Composite coordination monatomic catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of metal catalysis, in particular to a composite coordination monatomic catalyst and a preparation method and application thereof. The catalyst comprises a carrier and a metal center, the carrier comprises auxiliary coordination atoms, and at least two auxiliary coordination atoms are coupled with the metal center to form a catalytic activity center; wherein the metal center comprises a monatomic metal center, and the auxiliary coordination atoms comprise at least two of C, N, P, S and Cr. According to the composite coordination monatomic catalyst, the dissociation energy barrier of H2O is reduced through the synergistic effect between a metal center and auxiliary coordination atoms, the dissociation and proton generation rate of H2O is increased, and the catalytic efficiency of the composite coordination monatomic catalyst in an alkaline hydrogen evolution reaction is greatly improved. According to the composite coordination monatomic catalyst, an auxiliary coordination atom is coupled with an anchoring metal center to form a catalytic activity center, so that the stability and durability of the composite coordination monatomic catalyst are improved.

Description

Technical Field

[0001] This application belongs to the field of metal catalysis technology, and in particular relates to a composite coordination single-atom catalyst, its preparation method and application. Background Technology

[0002] Hydrogen energy, as one of the lowest carbon-emission fuels, holds promise for achieving sustainable development through green water electrolysis. Recent advances in anion exchange membrane (AEM) technology have confirmed the feasibility of operating electrolyzers and fuel cells in alkaline media. However, achieving significant alkaline hydrogen evolution reaction (HER) to date requires overcoming several fundamental bottlenecks, one of which is that the kinetics of alkaline HER are 2 to 3 orders of magnitude lower than in acidic environments because alkaline HER involves the dissociation of water (Volmer step: H₂O + e⁻ → 1 / 2). +OH - It is necessary to ensure an effective supply of protons near the active site through water dissociation.

[0003] Bifunctional mechanisms, involving multiple active components, can dissociate water molecules and optimize intermediate adsorption, and have been widely used in catalyst design to achieve sustainable hydrogen energy production through water electrolysis. For example, Markovic et al. first created a novel bifunctional metal oxide-metal system (Ni(OH)2 / Pt-island structure) to promote water dissociation and... Since binding strength has been used as a descriptor to control the basic hydrogen evolution reaction ( Figure 1 In recent years, much work has focused on introducing synergistic components to enhance catalytic performance. As a representative example, the Sargent group developed an anisotropic surface doping method to prepare CrOx / Cu-Ni multisite catalysts, where CrOx and Ni species are respectively doped with... and Strong bonding accelerates the dissociation of water on the Cu surface, thereby rapidly generating H2 ( Figure 1 (a) Furthermore, Koper et al. described the reaction rate of the basic hydrogen evolution reaction as... Bond strength ( )and Bond strength ( The function of ) is used to explain the bifunctional mechanism in the basic hydrogen evolution reaction, highlighting the seesaw relationship between the water dissociation energy barrier and the intermediate adsorption energy, and making a significant contribution to guiding and designing optimal catalysts.

[0004] Although a great deal of research has been conducted to try to improve the activity of alkaline hydrogen evolution reaction, there is still room for further improvement in the activity of alkaline hydrogen evolution reaction in order to reduce the cost of commercial application of alkaline hydrogen evolution reaction and promote the application of hydrogen energy. Summary of the Invention

[0005] The purpose of this application is to provide a composite coordination single-atom catalyst, its preparation method and application, to solve the technical problems of slow kinetics and low activity of alkaline hydrogen evolution reaction in the prior art.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: In a first aspect, embodiments of this application provide a composite coordination single-atom catalyst. The composite coordination single-atom catalyst of this application includes a support and a metal center. The support includes auxiliary coordinating atoms, and at least two auxiliary coordinating atoms are coupled with the metal center to form a catalytically active center. The metal center includes a single-atom metal center, and the auxiliary coordinating atoms include at least two of C, N, P, S, and Cr.

[0007] The composite coordination single-atom catalyst of this application uses at least two of the atoms selected from C, N, P, S, and Cr as auxiliary coordinating atoms to anchor the metal center. This allows the metal center and auxiliary coordinating atoms in the catalytic active center to have a synergistic effect, which can synergistically reduce the dissociation energy barrier of H2O, increase the dissociation rate of H2O and the proton production rate, and greatly improve the catalytic efficiency of the composite coordination single-atom catalyst in the alkaline hydrogen evolution reaction. Furthermore, compared with single-atom metal catalysts, the active catalytic center of the composite coordination single-atom catalyst of this application, formed by the coupling and anchoring of the metal center with auxiliary coordinating atoms, not only improves the catalytic activity but also enhances the stability and durability of the composite coordination single-atom catalyst.

[0008] Secondly, embodiments of this application provide a method for preparing the composite coordination single-atom catalyst described above. The method for preparing the composite coordination single-atom catalyst of this application includes the following steps: The carrier material and the metal source are subjected to a first mixing process to obtain a first mixture, wherein the carrier material is doped with elements that have auxiliary coordinating atoms and the metal source contains metal elements with metal centers. The first mixture was subjected to a first heating treatment to obtain a composite coordinated single-atom catalyst.

[0009] The method for preparing the composite coordination single-atom catalyst in this application promotes the coupling of metal and dopant elements through a first heat treatment, thereby promoting the formation of catalytic active centers containing auxiliary coordinating atoms coupled with the metal center. This significantly improves the catalytic activity of the composite coordination single-atom catalyst, giving it high catalytic activity for the alkaline hydrogen evolution reaction. Furthermore, the preparation method in this application involves fewer steps, is simple to operate, and is suitable for large-scale industrial production.

[0010] Thirdly, this application also provides another method for preparing the composite coordination single-atom catalyst described above. This preparation method includes the following steps: A second mixture is obtained by mixing a metal catalyst containing a metal center metal element with a doped element source. The second mixture was subjected to a second heat treatment to obtain a composite coordination single-atom catalyst.

[0011] The preparation method provided in the third aspect of this application involves mixing a metal catalyst and a dopant source, followed by a second heating treatment. This allows the metal element in the metal catalyst to couple with the dopant element, forming catalytic active centers, thereby producing a highly active composite coordination single-atom catalyst, which significantly improves the reactivity of the alkaline hydrogen evolution reaction. Furthermore, the preparation method of this application can also modify existing catalysts to further enhance their catalytic activity, making it widely applicable and possessing enormous application potential.

[0012] Fourthly, embodiments of this application provide the application of the composite coordination single-atom catalyst described above in water electrolysis.

[0013] The composite coordination single-atom catalyst of the present application has a good catalytic effect on alkaline hydrogen evolution reaction, which can greatly reduce the dissociation energy of water and has broad application prospects in the electrolysis of water to produce clean energy. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of a catalyst based on a bifunctional mechanism of alkaline hydrogen evolution reaction, wherein, Figure 1 In the diagram, 'a' represents a schematic diagram of a bifunctional catalytic system using existing technology (where O is represented in red and H in white). Figure 1 In the diagram, b represents the activation mechanism of orbital interaction between the metal center (M) and H2O; Figure 1 c in the figure is a schematic diagram of Lewis acid-basic bifunctional atom pairs in which the coordination environment of SACs is adjusted to enhance the basic hydrogen evolution reaction in an embodiment of this application. Figure 2 This is a schematic diagram of the preparation method of the composite coordination single-atom catalyst in Example 1; Figure 3 In the figure, 'a' represents the linear sweep voltammograms of composite coordination single-atom catalysts with different P / N atomic ratios (i.e., molar ratios) in Examples 1 to 5 and the catalyst in Comparative Example 1 (where the color scale represents the current density). Figure 3In the diagram, b represents the TOF value of HER activity as a function of the P / N atomic ratio; Figure 4 In the figure, 'a' represents the polarization curves of the composite coordination single-atom catalyst in Example 7 and the catalyst in Comparative Example 3. Figure 4 In the figure, b represents the polarization curves of the composite coordination single-atom catalyst in Example 6 and the catalyst in Comparative Example 2. Figure 4 In the diagram, c represents the relative activity of the current density on the overpotential scale for the composite coordination single-atom catalysts of Examples 6-7 and Comparative Examples 2-3. Figure 5 This is a schematic diagram illustrating the structural characterization of the Ru-P atom pair in the composite coordination single-atom catalyst of Example 1; wherein, Figure 5 In the image, 'a' represents the TEM image of Ru1 / PNC. Figure 5 b in the image is an AC HAADF-STEM image of Ru1 / PNC (proving the formation of a Ru single atom, with the yellow circle highlighting a typical Ru-P pair). Figure 5 c in the figure represents the elemental distribution of Ru1 / PNC at 200 nm. Figure 5 In the EELS spectrum, d indicates the presence of P and N elements on the carbon support; Figure 5 In this context, 'e' represents the Ru K-edge XANES spectrum. Figure 5 f is k 2 Weighted Ru K-edge FT-EXAFS spectrum; Figure 5 In the figure, g is the fitting analysis curve of Ru K-edge EXAFS to Ru1 / PNC. From bottom to top, it is the Ru-N and Ru-P scattering path signals contained in the total signal (red line) superimposed on the experimental data. The calculated and tested spectra have a high degree of consistency. The inset is a schematic diagram of Ru1-N3P1 structure. Figure 5 h in Figure 5 The intensity distribution map of several selected areas in b is shown in the schematic diagram. Figure 5 In the figure, i represents a heatmap of the P 2p X-ray photoelectron spectral signal with respect to the P content. The right spectrum was extracted from a P content of ~4.5 at.%. Figure 5 j represents the solid content of P. 31 P nuclear magnetic resonance spectrum; Figure 5 In this context, k represents the PDOS analysis spectrum of the Ru1-N3P1 structure; Figure 6 SEM images of Ru1 / PNC and Ru1 / NC are shown; where, Figure 6 In the figure, a and b are SEM images of Ru1 / PNC; Figure 6 c and d in the figure are SEM images of Ru1 / NC; Figure 7 High-resolution TEM image of Ru1 / PNC sample; Figure 8 In the image, 'a' represents the TEM image of the Ru1 / NC sample. Figure 8 b in the image is a high-resolution TEM image of the Ru1 / NC sample; Figure 9 XRD patterns of Ru1 / PNC and Ru1 / NC samples; Figure 10 AC HAADF-STEM image of Ru1 / NC sample; Figure 11 This is a plot showing the elemental distribution of Ru1 / NC. Figure 12 The images show the Ru 3p XPS spectra of Ru1 / PNC and Ru1 / NC. The spectra indicate that the Ru valence state in Ru1 / PNC is lower than that in Ru1 / NC. Figure 13 Example 1: Schematic diagram of the electrocatalytic performance and behavior of the composite coordination single-atom catalyst (Ru1 / PNC) in Comparative Example 1, the catalyst in Comparative Example 2 (Pt1 / C), and the catalyst in Comparative Example 3 (Ru / C) in the alkaline hydrogen evolution reaction; whereby... Figure 13 In the figure, 'a' represents the HER polarization curve in 1 M KOH electrolyte at a rotation speed of 2400 rpm. Figure 13 In this context, 'b' represents a comparison of the HER performance indicators of the catalysts. Figure 13 In this context, 'c' represents the overpotential and Tafel slope of the HER for different SACs-based catalysts. Figure 13 In the diagram, d represents the KIE value and is used to plot the polarization curve. Figure 13 In the figure, 'e' represents the cyclic voltammograms of Ru1 / PNC, Ru1 / NC, and Ru / C in different electrolytes. Figure 13 f in the figure represents the CO dissolution curves of Ru1 / PNC, Ru1 / NC, and Ru / C in 1M KOH; Figure 13 In the figure, g represents the Bode phase diagrams of Ru1 / NC and Ru1 / PNC under different applied overpotentials in 1M KOH; Figure 14 In the image, 'a' represents a TEM image of Ru nanoparticles. Figure 14 b in the image represents a high-resolution TEM image of Ru nanoparticles. Figure 14 In the image, c represents the HAADF image of Ru nanoparticles and the corresponding elemental distribution map; Figure 15 The HER polarization curves of Ru nanoparticle catalyst in 1M KOH electrolyte are shown. Figure 16 This is a Tafel slope plot; the data comes from... Figure 13 The polarization curve of a in the figure; Figure 17In the figure, 'a' is a schematic diagram of the specific surface area test results of Ru1 / NC; Figure 17 In the diagram, b represents the specific surface area test results of Ru1 / PNC; Figure 18 In the figure, a, b, c and d are HER cyclic voltammograms of Ru1 / PNC, Ru1 / NC, Pt / C and Ru / C at different scan rates, respectively; Figure 18 In the figure, 'e' represents the change in current density (Δ) plotted on the graph. j / 2) and scan rate (20~100mV·s) -1 The relationship between the two sides determines the schematic diagram of the double-layer capacitor; Figure 19 For Ru1 / PNC and Ru1 / NC at 10 mA·cm -2 Schematic diagram of chronopotential measurement results under current density; Figure 20 A schematic diagram showing the chronopotential measurement results of Ru1 / PNC, Ru1 / NC, and Ru / C at different temperatures ranging from 25 to 65°C; Figure 21 a, b, and c in the figure represent the polarization curves of Ru1 / PNC, Ru1 / NC, and Ru / C at different temperatures, respectively. Figure 21 In the diagram, d represents the Ea data and error bars for calculating the polarization curve; Figure 22 A schematic diagram illustrating the properties and multifunctionality of Lewis pairs; Figure 22 a and Figure 22 In the diagram, b represents the charge density difference between the Ru1 / NC and Ru1 / PNC structures, respectively. Blue represents electron depletion, and yellow represents accumulation. The isosurface energy level for different samples is 0.005 e Bohr. -3 ; Figure 22 c and Figure 22 In the figure, d represents the NH3–TPD curve and CO2–TPD curve of Ru1 / PNC, Ru1 / NC, Pt / C and Ru / C, respectively, showing the different acidity and basicity among the samples; Figure 22 In the diagram, 'e' represents the results of a poisoning experiment on Ru1 / PNC by controlling the addition of probe molecules; LB: thiourea molecule; LA: boric acid molecule. Figure 22 In this context, f represents a comparison of the catalytic performance of different Lewis acid-base pairs under the same reaction conditions; Figure 23 The pyridine infrared spectra of Ru1 / PNC and Ru1 / NC show that both catalysts contain acidic sites. The characteristic absorption peak of the Lewis acid site of pyridine chemisorption is present; although in A peak of pyridine adsorbed at the Bronster acidic site was also detected, but its density was much lower than that at the Lewis acidic site (the aspect ratio was around 9); in addition, the absorption peak of Ru1 / PNC was blue-shifted compared with Ru1 / NC, indicating that Ru1 / PNC has stronger acidity. Figure 24 The polarization curves of Ru1 / PNC after interaction with different toxic molecules are shown, where LB represents thiourea molecules and LA represents boric acid molecules. Figure 25 This is a schematic diagram of the reaction pathway and durability test results in AEM; where, Figure 25 In the diagram, 'a' represents the energy distribution of the Volmer-Heyrovsky basic hydrogen evolution reaction process, the inset shows the optimized configuration of the intermediate, and TS represents the transition state. Figure 25 In this context, b represents Ru1 / PNC at -0.8 to -1.2 V vs. Hg / HgO in 0.1 MKOH electrolyte; Figure 25 In the figure, c represents the polarization curve of the AEM cell with the self-made IrRuOx catalyst as the anode at 60℃; Figure 25 In this context, d represents Pt / C (1.2 mg Pt·cm). -2 ) and Ru1 / PNC (0.1 mg Ru·cm -2 ) at 2A·cm -2 A schematic diagram of the long-term durability test results; Figure 25 In this context, 'e' represents a comparison of the reaction time, decay rate, and current density of the composite coordination single-atom catalyst (Ru1 / PNC) of this application embodiment with existing alkaline hydrogen evolution reaction catalysts (where 'this work' refers to the composite coordination single-atom catalyst Ru1 / PNC of Example 1 of this application). Detailed Implementation

[0016] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0017] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0018] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, a~b (i.e., a and b), a~c, b~c, or a~b~c, where a, b, and c can be single or multiple.

[0019] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0020] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0021] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass in the embodiments of this application can be a well-known unit of mass in the chemical industry, such as µg, mg, g, or kg.

[0022] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0023] To address the technical problems of low kinetics and low reactivity of alkaline hydrogen evolution reaction in the prior art, this application proposes the following technical solution.

[0024] In a first aspect, embodiments of this application provide a composite coordination single-atom catalyst, which includes a support and a metal center. The support includes auxiliary coordinating atoms, and at least two auxiliary coordinating atoms are coupled with the metal center to form a catalytically active center. The metal center includes a single-atom metal center, and the auxiliary coordinating atoms include at least two of C, N, P, S, and Cr.

[0025] Among them, the single-atom catalyst in the composite coordination single-atom catalyst refers to the metal center being in a single-atom dispersed state, and the single-atom dispersed metal center is coupled with two or more auxiliary coordinating atoms to form a composite coordination catalyst.

[0026] The activity of the alkaline hydrogen evolution reaction (HER) mainly depends on the H2O dissociation step and the proton production rate. In the composite coordination single-atom catalyst of this application, the metal center in a single-atom dispersed state and the auxiliary coordinating atom bifunctional group form a Lewis acid-base pair. Through the synergistic effect of the Lewis acid-base pair, the dissociation energy barrier of H2O is lowered, and the dissociation rate of H2O and the proton production rate are increased, thereby greatly improving the activity of the alkaline HER. Therefore, the composite catalyst of this application exhibits excellent catalytic effect on the alkaline HER. Furthermore, by anchoring the metal center with auxiliary coordinating atoms, the composite coordination single-atom catalyst of this application not only improves the catalytic activity of the composite coordination single-atom catalyst but also greatly improves its stability and durability.

[0027] like Figure 1 Duval Chatter Duncanson (b) Chatt According to the Duncanson (DCD) bonding model, the H₂O molecule can feed electrons into the empty d orbitals of the metal to form σ bonds, known as H₂O as a metal σ donor. Simultaneously, the metal has filled d orbitals, which can feed electrons back into the empty d orbitals of H₂O. The orbital refers to the π-electron feedback between the metal and H₂O. Generally, metals exhibit strong σ-electron donation and weak π-electron donation between themselves and H₂O, making them Lewis acid centers and thus difficult to activate H₂O. Conversely, lower valence metals exhibit a stronger π-electron transfer ability than σ-electron donation, making them potential Lewis base activators to break the OH bonds in the H₂O molecule.

[0028] This application's embodiments of the composite coordination single-atom catalyst greatly improve the catalytic activity of the composite coordination single-atom catalyst for the hydrogen evolution reaction (HER) by adjusting the electron-donating ability of the metal center through the auxiliary coordinating atom. Furthermore, this application's embodiments also elucidate the bifunctional mechanism in the basic hydrogen evolution reaction through the concept of an atomic Lewis acid-base pair. In this application's embodiments, the auxiliary coordinating atom and the metal center of the composite coordination single-atom catalyst act as a bifunctional catalyst, enhancing the basic hydrogen evolution reaction by adjusting the coordination environment of the metal center, i.e., single-atom metal catalysts (SACs), through the auxiliary coordinating atom. Figure 1 (c in the text)

[0029] In some embodiments, the metal center element in the composite coordination single-atom catalyst of this application includes at least one metal element selected from Ru, Pt, and Ir. In further embodiments, in the same composite coordination single-atom catalyst, the metal atoms of multiple metal centers may be the same or different, without specific limitation. In exemplary examples, the metal center may be Ru, Pt, or Ir, and different metal center elements of the same composite coordination single-atom catalyst may also include Ru and Pt, without specific limitation. These metals can be single-atom metal catalysts with certain catalytic activity, and these single-atom metal catalysts can form atomic pairs with auxiliary metal ligand atoms as metal centers, effectively improving the activity of the alkaline hydrogen evolution reaction.

[0030] In some embodiments, the mass percentage of the metal element in the metal center of the composite coordination single-atom catalyst can be 0.5~10 wt.%, preferably 0.5wt.%~8wt.%, 0.5wt.%~5wt.%, 0.5wt.%~4wt.%, 1wt.%~8wt.%, 1wt.%~5wt.%, or 2.7wt.%~3.6wt.%. In exemplary examples, the mass percentage of the metal element in the metal center of the composite coordination single-atom catalyst can be 0.5wt.%, 1wt.%, 1.5wt.%, 2wt.%, 2.5wt.%, 3wt.%, 3.5wt.%, 4wt.%, 4.5wt.%, 5wt.%, 5.5wt.%, 6wt.%, 6.5wt.%, 7wt.%, 7.5wt.%, 8wt.%, 8.5wt.%, 9wt.%, 9.5wt.%, or 10wt.%, or any value between any two ranges. By controlling the mass percentage of the metal element in the metal center within this range, the catalytic efficiency of the composite coordination single-atom catalyst can be further improved while reducing the amount of metal element used, thus lowering the cost of the composite coordination single-atom catalyst.

[0031] In some embodiments, the auxiliary coordinating atom may include C, and at least one of P, N, S, and Cr. In other embodiments, the auxiliary coordinating atom may include P, and at least one of C, N, S, and Cr.

[0032] It should be noted that there can be two, three, or four auxiliary coordinating atoms coupled to a metal center; the specific number is not limited.

[0033] In some embodiments, the metal center elements of different active catalytic centers in the same composite coordination single-atom catalyst can be the same or different. In an exemplary embodiment, the same composite coordination single-atom catalyst may simultaneously include both Ru and Pt metal centers. In other embodiments, when the metal centers of different active catalytic centers are the same in the same composite coordination single-atom catalyst, the auxiliary coordinating atoms coupled to the metal centers can also be different. In an exemplary embodiment, when the metal centers of different active catalytic centers are all Ru metal centers in the same composite coordination single-atom catalyst, one Ru metal center can be coupled with three N atoms and one P atom, and another Ru metal center can be coupled with two N atoms and two P atoms. Elements such as P, N, S, and Cr have oxophilic properties. Through the coordination of these elements with the metal centers, the auxiliary coordinating atoms can form Lewis pairs with the metal centers, thereby reducing the dissociation energy of H₂O and effectively improving the catalytic efficiency of the composite coordination single-atom catalyst for the alkaline hydrogen evolution reaction.

[0034] In some embodiments, in the same composite coordination single-atom catalyst, the auxiliary coordinating atoms coupled to different metal centers can be the same or different, and there is no specific limitation. In an exemplary example, the metal center of the composite coordination single-atom catalyst is Ru, wherein some Ru metal centers can be coupled with N atoms, and other Ru metal centers can be coupled with N atoms and P atoms.

[0035] In some embodiments, the auxiliary coordinating atom includes P, and includes at least one of C, N, S, and Cr.

[0036] In some embodiments, the composite coordination single-atom catalyst may contain phosphorus (P). In further embodiments, the P content in the composite coordination single-atom catalyst may be greater than 0 and less than or equal to 10 wt.%, and may be selected as 0.1 wt.%~10 wt.%, 0.5 wt.%~10 wt.%, 0.5 wt.%~8 wt.%, 0.5 wt.%~6 wt.%, or 2 wt.%~6 wt.%. In the exemplary embodiment, the content of P element in the composite coordination single-atom catalyst of this application can be a typical but non-limiting value such as 0.1wt.%, 0.2wt.%, 0.3wt.%, 0.4wt.%, 0.5wt.%, 0.6wt.%, 0.7wt.%, 0.8wt.%, 0.9wt.%, 1wt.%, 1.5wt.%, 2wt.%, 2.5wt.%, 3wt.%, 3.4wt.%, 4wt.%, 4.5wt.%, 5wt.%, 5.5wt.%, 6wt.%, 6.5wt.%, 7wt.%, 7.5wt.%, 8wt.%, 8.5wt.%, 9wt.%, 9.5wt.%, 10wt.%, or any value between any two ranges.

[0037] In some embodiments, the composite coordination single-atom catalyst of the present application embodiment may simultaneously include N and P elements, and the auxiliary coordinating atoms include N and P. In further embodiments, the molar ratio of P to N elements in the composite coordination single-atom catalyst of the present application embodiment may be greater than 0 and less than or equal to 4, and the molar ratio of P to N elements may be selected as 0.1~4, 0.1~3, 0.1~2, 0.1~1, 0.3~4, 0.3~2, or 0.3~1. In exemplary examples, the molar ratio of P to N elements in the composite coordination single-atom catalyst of the present application embodiment may be a typical but non-limiting value such as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, or 4, or any value between any two numerical ranges.

[0038] The addition of P can improve the catalytic activity of the composite coordination single-atom catalyst in the embodiments of this application. For example, P, as an auxiliary coordinating atom, couples with a monodisperse metal active center such as Ru, which can switch the rate-determining step (RDS) of the alkaline hydrogen evolution reaction from the proton adsorption (Volmer) step to the electrochemical desorption (Heyrovsky) step. By controlling the content of P within this range, the catalytic activity of the composite coordination single-atom catalyst can be further improved.

[0039] In some embodiments, the metal center of the composite coordination single-atom catalyst of this application can be Ru, and the auxiliary coordinating atoms can include N and P. In an exemplary example, a Ru metal center can couple three N atoms and one P atom to form a Ru1-N3P1 structure. Four N atoms anchor a Ru center to form a Ru1-N4 structure. Through the formation of Ru-N pairs between Ru atoms and N atoms, 0.24e electrons are transferred from the Ru center to each surrounding N atom, resulting in a more positive Ru center and a more negative N atom, allowing the Ru center and N atoms to serve as Lewis acid (LA) and Lewis base (LB) sites, respectively. When a coordinating N atom in the Ru1-N4 structure is replaced by P to form the Ru1-N3P1 structure, the adjacent P will transfer 0.34e electrons to the Ru center, making Ru in the Ru-P pair relatively electron-rich and P relatively electron-poor compared to the Ru-N pair. This allows Ru and P to perform dual functions as LB and LA sites, respectively, effectively improving the catalytic efficiency of the composite coordination single-atom catalyst. Furthermore, the charge redistribution induced by the asymmetric Ru1-N3P1 moiety likely plays an indispensable role in promoting water dissociation. The presence of Ru-P can significantly reduce the dissociation energy of H2O, thereby switching the rate-determining step of the alkaline hydrogen evolution reaction from the Volmer step to the Heyrovsky step, significantly improving the catalytic performance of the composite coordination single-atom catalyst. The strong electronic coupling of the Ru-P Lewis pair can also inhibit the aggregation and desorption of active sites, thus enabling the composite coordination single-atom catalyst of the present application embodiments to maintain excellent durability at high current densities.

[0040] In some embodiments, the composite coordination single-atom catalyst of this application may include a layered structure. In a further embodiment, the composite coordination single-atom catalyst may include a micron-scale two-dimensional layered structure. The layered structure of the composite coordination single-atom catalyst is beneficial for further promoting the coupling between the metal center and the auxiliary ligand atoms, increasing the number of active centers of the composite coordination single-atom catalyst, and further improving the catalytic activity of the composite coordination single-atom catalyst. At the same time, the multilayer structure can also further increase the specific surface area of ​​the composite coordination single-atom catalyst, increase the contact between the active centers of the composite coordination single-atom catalyst and H2O, and further improve the catalytic activity of the composite coordination single-atom catalyst.

[0041] In some embodiments, the specific surface area of ​​the composite coordination single-atom catalyst in this application can be 100~2000 m². 2 / g, selectable from 100~500m 2 / g, 500~200m 2 / g, 500~1500m 2 / g, 500~1000m 2 / g、800~2000m 2 / g, 800~1500m 2 / g. In the exemplary embodiment, the specific surface area of ​​the composite coordination single-atom catalyst in this application can be 100m². 2 / g、200m 2 / g、300m 2 / g、400m 2 / g、500m 2 / g、600m 2 / g、700m 2 / g、800m 2 / g、900m 2 / g, 1000m 2 / g、1100m 2 / g、1200m 2 / g、1300m 2 / g, 1400m 2 / g, 1500m 2 / g, 1600m 2 / g, 1700m 2 / g、1800m 2 / g、1900m 2 / g、2000m 2 / g is a typical but not limiting value, or any value between any two ranges. Controlling the specific surface area of ​​the composite coordination single-atom catalyst in the embodiments of this application within this range further promotes the contact between the active center in the composite coordination single-atom catalyst and H2O, improves the activity of the composite coordination single-atom catalyst, and further improves the stability of the composite coordination single-atom catalyst.

[0042] In some embodiments, the composite coordination single-atom catalyst support of this application includes carbon material. By loading the catalytic active center with carbon material, the stability of the support and the stability of the catalytic active center loading are effectively improved, thereby further improving the stability of the composite coordination single-atom catalyst.

[0043] Secondly, embodiments of this application provide a method for preparing the aforementioned composite coordination single-atom catalyst. The method for preparing the composite coordination single-atom catalyst of this application includes the following steps: Step S10: The carrier material and the metal source are subjected to a first mixing process to obtain a first mixture, wherein the carrier material is doped with elements that assist coordination atoms, and the metal source contains metal elements with metal centers. Step S20: The first mixture is subjected to a first heating treatment to obtain a composite coordination single-atom catalyst.

[0044] The method for preparing the composite coordination single-atom catalyst in this application involves heating a first mixture to couple the auxiliary coordinating atoms in the support material with the metal element of the metal source, forming a monodisperse metal active center coupled with an auxiliary coordinating atom catalytic active center. This yields a composite coordination single-atom catalyst capable of efficiently catalyzing the alkaline hydrogen evolution reaction. Furthermore, the method for preparing the composite coordination single-atom catalyst in this application has few steps, is simple to operate, and is suitable for large-scale industrial production.

[0045] Step S10: By performing a first mixing treatment between the support material and the metal source, the dopant elements in the support material and the metal elements in the metal source are mixed and contacted, thereby promoting the coupling of the dopant elements and the metal elements in the subsequent first heating reaction and forming catalytic active centers.

[0046] In some embodiments, the method for preparing the carrier material may include the following steps: Step S101: Mix the carbon source and the dopant element source to obtain the precursor of the carrier material; Step S102: The precursor of the carrier material is subjected to heating and carbonization treatment to obtain the carrier material.

[0047] By heating and carbonizing a precursor obtained by mixing a carbon source and a dopant source to prepare a support material, the type and content of dopants in the support material can be effectively controlled, thereby controlling the type and content of auxiliary coordinating atoms in the composite coordination single-atom catalyst and further improving the catalytic activity of the composite coordination single-atom catalyst.

[0048] In some embodiments, the carbon source may include at least one of melamine, cyanuric acid, and alanine.

[0049] In some embodiments, the dopant source may include at least one of an N source, a P source, a S source, and a Cr source. The N source may include at least one of melamine, cyanuric acid, and alanine, and the P source may include phytic acid. It should be noted that the alanine contained in the carbon and N sources may include at least one of L-alanine and D-alanine.

[0050] In some embodiments, the temperature for the carbonization treatment can be 400~600℃, optionally 450~600℃ or 450~550℃. In exemplary examples, the temperature for the carbonization treatment can be typical but not limiting temperatures such as 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, and 600℃, or any temperature between any two temperature ranges. The carbonization treatment time can be 1~5 hours, optionally 1~4 hours, 1~2 hours, 1.5~2.5 hours, or 2~5 hours. In the example, the heating carbonization treatment time can be a typical but non-limiting time such as 1h, 1.5h, 2h, 2.5h, 3h, or any time between any two temperature ranges.

[0051] In some embodiments, when the support material is carbon and the dopant element is nitrogen (N), it is referred to as an NC support. The preparation method of this NC support material may include the following steps: melamine, cyanuric acid, and L-alanine are dispersed in water and stirred at 100°C to obtain a homogeneous white polymer, which serves as the precursor for the support material. The precursor is placed in a crucible and heated at 500°C for 2 hours in air, then cooled to obtain the support material. The NC support prepared by the above method exhibits a uniform distribution of nitrogen (N) elements, which is beneficial for promoting the subsequent coupling of N atoms with the metal center, increasing the number of catalytically active centers in the composite coordination single-atom catalyst, and further improving the catalytic effect of the composite coordination single-atom catalyst.

[0052] In some embodiments, when the support material is carbon and the doping elements are N and P, it is referred to as a PNC support. The preparation method of the PNC support material may include the following steps: melamine, cyanuric acid, L-alanine, and phytic acid are dispersed in water and stirred at 100°C to obtain a homogeneous white polymer, which is the precursor of the support material. The precursor of the support material is placed in a dry place and heated at 500°C for 2 hours in an air atmosphere, then cooled to obtain the support material. The PNC support prepared by the above method can not only flexibly adjust the N and P content in the PCN support according to actual needs, but also has a uniform distribution of N and P in the PNC support, which is beneficial to promoting the coupling of subsequent N and P atoms with the metal center, increasing the number of catalytic active centers in the composite coordination single-atom catalyst, and further improving the catalytic effect of the composite coordination single-atom catalyst.

[0053] In some embodiments, the metal element in the metal source can be either a metal atom or a metal ion. In further embodiments, the valence state of the metal element in the metal source can be the same as or different from that of the metal element at the metal center; there is no specific limitation.

[0054] In some embodiments, the first mixing process may include the following steps: Step S11: Dissolve the metal source in water to obtain a metal solution; Step S12: Disperse the carrier material in water to obtain a carrier material slurry; Step S13: Mix the carrier material slurry with the metal solution to obtain a mixed slurry; Step S14: Dry the mixed slurry to obtain the first mixture.

[0055] By dissolving or dispersing the metal source and support material in water to form a mixed slurry, and then drying it to prepare the first mixture, the mixing uniformity of the support material and the metal source is effectively improved, thereby further improving the dispersion of metal elements in the support material. This improves the dispersion of metal centers in the subsequently prepared composite coordination single-atom catalyst and enhances the catalytic activity of the composite coordination single-atom catalyst.

[0056] In some embodiments, the drying process can be freeze-drying.

[0057] Step S20: The first mixture is subjected to a first heating treatment in step S20 to promote the coupling of the metal center and the auxiliary coordinating atoms to form a catalytic active center, thereby obtaining a composite coordination single-atom catalyst.

[0058] In some embodiments, the first heat treatment may be performed under a protective atmosphere such as argon.

[0059] In some embodiments, the temperature of the first heating treatment can be 700~1000℃, and can be selected as 800~1000℃, 700~900℃, or 750~900℃. In exemplary examples, the temperature of the first heating treatment can be a typical but non-limiting temperature such as 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, 900℃, or 1000℃, or any temperature between any two numerical ranges.

[0060] In some embodiments, the duration of the first heating treatment can be 1 to 3 hours, specifically 1 to 2.5 hours, 1.5 to 3 hours, or 2 to 3 hours. In exemplary embodiments, the duration of the first heating treatment can be a typical but non-limiting time such as 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours, or any time between any two temperature ranges.

[0061] By controlling the temperature and time of the first heating treatment within this range, the coupling between the metal center and the auxiliary coordinating atoms is further promoted, the content of catalytic active centers in the composite coordination single-atom catalyst is increased, the catalytic effect of the composite coordination single-atom catalyst is improved, and energy consumption is reduced.

[0062] In some embodiments, when the support for the composite coordination single-atom catalyst is the PNC support described above, and the metal center element is Ru, the preparation method of the composite coordination single-atom catalyst in this application embodiment may include the following steps: dispersing the PCN support in water to obtain a PNC support suspension; adding RuCl3 solution to the PNC support; stirring for 12 hours; and freeze-drying the reaction solution to obtain a first mixture. The first mixture is heated at 800°C for 2 hours under an argon atmosphere and then cooled to obtain the composite coordination single-atom catalyst. This method allows for flexible adjustment of the Ru content in the composite coordination single-atom catalyst, and the formation of Ru-P pairs within the composite coordination single-atom catalyst effectively improves its catalytic effect.

[0063] Thirdly, embodiments of this application provide another method for preparing the above-mentioned composite coordination single-atom catalyst. The preparation method provided in the third aspect of this application includes the following steps: Step G10: The metal catalyst containing the metal center metal element is mixed with the doped element source in a second mixing to obtain a second mixture; Step G20: The second mixture is subjected to a second heating treatment to obtain a composite coordinated single-atom catalyst.

[0064] The preparation method provided in the third aspect of this application promotes the coupling of dopants and metal elements in the second mixture through a second heat treatment to form a catalytically active center containing a metal center and auxiliary coordinating atoms, thereby obtaining a composite coordination single-atom catalyst with high catalytic performance. This composite coordination single-atom catalyst can effectively improve the reaction activity of alkaline hydrogen evolution reaction.

[0065] Step G10: In step G10, the metal catalyst and the dopant source are mixed in a second process, which makes the metal catalyst and the dopant source uniformly dispersed and promotes the contact between the metal element and the dopant element. This further promotes the coupling between the auxiliary coordination atoms and the metal center during the second heating process, and further improves the catalytic effect of the composite coordination single-atom catalyst.

[0066] In some embodiments, the metal catalyst includes single-atom metal catalysts (SACs). By adjusting the coordination environment of the single-atom metal catalyst through doping, the catalytic activity of the catalyst in the alkaline hydrogen evolution reaction is greatly improved. In exemplary embodiments, the metal catalyst may include at least one of a Pt / C catalyst and a Ru / C catalyst, which can be commercial catalysts.

[0067] In some embodiments, the dopant source may include at least one of a P source, an N source, a S source, and a Cr source, wherein the P source may include NaH2PO2·H2O, the N source may include melamine, the S source may include thiourea, and the Cr source may include Cr(NO3)3·9H2O.

[0068] The preparation method described in this application incorporates elements such as P, N, S, and Cr into Pt / C and Ru / C catalysts, enabling these elements to act as auxiliary coordinating atoms to couple Pt and Ru, forming new catalytic active centers and effectively improving the catalytic activity of the Pt / C and Ru / C catalysts.

[0069] In some embodiments, the mass ratio of the metal catalyst to the dopant source can be 1:1 to 1:20, preferably 1:1 to 1:15, 1:1 to 1:10, or 1:5 to 1:15. In exemplary examples, the mass ratio of the metal catalyst to the dopant source can be typical but not limited to magnitudes such as 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, and 1:20, or any ratio between any two numerical ranges. Controlling the mass ratio of the metal catalyst to the dopant source within this range further improves the catalytic activity of the prepared composite coordination single-atom catalyst.

[0070] In some embodiments, the second mixing process may include grinding and mixing; for example, the second mixing process may be performed by grinding with a mortar and pestle.

[0071] Step G20: By performing a second heating treatment, the coupling of metal elements and dopant elements in the second mixture is promoted to form active catalytic centers, thereby obtaining a composite coordination single-atom catalyst with high catalytic activity.

[0072] In some embodiments, the second heat treatment may be performed under a protective atmosphere such as argon.

[0073] In some embodiments, the temperature of the second heating treatment can be 250~600℃, optionally 250~500℃ or 250~400℃. In exemplary examples, the temperature of the second heating treatment can be typical but not limiting temperatures such as 250℃, 300℃, 400℃, 450℃, 500℃, 550℃, and 600℃, or any temperature between any two temperature ranges. The duration of the second heating treatment can be 1~5h, optionally 1~4h, 1~2h, 1.5~2.5h, or 2~5h. In exemplary examples, the duration of the second heating treatment can be typical but not limiting times such as 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, and 5h, or any time between any two temperature ranges. Controlling the temperature and duration of the second heating treatment within this range further promotes the coupling of the single-atom metal catalyst and the dopant element in the metal catalyst, forming a catalytic active center containing a metal center and auxiliary coordinating atoms, further improving the catalytic effect of the composite coordinated single-atom catalyst.

[0074] In some embodiments, when the metal catalyst is a Pt / C catalyst and the dopant element is P, the preparation method of this application includes the following steps: The Pt / C catalyst and NaH2PO2·H2O are thoroughly mixed in a mortar. The mixture is then transferred to a crucible and heated to 300°C at a heating rate of 2°C / min under an argon atmosphere, and held at this temperature for 2 hours. After the reaction is complete, the resulting powder is thoroughly washed with deionized water and dried under vacuum at 70°C to finally obtain the P-doped Pt / C catalyst, which is the composite coordination single-atom catalyst of this application.

[0075] Fourthly, embodiments of this application provide the application of the composite coordination single-atom catalyst described above in water electrolysis.

[0076] The composite coordination single-atom catalyst of the present application has a good catalytic effect on alkaline hydrogen evolution reaction, which can greatly reduce the dissociation energy of water and has broad application prospects in the electrolysis of water to produce clean energy.

[0077] To enable those skilled in the art to clearly understand the above-described implementation details and operations of this application, and to demonstrate the significant advancements in the performance of the composite coordination single-atom catalyst, its preparation method, and its application in the embodiments of this application, the following examples illustrate the above technical solutions.

[0078] Example 1 This embodiment provides a composite coordination single-atom catalyst, which includes a support and a metal center. The support includes auxiliary coordinating atoms, and the metal center is coupled with the auxiliary coordinating atoms to form a catalytic active center. The metal center is monodisperse. The metal center is Ru, and the auxiliary coordinating atoms include N and P. One Ru metal center is coupled with three N atoms and one P atom to form a Ru1-N3P catalytic active center. Figure 2 The preparation method of the composite coordination single-atom catalyst shown in this embodiment is as follows: Step S1: Disperse 2g melamine, 2g cyanuric acid, 2g L-alanine and 400μL phytic acid (50wt.%) in 100mL deionized water, stir vigorously at 100℃ to obtain a uniform white polymer precursor, and dry.

[0079] Step S2: Place the polymer precursor obtained after drying in step S1 in a crucible and heat it at 500°C for 2 hours in an air atmosphere to obtain the PNC support.

[0080] Step S3: 200 mg of PNC support was ultrasonically dispersed in 10 mL of deionized water to obtain a suspension. 5 mg of RuCl3 solution was slowly added to the suspension, and the mixture was stirred for 12 h. The resulting slurry was freeze-dried and then heated at 800 °C for 2 h under argon protection to obtain the final sample, which is the composite coordination single-atom catalyst of this embodiment (denoted as Ru1 / PNC). The Ru metal content of the composite coordination single-atom catalyst Ru1 / PNC in this embodiment is 3.58 wt.%.

[0081] Examples 2 to 5 Examples 2 to 5 each provide a composite coordination single-atom catalyst. The composite coordination single-atom catalysts and their preparation methods in Examples 2 to 4 are basically the same as those in Example 1, except that the content of phytic acid added during preparation is different, resulting in different amounts of P element doping in the prepared composite coordination single-atom catalysts.

[0082] The molar ratio of P to N in the composite coordination single-atom catalysts of Examples 1 to 5, and the content of phytic acid added during preparation are shown in Table 1.

[0083] Example 6 This embodiment provides a composite coordination single-atom catalyst. The preparation method of this composite coordination single-atom catalyst includes the following steps: Step S1: Mix commercial Pt / C (20wt%) with phosphorus source NaH2PO2·H2O in a mortar at a mass ratio of 1:10 to obtain a mixture.

[0084] Step S2: The mixture was then transferred to a crucible and heated to 300°C at a heating rate of 2°C / min under an argon atmosphere, and held at this temperature for 2 hours. After the reaction was complete, the resulting powder was thoroughly washed with deionized water and dried under vacuum at 70°C to obtain the P-doped Pt / C catalyst, which is the composite coordination single-atom catalyst of this embodiment.

[0085] Example 7 This embodiment provides a composite coordination single-atom catalyst. The composite coordination single-atom catalyst and its preparation method in this embodiment are basically the same as those in Example 6, except that the composite coordination single-atom catalyst in this embodiment is prepared by mixing a commercial Ru / C catalyst with a phosphorus source.

[0086] Comparative Example 1 This embodiment provides a catalyst. The catalyst in this embodiment comprises four N atoms coupled to a Ru metal center, forming a Ru1-N4 structure. The preparation method of the catalyst in this embodiment is basically the same as that of the composite coordination single-atom catalyst preparation method in Example 1, except that phytic acid is not added in step S1, and the obtained support is an NC support. The Ru metal content of the Ru1 / NC catalyst in this embodiment is 2.70 wt.%. This composite coordination single-atom catalyst is denoted as Ru1-NC.

[0087] Comparative Example 2 This comparative example provides a catalyst, which is the commercial Pt / C catalyst from Example 6.

[0088] Comparative Example 3 This comparative example provides a catalyst, which is the commercial Ru / C catalyst in Example 7.

[0089] Performance evaluation: Electrochemical measurements were performed on the composite single-atom catalysts of Examples 1 to 7 and the catalysts of Comparative Examples 1 to 3, and the turnover frequency (TOF) values ​​were measured. The results are as follows: Figure 3 Figure 4 As shown in Table 1.

[0090] in, Figure 3 In the figure, 'a' represents the linear sweep voltammograms of composite coordination single-atom catalysts with different P / N atomic ratios (i.e., molar ratios) in Examples 1 to 5 and the catalyst in Comparative Example 1 (where the color scale represents the current density). Figure 3 In the diagram, b represents the TOF value of HER activity as a function of the P / N atomic ratio.

[0091] Figure 4In the figure, 'a' represents the polarization curves of the composite coordination single-atom catalyst in Example 7 and the catalyst in Comparative Example 3. Figure 4 In the figure, b represents the polarization curves of the complex coordination single-atom catalyst of Example 6 and the catalyst of Comparative Example 2; Figure 4 In the diagram, c represents the relative activity of the current density on the overpotential scale for the composite coordination single-atom catalysts of Examples 6-7 and Comparative Examples 2-3.

[0092] Table 1

[0093] like Figure 3 As shown in Table 1, when the Ru metal heavy metal in the catalyst of Comparative Example 1 is coordinated only with the N auxiliary coordinating atom, the TOF value measured under the same conditions is low, only 0.40 s. -1 When P is doped, the TOF values ​​of the composite coordination single-atom catalysts with different P / N atomic ratios in Examples 1-5 are significantly improved. This indicates that the composite coordination single-atom catalysts and their preparation methods prepared in this application have high catalytic activity.

[0094] In addition, such as Figure 3 As shown in Table 1, the activity of the composite coordination single-atom catalyst varies with different P doping amounts. As the P / N (molar ratio) increases, the current density increases until it reaches a peak. When P species are added to the N-coordinated Ru single-atom metal catalyst, the TOF value increases significantly. When the P / N ratio reaches approximately 0.7, the TOF plateaus, indicating the formation of a new coordination structure. This ligand structure may dominate the activity through a P doping strategy. The composite coordination single-atom catalyst and its preparation method described in this application can further enhance the catalytic activity of the composite coordination single-atom catalyst through P doping.

[0095] Figure 4 a and Figure 4 As shown in b, the overpotential of the P-modified commercial catalyst is significantly reduced. Specifically, compared to the commercial Pt / C of Comparative Example 2, the P-modified composite coordination single-atom catalyst of Example 6 exhibits a significantly reduced overpotential at a current density of 50 mA·cm⁻¹. -2 The overpotential decreased by 24.1 mV; compared to the commercial Ru / C catalyst of Comparative Example 3, the P-modified composite coordination single-atom catalyst of Example 7 showed a higher overpotential at a current density of 50 mA·cm⁻¹. -2The overpotential decreased by 50.5 mV. In Example 6, the average current density of the P-doped Pt / C catalyst was 1.69 times that of the Pt / C catalyst in Example 2, and in Example 7, the average current density of the P-doped Ru / C catalyst was 2.74 times that of the Ru / C catalyst in Example 3. This indicates that the composite coordination single-atom catalysts of this application have high catalytic activity, and that the preparation method of this application can effectively improve the activity of existing catalysts by doping with P.

[0096] Characterization analysis In addition to electrochemical measurements and TOF value determinations, the composite coordination single-atom catalyst of Example 1 and the catalyst of Comparative Example 1 were subjected to characterization analysis, CO stripping experiments, apparent activation energy evaluation, kinetic isotope effect experiments, and AMC experiments to further investigate and analyze their performance. The experimental methods for characterization analysis, electrochemical measurements, CO stripping experiments, apparent activation energy evaluation, kinetic isotope effect experiments, and AMC experiments are as follows: Characterization methods The morphology and microstructure of the samples were analyzed using scanning electron microscopy (SEM) (HITACHI S-4800, Japan) and transmission electron microscopy (TEM) (JEM-2100F, JEOL Corporation, Japan). Elemental distribution was imaged using a TEM equipped with an Oxford Instruments X-ray energy-dispersive spectrometer. X-ray powder diffraction (XRD) patterns were obtained using a Rigaku D / max-2500n diffractometer with Cu Kα rays (λ=1.5418Å), operating at 40 kV and 200 mA. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC HAADF-STEM) was performed at 200 kV using an aberration-corrected JEOL ARM 200CF. Corresponding EELS spectra were acquired using a GIF camera. The detector convergence half-angle, HAADF collection half-angle, and EELS collection half-angle were 31.5 mrad, 68–280 mrad, and 50 mrad, respectively. X-ray photoelectron spectroscopy (XPS) data were acquired using a Thermo ESCALAB 250 XI PHI-5000 system. Brunauer-Emmett-Teller (BET) surface area was determined using the N2 adsorption-desorption isotherm at 77 K obtained from a Powder Processing ASAP 2460 instrument. Inductively coupled plasma atomic emission spectrometry (ICP-AES) for mineral inorganic nutrients was performed on a PerkinElmer Avio 500 instrument to determine metal content. In-situ Fourier transform infrared (FTIR) spectra of the alkaline hydrogen evolution reaction were recorded using a Nicolai 6700 spectrometer and an MCT detector, with a total of 32 scans and a resolution of [resolution missing]. Pyridine-FTIR spectra were measured using a Bruker TENSOR 27 spectrometer. Temperature-programmed desorption of CO2 and NH3 was performed using a Powder Processing / Autochem II 2920 chemisorption analyzer.

[0097] Ru K-edge analysis was performed at the BL14W1 beamline of the Shanghai Synchrotron Radiation Facility. Prior to beamline analysis, the sample was pressed into a 1 cm diameter sheet and sealed with Kapton tape. XAFS spectra were recorded at room temperature using a Bruker 5040 four-channel silicon drift detector (SDD). Ru K-edge extended X-ray absorption fine structure (EXAFS) spectra were recorded in transmission mode. The XAFS data were analyzed using the Demeter 51 software package.

[0098] Electrochemical measurement methods A catalyst slurry was prepared by ultrasonically mixing 5 mg of catalyst powder with 970 μL of ethanol and 30 μL of 5% Nafion solution (Sigma-Aldrich) for 20 min. A glassy carbon rotating disk electrode (GCRDE) with a diameter of 3 mm coated with the catalyst slurry was used as the working electrode. 5 μL of the catalyst slurry was spin-coated onto the GCRDE. An Hg / HgO electrode was used as the reference electrode, and a graphite rod as the counter electrode. Electrochemical measurements were performed using a three-electrode system on an electrochemical workstation (CHI 760E). Polarization curves were measured for Hg / HgO from -0.85 to -1.3 V at a scan rate of 5 mV·s. -1 The rotational speed is 2400 r·min⁻¹, and the internal resistance is ( i R) compensation is 90%. Unless otherwise stated, all potentials are referenced to the Nernst equation: E(RHE) = E(Hg / HgO) + 0.0591 × pH + 0.098 V.

[0099] CO stripping experimental method CO stripping experiments were conducted in a 1.0 M KOH solution. The working electrode containing the catalyst was immersed in the solution, and CO gas was introduced for 20 min to saturate the electrolyte with CO. Once the catalyst was covered with CO at the open-circuit potential, the working electrode was transferred to an Ar-saturated 1.0 M KOH electrolyte. The scan rate was 50 mV·s in the range of 0.024–1.224 V (vs. RHE). -1 .

[0100] Apparent activation energy evaluation method Polarization curves were tested from -0.9 to -1.3 V vs. V, and the apparent activation energy (Ea) was calculated. Hg / HgO reacted with HgO in 1.0 M KOH solution at a rate of 5 mV·s⁻¹. -1The scan rate was used to react at different temperatures (25, 35, 45, 55, and 65 °C), with each reaction held at the temperature for 10 minutes to maintain temperature stability. Therefore, Ea:In can be further calculated by fitting the slope of the Arrhenius curve. j =A-Ea / RT, where A is the apparent pre-exponential factor, R is the ideal gas constant (8.314 J·K⁻¹ mol⁻¹), and T is the Kelvin temperature (K).

[0101] Kinetic Isotope Effect Experimental Method Kinetic isotope effects (KIEs) experiments were conducted in a 1.0 M KOH (H₂O or D₂O) electrolyte. The current densities corresponding to a given overpotential (η) are denoted as j. H and j D Then calculate KIE using the following formula: KIE=[j H / j D ] η .

[0102] TOF Calculation Method Transition frequency (TOF, s) -1 Calculate TOF using the following equation: j / (n×F×N) ,in j For current density, n The number of electrons transferred in the reaction (HER = 2). F Faraday constant (96485 C·mol) -1 N represents the number of moles of active sites. Specifically, the number of active sites... N It is estimated by the total metal loading on the electrodes.

[0103] AEM battery experimental method A serpentine flow channel is adopted (effective area: 1×1cm). 2 The practical application of the catalyst was tested in an anion exchange membrane (AEM) cell. Ru1 / PNC and commercial Pt / C (40 wt.%) were used as cathode catalysts, and a self-made RuIrOx titanium felt was used as the anode. The prepared catalyst slurry was initially air-sprayed onto porous nickel foam. The catalyst-coated nickel foam was then assembled with an anion exchange membrane (Fumasep, FAA-3-50) to form a self-made integrated AEM cell. Notably, the anion exchange membrane was immersed in a 1 M KOH solution for at least 24 hours before use to exchange Cl-. - For OH - The AEM battery operated at 60°C and ambient pressure using 1M KOH as the electrolyte. The performance of the assembled AEM battery was evaluated by measuring the polarization profiles from 1.2V to 3.0V. At 60°C, the current density was 2 Acm⁻¹.-2 Durability testing was conducted using the chronopotential method.

[0104] Theoretical calculation All calculations were based on density functional theory and performed using the Vienna Quantum Chemistry Ab initio Simulation Software (VASP). The generalized gradient approximation (GGA) and the Perdew-Burke-Ernzerhof (PBE) exchange-correlated functionals were employed. Van der Waals corrections in all calculations were performed using the DFT-D3 method. Cutoff energy, total energy convergence, and force convergence were set to 500 eV, 1 × 10⁻⁶, and 1 × 10⁻⁶, respectively. -3 eV and 0.01eV·Å -1 For pure graphene, a 7×7 supercell containing 98 C atoms was used, and a 20 Å vacuum layer was constructed to exclude interactions between adjacent cells. Spin polarization was considered for the 4d and 5s valence electrons of Ru, while spin polarization was considered for the 2s and 2p valence electrons of C, N, P, and O. The Ru-N4 and Ru-N3P1 single-atom sites were created by replacing two adjacent C atoms with one Ru atom, and four adjacent coordinating C atoms were replaced with four N atoms or three N atoms and one P atom, respectively. For the irreducible Brillouin zone, the Monkhorst-Pack scheme K-point grid sampling was set to 5×5×1. Bader charge analysis was carefully performed after each relaxation.

[0105] The Gibbs free energy changes for each step of the reaction are obtained through the following equation (1): ΔG = ΔE + ΔZPE – TΔS (1) Where ΔE represents the reaction energy change calculated by DFT, and ΔZPE and ΔS represent the changes in zero-point energy and entropy, respectively. The calculation uses the computational hydrogen electrode (CHE) model, where (H + The chemical potential of (+e-) is equal to 1 / 2 the chemical potential of H2. The transition states were discovered using the CINEB (Climbing Elastic Band) method. The initial and final states with the lowest energy were carefully examined, and all transition states were confirmed by frequency analysis.

[0106] Experimental results like Figure 5 a and Figure 6 , Figure 7 and Figure 8As shown, both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images indicate that the samples of the composite coordination single-atom catalyst of Example 1 and the catalyst of Comparative Example 1 are composed of stacked two-dimensional thin nanosheets. Furthermore, the absence of Ru nanoparticles in the high-resolution TEM indicates a highly dispersed state of Ru in both the composite coordination single-atom catalyst (Ru1 / PNC) of Example 1 and the catalyst Ru1 / NC of Comparative Example 1. The highly dispersed state of Ru was further confirmed by powder X-ray diffraction (XRD) patterns, as shown in Figure [Figure number missing]. Figure 9 As shown, only two broad peaks were observed at ~25° and 42°, which are attributed to the carbon substrate.

[0107] like Figure 5 b and Figure 10 As shown, aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC HAADF-STEM) confirmed that Ru in the composite coordination single-atom catalyst sample of Example 1 was atomically dispersed. The brighter spots, due to their greater Z-contrast, could be identified as isolated Ru single atoms. Energy-dispersive X-ray spectroscopy (EDS) elemental distribution also showed that Ru was uniformly distributed in the NC and PNC supports (…). Figure 5 c and Figure 11 The electron energy loss spectrum (EELS) confirmed the presence of P and N in Ru1 / PNC, suggesting the possibility of P / N coordinated single atoms. Figure 5 (d)

[0108] To further determine the coordination environments of Ru1 / PNC and Ru1 / NC, X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) studies were performed on the samples. The photon energy at the absorption threshold of Ru1 / PNC is lower than that of Ru1 / NC, indicating a lower valence state for Ru1 / PNC, consistent with XPS results (…). Figure 5 e and Figure 12 Consistent. Fourier Transform (FT) k 2 Weighted EXAFS spectra show that both Ru1 / PNC and Ru1 / NC exhibit a distinct peak at 1.45 Å (without phase shift), which is attributed to the Ru-N scattering path. Figure 5 (f) Furthermore, a shoulder peak of 1.80 Å appeared in Ru1 / PNC, which is attributed to the contribution of Ru-P. No Ru-Ru peak with a bond distance of 2.42 Å or greater was detected, indicating the presence of atomically dispersed Ru species in the PNC or NC network. Further quantitative least squares EXAFS curve fitting was used to investigate the coordination configuration of Ru units, revealing that Ru1 / PNC and Ru1 / NC are predominantly Ru1-N3P1 and Ru1-N4 configurations, respectively. Figure 5In other words, in Ru1 / PNC, the introduced P replaces one N atom in the Ru1-N4 moiety, forming a new Ru-P pair structure. This may be the reason why Ru1 / PNC exhibits excellent activity for the basic hydrogen evolution reaction. Figure 3 (a) Interestingly, most of the brighter Ru atoms are accompanied by darker P atoms, exhibiting a dimer-like pattern (a). Figure 5 (The yellow box next to b in the text).

[0109] Figure 5 The intensity distribution maps of several selected regions in b show that the average distance between coupled Ru-P pairs is ~0.23 nm. Figure 5 The results (h) are consistent with those obtained by EXAFS. To more intuitively demonstrate the existence of Ru-P pairs, X-ray photoelectron spectroscopy (XPS) of catalysts with different P contents was collected. The results show that with increasing P content, a convolution peak appears in the range of 130–135 eV, mainly attributed to OP, NP, and CP bonds; however, when the P doping amount is sufficiently high, a new peak appears at ~129 eV, corresponding to the Ru-P bond (h). Figure 5 (i) in the text. Furthermore, due to... 31 P has 100% isotopic abundance and a relatively high gyromagnetic ratio. The proposed Ru-P pair can be further used in solid-state applications. 31 P was measured using nuclear magnetic resonance. Figure 5 The j in the figure shows three well-resolved signals of PNC between 0 and -30 ppm, assigned to different P positions within the PNC frame, and P2. p The XPS results were consistent. However, a new peak appeared at -20.2 ppm (asterisk) in the Ru1 / PNC sample, which is a sensitive indicator of the coordination environment with the P donor. Furthermore, the projected density of states (PDOS) of Ru1 / PNC showed strong orbital coupling interactions between the Ru-P bonds, indicating that Ru4... d and P3 p There is significant overlap between the energy levels of the orbitals. Figure 5 The presence of k in the equation indicates the theoretical stability of the Ru1-N3P1 structure. Overall, we successfully synthesized and characterized structurally well-defined Ru-P and Ru-N pairs.

[0110] Catalytic performance and behavior study By constructing various atom pairs with different coordination environments, the correlation between these atom pairs and the performance of the alkaline hydrogen evolution reaction at well-defined active sites was determined. These catalysts were drop-coated onto a rotating ring-disk electrode (RRDE) and the reaction was carried out in a 1M KOH electrolyte. Figure 13 As shown in a, the geometric current density (j geometric Ru increases exponentially with increasing overpotential (η).1 / PNC exhibits faster kinetics than other reference catalysts, requiring only 16 mV overpotential to reach 10 mA·cm⁻¹. -2 In addition, such as Figure 14 and Figure 15 As shown, the formation of Ru nanoparticles (RuNPs) leads to relatively sluggish HER performance, thus demonstrating the superiority of Ru single atoms. The resulting Tafel slope of Ru1 / PNC is 39.4 mV·dec. -1 It is far lower than the 108.8 mVdec of Ru1 / NC. -1 This indicates that the constructed Ru-P pair ( Figure 16 The important role of ). It is worth noting that, due to similar BET areas, the double-layer capacitance (C) of Ru1 / PNC and Ru1 / NC is different. dl The values ​​were basically the same, eliminating the differences in active site exposure. Figures 17-18 The effect of ) . In addition to catalytic activity, in long-term chronopotential testing, Ru1 / PNC was more effective than Ru1 / NC (with appended) Figure 19 The Ru1 / PNC catalyst exhibits outstanding stability. These results indicate that the superior HER performance of Ru1 / PNC is driven by the Ru-P pair rather than a single Ru site. Furthermore, the mass-to-active-weight ratio (MSA) and time-to-flight (TOF) value of Ru1 / PNC also show the highest performance among these catalysts. Figure 13 (a) A comparison of the Tafel slope and overpotential of Ru1 / PNC with other previously reported SAC-based basic hydrogen evolution reaction electrocatalysts is shown in Figure 1. Figure 13 As shown in c, the superior performance of Ru1 / PNC is demonstrated.

[0111] Subsequently, embodiments of this application explain the reasons for the outstanding advantages of Ru1 / PNC in the alkaline hydrogen evolution reaction. First, the apparent activation energy (Ea) is calculated according to the Arrhenius equation to represent thermodynamic information ( Figures 20-21 The average Ea of Ru1 / NC is as high as 32 kJ·mol⁻¹. -1 This indicates that the rate-determining step involves the dissociation of water (i.e., the Volmer step). In contrast, the Ea values ​​of Ru1 / PNC and Ru / C are lower, suggesting that both the Ru-P atomic pairs and Ru nanoparticles promote the dissociation of H2O, but this may differ in other reaction pathways. Further kinetic isotope effect (KIE) experiments were conducted to investigate (see attached). Figure 24 Differences in reaction pathways. For example... Figure 13 As shown in d, due to the difference in zero-point energy between isotopic isomers, the activity of Ru / C decreased by 1.6 times ( j H / j DThe KIE values ​​of Ru1 / NC (3.4) and Ru1 / PNC (6.6) are classified as secondary KIE, indicating that their rate-determining step does not involve direct H-related bond breaking. In contrast, the increase in KIE values ​​for Ru1 / NC (3.4) and Ru1 / PNC (6.6) shifts to a dominant KIE, caused by direct H-related bond breaking events as their rate-determining steps, but in a different manner. Then, hydrogen (H+) is deposited via underpotential deposition. upd The location of H is used to study the bond breaking behavior related to H.

[0112] like Figure 13 As shown in e, when the electrolyte was switched from H2O to D2O, the peak position of Ru1 / PNC shifted significantly by 51 mV, indicating that the rate-determining step was an intermediate product. The desorption (i.e., the Heyrovsky step) is consistent with the KIE results. Meanwhile, the H... upd The displacement is negligible, indicating that both are prone to occur. Desorption. In addition, CO dissolution experiments are used to investigate... A powerful probe for adsorption capacity, exhibiting a more negative CO oxidation peak potential of 0.628V for Ru / C, indicating it is the strongest. Adsorption hindered its HER performance. Unlike Ru nanoparticles, the CO oxidation peak potential of Ru1 / PNC and Ru1 / NC catalysts showed a significant positive shift, indicating that the adsorption around the Ru single atom hindered its HER performance. The weak adsorption of OH* accelerates the reaction. Therefore, based on the above results, we can conclude that for Ru1 / NC, the rate-determining step of the basic hydrogen evolution reaction is the dissociation of H2O, while for Ru1 / PNC, it is... H* desorption.

[0113] To investigate the reaction behavior of Ru1 / PNC and Ru1 / NC in detail, operational electrochemical impedance spectroscopy (EIS) was performed in the overpotential range of 0–50 mV. Figure 13 As shown in g, the Bode plot corresponding to Ru1 / NC is at low frequencies (<10). 0 A significant peak appeared near 10 Hz, which is related to the Volmer step. In contrast, in the Ru1 / PNC system, the phase angle decreased rapidly in the low-frequency region as the applied potential increased; however, it remained constant in the mid-frequency region (10 Hz). 0 ~10 2 The slow decrease in the (Hz) phase angle indicates that the Heyrovsky step is relatively slow. This provides strong evidence that the rate-determining step can switch from the Volmer step to the Heyrovsky step after the introduction of the bifunctional Ru-P pair, thus explaining why Ru1 / PNC has better catalytic performance.

[0114] Lewis's bifunctional nature and multifunctionality The above results indicate that the basic hydrogen evolution reaction (HER) activity is significantly enhanced when P replaces one N atom in Ru1-N4 to form the Ru1-N3P1 structure. To reveal the intrinsic source of the significant HER performance on Ru1-N3P1, comprehensive theoretical calculations and experiments were performed. First, the models of Ru1-N3P1 and Ru1-N4 were optimized using DFT to provide insights into their electronic properties. Charge density difference and Bader charge analysis of Ru1-N4 showed that 0.24e is transferred from the Ru center to each surrounding N atom, resulting in a more positive Ru center and a negative N atom, which can act as Lewis acid (LA) and Lewis base (LB) sites, respectively. Conversely, when a coordinating N atom in the Ru1-N4 structure is replaced by P to form the Ru1-N3P1 structure, the adjacent P will transfer 0.34e to the Ru center, resulting in Ru being relatively electron-rich and P relatively electron-poor relative to the Ru-N pair, thus playing a bifunctional role as both LB and LA sites. Figure 22 a in Figure 22 (b) Furthermore, the charge redistribution induced by the asymmetric Ru1-N3P1 portion may play an indispensable role in promoting the dissociation of water.

[0115] Subsequently, temperature-programmed desorption (TPD) experiments with NH3 and CO2 were used to directly determine the acidity / basicity of Ru1 / PNC and Ru1 / NC. Figure 22 c in Figure 22 (d) From the NH3-TPD spectrum, it can be seen that the PNC vector shows two peaks at 99 and 145 °C, while the NC vector shows no response. This indicates that the signal in PNC originates from the introduced P species (d). Figure 22 (c) In contrast, Ru1 / NC exhibits a main peak at 110 °C, which can be attributed to the acidic Ru site. Similarly, a peak in Ru1 / PNC shifts to a higher temperature of 214 °C, attributed to the interaction of the Ru-P pair, resulting in stronger acidity. The acidity of Ru1 / PNC and Ru1 / NC was also confirmed by Fourier transform infrared (FTIR) spectroscopy using pyridine as a probe molecule, indicating that they possess Lewis acid properties. Figure 23 Furthermore, from the CO2-TPD spectra, the peaks near 84-87 °C in all samples can be attributed to basic N species; no other significant peaks were detected in the NC and PNC frameworks. However, after embedding Ru metal into NC, a new CO2 peak appeared in Ru1 / NC at 196 °C. 2-The desorption peak is attributed to the increased basicity of the coordinated N atom due to electron transfer from Ru to N. The introduction of a single Ru atom also produces a new peak at 243 °C in Ru1 / PNC, indicating the fundamental nature of the Ru site. Notably, according to Bader charge analysis, the electronic state of the neighboring N atom in Ru1 / PNC is almost unchanged compared to Ru1 / NC, ruling out the possibility that the peak at 243 °C is induced by a basic N species.

[0116] To demonstrate the bifunctional advantage of Ru-P Lewis pairs in the basic hydrogen evolution reaction, a series of site poisoning experiments were subsequently conducted, in which Ru-P acid-base pairs could be affected by thiourea and boric acid (…). Figure 22 e and appendix Figure 24 Effective blocking. First, thiourea molecules (LB) were intentionally added to the reaction system as a Lewis base. Therefore, Ru1 / PNC at 10 mA·cm -2 The overpotential increased sharply by 118 mV compared to the original activity, indicating that the Lewis acid site is essential for HER. Simultaneously, we selected boric acid (LA) as the Lewis acid to poison the Ru-basic site, resulting in a 24 mV increase in overpotential. Furthermore, the Ru1 / PNC catalyst was almost deactivated when both poisoning molecules were added simultaneously. These control experiments highlight the crucial role of bifunctional Ru-P Lewis acid pairs in the efficient basic hydrogen evolution reaction. Subsequently, to better validate the concept of Lewis acid-base pairs, we extended and evaluated the HER performance of two classes of Lewis acid-base pairs (MS / P / Cr and MN / B pairs). XRD patterns, TEM elemental mapping, and FT-EXAFS spectroscopy confirmed the uniformly dispersed metal centers and coordination environment. The HER performance of these two classes of Lewis acid-base pairs fell into two regions (following the order MP / S / Cr >> MN / B), confirming that the reaction rate is determined by the Lewis acid-base pair (MS / P / Cr >> MN / B). Figure 22 The properties of f) dominate. In particular, we believe that the bifunctional catalysts possess Lewis acid pair properties, where metallic Pt / Ru acts as the Lewis acid base and the oxyphilic Cr / Ce single atom acts as the Lewis acid acid; this demonstrates the unity and universality of our proposed concept. Therefore, to further improve the activity of commercial catalysts, we attempted to introduce a Lewis acid doping strategy into the modification of Ru / C and Pt / C. As a result, the average current densities of P-doped Ru / C and P-doped Pt / C are 2.74 times and 1.69 times that of the corresponding unmodified catalysts, respectively, demonstrating the effectiveness of the proposed bifunctional Lewis pair (f) Figure 4 The practicality of ).

[0117] Theoretical research and AEM batteries To clarify the effect of bifunctional Lewis acids and bases on the activity of water electrolysis, DFT calculations were performed. As representative examples, this application investigated two well-defined models: Ru1-N4 (Comparative Example 1) and Ru1-N3P1 (Example 1). We first analyzed that the d-band center of the Ru1-N3P1 structure is closer to the Fermi level than that of Ru1-N4, resulting in efficient dissociation of H2O. In fact, the activity of the basic hydrogen evolution reaction mainly depends on the proton production rate of the H2O dissociation step. Therefore, this application further investigated the dissociation pathway of H2O based on the above two models. The free energy curves ( Figure 25 As shown in a), the Ru1-N4 structure needs to overcome a high energy barrier of 1.13 eV to cause H2O to dissociate and form an endothermic 0.48 eV structure. and intermediates, which can be attributed to / In Ru-N pairs ( Figure 25 Weak adsorption on (a, blue) in the medium. The corresponding intermediate. and H2 can be readily desorbed to form H2. In contrast, due to the synergistic effect of the Ru-P pair, the energy barrier for the dissociation of H2O on the Ru1-N3P1 structure is reduced to 0.4 eV. Figure 25 (The 'a' in red). Interestingly, The formation of the intermediate is oriented towards the P Lewis acid atom, which can be considered the oxyphilic site previously reported in the literature; this indicates that the bifunctional composition is essential for the dissociation of H₂O. However, according to the Brønsted–Evans–Polanyi relation, the activation barrier for the dissociation of H₂O on the Ru-P pair is low, leading to... / The intermediate adsorption is strong, leading to the generation of H2 via the Heyrovsky step, consistent with experimental results. In summary, the different reaction energies of Ru1-N4 and Ru1-N3P1 are attributed to their unique electronic structures. The presence of the Ru-P pair significantly lowers the dissociation energy of H2O compared to the Ru-N pair, thus shifting the rate-determining step from the Volmer step to the Heyrovsky step. In other words, the overall HER rate can, in principle, be optimized by improving the Lewis properties of the active sites required for H2O dissociation, and... / Controlled by the desorption of intermediates.

[0118] Then, in-situ FTIR spectroscopy was performed to verify the enhanced H2O dissociation ability on Ru1 / PNC. Figure 25 (b) It is worth noting that when the applied potential is no higher than 0.9V, almost no signal appears, ruling out interference from H2O molecules in the electrolyte. However, once the applied potential can drive HER, in A potential-related signal was observed nearby, which could be further assigned to three deconvolution peaks located at... , and .generally, and This belongs to the strong vibration of the OH oscillator of the H2O molecule involved in the tetrahedral and trihedral coordination of HER, while These are inert dangling OH bonds in the H2O molecules at the interface. Therefore, as the applied potential increases, the Ru1 / PNC... and The sharp increase in peak proportion indicates a more efficient ability to split water. These results provide direct evidence that bifunctional SACs make a significant contribution to the basic hydrogen evolution reaction.

[0119] To further evaluate the application potential of the proposed bifunctional Lewis acid-base pair in water electrolysis, this application further assembled an AEM cell with a self-made IrRuOx catalyst as the anode, in 1.0 M KOH electrolyte, at 60 °C. Figure 25 Run under condition d). Figure 25 As shown in c, the current density of Ru1 / PNC reaches 1.0 and 2.0 Acm at battery voltages of 1.94 and 2.28V (without internal resistance compensation), respectively. -2 It outperforms the Ru1 / NC and Pt / C cathodes in the same reaction system. In stability tests, the Ru1 / PNC catalyst showed better performance at 2.0 A·cm⁻¹. -2 It exhibits excellent durability at high current densities, with an average decay rate of 0.08 mV·h over 266 hours. -1 ( Figure 25 (d) Furthermore, during this stable operation period, the corresponding specific activity and conversion number reached as high as 1.86 × 10⁴ AgRu⁻¹ and ~10⁸, respectively. In contrast, commercial Pt / C exhibited unsatisfactory performance, with high cell voltage and degradation rate (22 mV·h). -1 This demonstrates the crucial role of the bifunctional component in the alkaline hydrogen evolution reaction. Furthermore, compared to catalysts reported in AEM cells, Ru1 / PNC exhibits higher current density (…). Figure 25 The Ru1 / PNC catalyst exhibits excellent tolerance under (e) conditions, demonstrating the industrial potential of the proposed bifunctional Lewis pair. TEM, EDS, and ACHAADF-STEM were used to monitor the Ru1 / PNC catalyst under (e) conditions. Figure 25 (d) Compositional and structural evolution after long-term durability testing. Therefore, all elements are uniformly dispersed in the carbon matrix, and the Ru species remains in a single-atom state, indicating its structural stability. This is due to the strong electronic coupling of the Ru-P pair, which effectively suppresses the aggregation and shedding of active sites under harsh AEM conditions.

[0120] This application establishes a series of well-defined single-atom catalysts to reveal the bifunctional mechanism in the basic hydrogen evolution reaction (HER), where the dominant metal center and auxiliary coordinating atoms create abundant atom pairs endowed with Lewis acid-base properties. Importantly, these unique atom pairs can be tuned to produce efficient dissociation of H₂O by modulating their Lewis acid-base properties, shifting the rate-determining step of the basic HER from the Volmer step (with a higher Tafel slope of 97136 mV·dec) to the efficient dissociation of H₂O. -1 Switch to the Heyrovsky step (lower Tafel slope 3952mV·dec) -1 This significantly enhances catalytic performance. Experimental results and DFT calculations indicate that the preferential activity originates from the synergistic effect between the Lewis alkali metal center (Ru, Pt, Ir) and the Lewis acid coordinating atoms (P, S, Cr), clearly supporting a bifunctional mechanism through the use of well-defined single-atom sites. Furthermore, the representative Ru-P Lewis pair exhibits high activity at current densities up to 2 Acm⁻¹. -2 Exhibiting a durability of 266 hours without degradation, this strategy has been successfully extended to modifying commercial Pt / C and Ru / C catalysts. This application not only highlights the crucial role of bifunctional components in the alkaline hydrogen evolution reaction (HER), providing a catalyst capable of efficiently catalyzing the HER, but also offers a new perspective for designing advanced catalysts to enhance activity in water electrolysis and other catalytic applications.

[0121] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A composite coordination single-atom catalyst, characterized in that, The support includes a metal center, and at least two of the auxiliary coordinating atoms are coupled with the metal center to form a catalytically active center; wherein the metal center includes a single-atom metal center, and the auxiliary coordinating atoms include at least two of C, N, P, S, and Cr.

2. The composite coordination single-atom catalyst as described in claim 1, characterized in that, The metallic element at the metal center includes at least one of Ru, Pt, and Ir.

3. The composite coordination single-atom catalyst as described in claim 2, characterized in that, The metal element at the metal center accounts for 0.5 wt.% to 10 wt.% of the mass of the composite coordination single-atom catalyst; and / or The auxiliary coordinating atom includes the element P, and the content of the element P is greater than or equal to 0 and less than or equal to 10 wt.%. and / or The auxiliary coordinating atoms include P and N, and the molar ratio of P to N in the composite coordination single-atom catalyst is greater than 0 and less than or equal to 4.

4. The composite coordination single-atom catalyst according to any one of claims 2-3, characterized in that, The metal center is Ru, and the auxiliary coordinating atoms include N and P. One metal center is coupled with three N atoms and one P atom.

5. The composite coordination single-atom catalyst according to any one of claims 1-3, characterized in that, The specific surface area of ​​the composite coordination single-atom catalyst is 100–2000 m². 2 / g; and / or The composite coordination single-atom catalyst comprises a layered structure; and / or The support for the composite coordination single-atom catalyst includes carbon materials.

6. The method for preparing the composite coordination single-atom catalyst according to any one of claims 1-5, characterized in that, Includes the following steps: The carrier material and the metal source are subjected to a first mixing process to obtain a first mixture; The first mixture was subjected to a first heat treatment to obtain the composite coordination single-atom catalyst; The carrier material is doped with elements that assist coordination atoms, and the metal source contains a metal element with a metal center.

7. The preparation method according to claim 6, characterized in that, The metal source includes RuCl3; and / or The temperature of the first heat treatment is 700–1000°C; The first heat treatment lasts for 1 to 3 hours; and / or The first heat treatment is performed under a protective atmosphere.

8. The preparation method according to claim 6 or 7, characterized in that, The first mixing process includes the following steps: The metal source is dissolved in water to obtain a metal solution; The carrier material is dispersed in water to obtain a carrier material slurry; The carrier material slurry is mixed with the metal solution to obtain a mixed slurry; The mixed slurry is dried to obtain the first mixture.

9. The preparation method according to claim 6 or 7, characterized in that, The preparation of the carrier material includes the following steps: The carbon source and the dopant element source are mixed to obtain the precursor of the carrier material; The carrier material precursor is subjected to heat carbonization treatment to obtain the carrier material; The carbon source includes at least one of melamine, cyanuric acid, and alanine. The doping element source includes at least one of N source, P source, S source, and Cr source; the nitrogen source includes at least one of melamine, cyanuric acid, and L-alanine; and the phosphorus source includes phytic acid. The temperature for the heating and carbonization treatment is 400–600°C; The heating and carbonization treatment takes 1 to 5 hours.

10. A method for preparing a composite coordination single-atom catalyst as described in any one of claims 1-5, characterized in that: A second mixture is obtained by mixing a metal catalyst containing a metal center metal element with a doped element source. The second mixture is subjected to a second heat treatment to obtain the composite coordination single-atom catalyst.

11. The preparation method according to claim 10, characterized in that, The metal catalyst includes at least one of Pt / C catalyst and Ru / C catalyst; and / or The doping element source includes at least one of P source, N source, S source and Cr source, wherein the P source includes NaH2PO2·H2O, the N source includes melamine, the S source includes thiourea, and the Cr source includes Cr(NO3)3·9H2O; and / or The mass ratio of the metal catalyst to the dopant source is 1:1 to 1:20; and / or The second heat treatment is performed under a protective atmosphere; and / or The temperature of the second heat treatment is 250–600°C; and / or The second heat treatment lasts for 1 to 5 hours.

12. The application of the composite coordination single-atom catalyst as described in any one of claims 1-5 or the composite coordination single-atom catalyst prepared by the composite catalysis method as described in any one of claims 6-11 in the electrolysis of water.

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