Monatomic carbon-based catalyst precursor material and preparation method thereof, monatomic carbon-based catalyst and preparation method and application thereof

Abstract

The invention relates to the field of catalysts, in particular to a monatomic carbon-based catalyst precursor material, a preparation method of the monatomic carbon-based catalyst precursor material, a monatomic carbon-based catalyst and a preparation method and application of the monatomic carbon-based catalyst. The general formula of the precursor material is transition metal-COP (at) PC, the PC is honeycomb 3D porous carbon, characteristic peaks of 1705 + / -0.5 cm <-1 >, 1317 + / -0.5 cm <-1 >, 714 + / -0.5 cm <-1 > and 2230 + / -0.5 cm <-1 > exist in an FTIR spectrogram of the transition metal-COP, and the mass ratio of the transition metal-COP to the honeycomb 3D porous carbon in the catalyst is 1: (0.5-2). The transition metal-COP material with specific FTIR spectrogram characteristics and composition is loaded on the honeycomb-shaped 3D porous carbon, and the obtained material has excellent solution machinability.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and particularly relates to a single-atom carbon-based catalyst precursor material, a preparation method thereof, a single-atom carbon-based catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] The deterioration of the energy crisis and the environmental degradation caused by the combustion of fossil fuels have promoted the exploration of renewable energy conversion technologies. Proton exchange membrane fuel cells (PEMFCs) are considered to be one of the main forces for the next-generation new energy conversion because the water produced is clean and pollution-free and has high energy efficiency. However, compared with the oxidation reaction of fuel at the anode, the kinetically sluggish oxygen reduction reaction (ORR) occurring at the cathode of PEMFCs is the main bottleneck. Metal single-atom materials have become the most promising ORR catalysts due to their unique catalytic properties.

[0003] Numerous literatures have proven that single-atom characteristics, coordination environment, and metal atom loading are the main reasons affecting the activity of single-atom catalysts. Increasing the metal loading while maintaining atomic dispersion is an effective strategy to further improve the catalytic performance. The surface free energy of metals increases significantly as the particle size decreases, leading to the continuous formation of clusters and less active nanoparticles. Various schemes for preparing single-atom catalysts by anchoring metal atoms on supports have been proposed, such as the fabrication of metal-organic frameworks (MOFs), the proposal of the concept of spatial confinement, defect engineering of metal oxide and hydroxide supports, and the utilization of strong interactions between metal species and various heteroatoms (such as nitrogen, sulfur, and oxygen). However, these methods still cannot strictly exclude metal aggregation, and in many cases, further acid etching and secondary carbonization and other means are required for treatment. These procedures not only complicate the experimental process but also randomly create single-atom active sites on the support, resulting in low reproducibility.

[0004] In addition, the performance of the catalyst not only depends on the intrinsic activity and concentration of the catalyst but is also closely related to the utilization rate of the active sites. Summary of the Invention

[0005] The object of the present invention is to overcome the problems of low loading, low activity, and low utilization rate of active sites of single-atom catalysts existing in the prior art, and to provide a single-atom carbon-based catalyst precursor material, a preparation method thereof, a single-atom carbon-based catalyst, a preparation method thereof, and an application thereof. The single-atom carbon-based catalyst precursor material has excellent solution processing performance.

[0006] To achieve the above object, in the first aspect of the present invention, a single-atom carbon-based catalyst precursor material is provided. The general formula of the precursor material is transition metal-COP@PC, where PC is honeycomb-like 3D porous carbon, and there is 1705±0.5 cm in the FTIR spectrum of transition metal-COP-1 、1317 ± 0.5 cm -1 、714 ± 0.5 cm -1 and 2230 ± 0.5 cm -1 characteristic peaks, and the mass ratio of transition metal-COP to honeycomb 3D porous carbon in the catalyst is 1:0.5 - 2.

[0007] In the second aspect of the present invention, a preparation method of the precursor material described in the first aspect is provided. The preparation method includes the following steps: (1) preparing a dispersion of honeycomb 3D porous carbon; (2) adding the dispersion of honeycomb 3D porous carbon into an Fe-COP solution for mixing, filtering, and then drying under vacuum; the mass ratio of honeycomb 3D porous carbon to Fe-COP is 0.5 - 2:1.

[0008] In the third aspect of the present invention, a single-atom carbon-based catalyst is provided. The catalyst includes a honeycomb 3D porous carbon carrier and an active component supported on the carrier. The active component contains a transition metal atom-nitrogen co-doped carbon-based material; there are no characteristic peaks of transition metal oxides in the XRD spectrum of the catalyst; in the Raman spectrum of the catalyst I D / I G value is not greater than 1.3, where I D is the peak intensity of the peak with a Raman shift value of 1350 cm -1 and I G is the peak intensity of the peak with a Raman shift value of 1600 cm -1 .

[0009] In the fourth aspect of the present invention, a preparation method of the catalyst described in the third aspect is provided. The preparation method includes: carbonizing the precursor material described in the first aspect under an inert atmosphere.

[0010] In the fifth aspect of the present invention, an application of the catalyst described in the third aspect as an oxygen reduction catalyst in a proton exchange membrane fuel cell is provided.

[0011] Through the above technical solutions, the present invention has the following advantages: The present invention loads a transition metal-COP material with specific FTIR spectrum characteristics and composition on honeycomb 3D porous carbon, and the obtained material has excellent solution processability.

[0012] There are no characteristic peaks of transition metal oxides in the XRD spectrum of the single-atom carbon-based catalyst of the present invention, and in the Raman spectrum I D / I GThe value is not greater than 1.3, and the catalyst has excellent catalytic activity.

[0013] The preparation method of the catalyst of the present invention can effectively prevent the aggregation of metals during the preparation process and improve the loading amount of single-atom metals in the catalyst.

[0014] When the catalyst of the present invention is used in a proton exchange membrane fuel cell, the ORR catalytic efficiency and high-voltage stability are significantly improved. Specifically, when the transition metal is Fe, the ORR half-wave potential of the catalyst is as high as 0.827 V in 0.1 M HClO4 electrolyte, and its maximum power density reaches 1.04 W cm in PEMFCs. 2 Moreover, in PEMFCs under H2-air conditions, after a 100-hour membrane electrode life test at a high voltage of 0.75 V, the current density can still maintain 75% of the original. The active center atoms are evenly distributed at the three-phase reaction interface, truly realizing the atomic economy of the catalyst at the device level, and opening up new ideas for the assembly and application of high-performance fuel cell devices. Description of the Drawings

[0015] Figure 1 Among them, (a) is the Fourier transform infrared spectrum of Fe-COP prepared in Example 2; (b) is the thermogravimetric diagram of the catalyst prepared in Example 2, the catalyst prepared in Comparative Example 1, and the catalyst prepared in Comparative Example 2 under N2 atmosphere; (c) is the XRD spectrum of the catalyst prepared in Example 2, the catalyst prepared in Comparative Example 1, and the catalyst prepared in Comparative Example 2; (d) is the Raman spectrum of the catalyst prepared in Example 2, the catalyst prepared in Comparative Example 1, and the catalyst prepared in Comparative Example 2. Figure 2 Among them, (a) is the N2 adsorption-desorption isotherm diagram of the honeycomb three-dimensional porous carbon prepared in Example 1, the catalyst prepared in Example 2, the catalyst prepared in Comparative Example 1, and the catalyst prepared in Comparative Example 2; (b) is the pore size distribution curve diagram of the honeycomb three-dimensional porous carbon prepared in Example 1, the catalyst prepared in Example 2, the catalyst prepared in Comparative Example 1, and the catalyst prepared in Comparative Example 2. Figure 3 Among them, (a) is the SEM image of the Fe-ZIF@PC composite material prepared in Comparative Example 1; (b) is the SEM image of the Fe-MOF@PC composite material prepared in Comparative Example 2; (c) is the TEM image of the catalyst prepared in Comparative Example 1; (d) is the TEM image of the catalyst prepared in Comparative Example 2. Figure 4Among them, (a) is the SEM image of the catalyst prepared in Example 2; (b) is the SEM image of the catalyst prepared in Example 2; (c) is the elemental mapping image of the catalyst prepared in Example 2; (d) is the aberration-corrected HAADF-STEM image of the catalyst prepared in Example 2; (e) is the EELS spectrum of the catalyst prepared in Example 2; (f) is the EDX spectrum of the catalyst prepared in Example 2; Figure 5 Among them, (a) is the N 1s high-resolution XPS spectrum of the catalyst prepared in Example 2; (b) is the Fe K-edge XANES spectra of the catalyst prepared in Example 2, Fe foil and Fe2O3; Figure 6 Among them, (a) are the CV curves of the catalyst prepared in Example 2, the catalyst prepared in Comparative Example 1, and the catalyst prepared in Comparative Example 2 in 0.1 M HClO4 solution with N2; (b) are the CV curves of the catalyst prepared in Example 2, the catalyst prepared in Comparative Example 1, and the catalyst prepared in Comparative Example 2 in 0.1 M HClO4 solution with O2; Figure 7 Among them, (a) are the ORR polarization curves of the catalyst prepared in Example 2, the catalyst prepared in Comparative Example 1, the catalyst prepared in Comparative Example 2, and 20% Pt / C catalyst; (b) are the corresponding values of the catalysts prepared in Example 2, Example 4, Comparative Example 1, Comparative Example 2, and Comparative Example 3 at 0.75 V J k and E 1 / 2 ; (c) is the Tafel plot corresponding to the RDE polarization curves of the catalyst prepared in Example 2, the catalyst prepared in Comparative Example 1, the catalyst prepared in Comparative Example 2, and 20% Pt / C catalyst; (d) are the H2O2 yields and electron transfer numbers of the catalyst prepared in Example 2 and 20% Pt / C calculated by the RRDE method; (e) are the ORR polarization curves of the catalyst prepared in Example 2, the catalyst prepared in Example 4, and the catalyst prepared in Comparative Example 3; Figure 8 Among them, (a) is the reaction schematic diagram of PEMFC; (b) is the polarization curve graph of H2-O2 fuel cell; (c) are the Nyquist plots of the catalyst prepared in Example 2, the catalyst prepared in Comparative Example 1, and the catalyst prepared in Comparative Example 2 at 1 A cm -2 current density. Detailed implementation manners

[0016] The endpoints and any values within the ranges disclosed in this document are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the values between the endpoints of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this document.

[0017] The present invention provides a single-atom carbon-based catalyst precursor material, and the general formula of this precursor material is transition metal-COP@PC, where PC is honeycomb 3D porous carbon, and there are characteristic peaks at 1705 ± 0.5 cm -1 、1317 ± 0.5 cm -1 、714 ± 0.5 cm -1 and 2230 ± 0.5 cm -1 in the FTIR spectrum of the transition metal-COP. The mass ratio of the transition metal-COP to the honeycomb 3D porous carbon in the catalyst is 1:0.5 - 2.

[0018] The present invention loads the transition metal-COP material with specific FTIR spectrum characteristics and composition on the honeycomb 3D porous carbon, and the obtained material has excellent solution processability.

[0019] In the present invention, the mass ratio of the transition metal-COP to the honeycomb 3D porous carbon in the catalyst can be, for example, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2. Preferably, the mass ratio of the transition metal-COP to the honeycomb 3D porous carbon in the catalyst is 1:1 - 2.

[0020] According to a preferred embodiment of the present invention, based on the total mass of the precursor material, the content of the honeycomb 3D porous carbon is 40 - 80 wt%, and can be, for example, 50 wt%, 60 wt%, 70 wt%. By adopting the foregoing preference, the solution processability of the material can be further improved.

[0021] According to a preferred embodiment of the present invention, based on the total mass of the precursor material, the content of the transition metal-COP is 20 - 60 wt%, and can be, for example, 30 wt%, 40 wt%, 50 wt%. By adopting the foregoing preference, the solution processability of the material can be further improved.

[0022] In the present invention, the transition metal can be a conventional selection in the art. The following is a demonstration but does not limit the scope of the present invention thereby. According to a preferred embodiment of the present invention, the transition metal is selected from at least one of the Group VIII metals, Group IB metals, and Group VIIB metals.

[0023] According to a preferred embodiment of the present invention, the transition metal is at least one of iron, cobalt, copper, nickel, and manganese, and more preferably iron. By adopting the foregoing preference, the solution processability of the material can be further improved.

[0024] According to a preferred embodiment of the present invention, the proportion of pores with a pore diameter of 80 - 100 nm in the honeycomb 3D porous carbon is not less than 80%, preferably 85 - 95%; the proportion of pores with a pore diameter of 10 - 50 nm is greater than 0 and less than 20%, preferably 5 - 15%.

[0025] According to a preferred embodiment of the present invention, the specific surface area of the honeycomb 3D porous carbon is 500 - 600 m 2 g -1 , for example, 520 m 2 g -1 , 540 m 2 g -1 , 560 m 2 g -1 , 580 m 2 g -1 .

[0026] There is no particular requirement for the preparation method of the precursor material of the present invention, as long as a material with the characteristics of the present invention can be prepared. The following is a demonstration, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the preparation method includes the following steps: (1) preparing a dispersion of honeycomb 3D porous carbon; (2) adding the dispersion of honeycomb 3D porous carbon to a transition metal-COP solution for mixing, filtering, and then vacuum drying; the mass ratio of honeycomb 3D porous carbon to Fe-COP is 0.5 - 2:1, preferably 1 - 2:1.

[0027] In the present invention, there is no particular requirement for the preparation of the dispersion. Generally, the honeycomb 3D porous carbon can be directly mixed with a solvent, and the solvent can be, for example, DMF.

[0028] In the present invention, the honeycomb 3D porous carbon is prepared using mesophase pitch as a carbon source. Specifically, it includes dispersing mesophase pitch in ethanol and / or water, and then dropping a silica template agent, namely a colloidal silica suspension, into the above asphalt dispersion for blending. The preferred blending conditions include: dynamic mixing, a mixing temperature of 10 - 40 °C, and a time of 1 - 5 hours. Subsequently, the solvent is removed by heating, for example, to 80 °C to obtain a dry SiO2 / MP composite material, and then carbonized in an inert atmosphere, such as an N2 atmosphere, at a high temperature of 900 - 1100 °C for 1 - 4 hours. The solid product is reacted with an alkali solution, such as a 3 mol NaOH solution, for 12 - 36 hours to remove the SiO2 template to form nanopores, and then washed with water until neutral, and vacuum dried to obtain the final honeycomb 3D porous carbon.

[0029] In the present invention, the preparation of the transition metal-COP can be a conventional method in the art. In the present invention, an organic ligand such as 4-cyanobenzene is dissolved in an organic solvent such as DMF to obtain solution A. A soluble transition metal salt is dissolved in a solvent such as ethylene glycol and dissolved by ultrasonic treatment to form solution B. Then, solution B is poured into A, and a catalyst such as 1,8-diazabicyclo(5,4,0)undec-7-ene is added during mixing, and the reaction is carried out at 160-200 °C for 20-50 minutes. Subsequently, an acid such as dilute hydrochloric acid is added and allowed to stand to obtain a precipitate, which is centrifuged, washed with ethanol, and freeze-dried.

[0030] According to a preferred embodiment of the present invention, the conditions for mixing in step (2) include: the mixing temperature is 50-80 °C, preferably 60-70 °C, and the mixing time can be adjusted according to factors such as temperature, for example, it is 3-12 h, preferably 4-8 h.

[0031] The present invention provides a single-atom carbon-based catalyst, which includes a honeycomb-shaped 3D porous carbon support and an active component supported on the support, and the active component contains a transition metal atom-nitrogen co-doped carbon-based material; no characteristic peak of transition metal oxide exists in the XRD spectrum of the catalyst; in the Raman spectrum of the catalyst I D / I G The value is not greater than 1.3, where I D is the peak intensity at a Raman shift value of 1350 cm -1 and I G is the peak intensity at a Raman shift value of 1600 cm -1 .

[0032] No characteristic peak of transition metal oxide exists in the XRD spectrum of the single-atom carbon-based catalyst of the present invention, and in the Raman spectrum I D / I G The value is not greater than 1.3, and the catalyst has excellent catalytic activity.

[0033] According to a preferred embodiment of the present invention, in the Raman spectrum of the catalyst I D / I G The value is 1.1-1.3.

[0034] According to a preferred embodiment of the present invention, based on the total mass of the catalyst, the content of the transition metal is not less than 2.5 wt%, preferably 2.8-3.5 wt%.

[0035] According to a preferred embodiment of the present invention, the proportion of pores with a pore diameter of 80 - 100 nm in the catalyst is not less than 80%, and the proportion of pores with a pore diameter of 10 - 50 nm is greater than 0 and less than 20%.

[0036] According to a preferred embodiment of the present invention, the specific surface area of the catalyst is 500 - 600 m 2 g -1 。

[0037] In the present invention, the preparation method of the catalyst includes: carbonizing the precursor material described in the present invention under an inert atmosphere, and optionally cooling.

[0038] The preparation method of the catalyst of the present invention can effectively prevent the agglomeration of metals during the preparation process and improve the loading amount of single - atom metals in the catalyst.

[0039] According to a preferred embodiment of the present invention, the conditions for carbonization include: the heating rate is 5 - 10 °C min -1 ; and / or the carbonization temperature is 800 - 1100 °C, and / or the carbonization time is 1 - 3 h.

[0040] The present invention provides an application of the described catalyst as an oxygen reduction catalyst in a proton exchange membrane fuel cell.

[0041] When the catalyst of the present invention is used in a proton exchange membrane fuel cell, the ORR catalytic efficiency and high - voltage stability are significantly improved. Specifically, when the transition metal is Fe, the ORR half - wave potential of the catalyst is as high as 0.827 V in 0.1 M HClO4 electrolyte, and its maximum power density in PEMFCs reaches 1.04 W cm 2 。In addition, in PEMFCs under H2 - air conditions, after a 100 - hour membrane - electrode life test at a high voltage of 0.75 V, the current density can still maintain 75% of the original. Distributing the active - center atoms uniformly at the atomic level at the three - phase reaction interface truly realizes the atomic economy of the catalyst at the device level, opening up new ideas for the assembly and application of high - performance fuel - cell devices.

[0042] The present invention will be described in detail below through examples.

[0043] Example 1 Preparation of honeycomb - like three - dimensional porous carbon (PC) 1 g of mesophase pitch was dispersed in 20 mL of ethanol / water (volume ratio 1), and then a colloidal silica suspension containing 10 g of silica was dropped into the above solution. The mixture was stirred at room temperature (20 °C) for 2 hours. Subsequently, the solvent was removed by heating at 80 °C to obtain a dried SiO2 / MP composite material, which was then carbonized in a nitrogen atmosphere at 1000 °C for 2 hours. The solid product was reacted in a 3 mol NaOH solution for 24 hours to remove the SiO2 template to form nanopores, and then washed with water until neutral and dried in vacuo to obtain the final honeycomb-like 3D porous carbon (PC).

[0044] The results of nitrogen adsorption-desorption tests, i.e., the N2 adsorption-desorption isotherm, are as shown in Figure 2 (a), and the corresponding pore size distribution curve is as shown in Figure 2 (b).

[0045] Example 2 1. Preparation of Fe-COP 0.6 g of 4-cyanobenzene was dissolved in 6 mL of DMF and stirred to obtain solution A. 0.55 g of FeCl3 was dissolved in 54 mL of ethylene glycol and dissolved under ultrasonic treatment for 3 minutes to form solution B. Then solution B was poured into A, and 1.2 mL of 1,8-diazabicyclo(5,4,0)undec-7-ene was added while stirring. The above solution was reacted in a microwave reactor with a heating power of 300 W at 180 °C for 30 minutes. Subsequently, dilute hydrochloric acid was added and left for 3 hours to obtain a green precipitate, which was centrifuged, washed 3 times with ethanol, and freeze-dried.

[0046] The sample was dissolved in DMF, and the Fourier transform infrared spectrum (FTIR) obtained by testing is as shown in Figure 1 (a), with characteristic peaks at 1705 cm -1 , 1317 cm -1 , 714 cm -1 and 2230 cm -1 .

[0047] 2. Preparation of single-atom catalyst 20 mg of the porous carbon prepared in Example 1 was dispersed in 30 mL of DMF to obtain a dispersion. 10 mg of the prepared Fe-COP was ultrasonically dissolved in 30 mL of DMF, added to the above dispersion, and reacted at 60 °C for 6 hours. After filtration, it was dried in vacuo to obtain the Fe-COP@PC composite material. 20 mg of the Fe-COP@PC composite material was placed in a porcelain boat and heated to 1000 °C at a rate of 5 °C min -1 in a nitrogen atmosphere and heated for 2 hours, and then naturally cooled to obtain the single-atom catalyst product - COP@Fe SA -PC.

[0048] The thermogravimetric curve is shown in Figure 1 (b), indicating that the material has been completely decomposed after 800 °C; the XRD pattern was obtained by sampling and testing, as shown in Figure 1 (c), in which there are no other impurity peaks except the carbon peak, and there is no characteristic peak of Fe2O3; the Raman spectrum was obtained by sampling and testing, as shown in Figure 1 (d), and the measured peak intensity ratio of the D band at 1350 cm -1 and the G band at 1600 cm -1 is I D / I G 1.2, and the lower I D / I G value indicates that COP@Fe SA -PC has a stronger degree of graphitization; the SEM image was obtained by sampling and testing, as shown in Figure 4 (a), and the TEM image was obtained by testing, as shown in Figure 4 (b), preliminarily indicating that Fe in COP@Fe SA -PC exists in the form of single atoms; the elemental mapping is shown in Figure 4 (c), indicating that C, N, Fe, and O elements are uniformly distributed in PC; the high-angle annular dark-field scanning transmission electron microscopy image (HAADF-STEM) of COP@Fe SA -PC is shown in Figure 4 (d), and the corresponding electron energy loss spectrum (EELS) is shown in Figure 4 (e), further indicating that Fe in COP@Fe SA -PC is distributed in PC in the form of single atoms, and Fe atoms combine with surrounding N atoms to form FeN x groups; the energy-dispersive X-ray spectroscopy (EDS) of COP@Fe SA -PC is shown in Figure 4 (f), and the results show that the content of Fe reaches 3.05 wt%, and the ICP results further accurately confirm that the content of Fe in COP@FeSA-PC is 3.19 wt%; the N 1s high-resolution XPS spectrum was obtained by sampling and testing, as shown in Figure 5 (a), indicating that the content of pyridine nitrogen and metal nitrogen in the COP@FeSA-PC catalyst is high; the Fe K-edge X-ray absorption near-edge structure (XANES) spectrum of COP@FeSA-PC is shown in Figure 5 (b), in which Fe foil and Fe2O3 are used as references, and the absorption edge of COP@FeSA-PC is between Fe foil and Fe2O3, indicating that the valence state of Fe atoms is between Fe 0+ and Fe3+ between

[0049] The nitrogen adsorption - desorption test results of the catalyst, that is, the N2 adsorption - desorption isotherm, are as Figure 2 (a) shown, and the corresponding pore size distribution curve is as Figure 2 (b) shown. The BET specific surface area of the catalyst is not much different from that of PC before adsorption (568 vs. 532 m 2 g -1 ), while the specific surface areas of ZIF@FeNP - PC and MOF@FeNP - PC have decreased significantly. The pore size distribution results show that the pore size of the PC material we obtained is mainly (85% pore occupancy) concentrated in 80 - 100 nm; sufficient macropores are beneficial to the rapid transfer of charges, thus accelerating the ORR reaction process. In addition, compared with the ZIF@FeNP - PC and MOF@FeNP - PC catalysts, COP@FeSA - PC still retains a large amount of the porous structure of PC to a large extent, and there are also some (15% pore occupancy) mesopores at the same time. These results indicate that due to the filling of insoluble Fe - ZIF and Fe - MOF particles in PC, the specific surface area and pore volume of the obtained materials are reduced.

[0050] Example 3 Same as Example 2, except that Fe - COP is replaced by Co - COP, that is, ferric chloride is replaced by an equimolar amount of cobalt chloride. The FTIR diagram of Co - COP is similar to Figure 1 (a).

[0051] The XRD spectrum of the catalyst is similar to Figure 1 (c), in which there are no other impurity peaks except the carbon peak, and there is no characteristic peak of cobalt oxide; Raman spectroscopy is obtained by sampling, and the peak intensity ratio of the D band at 1350 cm -1 and the G band at 1600 cm -1 is I D / I G 1.2; SEM diagram is obtained by sampling, which is similar to Figure 4 (a), TEM diagram is obtained by testing, which is similar to Figure 4 (b), indicating that Co in COP@Fe SA -PC exists in the form of single atoms, and the content of Co measured by energy - dispersive X - ray spectroscopy (EDS) of the catalyst reaches 3.1 wt%.

[0052] Example 4 Same as Example 2, except that the amounts of the raw materials are changed: 20 mg of the porous carbon prepared in Example 1 was dispersed in 30 mL of DMF to obtain a dispersion, 5 mg of the prepared Fe-COP was ultrasonically dissolved in 30 mL of DMF, added to the above dispersion, reacted at 60 °C for 6 hours, filtered and then dried under vacuum. The single-atom catalyst —— COP@Fe SA -PC-0.5 was obtained. The test results are basically similar to those of the catalyst prepared in Example 2.

[0053] Example 5 Same as Example 2, except that 20 mg of the porous carbon prepared in Example 1 was dispersed in 30 mL of DMF to obtain a dispersion, 10 mg of the prepared Fe-COP was ultrasonically dissolved in 30 mL of DMF, added to the above dispersion, reacted at 70 °C for 3 hours, filtered and then dried under vacuum to obtain the Fe-COP@PC composite. 20 mg of the Fe-COP@PC composite was placed in a porcelain boat and heated to 1100 °C at a rate of 10 °C min -1 in a nitrogen atmosphere for 1 hour, and then naturally cooled to obtain the single-atom catalyst product. The test results are basically similar to those of the catalyst prepared in Example 2.

[0054] Comparative Example 1 Same as Example 2, except that Fe-COP was replaced by Fe-ZIF. Preparation of Fe-ZIF: First, 3 g of Zn(ClO4)2·6H2O was dissolved in 80 mL of methanol, 6.5 g of 2-methylimidazole and 1.76 g of iron acetylacetonate were also dissolved in 80 mL of methanol, and then the latter was poured into the former and reacted at 60 °C for 24 hours. Finally, centrifugal separation was used, and it was washed with ethanol and water respectively and dried overnight to obtain Fe-ZIF. The catalyst —— ZIF@Fe NP -PC was obtained.

[0055] The thermogravimetric diagram of the catalyst is as shown in Figure 1 (b), indicating that the material has been completely decomposed after 800 °C; the XRD pattern was obtained by sampling and testing, as shown in Figure 1 (c), and there is no characteristic peak of Fe2O3; the Raman spectrum was obtained by sampling and testing, as shown in Figure 1 (d), and the measured peak intensity ratio of the D band at 1350 cm -1 and the G band at 1600 cm -1 is I D / I G 1.34; the nitrogen adsorption-desorption test results of the catalyst, that is, the N2 adsorption-desorption isotherm, are as shown in Figure 2(a) As shown, the corresponding pore size distribution curve is as Figure 2 (b) shown.

[0056] Take the Fe-ZIF@PC composite material, and the SEM image obtained by testing is as Figure 3 (a) shown. Fe-ZIF presents a granular morphology of about 700 nm; the TEM image obtained by testing is as Figure 3 (c) shown. Metal particles appear in the TEM image, indicating that clustering occurred during the calcination process; The ICP result confirms that the Fe content in the catalyst is 1.73 wt %.

[0057] Comparative Example 2 Same as Example 2, except that Fe-COP is replaced by Fe-MOF. Preparation of Fe-MOF: Add 2.48 g of terephthalic acid and 0.55 mL of triethylamine to 80 mL of DMF, and obtain solution A after ultrasonic uniform dispersion. Dissolve 4.45 g of Zn(NO3)2·6H2O and 5.3 g of iron acetylacetonate in 40 mL of DMF, then add 2 mL of pyrrole and ultrasonically dissolve to obtain solution B. Pour solution B quickly into A and react at 120 °C for 24 hours. Centrifuge the suspension, wash it 3 times with ethanol, and dry it overnight in vacuum at 60 °C to obtain Fe-MOF. Obtain the catalyst - MOF@Fe NP -PC.

[0058] The thermogravimetric diagram of the catalyst is as Figure 1 (b) shown, indicating that the material has been completely decomposed after 800 °C; sample and test to obtain the XRD spectrum, as Figure 1 (c) shown. There is no characteristic peak of Fe2O3; sample and test to obtain the Raman spectrum, as Figure 1 (d) shown. The measured peak intensity ratio of the D band at 1350 cm -1 and the G band at 1600 cm -1 is I D / I G 1.53; the nitrogen adsorption-desorption test result, that is, the N2 adsorption-desorption isotherm, is as Figure 2 (a) shown, and the corresponding pore size distribution curve is as Figure 2 (b) shown.

[0059] Take the Fe-MOF @PC composite material, and the SEM image obtained by testing is as Figure 3 (b) shown. Fe-MOF presents a granular morphology of about 300 nm; the TEM image obtained by testing is as Figure 3 (d) shown. Metal particles appear in the TEM image, indicating that clustering occurred during the calcination process; The ICP results confirmed that the Fe content in the catalyst was 2.25 wt%.

[0060] Comparative Example 3 Same as Example 2, except that the amounts of each raw material were changed. 20 mg of the porous carbon prepared in Example 1 was dispersed in 30 mL of DMF to obtain a dispersion. 45 mg of the prepared Fe-COP was ultrasonically dissolved in 30 mL of DMF, and the above dispersion was added. The reaction was carried out at 60 °C for 6 hours, and after filtration, it was dried under vacuum.

[0061] The obtained catalyst COP@Fe SA The TEM image of -PC-2 was similar to Figure 3 (d). Metal particles appeared in the figure, and clustering occurred during the calcination process.

[0062] Example 6 The catalysts prepared in Example 2, Comparative Example 1, and Comparative Example 2 were subjected to three-electrode ORR performance tests The ORR activity of the developed catalyst was evaluated in a typical three-electrode system (using the obtained catalyst as the working electrode, a carbon rod and a saturated calomel electrode as the counter electrode and reference electrode, respectively). As Figure 6 (a) shows, in a 0.1 M HClO4 aqueous solution filled with N2, the CV curve was rectangular-like and had no characteristic peaks. As Figure 6 (b) shows, an obvious reduction peak appeared in the O2-saturated electrolyte solution. It should be noted that the reduction peak position of COP@FeSA-PC was higher than that of ZIF@FeNP-PC and MOF@FeNP-PC, which might be due to the larger number of Fe-N active sites in the former.

[0063] As Figure 7 (a) and Figure 7 (b) show, COP@FeSA-PC exhibited the best ORR activity. Among the studied catalysts, the kinetic current density was as high as 79 mA cm -2 , the onset potential was 0.95 V, and the half-wave potential was 0.83 V, showing the highest electrochemical performance. And the catalytic activities of these catalysts were in the order of COP@FeSA-PC > ZIF@FeNP-PC > MOF@FeNP-PC.

[0064] The Tafel slopes of different catalysts were as Figure 7 (c) shows, among which the Tafel slope of COP@FeSA-PC was lower, being 60 mV dec -1 , indicating that the ORR mechanism was controlled by the migration of adsorbed oxygen-containing species (O*, OH*, OOH*).

[0065] AsFigure 7 As shown in (d), the H2O2 yield remains below 10%, and the number of electron transfers is between 3.9 and 4.0, indicating that the catalytic process on the COP@FeSA-PC electrode is an efficient four-electron ORR process.

[0066] In addition, we also studied the ORR performance adsorbed by the catalysts of Example 4 and Comparative Example 3. As Figure 7 shown in (e), the results show that with the increase in the content of Fe-COP, the electrochemical activity is significantly improved. When the content of Fe-COP increases to the presence of metal clusters, the electrocatalytic performance significantly decreases.

[0067] Example 7 Fuel cell performance test Figure 8 (a) is the reaction schematic diagram of PEMFC; The H2-O2 PEMFC with the prepared material as the cathode catalyst. Membrane: Nafion 211, cathode catalyst loading: 3 mg cm -2 , anode: 0.2 mg Pt cm -2 , H2 / O2: 0.4 / 0.8 L min -1 , back pressure: 1 bar, electrode area 5 cm 2 , temperature: 80 °C. The results are as Figure 8 shown in (b). At 0.6 V, the current density of the COP@FeSA-PC catalyst is 1.1 A cm- 2 , significantly better than that of ZIF@FeNP-PC (0.9 A cm -2 ) and MOF@FeNP-PC catalyst (0.88 A cm -2 ). It is worth noting that in the entire mass transfer region (<0.60 V), the current density of COP@FeSA-PC is significantly greater than that of ZIF@FeNP-PC and MOF@FeNP-PC, which is due to the large BET specific surface area and higher porosity. In addition, the maximum power density (P max ) of the PEMFC containing COP@FeSA-PC reaches 1.04 W cm -2 , significantly better than that containing ZIF@FeNP-PC (0.817 W cm -2 ) and MOF@FeNP-PC (0.636 W cm -2 ).

[0068] The advantages of the COP@FeSA-PC catalyst were further evaluated by electrochemical impedance spectroscopy (EIS). As Figure 8 shown in (c), it is 1A cm -2Nyquist plots at current density. It is worth noting that, compared with ZIF@FeNP-PC and MOF@FeNP-PC catalysts, the charge transfer resistance of the COP@FeSA-PC cathode is much smaller. The excellent device performance is due to the large number of Fe-N active sites and the rich porous structure, which promote the charge transfer and diffusion of O2 to the active sites, contributing to efficient cathode ORR activity and excellent fuel cell performance.

[0069] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A single-atom carbon-based catalyst precursor material, characterized in that: The general formula of the precursor material is transition metal-COP@PC, wherein PC is a honeycomb 3D porous carbon, and the FTIR spectrum of transition metal-COP contains 1705±0.5cm -1 、1317±0.5cm -1 、714±0.5cm -1 and 2230±0.5cm -1 The mass ratio of transition metal-COP to honeycomb 3D porous carbon in the catalyst is 1:0.5-2.

2. The precursor material according to claim 1, wherein The mass ratio of transition metal-COP to honeycomb 3D porous carbon in the catalyst is 1:1-2; and / or Based on the total mass of the precursor material, the content of honeycomb 3D porous carbon is 40-80wt%; and / or the content of transition metal-COP is 20-60wt%; and / or The transition metal is at least one selected from Group VIII metals, Group IB metals, and Group VIIB metals, more preferably at least one selected from iron, cobalt, copper, nickel, and manganese, and more preferably iron.

3. The precursor material according to claim 1 or 2, wherein The honeycomb 3D porous carbon has a pore size of 80-100 nm and a pore size of 10-50 nm, accounting for no less than 80% and less than 20%; and / or The specific surface area of ​​the honeycomb 3D porous carbon is 500-600 m 2 g -1 .

4. The method for preparing a precursor material according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: (1) preparing a dispersion of honeycomb 3D porous carbon; (2) adding the honeycomb 3D porous carbon dispersion into the transition metal-COP solution, mixing, filtering and vacuum drying; the mass ratio of the honeycomb 3D porous carbon to Fe-COP is 0.5-2:1, preferably 1-2:

1.

5. The method for preparing a precursor material according to claim 4, wherein: The mixing conditions include: The mixing temperature is 50-80°C, preferably 60-70°C, and / or the mixing time is 3-12h, preferably 4-8h.

6. A single-atom carbon-based catalyst, characterized in that: The catalyst comprises a honeycomb 3D porous carbon carrier and an active component supported on the carrier, wherein the active component comprises a transition metal atom-nitrogen co-doped carbon-based material; There is no characteristic peak of transition metal oxide in the XRD spectrum of the catalyst; The Raman spectrum of the catalyst I D / I G The value is not greater than 1.3, where I D The Raman shift value is 1350 cm -1 The peak intensity of I G The Raman shift value is 1600 cm -1 The peak intensity.

7. The catalyst according to claim 6, wherein The Raman spectrum of the catalyst I D / I G A value of 1.1-1.3; and / or The content of transition metal is not less than 2.5wt%, preferably 2.8-3.5wt%.

8. The catalyst according to claim 6 or 7, wherein The proportion of pores with a pore size of 80-100 nm in the catalyst is not less than 80%, and the proportion of pores with a pore size of 10-50 nm is greater than 0 and less than 20%; and / or The specific surface area of ​​the catalyst is 500-600 m 2 g -1 .

9. The method for preparing the catalyst according to any one of claims 6 to 8, characterized in that: The preparation method comprises: carbonizing the precursor material according to any one of claims 1 to 3 under an inert atmosphere; Preferably, the carbonization conditions include: a heating rate of 5-10°C min -1 ; and / or the carbonization temperature is 800-1100°C, and / or the carbonization time is 1-3h.

10. Use of the catalyst according to any one of claims 6 to 8 as an oxygen reduction catalyst in a proton exchange membrane fuel cell.

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