Yttrium-doped phosphotungstic acid catalyst as well as preparation method and application thereof

Abstract

The invention discloses a yttrium-doped phosphotungstic acid catalyst as well as a preparation method and application thereof, and belongs to the technical field of electro-catalysis. The preparation method comprises the following steps: firstly, preparing yttrium-doped phosphotungstic acid Y-PTA by taking yttrium trichloride and phosphotungstic acid PTA as raw materials through an impregnation method, then preparing catalyst slurry by taking Y-PTA, ethanol, ultrapure water and a Nafion solution as raw materials, uniformly coating a gas diffusion layer carbon paper substrate with the catalyst slurry, spraying siloxane on the surface of the gas diffusion layer carbon paper substrate through an ultrasonic spraying technology, and drying the gas diffusion layer carbon paper substrate. And heating and drying to obtain the yttrium-doped phosphotungstic acid catalyst. The yttrium-doped phosphotungstic acid catalyst disclosed by the invention shows excellent electrocatalytic activity and selectivity, the electronic structure of the catalyst is optimized by doping yttrium metal, and an efficient hydrophobic layer is constructed on the surface of the catalyst, so that a hydrogen evolution competitive reaction and a catalyst dissolution phenomenon are greatly inhibited, and efficient electrocatalytic nitrogen reduction synthesis of ammonia is realized; the ammonia synthesis yield is up to 40.61 [mu] g.mg <-1 >. H <-1 >.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalysis, and in particular relates to an yttrium-doped phosphotungstic acid catalyst and a preparation method and application thereof. Background Art

[0002] Ammonia is one of the world's most produced chemical products and plays a vital role in the global economy. Currently, the traditional Haber-Bosch process is the primary method for industrial ammonia synthesis. This involves converting high-purity nitrogen and hydrogen into ammonia using an iron-based catalyst under high-temperature, high-pressure conditions. Due to the strong N≡N bond energy (945 kJ mol⁻¹) in nitrogen, this process requires high temperatures (300-500°C) and high pressures (150-300 atm) to activate the nitrogen. The resulting energy consumption and CO₂ emissions account for 1-3% and 1.6-3% of the global total, respectively. The Haber-Bosch process for ammonia synthesis is energy-intensive and highly polluting. Therefore, finding a green, environmentally friendly, and energy-efficient method for synthesizing ammonia is crucial for the sustainable development of the national economy.

[0003] Against this backdrop, the electrocatalytic nitrogen reduction reaction (NRR) has become a research hotspot due to its ability to directly convert nitrogen into ammonia at room temperature and pressure. Compared to traditional processes, NRR technology offers three breakthrough advantages: mild reaction conditions, the use of aqueous electrolytes (H+) as a clean hydrogen source, and near-zero carbon emissions during the reaction, providing a new path for the sustainable development of the synthetic ammonia industry. However, as an inert gas, N2 has a high nitrogen-nitrogen triple bond energy (941.69 kJ / mol). Therefore, in the electrochemical synthesis of ammonia, the adsorption and activation of N2 on the catalyst surface are key factors affecting the efficiency of the entire catalytic reaction.

[0004] At the same time, in aqueous electrolyte solutions, the overpotential of the hydrogen evolution reaction (HER) is very close to that of the nitrogen reduction reaction, so the electrochemical synthesis of ammonia is often accompanied by severe competition with the HER, which reduces the efficiency of electrocatalytic nitrogen reduction. In addition to studying how to increase ammonia yield, improving the selectivity of catalysts for nitrogen reduction is another key research issue in this field. Therefore, the electrocatalytic nitrogen reduction reaction has limitations such as low ammonia yield, low Faradaic efficiency, and difficulty in activation, making the commercialization of electrocatalytic nitrogen synthesis of ammonia difficult.

[0005] In recent years, researchers have attempted to find a reliable and sustainable electrocatalytic ammonia synthesis catalyst in catalyst research and development, and new catalysts such as transition metal-based, alloy, and carbon-based composite materials have continued to emerge. For example, the Chinese patent with publication number CN113802141A, filed on October 15, 2021, discloses a Pd / PdO heterojunction catalyst, preparation method, and application thereof. The Pd / PdO heterojunction catalyst increases the affinity of the Pd site for N2, making it more conducive to the formation of Pd-N bonds. The "synergistic effect" of the heterojunction allows N2 to be reduced by a distal association mechanism at low overpotential. The Chinese patent with publication number CN114855215A, filed on May 30, 2022, discloses a catalyst for efficient electrocatalytic ammonia synthesis and its preparation method. The resulting catalyst has a triple heterojunction interface with high conductivity and high interconnectivity, effectively improving NRR performance while suppressing HER activity.

[0006] Previous studies have shown that the unique structure and properties of Keggin-structured phosphotungstic acid (PTA) offer significant advantages in promoting N2 activation and inhibiting HER. Furthermore, its polyanion-rich pore structure facilitates N2 mass transfer, making it a promising catalyst for efficient eNRR. However, PTA's physical properties make it susceptible to dissolution during the reaction, reducing the catalyst's lifespan and hindering its practical application in ammonia synthesis.

[0007] Therefore, there is an urgent need to design a novel phosphotungstic acid (PTA) catalyst that can leverage the unique advantages of PTA materials in nitrogen activation and mass transfer while addressing the inadequate structural stability and the conflict between nitrogen mass transfer efficiency and the HER competitive reaction. This design not only has the potential to transform the catalytic potential of PTA into practical applications, but also provides a new paradigm for the development of non-precious metal NRR catalysts with high activity, high selectivity, and long life, and is a milestone in promoting green ammonia synthesis technology from the laboratory to industrialization. Summary of the Invention

[0008] To address the problems existing in the prior art, the present invention provides an yttrium-doped phosphotungstic acid catalyst, a preparation method, and an application thereof. By optimizing the electronic structure of the catalyst through yttrium metal doping and constructing an efficient hydrophobic layer on the catalyst surface, the "hydrogen evolution" competitive reaction and catalyst dissolution are greatly suppressed, thereby achieving efficient electrocatalytic nitrogen reduction to synthesize ammonia.

[0009] The technical solutions of the present invention are as follows:

[0010] One of the objectives of the present invention is to provide a method for preparing a yttrium-doped phosphotungstic acid catalyst. First, yttrium trichloride and phosphotungstic acid (PTA) are used as raw materials to prepare yttrium-doped phosphotungstic acid (Y-PTA) by an impregnation method. Then, a catalyst slurry is prepared using Y-PTA, ethanol, ultrapure water, and Nafion solution as raw materials. The slurry is evenly coated on a gas diffusion layer carbon paper substrate. Siloxane is sprayed on the surface using ultrasonic spraying technology, and the yttrium-doped phosphotungstic acid catalyst is obtained after heating and drying.

[0011] Further, the following steps are included:

[0012] S1. Pre-treat the gas diffusion layer carbon paper substrate by immersing it in 3M H2SO4, then rinse it with ultrapure water and dry it, then cut it into small pieces for later use;

[0013] S2. PTA was evenly dispersed in 10 mL of deionized water to prepare a PTA solution, and then yttrium chloride YCl3 solution was added dropwise. After sufficient stirring, the mixture was freeze-dried to obtain yttrium-doped phosphotungstic acid Y-PTA.

[0014] S3, preparing a catalyst slurry using the Y-PTA prepared in S2, ethanol, ultrapure water and Nafion solution as raw materials;

[0015] S4, take the catalyst slurry described in S3 and evenly apply it on the small piece of gas diffusion layer carbon paper substrate prepared in S1, heat and dry it to obtain a Y-PTA working electrode;

[0016] S5. Spraying siloxane on the surface of the Y-PTA working electrode, heating and drying, to obtain the yttrium-doped phosphotungstic acid catalyst.

[0017] Furthermore, the pretreatment time in S1 is 12-18 hours, and the drying temperature is 60-65°C; the pretreated gas diffusion layer carbon paper substrate is cut to an area of ​​1*1.5 cm, and is scribed, and a 1*1 cm catalyst slurry loading area is drawn.

[0018] Furthermore, the concentration of the PTA solution in S2 is 17.3 μmol / mL; the concentration of the YCl3 solution is 10 mg / mL.

[0019] Furthermore, the yttrium doping amount of the Y-PTA in S2 is any one of 0.5%, 0.7%, 1%, and 2%;

[0020] When the yttrium doping amount is 0.5%, the volume ratio of YCl3 solution to PTA solution is 0.549:10;

[0021] When the yttrium doping amount is 0.7%, the volume ratio of YCl3 solution to PTA solution is 0.769:10;

[0022] When the yttrium doping amount is 1%, the volume ratio of YCl3 solution to PTA solution is 1.099:10;

[0023] When the yttrium doping amount is 2%, the volume ratio of YCl3 solution to PTA solution is 2.198:10.

[0024] Furthermore, the dosage of Y-PTA, ethanol, ultrapure water and Nafion solution in S3 is 5 mg: 960 μL: 960 μL: 80 μL.

[0025] Furthermore, the concentration of the catalyst slurry in S3 is 2.5 mg / mL.

[0026] Furthermore, each gas diffusion layer carbon paper substrate in S4 is evenly coated with 40 μL of catalyst slurry, and the content of the loaded Y-PTA is 0.1 mg.

[0027] A second object of the present invention is to provide a yttrium-doped phosphotungstic acid catalyst.

[0028] A third object of the present invention is to provide an application of a yttrium-doped phosphotungstic acid catalyst in the direct synthesis of ammonia by electrocatalytic nitrogen reduction.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. This invention discloses for the first time a yttrium-doped phosphotungstic acid-based catalyst. By regulating the yttrium doping level, catalysts with varying yttrium doping levels can be controllably synthesized, and a supported catalyst electrode is constructed using a gas diffusion layer carbon paper as a substrate. This yttrium-doped phosphotungstic acid-based catalyst overcomes the traditional industrial ammonia synthesis reliance on high temperature, high pressure, and precious metal catalysts. It utilizes a green reaction pathway that directly uses nitrogen as a nitrogen source and uses protons produced by water electrolysis as a hydrogen source. This provides a new paradigm for the development of highly active and stable nitrogen reduction catalysts. Furthermore, this yttrium-doped phosphotungstic acid-based catalyst exhibits high current density and high Faradaic efficiency, enabling the maintenance of a stable reaction current and demonstrating excellent ammonia synthesis yield.

[0031] 2. The yttrium-doped phosphotungstic acid-based catalyst designed in the present invention exhibits excellent electrocatalytic activity and selectivity. First, the PTA material itself has the characteristics of environmental friendliness, low cost, highly adjustable composition and excellent electrochemical stability. The electronic structure of the catalyst is optimized by doping with metallic yttrium, thereby improving the catalyst's adsorption capacity for surface active nitrogen species N*. Secondly, the present invention combines yttrium-doped phosphotungstic acid with the high conductivity and gas diffusion properties of the carbon paper substrate, and constructs an efficient hydrophobic layer on the surface. The hydrophobic properties of Si-O-Si are used to improve the transmission of nitrogen, providing continuous active sites for the reaction. While continuously reducing nitrogen to synthesize ammonia, the "hydrogen evolution" competitive reaction and catalyst dissolution are greatly suppressed, thereby improving the stability of the yttrium-doped phosphotungstic acid-based catalyst, and its ammonia synthesis yield is as high as 40.61μg·mg-1·h-1.

[0032] 3. The present invention provides a method for preparing the yttrium-doped phosphotungstic acid-based catalyst. This method does not require complex equipment and uses readily available raw materials such as yttrium trichloride, PTA, and an ethanol aqueous solution to synthesize a series of yttrium-doped phosphotungstic acid (Y-PTA) in a one-step impregnation process. The freeze-drying process perfectly maintains the integrity of the Keggin structure. At the same time, the ultrasonic spraying technology is innovatively applied to uniformly coat the electrode surface with siloxane, and a Si-O-Si hydrophobic layer is constructed through a spontaneous condensation reaction. The present invention provides a standardized operating process and accurately controls the concentration and coating amount of the catalyst slurry, ensuring the repeatability of the preparation of the yttrium-doped phosphotungstic acid-based catalyst, laying an industrial foundation for the large-scale production of high-performance electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The X-ray powder diffraction pattern of the yttrium-doped phosphotungstic acid catalyst prepared in Examples 1-4 of the present invention;

[0034] Figure 2 1 is a comparison diagram of the linear sweep voltammetry (LSV) curves of the yttrium-doped phosphotungstic acid catalyst under argon and nitrogen conditions in the performance test of the present invention;

[0035] Figure 3 Graph showing ammonia yield and Faraday efficiency of catalysts with different doping amounts in the performance test of the present invention;

[0036] Figure 4 This is a comparison chart of ammonia yield and Faraday efficiency of pure PTA and catalysts with or without a hydrophobic layer in the performance test of the present invention;

[0037] Figure 5 Graph showing ammonia yield and Faraday efficiency of catalysts with and without a hydrophobic layer in the performance test of the present invention after four cycle tests. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with preferred embodiments. The endpoints of the ranges and any values ​​disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0039] Unless otherwise specified, the experimental methods in the following examples are conventional methods and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0040] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0041] Example 1

[0042] This embodiment provides a method for preparing a yttrium-doped phosphotungstic acid catalyst with a yttrium doping amount of 0.5%, comprising the following steps:

[0043] S1. Pre-treat the gas diffusion layer carbon paper substrate by immersing it in 3M H2SO4 for 14 h. Rinse with ultrapure water and dry at 65°C. Cut it into small pieces (1 x 1.5 cm). Mark it with a pencil. Draw a 1 x 1 cm loading area in the 1 x 1.5 cm area for later use.

[0044] S2. Pt-PTA was uniformly dispersed in deionized water to prepare a 17.3 μmol / mL PTA solution, and then 0.549 mL of a 10 mg / mL YCl3 solution was added dropwise. After stirring for 2 h, the mixture was freeze-dried to obtain 0.5% Y-PTA.

[0045] S3, prepare a catalyst slurry with a concentration of 2.5 mg / mL using 5 mg 0.5% Y-PTA, 960 μL ethanol, 960 μL ultrapure water, and 80 μL Nafion solution as raw materials;

[0046] S4, take 40 μL of the catalyst slurry described in S3 and evenly apply it on each piece of small gas diffusion layer carbon paper substrate prepared in S1, and heat and dry it on a hot plate at 60°C to obtain a Y-PTA working electrode;

[0047] S5. Spray siloxane on the surface of the Y-PTA working electrode, and heat and dry it to obtain the 0.5% yttrium-doped phosphotungstic acid catalyst.

[0048] Example 2

[0049] This embodiment provides a method for preparing a yttrium-doped phosphotungstic acid catalyst with a yttrium doping amount of 0.7%, comprising the following steps:

[0050] S1. Pre-treat the gas diffusion layer carbon paper substrate by immersing it in 3M H2SO4 for 12 h. Rinse with ultrapure water and dry at 65°C. Cut into small pieces (1 x 1.5 cm). Mark the pieces with a pencil. Draw a 1 x 1 cm loading area within the 1 x 1.5 cm area for later use.

[0051] S2. Pt-PTA was uniformly dispersed in deionized water to prepare a 17.3 μmol / mL PTA solution, and then 0.769 mL of a 10 mg / mL YCl3 solution was added dropwise. After stirring for 2 h, the mixture was freeze-dried to obtain 0.7% Y-PTA.

[0052] S3, prepare a catalyst slurry with a concentration of 2.5 mg / mL using 5 mg 0.7% Y-PTA, 960 μL ethanol, 960 μL ultrapure water, and 80 μL Nafion solution as raw materials;

[0053] S4, take 40 μL of the catalyst slurry described in S3 and evenly apply it on each piece of small gas diffusion layer carbon paper substrate prepared in S1, and heat and dry it on a hot plate at 60°C to obtain a Y-PTA working electrode;

[0054] S5. Spray siloxane on the surface of the Y-PTA working electrode, and heat and dry to obtain the 0.7% yttrium-doped phosphotungstic acid catalyst.

[0055] Example 3

[0056] This embodiment provides a method for preparing a yttrium-doped phosphotungstic acid catalyst with a yttrium doping amount of 1%, comprising the following steps:

[0057] S1. Pre-treat the gas diffusion layer carbon paper substrate by immersing it in 3M H2SO4 for 15 h. Rinse with ultrapure water and dry at 62°C. Cut it into small pieces (1 x 1.5 cm). Mark it with a pencil. Draw a 1 x 1 cm loading area in the 1 x 1.5 cm area for later use.

[0058] S2. Phosphotungstic acid (PTA) was uniformly dispersed in deionized water to prepare a 17.3 μmol / mL PTA solution, and then 1.099 mL of a 10 mg / mL YCl3 solution was added dropwise. After stirring for 2 h, the mixture was freeze-dried to obtain 1% Y-PTA.

[0059] S3, prepare a catalyst slurry with a concentration of 2.5 mg / mL using 5 mg 1% Y-PTA, 960 μL ethanol, 960 μL ultrapure water, and 80 μL Nafion solution as raw materials;

[0060] S4, take 40 μL of the catalyst slurry described in S3 and evenly apply it on each piece of small gas diffusion layer carbon paper substrate prepared in S1, and heat and dry it on a hot plate at 60°C to obtain a Y-PTA working electrode;

[0061] S5. Spray siloxane on the surface of the Y-PTA working electrode, and heat and dry to obtain the 1% yttrium-doped phosphotungstic acid catalyst.

[0062] Example 4

[0063] This embodiment provides a method for preparing a yttrium-doped phosphotungstic acid catalyst with a yttrium doping amount of 2%, comprising the following steps:

[0064] S1. Pre-treat the gas diffusion layer carbon paper substrate by immersing it in 3M H2SO4 for 18 h. Rinse with ultrapure water and dry at 60°C. Cut it into small pieces (1 x 1.5 cm). Mark it with a pencil. Draw a 1 x 1 cm loading area in the 1 x 1.5 cm area for later use.

[0065] S2. Phosphotungstic acid (PTA) was uniformly dispersed in deionized water to prepare a 17.3 μmol / mL PTA solution, and then 2.198 mL of a 10 mg / mL YCl3 solution was added dropwise. After stirring for 2 h, the mixture was freeze-dried to obtain 2% Y-PTA.

[0066] S3, prepare a catalyst slurry with a concentration of 2.5 mg / mL using 5 mg 2% Y-PTA, 960 μL ethanol, 960 μL ultrapure water, and 80 μL Nafion solution as raw materials;

[0067] S4, take 40 μL of the catalyst slurry described in S3 and evenly apply it on each piece of small gas diffusion layer carbon paper substrate prepared in S1, and heat and dry it on a hot plate at 60°C to obtain a Y-PTA working electrode;

[0068] S5. Spray siloxane on the surface of the Y-PTA working electrode, and heat and dry it to obtain the 2% yttrium-doped phosphotungstic acid catalyst.

[0069] Performance Testing

[0070] 1. Structural characterization

[0071] The crystal phases of the yttrium-doped phosphotungstic acid catalysts prepared in Examples 1-4 were characterized by X-ray powder diffractometer (XRD). The results are as follows: Figure 1 shown.

[0072] Depend on Figure 1 It can be seen that all catalysts present a cubic phase PTA (standard spectrum card number is 50-0304). At the same time, with the increase of metal doping amount, the characteristic peak gradually moves toward the low angle direction, indicating that the preparation method of the present invention can successfully dope metal yttrium into the PTA lattice.

[0073] 2. Electrocatalytic performance test

[0074] The performance of the electrocatalytic synthesis of ammonia using the yttrium-doped phosphotungstic acid catalysts with different yttrium doping amounts prepared in Examples 1-4 was tested using a typical three-electrode system, including a platinum counter electrode, a saturated Ag / AgCl reference electrode, and a yttrium-doped phosphotungstic acid catalyst supported on a carbon paper substrate as a working electrode. The electrolyte composition was 0.1 M Li2SO4, and a linear voltammetric scan was performed in the range of 0 to -1.2 V vs. RHE.

[0075] Test results Figure 2 As shown, compared with the electrolyte in Ar environment, the current density of the catalyst increased significantly under nitrogen conditions, and a clear reduction peak appeared, indicating that the introduction of nitrogen promoted the occurrence of the reaction.

[0076] Test results Figure 3 As shown in Figure 2, the 0.7% Y-PTA catalyst exhibits the best electrocatalytic nitrogen reduction performance, which can reach 27.07 μg·mg at -0.2 V vs. RHE. -1 ·h -1 The ammonia yield was 1.5% and the Faradaic efficiency was 8.8%.

[0077] Test results Figure 4 As shown in Figure 2, after the hydrophobic treatment of the catalyst surface, the 0.7% Y-PTA catalyst exhibited excellent electrocatalytic nitrogen reduction performance, reaching 40.61 μg·mg at -0.2 V vs. RHE. -1 ·h -1 The ammonia yield and Faradaic efficiency of 26.3% were greatly improved compared with those of pure PTA and 0.7% Y-PTA catalyst without hydrophobic treatment.

[0078] Test results Figure 5 As shown in FIG, the cyclic stability diagram of the 0.7% Y-PTA catalyst with and without a hydrophobic layer. It can be seen from the figure that the yield of the catalyst without hydrophobic treatment dropped significantly after 4 cycle tests, while the ammonia yield and Faraday efficiency of the catalyst after hydrophobic treatment remained basically unchanged.

[0079] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a yttrium-doped phosphotungstic acid catalyst, characterized in that: First, yttrium trichloride and phosphotungstic acid (PTA) were used as raw materials to prepare yttrium-doped phosphotungstic acid (Y-PTA) by an impregnation method. Then, a catalyst slurry was prepared using Y-PTA, ethanol, ultrapure water, and Nafion solution as raw materials. The slurry was evenly coated on a gas diffusion layer carbon paper substrate. Siloxane was sprayed on the surface using ultrasonic spraying technology, and the yttrium-doped phosphotungstic acid catalyst was obtained after heating and drying.

2. The method for preparing a yttrium-doped phosphotungstic acid catalyst according to claim 1, wherein: The following steps are involved: S1. Pre-treat the gas diffusion layer carbon paper substrate by immersing it in 3M H2SO4, then rinse it with ultrapure water and dry it, then cut it into small pieces for later use; S2. PTA is evenly dispersed in deionized water to prepare a PTA solution, and then yttrium chloride YCl3 solution is added dropwise. After sufficient stirring, the mixture is freeze-dried to obtain yttrium-doped phosphotungstic acid Y-PTA; S3, preparing a catalyst slurry using the Y-PTA prepared in S2, ethanol, ultrapure water and Nafion solution as raw materials; S4, take the catalyst slurry described in S3 and evenly apply it on the small piece of gas diffusion layer carbon paper substrate prepared in S1, heat and dry it to obtain a Y-PTA working electrode; S5. Spraying siloxane on the surface of the Y-PTA working electrode, heating and drying, to obtain the yttrium-doped phosphotungstic acid catalyst.

3. The method for preparing a yttrium-doped phosphotungstic acid catalyst according to claim 2, wherein: The pretreatment time in S1 is 12-18 hours, and the drying temperature is 60-65° C.; the pretreated gas diffusion layer carbon paper substrate is cut to an area of ​​1*1.5 cm, and is scribed, and a catalyst slurry loading area of ​​1*1 cm is drawn.

4. The method for preparing a yttrium-doped phosphotungstic acid catalyst according to claim 2, wherein: The concentration of the PTA solution in S2 is 17.3 μmol / mL; the concentration of the YCl3 solution is 10 mg / mL.

5. The method for preparing a yttrium-doped phosphotungstic acid catalyst according to claim 2, wherein: The yttrium doping amount of Y-PTA in S2 is any one of 0.5%, 0.7%, 1% and 2%; When the yttrium doping amount is 0.5%, the volume ratio of YCl3 solution to PTA solution is 0.549:10; When the yttrium doping amount is 0.7%, the volume ratio of YCl3 solution to PTA solution is 0.769:10; When the yttrium doping amount is 1%, the volume ratio of YCl3 solution to PTA solution is 1.099:10; When the yttrium doping amount is 2%, the volume ratio of YCl3 solution to PTA solution is 2.198:

10.

6. The method for preparing a yttrium-doped phosphotungstic acid catalyst according to claim 2, wherein: The dosage of Y-PTA, ethanol, ultrapure water and Nafion solution in S3 is 5 mg: 960 μL: 960 μL: 80 μL.

7. The method for preparing a yttrium-doped phosphotungstic acid catalyst according to claim 2, characterized in that: The concentration of the catalyst slurry in S3 is 2.5 mg / mL.

8. The method for preparing a yttrium-doped phosphotungstic acid catalyst according to claim 2, characterized in that: Each gas diffusion layer carbon paper substrate in S4 is evenly coated with 40 μL of catalyst slurry, and the loaded Y-PTA content is 0.1 mg.

9. A yttrium-doped phosphotungstic acid catalyst prepared according to the method of any one of claims 1 to 8.

10. Use of a yttrium-doped phosphotungstic acid catalyst prepared according to the method of any one of claims 1 to 8 in direct synthesis of ammonia by electrocatalytic nitrogen reduction.

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