A p, o co-doped fe ni ru ox nano-catalyst, a preparation method and application thereof

Abstract

The application discloses a P and O co-doped FeNiRuOx nano catalyst and a preparation method and application thereof, relates to the technical field of electrocatalytic materials, and the catalyst takes Fe, Ni and Ru as metal active centers, reconstructs a surface electronic structure through P and O double anion co-doping, and forms a polygonal nano structure, wherein the mass fraction ranges of Fe, Ni, Ru and P are 5.0-6.0%, 75-78%, 11-12% and 6.5-7.0% respectively. The preparation method comprises the following steps: taking iron acetylacetone, nickel acetylacetone and ruthenium chloride trihydrate as metal sources, synthesizing a precursor through a solvothermal reaction, and realizing P and O co-doping through a sodium hypophosphite assisted solid-phase phosphorization process, and the preparation process is mild. The synthesized catalyst has unique structural advantages, the formed polygonal nano structure has a large specific surface area and rich grain boundary defects, more active sites are exposed, and convenient channels are provided for the mass transfer of reactants and products. The synergistic effect among the polymetals further enhances the catalytic performance.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, specifically to a P, O co-doped FeNiRuOx nanocatalyst, its preparation method, and its application. Background Technology

[0002] With the deepening of the global energy transition and the "dual-carbon" strategy, hydrogen energy, as a secondary energy source that is abundant, green, low-carbon, and widely applicable, has become an important carrier for building a clean energy system. Among numerous hydrogen production technologies, water electrolysis is considered the most promising green hydrogen production route due to its advantages such as zero carbon emissions and high product purity. The core of this technology lies in the oxygen evolution reaction (OER) at the anode. However, the OER is a complex process involving the transfer of four electrons, with slow kinetics and high overpotential, becoming a key bottleneck restricting the overall energy efficiency and cost of water electrolysis.

[0003] Currently, commercially available OER catalysts are mainly noble metal-based materials, such as ruthenium dioxide (RuO2) and iridium dioxide (IrO2). While these catalysts possess certain catalytic activity, their large-scale application faces significant challenges. First, noble metals are scarce and expensive in the Earth's crust, resulting in high catalyst costs. Second, especially under harsh conditions of high current density and long-term operation, noble metal catalysts are prone to dissolution, aggregation, or oxidation, leading to loss of active sites and rapid performance degradation, making it difficult to meet industrial requirements in terms of stability. Furthermore, RuO2 lacks long-term stability in strongly alkaline environments, while IrO2 binds too strongly to oxygen intermediates, limiting further improvement in its intrinsic activity.

[0004] To overcome the limitations of noble metal catalysts, researchers have turned their attention to non-noble metal catalysts, particularly transition metal-based materials such as iron, nickel, and cobalt. These materials are abundant, inexpensive, and exhibit good OER catalytic potential. However, most non-noble metal catalysts have low intrinsic conductivity, insufficient exposure of active sites, and are prone to forming inactive hydroxide / oxide layers during reaction reconstruction, resulting in a gap in activity and stability compared to noble metal catalysts.

[0005] In recent years, doping with non-metallic elements (such as phosphorus, sulfur, nitrogen, and boron) to modulate the electronic structure of transition metal catalysts has become an effective strategy for improving their OER performance. Among them, phosphorus (P) doping has attracted much attention due to its unique electronic effects (low electronegativity of P can adjust the d-band center of metals and optimize the adsorption energy of oxygen-containing intermediates) and structural effects (inducing lattice distortion and forming defect-rich active interfaces). However, existing phosphating strategies mostly rely on highly toxic precursors (such as PH3) or complex liquid-phase processes, which have problems such as high safety risks, poor process reproducibility, and difficulty in precisely controlling phosphorus doping concentration and local coordination environment. More importantly, in the strongly alkaline OER working environment, the surface of phosphides is easily deeply oxidized to form an inactive phosphate layer, which blocks active sites and leads to rapid catalyst deactivation.

[0006] In summary, developing a novel OER catalyst that combines high activity, high stability, low cost, and a safe and environmentally friendly preparation process is an urgent need to promote the large-scale development of water electrolysis for hydrogen production. By employing a multi-metal synergy and multi-anion co-doping strategy, and precisely controlling the electronic structure and active interface of the catalyst surface, it is hoped that breakthroughs in catalytic performance can be achieved while maintaining the cost advantage of non-precious metals. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a P, O co-doped FeNiRu-based catalyst, its preparation method, and its applications. This catalyst aims to solve the technical problems of high cost and insufficient stability of existing noble metal OER catalysts, as well as the poor activity and conductivity of non-noble metal catalysts, safety risks in traditional phosphating processes, and the easy deactivation of phosphides.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, this invention provides a P,O co-doped FeNiRu-based catalyst. The catalyst possesses a unique polygonal nanostructure, with a chemical composition represented as P,O-FeNiRuOx, wherein P and O, as co-doping elements of two anions, are uniformly distributed within the metal active interface composed of Fe, Ni, and Ru. XRD characterization of this multiphase composite structure reveals the presence of Ni₂P, Fe₂Ni₃, and Ru₄Fe phases, which collectively construct a rich active interface and efficient charge transport channels.

[0009] Secondly, this invention provides a method for preparing the aforementioned P,O co-doped FeNiRu-based catalyst. This method employs a two-step approach to construct the target catalyst, specifically including the following steps: S1. Precursor Synthesis: A one-step solvothermal method is used to react nickel precursors (such as nickel acetylacetonate), ruthenium precursors (such as ruthenium trichloride), and iron precursors (such as iron acetylacetonate) with a specific organic solvent (preferably a mixed solvent of oleylamine and 1-octadecene) at 200-300℃ for 1-3 hours. By precisely controlling the reaction temperature and time, FeNiRuOx precursor nanomaterials with preliminary activity are generated.

[0010] S2. Controlled Phosphating Doping: The precursor obtained in step S1 is thoroughly ground and mixed with a solid phosphorus source (preferably sodium hypophosphite, NaH2PO2), and then placed in a tube furnace. Under an inert protective atmosphere (such as argon or nitrogen), the temperature is programmed to rise to 350-450°C at a heating rate of 2-10°C / min and held for 1-3 hours to carry out a high-temperature phosphating reaction. This step is the key to the present invention. Sodium hypophosphite decomposes under heating to release active phosphorus species. These species not only convert some metal oxides / hydroxides into metal phosphides (such as Ni2P) in situ, but also achieve the doping of P elements into the crystal lattice, forming a stable structure of P and O dual anion synergistic doping with the inherent O elements in the system.

[0011] Thirdly, this invention provides the application of the above-mentioned P, O co-doped FeNiRu-based catalyst in the oxygen evolution reaction (OER) of water electrolysis. The catalyst is particularly suitable for hydrogen production processes via water electrolysis in alkaline environments (including 1 MkOH pure water systems and complex alkaline wastewater systems) and can be used as a high-performance anode catalyst.

[0012] The beneficial effects and outstanding advantages of this invention are as follows: 1. The catalyst synthesized in this invention possesses unique structural advantages. The resulting polygonal nanostructure has a large specific surface area and abundant grain boundary defects, which not only exposes more active sites but also provides convenient channels for mass transfer between reactants and products. The synergistic effect among the multiple metals (Fe, Ni, Ru) further enhances the catalytic performance.

[0013] 2. This invention exhibits superior overall performance in electrochemical testing. In a 1 MkOH pure water system, the catalyst requires only 276 mV overpotential to drive a current density of 10 mA cm⁻², with a Tafel slope as low as 48.07 mV dec⁻¹, significantly outperforming commercial RuO₂. More importantly, in alkaline wastewater simulating a real wastewater environment, its overpotential is only 292 mV @ 10 mA cm⁻², demonstrating strong environmental adaptability. After 100 hours of continuous operation at a current density of 10 mA cm⁻², the performance degradation rate is extremely low (<2.5%), proving its excellent long-term operational stability.

[0014] 3. This invention uses solid sodium hypophosphite as the phosphorus source, completely avoiding the safety risks associated with the use of highly toxic PH3 gas in traditional phosphating processes, ensuring high experimental safety. The entire preparation process requires no complex equipment, has a simple process route, good reproducibility, and is easy to scale up for production. Furthermore, by using a low content of the precious metal Ru in combination with non-precious metals Fe and Ni, high performance is ensured while effectively controlling raw material costs, demonstrating broad prospects for industrial application. Attached Figure Description

[0015] Figure 1 The image shows a TEM image of the P,O-FeNiRuOx catalyst prepared in Example 1 of this invention. Figure 2 The image shows the HAADF-STEM image and elemental distribution of the catalyst in Example 1 of this invention. Figure 3 The XRD pattern of the catalyst in Example 1 of this invention; Figure 4 The X-ray photoelectron spectroscopy (XPS) spectra of the catalyst prepared in Example 1 of this invention include (a) the full spectrum and (b) high-resolution spectra of Fe2p, (c) Ni2p, (d) Ru3p, (e) P2p and (f) O1s. Figure 5 The above is a comparison of the electrochemical performance of the catalyst of Example 1 of the present invention and the comparative sample in 1MKOH pure aqueous electrolyte, including (a) linear sweep voltammetry (LSV) curves, (b) overpotential comparison bar charts extracted based on LSV curves, (c) Tafel slope diagrams and (d) electrochemical impedance spectroscopy (EIS) Nyquist plots. Figure 6 The above is a comparison of the electrochemical performance of the catalyst of Example 1 of the present invention and the comparative sample in 1MKOH alkaline wastewater electrolyte, including (a) LSV curve, (b) overpotential comparison, (c) Tafel slope diagram and (d) EIS spectrum. Figure 7 The stability test curves of the catalyst in 1MKOH pure aqueous electrolyte of Example 1 of the present invention include (a) a comparison of LSV curves before and after 11,000 cyclic voltammetry (CV) tests and (b) a chronopotential (it) curve at a constant current density of 10 mA cm⁻². Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1: P,O-FeNiRuO x Catalyst preparation Precursor (FeNiRuO) x Synthesis of nanoparticles (solvothermal method): 0.2 mM nickel acetylacetone (Ni(acac)2), 0.15 mM ruthenium trichloride trihydrate, and 0.3 mM iron acetylacetone (Fe(acac)3) were weighed as metal sources. 2 mL of oleylamine (OLA) and 10 mL of 1-octadecene (ODE) were measured as a mixed solvent and structure-directing agent and placed in a 250 mL three-necked flask. The mixed solution was heated from room temperature to 250 °C at a constant heating rate of 7 °C / min using a heating mantle. After reaching the target temperature, the solution was refluxed and held for 1 hour. During this process, the solution color gradually changed from initial turbidity to deep black, indicating that the nanoparticles had been successfully formed. After the reaction was completed, the three-necked flask was immediately removed from the heating mantle and allowed to cool naturally at room temperature to approximately 50 °C. Subsequently, the reaction solution was transferred to a centrifuge tube, anhydrous ethanol was added, and the mixture was centrifuged at 9000 rpm for 10 minutes, collecting the black precipitate at the bottom. To thoroughly remove unreacted metal precursors, excess organic solvents, and reaction byproducts, anhydrous ethanol and n-heptane were used as washing agents, each repeated three times by centrifugation. Finally, the resulting black solid was placed in a vacuum drying oven and dried at 40°C for 3 hours to obtain dry, loose FeNiRuO. x Precursor powder, for later use.

[0018] P, O co-doping (solid-phase phosphating treatment): In an agate mortar, 15 mg FeNiRuO x The precursor powder was thoroughly and uniformly mechanically ground and mixed with 60 mg of NaH2PO2 powder. The uniformly ground mixture was carefully transferred to a clean ceramic boat and smoothly pushed into the center of the isothermal heating zone of a horizontal tube furnace. First, the gas path was opened, and high-purity argon gas was introduced into the furnace cavity and continuously purged for 30 minutes to completely remove air (especially oxygen) from the furnace tube, creating an oxygen-free inert reaction environment. Then, the heating program was started, and the temperature was increased from room temperature to the target temperature of 400°C at a constant heating rate of 5°C / min. After reaching 400°C, the temperature was held for 2 hours to carry out the phosphating reaction. After the reaction was completed, the heating power was turned off, and the tube furnace was allowed to cool naturally to room temperature under the protection of a continuous argon gas flow. The resulting black powder is the P,O-FeNiRuO of this invention.x catalyst.

[0019] Systematic physical characterization of the catalyst: TEM ( Figure 1 The XRD results showed that it successfully formed a polygonal nanosheet structure with uniform size and clear outline; Figure 3 The characteristic diffraction peaks of phases such as Ni2P (JCPDS03-0953) and Ru4Fe (JCPDS40-1147) were clearly visible in the spectrum, confirming the successful construction of the multiphase composite structure after phosphating; XPS ( Figure 4 The high-resolution spectra verified the presence of MP bonds (-129.5 eV) and PO bonds (-134.1 eV) in the P2p orbitals, as well as the changes in the chemical valence states of various metal elements, providing direct evidence for the co-doping of P and O dual anions; EDS surface scan ( Figure 2 The spectrum shows that the five elements Fe, Ni, Ru, P and O are highly uniformly distributed and well overlapped inside the nanoparticles, proving the uniform composite at the element level.

[0020] Comparative Example 1: Undoped FeNiRuO x Sample preparation This comparative example aims to demonstrate, by comparing it with an undoped sample, that the subsequent P and O co-doping step is key to the present invention, and that the resulting electronic structure modulation and phase transformation play a decisive role in performance improvement.

[0021] Preparation process: FeNiRuO was synthesized strictly according to the exact same method and parameters (including raw materials, proportions, temperature, time, post-treatment, etc.) as step 1 in Example 1. x Precursor powder.

[0022] Differential treatment: The obtained precursor powder was not subjected to step 2 (i.e., phosphating) in Example 1. A portion was directly taken out for subsequent physical characterization and electrochemical testing. This sample was designated as FeNiRuO. x .

[0023] Comparative Example 2: Commercial Catalyst Samples This comparative example uses commercially available catalysts as a performance benchmark to objectively measure the improvement of the catalyst of this invention compared to current commercial technologies.

[0024] Sample source: Commercial ruthenium dioxide (Com.RuO2) catalyst purchased directly from Maclean Chemical Reagents Ltd.

[0025] Example 2: Electrochemical Performance Testing This embodiment is used to systematically evaluate and compare the OER catalytic activity, kinetics, and conductivity of the samples prepared in Example 1 (the present invention), Comparative Example 1, and Comparative Example 2.

[0026] Working electrode preparation: A rotating disk electrode (RDE) coating method was used. 5.0 mg of each catalyst powder to be tested (including: P,O-FeNiRuO of this invention) was accurately weighed. x Comparative Example 1: FeNiRuO x Comparative Example 2 (Com.RuO2) was mixed with 700 μL of anhydrous ethanol, 290 μL of ultrapure water (18.2 MΩ·cm), and 10 μL of 5 wt% Nafion perfluorinated resin solution, respectively, and placed in 2 mL centrifuge tubes. The mixture was then sonicated for at least 30 minutes until a homogeneous, stable catalyst ink without particle sedimentation was formed. 11.2 μL of the homogeneous ink was transferred and drop-coated onto a glassy carbon rotating disk electrode (GC-RDE, 5 mm in diameter, 0.196 cm²) that had been pre-polished to a mirror finish with alumina polishing powder (50 nm) and ultrasonically cleaned with ultrapure water and ethanol. 2 )surface.

[0027] Test System and Conditions: A standard three-electrode system was used, and all tests were performed on a CHI760e electrochemical workstation. The catalyst / GC-RDE prepared above was used as the working electrode, a platinum sheet as the counter electrode, and a saturated Hg / HgO electrode as the reference electrode. The electrolyte was 1 MkOH solution (prepared with ultrapure water). Before testing, high-purity oxygen was continuously bubbled into the electrolyte for at least 30 minutes. All tests were conducted at room temperature, and the RDE was kept rotating at 1600 rpm during the tests to eliminate mass transfer effects. All measured potentials were converted to potentials relative to the reversible hydrogen electrode (RHE) using the formula E(vs.RHE) = E(vs.Hg / HgO) + 0.0591 × pH + 0.098.

[0028] Performance Testing and Result Analysis: The working electrode was first subjected to 20 cyclic voltammetric scans at a scan rate of 100 mV / s within the 0.35 V to 1.0 V range to activate the catalyst surface and stabilize the current response. Then, linear sweep voltammetry was used to evaluate the OER activity. The scan potential range was 0.35 V to 1.0 V, and the scan rate was 50 mV / s. To accurately reflect the true overpotential of the catalyst, all test data were compensated for with 90% iR. Results ( Figure 5 a, b) show that the P,O-FeNiRuO of the present invention x The catalyst at a current density of 10 mA / cm -2 At that time, its overpotential (η) 10 The voltage is only 276 mV, far lower than that of the undoped FeNiRuO in Comparative Example 1. x The precursor (324 mV) and Comparative Example 2's commercial RuO2 (296 mV). At a higher 50 mA / cm²... -2The advantage is more pronounced at current densities, overpotential (η) 50 The value was 311 mV. The Tafel slope of each catalyst was calculated through linear fitting. This invention utilizes the P,O-FeNiRuO... x The catalyst exhibited the lowest Tafel slope, at 48.07 mVdec. -1 Significantly lower than FeNiRuO x And Com.RuO2. This indicates that the catalyst of the present invention has better reaction kinetics, and its rate-determining step may be closer to the ideal single-electron transfer step, which is beneficial for operation at high current densities. EIS tests were performed at a fixed potential of 1.55V (vs. RHE), and the fitting results show that P,O-FeNiRuO x R ct The value is only 2.0Ω, far lower than that of the comparative example 1FeNiRuO x (6.8Ω) and comparative example 2Com.RuO2 (4.2Ω). This directly proves that the catalyst has a faster interfacial charge transport rate after P and O doping, which is consistent with the conclusion that the electronic structure is optimized in XPS analysis.

[0029] Furthermore, to verify the catalytic performance and adaptability of the catalyst of this invention in a real complex environment (alkaline wastewater), the test system was the same as in Example 2, the only difference being that the electrolyte was replaced with a 1M KOH solution prepared from wastewater. The test curves are shown below. Figure 6 .

[0030] Example 3: Stability Test This example is used to evaluate the long-term operational stability of the catalyst prepared in Example 1.

[0031] Accelerated aging test (cycle stability): The load containing P,O-FeNiRuO x The working electrode of the catalyst was subjected to 11,000 cyclic voltammetry (CV) scans at a scan rate of 100 mV / s within a potential window of 1.2 V to 1.6 V (vs. RHE) in 1.0 mM MKOH to simulate rapid potential fluctuations and repeated adsorption / desorption of reaction intermediates. Immediately after the scan, the LSV curve was re-measured and compared with the initial LSV curve. The results showed that at 50 mA / cm²... -2 The overpotential at current density increased only from the initial 311mV to 317mV, an increment of 6mV, with an extremely low performance degradation rate (approximately 1.9%), demonstrating the catalyst's excellent structural mechanical stability and resistance to polarization.

[0032] Constant current durability test (chronovoltammetry): In 1.0 M KOH, P,O-FeNiRuO x Catalyst applied at 10 mAcm-2 The catalyst was subjected to a constant current density and tested continuously for 100 hours. The results fully demonstrate the excellent long-term electrochemical stability of the catalyst of this invention.

[0033] The detailed comparative analysis of the above embodiments and comparative examples fully demonstrates that the P,O-FeNiRuO provided by the present invention... x The catalyst and its preparation method achieve effective dual anion doping through a key solid-phase phosphating step, which significantly optimizes the electronic structure of the catalyst, increases the number of active sites, improves charge transport capability, and endows it with superior stability. Its comprehensive performance far exceeds that of the undoped precursor and commercial reference catalyst, showing great potential for practical applications.

[0034] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A P, O co-doped FeNiRuO x Nanocatalysts, their preparation methods and applications, characterized in that, The catalyst is a polygonal nanostructure composed of Fe, Ni, Ru, P and O elements, wherein the mass fraction of Fe ranges from 5.0 to 6.0%, the mass fraction of Ni ranges from 75 to 78%, the mass fraction of Ru ranges from 11 to 12%, the mass fraction of P ranges from 6.5 to 7.0%, and the O element exists in the form of surface adsorption state and PO bonded state. The catalyst comprises Ni2P phase, Fe7Ni3 alloy phase and Ru4Fe intermetallic compound phase, with characteristic lattice spacings of 0.19 nm, 0.22 nm and 0.237 nm, respectively. The surface electronic structure is reconstructed by P and O double anion co-doping to form a defect-rich active interface, which is used to optimize the oxygen evolution reaction kinetics.

2. The P, O co-doped FeNiRuO according to claim 1 x Nanocatalyst, characterized in that: The polygonal nanostructures have an average size ranging from 10 to 100 nm and a specific surface area ranging from 50 to 200 m². 2 / g, to expose more active sites and promote mass transfer of reactants.

3. The P, O co-doped FeNiRuO according to claim 1 x Nanocatalyst, characterized in that: The binding energy of the P2p orbital in the PO bonded state is 134.1 eV, and the binding energy of the MP bond is 129.5 eV. The electronic structure regulation induced by dianion doping was verified by XPS characterization.

4. A P, O co-doped FeNiRuO as described in any one of claims 1-3 x The method for preparing nanocatalysts is characterized by: Includes the following steps: (1) Nickel acetylacetone, iron acetylacetone, ruthenium chloride trihydrate, oleylamine, and 1-octadecene are mixed to obtain a mixed reaction solution, wherein the molar ratio of nickel acetylacetone, iron acetylacetone, and ruthenium chloride trihydrate is 0.2:0.3:(0.05-0.2), and the volume ratio of oleylamine to 1-octadecene is 2:(8-12); (2) The mixed reaction solution is heated to 200℃-300℃ at a heating rate of 5-10℃ / min, held at that temperature for 1-3 hours, cooled, centrifuged, washed, and dried to obtain FeNiRuO. x Precursor; (3) The precursor and sodium hypophosphite are mixed and ground at a mass ratio of 1:(3-5), and heated to 350-450°C at a heating rate of 2-10°C / min under an inert atmosphere and calcined for 1-3 hours to achieve P and O co-doping and obtain the catalyst.

5. A P, O co-doped FeNiRuO as described in claim 4 x The method for preparing nanocatalysts is characterized by: The washing in step (2) is performed by alternating between anhydrous ethanol and n-heptane, with a drying temperature of 40℃-60℃ and a drying time of 2-4 hours, in order to thoroughly remove organic residues and maintain the structural integrity of the precursor.

6. A P, O co-doped FeNiRuO as described in claim 4 x The method for preparing nanocatalysts is characterized by: The inert atmosphere mentioned in step (3) is argon or nitrogen. After calcination, it is naturally cooled to room temperature to suppress oxidation and ensure the uniformity of the phosphating reaction.

7. A P, O co-doped FeNiRuO as described in any one of claims 1-3 x The application of nanocatalysts in hydrogen production by water electrolysis is characterized by: The catalyst is used as an anode catalyst for the oxygen evolution reaction (OER) and is suitable for alkaline pure water systems or alkaline wastewater systems.

8. A P, O co-doped FeNiRuO according to claim 7 x Application of nanocatalysts in hydrogen production via water electrolysis, wherein the alkaline wastewater system contains industrial wastewater components, and the catalyst operates at 10 mA / cm². -2 The overpotential at current density is less than 300mV, and the performance degradation rate is less than 3% after 100 hours of stability testing.

Images