent is zinc salt, and the mass ratio of tannic acid to urea is (0.5-1.5): 1;
performing idle burning treatment on the first powder, wherein the idle burning temperature is 250-350 ℃ and the idle burning time is 3-8h, so as to obtain second powder;
and (3) carrying out high-temperature calcination treatment on the second powder under the inert atmosphere condition, wherein the high-temperature calcination treatment condition is as follows: heating to 500-600deg.C, maintaining for 2-4 hr, then heating to 850-1000deg.C, and maintaining for 2-4 hr;
and (3) stirring the obtained product in 0.1-1mol/L hydrochloric acid solution for 1-10h at room temperature, and then washing with deionized water for 3-5 times by adopting a suction filtration method to obtain the metal-free porous nitrogen-oxygen doped carbon-based catalyst.
2. The method for preparing a metal-free porous nitrogen-oxygen doped carbon-based catalyst according to claim 1, wherein in the spray drying process, the flow rate of spray gas is 5-15L/min, the temperature of an air inlet is 110-160 ℃, and the temperature of an air outlet is 90-100 ℃.
3. The method for preparing the metal-free porous nitrogen-oxygen doped carbon-based catalyst according to claim 1, wherein the temperature rising rate in the blank firing treatment is 1 ℃/min.
4. The method for preparing the metal-free porous nitrogen-oxygen doped carbon-based catalyst according to claim 1, wherein the high-temperature calcination treatment heating rate is 3 ℃/min.
5. The method for preparing a metal-free porous nitrogen-oxygen doped carbon-based catalyst according to claim 1, wherein the inert atmosphere is one of nitrogen, argon, krypton or xenon.
6. A metal-free porous nitrogen-oxygen doped carbon-based catalyst prepared by the method of any one of claims 1-5.
7. The application of the metal-free porous nitrogen-oxygen doped carbon-based catalyst is characterized in that the metal-free porous nitrogen-oxygen doped carbon-based catalyst as claimed in claim 6 is used as a cathode catalyst for a metal-air battery or a fuel battery.
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| CN109759117A (en) * | 2019-02-28 | 2019-05-17 | 合肥工业大学 | A method of nitrogen-doped carbon coating metal nano granule composite material is prepared using carbon fiber |
| CN110556546A (en) * | 2019-09-03 | 2019-12-10 | 武汉工程大学 | Nitrogen and oxygen co-doped hierarchical porous carbon material and preparation method thereof |
| CN111050907A (en) * | 2017-08-23 | 2020-04-21 | 小利兰·斯坦福大学托管委员会 | Highly selective N-and O-doped carbon for electrochemical H2O2 production under neutral conditions |
| CN113896193A (en) * | 2021-08-30 | 2022-01-07 | 中国科学院宁波材料技术与工程研究所 | Surface-modified exfoliated graphite and preparation method and application thereof |
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| JP6289630B2 (en) * | 2013-10-25 | 2018-03-07 | カウンスィル オブ サイエンティフィック アンド インダストリアル リサーチＣｏｕｎｃｉｌ Ｏｆ Ｓｃｉｅｎｔｉｆｉｃ ＆ Ｉｎｄｕｓｔｒｉａｌ Ｒｅｓｅａｒｃｈ | Method for producing nitrogen-doped carbon nanohorn for oxygen reduction electrocatalyst |
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| CN109759117A (en) * | 2019-02-28 | 2019-05-17 | 合肥工业大学 | A method of nitrogen-doped carbon coating metal nano granule composite material is prepared using carbon fiber |
| CN110556546A (en) * | 2019-09-03 | 2019-12-10 | 武汉工程大学 | Nitrogen and oxygen co-doped hierarchical porous carbon material and preparation method thereof |
| CN113896193A (en) * | 2021-08-30 | 2022-01-07 | 中国科学院宁波材料技术与工程研究所 | Surface-modified exfoliated graphite and preparation method and application thereof |
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