Preparation method of S-doped Fe single-atom ORR catalyst

Abstract

The present invention relates to a preparation method of an S-doped Fe single-atom ORR catalyst, belonging to the technical field of electrocatalysis. The present invention dissolves AlCl3·6H2O and 2-aminoterephthalic acid in N,N-dimethylformamide, reacts at a temperature of 190-210°C for 46-50h to obtain NH2-MIL-53(Al); under a nitrogen atmosphere, the NH2-MIL-53(Al) is uniformly heated to 790-810°C and kept warm for 2-2.5h to obtain a reactant; the reactant is added to a hydrochloric acid solution, stirred at a constant temperature of 70-80°C for 23-25h, solid-liquid separation is performed, and the solid is washed and dried in sequence to obtain N-HPC; N-HPC, Glucose and thiourea are added to deionized water to produce an N-HPC mixed solution. The N-HPC mixed solution is reacted at 170-180°C for 23-25°C, followed by solid-liquid separation, drying of the solid, and constant heating to 790-810°C in a nitrogen atmosphere for 1-1.5 hours to produce S,N-HPC. A dispersion of iron phthalocyanine is then added dropwise to the S,N-HPC solution with stirring for 2-2.5 hours. The solution is then separated from the solid and liquid, dried, and constant heating to 890-910°C in a nitrogen atmosphere for 1-1.5 hours to produce Fe@S,N-HPC. The co-coordination of N and S in Fe@S,N-HPC effectively adjusts the electronic structure of Fe.

Description

Technical Field

[0001] The invention relates to a preparation method of an S-doped Fe single-atom ORR catalyst, belonging to the technical field of electrocatalysis. Background Art

[0002] The combustion of fossil fuels inevitably produces greenhouse gases such as carbon dioxide and harmful gases such as sulfur dioxide, causing a severe greenhouse effect and environmental pollution, posing a serious threat to the ecological environment. To increase the proportion of non-fossil energy consumption, improve energy efficiency, and reduce carbon dioxide emissions, it is imperative to promote the application of new energy in production and daily life. Fuel cells are one of the most promising areas of application in the new energy industry.

[0003] Fuel cells can use clean energy such as hydrogen as fuel to achieve the conversion of chemical energy into electrical energy. They have the advantages of low environmental pollution, good fuel diversity, high power supply reliability, low operating noise, and flexible device size.

[0004] A complete fuel cell device primarily consists of an anode, an electrolyte membrane, and a cathode. Hydrogen and oxygen are introduced into the anode and cathode of the device, respectively. Hydrogen undergoes a hydrogen oxidation reaction (HOR) at the anode, losing electrons. These electrons then move from an external circuit to the cathode in the form of an electric current, causing the oxygen at the cathode to undergo an oxygen reduction reaction (ORR), thereby supplying power to external devices. During this process, the ORR reaction rate at the battery's cathode is much lower than the HOR reaction rate at the anode, becoming the primary bottleneck limiting fuel cell efficiency and hindering their practical application in production and everyday life. Therefore, accelerating the ORR reaction rate has become a key focus of research and attention in the pursuit of fuel cell practical applications.

[0005] Platinum group metals (PGM), especially Pt, have the most suitable oxygen binding energy ΔE0 among all kinds of metal elements due to their unique electronic structure. They show excellent activity and corrosion resistance in the ORR reaction, and have thus become the most widely used ORR catalyst system. On the other hand, the reserves of platinum are scarce and the price is high, which makes it difficult to support the demand for ORR catalysts for large-scale applications of fuel cells, limiting the large-scale practical application of PGM catalysts. There are two mainstream solutions to the above problems: 1. Develop high-performance non-precious metal catalysts to achieve inferior substitution of PGM catalysts; 2. Improve the catalytic activity and utilization rate of PGM to reduce the use and consumption of PGM.

[0006] Single-atom catalysts (SACs) refer to catalysts dispersed on a support in the form of isolated atomic sites, emphasizing the isolation of single atoms on the support. Compared with bulky and nanoparticle (NPs) catalysts, single-atom catalysts have the advantages of large surface energy, high specific activity, stronger metal-support interaction, low cost, and maximized atomic utilization. Among them, single-atom catalysts with MNC (M = Fe, Ni, Co and other metal elements) structure usually have better catalytic performance. However, at present, the activity of single-atom catalysts is still not ideal. Under actual working conditions, especially in acidic electrolytes, the catalyst activity and durability are poor, which hinders its further application. Summary of the Invention

[0007] In response to the problems of low activity and poor activity and durability of single-atom catalysts in acidic electrolytes in the existing technology, the present invention proposes a method for preparing a S-doped Fe single-atom ORR catalyst, namely, based on a hierarchical porous carbon material derived from NH2-MIL-53(Al), it is doped with S elements and loaded with Fe single atoms. By regulating the electronic structure of the Fe site and fully exposing its active sites, the catalytic activity of the catalyst is greatly improved.

[0008] A method for preparing a S-doped Fe single-atom ORR catalyst, the specific steps are as follows:

[0009] (1) AlCl3·6H2O and 2-aminoterephthalic acid are dissolved in N,N-dimethylformamide to obtain a mixed solution, and the mixed solution is reacted at a temperature of 190-210°C for 46-50 hours to obtain NH2-MIL-53(Al);

[0010] (2) Under a nitrogen atmosphere, NH2-MIL-53(Al) was heated at a constant rate of 790-810°C and kept at this temperature for 2-2.5 hours to obtain a reactant; the reactant was added to a hydrochloric acid solution, stirred at a constant temperature of 70-80°C for 23-25 ​​hours, and the solid-liquid separation was performed. The solid was washed and dried in turn to obtain N-HPC;

[0011] (3) N-HPC, glucose and thiourea are added to deionized water and stirred to dissolve to obtain an N-HPC mixed solution. The N-HPC mixed solution is reacted at a temperature of 170-180°C for 23-25°C, solid-liquid separation is performed, the solid is dried, and then placed in a nitrogen atmosphere and uniformly heated to a temperature of 790-810°C and annealed for 1-1.5 hours to obtain S,N-HPC;

[0012] (4) Add iron phthalocyanine to methanol and ultrasonically disperse to obtain solution A, add S,N-HPC to n-hexane and ultrasonically disperse to obtain solution B, add solution A dropwise to solution B and stir to react for 2 to 2.5 hours, separate the solid and liquid, dry the solid, and then place it in a nitrogen atmosphere and uniformly heat it to 890 to 910°C and anneal it for 1 to 1.5 hours to obtain Fe@S,N-HPC.

[0013] In the step (1), the mass ratio of AlCl3·6H2O to 2-aminoterephthalic acid is 0.90-0.92:1.

[0014] The concentration of the hydrochloric acid solution in step (2) is 3 to 3.5 mol / L.

[0015] In the step (3), the mass ratio of N-HPC, glucose and thiourea is 0.16-0.18:0.98-1.02:1.

[0016] In the step (4), the concentration of iron phthalocyanine in solution A is 48-50 g / L, the concentration of S,N-HPC in solution B is 24-26 g / L, and the mass ratio of iron phthalocyanine to S,N-HPC is 1.85-2.08:1.

[0017] Fe@S,N-HPC was loaded on a glassy carbon electrode to prepare a Fe@S,N-HPC / glassy carbon electrode. The ORR performance of Fe@S / N-HPC was tested in 1 M KOH solution using the Fe@S,N-HPC / glassy carbon electrode as the working electrode, the mercury oxide electrode as the reference electrode, and the platinum sheet as the counter electrode.

[0018] The beneficial effects of the present invention are:

[0019] (1) The present invention uses the N element and the doped S element in the NH2-MIL-53(Al) derivative to jointly regulate the electronic structure of the loaded Fe single atom, thereby improving its intrinsic activity;

[0020] (2) The multi-level pore structure of the material of the present invention exposes the Fe site components, thereby greatly improving the catalytic activity of the catalyst. The half-wave potential measured in 1M KOH solution is consistent with J k @0.85V are 0.88V and 13.93mA cm -2 ; It is significantly better than the 0.85V and 4.33mA cm of Fe@N-HPC and Fe@XC-72 prepared by using N-HPC without S element and commercial carbon support XC-72. -2 and 0.79 V and 1.66 mA cm for Fe@XC-72. -2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 HAADF-STEM image and STEM-EDS element distribution map of S / N-HPC in Example 1;

[0022] Figure 2 HAADF-STEM image (a) of Fe@S / N-HPC in Example 1, STEM-EDS distribution diagrams of N, S, and Fe elements (bd), and atomic resolution HAADF-STEM image (e);

[0023] Figure 3 K-edge XANES spectra (a) and FT-EXAFS spectra (b) of Fe@N-HPC, Fe@S / N-HPC and standard samples in Example 1;

[0024] Figure 4 LSV curves (a) of Fe@N-HPC, Fe@S / N-HPC and Fe@XC-72 in Example 1, E 1 / 2 Comparison with Jk@0.85V in Figure (b). DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0026] Example 1: A method for preparing a S-doped Fe single-atom ORR catalyst, the specific steps are as follows:

[0027] (1) AlCl3·6H2O and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide to obtain a mixed solution, and the mixed solution was reacted at 200°C for 48 hours to obtain NH2-MIL-53(Al); wherein the mass ratio of AlCl3·6H2O to 2-aminoterephthalic acid was 0.90:1; and the concentration of AlCl3·6H2O in the mixed solution was 0.026 g / L;

[0028] (2) Under a nitrogen atmosphere, NH2-MIL-53(Al) was heated to 800°C at a rate of 5°C / min and kept at this temperature for 2 h to obtain a reactant; the reactant was added to a 3.5 mol / L hydrochloric acid solution, stirred at 80°C for 24 h, and the solid-liquid separation was performed. The solid was washed and dried to obtain N-HPC;

[0029] (3) N-HPC, glucose and thiourea were added to deionized water and stirred to dissolve to obtain an N-HPC mixed solution. The N-HPC mixed solution was reacted at a temperature of 180 ° C and 24 ° C, solid-liquid separation was performed, the solid was dried, and then placed in a nitrogen atmosphere and uniformly heated to a temperature of 800 ° C and kept annealed for 1 h to obtain S,N-HPC; wherein the mass ratio of N-HPC, glucose and thiourea was 0.16:1:1, and the concentration of N-HPC in the N-HPC mixed solution was 24 g / L;

[0030] (4) Adding iron phthalocyanine to methanol and ultrasonically dispersing it to obtain solution A, adding S, N-HPC to n-hexane and ultrasonically dispersing it to obtain solution B, adding solution A dropwise to solution B and stirring to react for 2 hours, separating the solid and the liquid, drying the solid, and then placing it in a nitrogen atmosphere and uniformly heating it at a rate of 5°C / min to 900°C and annealing it for 1 hour to obtain Fe@S, N-HPC; wherein the concentration of iron phthalocyanine in solution A is 49 g / L, the concentration of S, N-HPC in solution B is 25 g / L, and the mass ratio of iron phthalocyanine to S, N-HPC is 1.96:1;

[0031] Fe@S,N-HPC was loaded onto a glassy carbon electrode to prepare a Fe@S,N-HPC / glassy carbon electrode. The Fe@S,N-HPC / glassy carbon electrode was used as the working electrode, a mercury oxide electrode was used as the reference electrode, and a platinum sheet was used as the counter electrode. The ORR performance of Fe@S / N-HPC was tested in a 1 M KOH solution.

[0032] The HAADF-STEM image and STEM-EDS element distribution map of N-HPC in this example are shown in Figure 1 ,from Figure 1 It can be seen that N-HPC has a uniform one-dimensional rod-like morphology and forms a rich mesoporous and microporous structure. The nitrogen element is evenly dispersed in N-HPC and can effectively anchor atomic sites. Therefore, N-HPC can be further doped and regulated as an excellent multi-level porous carbon material and applied in catalytic reactions.

[0033] The HAADF-STEM image of Fe@S / N-HPC in this example is shown in Figure 2 (a), STEM-EDS distribution diagram of N, S, and Fe elements is shown in Figure 2 (bd) and atomic resolution HAADF-STEM images are shown in Figure 2 (e), from Figure 2 From (a~d), we can see that the doped S element and the loaded Fe element are evenly distributed in the catalyst. Figure 2 (e) It can be seen that Fe is dispersed on the support in the form of single atoms;

[0034] The K-edge XANES spectra of Fe@N-HPC, Fe@S / N-HPC and standard samples in this example are shown in Figure 2. Figure 3 (a) and FT-EXAFS spectrum Figure 3 (b) It can be found that the pre-edge absorption peaks of Fe@N-HPC and Fe@S / N-HPC are between FePc and ferric oxide, which indicates that the valence state of Fe element in Fe@N-HPC and Fe@S / N-HPC is between +2 and +3; at the same time, the pre-edge absorption peak of Fe@S / N-HPC is located on the right side of Fe@N-HPC, indicating that the doping of S element changes the coordination environment of Fe, causing its valence state to increase; at the same time, there is only There is no Fe-N peak at The Fe-O peak at The Fe-Fe peak at 100 nm indicates that the Fe in the sample exists in the form of single atoms and forms a coordination with the N atom.

[0035] The LSV curves of Fe@N-HPC, Fe@S / N-HPC and Fe@XC-72 in this example are shown in Figure 4 (a), E 1 / 2 See the comparison chart with Jk@0.85V Figure 4 (b) Among the three groups of samples, Fe@S / N-HPC has the largest onset potential and half-wave potential. The half-wave potential and Jk@0.85V of Fe@S / N-HPC can reach 0.88V and 13.93mA cm -2 , which is higher than 0.85 V and 4.33 mA cm of Fe@N-HPC. -2 and 0.79 V and 1.66 mA cm for Fe@XC-72. -2 .

[0036] Example 2: A method for preparing a S-doped Fe single-atom ORR catalyst, the specific steps are as follows:

[0037] (1) AlCl3·6H2O and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide to obtain a mixed solution, and the mixed solution was reacted at a temperature of 190°C for 50 hours to obtain NH2-MIL-53(Al); wherein the mass ratio of AlCl3·6H2O to 2-aminoterephthalic acid was 0.92:1; and the concentration of AlCl3·6H2O in the mixed solution was 0.027 g / L;

[0038] (2) Under a nitrogen atmosphere, NH2-MIL-53(Al) was heated to 790°C at a heating rate of 5°C / min and kept warm for 2.5 hours to obtain a reactant; the reactant was added to a hydrochloric acid solution with a concentration of 3 mol / L, and the mixture was stirred at a constant temperature of 70°C for 25 hours. The solid and liquid were separated, and the solid was washed and dried in sequence to obtain N-HPC; the N-HPC in this embodiment had a uniform one-dimensional rod-like morphology and formed a rich mesoporous and microporous structure. The nitrogen element was uniformly dispersed in the N-HPC and could effectively anchor the atomic sites;

[0039] (3) N-HPC, glucose and thiourea were added to deionized water and stirred to dissolve to obtain an N-HPC mixed solution. The N-HPC mixed solution was reacted at a temperature of 175°C for 23°C, solid-liquid separation was performed, the solid was dried, and then placed in a nitrogen atmosphere and uniformly heated to a temperature of 810°C and kept annealed for 1.3 hours to obtain S,N-HPC; wherein the mass ratio of N-HPC, glucose and thiourea was 0.18:1.02:1, and the concentration of N-HPC in the N-HPC mixed solution was 27 g / L;

[0040] (4) Adding iron phthalocyanine to methanol and ultrasonically dispersing it to obtain solution A, adding S, N-HPC to n-hexane and ultrasonically dispersing it to obtain solution B, adding solution A dropwise to solution B and stirring to react for 2.5 hours, separating the solid and the liquid, drying the solid, and then placing it in a nitrogen atmosphere and uniformly heating it to 890°C at a heating rate of 5°C / min and annealing it for 1.5 hours to obtain Fe@S, N-HPC; wherein the concentration of iron phthalocyanine in solution A is 50 g / L, the concentration of S, N-HPC in solution B is 26 g / L, and the mass ratio of iron phthalocyanine to S, N-HPC is 1.92:1;

[0041] Fe@S,N-HPC was loaded onto a glassy carbon electrode to prepare a Fe@S,N-HPC / glassy carbon electrode. The Fe@S,N-HPC / glassy carbon electrode was used as the working electrode, a mercury oxide electrode was used as the reference electrode, and a platinum sheet was used as the counter electrode. The ORR performance of Fe@S / N-HPC was tested in a 1 M KOH solution.

[0042] The valence state of the Fe element in the Fe@S / N-HPC of this embodiment is between +2 and +3. The doping of the S element changes the coordination environment of Fe, causing its valence state to increase. Fe exists in the form of a single atom and forms a coordination with the N atom.

[0043] Therefore, the N element and the doped S element in the NH2-MIL-53(Al) derivative can jointly regulate the electronic structure of the loaded Fe single atom and enhance its intrinsic activity.

[0044] Example 3: A method for preparing a S-doped Fe single-atom ORR catalyst, the specific steps are as follows:

[0045] (1) AlCl3·6H2O and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide to obtain a mixed solution, and the mixed solution was reacted at a temperature of 210°C for 46 hours to obtain NH2-MIL-53(Al); wherein the mass ratio of AlCl3·6H2O to 2-aminoterephthalic acid was 0.91:1; and the concentration of AlCl3·6H2O in the mixed solution was 0.026 g / L;

[0046] (2) Under a nitrogen atmosphere, NH2-MIL-53(Al) was heated to 810°C at a heating rate of 5°C / min and kept warm for 2.3 hours to obtain a reactant; the reactant was added to a hydrochloric acid solution with a concentration of 3.2 mol / L, and the mixture was stirred at a constant temperature of 75°C for 23 hours. The solid and liquid were separated, and the solid was washed and dried in sequence to obtain N-HPC; the N-HPC in this embodiment had a uniform one-dimensional rod-like morphology and formed a rich mesoporous and microporous structure. The nitrogen element was uniformly dispersed in the N-HPC and could effectively anchor the atomic sites;

[0047] (3) N-HPC, glucose and thiourea were added to deionized water and stirred to dissolve to obtain an N-HPC mixed solution. The N-HPC mixed solution was reacted at a temperature of 170 ° C and 25 ° C, solid-liquid separation was performed, the solid was dried, and then placed in a nitrogen atmosphere and uniformly heated to a temperature of 790 ° C and kept annealed for 1.5 h to obtain S,N-HPC; wherein the mass ratio of N-HPC, glucose and thiourea was 0.17:0.99:1, and the concentration of N-HPC in the N-HPC mixed solution was 25.5 g / L;

[0048] (4) Adding iron phthalocyanine to methanol and ultrasonically dispersing it to obtain solution A, adding S, N-HPC to n-hexane and ultrasonically dispersing it to obtain solution B, adding solution A dropwise to solution B and stirring to react for 2.3 hours, separating the solid and the liquid, drying the solid, and then placing it in a nitrogen atmosphere and uniformly heating it to 910°C at a heating rate of 5°C / min and annealing it for 1.3 hours to obtain Fe@S, N-HPC; wherein the concentration of iron phthalocyanine in solution A is 48 g / L, the concentration of S, N-HPC in solution B is 24 g / L, and the mass ratio of iron phthalocyanine to S, N-HPC is 2:1;

[0049] Fe@S,N-HPC was loaded onto a glassy carbon electrode to prepare a Fe@S,N-HPC / glassy carbon electrode. The Fe@S,N-HPC / glassy carbon electrode was used as the working electrode, a mercury oxide electrode was used as the reference electrode, and a platinum sheet was used as the counter electrode. The ORR performance of Fe@S / N-HPC was tested in a 1 M KOH solution.

[0050] The valence state of the Fe element in the Fe@S / N-HPC of this embodiment is between +2 and +3. The doping of the S element changes the coordination environment of Fe, causing its valence state to increase. Fe exists in the form of a single atom and forms a coordination with the N atom.

[0051] Therefore, the N element and the doped S element in the NH2-MIL-53(Al) derivative can jointly regulate the electronic structure of the loaded Fe single atom and enhance its intrinsic activity.

[0052] The above describes the specific embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

Claims

1. A method for preparing a S-doped Fe single-atom ORR catalyst, characterized in that: The specific steps are as follows: (1) AlCl3·6H2O and 2-aminoterephthalic acid are dissolved in N,N-dimethylformamide to obtain a mixed solution, and the mixed solution is reacted at a temperature of 190-210°C for 46-50 hours to obtain NH2-MIL-53(Al); (2) Under a nitrogen atmosphere, NH2-MIL-53(Al) was heated to 790-810°C at a constant rate and kept at this temperature for 2-2.5 hours to obtain a reactant; the reactant was added to a hydrochloric acid solution, stirred at a constant temperature of 70-80°C for 23-25 ​​hours, and the solid-liquid separation was performed. The solid was washed and dried in turn to obtain N-HPC; (3) N-HPC, glucose and thiourea are added to deionized water and stirred to dissolve to obtain an N-HPC mixed solution. The N-HPC mixed solution is reacted at a temperature of 170-180°C for 23-25 ​​hours, solid-liquid separation is performed, the solid is dried, and then placed in a nitrogen atmosphere and uniformly heated to a temperature of 790-810°C and annealed for 1-1.5 hours to obtain S,N-HPC; (4) Add iron phthalocyanine to methanol and ultrasonically disperse to obtain solution A, add S,N-HPC to n-hexane and ultrasonically disperse to obtain solution B, add solution A dropwise to solution B and stir to react for 2 to 2.5 hours, separate the solid and liquid, dry the solid, and then place it in a nitrogen atmosphere and uniformly heat it to 890 to 910°C and anneal it for 1 to 1.5 hours to obtain Fe@S,N-HPC.

2. The method for preparing the S-doped Fe single-atom ORR catalyst according to claim 1, characterized in that: In step (1), the mass ratio of AlCl3·6H2O to 2-aminoterephthalic acid is 0.90-0.92:

1.

3. The method for preparing the S-doped Fe single-atom ORR catalyst according to claim 1, characterized in that: The concentration of the hydrochloric acid solution in step (2) is 3 to 3.5 mol / L.

4. The method for preparing the S-doped Fe single-atom ORR catalyst according to claim 1, characterized in that: In step (3), the mass ratio of N-HPC, glucose and thiourea is 0.16-0.18:0.98-1.02:

1.

5. The method for preparing the S-doped Fe single-atom ORR catalyst according to claim 1, characterized in that: The concentration of iron phthalocyanine in solution A of step (4) is 48-50 g / L, the concentration of S, N-HPC in solution B is 24-26 g / L, and the mass ratio of iron phthalocyanine to S, N-HPC is 1.85-2.08:1.

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