A method for preparing a Pt-N-C catalyst by using a nitrogen doping strategy and application thereof

Abstract

The application belongs to the technical field of electrochemical catalyst materials, and particularly relates to a method for preparing a Pt-N-C catalyst by using a nitrogen doping strategy and application. The method uses preparation of emeraldine base polyaniline (EB-PANI), and a precursor is complexed in the EB-PANI chain in a coordination form, and then the complex is subjected to a high-temperature carbonization reaction to obtain a fibrous Pt-N-C catalyst. The application enhances the binding force between Pt and the substrate by using the nitrogen-doped carbon strategy, and simultaneously dopes N into the Pt nanolattice, so that the prepared Pt-N-C catalyst has significantly improved oxygen reduction reaction catalytic activity and stability, and has certain practical value for improving the performance of a direct methanol fuel cell.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical catalyst materials, and particularly relates to a method for preparing a Pt-N-C catalyst by using a nitrogen doping strategy and application thereof. BACKGROUND

[0002] Since the energy crisis occurred in the 1970s, the world has paid more and more attention to the development and utilization of renewable energy. Human beings are constantly exploring renewable, safe and reliable sustainable energy systems, and the society is developing more and more rapidly, and it is more and more urgent to develop more efficient and clean new energy conversion devices to provide a stable guarantee for social and economic development. In this century, human beings have gradually entered a new energy era in which energy development and environmental protection are advancing in parallel. Fuel cells, metal-air batteries and the like are considered to meet the demand for green environmental protection and high energy density conversion, and can realize efficient utilization of renewable energy. Oxygen reduction reaction (ORR) as an important electrode reaction plays a key role in improving the efficiency of such energy storage conversion devices. Generally, noble metals have high catalytic activity due to their easy adsorption of reactants on the surface, and the noble metals are inert metals with low chemical activity, and have stable chemical properties, can resist oxidation and corrosion, and have been developed and applied in catalysts for various reactions for a long time. Among them, Pt-based noble metal catalysts have become the most widely used catalyst in the current acid ORR system due to their outstanding catalytic effect, but the low resource reserves and high preparation cost of Pt seriously hinder its industrial application, and in commercial Pt / C catalysts, Pt nanoparticles are supported on high specific surface area amorphous active carbon, which has the advantages of excellent conductivity and high catalytic activity to a certain extent, but due to the weak interaction between Pt and the substrate carbon material, the commercial Pt / C catalyst will have the phenomenon of migration and agglomeration of Pt nanoparticles under long-term high voltage, and corrosion of the carbon carrier will occur, accompanied by the detachment of Pt nanoparticles from the carrier, thereby affecting the catalytic activity and stability. SUMMARY

[0003] The purpose of the present application is to overcome the shortcomings and deficiencies of the prior art, and to provide a method for preparing a Pt-N-C catalyst by using a nitrogen doping strategy and application thereof.

[0004] The technical scheme adopted by the present application is as follows:

[0005] A method for preparing a Pt-N-C catalyst by using a nitrogen doping strategy, comprising the following steps:

[0006] (1) Preparation of ES-PANI nanofiber: equal amounts of 1 mol L-1 HClO4 aqueous solution were added to two reactors A and B, aniline was added to A and ammonium persulfate was added to B, and the solutions were uniformly ultrasonicated and stirred, then the B solution was added to the A solution after the temperature of the two solutions was reduced to 0-5 ℃, and the polymerization was performed for 24 hours, and then the ES-PANI nanofiber was obtained after washing and drying;

[0007] (2) Preparation of EB-PANI nanofiber: the ES-PANI nanofiber prepared in step (1) was subjected to deprotonation treatment to obtain the EB-PANI nanofiber;

[0008] (3) The precursor of Pt was added to the EB-PANI nanofiber prepared in step (2) for impregnation, and after washing and drying, the product was subjected to high-temperature carbonization treatment to obtain the fibrous Pt-N-C catalyst.

[0009] The method for preparing the Pt-N-C catalyst by using the nitrogen doping strategy, in step (1) of the method, the concentration of the aniline is 0.1-0.3 mol L-1, and the molar ratio of the ammonium persulfate to the aniline is 1:1-1:2.

[0010] The method for preparing the Pt-N-C catalyst by using the nitrogen doping strategy, in step (1) of the method, the ammonium persulfate solution of the B solution is slowly added dropwise to the aniline solution of the A solution.

[0011] The method for preparing the Pt-N-C catalyst by using the nitrogen doping strategy, in step (1) of the method, the solution temperature needs to be kept at 0-5 ℃ during the polymerization process.

[0012] The method for preparing the Pt-N-C catalyst by using the nitrogen doping strategy, in step (2) of the method, the ES-PANI nanofiber is soaked in excess 1 mol L-1 ammonia water for deprotonation treatment.

[0013] The method for preparing the Pt-N-C catalyst by using the nitrogen doping strategy, in step (3) of the method, the precursor used is PtCl4, and the mass ratio of the PtCl4 to the EB-PANI nanofiber is 1:2-1:5.

[0014] The method for preparing the Pt-N-C catalyst by using the nitrogen doping strategy, in step (3) of the method, the precursor of Pt is adsorbed onto the EB-PANI nanofiber by using the adsorption between the EB-PANI and the Lewis acid.

[0015] The method for preparing the Pt-N-C catalyst by the nitrogen-doping strategy has the carbonization temperature of 800 DEG C to 950 DEG C in the step (3), and the carbonization time is 2 hours, and the nitrogen is used as the protective atmosphere.

[0016] The application of the Pt-N-C catalyst prepared by the nitrogen-doping strategy as a redox electrocatalyst.

[0017] Beneficial effects:

[0018] The application adopts the carbon carrier enhancement strategy, combines the Pt-based catalyst with the carrier which is surface-modified and improved, changes the surface state of carbon by element doping and improving the graphitization degree of carbon material, and then enhances the stability of the carbon carrier, and firmly anchors the Pt nanoparticles on the surface of the carrier through the chemical bond, so that the catalytic activity and stability of Pt under the acid and cathode high potential are improved. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. The drawings in the following description are only some embodiments of the present application, and other drawings obtained from the drawings still belong to the scope of the present application.

[0020] Figure 1 The Fourier transform infrared spectrum of the EB-PANI obtained after the deprotonation of the ES-PANI;

[0021] Figure 2 The transmission electron microscope photo of the Pt-N-C catalyst prepared in example 1;

[0022] Figure 3 The high-resolution transmission electron microscope (a-b) of the Pt-N-C prepared in example 1, the fast Fourier transform (c) and the crystal plane dislocation enlarged view (d) corresponding to the region in the (b) frame;

[0023] Figure 4 The oxygen reduction polarization curve (a) of the Pt-N-C and the commercial Pt / C prepared in example 1, the mass ratio activity and half-wave potential comparison diagram of the commercial Pt / C and the Pt-N-C under the polarization voltage of 0.9 V (b), the Pt 4f XPS spectrum of the commercial Pt / C (c) and the Pt-N-C (d);

[0024] Figure 5 The hydrogen evolution curve of the Pt-N-C catalyst prepared in example 1;

[0025] Figure 6Oxygen reduction reaction test curves of the Pt-N-C catalysts prepared using different Pt precursors for Example 1 and Example 2;

[0026] Figure 7 X-ray diffraction patterns of the Pt-N-C catalysts prepared for Example 3-6;

[0027] Figure 8 X-ray photoelectron spectroscopy of N 1s of N-C prepared for Example 7-10, the pie chart inserted in a-d is a schematic diagram of the proportion of each N type;

[0028] Figure 9 X-ray photoelectron spectroscopy of N 1s of Pt-N-C prepared for Example 3-6, the pie chart inserted in a-d is a schematic diagram of the proportion of each N type;

[0029] Figure 10 Oxygen reduction curves (a) of the Pt-N-C catalysts prepared for Example 3-6, Tafel curves (b), Raman spectra of N-C prepared for Example 7-10 (c) and Raman spectra of Pt-N-C prepared for Example 3-6 (d). DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings.

[0031] Example 1

[0032] 200 mL of 1 mol L -1 HClO4 aqueous solution was added to two beakers A and B, aniline was added to A and ammonium persulfate was added to B, and they were ultrasonically and uniformly stirred, and after the temperature of the two solutions A and B was reduced to 2.5 ℃, the B solution was added dropwise into the A solution, and polymerization was carried out for 24 hours, and the solution temperature needed to be kept at 2.5 ℃ during the polymerization process. The concentration of aniline in the solution was 0.1 mol L -1 , and the molar ratio of ammonium persulfate to aniline was 1:1, and after the polymerization was completed, the product was washed several times with deionized water and ethanol, and dried to obtain ES-PANI nanofibers.

[0033] The obtained ES-PANI nanofibers were added to excess 1 mol L -1 ammonia solution (about 0.1 g of ES-PANI was added to 500 mL of ammonia solution), stirred overnight, and then suction filtered, and 1 mol L -1The ES-PANI nanofiber is washed with ammonia water for several times to completely deprotonate the ES-PANI, and then the filtered product is placed in a vacuum drying oven and dried at 80℃ overnight to obtain a deprotonated deep blue product EB-PANI nanofiber. The Fourier transform infrared spectra of the obtained EB-PANI nanofiber and the ES-PANI nanofiber are shown in Figure 1 .

[0034] The effect of deprotonation of the ES-PANI nanofiber with ammonia water is studied, as shown in Figure 1 , the absorption band at 1288 cm -1 corresponds to the C-N stretching vibration in the benzene structure -NH-(C6H4)-NH-, and the absorption band at 1225 cm -1 is attributed to the stretching vibration of C-N + in the polaron structure, which is a characteristic of the conductive protonated form. In the ES-PANI nanofiber, the stretching vibration of C-N + is very obvious, but after deprotonation, the C-N + stretching vibration of the EB-PANI nanofiber is significantly weakened, indicating that the deprotonation of the ES-PANI nanofiber has been completed.

[0035] PtCl4 and the EB-PANI nanofiber are added to 50 mL of acetonitrile solvent and stirred overnight to promote the adsorption of PtCl4 and the EB-PANI nanofiber, and the mass ratio of Pt to the EB-PANI nanofiber in the precursor is maintained at 1:2. After sufficient stirring for 12 hours, the solution is filtered, the product is washed with acetonitrile for several times, and then the product is placed in a vacuum drying oven and dried at 85℃ overnight, and then placed in a tube furnace for high-temperature carbonization treatment to obtain a fibrous Pt-N-C catalyst. Under the protection of a nitrogen atmosphere, the heating rate is 5℃ min -1 , the carbonization time is 2 hours, and the carbonization temperature is 800℃. The Pt-N-C catalyst obtained in this embodiment is applied as a redox electrocatalyst.

[0036] The transmission electron microscope of the product obtained by the carbonization reaction is shown in Figure 2As shown, it can be seen that the prepared Pt-N-C catalyst is nanowire, the nanowire diameter is about 80-120 nm, the Pt nanoparticles are uniformly distributed on the surface of the nanowire, the particle size is about 1.5-7 nm, most of the Pt particle size is about 2.5 nm, accompanied by individual larger size (6.5 nm) nanoparticles, but after high temperature carbonization, there are still some 1.5 nm Pt nanoclusters (red circle marked). Generally, Pt nanoparticles with a particle size of about 3 nm are considered to have the most catalytic activity, but small size Pt nanoclusters increase the specific surface area of the catalyst, which is beneficial to improve the Pt utilization.

[0037] The high-resolution transmission electron microscopy of the product obtained by carbonization is as shown in Figure 3 a, the lattice fringes of Pt are clearly visible, Figure 3 b shows an enlarged view of the larger Pt nanoparticles in 3a, by measuring, the average interplanar spacing of the middle region of the nanoparticles is 0.196 nm, which corresponds to the Pt (200) crystal plane, and the (200) crystal plane has higher catalytic activity relative to the low-index Pt nanoparticles. At the edge of the particle size, the (200) interplanar spacing increases to 0.229 nm, which is 16.8% higher than the interplanar spacing at the middle position. The boxed area in 3b was subjected to fast Fourier transform, and the results are shown in Figure 3 c, the diffraction point pointed by the arrow in the figure is the Pt (200) crystal plane, and by magnifying the boxed area in Figure 3 b, it can be seen that Figure 3 d shows that the crystal has obvious surface defects, and the lattice distortion can be clearly observed at the junction of different interplanar spacings, and the distortion angle is about 17°, and the interplanar spacing at the edge is increased, because the pyridine N atom is doped into the Pt atom lattice, which increases the interplanar spacing of the Pt lattice, and produces lattice distortion and tensile strain effect.

[0038] Figure 4 The ORR comparison diagram of the Pt-N-C catalyst prepared in this embodiment and the commercial Pt / C catalyst, under the same loading (m Pt =25 μg cm -2 ), as shown in Figure 4 a, the catalytic activity of Pt-N-C is obviously higher, the overpotential of oxygen reduction reaction is smaller, the half-wave potential is positively shifted by 43 mV compared with the commercial JM 60% Pt / C catalyst, and the limiting diffusion current density is larger, which indicates that Pt-N-C optimizes the mass transfer process of ORR. Figure 4b is the mass specific activity (current corresponding to 0.9 V polarization voltage) and half-wave potential of commercial JM 60% Pt / C and Pt-N-C, from which it can be seen from the figure that the ORR half-wave potential of Pt-N-C is 0.909 V, and that of commercial JM 60% Pt / C is only 0.867 V. At the same time, the mass specific activity of Pt-N-C is 168.8 mA mg-1, which is 4.57 times that of commercial JM 60% Pt / C (MA = 36.9 mA mg-1), indicating that Pt-N-C has higher ORR catalytic efficiency. This may be due to the smaller average particle size of Pt-N-C and the coordination synergistic effect with the substrate, thereby improving the catalytic efficiency. Figure 4 c is the peak fitting diagram of Pt 4f of the commercial Pt / C catalyst, and it can be seen that most (75.1%) of the Pt in the commercial Pt / C exists in the form of metal single element, and only 24.9% of the Pt exists in the form of Pt δ+ Valence state, because the Pt surface is occupied by oxygen in the air, and part of the oxygen is oxidized to platinum oxide under the condition of long-time placement of the Pt / C catalyst. The surface electronic state of Pt in the Pt-N-C catalyst prepared in the present application is different after high-temperature carbonization, as shown in Figure 4 d, only 58.8% of the Pt in Pt-N-C exists in the form of metal single element, which is lower than that of the commercial Pt / C, and the proportions of Pt2+ and Pt4+ are 24.4% and 16.8%, respectively. The XPS results show that part of the Pt in the Pt-N-C catalyst exists in the form of coordination, so that small particles of Pt are anchored on the carbon carrier to achieve a stable state.

[0039] Figure 5 The hydrogen evolution test curve of the Pt-N-C catalyst prepared in the present embodiment is shown in -2 It can be seen that the Pt-N-C catalyst prepared in the present embodiment also has certain hydrogen evolution activity.

[0040] Example 2

[0041] The difference between the present embodiment and Example 1 is that cis-(CH3CN)2PtCl2 (cis-bis-acetonitrile platinum dichloride) is used instead of PtCl4 in Example 1 to study the influence of different Pt precursors on the ORR performance of the prepared Pt-N-C catalyst, and the obtained ORR test curve is shown in Figure 6

[0042] When the content of Pt incorporated is the same, Figure 6 ​It can be seen that when PtCl4 is introduced into polyaniline as a Pt source, it has superior ORR performance, but cis- (CH3CN)2PtCl2 as a Pt source has almost no electrocatalytic activity for ORR, which is caused by the difference in the strength of Lewis acid between PtCl4 and cis- (CH3CN)2PtCl2. The strength of Lewis acid can be defined as the size of the tendency to accept a pair of lone electrons, and if the tendency to accept a lone pair of electrons is large, the acid is strong. The more charges Pt carries, the greater the tendency to attract electrons, and the stronger the acid. In PtCl4, one Pt atom is coordinated with four Cl atoms, and because Cl belongs to halogen atoms with high electronegativity, the electron density in the Pt-Cl bond is pulled towards the Cl atom, increasing the positive charge of the Pt atom, and thus enhancing the acidity of PtCl4. In cis- (CH3CN)2PtCl2, Pt exists in the valence state of Pt (II), and there are only two Cl atoms in the molecule, so the number of charges carried by Pt in PtCl4 is greater than that of Pt in cis- (CH3CN)2PtCl2. Therefore, the Lewis acid strength of the two precursors is PtCl4 > cis- (CH3CN)2PtCl2. As a weaker Lewis acid, cis- (CH3CN)2PtCl2 has poorer complexing ability with EB-PANI, lower adsorption efficiency, and greatly reduced catalytic activity. Therefore, PtCl4 is used as a precursor in the present application.

[0043] Examples 3-6:

[0044] The carbonization temperature in Example 1 was set to 800 ℃, 850 ℃, 900 ℃, and 950 ℃, respectively, to explore the effect of different carbonization temperatures on the performance of Pt-N-C catalysts, and the resulting products were denoted as Pt-N-C-800, Pt-N-C-850, Pt-N-C-900, and Pt-N-C-950, respectively.

[0045] Figure 7 The X-ray diffraction patterns of the Pt-N-C catalysts prepared in Examples 3-6 and the commercial Pt / C, and the Pt crystal size are directly related to the carbonization temperature. Generally, when the carbonization temperature increases, Pt is more likely to sinter and agglomerate, resulting in the growth of larger Pt nanoparticles. The XRD test results of Pt-N-C carbonized at 800 ℃, 850 ℃, 900 ℃, and 950 ℃ in the present application are as follows: Figure 7As shown, the diffraction peaks at 2θ of 39.763°, 46.243°, 67.454°, 81.286° correspond to Pt (111), (200), (220), (311) crystal faces, respectively. It can be seen from the figure that the diffraction peaks are enhanced with the increase of carbonization temperature, indicating that the crystallinity of Pt is improved, and Pt may gradually grow into larger nanocrystals.

[0046] Examples 7~10:

[0047] The EB-PANI product obtained in Example 1 was subjected to carbonization treatment, under the protection of a nitrogen atmosphere, the heating rate was 5 ℃ min -1 , the carbonization time was 2 hours, and the carbonization temperature was set to 800 ℃, 850 ℃, 900 ℃, and 950 ℃, respectively, and the obtained products were denoted as N-C-800, N-C-850, N-C-900, and N-C-950, respectively.

[0048] In order to study the types and proportions of N in the N-C materials obtained at different carbonization temperatures in Examples 7~10, the N 1s of the N-C catalysts obtained at 800 ℃, 850 ℃, 900 ℃, and 950 ℃ were characterized by XPS, and the types and contents of N are shown in Figure 8 As can be seen from the pie chart, with the increase of carbonization temperature, the proportion of pyridine N in N-C gradually decreases, the proportion of pyrrole N changes nearly gradually increases, and the proportion of graphite N first decreases and then increases with the increase of temperature.

[0049] The N 1s of the Pt-N-C in Examples 3~6 was further analyzed by XPS in the present application, and the possible combination mode of Pt and N was inferred from the proportion change of N types, and the XPS results are as follows: Figure 9It can be seen that when the carbonization temperature is 800℃, 850℃ and 900℃, the proportion of pyridine N in Pt-N-C is reduced compared with N-C obtained at the same carbonization temperature, which is reduced from 32% to 18% at 800℃, from 30% to 17% at 850℃, and from 27% to 20% at 900℃. At the same time, due to the reduction of the proportion of pyridine N, the proportions of pyrrole N and graphite N are increased accordingly. The XPS results show that when the carbonization temperature is lower than 950℃, Pt may be coordinated with pyridine N, resulting in a significant reduction in the content of pyridine N after the introduction of Pt. However, from the trend of the reduction of the content of pyridine N, it can be seen that when the temperature is increased, the coordination "efficiency" between Pt and pyridine N is reduced. When the carbonization temperature is increased to 950℃, the proportion of graphite N is reduced, and the proportions of pyridine N and pyrrole N are increased accordingly. At this time, the coordination between Pt and N may have changed from being combined with pyrrole N to being combined with a small part of graphite N, resulting in a change in the catalytic performance of Pt-N-C-950, and the ORR activity is lower than that of Pt-N-C-900 Figure 10 a), which may be due to the fact that the catalytic activity of the active site formed by Pt at pyridine N is better than that of the active site formed by combining with graphite N. The XPS results partially explain the difference in catalytic activity in Figure 10 a and Figure 10 b, and therefore the optimal carbonization condition is 900℃.

[0050] Figure 10 a is the performance characterization of the Pt-N-C catalyst prepared in examples 3-6. It can be seen that as the carbonization temperature increases, the graphitization degree of the catalyst increases, thereby improving the conductivity of the material, so that the ORR half-wave potential of Pt-N-C is positively shifted and the limiting diffusion current density gradually increases. When the temperature is increased to 950℃, the ORR performance is reduced, which may be due to the fact that when the carbonization temperature is too high, the catalyst is sintered and agglomerated, resulting in a reduction in catalytic activity. The catalytic activity of Pt-N-C-900 is the highest, and the half-wave potential reaches 0.909 V, Figure 10 b is the Tafel curve of the corresponding Pt-N-C, and the slope size is Pt-N-C-800>Pt-N-C-850>Pt-N-C-950>Pt-N-C-900 in turn. The Pt-N-C catalyst obtained at 900℃ has more favorable conditions for the occurrence of oxygen reduction reaction. In order to study the structural characteristics of Pt-N-C, the present application analyzes the Raman spectrum of N-C and Pt-N-C prepared at different temperatures in examples 3-10 in the range of 500-2000 cm -1 . Figure 10cRaman spectra of N-C at different carbonization temperatures in Examples 7-10, 1350 cm -1 nearby and 1583 cm -1 nearby correspond to disordered graphite band (I D ) and crystalline graphite band (I G ), respectively. The D peak represents the degree of defects of the material, the stronger the D peak, the greater the defects, while the G peak is caused by the stretching vibration between carbon atoms, representing the degree of graphitization of the material, the stronger the G peak, the higher the degree of graphitization of the material. It is calculated that with the increase of pyrolysis temperature, the I D / I G of N-C gradually increases (1.09, 1.20, 1.25, 1.26, respectively), indicating that higher pyrolysis temperature makes N-C have more defects, at the same time, with the increase of pyrolysis temperature, the position of D peak and G peak does not shift obviously, indicating that the carbon structure in the material does not change significantly. After the introduction of Pt, as shown in Figure 10 d, this law does not change, but the value of I D / I G increases on the basis of N-C (1.18, 1.23, 1.27, 1.31, respectively), indicating that the introduction of Pt makes the catalyst form more C defects in the pyrolysis process, thereby facilitating the capture of N atoms.

[0051] Example 11

[0052] The difference between this embodiment and embodiment 1 is that 200 mL of 1 mol L-1 HCIO4 aqueous solution is added to two beakers A and B respectively, aniline is added to A and ammonium persulfate is added to B, and they are uniformly ultrasonicated and stirred, then the temperature of the two solutions is reduced to 0 ℃, the B solution is added dropwise into the A solution, and polymerization is carried out for 24 hours, and the solution temperature needs to be kept at 0 ℃ during the polymerization. The concentration of aniline in the solution is 0.2 mol L-1, the molar ratio of ammonium persulfate to aniline is 1:2, and after the polymerization is completed, the product is washed with deionized water and ethanol several times, and then dried to obtain ES-PANI nanofibers. The obtained ES-PANI nanofibers are added to excess 1 mol L-1 ammonia solution and stirred overnight, then suction filtered, and washed with 1 mol L-1 ammonia several times to completely deprotonate the ES-PANI to obtain deprotonated deep blue product EB-PANI nanofibers. PtCI4 and EB-PANI nanofibers are added to 50 mL acetonitrile solvent and stirred overnight, and the mass ratio of Pt to EB-PANI nanofibers in the precursor is kept at 1:3. After sufficient stirring for 12 hours, the solution is suction filtered, and the product is washed several times with acetonitrile as a washing agent, then the product is placed in a vacuum drying oven and dried overnight, and then placed in a tube furnace for high-temperature carbonization treatment to obtain fibrous Pt-N-C catalyst.

[0053] Example 12

[0054] The difference between this embodiment and embodiment 1 is that 200 mL of 1 mol L-1 HCIO4 aqueous solution is added to two beakers A and B respectively, aniline is added to A and ammonium persulfate is added to B, and they are uniformly ultrasonicated and stirred, then the temperature of the two solutions is reduced to 0 ℃, the B solution is added dropwise into the A solution, and polymerization is carried out for 24 hours, and the solution temperature needs to be kept at 0 ℃ during the polymerization. The concentration of aniline in the solution is 0.2 mol L-1, the molar ratio of ammonium persulfate to aniline is 1:2, and after the polymerization is completed, the product is washed with deionized water and ethanol several times, and then dried to obtain ES-PANI nanofibers. The obtained ES-PANI nanofibers are added to excess 1 mol L-1 ammonia solution and stirred overnight, then suction filtered, and washed with 1 mol L-1 ammonia several times to completely deprotonate the ES-PANI to obtain deprotonated deep blue product EB-PANI nanofibers. PtCI4 and EB-PANI nanofibers are added to 50 mL acetonitrile solvent and stirred overnight, and the mass ratio of Pt to EB-PANI nanofibers in the precursor is kept at 1:3. After sufficient stirring for 12 hours, the solution is suction filtered, and the product is washed several times with acetonitrile as a washing agent, then the product is placed in a vacuum drying oven and dried overnight, and then placed in a tube furnace for high-temperature carbonization treatment to obtain fibrous Pt-N-C catalyst.

[0055] The foregoing merely illustrates the principles of the application and application of its principles. This description should not be taken as limiting the scope of the claims. Any variations and modifications of the examples described herein can be made by those skilled in the art without departing from the scope of the application as recited in the following claims.

Claims

1. A method for preparing a Pt-N-C catalyst using a nitrogen doping strategy, characterized in that, The method comprises the following steps: (1) Preparation of ES-PANI nanofiber: equal amounts of 1 mol L-1 HClO4 aqueous solution are added to two reactors A and B, aniline is added to reactor A and ammonium persulfate is added to reactor B, and the solutions are uniformly ultrasonicated and stirred, then the solution B is added to the solution A after the temperature of the two solutions is reduced to 0-5℃, and the polymerization is carried out for 24 hours, and the ES-PANI nanofiber is obtained after washing and drying; (2) Preparation of EB-PANI nanofiber: the ES-PANI nanofiber prepared in step (1) is subjected to deprotonation treatment to obtain the EB-PANI nanofiber; (3) The precursor of Pt is added to the EB-PANI nanofiber prepared in step (2) for impregnation, and the product is subjected to carbonization treatment to obtain the fibrous Pt-N-C catalyst after washing and drying; In step (1), the concentration of the aniline is 0.1-0.3 mol L-1, and the molar ratio of ammonium persulfate to aniline is 1:1-1:2; In step (1), the ammonium persulfate solution of the solution B is slowly added dropwise to the aniline solution of the solution A; In step (1), the temperature of the solution is kept at 0-5℃ during the polymerization process; In step (2), the ES-PANI nanofiber is immersed in excess 1 mol L-1 ammonia water for deprotonation treatment.

2. The method for preparing a Pt-N-C catalyst by a nitrogen-doping strategy according to claim 1, characterized in that: In step (3), the precursor used is PtCl4, and the mass ratio of PtCl4 to EB-PANI nanofiber is 1:2-1:

5.

3. The method for preparing a Pt-N-C catalyst by a nitrogen-doping strategy according to claim 1, characterized in that: In step (3), the precursor of Pt is adsorbed onto the EB-PANI nanofiber by using the adsorption between EB-PANI and Lewis acid.

4. The method for preparing a Pt-N-C catalyst by a nitrogen-doping strategy according to claim 1, characterized in that: In step (3), the carbonization temperature is 800-950℃, and the carbonization time is 2 hours, and nitrogen is used as the protective atmosphere.

5. Use of the Pt-N-C catalyst prepared by the nitrogen doping strategy as an oxidation-reduction electrocatalyst.

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