A screening and evaluation method for a single-atom catalyst with high mass specific activity and high overall catalytic activity in a fenton-like reaction

Abstract

The present application relates to the field of nanocatalytic materials, and in particular to a screening and evaluation method for single-atom catalysts with high mass-specific activity and high overall catalytic activity in Fenton-like reactions. The screening and evaluation method provided by the present application can screen single-atom density materials with the highest mass-specific activity by developing a work function as a key descriptor; and can determine single-atom catalysts that can simultaneously achieve high mass-specific activity and high overall catalytic activity by evaluating the electronic structure and spatial structure. The present application provides a screening and evaluation method for single-atom catalysts with high mass-specific activity and high overall catalytic activity at different densities in Fenton-like reactions from the level of single atoms, solves the problem of trial-and-error synthesis and trial use of catalytic materials that rely too much on experience, and effectively accelerates the design and optimization process of single-atom catalysts.

Description

Technical Field

[0001] This invention relates to the field of nanocatalytic materials, specifically a screening and evaluation method for single-atom catalysts that possess both high specific activity and high overall catalytic activity in Fenton-like reactions. Background Technology

[0002] Fenton-like reactions are a widely used advanced oxidation process (AOP) for the degradation of organic pollutants. The core of this process involves the reaction of transition metal catalysts with oxidants such as hydrogen peroxide and persulfate to generate highly reactive oxygen species, which oxidize and destroy organic pollutants, thereby achieving environmental purification. However, traditional Fenton-like catalysts have some limitations, such as low catalyst activity, low atom utilization, non-uniformity of active sites, and secondary pollution from transition metal ions.

[0003] In recent years, single-atom catalysts (SACs) have demonstrated great potential in environmental remediation due to their unique coordination environment and maximized atom utilization. Single-atom catalysts provide uniform active sites, enabling precise control of reactions and thus improving catalytic efficiency and selectivity. However, developing high-specific-activity and high-activity single-atom catalysts for Fenton-like reactions remains a challenge. In particular, the selection of single-atom catalysts of different densities and types still heavily relies on empirical trial and error, which limits the practical application of single-atom catalysts.

[0004] Therefore, developing a screening and evaluation method for single-atom Fenton-like catalysts that possess both high specific activity and high overall catalytic activity is of great significance. This method can help scientists and engineers quickly identify single-atom catalysts with the highest specific activity and optimal catalytic activity in Fenton-like reactions, thereby accelerating the catalyst design and optimization process. Furthermore, this method can provide more effective and environmentally friendly solutions for environmental remediation, helping to reduce secondary pollution, improve the utilization rate of metal elements, and promote the development of green chemistry and sustainable technologies. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a screening and evaluation method for single-atom catalysts that possess both high specific activity and high overall catalytic activity in Fenton-like reactions. The method provided by the present invention, by developing the work function as a key descriptor of specific activity, can screen out single-atom catalysts with the highest specific activity at different single-atom densities in Fenton-like reactions. By evaluating the electronic and spatial structures of the single-atom catalyst, it can be determined whether the single-atom catalyst can simultaneously achieve high specific activity and high catalytic activity, thereby screening out single-atom catalysts that possess both high specific activity and high overall catalytic activity.

[0006] This invention provides a method for screening and evaluating single-atom catalysts that possess both high specific activity and high overall catalytic activity in Fenton-like reactions, comprising:

[0007] Step S1) Screening a first catalyst and a second catalyst from multiple supported single-atom catalysts with different single-atom densities, and performing a first evaluation and a second evaluation on each of the supported single-atom catalysts;

[0008] The first catalyst is: the single-atom catalyst with the smallest work function among all the supported single-atom catalysts;

[0009] The second catalyst is: the single-atom catalyst among the supported single-atom catalysts that has the smallest difference, with the difference being 0~0.05 nm; the difference is the interatomic distance of each of the supported single-atom catalysts and the activation site O of the oxidant used in the Fenton-like reaction. γ and O α The difference in spacing;

[0010] The first assessment is: determining the activation site O of the supported single-atom catalyst for the oxidant used in the Fenton-like reaction. γ and O α Whether the adsorption order is adjacent;

[0011] The second assessment is to determine whether the reducibility of the supported single-atom catalyst increases with the increase of its single-atom density;

[0012] Step S2) Determine whether the single-atom densities of the first catalyst and the second catalyst in step S1) are the same.

[0013] The screening and evaluation method described in this invention is a method for screening and evaluating single-atom catalysts with different single-atom densities that can possess both high specific activity and high overall catalytic activity in Fenton-like reactions.

[0014] The Fenton-like reaction described in this invention is an advanced oxidation process widely used in the degradation of organic pollutants. Its core lies in the reaction of a catalyst with an oxidant to generate highly reactive oxygen species, which oxidize and destroy organic pollutants. In some embodiments of this invention, the oxidant used in the Fenton-like reaction is selected from one or more of persulfate, perdisulfate, and hydrogen peroxide. In some embodiments of this invention, the Fenton-like reaction is a Fenton-like reaction for degrading organic pollutants in wastewater; the organic pollutants include aromatic compounds containing electron-rich groups, wherein the electron-rich groups are hydroxyl and / or amino groups, and the aromatic compounds include at least one of phenol, 2,6-dimethylphenol, and aniline.

[0015] The supported single-atom catalysts of this invention are specifically supported single-atom Fenton-like catalysts, comprising a single-atom support and single atoms supported on the single-atom support. The screening and evaluation method of this invention targets the same type of single atom and single-atom support for each of the supported single-atom catalysts, but with different single-atom densities. The single atoms of each of the supported single-atom catalysts of this invention are selected from one or more of Cu, Fe, Ni, Co, Zn, Cr, and Mn; the single-atom supports of each of the supported single-atom catalysts are selected from one or more of carbon-based materials, oxides, and sulfides, wherein the carbon-based materials include carbon nanotubes, carbon black, carbon nitride, or metal-organic frameworks (MOFs), the oxides include Fe3O4, Fe2O3, CuO, NiO, Co3O4, or Mn2O3, and the sulfides include MoS2, Cu2S, NiS, or Co2S. In some embodiments of this invention, the single-atom density of each of the supported single-atom catalysts is less than 6 wt%.

[0016] The screening and evaluation method of the present invention first performs step S1), that is, screening a first catalyst and a second catalyst respectively among multiple supported single-atom catalysts with different single-atom densities, and performing a first evaluation and a second evaluation on each of the supported single-atom catalysts.

[0017] The first catalyst of this invention is the single-atom catalyst with the smallest work function among all the supported single-atom catalysts. This invention obtains the work function of each of the supported single-atom catalysts, determines the magnitude of the work function of each supported single-atom catalyst, and screens out the single-atom catalyst with the smallest work function, which is the single-atom catalyst with the highest mass-to-specific activity. Specifically, this invention determines the magnitude of the work function of each of the supported single-atom catalysts by judging the absolute value of its work function.

[0018] The work function of each of the supported single-atom catalysts described in this invention is obtained based on their surface potential. Specifically, the surface potential of each of the supported single-atom catalysts is obtained, and the work function of each supported single-atom catalyst with different single-atom densities is calibrated and calculated using gold (Au) as a reference. In some embodiments of this invention, the surface potential is obtained using Kelvin probe force microscopy (KPFM), photoelectron emission threshold method, hot cathode emission blocking potential method, thermionic emission method, field emission method, photoelectron emission method, electron beam (or ion beam) deceleration potential method, and scanning low-energy electron probe method.

[0019] The second catalyst of this invention is a single-atom catalyst having the smallest difference among the supported single-atom catalysts, with the difference being 0~0.05 nm; the difference is the interatomic distance of each of the supported single-atom catalysts and the activation site O of the oxidant used in the Fenton-like reaction. γ and O α The difference in spacing.

[0020] The difference mentioned in this invention refers to the interatomic spacing of each of the supported single-atom catalysts and the activation site O of the oxidant used in the Fenton-like reaction. γ and O α The difference in spacing refers to the absolute value of the difference, which is essentially the interatomic spacing of each of the supported single-atom catalysts and the activation site O of the oxidant used in the Fenton-like reaction. γ and O α The proximity of the spacing between the atoms can be used to assess whether the spatial structure of each supported single-atom catalyst and the oxidant used in the Fenton-like reaction can achieve spatial synergy. When the difference is 0~0.05 nm, preferably 0, it indicates that there is sufficient proximity and the single atom can simultaneously adsorb O. γ and O α For typical oxidants used in Fenton-like reactions, O γ It is considered to be the main site for the generation of active species and the primary activation site, which is conducive to the generation of high-valence metal and oxygen active species; while O α This is a relatively stable catalyst capable of forming a complex between the oxidant and the catalyst, thereby degrading pollutants through catalyst-mediated electron transfer. Therefore, the interatomic distance of the single-atom catalyst is similar to the activation site O of the oxidant used in the Fenton-like reaction. γ and O α The closer the spacing between the atoms, the easier it is for the single atoms of the single-atom catalyst to simultaneously adsorb the active sites of the oxidant used. γ and O α That is, the easier it is for the oxidant to achieve spatial co-activation.

[0021] In some embodiments of the present invention, the interatomic spacing of each of the supported single-atom catalysts is obtained by one or more characterization methods, including spherical aberration electron microscopy spacing measurement, Raman spectroscopy, and theoretical calculation (DFT). The present invention obtains the interatomic spacing of each of the supported single-atom catalysts and the activation site O of the oxidant used in the Fenton-like reaction. γ and O αThe spacing between the two is evaluated, and the difference between them is assessed. If a supported single-atom catalyst with the smallest difference size (0~0.05 nm) can be screened, it indicates that the screened supported single-atom catalyst can enable the oxidant to achieve spatial synergistic activation, and is expected to achieve optimal catalytic activity and mass-to-specific activity at the same time; otherwise, it indicates that the supported single-atom catalysts in the Fenton-like reaction cannot have both high mass-to-specific activity and overall catalytic activity.

[0022] The first evaluation of this invention is: determining the activation site O of the supported single-atom catalyst for the oxidant used in the Fenton-like reaction. γ and O α Whether the adsorption order is adjacent. The supported single-atom catalyst of the present invention has an activation site O for the oxidant used in the Fenton-like reaction. γ and O α The adsorption sequence means that the evaluated single-atom catalyst has no active site adsorption sequence greater than 0 for the oxidant used in the Fenton-like reaction. α And less than 0 γ or greater than 0 γ And less than 0 α Other activation sites. The adsorption order of the activation sites described in this invention can be obtained by theoretical calculation (DFT) or in-situ Raman characterization.

[0023] If the supported single-atom catalyst of the present invention has an activation site O for the oxidant used in the Fenton-like reaction... γ and O α If the order is adjacent, the supported single-atom catalyst can achieve spatial synergistic activation with the oxidant used in the Fenton-like reaction; otherwise, even if the difference is 0~0.05 nm, the oxidant cannot achieve spatial synergistic activation.

[0024] The second evaluation of this invention is to determine whether the reducibility of the supported single-atom catalyst increases with increasing single-atom density. Essentially, this second evaluation assesses the electronic structure of each of the supported single-atom catalysts. If the reducibility of the supported single-atom catalyst increases with increasing single-atom density, then in a Fenton-like system, stronger catalyst reducibility means easier activation of the oxidant; therefore, the overall catalytic activity and specific activity are expected to reach their maximum simultaneously. Otherwise, in a Fenton-like reaction, each of the supported single-atom catalysts cannot simultaneously possess high specific activity and high overall catalytic activity.

[0025] Since the greater the proportion of single atoms with higher reducing activity in the supported single-atom catalysts described in this invention, the greater the reducing power of the catalyst, this invention can obtain the relationship between the reducing power of each supported single-atom catalyst and the change in its single-atom density based on the relationship between the proportion of single atoms with relatively higher reducing activity among all single atoms in different valence states present in each supported single-atom catalyst and the change in its single-atom density.

[0026] Since the lower the valence state of the supported single-atom catalyst in the present invention, the stronger the reducing power of the single atom, the greater the proportion of single atoms with relatively lower valence states, the greater the reducing power of the catalyst. Therefore, the reducing power of each supported single-atom catalyst can be obtained from the relationship between the proportion of single atoms with relatively lower valence states among all single atoms with different valence states in each supported single-atom catalyst and the change in its single-atom density.

[0027] In some embodiments of the present invention, the reducibility of each of the supported single-atom catalysts is obtained by one or more characterization methods, namely photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS).

[0028] The screening and evaluation method of this invention involves first screening the first and second catalysts among the supported catalysts in step S1), and then performing a first evaluation and a second evaluation on each of the supported catalysts. In the screening of the first catalyst, the work function is developed as a key descriptor for specific mass activity to screen for single-atom catalysts with the highest specific mass activity at different single-atom densities. In the screening of the second catalyst and during the first evaluation, the spatial structure of each of the supported single-atom catalysts is evaluated. In the second evaluation, the electronic structure of each of the supported single-atom catalysts is evaluated. These four processes can be performed sequentially or simultaneously, without a specific order. The results of all four processes are combined to ultimately screen and evaluate whether each of the supported single-atom catalysts can simultaneously achieve both high specific mass activity and high catalytic activity.

[0029] After step S1), this invention proceeds to step S2). In step S2), it is determined whether the single-atom densities of the first catalyst and the second catalyst in step S1) are the same. Specifically, it is determined whether the single-atom densities of the first catalyst and the second catalyst selected in step S1) are the same. If they are the same, it indicates that the supported catalyst with that single-atom density possesses both high specific activity and high overall catalytic activity in the Fenton-like reaction; otherwise, it indicates that the supported catalyst cannot possess both high specific activity and high overall catalytic activity in the Fenton-like reaction.

[0030] In this invention, if the single-atom densities of the first catalyst and the second catalyst are the same, it indicates that they are the same supported single-atom catalyst with the same single-atom type, density, and single-atom support. On the one hand, having the same single-atom density as the screened first catalyst, i.e., the supported single-atom catalyst with the minimum work function, indicates that the screened second catalyst has the highest specific activity. On the other hand, if the supported single-atom catalyst meets the first and second evaluation criteria, the screened second catalyst is also a single-atom catalyst that enables the oxidant to achieve spatial co-activation. Therefore, the first catalyst, or the second catalyst, is screened and evaluated to possess both high specific activity and high overall catalytic activity in the Fenton-like reaction. If they are not the same, it indicates that the supported single-atom catalysts in the Fenton-like reaction cannot simultaneously possess high specific activity and high overall catalytic activity.

[0031] This invention provides a method for screening and evaluating single-atom catalysts with both high specific activity and high overall catalytic activity in Fenton-like reactions. The method utilizes the work function as a key descriptor to screen for single-atom density materials with the highest specific activity; and through evaluation of electronic and spatial structures, it identifies single-atom catalysts that simultaneously achieve both high specific activity and high overall catalytic activity. This invention provides a method for screening and evaluating single-atom catalysts with both high specific activity and high overall catalytic activity at different densities in Fenton-like reactions at the single-atom level, solving the problem of trial-and-error synthesis and trial use of catalytic materials that overly rely on experience, and effectively accelerating the design and optimization process of single-atom catalysts. The simultaneous optimization of specific activity and overall catalytic activity indicates that the atom utilization rate is maximized while the intrinsic activity per unit point is also maximized. This effectively saves on metal usage in the synthesis process of single-atom catalysts, and the appropriate selection of single-atom density allows reactants to react in a spatially coordinated manner, thereby increasing the rate. This has important guiding significance for the practical production and application of single-atom catalysts. Attached Figure Description

[0032] Figure 1 This is a schematic diagram illustrating the general process of screening and evaluating single-atom catalysts in a specific embodiment of the present invention.

[0033] Figure 2 XRD patterns of a series of density single-atom catalysts of Co-SAC and Fe-SACs supported on a carbon substrate (carbon nitride);

[0034] Figure 3 Aberration-corrected electron microscopy images of a series of density single-atom catalysts supported on a carbon substrate (carbon nitride) using Co-SACs and Fe-SACs.

[0035] Figure 4Fenton-like reaction kinetics of a series of density single-atom catalysts supported on a carbon substrate (carbon nitride).

[0036] Figure 5 A series of density-dependent single-atom catalysts supported on a carbon-based (carbon nitride) Co-SACs and Fe-SACs are plotted in relation to their second-order kinetic constants.

[0037] Figure 6 A series of density-to-mass ratio activities of Co-SACs and Fe-SACs density single-atom catalysts supported on a carbon substrate (carbon nitride).

[0038] Figure 7 KPFM measured surface potential maps of a series of density single-atom catalysts for carbon-based (carbon nitride) supported Co-SACs and Fe-SACs.

[0039] Figure 8 A series of density-work function relationships between Co-SACs and Fe-SACs density single-atom catalysts supported on a carbon substrate (carbon nitride);

[0040] Figure 9 The relationship between the mass ratio activity and work function of a series of density single-atom catalysts supported on a carbon-based (carbon nitride) Co-SACs and Fe-SACs substrates;

[0041] Figure 10 XPS plots of density single-atom catalysts for Co-SACs and Fe-SACs series supported on carbon substrates (carbon nitride);

[0042] Figure 11 Fitting plots showing the relationship between the density of a series of density single-atom catalysts of Co-SACs and Fe-SACs supported on a carbon substrate (carbon nitride) and the content of different metal valence states.

[0043] Figure 12 This is a diagram showing the calculated spacing of the active sites of the oxidant PMS in the Fenton-like reaction in Example 5;

[0044] Figure 13 In-situ Raman spectra of Co-3 wt.%-SACs, Fe-3 wt.%-SACs and carbon substrate. Detailed Implementation

[0045] This invention discloses a method for screening and evaluating single-atom catalysts that possess both high specific activity and high overall catalytic activity in Fenton-like reactions. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0046] The general process for screening and evaluating single-atom catalysts in the specific embodiments of this invention is as follows: Figure 1 As shown, Figure 1 This is a schematic diagram illustrating the general process of screening and evaluating single-atom catalysts in a specific embodiment of the present invention.

[0047] The present invention will be further described below with reference to the embodiments:

[0048] Example 1

[0049] Preparation of single-atom catalysts of the same density but different metals:

[0050] In this invention, the source of the single-atom catalyst is not strictly limited and can be prepared according to conventional preparation methods in the art. In the embodiments of this invention, the carbon-based single-atom catalyst was prepared according to the preparation method disclosed in the literature Chen, F. et al. Molecular Engineering toward Pyrrolic N-Rich M-N4 (M = Cr, Mn, Fe, Co, Cu) Single-Atom Sites for Enhanced Heterogeneous Fenton-Like Reaction. Adv. Funct. Mater. 31, 2007877 (2021). The single-atom densities were selected as 0, 0.5, 1.0, 3.0, 5.0, and 6.0 wt.%, respectively, and the transition metal elements were selected as Co and Fe, and the catalyst was synthesized according to the following steps:

[0051] S1. Dissolve cyanuric acid (9.6 mmol) and xanthine (2.4 mmol) in DI water (80 mL), and disperse by ultrasonication to obtain mixture 1.

[0052] S2. Melamine (1.2 mmol) was dissolved in DI water (80 mL) and dispersed by ultrasonication to obtain mixture 2.

[0053] S3. Quickly mix mixture 2 and mixture 1 to form a suspension, ultrasonically disperse for 20 min, and then magnetically stir at room temperature for 4 h to obtain mixture 3.

[0054] S4. Dissolve 0.0, 0.7, 1.3, 4.0, 6.6 and 8.0 mmol of the corresponding monatomic metal salts (nitrates of Co and Fe) in 40 mL of DI water to obtain metal salt solutions. Add the metal salt solutions to mixture 3 and stir for 1 h to obtain metal precursor solutions.

[0055] S5. After centrifuging and washing with pure water, the metal precursor solution was vacuum dried at 60℃ for 10 h. Then, the dried sample was ground in a mortar. After that, it was calcined at 550℃ for 2 h under N2 atmosphere at a rate of 5℃ / min to obtain single-atom catalysts Co-X wt.%-SACs and Fe-X wt.%-SACs (X=0, 0.5, 1.0, 3.0, 5.0, 6.0).

[0056] Characterization of the synthesized material confirmed that it was indeed a single-atom catalyst.

[0057] (1) XRD test

[0058] X-ray diffraction (XRD) tests were performed on a series of carbon-based supported density single-atom catalysts, and the results are as follows: Figure 2 As shown, Figure 2 XRD patterns of a series of density single-atom catalysts, including Co-SAC and Fe-SACs, supported on a carbon-based (carbon nitride) substrate. Figure 2 It can be seen that the doping of metal did not change the structure of the carbon substrate itself, and there were no metal oxides or metal nanoparticles present.

[0059] (2) Spherical aberration electron microscopy test

[0060] Aberration-corrected electron microscopy was performed on a series of carbon-based supported density single-atom catalysts, and the results are as follows: Figure 3 As shown, Figure 3 Aberration-corrected electron microscopy (SEM) images of a series of density single-atom catalysts based on carbon substrates (carbon nitride) and supported on Co-SACs and Fe-SACs, from... Figure 3 As can be seen directly, the metal is distributed on the material surface in the form of single atoms, indicating the successful preparation of the single-atom catalyst.

[0061] (3) Inductively Coupled Atomic Emission Spectroscopy (ICP-AES) Test

[0062] Actual measurements showed that the actual loading amounts of Co-X wt.%-SACs (X=0, 0.5, 1.0, 3.0, 5.0, 6.0) were 0.000, 0.305, 1.432, 3.437, 4.821, and 6.447 wt.%; and the actual loading amounts of Fe-X wt.%-SACs (X=0, 0.5, 1.0, 3.0, 5.0, 6.0) were 0.000, 0.304, 1.119, 3.523, 4.983, and 5.913 wt.%, which were basically consistent with expectations, indicating the successful synthesis of a series of single-atom densities.

[0063] Example 2

[0064] Evaluation of the catalytic effect of single-atom catalysts in Fenton-like reactions:

[0065] The Fenton-like reaction is mainly used to degrade pollutants by activating Fenton-like oxidants.

[0066] 1. Preparation of simulated wastewater

[0067] The organic pollutant phenol (PhOH) was dissolved in water to obtain simulated wastewater (a 0.5 mM PhOH solution, 20 mL of which was used in each experiment).

[0068] 2. Catalytic performance evaluation

[0069] Oxidant PMS (1.0 mM) was added to simulated wastewater, and the pH of the system was adjusted to 7.0 using H2SO4 / NaOH solution. Then, catalyst (based on wastewater, catalyst dosage was 1.0 g / L) was added. -1 To initiate the reaction, 1 mL of sample solution was added to a 0.2 mL (200 mM) Na₂S₂O₃ aqueous solution for quenching. After filtration through a 0.22 μm filter membrane, the concentration of PhOH in the filtrate was detected using ultra-high performance liquid chromatography (UPLC), and the reaction kinetic curve was obtained, as shown below. Figure 4 As shown, Figure 4 Fenton-like reaction kinetics of a series of density single-atom catalysts supported on a carbon substrate (carbon nitride) such as Co-SACs and Fe-SACs.

[0070] 3. Calculation of mass-to-specific activity

[0071] The second-order kinetic constants of the reaction, as we first determined, are as follows: Figure 5 As shown, Figure 5 A series of density-dependent single-atom catalysts of Co-SACs and Fe-SACs supported on a carbon-based (carbon nitride) substrate are plotted against their second-order kinetic constants. Figure 5It can be seen that, in both Co-SACs and Fe-SACs systems, a density-dependent active volcano-type curve is exhibited, reaching its maximum at 3 wt.%.

[0072] Furthermore, we calculated the conversion frequency (TOF = second-order kinetic constant / actual single-atom loading) based on the mass-to-activity ratio, such as... Figure 6 As shown, Figure 6 A series of density-to-mass ratio activity graphs for Co-SACs and Fe-SACs density single-atom catalysts supported on a carbon-based (carbon nitride) substrate; Figure 6 The results showed significant differences between the Co and Fe systems. The specific activity of the Co system decreased with increasing density, while the Fe system exhibited a volcano-shaped curve consistent with its activity, meaning that both the specific activity and catalytic activity reached their optimal values ​​at 3 wt.%. From an application perspective, Fe-3 wt.%-SACs are undoubtedly the best choice. We will further verify this by screening and evaluating them using our proposed method.

[0073] Example 3

[0074] Work function measurement and screening of the single atom density with the highest mass-to-energy reactivity:

[0075] We measured the surface potential of catalysts with different densities using KPFM, such as Figure 7 As shown, Figure 7 Surface potential maps of Co-SACs and Fe-SACs series density single-atom catalysts supported on carbon substrates (carbon nitride) were obtained by KPFM measurement; and the work function versus density relationship of the materials was further calculated after Au calibration, as shown in the figure. Figure 8 As shown, Figure 8 The graphs show the relationship between the density and work function of a series of density-dependent single-atom catalysts, Co-SACs and Fe-SACs, supported on a carbon-based (carbon nitride) substrate. The work function of Co-SACs gradually increases with increasing density, while the work function of Fe-SACs exhibits a volcano-shaped curve with increasing density, reaching a minimum at 3.0 wt.%. This means that Co-0.5 wt.%-SACs has the highest specific activity, while Fe-3.0 wt.%-SACs has the highest specific activity.

[0076] To further verify the reliability of our work function as a descriptor, we fitted the mass-to-activity ratio to the work function, as follows: Figure 9 As shown, Figure 9 The graph shows the mass-to-specific activity versus work function of a series of density single-atom catalysts supported on a carbon-based (carbon nitride) Co-SACs and Fe-SACs substrates. Figure 9It was found that good fitting effects were achieved in both Co-SACs and Fe-SACs systems, with R0... 2 The values ​​are 0.995 and 0.957, respectively. This means that we can quickly determine the single-atom catalyst with the highest mass-to-specific activity at the corresponding density by measuring the work function, even without kinetic experiments.

[0077] Example 4

[0078] Electronic structure evaluation identifies metals that simultaneously achieve optimal mass-to-specific activity and catalytic activity:

[0079] As density increases, the metal on the catalyst surface causes charge redistribution, and different metal elements may result in different final metal valence states. We used XPS to evaluate catalysts with different densities and different metal elements in order to determine suitable metal elements.

[0080] like Figure 10 and Figure 11 As shown, Figure 10 XPS plots of density single-atom catalysts for carbon-based (carbon nitride) supported Co-SACs and Fe-SACs series. Figure 11 The figure shows the relationship between the density of a series of density-dependent single-atom catalysts (Co-SACs and Fe-SACs) supported on a carbon-based (carbon nitride) substrate and the content of different metal valence states. It can be seen that the charge redistribution effect caused by increasing density is different in Co-SACs and Fe-SACs; the proportion of Co(II) decreases with increasing density, while the proportion of Fe(II) increases with increasing density. We know that in Fenton-like systems, the catalyst has stronger reducing power, meaning it is easier to activate the oxidant, and the corresponding catalytic activity and specific mass activity are expected to reach their maximum simultaneously. This indicates that, compared to Co, Fe is more likely to achieve optimal specific mass activity and catalytic activity simultaneously, consistent with experimental phenomena (i.e., compared to Co). Figures 4-6 (As shown).

[0081] Example 5

[0082] Spatial structure evaluation identifies metals that can simultaneously achieve optimal specific activity and catalytic activity:

[0083] We first statistically analyzed the interatomic spacing within the field of view of a spherical aberration electron microscope. For densities of 0.5, 3.0, and 6.0 wt.%, we selected 20, 30, and 40 sets of spacing values, respectively, and found that they generally exhibited a normal distribution trend. Further calculation of the average spacing revealed that the spacings corresponding to Co-(0.5, 3.0, 6.0 wt.%)-SACs were 0.474 nm, 0.327 nm, and 0.279 nm, respectively (from...). Figure 3As can be seen from a), the spacings corresponding to Fe-(0.5, 3.0, 6.0 wt.%)-SACs are 0.486 nm, 0.328 nm, and 0.281 nm (from a). Figure 3 (As can be seen from b). The spacing values ​​of the two single-atom materials are very consistent, indicating that the materials are synthesized very uniformly.

[0084] For typical Fenton-like oxidants PMS, O γ It is considered to be the main site for the generation of active species and the primary activation site, which is conducive to the generation of high-valence metal and oxygen active species; while O α These are relatively stable and can form PMS*, thereby degrading pollutants through catalyst-mediated electron transfer. For example... Figure 12 As shown, Figure 12 The diagram shows the calculated spacing of the active sites of the oxidant PMS in the Fenton-like reaction in Example 5. It can be seen that the Oγ-Oα spacing is exactly the same as the spacing of 3 wt.% Co-SACs and Fe-SACs. This means that PMS can, at this density, simultaneously adsorb O through spatial coordination (simultaneous adsorption of O). γ -O α The activation of PMS is achieved through a method that improves the activation efficiency of PMS, thereby potentially achieving both optimal mass-to-specific activity and catalytic activity.

[0085] Although the spacing is consistent, not all metals can simultaneously adsorb O. γ -O α Through theoretical calculations, we found that the PMS adsorption site order of Co is O γ >O β >O α The PMS adsorption site order for Fe is O. γ >O α >O β This means that spatial synergy can be formed to activate PMS to degrade pollutants, while Co cannot.

[0086] Raman's tests further confirmed the above analysis, such as Figure 13 As shown, Figure 13 In-situ Raman spectra of Co-3 wt.%-SACs, Fe-3 wt.%-SACs, and a carbon substrate. Figure 13 c indicates that the carbon substrate cannot activate PMS; only the signal of Co(IV)=O can be observed. Figure 13 a), this is the product of PMS after Oγ activation; while in Fe-3 wt.%-SACs, signals of PMS* and Fe(IV)=O can be observed simultaneously ( Figure 13 b), This is PMS after O γ With O α Key evidence for synergistic activation. Figure 3 and Figures 12-13 The test results show that Fe, which can achieve spatial synergistic activation of PMS, is more likely to achieve both optimal mass ratio activity and catalytic activity compared to Co, which is consistent with experimental observations (i.e., compared to Co). Figures 4-6 (As shown).

[0087] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for screening and evaluating single-atom catalysts possessing both high specific activity and high overall catalytic activity in Fenton-like reactions, characterized in that, include: Step S1) Screening a first catalyst and a second catalyst from multiple supported single-atom catalysts with different single-atom densities, and performing a first evaluation and a second evaluation on each of the supported single-atom catalysts; the first catalyst and the second catalyst have the same type of single atom. The first catalyst is: the single-atom catalyst with the smallest work function among all the supported single-atom catalysts; The second catalyst is: the single-atom catalyst among the supported single-atom catalysts that has the smallest difference, with the difference being 0~0.05 nm; the difference is the interatomic distance of each of the supported single-atom catalysts and the activation site O of the oxidant used in the Fenton-like reaction. γ and O α The difference in spacing; The first assessment is: determining the activation site O of the supported single-atom catalyst for the oxidant used in the Fenton-like reaction. γ and O α Whether the adsorption order is adjacent; The second assessment is to determine whether the reducibility of the supported single-atom catalyst increases with the increase of its single-atom density; Step S2) Determine whether the single-atom densities of the first catalyst and the second catalyst in step S1) are the same; If the judgment results of the first evaluation and the second evaluation in step S1) are both yes, and the single atom density of the first catalyst and the second catalyst is the same in step S2), then it is determined that the first catalyst or the second catalyst has both high specific activity and high overall catalytic activity in the Fenton-like reaction.

2. The screening and evaluation method according to claim 1, characterized in that, The oxidant used in the Fenton-like reaction is selected from one or more of persulfate, perdisulfate and hydrogen peroxide.

3. The screening and evaluation method according to claim 1, characterized in that, The Fenton-like reaction is a Fenton-like reaction that degrades organic pollutants in wastewater; The organic pollutants include aromatic compounds containing electron-rich groups.

4. The screening and evaluation method according to claim 1, characterized in that, The single-atom density of each of the supported single-atom catalysts is less than 6 wt%.

5. The screening and evaluation method according to claim 1, characterized in that, The single atoms of each of the supported single-atom catalysts are selected from one or more of Cu, Fe, Ni, Co, Zn, Cr and Mn; The single-atom support for each of the supported single-atom catalysts is selected from one or more of carbon-based materials, oxides, and sulfides.

6. The screening and evaluation method according to claim 1, characterized in that, In step S1), the work function of each supported single-atom catalyst is obtained based on its surface potential.

7. The screening and evaluation method according to claim 1, characterized in that, In step S1), the second evaluation specifically involves determining whether the proportion of single atoms with relatively higher reduction activity among all single atoms of different valence states present in the supported single-atom catalyst increases with the increase of its single-atom density.

8. The screening and evaluation method according to claim 1, characterized in that, In step S1), the second evaluation specifically involves determining whether the proportion of single atoms with relatively lower valence states among all the single atoms in the supported single-atom catalyst increases with the increase of its single-atom density.

9. The screening and evaluation method according to claim 1, characterized in that, In step S1), the reducibility of each of the supported single-atom catalysts is obtained by one or more characterization methods, namely photoelectron spectroscopy and X-ray absorption spectroscopy.

10. The screening and evaluation method according to claim 1, characterized in that, In step S1), the interatomic spacing of each of the supported single-atom catalysts is obtained by one or more characterization methods, including spherical aberration electron microscopy spacing measurement, Raman spectroscopy, and theoretical calculation.

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