Citric acid coordination regulated amino-functionalized palladium-silver alloy catalyst as well as preparation method and application thereof

Abstract

The invention discloses a citric acid coordination regulated amino-functionalized palladium-silver alloy catalyst as well as a preparation method and application thereof. Nitrogen-doped carbon is used as a carrier, and the palladium-silver alloy catalyst is constructed through coordination-confinement in-situ reduction of citric acid. According to the preparation method, citric acid is introduced, and synergistic interaction of sub-nano-scale dispersion and efficient interface mass transfer is achieved through dual synergistic regulation and control of the size and the interface; the coordination effect enables the palladium-silver alloy to achieve sub-nano-scale superfine dispersion; as a competitive hydrogen bond acceptor / donor, the polycarboxyl group can effectively break an interface hydrogen bond network and inhibit the formation of a tight gas film from the source. The mechanism ensures that the catalyst is always in full contact with a mixed aqueous solution containing formic acid and formate and hydrogen is quickly released during formic acid dehydrogenation hydrogen production reaction, so that the catalyst has excellent anti-poisoning cycling stability while keeping high intrinsic activity, and the technical problem that high activity and long-term stability are difficult to consider at the same time is solved.

Description

Technical Field

[0001] This invention relates to the field of hydrogen energy and nanocatalytic materials technology, and in particular to an amino-functionalized palladium-silver alloy catalyst with citric acid coordination regulation, its preparation method and application. Background Technology

[0002] Hydrogen energy, as a key carrier in clean energy systems, urgently requires solutions to its storage and transportation challenges for large-scale application. Formic acid (HCOOH) is considered an ideal liquid organic hydrogen carrier (LOHC) due to its high hydrogen storage capacity, wide availability, and mild dehydrogenation conditions. Currently, developing efficient and stable heterogeneous catalysts is crucial for the practical application of this technology.

[0003] However, existing carbon-supported palladium-based catalysts still face multiple challenges in practical applications: On the one hand, the active components are prone to agglomeration, and high surface energy metal nanoparticles are extremely prone to migration and agglomeration, making it difficult to maintain sub-nanometer dispersion, which leads to a decrease in atom utilization. On the other hand, existing catalyst systems, while pursuing high reaction rates, also face a frequently overlooked but highly destructive problem: "interfacial mass transfer failure." Specifically, the rapid release of gas during the formic acid dehydrogenation process easily induces severe interfacial bubbling. Studies have shown that the rigid, strong hydrogen bond network formed by a large number of formate ions and water molecules in the reaction medium significantly enhances the structural strength of the gas-liquid interface film, making it difficult for the generated bubbles to spontaneously rupture. This results in the accumulation of a dense "catalyst-bubble" composite foam layer (similar to Pickering foam) on the catalyst surface. This stable foam layer not only hinders the escape of hydrogen but also easily triggers severe "solid-liquid phase physical isolation," meaning that catalyst particles are easily carried upwards by the rigid bubble film, causing the catalyst to detach from the liquid-phase reaction substrate and become ineffective. At the same time, the accompanying deterioration of the local microenvironment (such as drastic pH changes and formate poisoning) further accelerates the deactivation of the catalyst.

[0004] Current modification techniques for carbon-supported palladium-based catalysts mostly focus on reducing metal particle size or simply modifying the support, failing to address the aforementioned problem of "interfacial mass transfer failure." Furthermore, simple physical stirring cannot fundamentally dismantle the rigid structure maintained by the microscopic, strong hydrogen bond network. Therefore, there is an urgent need to develop a novel catalyst capable of simultaneously achieving sub-nanometer metal dispersion and active regulation of the interfacial hydrogen bond network. This would eliminate the basis for gas film formation at the microscopic level and ensure efficient solid-liquid two-phase contact at the macroscopic level, thereby overcoming the efficiency and stability bottlenecks in formic acid-to-hydrogen production. Summary of the Invention

[0005] The purpose of this invention is to provide an amino-functionalized palladium-silver alloy catalyst with citric acid coordination regulation, its preparation method and application, aiming to solve the technical problems of existing carbon-supported palladium-based catalysts in the formic acid dehydrogenation reaction, such as easy agglomeration of metal particles, low atom utilization, and bubble accumulation caused by strong interfacial hydrogen bonding, solid-liquid physical isolation caused by catalyst being carried to the surface and gas production being hindered.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A first aspect of the present invention provides an amino-functionalized palladium-silver alloy catalyst with citric acid coordination regulation. The catalyst comprises a nitrogen-doped carbon support and citric acid-modified palladium-silver alloy nanoparticles anchored on the surface of the nitrogen-doped carbon support. The catalyst is prepared by a citric acid-assisted coordination-confined in-situ reduction strategy, comprising: forming a palladium-silver-citric acid coordination complex with a palladium precursor, a silver precursor, and citric acid in a liquid phase; and subsequently, under the action of a reducing agent, in-situ reducing the palladium-silver-citric acid coordination complex to a citric acid coordination structure and anchoring it on the surface of the nitrogen-doped carbon support.

[0007] A second aspect of the present invention provides a method for preparing the above-mentioned citric acid-coordination-regulated amino-functionalized palladium-silver alloy catalyst, comprising the following steps: S1. Add carbon material and nitrogen source to deionized water, stir and mix, and then place in an inert atmosphere for high-temperature calcination to obtain an amino-functionalized support, i.e., a nitrogen-doped carbon support. S2. Dissolve the palladium precursor and the silver precursor in citric acid solution, stir and react to obtain a palladium-silver-citric acid complex solution. S3. Disperse the nitrogen-doped carbon support in a solvent to obtain a support suspension. Mix the obtained support suspension with a palladium-silver-citric acid complex solution and stir to allow the palladium-silver-citric acid complex to be adsorbed onto the surface of the nitrogen-doped support to obtain a mixed solution. S4. Add a reducing agent to the mixture to react and obtain the target amino-functionalized palladium-silver alloy catalyst.

[0008] Preferably, in step S1, the high-temperature calcination temperature is 700~900℃ and the calcination time is 2~4 h.

[0009] Preferably, in step S1, the mass ratio of the carbon material to the nitrogen source is 1~2 g: 5~40 g.

[0010] Preferably, in step S1, the carbon material is any one or a combination of two or more of XC-72R carbon black, commercial mesoporous carbon, carbon nanotubes, C3N4, or graphene oxide; and the nitrogen source is any one or a combination of two or more of urea, melamine, or dicyandiamine.

[0011] Preferably, in step S2, the palladium precursor is any one or a combination of two or more of Na2PdCl4, Pd(NO3)2, K2PdCl4, PdCl2 or Pd(OAc)2; and the silver precursor is any one or a combination of two or more of AgNO3, Ag2SO4 or Ag(OAc).

[0012] Preferably, in step S2, the molar ratio of the palladium precursor to the silver precursor is 1:(0.5~2); and the molar ratio of the total molar amount of metallic palladium and metallic silver to citric acid is 1:(1~4).

[0013] Preferably, in step S3, during the process of dispersing the nitrogen-doped carbon support in the solvent, 3-aminopropyltriethoxysilane (hereinafter referred to as APTES) is added for surface modification, so that APTES is uniformly grafted onto the surface of the nitrogen-doped carbon support to obtain an amino-functionalized support suspension.

[0014] Preferably, in step S3, the ratio of nitrogen-doped carbon support to 3-aminopropyltriethoxysilane (APTES) is 0.1~0.5 g: 0.1~1.0 mL.

[0015] Preferably, in step S4, the reducing agent is NaBH4, and the reducing agent is added in the form of an aqueous reducing agent solution with a concentration of 0.5~2.0 mol / L.

[0016] Preferably, in step S4, the reaction is carried out at room temperature and the stirring speed is 400~800 rpm.

[0017] Preferably, in step S4, after the reaction is completed, the reaction product is further centrifuged, washed, and dried. The centrifugation speed is 8000~10000 r / min, the drying temperature is 40~80 ℃, and the drying time is 12~24 h.

[0018] A third aspect of the present invention provides the application of the above-mentioned citric acid-coordinated amino-functionalized palladium-silver alloy catalyst in the dehydrogenation of formic acid to produce hydrogen.

[0019] Preferably, the method of use includes: placing the catalyst and a mixed aqueous solution containing formic acid and formate in a reactor, stirring, and carrying out a dehydrogenation reaction, wherein the catalyst is used such that the molar ratio of palladium metal to formic acid is 1:(50~200), and the recovered product is a mixed gas of hydrogen and carbon dioxide.

[0020] Preferably, in the mixed aqueous solution containing formic acid and formate, the concentration of formic acid is 0.5~3 mol / L, and the molar ratio of formic acid to formate is 1:(1~4). Preferably, the temperature of the dehydrogenation reaction is 25~80℃, and the stirring speed is 100~350 rpm.

[0021] Beneficial effects This invention provides a citric acid-coordination-regulated amino-functionalized palladium-silver alloy catalyst, which is constructed using nitrogen-doped carbon as a support through citric acid coordination-confined in-situ reduction. The catalyst comprises a nitrogen-doped carbon support and citric acid-modified palladium-silver alloy nanoparticles anchored on the surface of the nitrogen-doped carbon support. It is prepared using a citric acid-assisted coordination-confined in-situ reduction strategy, comprising: forming a palladium-silver-citric acid coordination complex with a palladium precursor and a silver precursor in a liquid phase; subsequently, under the action of a reducing agent, the palladium-silver-citric acid coordination complex is in-situ reduced to a citric acid coordination structure and anchored on the surface of the nitrogen-doped carbon support; this citric acid coordination structure can disrupt the formate-water hydrogen bond network.

[0022] This invention utilizes the coordination effect of citric acid to effectively suppress the excessive growth and aggregation of metal crystal nuclei, enabling the palladium-silver alloy to achieve sub-nanometer-scale ultrafine dispersion (average particle size of approximately 0.86 nm) on the surface of a nitrogen-doped carbon support. This extreme dispersion state and the optimization of the electronic structure by the alloy effect provide a high-density intrinsic activity basis for subsequent efficient catalytic reactions.

[0023] This invention utilizes the polycarboxyl groups of citric acid as competitive hydrogen bond acceptors / donors, effectively breaking the rigid hydrogen bond network at the interface. This mechanism dismantles the structural basis of the dense bubbling layer (Pickerlin-like foam) from the source, not only promoting the rapid desorption of the generated gas, but also ensuring that the active sites of the catalyst are always in full contact with the liquid substrate (a mixed aqueous solution containing formic acid and formate). This solves the technical problem in existing formic acid dehydrogenation systems where the rigid hydrogen bond network of formate-water induces bubbling and accumulation, leading to "solid-liquid physical isolation" and obstructed exhaust.

[0024] The citric acid-coordinated amino-functionalized palladium-silver alloy catalyst provided in this invention was applied to the formic acid dehydrogenation reaction. Through the dual synergistic regulation of "size" and "interface," a synergistic effect of "sub-nanometer dispersion" and "efficient interfacial mass transfer" was achieved, resulting in a catalyst exhibiting excellent catalytic activity (TOF > 47,000 h⁻¹). -1 Its excellent resistance to toxic cycling stability contributes to the large-scale application of formic acid to hydrogen production technology.

[0025] The preparation method of this invention is simple to operate, low in cost, highly controllable, and easy to industrialize. Attached Figure Description

[0026] Figure 1 These are high-resolution transmission electron microscopy (HRTEM) morphology comparison images; where (a) is CA-Pd1Ag1 / NC-NH2; and (b) is Pd1Ag1 / NC-NH2. Figure 2 The images show high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images and corresponding elemental energy dispersive spectroscopy (EDS) mapping diagrams of the catalyst prepared in Example 1. Figure 3 Photographs showing the macroscopic interfacial state of the reaction system during the cyclic reaction test using the catalyst; (a) CA-Pd1Ag1 / NC-NH2; (b) Pd1Ag1 / NC-NH2; Figure 4 The curves show the comparison of the cyclic catalytic performance of the catalysts prepared in Example 1 and Comparative Example 1 under the same test conditions. Figure 5 The images show in-situ Raman spectra (a, c) of the evolution of the hydrogen bond network at the interface before and after the reaction of the catalysts prepared in Example 1 and Comparative Example 1, and the corresponding bar charts (b, d) for quantitative analysis of the proportion of strong hydrogen bonds. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0028] Example 1 A method for preparing a citric acid-coordination-regulated amino-functionalized palladium-silver alloy catalyst includes the following steps: (1) Weigh 1.0 g of XC-72R carbon black and 20.0 g of urea and add them to 80 mL of deionized water. Stir at 80℃ for 12 h to allow the urea to fully diffuse into the pores of the carbon black. Then centrifuge and vacuum dry at 60℃ for 12 h. Then place it in a tube furnace and calcine at 800℃ for 2 h under a nitrogen atmosphere. After natural cooling, nitrogen-doped carbon support (NC) is obtained. (2) Weigh 0.1 g of nitrogen-doped carbon support (NC) and disperse it in 5 mL of deionized water. Then add 0.1 mL of APTES and sonicate for 30 min to make APTES uniformly grafted onto the surface of nitrogen-doped carbon support, so as to obtain an amino-functionalized support suspension, i.e., nitrogen-doped carbon support suspension. (3) Dissolve 0.03 g of citric acid in 20 mL of deionized water to obtain a citric acid solution. Then add 0.018 g of Na₂PdCl₄ to the citric acid solution, stir well, and then add 0.6 mL of AgNO₃ solution (0.1 mol / L). Continue stirring for 30 min to allow the citric acid and Pd to react. 2+ Ag + Fully coordinated, forming a homogeneous and stable palladium-silver-citric acid complex solution; (4) The obtained amino-functionalized carrier suspension was poured into the palladium-silver-citric acid complex solution and stirred vigorously at 800 rpm for 30 min. The palladium-silver precursor was directionally adsorbed on the surface of the nitrogen-doped carbon carrier by electrostatic attraction and coordination. (5) While maintaining stirring, slowly add 1.5 mL of NaBH4 solution (1 mol / L) to the mixture and continue stirring for 30 min to ensure complete reduction. After the reaction is complete, centrifuge the reaction product at 10000 r / min for 5 min, wash it three times with deionized water to remove impurity ions, and finally dry the solid product under vacuum at 60℃ for 12 h to obtain the amino-functionalized palladium-silver alloy catalyst regulated by citric acid coordination, labeled as CA-Pd1Ag1 / NC-NH2.

[0029] Example 2 The steps are basically the same as in Example 1, except that the amount of citric acid added in step (3) is 0.02 g. The final catalyst is labeled CA(0.02)-Pd1Ag1 / NC-NH2.

[0030] Example 3 The steps are basically the same as in Example 1, except that in step (3), the amount of AgNO3 solution (1 mol / L) added is 0.3 mL (i.e., Pd:Ag = 2:1). The final catalyst is labeled CA-Pd2Ag1 / NC-NH2. Example 4 The steps are basically the same as in Example 1, except that in step (3), the amount of AgNO3 solution (1 mol / L) added is 1.2 mL (i.e., Pd:Ag = 1:2). The final catalyst is labeled CA-Pd1Ag2 / NC-NH2; Comparative Example 1 The preparation steps are basically the same as in Example 1, except that citric acid is not added in step (3). The final catalyst is labeled as Pd1Ag1 / NC-NH2.

[0031] Comparative Example 2 The preparation steps are basically the same as in Example 1, except that citric acid and AgNO3 solution are not added in step (3), that is, only Na2PdCl4 is added. The final catalyst is labeled as Pd / NC-NH2.

[0032] Comparative Example 3 The preparation steps are basically the same as those in Example 1, except that APTES is not added in step (2) and citric acid and AgNO3 solution are not added in step (3); the final catalyst is labeled as Pd / NC.

[0033] (1) Characterization The catalysts prepared in Example 1 and Comparative Example 1 were characterized, and the TEM results, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images, and corresponding elemental energy dispersive spectroscopy (EDS) mapping diagrams are shown below. Figure 1-2 .

[0034] Depend on Figure 1 (a) The results show that in the catalyst CA-Pd1Ag1 / NC-NH2 prepared in Example 1, the metal component PdAg is dispersed in sub-nanometer ultrafine dispersion on the support surface (average particle size ~0.86 nm).

[0035] Depend on Figure 1 (b) The results show that in the catalyst Pd1Ag1 / NC-NH2 prepared in Comparative Example 1, the metal particles PdAg are significantly aggregated on the surface of the support.

[0036] Depend on Figure 2The results showed that in the catalyst CA-Pd1Ag1 / NC-NH2 prepared in Example 1, Pd and Ag elements were uniformly alloyed and distributed in the nanoparticle structure.

[0037] (2) Catalytic performance test (a) Weigh 0.1 g of the catalyst to be tested, disperse it in 4 mL of deionized water, and transfer it to a three-necked flask equipped with a gas collection device (water displacement method). Place the reaction system in a 60°C oil bath, maintain magnetic stirring at 200 rpm, and check the airtightness of the apparatus. After temperature equilibrium is reached, quickly inject 2 mL of the pre-prepared formic acid / sodium formate (FA / SF) mixed solution using a syringe, and immediately start timing, recording the change in the volume of gas produced over time and the time required to produce 135 mL. Perform qualitative and quantitative analysis of the gas components using gas chromatography (GC).

[0038] (b) To investigate the influence of the reaction microenvironment and catalyst structure, the following test examples were set up: Test Examples 1-4: Using CA-Pd1Ag1 / NC-NH2 prepared in Example 1 as the catalyst, the molar ratio of formic acid (FA) to sodium formate (SF) in the substrate was changed to 1:1, 1:2, 1:3 and 1:4, respectively; Test Examples 5-7: Under the preferred substrate ratio (FA / SF = 1:3), the catalytic performance of Example 2 (low citric acid content), Example 3 (Pd:Ag = 2:1) and Example 4 (Pd:Ag = 2:1) were tested to verify the universality and high efficiency of the catalyst of the present invention in different citric acid modification amounts and metal ratio ranges; Test Examples 8-10: Under the preferred substrate ratio (FA / SF = 1:3), the catalytic performance of Comparative Example 1 (no citric acid), Comparative Example 2 (no Ag) and Comparative Example 3 (no APTES) were tested to analyze the contribution of each component. The results of the formic acid dehydrogenation reaction, analytical results, and calculated conversion frequencies (TOF) for each test case are shown below. Figure 3-5 and Table 1 below. Table 1. Test results of formic acid dehydrogenation performance under different catalysts and reaction conditions

[0039] From Table 1 and Figure 4 The results show that the CA-Pd1Ag1 / NC-NH2 catalyst prepared in Example 1 of this invention exhibits excellent catalytic performance (TOF > 47,000 h⁻¹). -1 The activity decayed very little after 5 cycles, demonstrating excellent resistance to toxicity and cycling stability, while the activity of Comparative Example 1 decreased significantly with increasing cycle number.

[0040] Comparative tests 8-10 confirm that the electronic synergistic effect of Ag and the amination modification of the support surface provide the necessary thermodynamic and kinetic basis for the reaction; while the significant difference between tests 3 and 8 indicates that citric acid (CA) is the key determining factor for achieving a qualitative leap in performance. Furthermore, tests 5-7 further reveal the excellent process versatility of this system: even with reduced citric acid dosage or adjustments to the Pd:Ag ratio over a wide range (2:1~1:2), the catalyst still maintains extremely high activity (TOF>37,000 h⁻¹). -1 Based on the data, it can be seen that the introduction of citric acid in this invention achieves dual synergistic regulation of "size and interface": its coordination-confinement effect enables PdAg alloys to achieve sub-nanometer ultrafine dispersion of 0.86 nm (see...). Figure 1 This maximizes the intrinsic active site density; the experimental results of Comparative Examples 2 and 3 show that the electronic synergistic effect of Ag and the amination modification of the support surface are the basis for constructing an effective catalytic center (both are indispensable).

[0041] Figure 3 (a) Macroscopic photographs show that the macroscopic interface state of the reaction system using the catalyst prepared in Example 1 during the cyclic reaction test is as follows: the reaction liquid surface is clear and there is no bubble accumulation; Figure 3 (b) Macroscopic photographs show that the macroscopic interface state of the reaction system during the cyclic reaction test using the catalyst prepared in Comparative Example 1 is as follows: there is a large amount of dense foam layer formed by the aggregation of bubbles on the surface of the reaction liquid (similar to Pickering foam phenomenon). The above results confirm the existence of solid-liquid physical isolation.

[0042] Figure 5 (a) and Figure 5 (b) The results showed that the catalyst prepared in Comparative Example 1 had a significantly increased relative proportion of strong hydrogen bonds after the cyclic reaction, indicating the formation of a rigid hydrogen bond network. Figure 5 (c) and Figure 5 (d) The results show that, thanks to the introduction of citric acid, the proportion of strong hydrogen bonds in the catalyst prepared in Example 1 remained at a low level before and after the reaction. This result directly confirms that citric acid effectively breaks the long-range ordered hydrogen bond network at the interface through competitive hydrogen bonding, thereby ensuring the continuous unobstructed flow of the gas-liquid interface.

[0043] Based on the above macro photos ( Figure 3 ) and Raman spectroscopy ( Figure 5The results directly show that the polycarboxyl structure of citric acid effectively breaks the rigid formate-water hydrogen bond network at the interface, inhibiting the formation of dense bubbling film from the source and ensuring that the catalyst and the reaction liquid are always in full contact and that hydrogen is released rapidly. This overcomes the key challenges of existing carbon-based formate dehydrogenation catalysts and achieves a perfect balance between high catalyst activity and long-term stability. The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A citric acid-coordination-regulated amino-functionalized palladium-silver alloy catalyst, characterized in that, The catalyst comprises a nitrogen-doped carbon support and citric acid-modified PdAg alloy nanoparticles anchored on the surface of the nitrogen-doped carbon support. The catalyst is prepared by a citric acid-assisted coordination-confined in-situ reduction strategy, comprising: forming a palladium-silver-citric acid coordination complex with a palladium precursor and a silver precursor in a liquid phase; and then, under the action of a reducing agent, reducing the palladium-silver-citric acid coordination complex in situ to a citric acid coordination structure and anchoring it on the surface of the nitrogen-doped carbon support.

2. A method for preparing the citric acid-coordination-regulated amino-functionalized palladium-silver alloy catalyst as described in claim 1, characterized in that, Includes the following steps: S1. Add carbon material and nitrogen source to deionized water, stir and mix, and then place in an inert atmosphere for high-temperature calcination to obtain nitrogen-doped carbon support; S2. Dissolve the palladium precursor and the silver precursor in citric acid solution, stir and react to obtain a palladium-silver-citric acid complex solution. S3. Disperse the nitrogen-doped carbon support in a solvent to obtain a support suspension. Mix the obtained support suspension with a palladium-silver-citric acid complex solution and stir to allow the palladium-silver-citric acid complex to be adsorbed onto the surface of the nitrogen-doped support to obtain a mixed solution. S4. Add a reducing agent to the mixture to react and obtain the target catalyst.

3. The preparation method of the citric acid-coordination-regulated amino-functionalized palladium-silver alloy catalyst according to claim 2, characterized in that, In step S1, the high-temperature calcination temperature is 700~900℃, and the calcination time is 2~4 h; the mass ratio of carbon material to nitrogen source is 1~2 g: 5~40 g; the carbon material is any one or a combination of two or more of XC-72R carbon black, commercial mesoporous carbon, carbon nanotubes, C3N4 or graphene oxide; the nitrogen source is any one or a combination of two or more of urea, melamine or dicyandiamine.

4. The preparation method of a citric acid-coordination-regulated amino-functionalized palladium-silver alloy catalyst according to claim 2, characterized in that, In step S2, the molar ratio of the palladium precursor to the silver precursor is 1:(0.5~2); the molar ratio of the total molar amount of metallic palladium and metallic silver to citric acid is 1:(1~4); the palladium precursor is any one or a combination of two or more of Na2PdCl4, Pd(NO3)2, K2PdCl4, PdCl2 or Pd(OAc)2; and the silver precursor is any one or a combination of two or more of AgNO3, Ag2SO4 or Ag(OAc).

5. The preparation method of a citric acid-coordination-regulated amino-functionalized palladium-silver alloy catalyst according to claim 2, characterized in that, In step S3, during the process of dispersing the nitrogen-doped carbon support in the solvent, 3-aminopropyltriethoxysilane is added for surface modification, so that 3-aminopropyltriethoxysilane is uniformly grafted onto the surface of the nitrogen-doped carbon support to obtain an amino-functionalized support suspension; the ratio of nitrogen-doped carbon support to 3-aminopropyltriethoxysilane is 0.1~0.5 g: 0.1~1.0 mL.

6. The preparation method of a citric acid-coordination-regulated amino-functionalized palladium-silver alloy catalyst according to claim 2, characterized in that, In step S4, the reducing agent is NaBH4, and the reducing agent is added in the form of an aqueous solution of the reducing agent with a concentration of 0.5~2.0 mol / L; the reaction is carried out at room temperature, and the stirring speed is 400~800 rpm.

7. The application of a citric acid coordination-regulated amino-functionalized palladium-silver alloy catalyst as described in any one of claims 1-6 in the dehydrogenation of formic acid to produce hydrogen.

8. The application according to claim 7, characterized in that, The method of using the citric acid-coordinated amino-functionalized palladium-silver alloy catalyst in formic acid dehydrogenation to produce hydrogen includes: placing the catalyst and a mixed aqueous solution containing formic acid and formate in a reactor, stirring, and carrying out the dehydrogenation reaction.

9. The application according to claim 8, characterized in that, In the mixed aqueous solution containing formic acid and formate, the concentration of formic acid is 0.5~3 mol / L, and the molar ratio of formic acid to formate is 1:(1~4).

10. The application according to claim 8, characterized in that, The temperature of the dehydrogenation reaction is 25~80℃, and the stirring speed is 100~350 rpm.

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