A surface-reconstructed heterojunction catalyst, its preparation method and application

Abstract

This invention belongs to the field of catalyst technology, and relates to a surface-reconstructed heterojunction catalyst, its preparation method, and its application. The preparation method includes the following steps: dissolving cobalt salt, iron salt, and praseodymium salt in deionized water, heating and spraying the solution onto a support to obtain praseodymium-doped cobalt-iron layered double hydroxide; mixing the praseodymium-doped cobalt-iron layered double hydroxide with a phosphorus source and calcining under an inert atmosphere to obtain praseodymium-doped CoP / Fe2P; and subjecting the praseodymium-doped CoP / Fe2P to electro-oxidation treatment to obtain Pr6O. 11 Cluster-modified CoFeOOH heterojunction catalysts. Through the synergistic application of spray thermal deposition-phosphating-electrooxidation techniques, stable construction and electrochemical activation of the heterojunction interface were achieved, significantly improving the catalyst's corrosion resistance and resistance to chlorine evolution competition in chlorine-containing alkaline systems. An overpotential of only 223 mV was required to reach 100 mA·cm⁻¹. ‑2 The current density is maintained at a stable level for 500 hours.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a surface-reconstructed heterojunction catalyst, its preparation method, and its application. Background Technology

[0002] With the continued growth of global energy demand and the dwindling resources of fossil fuels, hydrogen energy, due to its high energy density and zero carbon emissions from combustion, is considered one of the important carriers of a sustainable energy system. Electrocatalytic water splitting technology for hydrogen production, based on renewable energy sources such as solar and wind power, is considered a highly promising hydrogen production route due to its clean and pollution-free process. However, this technology still faces two major challenges: first, the oxygen evolution reaction (OER), as a four-electron transfer process, has slow kinetics, leading to high overpotentials that severely limit energy conversion efficiency; second, traditional water electrolysis relies on freshwater resources, directly conflicting with the global freshwater shortage.

[0003] Seawater accounts for over 97% of the Earth's water resources. If it could be directly used for hydrogen production through electrolysis, it would effectively alleviate the pressure on raw material supply. However, seawater has a complex composition, including a high concentration of chloride ions (Cl-). - At an anolytical potential of approximately 0.5 M, a competitive chlorine evolution reaction (CER) can occur, which not only reduces the Faraday efficiency of hydrogen production but may also generate corrosive chlorine gas and other byproducts. Furthermore, Cl... - Most electrocatalysts are highly corrosive, easily causing dissolution of active sites, structural collapse, or permanent deactivation, severely affecting the service life of the materials. Therefore, developing catalysts that can combine high OER activity, high CER selectivity, and excellent resistance to chloride ion corrosion in seawater environments has become a key issue in promoting the development of seawater electrolysis hydrogen production technology.

[0004] In recent years, transition metal-based compounds such as sulfides, phosphides, and selenides have become a promising class of candidate materials due to their tunable electronic structures, high intrinsic activity, and well-defined active centers. However, these materials face significant challenges in the complex and corrosive real-world seawater system: the presence of Cl in seawater... - and hypochlorite (ClO) that may be generated during the anodic reaction - Strong oxidizing species such as α, β, and γ can irreversibly erode the active phase of the catalyst, causing the dissolution of metal centers such as Ni, Co, and Fe and the collapse of the crystal lattice structure, leading to rapid performance degradation. Meanwhile, the Ca in seawater... 2+ Mg 2+Alkaline earth metal ions and dissolved organic matter tend to deposit on the electrode surface, forming a passivation layer that covers active sites and hinders mass transport, significantly reducing reaction efficiency. Furthermore, under strongly alkaline and high-potential operating conditions, non-metallic elements such as sulfur, phosphorus, and selenium are thermodynamically unstable and prone to oxidation, dissolution, or phase transitions. This leads to uncontrollable reconstruction or even phase separation on the catalyst surface, making it difficult to maintain long-term chemical and structural stability and limiting its practical application prospects. Summary of the Invention

[0005] The purpose of this invention is to provide a surface-reconstructed heterojunction catalyst, its preparation method, and its application, thereby overcoming the shortcomings of the prior art. By synergistically employing three technologies—spray thermal deposition, phosphating, and electro-oxidation—in-situ regulation of the interface between rare earth oxides and transition metal hydroxyl oxides is achieved. By utilizing the valence state adjustment of Pr and the oxygen vacancy effect, the electronic structure is optimized and the resistance to chlorine corrosion is enhanced, thus endowing the catalyst with high activity and excellent stability.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing a surface-reconstructed heterojunction catalyst, comprising the following steps:

[0008] A precursor solution was prepared by dissolving cobalt salt, iron salt and praseodymium salt in deionized water;

[0009] The precursor solution was heated and sprayed onto a carrier to prepare praseodymium-doped cobalt-iron layered double hydroxide.

[0010] Praseodymium-doped cobalt-iron layered double hydroxide was mixed with a phosphorus source and calcined under an inert atmosphere to obtain praseodymium-doped CoP / Fe2P.

[0011] Pr6O was prepared by electro-oxidation of praseodymium-doped CoP / Fe2P. 11 Cluster-modified CoFeOOH heterojunction catalyst.

[0012] This invention utilizes a synergistic approach of spray thermal deposition, phosphating, and electro-oxidation to construct Pr6O in situ. 11 Cluster / CoFeOOH heterojunction catalyst. By utilizing the valence state adjustment of Pr and the oxygen vacancy effect, the electronic structure is optimized and the resistance to chlorine corrosion is enhanced, thereby endowing the catalyst with high activity and excellent stability. The catalyst exhibits a low overpotential and Tafel slope in the seawater electrochemical oxygen evolution reaction (OER) and maintains stable output at high current densities.

[0013] In some other embodiments, the molar ratio of cobalt salt, iron salt, and praseodymium salt is 4:4:(1-3), and the concentration of praseodymium salt in the precursor solution is 1×10⁻⁶. -3 -3×10 -3 mol·L-1 ;

[0014] The cobalt salt is one or more of cobalt nitrate, cobalt sulfate, and cobalt chloride;

[0015] Iron salts are one or more of ferric nitrate, ferric sulfate, and ferric chloride;

[0016] Praseodymium salts are one or more of praseodymium nitrate, praseodymium sulfate, and praseodymium chloride.

[0017] Specifically, the molar ratio of cobalt salt, iron salt, and praseodymium salt is 4:4:1, 4:4:2, or 4:4:3, and the concentration of praseodymium salt in the precursor solution is 1×10⁻⁶. -3 2×10 -3 Or 3×10 -3 mol·L -1 ;

[0018] The inventors discovered that the Pr doping ratio has a crucial impact on the regulation of interfacial electronic structure and the selectivity of OER reaction. By precisely controlling the molar ratio of Pr to Co and Fe in the precursor solution, the degree of Pr embedding in the crystal lattice and the oxygen vacancy concentration can be effectively adjusted, thereby optimizing the electron distribution and the adsorption intensity of active sites.

[0019] Before the heated spraying, the carrier is pretreated. The carrier pretreatment method is to ultrasonically clean it in ethanol and deionized water for 5-15 min in sequence to remove surface impurities and organic matter, then ultrasonically treat it in 2-4 mol / L HCl solution for 5-15 min, and finally rinse it with deionized water and dry it with argon gas.

[0020] Specifically, the substrate is a nickel mesh or a copper mesh. More specifically, the substrate is a nickel mesh.

[0021] In some other embodiments, the temperature of the heated spraying is 300-400 ℃, and the heated spraying adopts a cyclic spraying process of spraying for 1-3 seconds and stopping for 3-5 seconds, with a total spraying time of 8-12 minutes.

[0022] Specifically, the heating spraying temperature is 300, 350, or 400 °C, and the heating spraying adopts a cyclic spraying process of spraying for 1, 2, or 3 seconds and stopping for 3, 4, or 5 seconds, with a total spraying time of 8, 10, or 12 minutes. Within this range, the precursor solution can be rapidly and uniformly deposited on the carrier, and its non-equilibrium solidification process helps to form ultrafine crystalline or amorphous structures, increasing the reactivity and creating favorable conditions for the subsequent phosphating process.

[0023] In some other embodiments, the mass ratio of praseodymium-doped cobalt-iron layered double hydroxide to phosphorus source is 1:(1-20);

[0024] The phosphorus source is either sodium hypophosphite or triphenylphosphine.

[0025] In some other embodiments, the heating rate of calcination is 3-5 °C·min. -1 The calcination temperature is 250-350℃, and the calcination time is 1.5-2.5 h.

[0026] Specifically, the heating rate for calcination is 3, 4, or 5 °C·min. -1 The calcination temperature is 250, 300 or 350 ℃, and the calcination time is 1.5, 2 or 2.5 h.

[0027] In some other embodiments, the current density applied during the electro-oxidation treatment is 50-200 mA cm⁻¹. -2 The application time range is 1-3 hours.

[0028] Specifically, the current density applied during the electro-oxidation treatment is 50, 100, 150, or 200 mA cm⁻¹. -2 The application time range is 1, 2 or 3 hours.

[0029] A stable phosphide framework is constructed through high-temperature phosphating, followed by precise surface reconstruction via electro-oxidation. Compared to direct synthesis of oxides or hydroxides, this approach yields a richer defect pool, a higher specific surface area, and a more optimized electronic structure. The electro-oxidation process is mild and highly controllable, enabling the segregation and oxidation of Pr elements on the surface to form Pr6O. 11 The clusters simultaneously transform the phosphide core into highly active CoFeOOH, while the internal phosphide can still serve as a highly conductive "skeleton" support, achieving a balance between activity and stability.

[0030] In some other embodiments, praseodymium-doped CoP / Fe2P is used as the working electrode, a graphite rod as the counter electrode, an Ag / AgCl electrode as the reference electrode, and KHCO3 solution as the electrolyte in the electro-oxidation process.

[0031] In a second aspect, the present invention provides a surface-reconstructed heterojunction catalyst prepared by the method for preparing a surface-reconstructed heterojunction catalyst as described in the first aspect, comprising a CoFeOOH heterojunction matrix and Pr6O supported on its surface. 11 Cluster.

[0032] CoFeOOH serves as the substrate, providing a strong main active site for the oxygen evolution reaction; while the Pr6O2 reconstructed on the surface... 11 Clusters can effectively regulate the electronic structure of CoFeOOH, reduce the reaction energy barrier, and preferentially adsorb hydroxide ions, effectively competing with and inhibiting chloride ion erosion and side reactions, thereby jointly improving the activity and selectivity of the catalyst.

[0033] In some other embodiments, the surface-reconstructed heterojunction catalyst has a three-dimensional nanosheet structure with a particle size of 150-250 nm.

[0034] Thirdly, the present invention provides the application of the surface-reconstructed heterojunction catalyst described in the second aspect in seawater oxidation.

[0035] The beneficial effects of this invention are:

[0036] (1) In-situ regulation of the interface between rare earth oxides and transition metal hydroxy oxides is achieved by spray thermal deposition-phosphating-electrooxidation synergistic technology. By utilizing the valence state adjustment of Pr element and oxygen vacancy effect, the electronic structure is optimized and the resistance to chlorine corrosion is enhanced, thereby endowing the catalyst with high activity and excellent stability.

[0037] (2) Praseodymium-doped CoP / Fe2P nanoparticles are reconstructed in situ under oxidation potential. The grains melt and are reorganized into a three-dimensional nanosheet structure with a diameter of about 200 nm. This structure is beneficial for electrolyte penetration, rapid release of bubbles and transport of reaction intermediates.

[0038] (3) By systematically controlling the Pr doping ratio and the parameters of the phosphating and electro-oxidation processes, the stable construction and electrochemical activation of the heterostructure were achieved, significantly improving the catalyst's corrosion resistance and chlorine evolution resistance in chlorine-containing alkaline systems. Only an overpotential of 223 mV was required to reach 100 mA·cm⁻¹. -2 The current density is maintained at a stable level for 500 hours. Attached Figure Description

[0039] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0040] Figure 1 Pr prepared in Example 2 0.2 - Scanning electron microscope (SEM) image, high-resolution transmission electron microscope (HRTEM) image, and fast Fourier transform (FFT) spectrum of CoP / Fe2P material, where a is the SEM image at a 1 μm scale, b is the HRTEM image, c is the FFT spectrum of Fe2P, d is the FFT spectrum of CoP, e is the lattice spacing diagram of Fe2P, and f is the lattice spacing diagram of CoP.

[0041] Figure 2 CoP / Fe2P and Pr prepared in Comparative Example 1 and Example 2, respectively. 0.2- X-ray photoelectron spectra of CoP / Fe2P materials, where a is the Co 2p spectrum, b is the Fe 2p spectrum, c is the Pr 3d spectrum, d is the O 1s spectrum, and e is the P 2p spectrum;

[0042] Figure 3 Pr6O prepared in Example 2 11 Scanning electron microscope (SEM) image and aberration-corrected transmission electron microscope (TEM) image of the -CoFeOOH-0.2 catalyst, where a is the SEM image and b is the aberration-corrected TEM image;

[0043] Figure 4 Pr prepared in Example 2 0.2 -CoP / Fe2P and Pr6O 11 The high-resolution photoelectron spectrum of -CoFeOOH-0.2, where a is the Co 2p spectrum, b is the Fe 2p spectrum, c is the Pr 3d spectrum, d is the O 1s spectrum, and e is the P 2p spectrum;

[0044] Figure 5 Linear sweep voltammetry curves, overpotential graphs, and Tafel slope graphs of the catalysts prepared in Examples 1-3 and Comparative Examples 1 and 7 in 1M KOH are shown, where a is the linear sweep voltammetry curve, b is the overpotential graph, and c is the Tafel slope graph.

[0045] Figure 6 The graphs show the oxidation performance of the catalysts of Example 2, Comparative Examples 1 and 7 in simulated seawater, where a is the linear sweep voltammetry curve, b is the overpotential curve, c is the polarization curve of the catalyst of Example 2 in simulated seawater, and d is the stability test curve of the catalyst of Example 2.

[0046] Figure 7 The figures are cyclic voltammetry curves, electrochemical double-layer capacitance diagrams, and impedance diagrams of the catalysts prepared in Examples 1-3 and Comparative Example 1, respectively. Specifically, a is the cyclic voltammetry curve of Comparative Example 1, b is the cyclic voltammetry curve of Example 1, c is the cyclic voltammetry curve of Example 2, d is the cyclic voltammetry curve of Example 3, e is the electrochemical double-layer capacitance diagram, and f is the impedance diagram. Detailed Implementation

[0047] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Specific conditions not specified in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Components whose manufacturers are not specified are all commercially available conventional products.

[0048] Example 1

[0049] A surface reconstruction of Pr6O11 / CoFeOOH heterojunction catalyst and its preparation method, including the following steps:

[0050] S1: Dissolve 0.4 mmol Co(NO3)2, 0.1 mmol PrN3O9·6H2O and 0.4 mmol Fe(NO3)3·H2O in 100 mL of deionized water in sequence, and stir continuously for 1 h until the solution is homogeneous to obtain a mixed precursor solution.

[0051] S2: Transfer the mixed precursor solution to the reservoir of the spray device, adjust the carrier gas pressure to 0.3 Mbar, and spray it onto the surface of the nickel mesh at 300℃ according to a cycle of 2 seconds of spraying followed by 4 seconds of rest. The total spraying time is 10 minutes, ultimately forming a uniform Pr coating on the surface of the nickel mesh. 0.1 -CoFe layered double hydroxides (LDH) film, labeled Pr 0.1 -CoFe-LDH thin film;

[0052] S3: Pr obtained in step S2 0.1 The -CoFe-LDH film was placed in a ceramic boat and transferred to the isothermal zone of a tube furnace, with 0.8 g of NaH2PO2·H2O placed in the upstream zone as a phosphorus source. Subsequently, under an argon atmosphere, it was heated at 4 ℃·min. -1 The temperature is increased to 300℃ using a programmed heating rate and held for 2 hours. The resulting material is labeled as Pr. 0.1 -CoP / Fe2P.

[0053] S4: Pr obtained in step S3 0.1 A three-electrode system was constructed using a CoP / Fe₂P electrode as the working electrode, a graphite rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode. 100 mL of 1 M KHCO₃ solution was added to the electrolytic cell as the electrolyte. Electrochemical treatment was performed on an electrochemical workstation, applying an electrode pressure of 100 mA cm⁻¹. -2 Electro-oxidation was performed at a current density of [value missing] for 1 hour. The final catalyst was labeled as Pr6O. 11 -CoFeOOH-0.1.

[0054] Example 2

[0055] A surface reconstruction of Pr6O 11The / CoFeOOH heterojunction catalyst and its preparation method differ from Example 1 in that: in step S1, PrN3O9·6H2O is 0.2 mmol, that is, 0.4 mmol Co(NO3)2, 0.2 mmol PrN3O9·6H2O, and 0.4 mmol Fe(NO3)3·H2O are dissolved sequentially in 100 mL of deionized water solution, and stirred continuously for 1 h until the solution is uniformly mixed to obtain a mixed precursor solution; other preparation steps are the same as in Example 1. The material obtained in step S3 is labeled as Pr 0.2 -CoP / Fe2P. The catalyst obtained in step S4 is labeled as Pr6O. 11 -CoFeOOH-0.2.

[0056] Example 3

[0057] A surface reconstruction of Pr6O 11 The / CoFeOOH heterojunction catalyst and its preparation method differ from Example 1 in that: in step S1, the amount of PrN3O9·6H2O is 0.3 mmol, that is, 0.4 mmol Co(NO3)2, 0.3 mmol PrN3O9·6H2O, and 0.4 mmol Fe(NO3)3·H2O are dissolved sequentially in 100 mL of deionized water solution, and stirred continuously for 1 h until the solution is homogeneous to obtain a mixed precursor solution; other preparation steps are the same as in Example 1. The material obtained in step S3 is labeled as Pr 0.3 -CoP / Fe2P. The catalyst obtained in step S4 is labeled as Pr6O. 11 -CoFeOOH-0.3.

[0058] Comparative Example 1

[0059] A CoFeOOH heterojunction catalyst and its preparation method differ from Example 1 in that: in step S1, the addition of PrN3O9·6H2O is omitted; instead, 0.4 mmol Co(NO3)2 and 0.4 mmol Fe(NO3)3·H2O are dissolved sequentially in 100 mL of deionized water, and the mixture is stirred continuously for 1 h until the solution is homogeneous, thus obtaining a mixed precursor solution; the other preparation steps are the same as in Example 1. The material obtained in step S3 is labeled as CoP / Fe2P. The catalyst finally obtained in step S4 is labeled as CoFeOOH.

[0060] Comparative Example 2

[0061] A catalyst and its preparation method differ from Example 1 in that: in step S1, the addition of PrN3O9·6H2O and Co(NO3)2 is omitted; instead, 0.4 mmol Fe(NO3)3·H2O is dissolved in 100 mL of deionized water, and the solution is stirred continuously for 1 h until it is homogeneous, thus obtaining a mixed precursor solution; the other preparation steps are the same as in Example 1. The final catalyst is labeled FeOOH.

[0062] Comparative Example 3

[0063] A catalyst and its preparation method differ from Example 1 in that: in step S1, the addition of PrN3O9·6H2O and Fe(NO3)3·H2O is omitted; instead, 0.4 mmol Co(NO3)2 is dissolved in 100 mL of deionized water and stirred continuously for 1 h until the solution is homogeneous, thus obtaining a mixed precursor solution; the other preparation steps are the same as in Example 1. The final catalyst is labeled as CoOOH.

[0064] Comparative Example 4

[0065] A catalyst and its preparation method, comprising the following steps:

[0066] Unlike Example 1, step S1 omits the addition of Co(NO3)2 and Fe(NO3)3·H2O. Instead, 0.1 mmol PrN3O9·6H2O is dissolved in 100 mL of deionized water and stirred continuously for 1 h until the solution is homogeneous, thus obtaining a mixed precursor solution. Other preparation steps are the same as in Example 1. The final catalyst is labeled as Pr6O. 11 .

[0067] Comparative Example 5

[0068] A catalyst and its preparation method, comprising the following steps:

[0069] Unlike Example 1, in step S1, 0.4 mmol Co(NO3)2 was replaced with an equal amount of 0.4 mmol Mn(NO3)2. Specifically, 0.4 mmol Mn(NO3)2, 0.1 mmol PrN3O9·6H2O, and 0.4 mmol Fe(NO3)3·H2O were sequentially dissolved in 100 mL of deionized water and stirred continuously for 1 h until the solution was homogeneous, thus obtaining a mixed precursor solution. Other preparation steps were the same as in Example 1. The final catalyst was labeled as Pr6O. 11 -MnFeOOH-0.1.

[0070] Comparative Example 6

[0071] A catalyst and its preparation method, comprising the following steps:

[0072] Unlike Example 1, in step S1, 0.4 mmol Co(NO3)2 was replaced with 0.2 mmol Co(NO3)2 and 0.2 mmol Ni(NO3)2. Specifically, 0.2 mmol Co(NO3)2, 0.2 mmol Ni(NO3)2, 0.1 mmol PrN3O9·6H2O, and 0.4 mmol Fe(NO3)3·H2O were sequentially dissolved in 100 mL of deionized water and stirred continuously for 1 h until the solution was homogeneous, thus obtaining a mixed precursor solution. Other preparation steps were the same as in Example 1. The final catalyst was labeled as Pr6O. 11 -NiCoFeOOH-0.1.

[0073] Comparative Example 7

[0074] Commercial RuO2 was used as the catalyst.

[0075] The catalyst materials prepared in the above examples and comparative examples were characterized as follows:

[0076] (1) Composition and structural characterization: The morphology and structure of the prepared catalysts were analyzed using field emission scanning electron microscopy (SEM, ZEISS Gemini SEM300, Germany), transmission electron microscopy (TEM, JEM-2100F), and high-angle annular dark-field scanning transmission electron microscopy with spherical aberration correction (HAADF-STEM, JEOL JEM-ARM300F). X-ray photoelectron spectroscopy (XPS, ESCALAB 250) was used to characterize the catalyst components.

[0077] Figure 1 Pr prepared in Example 2 0.2 - Scanning electron microscope (SEM) images, high-resolution transmission electron microscope (HRTEM) images, and fast Fourier transform (FFT) spectra of CoP / Fe2P materials. Where a is the SEM image at a 1 μm scale, b is the HRTEM image, c is the FFT spectrum of Fe2P, d is the FFT spectrum of CoP, e is the lattice spacing diagram of Fe2P, and f is the lattice spacing diagram of CoP. (Example:) Figure 1 As shown in 'a', the CoP / Fe2P material consists of uniformly distributed nanoparticles. High-resolution transmission electron microscopy (TEM) images and their corresponding fast Fourier transform spectra (FFT) are presented. Figure 1 The bd in the figure further confirms the successful formation of the CoP and Fe2P crystal phases. Among them, the lattice spacing of 0.206 nm belongs to the (111) crystal plane of CoP. Figure 1 The 0.226 nm lattice fringes are consistent with the (111) crystal plane characteristics of Fe2P. Figure 1(f in the text). The close contact between these two phosphide grains indicates the formation of a heterostructure with abundant interfaces, which is beneficial for promoting electron transport during electrocatalysis.

[0078] Figure 2 CoP / Fe2P and Pr prepared in Comparative Example 1 and Example 2, respectively. 0.2 - X-ray photoelectron spectra of CoP / Fe2P materials, where a is the Co 2p spectrum, b is the Fe 2p spectrum, c is the Pr 3d spectrum, d is the O 1s spectrum, and e is the P 2p spectrum.

[0079] Depend on Figure 2 As can be seen from 'a' in the high-resolution Co 2p spectrum of the CoP / Fe2P material, the binding energy peaks at 778.0 eV and 791.7 eV are attributed to Co, respectively. 3+ 2p 3 / 2 With 2p 1 / 2 The double peaks at 781.8 eV and 795.3 eV correspond to Co. 2+ 2p 3 / 2 With 2p 1 / 2 Each main peak is accompanied by a distinct satellite peak. Figure 2 (a) In the Fe 2p spectrum, the peaks at 712.13 eV and 723.45 eV belong to Fe. 2+ 2p 3 / 2 With 2p 1 / 2 The signals at 714.18 eV and 726.34 eV belong to Fe. 3+ 2p 3 / 2 With 2p 1 / 2 Fe was observed at 709.97 eV and 719.77 eV. 0 Characteristic peaks of the species. Specifically, Pr modified with Pr. 0.2 In CoP / Fe2P, the Co 2p binding energy shifts positively by 0.15 eV, while the Fe 2p binding energy shifts negatively by 0.26 eV. Figure 2 (b) indicates that the introduction of Pr effectively modulates the electronic structure of the Co and Fe sites, inducing an electronic synergistic effect between them. Pr 3d spectrum ( Figure 2 c) further shows that Pr mainly exists in a mixed valence state of +3 (929.97, 935.09, 949.92, 955.15 eV) and +4 (932.70, 952.98 eV). In addition, characteristic peaks are located near 531.36 eV and 532.85 eV in the O 1s spectrum (…). Figure 2 In the spectrum, d) can be attributed to oxygen vacancies and adsorbed oxygen species. The slight shift in the spectrum reflects the effect of Pr modification on the local oxygen coordination environment. (P 2p spectrum) Figure 2The double peaks at 129.45 eV and 130.17 eV in e) correspond to P 2p, respectively. 3 / 2 With P 2p 1 / 2 This confirmed the formation of MP bonds (M being Pr, Co, and Fe), with the broad peak near 133.92 eV originating from PO species formed by surface oxidation.

[0080] Figure 3 Pr6O prepared in Example 2 11 Scanning electron microscope (SEM) image and aberration-corrected transmission electron microscope (TEM) image of the -CoFeOOH-0.2 catalyst, where a is the SEM image and b is the aberration-corrected TEM image.

[0081] like Figure 3 As shown in a, Pr6O 11 -CoFeOOH-0.2 exhibits a nanosheet-like structure. Pr is uniformly distributed on the surface of the nickel mesh. 0.2 -CoP / Fe2P nanoparticles underwent in-situ reconstruction at the operating oxidation potential, resulting in crystallization and recombination into a three-dimensional nanosheet structure with a diameter of approximately 200 nm. This structure facilitates electrolyte penetration, rapid bubble release, and the transport of reaction intermediates. (Image from aberration-corrected transmission electron microscopy) Figure 3 Further observation of b in the figure revealed clear lattice fringes. The interplanar spacings of 0.230 nm and 0.225 nm corresponded to the CoOOH (111) and FeOOH (121) crystal planes, respectively. Meanwhile, the interplanar spacings of 0.27 nm and 0.31 nm were attributed to Pr6O... 11 The (200) and (111) crystal planes, with an included angle of approximately 55°, indicate that Pr 0.2 –CoP / Fe2P undergoes surface reconstruction to form Pr6O during OER. 11 Cluster-loaded CoFeOOH heterostructure.

[0082] Figure 4 Pr prepared in Example 2 0.2 -CoP / Fe2P and Pr6O 11 The high-resolution photoelectron spectrum of -CoFeOOH-0.2, where a is the Co 2p spectrum, b is the Fe 2p spectrum, c is the Pr 3d spectrum, d is the O 1s spectrum, and e is the P 2p spectrum.

[0083] Depend on Figure 4 As can be seen from 'a', the Co 2p spectrum shows Co 3+ The signal is significantly enhanced, indicating that the cobalt species were oxidized to a higher valence state during the reaction. (Pr6O) 11 -CoFeOOH-0.2 of Co 2p and Fe 2p ( Figure 4The binding energies of a) and b) in the Pr 3d spectrum shift positively by 0.49 eV and 0.61 eV, respectively, further confirming the enhancement of the oxidation state of the metal center. Notably, in the Pr 3d spectrum... 4+ The proportion of species increased significantly, and the spectral peaks shifted overall towards higher binding energies. Figure 4 c), indicating Pr 3+ During the reaction, electrons were donated to the Co / Fe active sites, and this electron transfer effect effectively inhibited Co. 3+ and Fe 3+ Excessive oxidation and metal dissolution. For example... Figure 4 As shown in d, Pr 0.2 The characteristic peaks of -CoP / Fe2P at 531.41 eV and 532.11 eV correspond to oxygen vacancies and adsorbed water, respectively. A new peak appears at 529.97 eV after the OER reaction, consistent with the formation of M-OH species. Simultaneously, the MP bond signal in the P2p spectrum is significantly weakened. Figure 4 The results (e) confirm the reconstruction process driven by the breaking of surface MP bonds. These results collectively reveal that Pr doping synergistically enhances the catalyst's oxidation tolerance and structural stability by regulating electron transfer and promoting surface hydroxylation reconstruction.

[0084] (2) Characterization of oxygen evolution reaction activity: Pr6O was evaluated in 1 M KOH electrolyte using a standard three-electrode system. 11 Oxygen evolution reaction activity of the -CoFeOOH-x (0.1, 0.2, 0.3) series catalysts. Figure 5 Linear sweep voltammetry curves, overpotential graphs, and Tafel slope graphs of the catalysts prepared in Examples 1-3, Comparative Examples 1, and Comparative Examples 7 in 1 M KOH are shown, where a is the linear sweep voltammetry curve, b is the overpotential graph, and c is the Tafel slope graph.

[0085] like Figure 5 As shown in a and b, Pr6O 11 -CoFeOOH-0.2 exhibited the highest current density across the entire test potential range, at 100 mA cm⁻¹. -2 At current density, the required overpotential is minimal, requiring only 223 mV to drive 100 mA·cm. -2 The current density has a Tafel slope of 46.9 mV·dec. -1 ( Figure 5 (as shown in c), which is the lowest value among the catalysts in this series, indicating that it has faster OER reaction kinetics.

[0086] Figure 6The graphs show the oxidation performance of the catalysts in simulated seawater for Comparative Examples 1, 7, and 2, where a is a linear sweep voltammetry curve, b is an overpotential curve, c is a polarization curve of the catalyst in simulated seawater, and d is a stability test curve of the catalyst in Example 2.

[0087] Depend on Figure 6 From a and b in the data, we can see that in simulated seawater (1M KOH + 0.5M NaCl), Pr6O 11 -CoFeOOH-0.2 exhibits the highest current density, superior to CoFeOOH and RuO2 catalysts, at 100 mA·cm⁻¹. -2 It requires the lowest overpotential at the current density. To further evaluate its industrial application potential, a Pr6O4-based system was constructed. 11 Using CoFeOOH-0.2 as the anode and Pt / C as the cathode, an anion exchange membrane electrolyzer is assembled. In a 1 M KOH electrolyte, this electrolyzer requires only 2.0 V of cell voltage to achieve 0.5 A·cm⁻¹. -2 The current density of Pr6O2 significantly outperforms that of the commercial Pt / C||RuO2 reference system (2.4 V). Under simulated industrial conditions (30 wt% KOH, 85 °C), the operating voltage is further reduced to 1.86 V. Adding sodium chloride to the electrolyte to simulate a seawater environment only increases the cell voltage by 30 mV, indicating that Pr6O2 exhibits superior performance. 11 -CoFeOOH-0.2 possesses excellent catalytic activity and structural stability in seawater electrolysis. Figure 6 (c) The long-term stability was evaluated using the chronopotential method at 100 mA·cm⁻¹. -2 After 500 hours of continuous operation at current density, the overpotential remained almost unchanged. Figure 6 (d) exhibits excellent durability.

[0088] Figure 7 The figures are cyclic voltammetry curves, electrochemical double-layer capacitance diagrams, and impedance diagrams of the catalysts prepared in Examples 1-3 and Comparative Example 1, respectively. Specifically, a is the cyclic voltammetry curve of Comparative Example 1, b is the cyclic voltammetry curve of Example 1, c is the cyclic voltammetry curve of Example 2, d is the cyclic voltammetry curve of Example 3, e is the electrochemical double-layer capacitance diagram, and f is the impedance diagram.

[0089] Depend on Figure 7 The CV curves of the catalyst in ad in the non-Radida potential range are used to calculate the double-layer capacitance (C). dl )(like Figure 7 (as shown in f), Pr6O 11 -CoFeOOH-0.2 of C dl The maximum value is 2.99 mF·cm. -2This indicates that it has the largest electrochemically active surface area, exposing more OER active sites. Electrochemical impedance spectroscopy is shown in the figure. Figure 7 As shown in e, the semicircle diameter of the Nyquist plot for all Pr-doped catalysts is smaller than that for undoped CoFeOOH, where Pr6O 11 The semicircle diameter of -CoFeOOH-0.2 is the smallest, indicating its charge transfer resistance (R0.2). ct It has the lowest [value] and the optimal interfacial charge transport dynamics.

[0090] The long-term stability of the catalysts prepared in Examples 1-3 and Comparative Examples 1-7 was evaluated by chronopotentiometric method at 100 mA·cm⁻¹. -2 The system was continuously operated at current density, and its operational stability was tested by measuring overpotential and operating time. The test results are shown in Table 1.

[0091] Table 1 shows the electrochemical performance test results.

[0092]

[0093] As shown in Table 1, Example 2 has the lowest overpotential and the longest stable operating time, exhibiting the best overall performance.

[0094] Compared to Example 2, Example 1 reduced the Pr doping amount, resulting in an increased overpotential and decreased stability, possibly because insufficient Pr content weakened the regulation of the electronic structure of the transition metal. Compared to Example 2, Example 3 increased the Pr doping amount, resulting in an increased overpotential and decreased stability, possibly because excessive Pr caused lattice distortion and restricted charge migration.

[0095] Compared to Example 2, Comparative Example 1, lacking Pr doping, resulted in increased overpotential and decreased stability, possibly due to the absence of rare-earth element f orbital-induced electron rearrangement. Comparative Example 2, compared to Example 2, lacking Co component and Pr regulation, also resulted in increased overpotential, possibly due to the strong adsorption energy of the FeOOH system for reaction intermediates, limiting the oxygen generation step. Comparative Example 3, compared to Example 2, lacking Fe component and Pr doping, also resulted in increased overpotential, possibly due to the simple electronic structure of active sites and weak adsorption energy of OER intermediates, limiting intermediate formation. Comparative Example 4, compared to Example 2, containing only Pr oxide as the main body, resulted in a significantly increased overpotential, possibly due to poor conductivity and a lack of transition metal active centers. Comparative Example 5, compared to Example 2, showed decreased performance after Mn substitution for Co, leading to increased overpotential, possibly due to structural defects and electrochemical activity degradation caused by Mn valence instability. Comparative Example 6, compared to Example 2, showed weakened synergistic effects due to multi-metal co-doping, leading to increased overpotential, possibly due to uneven electronic coupling between heterogeneous metals and hindered interfacial charge transfer. Compared with Example 2, Comparative Example 7 lacks Pr-CoFe interface synergy, resulting in an increase in overpotential, possibly due to the lack of df orbital hybridization between rare earth and transition metals.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a surface-reconstructed heterojunction catalyst, characterized in that, Includes the following steps: A precursor solution was prepared by dissolving cobalt salt, iron salt and praseodymium salt in deionized water; The precursor solution was heated and sprayed onto a carrier to prepare praseodymium-doped cobalt-iron layered double hydroxide. Praseodymium-doped cobalt-iron layered double hydroxide was mixed with a phosphorus source and calcined under an inert atmosphere to obtain praseodymium-doped CoP / Fe2P. Pr6O was prepared by electro-oxidation of praseodymium-doped CoP / Fe2P. 11 Cluster-modified CoFeOOH heterojunction catalysts; The molar ratio of the cobalt salt, iron salt and praseodymium salt is 4:4:(1-3); The mass ratio of the praseodymium-doped cobalt-iron layered double hydroxide to the phosphorus source is 1:(1-20); The calcination temperature is 250-350 ℃; The temperature of the heated spraying is 300-400 ℃, and the heated spraying adopts a cyclic spraying process of spraying for 1-3 seconds and stopping for 3-5 seconds, with a total spraying time of 8-12 minutes.

2. The method for preparing the surface-reconstructed heterojunction catalyst according to claim 1, characterized in that, The concentration of praseodymium salt in the precursor solution is 1×10⁻⁶. -3 -3×10 -3 mol·L -1 ; The cobalt salt is one or more of cobalt nitrate, cobalt sulfate, and cobalt chloride; The iron salt is one or more of ferric nitrate, ferric sulfate, and ferric chloride; The praseodymium salt is one or more of praseodymium nitrate, praseodymium sulfate, and praseodymium chloride.

3. The method for preparing the surface-reconstructed heterojunction catalyst according to claim 1, characterized in that, The phosphorus source is either sodium hypophosphite or triphenylphosphine.

4. The method for preparing the surface-reconstructed heterojunction catalyst according to claim 1, characterized in that, The heating rate for calcination is 3-5 °C / min. -1 The calcination time is 1.5-2.5 h.

5. The method for preparing the surface-reconstructed heterojunction catalyst according to claim 1, characterized in that, The applied current density for electro-oxidation treatment is 50-200 mA cm⁻¹. -2 The application time is 1-3 hours.

6. The method for preparing the surface-reconstructed heterojunction catalyst according to claim 1, characterized in that, In the electro-oxidation process, praseodymium-doped CoP / Fe2P was used as the working electrode, a graphite rod as the counter electrode, an Ag / AgCl electrode as the reference electrode, and KHCO3 solution as the electrolyte.

7. A surface-reconstructed heterojunction catalyst prepared by the method of any one of claims 1-6, characterized in that, Including the CoFeOOH heterojunction matrix and its surface-loaded Pr6O 11 Cluster.

8. The surface-reconstructed heterojunction catalyst according to claim 7, characterized in that, The surface-reconstructed heterojunction catalyst has a three-dimensional nanosheet structure with a particle size of 150-250 nm.

9. The application of a surface-reconstructed heterojunction catalyst as described in claim 7 or 8 in seawater oxidation.

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