Lanthanum oxide doped molybdenum-based supported catalyst as well as preparation method and application thereof

Abstract

The invention provides a lanthanum oxide doped molybdenum-based supported catalyst as well as a preparation method and application thereof, and belongs to the technical field of electrocatalytic decomposition hydrogen desorption catalysts. The preparation method of the lanthanum oxide-doped molybdenum-based supported catalyst comprises the following steps: mixing ammonium molybdate or a hydrate thereof, lanthanum oxide and a modifier in water to form a mixed solution; a pretreated porous carrier is added into the mixed solution for a hydrothermal reaction, and a catalyst precursor is obtained; and roasting the catalyst precursor in an inert atmosphere, and cooling to obtain the lanthanum oxide doped molybdenum-based supported catalyst, wherein the modifier comprises at least one of ethanol, glucose and acetic acid. The doping of lanthanum oxide can adjust the electronic structure of MoO2, optimize the hydrogen adsorption free energy and improve the catalytic activity of the molybdenum-based supported catalyst, the introduced modifier inhibits MnO2 from being excessively oxidized into MoO3, the stability of the molybdenum-based supported catalyst is maintained, and the catalytic activity of the molybdenum-based supported catalyst is further enhanced.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic desorption hydrogen catalyst technology, and particularly to a lanthanum oxide-doped molybdenum-based supported catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen, with its high energy density (120 MJ / kg), environmental friendliness, and renewability, is becoming one of the future alternatives to fossil fuels. Currently, catalytic hydrogen evolution via water electrolysis is a widely used hydrogen production method. However, this reaction has a high overpotential at the cathode, leading to high costs for hydrogen production. Catalysts are typically added to reduce the overpotential at the cathode; commonly used catalysts are platinum and its compounds. However, platinum is expensive and its reserves are limited, restricting its further development and application.

[0003] Therefore, it is necessary to find catalysts that are abundant, inexpensive, and readily substitutable, while also maintaining high catalytic efficiency in hydrogen production. Summary of the Invention

[0004] In view of this, in order to at least partially solve the aforementioned technical problems, the present invention provides a lanthanum oxide-doped molybdenum-based supported catalyst, its preparation method, and its application.

[0005] According to one aspect of the present invention, a method for preparing a lanthanum oxide-doped molybdenum-based supported catalyst is provided, comprising: mixing ammonium molybdate or its hydrate, lanthanum oxide, and a modifier in water to form a mixture; adding a pretreated porous support to the mixture and performing a hydrothermal reaction to obtain a catalyst precursor; calcining the catalyst precursor under an inert atmosphere and cooling to obtain a lanthanum oxide-doped molybdenum-based supported catalyst; wherein the modifier includes at least one selected from ethanol, glucose, and acetic acid; the pretreated porous support is prepared by ultrasonically washing the porous support sequentially with an acidic solution, an ethanol solution, and water, followed by drying; the porous support includes any one selected from nickel foam and graphite.

[0006] In some embodiments, when the modifier is ethanol, the volume ratio of water to ethanol is 1:(0.5~1); when the modifier is glucose, the mass ratio of glucose to ammonium molybdate or its hydrate is (0.4~1):1; when the modifier is acetic acid, the volume ratio of water to acetic acid is 1:(0.5~1).

[0007] In some implementations, when the modifier is ethanol, the volume ratio of water to ethanol is 1:0.9.

[0008] In some implementations, the mass of lanthanum oxide is a, the mass of ammonium molybdate or its hydrate is b, and the ratio of a to b is 5 to 12%.

[0009] In some implementations, the hydrothermal reaction temperature is 100~210℃ and the reaction time is 12~24h.

[0010] In some implementations, the calcination temperature is 650-700°C, the calcination time is 150-180 min, and the inert atmosphere includes a nitrogen atmosphere.

[0011] According to another aspect of the present invention, a lanthanum oxide-doped molybdenum-based supported catalyst prepared by the preparation method described above is provided, comprising a porous support and La2O3-doped MoO2 nanoparticles grown in situ on the surface of the porous support.

[0012] In some implementations, the average particle size of the La2O3-doped MoO2 nanoparticles is 0.6–1.5 μm.

[0013] According to another aspect of the present invention, the application of the lanthanum oxide-doped molybdenum-based supported catalyst described above in alkaline water splitting for hydrogen production is provided.

[0014] According to the preparation method of the lanthanum oxide-doped molybdenum-based supported catalyst of the present invention, the introduction of lanthanum oxide (La₂O₃) can adjust the electronic structure of MoO₂ in the formed molybdenum-based supported catalyst, causing the d-band center to shift, optimizing the hydrogen adsorption free energy, and improving the catalytic activity of the lanthanum oxide-doped molybdenum-based supported catalyst. Furthermore, the addition of lanthanum oxide promotes the formation of more La₂O₃-doped MoO₂ composite particles, increasing the effective electrochemical surface area, thereby improving the catalytic activity. In the preparation process of the lanthanum oxide-doped molybdenum-based supported catalyst, the addition of the above-mentioned modifier can inhibit the over-oxidation of MoO₂ to MoO₃ during the reaction, further enhancing the catalytic performance of the lanthanum oxide-doped molybdenum-based supported catalyst. Simultaneously, the addition of the modifier can promote the uniform dispersion of ammonium molybdate or its hydrate, reduce the agglomeration of La₂O₃-doped MoO₂ composite particles, form more uniformly distributed active sites, and enhance catalytic activity. In addition, the addition of porous support provides a larger specific surface area, and its three-dimensional porous structure is conducive to the rapid diffusion of gas in subsequent applications of alkaline water electrolysis for hydrogen production, avoiding mass transfer limitations caused by the accumulation of bubbles on the electrodes. Attached Figure Description

[0015] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings.

[0016] Figure 1 This is a flowchart illustrating the preparation method of the lanthanum oxide-doped molybdenum-based supported catalyst according to an embodiment of the present invention.

[0017] Figure 2The images show scanning electron microscope (SEM) images of the catalysts prepared in Comparative Example 1 and Example 1, respectively.

[0018] Figure 3 Linear sweep voltammetry (LSV) curves of the catalysts in Examples 1-5 and Comparative Example 1 are shown.

[0019] Figure 4 Tafel curves of the catalysts in Examples 1-5 and Comparative Example 1;

[0020] Figure 5 The LSV curves of the catalysts in Examples 1, 6-7 and Comparative Examples 2-3 are shown.

[0021] Figure 6 Tafel curves of the catalysts in Examples 1, 6-7 and Comparative Examples 2-3;

[0022] Figure 7 The 48-hour chronoampere (CA) curve of the catalyst in Example 1 is shown.

[0023] Figure 8 The 48-hour chronopotential (CP) curve of the catalyst in Example 1 is shown. Detailed Implementation

[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0025] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0026] Currently, hydrogen production through water electrolysis is considered an important future development path for industrial hydrogen production due to its relatively simple process conditions, low equipment requirements, and high product purity. However, the slow kinetics of the hydrogen evolution reaction (HER) in water electrolysis lead to high energy consumption, and current catalytic materials struggle to achieve optimal performance, stability, and cost-effectiveness. Therefore, there is an urgent need to develop hydrogen evolution reaction (HER) catalysts that combine high activity, low cost, and stable durability.

[0027] Among transition metal oxides, MoO2 exhibits superior electronic conductivity, high chemical stability, and abundant edge active sites (including molybdenum and oxygen vacancies in intrinsic defect structures), demonstrating potential application value in electrocatalysis. However, this material is prone to nanoparticle aggregation during catalysis, leading to insufficient exposure of active sites and severely limiting the improvement of its electrochemical active surface area, thus restricting its catalytic efficiency in HER. Furthermore, the preparation of MoO2 requires relatively strict synthesis conditions, places high demands on equipment, and is complex to operate.

[0028] In realizing this invention, it was discovered that MoO2 is synthesized on a porous support substrate via a hydrothermal reaction. Simultaneously, the electronic structure of MoO2 is adjusted by doping with La2O3, optimizing the hydrogen adsorption free energy and improving catalytic activity. By introducing a modifier, excessive oxidation of MoO2 is suppressed, thereby controlling its valence state and morphology. Combined with the synergistic effect of lanthanum oxide and the modifier, the durability and stability of the molybdenum-based supported catalyst can be improved without damaging the basic framework of the porous support, while maintaining good catalytic performance.

[0029] Specifically, according to one embodiment of the present invention, a method for preparing a lanthanum oxide-doped molybdenum-based supported catalyst is provided. Figure 1 This is a flowchart illustrating a method for preparing a lanthanum oxide-doped molybdenum-based supported catalyst according to an embodiment of the present invention. Figure 1 As shown, the preparation method includes steps S101 to S103.

[0030] In step S101, ammonium molybdate or its hydrate, lanthanum oxide and a modifier are mixed in water to form a mixture.

[0031] In step S102, a pretreated porous support is added to the mixture for hydrothermal reaction to obtain a catalyst precursor.

[0032] In step S103, the catalyst precursor is calcined under an inert atmosphere and cooled to obtain a lanthanum oxide-doped molybdenum-based supported catalyst.

[0033] According to embodiments of the present invention, the introduction of lanthanum oxide, based on the similarity of atomic radii, helps to regulate the electronic structure of MoO2, optimize the hydrogen adsorption free energy, and promote the formation of a relatively large number of La2O3-doped MoO2 composite particles (hereinafter referred to as MoO2 composite particles). This increases the effective surface area for subsequent application as an electrode in water electrolysis for hydrogen production, thereby improving the overall catalytic efficiency. The in-situ growth of lanthanum oxide-doped molybdenum-based catalysts on the inner and outer surfaces of a porous support is achieved based on a hydrothermal reaction. No additional impurities (anionic impurities, such as chloride ions, nitrate ions, sulfate ions, etc.) are introduced during the hydrothermal reaction, reducing the adverse effects on the electrochemical performance of the lanthanum oxide-doped molybdenum-based supported catalyst.

[0034] According to embodiments of the present invention, the modifier includes at least one of ethanol, glucose, and acetic acid. It is understood that the addition of ethanol helps improve the solubility of ammonium molybdate or its hydrate, promoting uniform dispersion and reducing agglomeration. Furthermore, the decomposition of ethanol during the hydrothermal reaction can generate hydroxyl groups on its surface, thereby modifying the surface of the MoO2 composite particles, providing proton transfer sites, and promoting hydrogen adsorption in subsequent electrocatalysis. Simultaneously, the weak reducing properties of ethanol can inhibit the over-oxidation of MoO2 to MoO3 during the reaction, helping to maintain the stability of the lanthanum oxide-doped molybdenum-based supported catalyst. In the preparation process and / or application in electrocatalysis, the addition of ethanol can partially remove MoO2 from the surface of MoO2. 4+ Further restored to Mo 3+ This creates oxygen vacancies, enhancing the electron transport and adsorption capabilities of lanthanum oxide-doped molybdenum-based supported catalysts.

[0035] The aldehyde group (and other groups such as hydroxyl groups) on glucose molecules release reducing gases, such as hydrogen or carbon monoxide, during hydrothermal reactions and / or calcination, which can lead to the formation of undesirable Mo during the reaction. 6+ Restored to Mo 4+ (It exists as MoO2 after calcination), while simultaneously introducing oxygen vacancies. In addition, glucose can guide MoO2 to form porous or nanosheet structures during hydrothermal reaction and / or calcination, further increasing the number of exposed active sites.

[0036] The addition of acetic acid can improve the aggregation of MoO2 and modify the surface of lanthanum oxide-doped molybdenum-based supported catalysts, providing proton adsorption and transport sites, while also helping to maintain the MoO2 content. 4+ The stable state. This invention, through the interaction between lanthanum oxide and the aforementioned modifiers, enables the lanthanum oxide-doped molybdenum-based supported catalyst to possess high electrocatalytic activity, excellent durability, and long-term stability when used as a hydrogen evolution catalyst.

[0037] The porous support of this invention, such as a porous metal support, possesses abundant porous structure and excellent conductivity, providing support for a large specific surface area, thus promoting the in-situ growth of lanthanum oxide-doped molybdenum-based catalysts. The three-dimensional porous structure of the porous support facilitates rapid gas diffusion away from the electrode surface during electrocatalysis, avoiding mass transfer limitations caused by bubble accumulation. The resulting lanthanum oxide-doped molybdenum-based supported catalyst can be directly used as a working electrode at high current densities. According to embodiments of this invention, the preparation method is relatively simple, low-cost, and uses mild reaction conditions, and the prepared lanthanum oxide-doped molybdenum-based supported catalyst exhibits excellent durability and good stability. Furthermore, it avoids the use of precursor salts commonly used in hydrothermal reactions, avoiding the introduction of anionic impurities such as chloride and nitrate ions, saving steps, and avoiding the residual risk of aforementioned anionic impurities present in related technologies. Anionic impurities in related technologies are not only difficult to completely remove in subsequent processes but may also remain on the catalyst surface, further affecting the electrochemical performance of the catalyst.

[0038] According to an embodiment of the present invention, the pretreated porous carrier is prepared by ultrasonically washing the porous carrier sequentially with an acidic solution, an ethanol solution, and water, followed by drying. This arrangement helps to remove impurities from the surface of the porous carrier, activate its inner and outer surfaces, and improve the uniformity and stability of the load.

[0039] In some embodiments, the porous support includes either nickel foam or graphite. Nickel foam and graphite possess porous structures and excellent electrical conductivity, allowing them to be used directly as working electrodes for in-situ growth of lanthanum oxide-doped molybdenum-based catalysts without the need for binders. They not only provide a large specific surface area for the lanthanum oxide-doped molybdenum-based catalyst, but their three-dimensional porous structure also facilitates rapid gas diffusion away from the electrode surface, avoiding mass transfer limitations caused by bubble accumulation. Nickel foam is preferred.

[0040] In some implementations, drying may include air drying at room temperature or vacuum drying.

[0041] In some specific implementations, the pretreatment includes ultrasonically immersing and cleaning the nickel foam carrier for 15 minutes in a 2 mol / L hydrochloric acid solution, anhydrous ethanol, and deionized water, followed by vacuum drying.

[0042] In some implementations, ammonium molybdate hydrate may include ammonium molybdate tetrahydrate.

[0043] In some embodiments, when ethanol is used as the modifier, the volume ratio of water to ethanol is 1:(0.5~1). This setting allows the addition of ethanol to adjust the solvent polarity, optimizing the dissolution and depolymerization state of ammonium molybdate or its hydrate, encouraging dissociation into smaller molybdenum-oxygen units. These smaller units diffuse more easily into the micropores of the porous support, achieving high dispersion and effectively preventing the aggregation of molybdenum-oxygen units. This results in smaller, more uniformly distributed active sites after calcination. The addition of ethanol also helps adjust the surface tension of the water and ethanol mixture, promoting the penetration of the mixture into the pores of the porous support and further promoting the uniform loading of molybdenum-oxygen units within the porous support. After subsequent calcination, the molybdenum-oxygen units form MoO2. By adjusting the water-to-ethanol ratio to the above range, proton transfer sites can be provided while promoting uniform dispersion of MoO2; simultaneously, the weak reducing properties of ethanol further enhance the electron transport capacity and adsorption performance of the catalyst. If the ethanol ratio is too low, for example, below the lower limit mentioned above, the effect of reducing surface tension and depolymerization will not be obvious, which is not conducive to the dispersion of molybdenum oxide units. If the ethanol ratio is too high, for example, above the upper limit mentioned above, it may lead to a decrease in the solubility of ammonium molybdate or its hydrate, resulting in uneven mixing. In addition, a low water ratio will also result in poor dispersion of lanthanum oxide.

[0044] Optionally, the volume ratio of water to ethanol can be, for example, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1, or a range consisting of any two of the above ratios.

[0045] In some preferred embodiments, the volume ratio of water to ethanol is 1:0.9. This setting effectively prevents the aggregation of ammonium molybdate or its hydrate, further optimizing the efficiency and uniformity of hydrogen adsorption during the electrocatalytic process.

[0046] In some embodiments, when glucose is used as the modifier, the mass ratio of glucose to ammonium molybdate or its hydrate is (0.4~1):1. This configuration, by introducing an appropriate amount of glucose, helps to adequately guide the formation of porous or nanosheet structures from MoO2, increasing the number of exposed active sites. If the glucose content is too low, for example below the lower limit mentioned above, it is difficult to provide sufficient structure guidance; if the glucose ratio is too high, for example above the upper limit mentioned above, it may clog the pores of the porous support, leading to coverage of active sites and reducing the catalytic activity of the lanthanum oxide-doped molybdenum-based supported catalyst.

[0047] Optionally, the mass ratio of glucose to ammonium molybdate or its hydrate may be, for example, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1, or a range consisting of any two of the above ratios.

[0048] In some embodiments, when the modifier is acetic acid, the volume ratio of water to acetic acid is 1:(0.5~1). Acetic acid is a weak acid, which causes the molybdate ion to tend to protonate, promoting the molybdate... 4+ The stable formation of [Mo] is facilitated by the electrostatic adsorption of negatively charged molybdate ions onto the porous support surface under weakly acidic conditions, thus mitigating aggregation. Furthermore, the electronic effect of acetic acid contributes to the stabilization of Mo. 4+ The formation of [something] reduces excessive oxidation into Mo. 6+ If the acetic acid content is too low, for example, below the lower limit mentioned above, the acidity will be too weak to effectively inhibit the polymerization of molybdate ions, and the effect on controlling the valence state of molybdenum will be limited. If the acetic acid ratio is too high, for example, above the upper limit mentioned above, it may corrode the porous support, destroy its pore structure, and lead to a decrease in mechanical strength.

[0049] Optionally, the volume ratio of water to acetic acid may be, for example, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1, or a range consisting of any two of the above ratios.

[0050] In some implementations, the mass of lanthanum oxide is 'a', and the mass of ammonium molybdate or its hydrate is 'b', with an a / b ratio of 5-12%. Lanthanum oxide doping effectively modulates the electron configuration of MoO2, causing a shift in its d-band center, resulting in a favorable hydrogen adsorption free energy. This enhances the adsorption and activation capacity for water molecules in subsequent water electrolysis for hydrogen production, lowers the reaction energy barrier for steps such as water molecule dissociation and hydrogen atom recombination, and improves the intrinsic catalytic activity of the lanthanum oxide-doped molybdenum-based supported catalyst. Morphologically, lanthanum oxide doping increases the surface roughness of the formed lanthanum oxide-doped molybdenum-based supported catalyst. Together with the modifier, it induces the refinement and dispersion of MoO2 composite particles, constructing a rough surface rich in nanoparticles, providing more active sites, and optimizing the interfacial wettability of the electrode, thus providing favorable conditions for efficient mass transport. If the doping amount of lanthanum oxide is too low, the above-mentioned improvement is not obvious; if the doping amount of lanthanum oxide is too high, the excess lanthanum oxide exists in the form of agglomeration, which will physically cover the active sites activated by the electronic effect, and may also block the three-dimensional porous structure of the lanthanum oxide-doped molybdenum-based supported catalyst, hindering the mass transfer process and weakening the catalytic performance.

[0051] Alternatively, a / b can be, for example, 5%, 7.5%, 10% or 12%, or a range consisting of any two of the above ratios.

[0052] In some embodiments, the hydrothermal reaction temperature is 100–210°C, and the reaction time is 12–24 h. Setting the temperature in this way effectively promotes the reaction, allowing the mixture to penetrate into the pores of the porous support, laying the foundation for uniform loading, and significantly accelerating the hydrolysis and condensation reactions of the metal precursor (such as ammonium molybdate or its hydrate, lanthanum oxide), as well as the chemical bonding between the metal precursor and the functional groups on the surface of the porous support. Setting the reaction time in this way helps to achieve uniform and sufficient loading of the active component of the metal precursor (such as ammonium molybdate or its hydrate, lanthanum oxide) on the porous support.

[0053] Optionally, the temperature of the hydrothermal reaction can be, for example, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, or 210°C, or a range consisting of any two of the above values.

[0054] Optionally, the reaction time of the hydrothermal reaction can be, for example, 12h, 14h, 16h, 18h, 20h, 22h or 24h, or a range consisting of any two of the above values.

[0055] In some implementations, the calcination temperature is 650–700 °C, and the calcination time is 150–180 min. This setting helps ensure the complete decomposition of ammonium molybdate or its hydrate, modifiers, and catalyst precursors formed by the hydrothermal reaction, promoting the formation and growth of MoO2. This allows the lanthanum oxide-doped molybdenum-based catalyst to be firmly anchored on the outer and inner surfaces of the porous support, improving the thermal stability and lifespan of the lanthanum oxide-doped molybdenum-based supported catalyst. Furthermore, the calcination process removes impurities from the reaction process, preventing them from occupying active sites.

[0056] Optionally, the calcination temperature may be, for example, 650°C, 660°C, 670°C, 680°C, 690°C, or 700°C, or a range consisting of any two of the above values.

[0057] Optionally, the roasting time may be, for example, 150 min, 160 min, 170 min or 180 min, or a range consisting of any two of the above values.

[0058] In some embodiments, the inert atmosphere includes a nitrogen atmosphere. A nitrogen atmosphere prevents MoO2 from being over-oxidized to MoO3, which has lower catalytic activity, thereby improving the catalytic activity and stability of the lanthanum oxide-doped molybdenum-based supported catalyst.

[0059] According to another aspect of the present invention, a lanthanum oxide-doped molybdenum-based supported catalyst prepared by the preparation method described above is provided, comprising a porous support and La2O3-doped MoO2 nanoparticles grown in situ on the surface of the porous support.

[0060] According to embodiments of the present invention, in the lanthanum oxide-doped molybdenum-based supported catalyst prepared by the present invention, lanthanum oxide doping regulates the electronic structure of the molybdenum-based supported catalyst, and the modifier regulates the valence state and morphology of MoO2. The synergistic effect of lanthanum oxide and the modifier improves the catalytic activity, durability, and stability of the lanthanum oxide-doped molybdenum-based supported catalyst without destroying the basic framework. La2O3-doped MoO2 nanoparticles have a large specific surface area, thereby increasing adsorption sites and further improving catalytic reaction efficiency. The lanthanum oxide-doped molybdenum-based supported catalyst of the present invention exhibits high catalytic activity, low cost, and long service life.

[0061] In some embodiments, the average particle size of the La2O3-doped MoO2 nanoparticles is 0.6–1.5 μm. This configuration can further improve the surface roughness of the lanthanum oxide-doped molybdenum-based supported catalyst, increase the specific surface area, and expand the number of active sites.

[0062] Optionally, the average particle size of the La2O3-doped MoO2 nanoparticles may be, for example, 0.6 μm, 0.9 μm, 1.1 μm, 1.3 μm or 1.5 μm, or a range consisting of any two of the above values.

[0063] According to another aspect of the present invention, the application of the lanthanum oxide-doped molybdenum-based supported catalyst described above in alkaline water splitting for hydrogen production is provided.

[0064] According to embodiments of the present invention, similarly to the foregoing, the lanthanum oxide-doped molybdenum-based supported catalyst of the present invention has high activity, durability and stability, can improve the reaction rate of hydrogen evolution reaction, and has good hydrogen production catalytic efficiency when applied to alkaline water splitting for hydrogen production, while having low cost.

[0065] The technical solution of the present invention will be further illustrated below through specific embodiments. It should be noted that the specific embodiments described below are merely illustrative examples, and the scope of protection of the present invention is not limited thereto.

[0066] Example 1

[0067] The preparation process of lanthanum oxide-doped molybdenum-based supported catalyst is shown below.

[0068] The nickel foam was cut into small pieces of 1cm×2cm. Then, the nickel foam was pretreated by washing it with 2mol / L hydrochloric acid solution, anhydrous ethanol and deionized water under ultrasonic conditions for 15min each. After washing, the nickel foam was dried at room temperature to obtain the pretreated porous nickel carrier.

[0069] Weigh 0.1250g of ammonium molybdate tetrahydrate and 7.5% of the mass of ammonium molybdate tetrahydrate lanthanum oxide into a 100mL reaction vessel liner. Add 10mL of deionized water and 10mL of anhydrous ethanol, and stir thoroughly until completely dissolved to obtain a premixed solution.

[0070] Next, a pretreated porous nickel support was added to the premixed solution for a hydrothermal reaction at a temperature of 210°C for 20 hours. After cooling to room temperature, the solution was washed with deionized water and ethanol and then vacuum dried to obtain the precursor.

[0071] The precursor was placed in a furnace and calcined under a N2 atmosphere at 650°C for 180 min, and then cooled to room temperature to obtain a lanthanum oxide-doped molybdenum-based supported catalyst, which was calculated to be 7.5% La2O3-MoO2 / Ni.

[0072] Example 2

[0073] The only difference from Example 1 is that the amount of lanthanum oxide used is 2.5% of the mass of ammonium molybdate tetrahydrate. All other experimental conditions are the same as in Example 1. The resulting lanthanum oxide-doped molybdenum-based supported catalyst is calculated to be 2.5% La2O3-MoO2 / Ni.

[0074] Example 3

[0075] The only difference from Example 1 is that the amount of lanthanum oxide used is 5% of the mass of ammonium molybdate tetrahydrate. All other experimental conditions are the same as in Example 1. The resulting lanthanum oxide-doped molybdenum-based supported catalyst is calculated as 5%La2O3-MoO2 / Ni.

[0076] Example 4

[0077] The only difference from Example 1 is that the amount of lanthanum oxide used is 10% of the mass of ammonium molybdate tetrahydrate. All other experimental conditions are the same as in Example 1. The resulting lanthanum oxide-doped molybdenum-based supported catalyst is calculated to be 10%La2O3-MoO2 / Ni.

[0078] Example 5

[0079] The only difference from Example 1 is that the amount of lanthanum oxide used is 12% of the mass of ammonium molybdate tetrahydrate. All other experimental conditions are the same as in Example 1. The resulting lanthanum oxide-doped molybdenum-based supported catalyst is calculated to be 12%La2O3-MoO2 / Ni.

[0080] Comparative Example 1

[0081] The only difference from Example 1 is that lanthanum oxide was not added, while all other experimental conditions were the same as in Example 1. The resulting molybdenum-based supported catalyst was denoted as MoO2 / Ni.

[0082] Figure 2The images show scanning electron microscope (SEM) images of the catalysts prepared in Comparative Example 1 and Example 1, respectively; where (a) is the SEM image of Comparative Example 1; (b) is the SEM image of Example 1; and (c) is a magnified view of (b). Figure 2 In (a) to (c), it can be observed that the microstructure of the MoO2 / Ni catalyst in Comparative Example 1 and the 7.5% La2O3-MoO2 / Ni catalyst in Example 1 differs significantly in morphology. The surface of MoO2 / Ni in Comparative Example 1 is relatively smooth, and the pore structure is relatively regular, but there are no obvious nanoscale particles or roughness on the pore walls. This indicates that its specific surface area is limited and the number of exposed active sites is small. Although some large pores can be seen, these pores facilitate electrolyte permeation and gas escape, but the smoothness of the pore walls limits the number of active sites. In contrast, the surface of the 7.5% La2O3-MoO2 / Ni catalyst in Example 1 is significantly rougher, with a large number of nanoparticles uniformly dispersed on the pore walls. These nanoparticles on the pore walls increase the surface roughness and irregularity, thereby greatly increasing the specific surface area of ​​the catalyst. The presence of these nanoparticles not only increases the physical contact area but also introduces new chemical active sites, such as La-O bonds and Mo-O-La interfaces. These sites play an important role in the adsorption and activation of water molecules.

[0083] Test case

[0084] Electrochemical performance tests were performed on Examples 1-5 and Comparative Example 1 in 1.0 M KOH electrolyte, with a calomel electrode as the reference electrode and a scan rate of 5 mV·s. -1 The current curves as a function of voltage were recorded, and the results are shown in Table 1 below.

[0085] Table 1 Performance data of Examples 1-5 and Comparative Example 1

[0086]

[0087] Figure 3 The catalysts used in Examples 1-5 and Comparative Example 1 were tested at a current density of 10 mA / cm². 2 Linear sweep voltammetry (LSV) curve at time; Figure 4 The Tafel curves for the catalysts of Examples 1-5 and Comparative Example 1 are shown below. It can be understood that... Figure 4 The horizontal axis in the table represents the logarithm of the absolute value. (Referring to Table 1 and...) Figures 3-4As can be seen, compared to Comparative Example 1, the overpotential did not change significantly after doping with La2O3 in Example 2, and the Tafel slope was relatively poor. With gradually increasing the doping amount of La2O3, the overpotential decreased significantly, indicating that further increases in La2O3 significantly improved the catalytic activity. Among them, the 7.5% La2O3-MoO2 / Ni sample (Example 1) had a relatively lower overpotential (-0.115V) and Tafel slope, meaning that under these conditions, the catalyst required a relatively smaller overpotential and achieved higher efficiency; and as... Figure 2 As shown, although unmodified MoO2 / Ni has macroscopic pores, its smooth surface severely limits its adsorption and activation ability for reactants (such as H2O molecules), which is directly reflected in its relatively high overpotential (-0.214V), indicating its low intrinsic catalytic activity. With increasing La2O3 doping concentration beyond 2.5%, the hydrogen evolution overpotential of the catalyst first drops sharply and then slowly recovers, reaching a relatively optimal value of -0.115V at a doping concentration of 7.5%, a decrease of approximately 100mV. This significant performance improvement is not due to a single factor, but rather stems from the profound synergistic effect between La2O3 and MoO2 in terms of electronic microstructure and macroscopic physical morphology.

[0088] From an in-depth exploration of the electronic structure, the introduction of La2O3 plays a crucial role. As a highly efficient electronic modulator, it effectively modulates the electronic configuration of MoO2, causing a shift in its d-band center. This fine-tuning of the electronic structure directly optimizes the adsorption behavior of hydrogen intermediates on the catalyst surface, bringing the hydrogen adsorption free energy close to the ideal thermally neutral state. This significantly reduces the reaction energy barrier for steps such as water molecule dissociation and hydrogen atom recombination, fundamentally enhancing the intrinsic activity of the catalytic site. At the morphological construction level, La2O3 also exhibits excellent structure-promoting functions. Together with the modifier ethanol, it effectively induces the refinement and dispersion of MoO2 composite particles during synthesis, successfully constructing a rough surface with abundant nanostructures. This morphological evolution directly leads to a significant increase in the electrochemically active surface area, not only providing more usable active sites for the reaction but also optimizing the interfacial wettability of the electrode, creating favorable conditions for efficient mass transfer. When the doping content of La2O3 exceeds 7.5%, the excess La2O3 (e.g., more than 12% doping content) begins to exist in the form of agglomerates. These agglomerates not only physically cover the highly active sites activated by electronic effects, but may also block the three-dimensional porous structure of the catalyst, hindering the mass transfer process, and ultimately leading to the breakdown of the synergistic balance and the decline of catalytic performance.

[0089] In summary, the Tafel slope data and overpotential analysis are highly consistent, indicating that the introduction of La2O3 not only modulates the electronic structure of MoO2, but also provides more available active sites for the hydrogen evolution reaction, thereby significantly enhancing the HER activity of the catalyst.

[0090] Example 6:

[0091] The preparation process of Example 6 is largely the same as that of Example 1, except that the modifier added is different. It is glucose, and the mass of glucose added is 0.125g, so as to obtain a lanthanum oxide-doped molybdenum-based supported catalyst, which is calculated as 7.5%La2O3-MoO2 / Ni (glucose).

[0092] Example 7:

[0093] The preparation process of Example 7 is largely the same as that of Example 1, except that the modifier added is different. It is acetic acid, and the volume of acetic acid added is 10 mL, resulting in a lanthanum oxide-doped molybdenum-based supported catalyst, which is calculated to be 7.5% La2O3-MoO2 / Ni (acetic acid).

[0094] Comparative Example 2:

[0095] The preparation process of Comparative Example 2 is largely the same as that of Example 1, except that no modifier is added, resulting in a lanthanum oxide-doped molybdenum-based supported catalyst, calculated as 7.5% La2O3-MoO2 / Ni (without modifier).

[0096] Comparative Example 3:

[0097] The preparation process is largely the same as in Example 1, except that cerium oxide is added instead of lanthanum oxide, resulting in 7.5% CeO2-MoO2 / Ni.

[0098] Test case

[0099] Electrochemical performance tests were conducted on Examples 6-7 and Comparative Examples 2-3 in 1.0 M KOH electrolyte, with a calomel electrode as the reference electrode and a scan rate of 5 mV·s. -1 The current curves as a function of voltage were recorded, and the results are shown in Table 2 below.

[0100] Table 2. Catalysts from Examples 1, 6-7 and Comparative Examples 2-3 at a current density of 10 mA / cm² 2 Hydrogen evolution overpotential and Tafel slope at time

[0101]

[0102] Figure 5 The catalysts used in Examples 1, 6-7, and Comparative Examples 2-3 were tested at a current density of 10 mA / cm². 2 LSV curve at time; Figure 6 The Tafel curves for the catalysts of Examples 1, 6-7, and Comparative Examples 2-3 are shown below. It can be understood that... Figure 4 Similarly, Figure 6The horizontal axis in the table represents the logarithm of the absolute value. (Referring to Table 2 and...) Figures 5-6 It can be seen that when glucose or acetic acid is used as a modifier, the catalyst performance is better than that of Comparative Example 2 without modifier, which fully demonstrates the key role of modifier in improving catalytic performance. Specifically, the superiority of glucose lies in the fact that the aldehyde group in its molecule can release a strong reducing gas during heat treatment, which not only ensures the Mo 6+ The precursor was efficiently reduced to active Mo. 4+ Simultaneously, abundant oxygen vacancies are created in the MoO2 lattice, significantly enhancing the intrinsic conductivity of the catalyst and its adsorption capacity for reaction intermediates. Furthermore, glucose acts as a soft template during decomposition, guiding the formation of nanostructures with larger specific surface areas and more exposed active sites. Acetic acid offers advantages in two aspects: firstly, its acidity improves the dispersibility of the precursor solution, effectively inhibiting the aggregation of MoO2 nanoparticles during growth, resulting in smaller size and more uniform distribution; secondly, the oxygen-containing functional groups generated by the high-temperature decomposition of acetic acid can modify the catalyst surface, providing additional proton adsorption and transport sites, while its weak reducing properties also help maintain the MoO2 nanoparticles' properties. 4+ To maintain its stable state and prevent its inactivation.

[0103] Compared to ethanol, the aforementioned modifiers have the following problems. For example, when glucose is used as a modifier, its carbonization products themselves act as a physical barrier, rapidly consuming and covering the active sites. In the aforementioned acidic hydrothermal medium with the pH value of Mo... 4+ The stability of [MoO2] is compromised, and the MoO2 precursor tends to form soluble [MoO2]. 2+ The presence of cations, rather than the target product MoO2, may cause the entire synthesis system to deviate from the intended path, resulting in a low-activity mixture with uncertain composition and blurred interfaces, encapsulated by amorphous carbon. Similarly, the carboxyl groups (-COOH) on acetic acid will have strong coordination interactions with the metal precursor. This competitive coordination severely interferes with the in-situ, ordered growth and composite process of MoO2 and La2O3 on nickel foam, preventing the formation of "La2O3-MoO2 composite particles" with highly active interfaces and instead generating a low-activity aggregate with unknown morphology. At the same time, the acidic acetic acid environment is also not conducive to the exposure of specific crystal faces.

[0104] Without the addition of a modifier, even with the same La2O3 doping amount (7.5%), the resulting catalyst exhibits a higher overpotential (-0.339V) and Tafel slope (353.2mV / dec). These data demonstrate that without the induction of oxygen vacancies and structural regulation by a modifier, La2O3 is difficult to effectively disperse and form an active interface with MoO2. The catalyst surface not only has a sparse number of active sites but also low intrinsic activity, making water molecule dissociation more difficult and the kinetic process more sluggish. Ultimately, La2O3 tends to form isolated clusters or surface coatings, failing to effectively regulate the electronic structure of Ni / Mo.

[0105] Ethanol is the preferred modifier in this invention. As a monohydroxy modifier, ethanol exhibits mild and controllable chemical behavior. It does not undergo a violent self-carbonization reaction and does not significantly disturb the solution pH, thus providing a stable reaction field for the in-situ, simultaneous crystallization and composite formation of MoO2 and La2O3. Furthermore, the reducing properties of ethanol and its weak coordination with the metal center can selectively induce oxygen vacancies in the MoO2 lattice. These defect sites become active sites for the preferential anchoring and growth of MoO2 composite nanoparticles, ultimately synergistically constructing an ideal composite structure rich in oxygen vacancies and featuring a highly active Mo-O-La interface.

[0106] Furthermore, under the same experimental conditions, not all rare earth element doping significantly improves overpotential, such as doping with CeO2. This is because Ce... 4+ The ionic radius (~0.87 Å) and Mo 4+ The large difference (~0.65 Å) leads to stress or phase separation in the MoO2 lattice, which in turn promotes particle aggregation. Meanwhile, La... 3+ Ions can partially dope into the rutile lattice of MoO2, or exist as La-O-Mo at grain boundaries, which helps stabilize the crystal phase of MoO and prevents it from undergoing phase transition or dissolution during hydrogen evolution reaction (especially under long-term alkaline conditions); and La 3+ As Lewis acid sites, they can adsorb water molecules and promote their dissociation (H-OH bond breaking). Although CeO2 also has a certain ability to adsorb and activate water molecules, its redox properties may lead to the formation of surface species (such as Ce...). 3+ CeO2 has poor stability (-OH), so under the strong reducing environment of hydrogen evolution, the surface of CeO2 may be over-reduced, lose its catalytic function, or even become an inert layer.

[0107] Figure 7 The 48-hour chronoampere (CA) curve of the catalyst in Example 1 is shown. Figure 8 The image shows the 48-hour chronopotential (CP) curve of the catalyst in Example 1. Catalyst stability testing: CA and CP tests were performed on the sample from Example 1; see [link to relevant documentation]. Figure 7The CA test curve was obtained with an applied potential of -1.25V (vs. RHE). The stability of the catalyst in Example 1 was studied in 1.0M KOH electrolyte. Initially, the current density decreased rapidly, indicating a rapid reaction or material consumption at the electrode surface after the applied potential, leading to a rapid decrease in current density. Over time, the current density gradually stabilized, entering a relatively gentle plateau period. During this plateau period, the current density fluctuated little, indicating a dynamic equilibrium state was reached and the reaction rate became relatively stable. Furthermore, the catalyst maintained a high current density for 48 hours, demonstrating that the 7.5% doped catalyst exhibits good electrochemical stability and durability under alkaline conditions, making it suitable as a high-efficiency HER catalyst for subsequent applications. See also... Figure 8 The CP test diagram shows an applied current density of 0.1 A / cm². 2 The stability of the sample from Example 1 was studied in 1.0 M KOH electrolyte. The potential of the catalyst initially increased significantly, then the fluctuations gradually decreased, and finally stabilized. The voltage at the end was 2.0539 V, which was 0.31% lower than the highest voltage of 2.0604 V at 1200 seconds. Throughout the experiment, the potential remained within a relatively stable range, indicating that the catalyst can maintain a relatively stable state during the reaction over a long period of time. This further proves that the doped sample exhibits good electrochemical performance and durability during long-term operation.

[0108] Mechanism analysis: Due to the good stability of La2O3 in alkaline environments, and the formation of a stable solid solution structure by doping MoO2 with La2O3, the dissolution of MoO2 is effectively suppressed, allowing the catalyst to maintain good structure and catalytic performance even during long-term operation. The synergistic effect of La2O3 and MoO2 significantly improves the electrocatalytic activity and durability of the lanthanum oxide-doped molybdenum-based supported catalyst, making it a promising and highly efficient HER catalyst.

[0109] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. 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 method for preparing a lanthana-doped molybdenum-based supported catalyst, characterized in that, The preparation method comprises: ammonium molybdate or a hydrate thereof, lanthanum oxide and a modifier are mixed in water to form a mixed solution; a pretreated porous carrier is added to the mixed solution to perform a hydrothermal reaction to obtain a catalyst precursor; the catalyst precursor is subjected to a calcination treatment under an inert atmosphere, and the lanthanum oxide doped molybdenum-based supported catalyst is obtained after cooling; the modifier comprises at least one of ethanol, glucose and acetic acid; the pretreated porous carrier is prepared by the following method: the porous carrier is sequentially subjected to ultrasonic washing with an acidic solution, an ethanol solution and water, and then dried; the porous carrier comprises any one of foamed nickel and graphite.

2. The production method according to claim 1, characterized by, when the modifier is ethanol, the volume ratio of water to ethanol is 1:(0.5-1); when the modifier is glucose, the mass ratio of glucose to ammonium molybdate or the hydrate thereof is (0.4-1):1; when the modifier is acetic acid, the volume ratio of water to acetic acid is 1:(0.5-1).

3. The preparation method according to claim 2, characterized in that, when the modifier is ethanol, the volume ratio of water to ethanol is 1:0.

9.

4. The method of claim 1, wherein, the mass of lanthanum oxide is a, the mass of ammonium molybdate or the hydrate thereof is b, and a / b is 5-12%.

5. The preparation method according to claim 1, characterized in that, the temperature of the hydrothermal reaction is 100-210°C, and the reaction time is 12-24h.

6. The method of claim 1, wherein, the temperature of the calcination treatment is 650-700°C, the calcination time is 150-180min, and the inert atmosphere comprises a nitrogen atmosphere. 7.A lanthanum oxide doped molybdenum-based supported catalyst prepared by the preparation method in any one of claims 1-6, comprising a porous carrier and La2O3 doped MoO2 nanoparticles in situ grown on the surface of the porous carrier.

8. The lanthana-doped molybdenum-based supported catalyst according to claim 7, characterized in that, the average particle size of the La2O3 doped MoO2 nanoparticles is 0.6-1.5μm. 9.Use of the lanthanum oxide doped molybdenum-based supported catalyst in claim 7 or 8 in alkaline water decomposition for hydrogen production.

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