An oxygen evolution reaction catalyst, a preparation method therefor, and use thereof

Abstract

This invention belongs to the technical field of catalytic materials for hydrogen production through water electrolysis, specifically relating to an oxygen evolution reaction catalyst, its preparation method, and its application. The catalyst has the general chemical formula M-M1M2 LDH, where M1 and M2 are one of Fe, Co, and Ni, respectively, and M1 and M2 are not the same element. M is one of V, Cr, Mn, Co, Cu, Zn, Mo, Ce, and Zr. It is prepared using the sol-gel method. This invention optimizes the electronic structure of layered double hydroxides by controllably doping with transition metal elements, synthesizing transition metal-doped layered double hydroxides with a particle size of less than 5 nm, which are used as catalysts for the oxygen evolution reaction and exhibit good electrocatalytic activity. The preparation process of this material is simple and low-cost, providing a new strategy for the development and large-scale production of efficient and stable water electrolysis catalysts.

Description

Technical Field

[0001] This invention belongs to the technical field of catalytic materials for hydrogen production through water electrolysis, specifically relating to an oxygen evolution reaction catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen production through water electrolysis, which decomposes water into high-purity hydrogen and oxygen, provides an important pathway for clean energy conversion. When combined with renewable energy power supply, this process can achieve zero carbon emissions throughout its entire lifecycle. Anion exchange membrane electrolysis (AEMWE) technology can produce hydrogen with a purity exceeding 99.9%, making it particularly suitable for fields with stringent hydrogen purity requirements, such as semiconductor manufacturing and fuel cells. AEMWE combines the technological advantages of proton exchange membrane electrolysis (PEMWE) and alkaline water electrolysis (AWE), but it is still in its early stages of development. The main challenges lie in the membrane and catalyst, particularly the low catalytic activity and unstable electrode structure of non-precious metal electrodes.

[0003] In recent years, non-precious metal oxygen evolution reaction (OER) catalysts have become a research hotspot, among which layered double hydroxides (M1M2LDH), especially NiFe LDH, have attracted much attention due to their low cost and high intrinsic activity. However, they still have significant drawbacks: (1) the layered structure is prone to stacking, which leads to the loss of active sites (such as Ni 3+ / Fe 3+ (1) Insufficient exposure; (2) Poor intrinsic conductivity and low charge transport efficiency; (3) Metal ion dissolution under high current density leads to structural collapse and insufficient stability.

[0004] To address the insufficient activity of traditional OER catalysts, researchers have recently focused on two main strategies: synergistic effects of multi-metal doping and precise control of nanostructures. The nickel-iron-chromium trimetallic layered double hydroxide (NiFeCr LDH) developed by Zhao et al. (US11913125B2) is a typical example. This material is produced by electrodeposition-etching of Cr... 3+ Introduced into the NiFe matrix as a sacrificial template, and after alkaline etching, a porous nanosheet structure with a pore size of 2-10 nm is formed (with an electrochemically active area of ​​54.96 cm²). 2 Cr doping not only inhibits the over-oxidation of the Ni active phase (maintaining β-NiOOH), but also reduces the adsorption energy of the oxygen intermediate through Fe-O bond optimization, ultimately enabling the material to achieve 260mV@100mA / cm in 1M KOH. 2 It exhibits a low overpotential and a Tafel slope of 29 mV / dec, and maintains no performance degradation during a 40,000-second stability test. However, this strategy involves complex preparation methods, and if the doped atoms themselves have weak catalytic activity (such as Cr, V, and some non-metals), they may occupy the positions of highly active metals such as Ni and Fe, thereby reducing the number of active sites.

[0005] Meanwhile, Haase et al. (Nat. Energy 2022, 7, 765-773.) revealed the crucial role of nanoscale effects. When cobalt oxide (CoO) x (OH) y When the size of NPs was reduced to 1 nm, the mass activity increased by 15-fold (1.3→20.4 mA / μg) and the specific activity increased by 2.4-fold (0.5→1.2 mA / cm²). 2 This is attributed to the surface Co-O bond contraction (ΔR = 0.022 Å) and the charge redistribution mechanism dominated by oxygen radicals (oxyl). In other words, reducing catalyst size not only increases specific surface area and exposes more active sites, but also modulates the chemical state of metal elements; however, reducing size also carries the risk of agglomeration.

[0006] In summary, how to construct an OER catalyst that can effectively regulate the electronic structure through component design to enhance intrinsic activity, and form a stable nanostructure to prevent the aggregation of active sites, remains a key problem that urgently needs to be solved in the field of water electrolysis hydrogen production technology. Summary of the Invention

[0007] This invention addresses the problems of insufficient active sites, poor conductivity, and insufficient stability at high current densities in existing layered double hydroxide (M1M2LDH) oxygen evolution reaction catalysts. It provides a nanoscale transition metal-doped layered double hydroxide oxygen evolution reaction catalyst, its preparation method, and its applications. This catalyst, by introducing a transition metal element, utilizes electronic effects to form a synergistic effect with Ni / Fe (or Ni / Co, or Co / Fe) active centers. The M-M1M2LDH nanoscale transition metal-doped layered double hydroxide, prepared using the sol-gel method, exhibits significantly reduced overpotential and Tafel slope in alkaline electrolytes and maintains excellent stability even after long-term operation at high current densities, with a performance degradation rate far lower than that of undoped layered double hydroxides. This catalyst material combines high activity and long lifetime characteristics, providing a new solution for low-energy consumption and high-stability operation of water electrolysis hydrogen production devices.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] The present invention provides a method for preparing an oxygen evolution reaction catalyst, wherein the catalyst has the general chemical formula M-M1M2LDH, wherein M1 and M2 are respectively one of Fe, Co and Ni, and M1 and M2 are not the same element, and M is one of V, Cr, Mn, Co, Cu, Zn, Mo, Ce and Zr.

[0010] Its preparation method includes the following steps:

[0011] (a) Dissolve three metal salts, M1, M2 and M, in a mixed solvent of water and ethanol;

[0012] (b) Add the chelating agent to the mixed solution obtained in step (a) and stir until the mixture is homogeneous;

[0013] (c) Add a gelling agent to the mixed solution obtained in step (b), stir twice, and obtain a sol;

[0014] (d) The sol obtained in step (c) is aged at room temperature to form a gel, and then aged for another time to make the system become a sol again;

[0015] (e) Dry and grind the mixture obtained in step (d).

[0016] In the above technical solution, further, in step (a), the M salt accounts for 1% to 15% of the total molar amount of the three metal salts; the molar ratio of M1 and M2 is 3:1 to 4:1, preferably the anions of the three metal salts are consistent, the three metal salts added should be fully stirred and mixed evenly, if the scale is increased proportionally, the stirring time should be appropriately extended.

[0017] In the above technical solution, further, in step (a), the ratio of the molar amount of water to the total molar amount of the three metal salts is 12:1 to 16:1. If there is too little water, the reaction will be too fast, the doping will be uneven, and the size will be uneven; if there is too much water, the reaction will be too slow, and the resulting catalyst will be too large.

[0018] Ethanol is used as a structure and morphology regulator in the feed, with a molar ratio of ethanol to water of 1.5:1 to 2.5:1. Through kinetic control and physical adsorption, the size, uniformity and dispersibility of the product are determined.

[0019] In the above technical solution, further, in step (b), the stirring time is at least 30 minutes. The stirring time needs to be increased as the amount of material added increases.

[0020] In the above technical solution, further, in step (b), the molar ratio of the chelating agent to the complexed metal salt is determined according to its coordination with the metal salt, and the ratio of the molar amount of the chelating agent to the total molar amount of the three metal salts is 2:3 to 1:6.

[0021] In the above technical solution, further, in step (c), the gelling agent is selected from one of propylene oxide, urea, and hexamethylenetetramine; the molar amount of the gelling agent is 4 to 6 times the total molar amount of the three metal salts.

[0022] In the above technical solution, further, in step (c), the temperature of the second stirring is 25~30℃, and the stirring time is more than 1 minute.

[0023] In the above technical solution, further, in step (d), the aging time for the first aging is 24~48h; and the aging time for the second aging is 24~72h.

[0024] In the above technical solution, further, in step (e), the drying time is more than 24 hours, and the drying method is drying in a forced-air drying oven at 80°C or freeze drying.

[0025] In another aspect, the present invention provides an oxygen evolution reaction catalyst prepared by the above-described preparation method, wherein the catalyst uses a bimetallic layered hydroxide M1M2LDH as a structural matrix, and a doping element M is introduced into the structural matrix; wherein the doping amount of M in the catalyst is 1 to 15 at.% of the total molar amount of the three metals, and the molar ratio of M1 to M2 is 3:1 to 4:1; the particle size of the catalyst is less than 5 nm, preferably 0.5 to 3 nm.

[0026] The present invention also provides an application of the above-mentioned oxygen evolution reaction catalyst in anion exchange membrane water electrolysis.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. This invention provides a ternary doped catalyst with a bimetallic matrix and a dopant. By introducing the transition metal M as an electronic modifier into the active matrix, the electronic structure of the material is optimized to regulate the adsorption energy of intermediates during the reaction. On the one hand, it significantly improves the intrinsic catalytic activity, thus breaking through the intrinsic activity limitations of single or binary metals; on the other hand, compared with traditional ternary mixtures, this invention achieves more efficient and stable charge transfer and catalytic cycling, especially showing significant advantages in the rate and selectivity of the catalytic reaction.

[0029] 2. This invention utilizes a sol-gel method to obtain ultrafine LDH nanoparticles with a particle size of less than 5 nm. This structural feature precisely matches the technical requirements of hydrogen production through water electrolysis (especially AEMWE). At high current densities, the catalyst exhibits extremely high reaction flux per unit area. The ultrafine particle size of this invention dramatically increases the electrochemically active specific surface area of ​​the catalyst, exposing edge active sites far exceeding those of conventional catalysts, directly meeting the demands of high-throughput reactions. Simultaneously, the ultrafine structure combined with transition metal doping forms a dual-regulation mechanism, optimizing the catalyst's adsorption energy for intermediates and promoting charge transport efficiency, jointly contributing to the catalyst's performance at 250–500 mA / cm². 2 Even at higher industrial-grade current densities, it exhibits a significantly reduced overpotential (e.g., 1.81V@2000mA / cm in full-cell testing). 2 It has excellent long-term operational stability.

[0030] 3. This invention determines the formation of the ternary structure and the density of active sites by controlling the molar ratio between the bimetallic matrix and the doped metal M. This ratio, combined with chelating agent control, synergistically ensures atomic-level uniform distribution of each element, avoiding local segregation. Simultaneously, this process effectively suppresses excessive agglomeration of grains during growth and drying, resulting in ultrafine nanoparticles with a concentrated size distribution. Through synergistic control of material composition and microstructure, this invention enables the catalyst to exhibit both low overpotential and excellent operational stability under the high current density conditions required for hydrogen production via water electrolysis. Attached Figure Description

[0031] Figure 1 The XRD pattern of the catalyst prepared in Example 1 is shown below.

[0032] Figure 2 TEM image of the catalyst prepared in Example 1;

[0033] Figure 3 The TEM-mapping image of the catalyst prepared in Example 1 is shown.

[0034] Figure 4 The polarization curves obtained by linear voltammetry scanning of the catalyst prepared in Example 1;

[0035] Figure 5 The results are the stability test results of the catalyst prepared in Example 1;

[0036] Figure 6 The polarization curves were obtained by linear voltammetry scanning of the catalyst prepared in Example 2.

[0037] Figure 7 The polarization curves were obtained by linear voltammetry scanning of the catalyst prepared in Example 3.

[0038] Figure 8 To obtain the polarization curve, a linear voltammetric scan was performed on the catalyst prepared in Comparative Example 1.

[0039] Figure 9 The image shows a TEM image of the catalyst prepared in Comparative Example 2.

[0040] Figure 10 The polarization curves are for the catalyst prepared in Comparative Example 2.

[0041] Figure 11 Impedance curves of the catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0042] Figure 12 The polarization curves are from a full-cell test of the catalyst prepared in Example 1. Detailed Implementation

[0043] The present invention will be further illustrated by specific implementation examples below, but the present invention is not limited to the following embodiments.

[0044] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained commercially or prepared according to conventional methods known to those skilled in the art.

[0045] Example 1

[0046] 1.8 mmol of NiCl2·6H2O, 0.6 mmol of FeCl3·6H2O, and 0.3 mmol of ZnCl2 were dissolved in a mixed solvent of 0.037 mol ultrapure water and 0.017 mol ethanol. 0.9 mmol of acetylacetone (ACAC) was added to the above solution and stirred for 30 min. 0.013 mol of propylene oxide (POX) was added and stirred for 1 min at room temperature (25 °C). The mixture was allowed to stand at room temperature for 12 h, at which point the sol turned into a gel, meaning it did not flow after slight shaking. After standing for about 50 h, the system regained its fluidity. The mixture was freeze-dried for 24 h and then ground to obtain nano-sized Zn-NiFe LDH catalyst.

[0047] Table 1 shows the component analysis of the prepared catalyst by ICP-OES. It can be seen that the atomic doping amount of Zn is not much different from the amount of feed.

[0048] Table 1

[0049]

[0050] according to Figure 1 and Figure 2 The XRD and TEM images show that the prepared catalyst powder exhibits a nanosheet morphology with a particle size of less than 3 nm. Figure 3 The TEM-mapping diagram shown clearly demonstrates the uniform distribution of Zn elements in the NiFe LDH nanosheet structure.

[0051] Half-cell test: 4 mg of the Zn-NiFe LDH catalyst prepared in Example 1 was dissolved in 750 μL of deionized water, 250 μL of isopropanol, and 10 μL of 5 wt% Nafion solution, and sonicated for 2 h; 15 μL of this solution was then drop-coated onto a 5 mm glassy carbon electrode, with a loading of approximately 0.3 mg / cm³. 2 After complete drying, in a three-electrode system, the test temperature was 30℃, using 1M KOH solution as the electrolyte, and LSV scanning was performed on the Zn-NiFe LDH electrocatalyst. Figure 4 As shown. The Zn-NiFe LDH prepared by this method has an efficiency of 10 mA / cm² in a 1M KOH electrolyte solution. 2The potential at the electrolytic current density is 1.467V (vs. RHE) (IR corrected).

[0052] Impedance testing: In a 30°C water bath, the Zn-NiFe LDH prepared in Example 1 was drop-coated onto a glassy carbon electrode using a half-cell testing method, with a loading of 0.3 mg / cm³. 2 The catalyst was tested at a constant voltage of 1.52V (vs. RHE) from 0.1 to 10000Hz with an amplitude of 10mV rms. The test results are as follows. Figure 11 As shown.

[0053] Stability test: The slurry prepared according to the half-cell test procedure was drop-coated at a depth of 1 cm. 2 The Ni fiber felt has a loading capacity of 0.3 mg / cm³. 2 .like Figure 5 As shown, at 1M KOH, 30℃, and 100 mA / cm 2 It ran for 650 hours in a constant current test.

[0054] Example 2

[0055] The same preparation process as in Example 1 was used, except that the amount of Zn salt added was 0.2 mmol and the Zn doping amount was 7.7 at.%.

[0056] The half-cell testing procedure used is the same as in Example 1, and the test results are as follows: Figure 6 As shown. The Zn-NiFe LDH prepared by this method has an efficiency of 10 mA / cm² in a 1M KOH electrolyte solution. 2 The potential at the electrolytic current density is 1.508V (vs. RHE) (IR corrected).

[0057] Example 3

[0058] The same preparation process as in Example 1 was used, except that the Zn salt was replaced with 0.2 mmol of CoCl3·6H2O and the Co doping amount was 7.7 at.%.

[0059] The half-cell testing procedure used is the same as in Example 1, and the test results are as follows: Figure 7 As shown. The Co-NiFe LDH prepared by this method has a current of 10 mA / cm² in 1M KOH electrolyte solution. 2 The potential at the electrolytic current density is 1.520V (vs. RHE) (IR corrected).

[0060] Comparative Example 1

[0061] For the zinc-free control experiment, the same preparation process as in Example 1 was used, except that the precursor solution was changed to 1.8 mmol of NiCl2·6H2O and 0.9 mmol of FeCl3·6H2O solution.

[0062] The half-cell testing procedure used is the same as in Example 1, and the test results are as follows: Figure 8 As shown. The NiFe LDH prepared by this method has a current of 10 mA / cm² in 1M KOH electrolyte solution. 2 The potential at the electrolytic current density is 1.538V (vs. RHE) (IR corrected).

[0063] The impedance testing procedure used is the same as in Example 1, and the test results are as follows: Figure 11 As shown.

[0064] Comparative Example 2

[0065] For a slightly larger control experiment, a co-deposition method was used. A 100 mL beaker containing 20 mL of deionized water was placed in a 40 °C water bath and rotated at 750 rpm. Simultaneously, 30 mL solutions of 75 mM Ni(NO3)2, 25 mM Fe(NO3)3, 12.5 mM Zn(NO3)2, and 0.25 M NaOH were slowly added dropwise to the beaker. After the addition was complete, the mixture was stirred for 1 h, allowed to stand for 24 h, centrifuged, washed three times with deionized water, washed three times with ethanol, and finally dried at 60 °C to obtain larger-sized Zn-NiFe LDH, as shown below. Figure 9 As shown, its particle size is above 10 nm.

[0066] The half-cell testing procedure used is the same as in Example 1, and the test results are as follows: Figure 10 As shown. The large-sized Zn-NiFe LDH prepared using this method showed a flow rate of 10 mA / cm² in a 1M KOH electrolyte solution. 2 The potential at the electrolytic current density is 1.585V (vs. RHE) (IR corrected).

[0067] The impedance testing procedure used is the same as in Example 1, and the test results are as follows: Figure 11 As shown.

[0068] Application Example 1

[0069] (1) Preparation of catalyst slurry:

[0070] The nano-sized Zn-NiFe LDH catalyst powder prepared in Example 1 was reacted with an anion exchange resin (according to the literature). Nat EnergyThe mixture was prepared by the method in 4, 392-398 (2019) at a mass ratio of 17:3, and a mixed solvent of deionized water and isopropanol at a mass ratio of 2:1 was added; a commercial Pt / C catalyst (Johnson Matthey, Pt loading of 50 wt%) and anion exchange resin were mixed at a mass ratio of 4:1 and isopropanol was added, and the mixture was ultrasonically dispersed (power 80 W, 2 h) to form a uniform slurry;

[0071] (2) Fabrication of membrane electrode:

[0072] The above slurry was uniformly coated onto the pretreated anion exchange membrane (PiperIon-A40-HCO3) using an ultrasonic spraying method. - On one side of the surface, the catalyst loading was controlled at 1.5 mg / cm³. 2 A Pt / C catalyst with a Pt loading of 50 wt% was used as the hydrogen evolution catalyst, with a loading of 0.4 mg / cm³. 2 The catalyst layer-membrane integrated structure (CCM) was prepared by soaking in 1M KOH overnight.

[0073] (3) Performance testing:

[0074] Assemble a single battery (effective area 4cm²) 2 In the full battery system, the polarization curves were tested at 80℃ using 1M KOH as the electrolyte (flow rate 20mL / min).

[0075] like Figure 12 As shown, when Zn-NiFe LDH is used as the anode catalyst, only 1.68V is required to reach 1A in a single cell; and only 1.81V is required to reach 2A in a single cell.

[0076] In the catalyst of this invention, the uniform incorporation of M modulates the electronic states of M1 and M2, thereby regulating the adsorption / desorption energy of intermediate species. Simultaneously, the nanostructure of the M-M1M2LDH catalyst weakens the metal-oxygen bond, which promotes the modulation of M1 and M2 elements, achieving a moderate adsorption energy for intermediate species and increasing the exposure of active sites. Therefore, the M-M1M2LDH catalyst prepared in this invention exhibits excellent catalytic performance and long-lasting durability in both laboratory and industrial environments.

[0077] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for preparing an oxygen evolution reaction catalyst, characterized by: The catalyst has the general chemical formula M-M1M2LDH, where M1 and M2 are one of Fe, Co, and Ni, respectively, and M1 and M2 are not the same element. M is one of V, Cr, Mn, Co, Cu, Zn, Mo, Ce, and Zr. Its preparation method includes the following steps: (a) Dissolve three metal salts, M1, M2 and M, in a mixed solvent of water and ethanol; (b) Add the chelating agent to the mixed solution obtained in step (a) and stir until the mixture is homogeneous; (c) Add a gelling agent to the mixed solution obtained in step (b), stir twice, and obtain a sol; (d) The sol obtained in step (c) is aged at room temperature to form a gel, and then aged for another time to make the system become a sol again; (e) Dry and grind the mixture obtained in step (d); In step (b), the chelating agent is acetylacetone; In step (c), the gelling agent is propylene oxide.

2. The method of claim 1, wherein: In step (a), the M salt accounts for 1% to 15% of the total molar amount of the three metal salts; The molar ratio of M1 to M2 is 3:1 to 4:

1.

3. The method of claim 1, wherein: In step (a), the ratio of the molar amount of water to the total molar amount of the three metal salts is 12:1 to 16:1; In the mixed solvent of water and ethanol, the molar ratio of ethanol to water is 1.5:1 to 2.5:

1.

4. The preparation method according to claim 1, characterized in that: In step (b), the stirring time is at least 30 minutes.

5. The preparation method according to claim 1, characterized in that: In step (b), The molar ratio of the chelating agent to the total molar ratio of the three metal salts is 2:3 to 1:

6.

6. The preparation method according to claim 1, characterized in that: In step (c), The molar amount of the gelling agent is 4 to 6 times the total molar amount of the three metal salts.

7. The preparation method according to claim 1, characterized in that: In step (c), the temperature of the second stirring is 25~30℃, and the stirring time is more than 1 minute.

8. The preparation method according to claim 1, characterized in that: In step (d), the aging time for the first stage is 24-48 hours; the aging time for the second stage is 24-72 hours. In step (e), the drying time is more than 24 hours, and the drying method is drying in a forced-air drying oven at 80°C or freeze drying.

9. An oxygen evolution reaction catalyst prepared by the method according to any one of claims 1-8, characterized in that, The catalyst uses a bimetallic layered hydroxide M1M2LDH as its structural matrix, and a doping element M is introduced into the structural matrix; the doping amount of M in the catalyst is 1~15 at.% of the total molar amount of the three metals, and the molar ratio of M1 to M2 is 3:1~4:1; the particle size of the catalyst is less than 5 nm.

10. The application of the oxygen evolution reaction catalyst according to claim 9 in the electrolysis of water to produce hydrogen.

Images