A method for improving performance stability of a ruthenium-based catalyst based on structure confinement effect

Abstract

The embodiment of the application relates to the technical field of inorganic material preparation, and particularly relates to a method for improving performance stability of a ruthenium-based catalyst based on structure confinement effect, which comprises the following steps: preparing lithium-doped binary hydroxide, calcining the lithium-doped binary hydroxide to obtain lithium-doped spinel oxide; calculating the concentration of nitro solution of tetrafluoroboric acid based on the lithium-doped amount and the delithiation ratio, delithiating the spinel oxide to obtain spinel oxide with a spatial confinement structure; dispersing the spinel oxide in a solution containing a ruthenium salt for reaction, determining a reaction equilibrium time by monitoring the change in electrical conductivity in real time; filtering, drying and calcining, determining the calcination time according to the change in electrical conductivity, and obtaining a ruthenium-based catalyst; the method constructs a spatial confinement vacancy through selective delithiation, guides ruthenium atoms to accurately occupy original lithium ion lattice sites, realizes confinement anchoring of ruthenium species at an atomic scale, and significantly improves the structural stability and catalytic durability of the catalyst in an acid oxygen evolution reaction.

Description

Technical Field

[0001] This application relates to the field of inorganic material preparation technology, and in particular to a method for improving the performance stability of ruthenium-based catalysts based on structural confinement effects. Background Technology

[0002] With the accelerated construction of my country's new power system, the scale of clean energy power generation such as wind and solar power is growing rapidly, and the problem of new energy consumption is becoming increasingly prominent. Hydrogen energy, as a green, low-carbon, and high-energy-density energy carrier, is receiving widespread attention. Among them, proton exchange membrane (PEM) water electrolysis hydrogen production technology is considered one of the most promising green hydrogen production technologies due to its advantages such as high hydrogen purity, small electrolyzer size, flexible operation, wide load range, high current density, and fast dynamic response speed. It can well match the randomness and volatility of new energy power generation and achieve zero carbon emissions throughout the entire chain.

[0003] The cathode and anode reactions of the PEM electrolytic cell are as follows: Cathode: 4H + +4e - →2H₂; Anode: 2H₂O→4H + +O2+4e - ; The working environment of the anode is extremely harsh, typically with a temperature of 60~80℃, pH≈2, and an electrolysis voltage of 1.4~2.0V, which places extremely high demands on the activity and stability of the anode catalyst.

[0004] Currently, the anode catalysts for PEM water electrolysis mainly use precious metal materials such as iridium and ruthenium. Iridium-based catalysts combine high catalytic activity with good stability, and are considered the most suitable anode materials for PEM water electrolysis technology. However, the global annual mining volume of iridium is only about 7 tons, making its scarcity and high cost severely restrict its large-scale application. In contrast, ruthenium-based catalysts have higher intrinsic catalytic activity, and the price of ruthenium is only 10% to 20% of that of iridium, which is expected to significantly reduce the manufacturing cost of PEM electrolyzers. However, ruthenium-based catalysts are prone to dissolution under strongly acidic conditions, leading to catalyst loss, decreased oxygen evolution reaction activity, insufficient stability, and short service life. Summary of the Invention

[0005] To address this, the present invention provides a method for improving the performance stability of ruthenium-based catalysts based on the structural confinement effect, thereby overcoming the problems in the prior art where ruthenium-based catalysts are prone to dissolution under strong acidic conditions, leading to catalyst loss, decreased oxygen evolution reaction activity, insufficient stability, and short service life.

[0006] To achieve the above objectives, this invention provides a method for improving the performance stability of ruthenium-based catalysts based on structural confinement effects. This includes: Step S1: Prepare lithium-doped binary hydroxide, and obtain lithium-doped spinel oxide by calcination; Step S2: Calculate the concentration of the tetrafluoroborate solution based on the lithium doping amount in the spinel oxide according to a preset delithiation ratio, disperse the lithium-doped spinel oxide in the tetrafluoroborate solution to react and delithiate, and obtain a spinel oxide with a spatially confined structure. Step S3: The spinel oxide with spatial confinement structure is dispersed in a ruthenium-containing salt solution for reaction. The conductivity of the reaction system is monitored in real time. The reaction equilibrium time is determined based on the change in the conductivity of the reaction system. When the rate of change in conductivity is lower than a set threshold, the reaction equilibrium is determined and the reaction product is obtained. Step S4: The reaction products are filtered, dried and transferred to a tube furnace for calcination. The calcination time is determined based on the change in the conductivity of the calcined products. The products are calcined for the specified time to obtain a ruthenium-based catalyst with a structural confinement effect.

[0007] Further, in step S2, the concentration of the tetrafluoroborate nitrate solution is calculated based on the lithium doping amount in the spinel oxide according to a preset delithiation ratio, including: Step S21: Determine the lithium content in the spinel oxide to determine the target lithium content to be removed; Step S22: Based on the target delithiation amount, establish the correlation between the concentration of tetrafluoroborate nitrate solution and the delithiation amount; Step S23: Based on the correlation and the characterization and detection of the delithiation products, select the lowest effective concentration of tetrafluoroborate nitrate solution that can achieve the target delithiation amount without damaging the framework structure.

[0008] Further, in step S23, based on the correlation and the characterization and detection of the delithiation products, the lowest effective concentration of the tetrafluoroborate nitrate solution that can achieve the target delithiation amount without damaging the framework structure is selected, including: Step S231: Based on the aforementioned correlation, design a tetrafluoroborate nitrate solution containing multiple concentration gradients, with each concentration gradient maintaining an equal or logarithmic interval distribution. Step S232: The spinel oxides prepared in the same batch are dispersed in tetrafluoroborate nitrate solutions of different concentration gradients and delithiation reaction is carried out under the same reaction conditions. After the reaction is completed, the products are subjected to solid-liquid separation, washing and drying. Step S233: Characterize and detect the delithiation products of each concentration gradient after drying. The characterization and detection include: determining the lithium content of each product using inductively coupled plasma atomic emission spectrometry, and determining whether the target delithiation amount has been reached based on the original lithium content and the remaining lithium content; and analyzing the integrity of the spinel framework structure of each product using X-ray diffraction to determine whether structural collapse or impurity phases have occurred. Step S234: Select the lowest concentration value from the concentration gradients that meet the following two conditions as the lowest effective concentration of the tetrafluoroborate nitrate solution: the actual delithiation amount reaches or exceeds the set threshold of the target delithiation amount, and no impurity peaks belonging to non-spinel phases appear in the X-ray diffraction pattern, and the full width at half maximum (FWHM) of the spinel characteristic diffraction peaks does not exceed the set threshold of the initial value.

[0009] Further, in step S3, determining the reaction equilibrium time based on the change in the conductivity of the reaction system includes: Step S31: Record the initial conductivity value at the start of the reaction, collect the conductivity data of the reaction system in real time at fixed time intervals, and calculate the rate of change of conductivity within the time interval. Step S32: When multiple consecutive conductivity change rates fluctuate within a preset threshold percentage range, the reaction is determined to have reached equilibrium. Step S33: Determine the reaction equilibrium time based on the moment when the equilibrium state is reached and the moment when the reaction begins.

[0010] Further, in step S32, determining that the reaction has reached an equilibrium state includes: Step S321: Set the equilibrium criterion parameters, including the conductivity change rate threshold and the continuous stable time window; Step S322: Calculate the rate of change of conductivity at the current sampling point in real time; Step S323: When the rate of change of conductivity first decreases below the set rate of change threshold, the timing of the continuous stable time window is started; Step S324: Within the continuous stable time window, continuously monitor the rate of change of conductivity at each sampling point. If the rate of change of conductivity at all sampling points remains below the set rate of change threshold within the window period, it is determined that the reaction has reached equilibrium. Step S325: If the rate of change of conductivity at any sampling point exceeds the set rate of change threshold during the continuous stable time window, the current timing is terminated and the window is reset. Timing is restarted when the rate of change of conductivity drops below the rate of change threshold again.

[0011] Furthermore, the lithium-doped binary hydroxide in step S1 is composed of two or more chemical elements in different valence states, one of which is a metal element including at least one of magnesium, nickel, chromium, zinc, manganese, etc.; the second metal element includes at least one of aluminum, iron, cobalt, manganese, etc.; and the amount of lithium doping is 1% to 99% of the molar amount of the metal element replacing the spinel.

[0012] Furthermore, in step S1, the calcination is carried out in an air atmosphere at a temperature of 600℃ to 1000℃.

[0013] Furthermore, in step S2, the solvent of the tetrafluoroborate nitrate solution is at least one of solvents such as ethanol, acetonitrile, dichloromethane, and nitromethane, and the amount of tetrafluoroborate nitrate used is 0.5 to 10 times the molar amount of spinel oxide.

[0014] Furthermore, in step S3, the reaction temperature is 25℃~100℃, and the reaction time is 1h~96h.

[0015] Further, in step S3, the molar ratio of spinel oxide to ruthenium salt is 0.01 to 1, and the ruthenium salt is selected from one or more of ruthenium chloride, ruthenium nitrate, ruthenium acetylacetonate, and nitrosyl ruthenium, and a solution is prepared by selecting an appropriate solvent according to the characteristics of the ruthenium precursor.

[0016] Further, in step S3, the spinel oxide with the spatially confined structure is dispersed in a ruthenium-containing salt solution for reaction, the reaction temperature is 25℃~60℃, the stirring speed is 100r / min~1000r / min, and the reaction time is 1h~96h.

[0017] Furthermore, the calcination in step S4 is carried out in an atmosphere of hydrogen, argon, nitrogen or a mixture thereof, at a temperature of 100℃ to 600℃, and for a time of 0.5h to 10h.

[0018] Furthermore, in step S31, the fluctuation range of the rate of change of conductivity within the sampling interval is 1% to 5%, and multiple consecutive time intervals refer to consecutive time periods divided into 3-minute intervals within a continuous time window of 5 to 20 minutes.

[0019] Furthermore, in the ruthenium-based catalyst with structural confinement effect described in step S4, the type of lattice sites occupied by ruthenium atoms is consistent with the initial occupancy sites of lithium ions in step S1.

[0020] Further, the preparation of lithium-doped binary hydroxide in step S1 adopts a co-precipitation method, specifically including: adding component A, which contains lithium salt, a first metal salt, and a second metal salt, and component B, which contains a precipitant, dropwise to component C of the reaction medium simultaneously; controlling the pH value within the range of 8.0 to 9.0 under stirring conditions to carry out the co-precipitation reaction; after the reaction is completed, centrifuging, washing to neutrality, and drying are performed to obtain lithium-doped binary hydroxide; the metal element in the first metal salt is selected from at least one of magnesium, nickel, chromium, zinc, and manganese, and the metal element in the second metal salt is selected from at least one of aluminum, iron, cobalt, and manganese.

[0021] Furthermore, the ruthenium-based catalyst with structural confinement effect was applied to the oxygen evolution reaction at the anode of proton exchange membrane water electrolysis. In a 0.1 mol / L sulfuric acid electrolyte, linear sweep voltammetry was used to test the oxygen evolution reaction overpotential at a current density of 10 mA / cm², and the overpotential was no higher than 280 mV.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: by measuring the lithium content in lithium-doped spinel oxide and determining the target delithiation amount, the present invention establishes a correlation between the concentration of tetrafluoroborate nitrate solution and the delithiation amount, and designs multiple concentration gradients for delithiation reactions accordingly. The lithium content of the products is determined by inductively coupled plasma atomic emission spectrometry to determine the delithiation compliance, and X-ray diffraction is used to analyze the integrity of the spinel framework structure. Finally, the lowest concentration value is selected as the lowest effective concentration from the concentration gradients that meet the delithiation requirements, have no impurity phase peaks, and whose full width at half maximum (FWHM) increases do not exceed the threshold. This achieves the optimal balance between delithiation efficiency and framework structure preservation, ensuring the formation of an effective spatially confined structure while avoiding framework collapse or impurity phase generation, thus guaranteeing the full play of the structural confinement effect of ruthenium-based catalysts.

[0023] Furthermore, this invention monitors the conductivity changes of the reaction system in real time, collects data at fixed time intervals and calculates the conductivity change rate, sets a conductivity change rate threshold and a continuous stabilization time window as equilibrium criterion parameters, and calculates the conductivity change rate at the current sampling point in real time. When the conductivity change rate first drops below the set change rate threshold, the continuous stabilization time window timing is started. During the window period, the conductivity change rate of each sampling point is continuously monitored. If the conductivity change rate of all sampling points remains below the threshold during the window period, the reaction is determined to have reached equilibrium. If the conductivity change rate of any sampling point exceeds the threshold during the window period, the timing is terminated and the window is reset. When the rate of change of conductivity decreases below the threshold again, the timing is restarted. The reaction equilibrium time is finally determined based on the time when the equilibrium state is reached and the time when the reaction begins. This achieves dynamic, accurate, and quantifiable determination of the reaction equilibrium state, avoiding misjudgments caused by instantaneous fluctuations or noise signals. The rate of change threshold can be set as an absolute value or a percentage relative to the initial maximum rate of change. Using a relative percentage threshold can eliminate the influence of differences in absolute rate of change values ​​between different batches of reaction, ensuring that the delithiation product and the ruthenium-containing salt solution react fully to the thermodynamic equilibrium state, thereby ensuring the uniform loading and stable anchoring of ruthenium in the spatially confined structure.

[0024] Furthermore, this invention ensures the full progress of the delithiation reaction by using acetonitrile as the solvent for the tetrafluoroborate nitrate solution and controlling the amount of tetrafluoroborate nitrate to be several times the molar amount of spinel oxide. Simultaneously, the spinel oxide with a spatially confined structure is dispersed in a ruthenium-containing salt solution, the reaction temperature is controlled within an appropriate range, and the reaction equilibrium time is dynamically determined using real-time conductivity monitoring. The actual equilibrium time is determined by the conductivity change rate remaining consistently below a threshold percentage. This achieves a balance between the sufficiency of the delithiation process and the equilibrium of the ruthenium loading process, avoiding uneven ruthenium loading due to insufficient reaction time or structural damage due to excessive reaction time. This ensures the uniform anchoring and stable existence of ruthenium within the spatially confined structure.

[0025] Furthermore, this invention controls the molar ratio of spinel oxide to ruthenium chloride to an appropriate ratio, prepares a ruthenium salt solution using deionized water, disperses the spatially confined spinel oxide in the ruthenium solution, and dynamically determines the reaction equilibrium time using real-time conductivity monitoring at suitable reaction temperature and stirring speed. After the reaction, the solution is filtered, dried, and transferred to a tube furnace for calcination at an appropriate temperature under a mixed atmosphere of hydrogen and argon. This achieves uniform loading and stable anchoring of ruthenium in the spatially confined structure of the spinel. At the same time, moderate calcination under a reducing atmosphere yields metallic ruthenium species with high catalytic activity, and the growth of ruthenium particles is physically constrained by the spinel framework, avoiding agglomeration. This significantly improves the structural stability, dispersibility, and catalytic activity of the ruthenium-based catalyst.

[0026] Furthermore, this invention, through precise control of the reaction time, enables ruthenium ions to fully diffuse and occupy the original lithium-ion lattice vacancies left after delithiation treatment. This achieves precise inheritance and in-situ loading of ruthenium atoms onto the original lithium-ion lattice sites, ultimately ensuring that the type of lattice sites occupied by ruthenium atoms is consistent with the initial type of lithium-ion sites. Through this site-consistent structural confinement effect, ruthenium atoms are anchored in specific lattice sites within the spinel framework. Their migration and aggregation are constrained by the steric hindrance of surrounding atoms, thereby significantly improving the structural stability, anti-sintering ability, and long-lasting catalytic activity of ruthenium-based catalysts under high-temperature reducing atmospheres.

[0027] Furthermore, this invention prepares lithium-doped binary hydroxides using a co-precipitation method. Component A, containing lithium salt, a first metal salt, and a second metal salt, and component B, containing a precipitant, are simultaneously added dropwise to the reaction medium component C. The co-precipitation reaction is carried out under stirring conditions, with the pH controlled within an alkaline range. After the reaction, the precursor is centrifuged, washed to neutral, and dried to obtain a binary hydroxide precursor with lithium ions uniformly distributed in the layers, providing a structural basis for subsequent calcination into spinel oxide. The resulting ruthenium-based catalyst with structural confinement effect is then applied to the oxygen evolution reaction (OER) at the anode of proton exchange membrane water electrolysis. Linear sweep voltammetry is used in an acidic electrolyte. The OER overpotential remains low under moderate current density conditions, and after 1000 hours of galvanostatic testing, the potential remains stable without significant increase, indicating that the catalyst possesses both excellent catalytic activity and long-term operational stability under acidic OER conditions. Attached Figure Description

[0028] Figure 1 This is a flowchart of a method for improving the performance stability of ruthenium-based catalysts based on structural confinement effects, provided in an embodiment of the present invention. Figure 2 This is a graph showing the X-ray diffraction data of the ruthenium-based catalyst material prepared in Example 1 of this invention. Figure 3 This is a microstructure diagram of the ruthenium-based catalyst with a confined structure in Example 1 of the present invention; Figure 4 This is a graph showing the oxygen evolution reaction activity of the catalyst evaluated by linear sweep voltammetry (LSV) according to an embodiment of the present invention. Figure 5 This is a durability test curve of the catalyst under constant current provided in the embodiments of the present invention. Detailed Implementation

[0029] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0030] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0031] Please see Figures 1-5 As shown, where, Figure 1 This is a flowchart of a method for improving the performance stability of ruthenium-based catalysts based on structural confinement effects, provided in an embodiment of this application. Figure 2 This is a graph showing the X-ray diffraction data of the ruthenium-based catalyst material prepared in Example 1 of this invention. Figure 3 This is a microstructure diagram of the ruthenium-based catalyst with a confined structure in Example 1 of the present invention; Figure 4 This is a graph showing the oxygen evolution reaction activity of the catalyst evaluated by linear sweep voltammetry (LSV) according to an embodiment of the present invention. Figure 5 This is a durability test curve of the catalyst under constant current provided in the embodiments of the present invention.

[0032] like Figure 1 As shown, the technical solution provided in this application includes the following steps: Step S1: Prepare lithium-doped binary hydroxide, and obtain lithium-doped spinel oxide by calcination; Step S2: Calculate the concentration of the tetrafluoroborate solution based on the lithium doping amount in the spinel oxide according to a preset delithiation ratio, disperse the lithium-doped spinel oxide in the tetrafluoroborate solution to react and delithiate, and obtain a spinel oxide with a spatially confined structure. Step S3: The spinel oxide with spatial confinement structure is dispersed in a ruthenium-containing salt solution for reaction. The conductivity of the reaction system is monitored in real time. The reaction equilibrium time is determined based on the change in the conductivity of the reaction system. When the rate of change in conductivity is lower than a set threshold, the reaction equilibrium is determined and the reaction product is obtained. Step S4: The reaction products are filtered, dried and transferred to a tube furnace for calcination. The calcination time is determined based on the change in the conductivity of the calcined products. The products are calcined for the specified time to obtain a ruthenium-based catalyst with a structural confinement effect.

[0033] Specifically, in step S2, the concentration of the tetrafluoroborate solution is calculated based on the lithium doping amount in the spinel oxide according to a preset delithiation ratio, including: Step S21: Determine the lithium content in the spinel oxide to determine the target lithium content to be removed; Step S22: Based on the target delithiation amount, establish the correlation between the concentration of tetrafluoroborate nitrate solution and the delithiation amount; Step S23: Based on the correlation and the characterization and detection of the delithiation products, select the lowest effective concentration of tetrafluoroborate nitrate solution that can achieve the target delithiation amount without damaging the framework structure.

[0034] In this embodiment, the lithium-doped spinel oxide sample obtained after calcination was used, and the lithium content was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The mass fraction of lithium in the sample was found to be 3.2%. Based on the preset target delithiation ratio (e.g., removing 60% of the total lithium), the target lithium content to be removed was calculated to be 1.92% (relative to the sample mass). A series of acetonitrile solutions of tetrafluoroborate nitrate with different concentrations were prepared, namely 0.05 mol / L, 0.10 mol / L, 0.15 mol / L, and 0.20 mol / L. Equal masses of spinel oxide (e.g., 2 g) were dispersed in 50 mL of the above solutions, and the mixture was stirred at 25 °C for 12 hours. By measuring the residual lithium ion concentration after the reaction, the relationship between the tetrafluoroborate nitrate concentration (C) and the delithiation amount (Q) was established. A linear relationship was obtained by fitting the equation: Q (mg / g) = 12.3 × C (mol / L) + 0.2, correlation coefficient R² > 0.99.

[0035] Based on the above correlation, to achieve a delithiation rate of 1.92% (i.e., 38.4 mg / g), the required concentration of nitric tetrafluoroborate is approximately 3.1 mol / L. However, X-ray diffraction and nitrogen adsorption experiments revealed that when the concentration exceeded 2.5 mol / L, the diffraction peaks of the spinel structure began to broaden significantly, and the specific surface area decreased by more than 15%, indicating partial damage to the framework. Therefore, 2.5 mol / L was chosen as the minimum effective concentration. Under this condition, the actual delithiation rate reached 1.88% (98% of the target delithiation rate), while the material maintained its original spinel structure with intact spatial confinement.

[0036] Specifically, in step S23, based on the correlation and characterization of the delithiation products, the lowest effective concentration of the tetrafluoroborate nitrate solution that can achieve the target delithiation amount without damaging the framework structure is selected, including: Step S231: Based on the aforementioned correlation, design a tetrafluoroborate nitrate solution containing multiple concentration gradients, with each concentration gradient maintaining an equal or logarithmic interval distribution. In this embodiment, the established correlation model between lithium removal amount and tetrafluoroborate nitrate concentration (Q=12.3×C+0.2, R²=0.99) is used, where Q is the actual lithium removal amount (mg / g) and C is the molar concentration of tetrafluoroborate nitrate (mol / L). The target lithium removal amount is 38.4 mg / g (corresponding to 60% of the total lithium in lithium-doped spinel oxide). An equally spaced gradient design strategy is adopted, setting the concentration sequence of tetrafluoroborate nitrate / acetonitrile solution as: 1.0, 1.5, 2.0, 2.5, 3.0 mol / L; at the same time, logarithmic interval auxiliary groups (0.8, 1.6, 3.2 mol / L) are added to verify the nonlinear segment of the concentration-lithiation amount response.

[0037] Step S232: The spinel oxides prepared in the same batch are dispersed in tetrafluoroborate nitrate solutions of different concentration gradients and delithiation reaction is carried out under the same reaction conditions. After the reaction is completed, the products are subjected to solid-liquid separation, washing and drying. In this embodiment, 2.000 g ± 0.005 g of lithium-doped spinel oxide from the same synthesis batch were dispersed in 50.0 mL of tetrafluoroborate nitrile / acetonitrile solutions of various concentration gradients. The reaction conditions were uniformly controlled as follows: high-purity nitrogen atmosphere, temperature 25.0℃ ± 0.5℃, magnetic stirring speed 400 rpm, and reaction time 12.0 h. After the reaction, solid-liquid separation was achieved by centrifugation (8000 rpm, 10 min). The precipitate was washed three times with anhydrous acetonitrile (30 mL each time) and then dried in a vacuum drying oven at 60℃ for 12 h to obtain the delithiation products corresponding to each concentration gradient.

[0038] Step S233: Characterize and detect the delithiation products of each concentration gradient after drying. The characterization and detection include: determining the lithium content of each product using inductively coupled plasma atomic emission spectrometry, and determining whether the target delithiation amount has been reached based on the original lithium content and the remaining lithium content; and analyzing the integrity of the spinel framework structure of each product using X-ray diffraction to determine whether structural collapse or impurity phases have occurred. In this embodiment, inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to quantitatively analyze the residual lithium content in the delithiation products at various concentration gradients. Samples were pretreated by microwave digestion before being analyzed to obtain the mass fraction of residual lithium in each product. The measured residual lithium content was compared with the initial lithium content in the original lithium-doped spinel oxide to calculate the actual delithiation amount, which was then compared with the preset target delithiation amount to determine whether the target delithiation requirement was met under each concentration gradient. The comparison results showed that at lower tetrafluoroborate nitrate concentrations, the actual delithiation amount was significantly lower than the target value; as the concentration increased, the delithiation amount gradually increased; only when the concentration reached a certain critical value could the delithiation amount approach or reach the target delithiation amount.

[0039] X-ray diffraction was used to characterize the crystal structures of the delithiation products at various concentration gradients. A CuKα radiation source was used, and diffraction patterns were acquired within a set scanning range. The analysis focused on three main aspects: First, the presence and retention of spinel characteristic diffraction peaks. The clarity and sharpness of multiple characteristic crystal plane diffraction peaks (including high-index crystal planes) belonging to the spinel phase were observed. Second, impurity phase identification. The presence of additional diffraction peaks belonging to non-spinel phases, such as characteristic peaks of lithium-rich manganese oxide, manganese oxide, or other impurity phases, was carefully examined. The presence of such impurity peaks indicates that the delithiation process induced an irreversible phase transformation. Third, the evaluation of diffraction peak broadening. The strongest or most representative characteristic diffraction peak in the spinel phase was selected, and its full width at half maximum (FWHM) was compared with the corresponding FWHM of the original, untreated spinel oxide. A significant broadening of the full width at half maximum (FWHM) usually indicates a decrease in crystal order, accumulation of lattice distortion, or reduction in grain size, marking the beginning of skeletal degradation. Analysis showed that at lower concentrations of nitric tetrafluoroborate, all characteristic spinel diffraction peaks were clearly distinguishable, with no impurity peaks appearing, and the FWHM of the characteristic peaks showed no significant change compared to the original sample, indicating that the spinel skeletal structure remained intact. When the concentration increased to a certain critical level, the characteristic spinel diffraction peaks still existed without obvious impurities, but the FWHM of some characteristic peaks showed a moderate broadening, suggesting that the crystal structure had undergone some degree of relaxation or defect accumulation, but the overall skeletal structure remained intact. When the concentration further increased to above a certain threshold, impurity peaks belonging to non-spinel phases appeared in the diffraction pattern, while the intensity of the characteristic spinel diffraction peaks decreased significantly and the peak shape broadened markedly, indicating that excessive delithiation had led to local collapse or irreversible phase transformation of the spinel skeletal structure.

[0040] Step S234: Select the lowest concentration value from the concentration gradients that meet the following two conditions as the lowest effective concentration of the tetrafluoroborate nitrate solution: the actual delithiation amount reaches or exceeds the set threshold of the target delithiation amount, and no impurity peaks belonging to non-spinel phases appear in the X-ray diffraction pattern, and the full width at half maximum (FWHM) of the spinel characteristic diffraction peaks does not exceed the set threshold of the initial value.

[0041] In this embodiment, two screening thresholds are preset: the first threshold is the delithiation amount threshold. The actual delithiation amount must reach a specific percentage above the target delithiation amount to be considered to meet the delithiation requirements. This threshold is set based on the activity requirements of the subsequent catalyst; delithiation amounts below this threshold will not form an effective spatially confined structure. The second threshold is the structural integrity threshold. It requires that no impurity peaks belonging to non-spinel phases appear in the X-ray diffraction pattern, and that the increase in the full width at half maximum (FWHM) of the spinel characteristic diffraction peaks does not exceed a set percentage of the initial value. This threshold is set based on the stability requirements of the spinel framework structure; structural degradation exceeding this threshold will affect the confinement effect.

[0042] The characterization results for all obtained concentration gradients were evaluated step-by-step in ascending order of concentration. For low concentration gradients, the delithiation amount was first examined to see if it met the target threshold. The evaluation revealed that in the lower concentration range, the actual delithiation amount was significantly lower than the target delithiation amount, failing to meet the set threshold. Therefore, such concentration gradients were excluded regardless of structural integrity. As the concentration increased to a certain intermediate level, the delithiation amount began to approach or reach the set threshold. At this point, the structural integrity of the delithiated products at this concentration gradient was further examined. X-ray diffraction patterns were evaluated to confirm the presence of non-spinel phase impurities and to calculate whether the increase in the full width at half maximum (FWHM) of the spinel characteristic diffraction peaks was controlled within the set threshold. If both requirements were met, the concentration gradient entered the candidate range; at concentrations higher than the candidate concentration, the delithiation amount usually met or exceeded the target threshold. However, structural integrity needs to be carefully assessed at this point: X-ray diffraction patterns at some high concentration gradients may show impurity peaks belonging to non-spinel phases, or the full width at half maximum (FWHM) of spinel characteristic diffraction peaks may significantly exceed the set threshold, indicating that excessive delithiation has led to irreversible degradation of the framework structure. Such concentration gradients, despite meeting the delithiation target, are excluded due to compromised structural integrity.

[0043] After evaluating all concentration gradients stepwise, a candidate set of concentration gradients was obtained, consisting of several that met the dual conditions of achieving delithiation and structural integrity. The lowest concentration value in this candidate set is the critical concentration that can achieve the target delithiation amount while satisfying the structural integrity requirement. The lowest concentration value was selected from the candidate set as the minimum effective concentration of the tetrafluoroborate nitrate solution. This concentration has the following technical significance: below this concentration, the delithiation amount cannot meet the target requirement; above this concentration, although the delithiation amount can be further increased, it will come at the cost of sacrificing the structural integrity of the spinel framework, which is not conducive to the subsequent construction of the space-confined structure. Therefore, this minimum effective concentration represents the optimal balance point between delithiation efficiency and structural preservation.

[0044] This invention determines the target delithiation amount by measuring the lithium content in lithium-doped spinel oxide and establishing a correlation between the concentration of tetrafluoroborate nitrate solution and the delithiation amount. Based on this, multiple concentration gradients are designed for delithiation reactions. The lithium content of the products is determined by inductively coupled plasma atomic emission spectrometry to assess the delithiation compliance. X-ray diffraction is used to analyze the integrity of the spinel framework structure. Finally, the lowest concentration value is selected from the concentration gradients that meet the delithiation target, have no impurity phase peaks, and whose full width at half maximum (FWHM) increases do not exceed the threshold as the minimum effective concentration. This achieves an optimal balance between delithiation efficiency and framework structure preservation, ensuring the formation of an effective spatially confined structure while avoiding framework collapse or impurity phase generation, thus guaranteeing the full utilization of the structural confinement effect of the ruthenium-based catalyst.

[0045] Specifically, in step S3, determining the reaction equilibrium time based on the change in the conductivity of the reaction system includes: Step S31: Record the initial conductivity value at the start of the reaction, collect the conductivity data of the reaction system in real time at fixed time intervals, and calculate the rate of change of conductivity within the time interval. Step S32: When multiple consecutive conductivity change rates fluctuate within a preset threshold percentage range, the reaction is determined to have reached equilibrium. Step S33: Determine the reaction equilibrium time based on the moment when the equilibrium state is reached and the moment when the reaction begins.

[0046] Specifically, in step S32, determining that the reaction has reached an equilibrium state includes: Step S321: Set equilibrium criterion parameters, including conductivity change rate threshold and continuous stable time window; wherein, the conductivity change rate threshold can be set to an absolute value (e.g., 0.1 μS / (cm·min)) or a percentage of change rate between adjacent intervals of 1%-5%; Step S322: Calculate the rate of change of conductivity at the current sampling point in real time; Step S323: When the rate of change of conductivity first decreases below the set rate of change threshold, the timing of the continuous stable time window is started; Step S324: Within the continuous stable time window, continuously monitor the rate of change of conductivity at each sampling point. If the rate of change of conductivity at all sampling points remains below the set rate of change threshold within the window period, it is determined that the reaction has reached equilibrium. Step S325: If the rate of change of conductivity at any sampling point exceeds the set rate of change threshold during the continuous stable time window, the current timing is terminated and the window is reset. Timing is restarted when the rate of change of conductivity drops below the rate of change threshold again.

[0047] In this embodiment, spinel oxide with a spatially confined structure is dispersed in a ruthenium-containing salt solution, and conductivity monitoring is initiated simultaneously with the start of the reaction. The initial conductivity value is recorded at the start of the reaction, and then the conductivity data of the reaction system is collected in real time at fixed time intervals. After each new conductivity data point is obtained, the change in conductivity relative to the previous time interval is calculated and further converted into a conductivity change rate to characterize the speed of the reaction. Before the reaction begins, two key equilibrium criteria parameters are pre-set: one is a percentage threshold for the rate of change, used to determine whether the conductivity change has approached zero; the other is a continuous stable time window, used to determine the duration for which the conductivity change rate can remain below the threshold. The setting of these parameters is based on the reaction kinetics characteristics of the system and the required equilibrium accuracy.

[0048] The conductivity change rate at the current sampling point is calculated in real time. As the reaction proceeds, the conductivity change rate generally shows a decreasing trend. The system monitors the numerical change in conductivity change rate in real time. When it first drops below a pre-set threshold (this threshold can be an absolute value, such as 0.1 μS / (cm·min), or a percentage change rate between adjacent intervals of 1%~5%), the system determines that the reaction has entered the critical stability region and immediately starts timing the continuous stability time window. It should be noted that, to eliminate the influence of initial change rate differences between different batches of reaction, it is recommended to use the change rate between adjacent intervals as the change rate threshold (e.g., a percentage of 1%~5%), thereby normalizing the equilibrium criterion.

[0049] During the continuous steady-state time window, the system continuously monitors the relative rate of change at each sampling point within the window. If the relative rate of change at each sampling point remains below the threshold percentage throughout the entire window period, without any instance exceeding the threshold, the reaction is determined to have reached equilibrium. If, during the continuous steady-state time window, the relative rate of change at any sampling point exceeds the threshold percentage, it indicates that the reaction system has experienced fluctuations exceeding the expected magnitude during that period and has not yet reached true equilibrium. In this case, the system immediately terminates the timing of the current window and resets the window state to zero. Once the relative rate of change decreases below the threshold percentage again during subsequent monitoring, the timing of the continuous steady-state time window is restarted, and the monitoring and determination process in step S324 is repeated. When the reaction is determined to have reached equilibrium, the system records the moment when this equilibrium state occurs. The time interval between the start of the reaction and the moment the equilibrium state is reached is calculated and determined as the reaction equilibrium time of the system. This equilibrium time is used to guide the setting of reaction time for subsequent batches, ensuring that each batch of delithiation products can fully react with the ruthenium-containing salt solution to a thermodynamic equilibrium state, thereby ensuring uniform loading and stable anchoring of ruthenium in the spatially confined structure.

[0050] This invention monitors the conductivity changes of the reaction system in real time, collects data at fixed time intervals and calculates the rate of change of conductivity, sets a conductivity change rate threshold and a continuous stabilization time window as equilibrium criterion parameters, and calculates the conductivity change rate at the current sampling point in real time. When the conductivity change rate first drops below the set threshold, the continuous stabilization time window is started. During the window period, the conductivity change rate of each sampling point is continuously monitored. If the conductivity change rate of all sampling points remains below the threshold during the window period, the reaction is determined to have reached equilibrium. If the conductivity change rate of any sampling point exceeds the threshold during the window period, the timing is terminated and the window is reset. When the rate of change of conductivity decreases below the threshold again, the timing is restarted. The reaction equilibrium time is finally determined based on the time when the equilibrium state is reached and the time when the reaction begins. This achieves dynamic, accurate, and quantifiable determination of the reaction equilibrium state, avoiding misjudgments caused by instantaneous fluctuations or noise signals. The rate of change threshold can be set as an absolute value or a percentage relative to the initial maximum rate of change. Using a relative percentage threshold can eliminate the influence of differences in absolute rate of change values ​​between different batches of reaction, ensuring that the delithiation product and the ruthenium-containing salt solution react fully to the thermodynamic equilibrium state, thereby ensuring the uniform loading and stable anchoring of ruthenium in the spatially confined structure.

[0051] Specifically, the lithium-doped binary hydroxide in step S1 is composed of two or more chemical elements in different valence states. One of the metal elements includes at least one of magnesium, nickel, chromium, zinc, and manganese; the second metal element includes at least one of aluminum, iron, cobalt, and manganese; and the amount of lithium doping is 1% to 99% of the molar amount of the metal element in the spinel.

[0052] In this embodiment, the lithium-doped binary hydroxide is composed of two or more chemical elements with different valence states. The first metal element is selected from at least one of magnesium, nickel, chromium, zinc, and manganese; the second metal element is selected from at least one of aluminum, iron, cobalt, and manganese. It should be noted that when both the first and second metal elements contain manganese, they can be the same element but with different valence states to achieve valence state differences among the metal elements in the binary hydroxide. Specifically, the lithium-doped binary hydroxide used in this embodiment is a lithium-doped magnesium-aluminum layered bimetallic hydroxide, where magnesium is the first metal element and aluminum is the second metal element. The lithium doping amount is set to replace a specific percentage of the total molar amount of metal elements in the spinel structure, and this percentage is adjusted within the range of 1% to 99% according to the performance requirements of the target product.

[0053] As a preferred embodiment, the lithium doping amount is set to replace 50% of the total molar amount of the metal elements in this embodiment. At this doping ratio, a lithium-doped spinel oxide with a suitable lithium vacancy concentration can be obtained after subsequent calcination, providing a controllable lithium removal window for the subsequent delithiation step. In another optional embodiment, the first metal element in the lithium-doped binary hydroxide is nickel, and the second metal element is cobalt, forming a lithium-doped nickel-cobalt binary hydroxide precursor. In yet another optional embodiment, the first metal element in the lithium-doped binary hydroxide is zinc, and the second metal element is iron, forming a lithium-doped zinc-iron binary hydroxide precursor. In yet another optional embodiment, both the first and second metal elements in the lithium-doped binary hydroxide are manganese, but the manganese is present in different valence states (such as Mn(II) and Mn(III) or Mn(IV)) by controlling the synthesis conditions, forming a lithium-doped manganese-based binary hydroxide precursor. The aforementioned lithium-doped binary hydroxides were prepared using a co-precipitation method or a hydrothermal method. By controlling the ratio of the metal salt solution, the dropping rate of the precipitant, the reaction temperature, and the pH value, lithium ions were uniformly incorporated into the lamellar structure of the binary hydroxide, resulting in a precursor material with good crystallinity and uniform elemental distribution. This precursor can be converted into lithium-doped spinel oxide through subsequent calcination.

[0054] Specifically, in step S1, calcination is carried out in an air atmosphere at a temperature of 600°C to 1000°C.

[0055] In this embodiment of the invention, a lithium-doped binary hydroxide precursor prepared by co-precipitation or hydrothermal method is placed in a muffle furnace or tube furnace, using air as the calcination atmosphere. The furnace temperature is raised to the target calcination temperature at a set heating rate, and held at this temperature for a preset time to completely convert the precursor into lithium-doped spinel oxide. As a specific implementation of this embodiment, the calcination temperature is set to 800°C. At this temperature, the lithium-doped binary hydroxide undergoes thermal decomposition and a solid-state reaction, causing the lamellar structure to collapse and recombine, forming an oxide product with a spinel crystal phase structure. As another optional implementation of this embodiment, when a spinel product with higher crystallinity or a specific crystal orientation is required, the calcination temperature is set to 900°C–1000°C. As yet another optional implementation of this embodiment, when retaining a smaller grain size or a higher specific surface area is required, the calcination temperature is set to 600°C–750°C. In this embodiment, the heating rate is controlled to increase the temperature by a certain temperature per minute (e.g., 5°C to 10°C), and the holding time is set to 2 to 12 hours to ensure that the precursor is fully decomposed, the crystal phase transformation is complete, and the elements are uniformly distributed. After calcination, the sample is cooled in the furnace or quickly removed and cooled to room temperature in air to obtain lithium-doped spinel oxide.

[0056] Specifically, in step S2, the solvent of the tetrafluoroborate nitrate solution is at least one of solvents such as ethanol, acetonitrile, dichloromethane, and nitromethane, and the amount of tetrafluoroborate nitrate is 0.5 to 10 times the molar amount of spinel oxide.

[0057] Specifically, in step S3, the reaction temperature is 25℃~100℃ and the reaction time is 1h~96h.

[0058] In this embodiment, acetonitrile was selected as the solvent for the tetrafluoroborate nitrate solution, and the amount of tetrafluoroborate nitrate was set to three times the molar amount of spinel oxide to ensure the complete delithiation reaction. The spinel oxide with a spatially confined structure was dispersed in a ruthenium-containing salt solution. The reaction temperature was controlled at 60°C, and the reaction time was dynamically determined using real-time conductivity monitoring. The preset time window was 1 h to 96 h, and the actual equilibrium time was determined when the rate of change in conductivity remained continuously stable below the threshold percentage. Through the above condition control, the completeness of the delithiation process and the balance of the ruthenium loading process were achieved, ensuring the structural confinement effect and catalytic activity of the final ruthenium-based catalyst.

[0059] This invention ensures the full progress of the delithiation reaction by using acetonitrile as the solvent for the tetrafluoroborate nitrate solution and controlling the amount of tetrafluoroborate nitrate to be several times the molar amount of spinel oxide. Simultaneously, the spinel oxide with a spatially confined structure is dispersed in a ruthenium-containing salt solution, the reaction temperature is controlled within an appropriate range, and the reaction equilibrium time is dynamically determined using real-time conductivity monitoring. The actual equilibrium time is determined by the continuous and stable conductivity change rate below a threshold percentage. This achieves a balance between the sufficiency of the delithiation process and the equilibrium of the ruthenium loading process, avoiding uneven ruthenium loading due to insufficient reaction time or structural damage due to excessive reaction time. This ensures the uniform anchorage and stable existence of ruthenium within the spatially confined structure.

[0060] Specifically, in step S3, the molar ratio of spinel oxide to ruthenium salt is 0.01 to 1, and the ruthenium salt is selected from one or more of ruthenium chloride, ruthenium nitrate, ruthenium acetylacetonate, and nitrosyl ruthenium, and a solution is prepared by selecting an appropriate solvent according to the characteristics of the ruthenium precursor.

[0061] Specifically, in step S3, the spinel oxide with a spatially confined structure is dispersed in a ruthenium-containing salt solution for reaction. The reaction temperature is 25℃~60℃, the stirring speed is 100r / min~1000r / min, and the reaction time is 1h~96h.

[0062] Specifically, the calcination in step S4 is carried out in an atmosphere of hydrogen, argon, nitrogen or a mixture thereof, at a temperature of 100℃ to 600℃, and for a time of 0.5h to 10h.

[0063] In this embodiment, the molar ratio of spinel oxide to ruthenium chloride was set to 0.1, and a ruthenium salt solution was prepared using deionized water. The spinel oxide with a spatially confined structure was dispersed in the ruthenium-containing solution. The reaction temperature was controlled at 60°C, the stirring speed was set to 400 r / min, and the reaction time was dynamically determined using real-time conductivity monitoring. After the reaction, the solution was filtered, dried, and transferred to a tube furnace for calcination at 300°C for 3 hours under a mixed atmosphere of hydrogen and argon, ultimately obtaining a ruthenium-based catalyst with a structural confinement effect. Through the above controlled conditions, uniform loading and stable anchoring of ruthenium within the spatially confined structure of the spinel were achieved. Simultaneously, moderate calcination under a reducing atmosphere yielded a highly catalytically active metallic ruthenium species, and the growth of the ruthenium particles was physically constrained by the spinel framework, preventing agglomeration.

[0064] This invention achieves uniform loading and stable anchoring of ruthenium in the spinel's spatially confined structure by controlling the molar ratio of spinel oxide to ruthenium chloride to an appropriate proportion and preparing a ruthenium salt solution using deionized water. The spinel oxide, with its spatially confined structure, is dispersed in the ruthenium solution. The reaction equilibrium time is dynamically determined using real-time conductivity monitoring at suitable reaction temperature and stirring speed. After the reaction, the solution is filtered, dried, and transferred to a tube furnace for calcination at an appropriate temperature under a mixed atmosphere of hydrogen and argon. Simultaneously, moderate calcination under a reducing atmosphere yields metallic ruthenium species with high catalytic activity. Furthermore, the growth of ruthenium particles is physically constrained by the spinel framework, preventing agglomeration. This significantly improves the structural stability, dispersibility, and catalytic activity of the ruthenium-based catalyst.

[0065] Specifically, in step S31, the fluctuation range of the rate of change of conductivity within the sampling interval is 1% to 5%, and multiple consecutive time intervals refer to consecutive time periods divided into 3-minute intervals within a continuous time window of 5 to 20 minutes.

[0066] In this embodiment, the fluctuation range of the conductivity change rate within the sampling interval in step S31 is 1% to 5%. Multiple consecutive time intervals refer to consecutive time periods divided into 3-minute intervals within a continuous time window of 5 to 20 minutes. Specifically, during real-time monitoring of the conductivity of the reaction system, the fluctuation tolerance range of the conductivity change rate is set to 1% to 5%. When the calculated conductivity change rate between adjacent sampling points falls within this range, it is considered that the fluctuation is within an acceptable stable range. Regarding the setting of the continuous stable time window, this embodiment uses a continuous time window of 5 to 20 minutes as the time scale for determining whether the reaction has reached equilibrium. Within this time window, several consecutive time periods are divided into 3-minute intervals. For example, when the continuous stable time window is set to 15 minutes, this window contains 5 consecutive 3-minute time periods (i.e., minutes 0 to 3, minutes 3 to 6, minutes 6 to 9, minutes 9 to 12, and minutes 12 to 15). The system needs to monitor the rate of change of conductivity in each 3-minute time period. Only when the rate of change in all time periods remains within the preset fluctuation range (1% to 5%) can the reaction be determined to have reached equilibrium.

[0067] In one specific implementation of this embodiment, the fluctuation threshold for the rate of change of conductivity is set to 3%, and the continuous stabilization time window is set to 12 minutes, divided into four consecutive time periods with 3-minute intervals. In another optional implementation, when the reaction system exhibits large fluctuations, the fluctuation threshold is relaxed to 5%, and the continuous stabilization time window is extended to 20 minutes. In yet another optional implementation, when the reaction system exhibits high stability, the fluctuation threshold is narrowed to 1%, and the continuous stabilization time window is shortened to 5 minutes.

[0068] Specifically, in the ruthenium-based catalyst with structural confinement effect described in step S4, the lattice sites occupied by ruthenium atoms are consistent with the initial occupancy sites of lithium ions in step S1.

[0069] In this embodiment, in the ruthenium-based catalyst with structural confinement effect described in step S4, the lattice sites occupied by ruthenium atoms are consistent with the initial occupied sites of lithium ions in step S1. Specifically, in step S1, lithium ions are incorporated into the spinel framework during calcination, preferentially occupying tetrahedral sites (8a sites) or octahedral sites (16d sites) in the spinel structure. The specific occupied site type depends on the chemical composition and synthesis conditions of the spinel. After the delithiation treatment in step S2, lithium ions are controllably removed from the original occupied sites, leaving vacancy defects with specific coordination environments and spatial sizes in situ. During the reaction in step S3, ruthenium ions diffuse from the ruthenium salt solution into the spinel framework, preferentially occupying these vacancy sites left after the removal of lithium ions, achieving "in-situ occupancy" loading. Therefore, in the final ruthenium-based catalyst, the lattice site type occupied by ruthenium atoms is consistent with the initial site type occupied by lithium ions in step S1: if lithium ions initially occupy tetrahedral sites, then ruthenium atoms also occupy tetrahedral sites; if lithium ions initially occupy octahedral sites, then ruthenium atoms also occupy octahedral sites.

[0070] The achievement of this site consistency depends on the synergistic control of the following conditions: First, in step S2, the delithiation process uses the lowest effective concentration of tetrafluoroborate nitrate solution to ensure that the spinel framework remains intact after delithiation, and the geometry and coordination environment of the vacancy sites do not undergo significant distortion; Second, in step S3, the reaction temperature is controlled between 25℃ and 60℃, so that ruthenium ions enter the vacancy with lower kinetic energy, avoiding the occupation of non-original sites due to excessive thermal disturbance; Third, real-time monitoring of conductivity ensures that the reaction reaches thermodynamic equilibrium, allowing ruthenium ions sufficient time to diffuse to the original lithium site with the lowest energy.

[0071] This invention, through precise control of reaction time, enables ruthenium ions to fully diffuse and occupy the original lithium-ion lattice vacancies left after delithiation treatment. This achieves precise inheritance and in-situ loading of ruthenium atoms onto the original lithium-ion lattice sites, ultimately ensuring that the type of lattice sites occupied by ruthenium atoms is consistent with the initial type of lithium-ion sites. Through this site-consistent structural confinement effect, ruthenium atoms are anchored in specific lattice sites within the spinel framework. Their migration and aggregation are constrained by the steric hindrance of surrounding atoms, thereby significantly improving the structural stability, anti-sintering ability, and long-lasting catalytic activity of ruthenium-based catalysts under high-temperature reducing atmospheres.

[0072] Specifically, the preparation of lithium-doped binary hydroxide in step S1 adopts a co-precipitation method, which includes: simultaneously adding component A, containing lithium salt, a first metal salt, and a second metal salt, and component B, containing a precipitant, to the reaction medium component C; controlling the pH value within the range of 8.0 to 9.0 under stirring conditions to carry out the co-precipitation reaction; after the reaction is completed, centrifuging, washing to neutrality, and drying are performed to obtain lithium-doped binary hydroxide; the metal element in the first metal salt is selected from at least one of magnesium, nickel, chromium, zinc, and manganese, and the metal element in the second metal salt is selected from at least one of aluminum, iron, cobalt, and manganese.

[0073] In this embodiment, component A, containing lithium salt, a first metal salt, and a second metal salt, and component B, containing a precipitant, are simultaneously added dropwise to the reaction medium component C. A co-precipitation reaction is carried out under stirring conditions, with the pH value controlled within the range of 8.0 to 9.0. The first metal salt contains at least one metal element selected from magnesium, nickel, chromium, zinc, and manganese, and the second metal salt contains at least one metal element selected from aluminum, iron, cobalt, and manganese. Specifically, component A in this embodiment contains lithium salt (such as lithium hydroxide or lithium nitrate), magnesium salt (such as magnesium nitrate), and aluminum salt (such as aluminum nitrate), dissolved in deionized water according to the target stoichiometric ratio. The precipitant in component B is selected from at least one of sodium hydroxide, sodium carbonate, ammonia, or urea, preferably a mixed solution of sodium hydroxide and sodium carbonate. The reaction medium for component C is deionized water, initially added to the reaction vessel and preheated to a set temperature (e.g., 40°C to 80°C).

[0074] During the reaction, components A and B were simultaneously added to component C using an acid-base burette at a set dropping rate, with stirring maintained throughout to promote uniform mixing. The pH of the reaction system was monitored in real time using an online pH meter, and the pH was precisely controlled within the range of 8.0–9.0 by adjusting the dropping rate of component B. After the reaction, the resulting suspension was centrifuged, the precipitate was collected, and repeatedly washed with deionized water until the washing solution was neutral (pH=7). The washed precipitate was then transferred to a vacuum drying oven and dried at 60℃–80℃ for 12–24 hours to obtain a lithium-doped binary hydroxide precursor. This precursor has a layered bimetallic hydroxide structure, with lithium ions uniformly distributed in the layers, providing a structural basis for subsequent calcination to convert it into spinel oxide. In another optional embodiment, nickel nitrate is used as the first metal salt, and cobalt nitrate is used as the second metal salt. In yet another optional embodiment, zinc nitrate is used as the first metal salt, and iron nitrate is used as the second metal salt. In another alternative embodiment, both the first metal salt and the second metal salt are manganese salts, and manganese exists in different valence states by controlling the synthesis conditions (such as pH value, temperature, and oxidizing atmosphere).

[0075] Specifically, the ruthenium-based catalyst with structural confinement effect is applied to the oxygen evolution reaction at the anode of proton exchange membrane water electrolysis. In 0.1 mol / L sulfuric acid electrolyte, linear sweep voltammetry is used to test the oxygen evolution reaction overpotential at a current density of 10 mA / cm², and the overpotential is no higher than 280 mV.

[0076] In this embodiment, the prepared ruthenium-based catalyst, conductive carbon black, and perfluorosulfonic acid ionomer (such as Nafion) were dispersed in a certain proportion in a mixed solvent of isopropanol and water, and ultrasonically dispersed to form a uniform catalyst ink. An appropriate amount of ink was drop-coated onto the surface of the glassy carbon working electrode of a rotating disk electrode and dried at room temperature to form a uniform catalyst film. The catalyst loading was controlled within the range of 0.1–0.3 mg / cm². Electrochemical testing employed a three-electrode system, with the rotating disk electrode as the working electrode, a platinum wire or platinum mesh as the counter electrode, and a reversible hydrogen electrode as the reference electrode. The electrolyte was a 0.05 mol / L sulfuric acid solution, which was saturated with high-purity oxygen before testing. Linear sweep voltammetry was performed at a rotating disk electrode speed of 1600 r / min, a scan rate of 5 mV / s–10 mV / s, and a potential scan range from the open circuit potential to 1.8 V (relative to the reversible hydrogen electrode). Record the current density versus potential curve and read the oxygen evolution overpotential at a current density of 10 mA / cm². Accelerated stability testing was performed using the constant current method at 1 A / cm². 2 The working electrode was subjected to constant current treatment at a current density, and the potential drift was recorded over 1000 hours.

[0077] The test results of this embodiment show that the ruthenium-based catalyst with structural confinement effect has an oxygen evolution reaction overpotential of no more than 280 mV at a current density of 10 mA / cm² in 0.1 mol / L sulfuric acid electrolyte, and at a current density of 1 A / cm². 2 The potential drift at a given current density is 0.0148 mV / h. This performance is attributed to the structural confinement effect formed by the precise inheritance of the original lithium-ion lattice sites by ruthenium atoms, which effectively suppresses the dissolution and aggregation of ruthenium under acidic oxygen evolution reaction conditions. At the same time, the spatial confinement of the spinel framework maintains the structural stability of the active sites, thereby achieving a synergistic improvement in low overpotential and high stability.

[0078] This invention prepares lithium-doped binary hydroxides using a co-precipitation method. Component A, containing lithium salt, a first metal salt, and a second metal salt, and component B, containing a precipitant, are simultaneously added dropwise to reaction medium component C. The co-precipitation reaction is carried out under stirring conditions, with the pH controlled within an alkaline range. After the reaction, the precursor is centrifuged, washed to neutral, and dried to obtain a binary hydroxide with lithium ions uniformly distributed in the layers, providing a structural basis for subsequent calcination into spinel oxide. Furthermore, the resulting ruthenium-based catalyst with structural confinement effect is applied to the oxygen evolution reaction (OER) at the anode of proton exchange membrane water electrolysis. Linear sweep voltammetry is used in an acidic electrolyte. The OER overpotential remains low under moderate current density conditions, and after 1000 hours of galvanostatic testing, the potential remains stable without significant increase, indicating that the catalyst possesses both excellent catalytic activity and long-term operational stability under acidic OER conditions.

[0079] Example 1 Component A: Zn(NO3)2·6H2O: 0.595g, LiNO3: 0.055g, Co(NO3)2·6H2O: 1.330g; Component B: NaOH: 0.840g; Component C: H2O: 20mL; Component A and component B were dissolved in 40 mL of deionized water. Components A and B were simultaneously added dropwise to component C under vigorous stirring, maintaining the pH of the system at approximately 8.5. After the addition was complete, the resulting suspension was stirred for 6 hours. The precipitate was separated by centrifugation and repeatedly washed with deionized water until the pH of the washing solution reached neutral. After washing, the precipitate was transferred to a 60°C oven for drying to obtain ZnLi. x Co y (OH) z Precursor. The ZnLi obtained above... x Co y (OH) z The precursor was placed in a muffle furnace and heated to 600°C at a heating rate of 5°C / min in air atmosphere and held for 4 hours to obtain lithium-doped zinc cobalt oxide spinel.

[0080] Under argon protection, 0.3 g of lithium-doped zinc cobalt oxide was dispersed in an acetonitrile solution containing 0.1 g of NO2BF4 and stirred vigorously at room temperature for 48 h to remove lithium from the material. After the reaction was complete, the product was thoroughly washed multiple times with acetonitrile under an argon atmosphere to remove residual LiBF4, and then dried under vacuum at 60 °C for 12 h to obtain zinc cobalt oxide with confined structural vacancies.

[0081] 0.1 g of zinc cobalt oxide spinel powder was impregnated in an aqueous solution containing 0.05 g of ruthenium chloride. After stirring for 12 h, the mixture was subjected to rotary evaporation. The resulting solid was activated at 200 °C for 4 h in a diluted hydrogen atmosphere (5% H2 / Ar) to obtain a ruthenium-based catalyst with structural confinement effect.

[0082] Example 2 Component A: Ni(NO3)2·6H2O: 0.476g, LiNO3: 0.028g, AlCl3·6H2O: 0.5g; Component B: NaOH: 0.840g; Component C: H2O: 20mL; Component A and component B were dissolved in 40 mL of deionized water. Components A and B were simultaneously added dropwise to component C under vigorous stirring, maintaining the pH of the system at approximately 8.5. After the addition was complete, the resulting suspension was stirred for 6 hours. The precipitate was separated by centrifugation and repeatedly washed with deionized water until the pH of the washing solution reached neutral. After washing, the precipitate was transferred to a 60°C oven for drying to obtain LiNi. x Al y (OH) z Precursor. The LiNi obtained above... x Al y (OH) z The precursor was placed in a muffle furnace and heated to 700°C at a heating rate of 5°C / min in air atmosphere and held for 4 hours to obtain lithium-doped nickel aluminate spinel oxide.

[0083] Under argon protection, 0.3 g of nickel aluminate spinel oxide powder was dispersed in an acetonitrile solution containing 0.06 g of NO2BF4, and the mixture was vigorously stirred at room temperature for 48 h to remove Li elements from the material. After the reaction was completed, the product was thoroughly washed multiple times with acetonitrile under an argon atmosphere to remove residual LiBF4, and then dried under vacuum at 60 °C for 12 h to obtain nickel aluminate spinel oxide with confined structural vacancies.

[0084] 0.1 g of nickel aluminate spinel oxide with confined structural vacancies was impregnated in an aqueous solution containing 0.055 g of ruthenium nitrate. After stirring for 12 h, the mixture was subjected to rotary evaporation. The resulting solid was activated at 300 °C for 4 h in a diluted hydrogen atmosphere (5% H2 / Ar) to obtain a ruthenium-based catalyst with a structural confinement effect.

[0085] Comparative Examples This comparative example uses a co-precipitation method combined with an impregnation-calcination process to prepare ruthenium-based catalysts. No lithium ions are introduced for structural control during the process, and no selective delithiation is performed. The aim is to prepare spinel oxide-supported ruthenium-based catalysts using conventional methods as a comparison with the embodiments of this invention.

[0086] Component A: Zn(NO3)2·6H2O: 0.595g, Co(NO3)2·6H2O: 1.330g; Component B: NaOH: 0.840g; Component C: H2O: 20mL; Component A and component B were dissolved in 40 mL of deionized water. Components A and B were simultaneously added dropwise to component C under vigorous stirring, maintaining the pH of the system at approximately 8.5. After the addition was complete, the resulting suspension was stirred for 6 hours. The precipitate was separated by centrifugation and repeatedly washed with deionized water until the pH of the washing solution reached neutral. After washing, the precipitate was transferred to a 60°C oven for drying to obtain ZnCo. y (OH) z Precursor. The ZnCo obtained above... y (OH) z The precursor was placed in a muffle furnace and heated to 600°C at a heating rate of 5°C / min in air atmosphere and held for 4 hours to obtain zinc cobalt oxide spinel.

[0087] Take 0.1 g of zinc cobalt oxide spinel powder and impregnate it in an aqueous solution containing 0.05 g of ruthenium chloride. After stirring for 12 h, the mixture is subjected to rotary evaporation. The resulting solid is activated at 200 °C for 4 h in a diluted hydrogen atmosphere (5% H2 / Ar) to obtain a spinel-supported ruthenium-based catalyst.

[0088] Inductively coupled plasma atomic emission spectrometry (ICP-AES) was performed on the catalyst materials of the examples and comparative examples to determine the ruthenium content in the catalyst materials. The results are shown in Table 1.

[0089] Table 1 shows the ruthenium content in the catalyst materials prepared in the comparative examples and embodiments.

[0090] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A method for improving the performance stability of ruthenium-based catalysts based on structural confinement effects, characterized in that, include: Step S1: Prepare lithium-doped binary hydroxide, and obtain lithium-doped spinel oxide by calcination; Step S2: Calculate the concentration of the tetrafluoroborate solution based on the lithium doping amount in the spinel oxide according to a preset delithiation ratio, disperse the lithium-doped spinel oxide in the tetrafluoroborate solution to react and delithiate, and obtain a spinel oxide with a spatially confined structure. Step S3: The spinel oxide with spatial confinement structure is dispersed in a ruthenium-containing salt solution for reaction. The conductivity of the reaction system is monitored in real time. The reaction equilibrium time is determined based on the change in the conductivity of the reaction system. When the rate of change in conductivity is lower than a set threshold, the reaction equilibrium is determined and the reaction product is obtained. Step S4: The reaction products are filtered, dried and transferred to a tube furnace for calcination. The calcination time is determined based on the change in the conductivity of the calcined products. The products are calcined for the specified time to obtain a ruthenium-based catalyst with a structural confinement effect.

2. The preparation method according to claim 1, characterized in that, In step S2, the concentration of the tetrafluoroborate nitrate solution is calculated based on the lithium doping amount in the spinel oxide according to a preset delithiation ratio, including: Step S21: Determine the lithium content in the spinel oxide to determine the target lithium content to be removed; Step S22: Based on the target delithiation amount, establish the correlation between the concentration of tetrafluoroborate nitrate solution and the delithiation amount; Step S23: Based on the correlation and the characterization and detection of the delithiation products, select the lowest effective concentration of tetrafluoroborate nitrate solution that can achieve the target delithiation amount without damaging the framework structure.

3. The preparation method according to claim 2, characterized in that, In step S23, based on the correlation and characterization of the delithiation products, the lowest effective concentration of the tetrafluoroborate nitrate solution that can achieve the target delithiation amount without damaging the framework structure is selected, including: Step S231: Based on the aforementioned correlation, design a tetrafluoroborate nitrate solution containing multiple concentration gradients, with each concentration gradient maintaining an equal or logarithmic interval distribution. Step S232: The spinel oxides prepared in the same batch are dispersed in tetrafluoroborate nitrate solutions of different concentration gradients and delithiation reaction is carried out under the same reaction conditions. After the reaction is completed, the products are subjected to solid-liquid separation, washing and drying. Step S233: Characterize and detect the delithiation products of each concentration gradient after drying. The characterization and detection include: determining the lithium content of each product using inductively coupled plasma atomic emission spectrometry, and determining whether the target delithiation amount has been reached based on the original lithium content and the remaining lithium content; and analyzing the integrity of the spinel framework structure of each product using X-ray diffraction to determine whether structural collapse or impurity phases have occurred. Step S234: Select the lowest concentration value from the concentration gradients that meet the following two conditions as the lowest effective concentration of the tetrafluoroborate nitrate solution: the actual delithiation amount reaches or exceeds the set threshold of the target delithiation amount, and no impurity peaks belonging to non-spinel phases appear in the X-ray diffraction pattern, and the full width at half maximum (FWHM) of the spinel characteristic diffraction peaks does not exceed the set threshold of the initial value.

4. The preparation method according to claim 1, characterized in that, In step S3, the reaction equilibrium time is determined based on the change in the conductivity of the reaction system, including: Step S31: Record the initial conductivity value at the start of the reaction, collect the conductivity data of the reaction system in real time at fixed time intervals, and calculate the rate of change of conductivity within the time interval. Step S32: When multiple consecutive conductivity change rates fluctuate within a preset threshold percentage range, the reaction is determined to have reached equilibrium. Step S33: Determine the reaction equilibrium time based on the moment when the equilibrium state is reached and the moment when the reaction begins.

5. The preparation method according to claim 4, characterized in that, In step S32, determining that the reaction has reached equilibrium includes: Step S321: Set the equilibrium criterion parameters, including the conductivity change rate threshold and the continuous stable time window; Step S322: Calculate the rate of change of conductivity at the current sampling point in real time; Step S323: When the rate of change of conductivity first decreases below the set rate of change threshold, the timing of the continuous stable time window is started; Step S324: Within the continuous stable time window, continuously monitor the rate of change of conductivity at each sampling point. If the rate of change of conductivity at all sampling points remains below the set rate of change threshold within the window period, it is determined that the reaction has reached equilibrium. Step S325: If the rate of change of conductivity at any sampling point exceeds the set rate of change threshold during the continuous stable time window, the current timing is terminated and the window is reset. Timing is restarted when the rate of change of conductivity drops below the rate of change threshold again.

6. The preparation method according to claim 1, characterized in that, The lithium-doped binary hydroxide in step S1 is composed of two or more chemical elements in different valence states. One of the metal elements includes at least one of magnesium, nickel, chromium, zinc, and manganese; the second metal element includes at least one of aluminum, iron, cobalt, and manganese; and the amount of lithium doping is 1% to 99% of the molar amount of the metal element in the spinel.

7. The preparation method according to claim 1, characterized in that, In step S1, calcination is carried out in an air atmosphere at a temperature of 600℃ to 1000℃.

8. The preparation method according to claim 1, characterized in that, In step S2, the solvent of the tetrafluoroborate nitrate solution is at least one of the solvents such as ethanol, acetonitrile, dichloromethane, and nitromethane, and the amount of tetrafluoroborate nitrate used is 0.5 to 10 times the molar amount of spinel oxide.

9. The preparation method according to claim 1, characterized in that, In step S3, the reaction temperature is 25℃~100℃ and the reaction time is 1h~96h.

10. The preparation method according to claim 1, characterized in that, In step S3, the molar ratio of spinel oxide to ruthenium salt is 0.01 to 1. The ruthenium salt is selected from one or more of ruthenium chloride, ruthenium nitrate, ruthenium acetylacetonate, and nitrosyl ruthenium, and a solution is prepared by selecting an appropriate solvent according to the characteristics of the ruthenium precursor.

11. The preparation method according to claim 1, characterized in that, In step S3, the spinel oxide with a spatially confined structure is dispersed in a ruthenium-containing salt solution for reaction. The reaction temperature is 25℃~60℃, the stirring speed is 100r / min~1000r / min, and the reaction time is 1h~96h.

12. The preparation method according to claim 1, characterized in that, The calcination in step S4 is carried out in an atmosphere of hydrogen, argon, nitrogen or a mixture thereof, at a temperature of 100℃ to 600℃, and for a time of 0.5h to 10h.

13. The preparation method according to claim 4, characterized in that, In step S31, the rate of change of conductivity within the sampling interval fluctuates within the range of 1% to 5%. Multiple consecutive time intervals refer to consecutive time periods divided into 3-minute intervals within a continuous time window of 5 to 20 minutes.

14. The preparation method according to claim 1, characterized in that, In the ruthenium-based catalyst with structural confinement effect described in step S4, the lattice site type occupied by ruthenium atoms is consistent with the initial occupied site of lithium ions in step S1.

15. The preparation method according to claim 1, characterized in that, The preparation of lithium-doped binary hydroxide in step S1 is carried out by co-precipitation method, specifically including: adding component A, which contains lithium salt, a first metal salt and a second metal salt and component B, which contains precipitant, dropwise to reaction medium component C; controlling the pH value within the range of 8.0 to 9.0 under stirring conditions to carry out co-precipitation reaction; after the reaction is completed, centrifuging, washing to neutrality and drying are performed to obtain lithium-doped binary hydroxide; the metal element in the first metal salt is selected from at least one of magnesium, nickel, chromium, zinc and manganese, and the metal element in the second metal salt is selected from at least one of aluminum, iron, cobalt and manganese.

16. The preparation method according to claim 1, characterized in that, The ruthenium-based catalyst with structural confinement effect was applied to the oxygen evolution reaction at the anode of proton exchange membrane water electrolysis. In 0.1 mol / L sulfuric acid electrolyte, the oxygen evolution reaction overpotential was tested by linear sweep voltammetry using a rotating disk electrode and was no higher than 280 mV at a current density of 10 mA / cm².

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