High-entropy conjugated coordination polymer aerogel material as well as preparation method and application thereof

Abstract

The invention discloses high-entropy conjugated coordination polymer aerogel as well as preparation and application thereof. The material is constructed by coordination of at least five metal elements M and a conjugated ligand L, and three-dimensional porous aerogel is obtained through sol-gel gelling, solvent exchange and drying (preferably supercritical). M is selected from Fe, Co, Ni, Cu, Zn and Mn (Al and Bi can be contained), and the metal atom ratio is nearly equal friction (preferably deviation is smaller than or equal to + / -10%); l is selected from HHTP, HHB, HATP or HAB. The method comprises the following steps: mixing a metal salt aqueous solution A and a ligand organic solution B, heating at 65-85 DEG C for 24-48 hours to form gel, and drying to form the material. The material is large in specific surface area, rich in monatomic sites and high in mass transfer rate, can be used for water electrolysis oxygen evolution in alkaline electrolyte, and shows low overpotential and high-quality activity.

Description

Technical Field

[0001] This invention belongs to the field of high-entropy conjugated coordination polymer materials technology, and particularly relates to high-entropy conjugated coordination polymer aerogel materials, their preparation methods, and their application in the oxygen evolution reaction of water electrolysis. Background Technology

[0002] In the field of electrocatalysis and new energy materials, the focus is on the oxygen evolution reaction (OER) in devices such as water electrolysis, metal-air batteries and renewable fuel cells. The evaluation of these materials is mainly based on indicators such as overpotential, current density-potential relationship, Tafel slope, mass activity and durability.

[0003] The closest existing technologies include catalytic systems represented by noble metal oxides such as IrO2 and RuO2. This route is of reference value in terms of activity and onset potential, but its large-scale application is constrained by the scarcity and high cost of raw materials. Furthermore, the structural and compositional stability under long-term polarization and complex electrolysis environments, particularly under strong alkaline / high-potential conditions, remains insufficient. In addition, there are publicly disclosed technical routes using multi-metal coordination polymers for OER, but differences remain in ligand types, molding and drying methods, and morphology control, and the related engineering constraints have not been fundamentally resolved.

[0004] As an alternative, non-precious metal systems (such as transition metal-based oxides / hydroxides, phosphides, sulfides, etc.) improve the adsorption / desorption process by regulating the valence state and electronic structure, thereby reducing the overpotential at the target current density. Another approach is to improve reactant transport and gas evolution behavior by introducing porous, lightweight frameworks and macro / meso / micro multi-level porous structures, aiming to improve specific activity and utilization at lower loading levels.

[0005] However, the above-mentioned routes still have common shortcomings in key indicators and engineering constraints: First, OER is a multi-step four-electron transfer process (involving proton-electron coupling), which is kineticly slow and often results in speeds below 10 mA·cm⁻¹. -² First, the overpotential at the reference current density is too high and the Tafel slope is too large, limiting the electrode efficiency. Second, the structural and compositional stability of non-noble metal catalysts is insufficient under strong base and high potential conditions, and the active sites may dissolve / reconstruct, leading to performance degradation. Third, there is a contradiction between the density and accessibility of active sites at the material level. Although porous structures are beneficial for mass transfer, they are prone to diffusion and electron transport bottlenecks in actual electrodes due to binders, carrier contact, and pore collapse. Fourth, large-scale synthesis and batch-to-batch consistency are easily affected by the precursor ratio, sol-gel and drying path window control, resulting in large performance dispersion.

[0006] Against this background, there is a need in the field to construct a catalytic material system suitable for alkaline OERs, taking into account both cost and availability, so that it simultaneously possesses high active site density, effective electron / ion transport channels and long-term structural stability, and achieves low overpotential and high quality activity under representative operating conditions, while forming a replicable and scalable process window and evaluation criteria. Summary of the Invention

[0007] The technical problem to be solved is that, in the oxygen evolution reaction (OER) under alkaline conditions, noble metal catalysts are limited by cost and resource availability; existing non-noble metal systems still have room for improvement in terms of site utilization, overpotential at reference current density, long-term stability, and batch-to-batch consistency. This invention aims to construct an electrocatalytic material system with high active site density, effective mass transfer channels, and a robust framework, while maintaining availability and low cost, and to establish a reproducible synthesis window and a unified evaluation standard.

[0008] First aspect of the invention: Product (material) A high-entropy conjugated coordination polymer aerogel material is provided. The material consists of a three-dimensional porous network constructed by coordination of at least five different metal elements M with conjugated organic ligands L, and exhibits an aerogel morphology; wherein: M is selected from the combination of elements Fe, Co, Ni, Cu, Zn, Mn, Al, and Bi, and the atomic ratio of each metal element is close to equimolar, preferably deviating from equimolar by no more than ±10%; L is selected from at least one of 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP), hexahydroxybenzene (HHB), 2,3,6,7,10,11-hexaaminotriphenyl (HATP), and hexaaminobenzene (HAB); The material preferably has a three-dimensional network morphology with both micropores and / or mesopores; preferably, the metal is dispersed in the form of single atoms and no metal coordination peaks appear in the X-ray absorption fine structure spectrum.

[0009] Second aspect of the invention: Method (preparation) The material can be obtained through the following sol-gel + drying process: (1) Dissolve at least five metal salts of the metals in water to obtain solution A; (2) Dissolve the conjugated organic ligand in an organic solvent to obtain solution B; (3) Mix solution A and solution B, heat at 65-85℃ for 24-48h, and obtain wet gel through sol-gel process; (4) After solvent exchange, the wet gel is dried by at least one of atmospheric pressure drying, freeze drying or supercritical drying to obtain a high-entropy conjugated coordination polymer aerogel material.

[0010] Preferably, the metal salt is one or more of chloride, acetate, sulfate, or nitrate, with acetate being preferred; the molar ratio of each metal salt in solution A is 1:1:1:1:1; and the concentration of solution A is 0.5–1.0 mol·L⁻¹. -¹ The concentration of solution B is 0.2–0.8 mol·L⁻¹. -¹ The organic solvent is one or more of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), or acetone, with DMSO being preferred; the drying method is preferably supercritical drying. These preferred methods do not alter the boundaries of the independent technical solutions and are used to improve the continuity of the gel skeleton and the reproducibility of the preparation.

[0011] Third aspect of the invention: Uses (applications) The material is used for oxygen evolution catalysis in alkaline media, particularly for oxygen production via water electrolysis. In OER evaluation, a three-electrode system with 1 mol·L⁻¹ was used. -1 KOH electrolyte was used for LSV and other tests under a uniform iR compensation caliber; current density was normalized according to geometric area, and mass activity was normalized according to catalyst loading.

[0012] Beneficial effects The present invention has the following advantages over the prior art: (1) By co-constructing near-isomolar (±10%) metals with conjugated ligands, the electronic structure of metal ligands was modulated at a reference current density of 10 mA·cm⁻¹. -² A lower overpotential was obtained; under uniform test conditions, the overpotential of the representative sample was 155mV (see...). Figure 6 The near-isomolar composition was confirmed by ICP-OES data (see Table 1), and this was corroborated by the absence of metal coordination peaks observed in X-ray absorption fine structure (XAS) (see Table 1). Figure 5 ) (2) The material has a three-dimensional porous aerogel framework, which is conducive to reactant transport and gas evolution and reduces mass transfer resistance; it exhibits high mass activity at an overpotential of 300mV, with a representative sample having an activity of 146mA·mg. - ¹(see) Figure 7 ).

[0013] (3) Single-atom dispersion characteristics: XAS showed significant metal-oxygen coordination peaks, but no metal-metal coordination peaks were observed, indicating that the metal was dispersed in single-atom form (see Figure 5 Combined with the elemental content results in Table 1, this supports the structural characteristics of "near-isomolar + single atom".

[0014] (4) Clear process window: The concentration of solution A / B, gelation temperature / time, solvent exchange and drying path are clearly defined, which facilitates batch preparation and cross-batch consistency control (corresponding to specific implementation methods).

[0015] The aforementioned performance and structural evidence was obtained through examples and comparative studies under a unified testing caliber, as detailed in [link to relevant documentation]. Figure 1 – Figure 7 See Table 1. Attached Figure Description

[0016] Figure 1 Schematic diagrams of the local structures of high-entropy conjugated coordination polymer aerogels and low-entropy aerogels (see abstract figures).

[0017] Figure 2 Photographs of the material state after the reaction of the samples in Example 1 and Comparative Example 6.

[0018] Figure 3 Scanning electron microscope images of the samples from Example 1 and Comparative Example 6.

[0019] Figure 4 Transmission electron microscope image of the elemental distribution of the sample in Example 1.

[0020] Figure 5 X-ray absorption spectrum of the sample in Example 1.

[0021] Figure 6 Samples from Example 1, Comparative Examples 1-5, and Comparative Example 6 were tested at 1 mol·L⁻¹ -1 Linear sweep voltammetry curves in KOH.

[0022] Figure 7 Samples from Example 1, Comparative Examples 1-5, and Comparative Example 6 were tested at 1 mol·L⁻¹ -1 Comparison chart of mass activity in KOH. Detailed Implementation

[0023] Terminology Explanation 1. Solution A / Solution B: Solution A refers to an aqueous solution of a metal salt; Solution B refers to an organic solution of a conjugated organic ligand. All ratios and concentrations appearing in this document are based on this naming convention.

[0024] 2. Concentration and Units: All solution concentrations in this document are expressed in mol·L⁻¹. -¹ Indicate (specify the number of moles and volume if necessary).

[0025] 3. High Entropy and Near-Isomolarity: "High entropy" refers to a system containing ≥5 metallic elements. Near-isomolarity criterion: For a sample containing N (≥5) metallic elements, the theoretical isomolarity value is 100 / N at / %; if the measured atomic fraction at / % of each metal satisfies... If the value is within ±10% of the theoretical value, it is considered "near-isomolar". For example, when N=5, the theoretical value is 20 at / %, and the allowable range is 18.0–22.0 at / %. The elemental content is determined by ICPOES / ICP-OES / ICP-MS and the conversion method is given in the instruction manual.

[0026] 4. Aerogel: refers to a three-dimensional porous network solid obtained by sol-gel formation and subsequent drying (preferably supercritical drying).

[0027] 5. XAS / EXAFS Criterion (Single Atom Dispersion): X-ray Absorption Fine Structure (EXAFS, k...) ³ In weighted (R-space), if only metal-coordination (e.g., M–O, M–N) signals are observed without a significant metal-metal (M–M) first coordination shell peak, this can be used as structural evidence that the metal is dispersed as single atoms. Data processing methods and reference samples are specified in the methodology section of the instruction manual.

[0028] 6. OER test caliber: - System: Three-electrode system, electrolyte 1.0 mol·L⁻¹ -¹ KOH, room temperature (25 ± 2 ℃); reference electrode labeled and converted to RHE.

[0029] - Potential converted to RHE: E(RHE) = E(Hg / HgO) + 0.098 + 0.059·pH (1.0 mol·L⁻¹) -¹ The voltage at KOH is approximately 0.91–0.92 V. All samples were tested under the same iR compensation aperture (95%) and scan parameters.

[0030] - iR compensation: After measuring the solution resistance Rᵤ, 95% iR compensation is applied (the compensation ratio and Rᵤ are noted in the figure caption).

[0031] - LSV scan rate: 5 mV·s (default) - ¹; Current density normalized according to geometric area (mA·cm) -² Mass activity is normalized according to the net catalyst loading (mA·mg) -¹ ).

[0032] - Repeatability: Key data (e.g., η@10 mA·cm) -² (Metal activity) It is recommended that n≥3 and given as mean ± standard deviation.

[0033] General preparation process Solution A: At least five metal salts (preferably acetates) dissolved in water (0.5–1.0 mol·L⁻¹)-¹ Solution B: Ligands (such as HHTP) dissolved in DMSO (0.2–0.8 mol·L⁻¹). -¹ After mixing A and B at room temperature, the mixture was kept at 75°C for 24 hours to form a gel. Following solvent exchange, supercritical drying was used to obtain an aerogel. The preferred metal molar ratio was 1:1:1:1:1 (near isomolar ± 10%). Examples 1-3 Example 1: Preparation of high-entropy conjugated coordination polymer aerogel materials Solution A was prepared by dissolving 26.1 mg (0.15 mmol) ferric acetate, 37.4 mg (0.15 mmol) cobalt acetate tetrahydrate, 37.3 mg (0.15 mmol) nickel acetate tetrahydrate, 29.9 mg (0.15 mmol) copper acetate monohydrate, and 32.9 mg (0.15 mmol) zinc acetate dihydrate in 1.0 mL of deionized water. Solution B was prepared by dissolving 162 mg (0.50 mmol) of 2,3,6,7,10,11 hexahydroxytriphenyl in 1.0 mL of dimethyl sulfoxide and ultrasonically dispersed for 1 h. Solution A and solution B were mixed in a glass bottle and incubated in a 75 °C oven for 24 h to obtain a wet gel. After solvent exchange, the gel was dried using supercritical fluid to obtain a high-entropy conjugated coordination polymer aerogel material.

[0034] Example 2: Preparation of high-entropy conjugated coordination polymer aerogel materials Solution A was prepared by dissolving 36.8 mg (0.15 mmol) manganese acetate tetrahydrate, 26.1 mg (0.15 mmol) ferric acetate, 37.4 mg (0.15 mmol) cobalt acetate tetrahydrate, 37.3 mg (0.15 mmol) nickel acetate tetrahydrate, and 29.9 mg (0.15 mmol) copper acetate monohydrate in 1.0 mL of deionized water. Solution B was prepared by dissolving 162 mg (0.50 mmol) of 2,3,6,7,10,11 hexahydroxytriphenyl in 1.0 mL of dimethyl sulfoxide and ultrasonically dispersing for 1 h. The mixture was then incubated at 75 °C for 24 h to obtain a wet gel. After solvent exchange, the target material was obtained by supercritical drying.

[0035] Example 3: Preparation of high-entropy conjugated coordination polymer aerogel materials Solution A was prepared by dissolving 49.0 mg (0.20 mmol) manganese acetate tetrahydrate, 34.8 mg (0.20 mmol) ferric acetate, 49.9 mg (0.20 mmol) cobalt acetate tetrahydrate, 49.7 mg (0.20 mmol) nickel acetate tetrahydrate, and 39.9 mg (0.20 mmol) copper acetate monohydrate in 1.0 mL of deionized water. Solution B was prepared by dissolving 226.8 mg (0.70 mmol) of 2,3,6,7,10,11-hexahydroxytriphenyl in 1.0 mL of dimethyl sulfoxide and ultrasonically dispersing for 1 h. The mixture was then incubated at 75 °C for 24 h to obtain a wet gel; after solvent exchange, the target material was obtained by supercritical drying.

[0036] Comparative Examples 1-6 Comparative Example 1 (Low-entropy aerogel) Solution A was prepared by dissolving 130 mg (0.75 mmol) of ferric acetate in 1.0 mL of water; Solution B was prepared in the same manner as in Example 1. The mixing, heating, and drying steps were the same as in Example 1 to obtain a low-entropy conjugated coordination polymer aerogel material.

[0037] Comparative Example 2 (Low-entropy aerogel) Solution A was prepared using only 187.1 mg (0.75 mmol) of cobalt acetate tetrahydrate; the remaining steps were the same as in Example 1.

[0038] Comparative Example 3 (Low-entropy aerogel) Solution A was prepared using only 186.4 mg (0.75 mmol) of nickel acetate tetrahydrate; the remaining steps were the same as in Example 1.

[0039] Comparative Example 4 (Low-entropy aerogel) Solution A was prepared using only 149.6 mg (0.75 mmol) of copper acetate monohydrate; the remaining steps were the same as in Example 1.

[0040] Comparative Example 5 (Low-entropy aerogel) Solution A was prepared using only 164.5 mg (0.75 mmol) of zinc acetate dihydrate; the remaining steps were the same as in Example 1.

[0041] Comparative Example 6 (Non-aerogel control) Solution A was prepared by dissolving 7.96 mg of ferric acetate, 37.4 mg of cobalt acetate tetrahydrate, 7.96 mg of nickel acetate tetrahydrate, 29.9 mg of copper acetate monohydrate, and 32.9 mg of zinc acetate dihydrate in 2.0 mL of deionized water; Solution B was prepared by dissolving 51.84 mg of 2,3,6,7,10,11-hexahydroxytriphenyl in 2.0 mL of dimethyl sulfoxide. The solutions were ultrasonically dispersed for 1 h and then mixed. The mixture was incubated at 75 ℃ for 24 h to obtain a high-entropy conjugated coordination polymer. After washing, centrifugation, and supercritical drying, a high-entropy conjugated coordination polymer material (non-aerogel) was obtained.

[0042] Experimental Example: Performance Testing of High-Entropy Conjugated Coordination Polymer Aerogel Materials Testing and Characterization Methods Unless otherwise specified, oxygen evolution performance is evaluated using a three-electrode system in an alkaline electrolyte; the electrolyte is 1 mol·L⁻¹. -¹ KOH; current density is normalized to geometric area, and mass activity is normalized to catalyst loading; parameters such as iR compensation or scan rate are explained in the corresponding figure captions. Morphological and structural characterization includes SEM / TEM, XAS, and ICP-OES, and the figure numbers and corresponding relationships are given below. The experimental method is consistent with the aforementioned examples.

[0043] Test results (1) Morphology and gelation state Figure 1 This is a partial structural schematic diagram of Example 1 and Comparative Example 1.

[0044] Figure 2 The material states of Example 1 and Comparative Example 6 after reaction under the same heating conditions are shown: Example 1 is in a gel state, and Comparative Example 6 is in a solution state.

[0045] Figure 3 SEM images of Example 1 and Comparative Example 6: Example 1 exhibits a loose and porous aerogel morphology. Compared with the non-aerogel sample, the aggregation phenomenon is reduced, which is beneficial to reactant contact and site exposure.

[0046] (2) Element distribution and coordination environment Figure 4 The TEM elemental distribution diagram of the sample in Example 1 shows that the five metal elements are evenly distributed.

[0047] Figure 5 XAS of the sample from Example 1: Metal-oxygen coordination correlation peaks were observed, but no metal-metal coordination peaks were seen, indicating that the metal was dispersed in the form of single atoms.

[0048] Table 1 shows the ICP OES results of Example 1: the contents of the five metals are close, which meets the near-isomolar design criterion.

[0049] Table 1. ICP OES Content of Five Metals in Example 1 and Near-Isomolarity Criterion Note: ICP OES quantification is performed using the external standard method; n≥3 for each sample, data are expressed as x̄ ± s. Near isomolarity is determined based on the following formula, converting w / % to atomic fraction at / %: Where Mi is the atomic weight of the element; when the deviation of each element's at / % from the relative isomolarity (20%) is ≤±10%, it is considered 'near isomolarity'. The above data corresponds to the elemental content results in Table 1. The above descriptions are factual statements regarding the existing charts and data.

[0050] (3) Comparison of OER activity (1 mol·L) -¹ KOH) Figure 6 (LSV): Example 1 at 10 mA·cm -² The overpotential of Example 1 was 155 mV; the overpotentials of Comparative Examples 1–5 (low-entropy aerogel) and Comparative Example 6 (non-aerogel) were 270, 268, 214, 340, 267, and 271 mV, respectively. Under comparable conditions, the overpotential of Example 1 was lower.

[0051] Figure 7 (Mass activity): At an overpotential of 300 mV, the mass activity of Example 1 is 146 mA·mg. -¹ Comparative Examples 1–5 and Comparative Example 6 showed activity levels of 37, 42, 63, 7, 40, and 44 mA·mg⁻¹, respectively. Example 1 exhibited higher mass activity.

[0052] The above results indicate that, under the same evaluation criteria, the high-entropy + conjugated ligand system, after sol-gelation and aerogelation (preferably supercritical drying), yields materials that possess both lower overpotential and higher quality activity. No metal peaks were observed in XAS, and combined with the near-isomolar results from ICP-OES, the materials exhibit single-atom dispersion and near-isomolar multi-metallic structural characteristics, consistent with... Figure 6 / Figure 7 The electrochemical performance is consistent with that of the test results. The above description is used to objectively interpret the test results and does not constitute a limitation of the claims in this application.

[0053] The embodiments described in this specification are for illustrative purposes only and not for limiting purposes; unless otherwise stated, numerical ranges include endpoints, and the term "comprising / including" is non-exclusive. For those skilled in the art, any equivalent substitutions or modifications made without departing from the basic concept of this application shall be governed by the claims.

[0054] Industrial applicability The method is characterized by mild conditions, simple process, and friendly solvent and temperature windows, making it suitable for large-scale production. The resulting material has a stable structure and wide range of applications, and can be used in electrocatalytic scenarios such as water electrolysis for oxygen production.

Claims

1. A high-entropy conjugated coordination polymer aerogel material, characterized in that: A three-dimensional porous network consisting of coordination of at least five different metal elements M with conjugated organic ligands L, and in aerogel form; wherein: M is selected from at least five of Fe, Co, Ni, Cu, Zn, Mn, Al, Bi; L is selected from at least one of 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP), hexahydroxybenzene (HHB), 2,3,6,7,10,11-hexaaminotriphenyl (HATP), hexaaminobenzene (HAB); The atomic ratio of each metal element is close to equimolar, deviating from equimolar by no more than ±10%.

2. The material of claim 1, wherein M is composed of five elements of Fe, Co, Ni, Cu, Zn, and is close to equimolar.

3. The material of claim 1 or 2, wherein L is 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP).

4. The material of claim 1, wherein the material has a three-dimensional network morphology of micropores and / or mesopores.

5. The material of claim 1, wherein the metal is dispersed in the form of a single atom, and no metal-metal coordination peak appears in the X-ray absorption fine structure spectrum.

6. A method of making the material of any one of claims 1-5, characterized in that, Comprising: (1) dissolving metal salts of at least five of the metals in water to obtain solution A; (2) dissolving the conjugated organic ligand in an organic solvent to obtain solution B; (3) mixing solution A and solution B, heating at 65-85°C for 24-48h, and obtaining a wet gel through sol-gel; (4) after solvent exchange of the wet gel, drying by supercritical drying to obtain the aerogel material; wherein the total metal ion concentration of solution A is 0.5-1.0 mol L -¹ and the ligand concentration of solution B is 0.2-0.8 mol L -¹ .

7. The method of claim 6, wherein the metal salt is acetate, and the molar ratio of each metal salt in solution A is 1:1:1:1:1; the organic solvent is selected from one or more of dimethyl sulfoxide, N,N-dimethylformamide or acetone, preferably dimethyl sulfoxide; the gelation temperature is 75°C, and the gelation time is 24h.

8. Use of the material of any one of claims 1-5 as a catalyst for the oxygen evolution reaction (OER) of water electrolysis in alkaline medium.

9. The use according to claim 8, wherein the electrolyte is a 1 mol-L -¹ potassium hydroxide solution.

10. An electrode comprising an electrically conductive substrate and the material of any one of claims 1-5 supported thereon.

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