Bimetal AuPd alloy porous material as well as preparation method and application thereof

Abstract

The invention discloses a bimetallic AuPd alloy porous material and a preparation method and application thereof.The preparation method comprises the steps that a sodium tetrachloropalladate aqueous solution, a chloroauric acid aqueous solution, cetylpyridinium chloride and water are mixed to be uniform, an ascorbic acid aqueous solution is added under the stirring condition, the mixture is stirred to react till the color of liquid is changed into gray black from yellow transparent, centrifugation is conducted, and a product is obtained; the preparation method comprises the following steps: adding an aqueous solution into a reaction kettle, stirring to obtain a colloidal product, washing the colloidal product to obtain a first precipitate, uniformly mixing the first precipitate with a solvent to obtain a first solution, dripping the first solution onto an electrode, soaking the electrode into a 1H, 1H, 2H, 2H-perfluorooctyltrimethoxysilane ethanol solution, and drying to obtain the bimetallic AuPd alloy porous material. The bimetallic AuPd alloy porous material is applied to nitrogen reduction synthesis of ammonia, the ammonia yield is up to 43.67 [mu] g.h <-1 >. Cm <-2 >, and the Faraday efficiency is up to 43.83%. The bimetallic AuPd alloy porous material is synthesized through a wet reduction method, the ammonia yield is high through the synergistic effect of Au and Pd bimetals, and the bimetallic AuPd alloy porous material can be widely applied to the field of electrocatalytic synthesis of ammonia.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic nitrogen fixation materials, and in particular relates to a bimetallic AuPd alloy porous material and a preparation method and application thereof. Background Art

[0002] Currently, the world requires 150-200 million tons of NH3 annually for use in the chemical, fertilizer, and energy storage industries. With societal development and population growth, demand for NH3 is expected to grow further. Currently, 90% of global NH3 production relies on the Haber-Bosch process. However, the Haber-Bosch process requires high temperature and pressure (200-250 bars, 400-500°C), and the H2 feedstock requires energy-intensive and high-CO2-emitting methane reforming and water-gas shifting technologies to produce it. This results in 500 million tons of CO2 greenhouse gas emissions annually. Therefore, the traditional Haber-Bosch process for producing NH3 is extremely energy-intensive and environmentally unfriendly. Therefore, there is an urgent need to develop novel methods for synthesizing NH3 that can meet the growing global demand for NH3. The concept of "green NH3" has been floated on paper, and the industry has initiated a series of attempts. However, its large-scale application remains plagued by practical challenges of high cost and low energy efficiency. Therefore, the development of materials, including catalysts, electrodes, and adsorbents, as well as the optimization of key processes, are crucial to reducing capital costs and energy consumption. Electrocatalytic nitrogen reduction (NRR) ammonia synthesis technology, a key component of this process, is considered by both industry and science to be a highly efficient, environmentally friendly alternative. Single-atom catalytic materials, due to their specific electronic structure, adjustable atomic coordination environment, and efficient atom utilization, have attracted considerable attention from both academia and industry, and are considered the most challenging alternative to commercial catalysts. Currently, noble metal nanocatalytic materials are widely used in photocatalytic, electrocatalytic, and thermal reactions, particularly in NRR energy catalysis. However, during the synthesis process, the surface energy of metal single atoms increases dramatically, making them prone to agglomeration, thereby affecting the activity and selectivity of the catalytic reaction. The strong bonds of dinitrogen molecules (N2) require large overpotentials for their activation and reduction, hindering NRR performance. Furthermore, during the NRR process, because the metal single atoms and dinitrogen molecules have similar equilibrium potentials, competitive hydrogen evolution reactions occur, further limiting their application in ammonia synthesis. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the present invention aims to provide a method for preparing a bimetallic AuPd alloy porous material.

[0004] Another object of the present invention is to provide a bimetallic AuPd alloy porous material obtained by the above preparation method, in which Pd is uniformly distributed throughout the nanostructure, Au is concentrated in the core position of the nanoparticles, and each nanostructure exhibits porosity.

[0005] Another object of the present invention is to provide the use of the above-mentioned bimetallic AuPd alloy porous material as an electrocatalyst in nitrogen reduction synthesis of ammonia.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] A preparation method of a bimetallic AuPd alloy porous material comprises: uniformly mixing a sodium tetrachloropalladate aqueous solution, a chloroauric acid aqueous solution, cetylpyridinium chloride, and water; adding an ascorbic acid aqueous solution under stirring; stirring and reacting until the liquid changes from yellow transparent to grayish black; centrifuging to obtain a colloidal product; washing the colloidal product to obtain a first precipitate; uniformly mixing the first precipitate and a solvent to obtain a first solution; dripping the first solution onto an electrode; immersing the electrode in a 1H,1H,2H,2H-perfluorooctyltrimethoxysilane ethanol solution; and drying the solution to obtain the bimetallic AuPd alloy porous material on the electrode. The bimetallic AuPd alloy porous material is obtained on the electrode by weight, wherein the ratio of Pd in the sodium tetrachloropalladate aqueous solution to Au in the chloroauric acid aqueous solution is (0.5-4):1.

[0008] In the above technical solution, the stirring reaction time is 2 to 4 hours.

[0009] In the above technical solution, the ratio of Pd in the sodium tetrachloropalladate aqueous solution to Au in the chloroauric acid aqueous solution is preferably (1-2):1, calculated by amount of substance.

[0010] In the above technical solution, the ratio of the mass fraction of the cetylpyridinium chloride, the amount of sodium tetrachloropalladate in the sodium tetrachloropalladate aqueous solution, the amount of ascorbic acid in the ascorbic acid aqueous solution, and the volume fraction of water is (18-20):(0.5-4):(25-30):(4-5), the unit of the mass fraction is mg, the unit of the volume fraction is mL, and the unit of the amount of substance is mol.

[0011] In the above technical solution, the temperature of the stirring reaction is 25-35° C., and the rotation speed of the stirring reaction is 500-600 rpm.

[0012] In the above technical solution, the drying is carried out in a vacuum environment, the drying temperature is 30-40° C., and the drying time is 3-5 hours.

[0013] In the above technical solution, the concentration of sodium tetrachloropalladate in the sodium tetrachloropalladate aqueous solution is 8-10 mM.

[0014] In the above technical solution, the concentration of chloroauric acid in the chloroauric acid aqueous solution is 8 to 10 mM.

[0015] In the above technical solution, the concentration of ascorbic acid in the ascorbic acid aqueous solution is 70-100 mM.

[0016] In the above technical solution, the centrifugal speed is 6000-10000 rpm, and the centrifugal time is 4-6 minutes.

[0017] In the above technical solution, the ratio of the mass fraction of the first precipitate to the volume fraction of the solvent is (4-5):(1-2), the unit of the mass fraction is mg, and the unit of the volume fraction is mL.

[0018] In the above technical solution, the solvent is ethanol.

[0019] In the above technical solution, the 1H,1H,2H,2H-perfluorooctyltrimethoxysilane ethanol solution is a mixture of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane and ethanol.

[0020] In the above technical solution, the concentration of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane in the 1H,1H,2H,2H-perfluorooctyltrimethoxysilane ethanol solution is 0.35-0.55 mM.

[0021] In the above technical solution, the detergents used for washing are water and ethanol.

[0022] In the above technical solution, the soaking time is 30 to 40 minutes.

[0023] The bimetallic AuPd alloy porous material is obtained by the above preparation method.

[0024] In the above technical solution, the water contact angle of the bimetallic AuPd alloy porous material is 153-170°, and the average size is 45-74 nm.

[0025] The above-mentioned bimetallic AuPd alloy porous material is used as an electrocatalyst in nitrogen reduction to synthesize ammonia.

[0026] In the above technical solution, the maximum ammonia yield reached 43.67 μg·h -1 cm -2 , the Faraday efficiency reaches up to 43.83%.

[0027] The present invention adopts a wet reduction method to synthesize a bimetallic AuPd alloy porous material. The preparation method is simple and easy, the required equipment is simple, and the repeatability is high. The synergistic effect of the Au and Pd bimetallics enables a high ammonia yield, enhances N2 chemical adsorption, improves electrical conductivity, and suppresses the characteristics of the hydrogen evolution reaction. The material also has good electrochemical stability and high nitrogen reduction electrocatalytic performance, and can be widely used in the field of electrocatalytic ammonia synthesis. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1( a ) is a transmission electron microscope (TEM) image of the bimetallic AuPd alloy porous material prepared in Example 1;

[0029] FIG1( b ) is a particle size distribution diagram of the bimetallic AuPd alloy porous material prepared in Example 1;

[0030] Figure 2 This is the UV-visible absorption spectrum of the bimetallic AuPd alloy porous material prepared in Example 1;

[0031] Figure 3 This is the X-ray powder diffraction characterization pattern of the bimetallic AuPd alloy porous material prepared in Example 1;

[0032] Figure 4 This is a static water contact angle characterization diagram of the bimetallic AuPd alloy porous material prepared in Example 1;

[0033] Figure 5 The element distribution diagram and element diffraction pattern of Au and Pd in the bimetallic AuPd alloy porous material prepared in Example 1;

[0034] Figure 6 The constant current test results of the glassy carbon electrode loaded with the bimetallic AuPd alloy porous material in Example 1 as the working electrode;

[0035] Figure 7 Graph showing the ammonia yield and ammonia production efficiency of a glassy carbon electrode loaded with the bimetallic AuPd alloy porous material in Example 1 as a working electrode. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below with reference to specific embodiments.

[0037] The raw materials and purchase sources involved in the following examples are as follows: chloroauric acid tetrahydrate (HAuCl4·4H2O, analytical reagent, referred to as AR), sodium tetrachloropalladate (Na2PdCl4, >99.9%) and 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (PFOTMS) were purchased from Shanghai Myril Biochemical Technology Co., Ltd.; cetylpyridinium chloride (C5H5N(Cl)(CH2)15CH3·H2O, HDPC, 99.0-102%) was purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd.; L-ascorbic acid (C6H8O6, 99%) was purchased from Shanghai Aladdin Reagent Co., Ltd.; ethanol (analytical grade) was purchased from Tianjin Fengchuan Chemical Reagent Technology Co., Ltd.

[0038] In the following examples, the sodium tetrachloropalladate aqueous solution was obtained by uniformly mixing sodium tetrachloropalladate with 0.2 mL of water at room temperature.

[0039] In the following examples, the aqueous chloroauric acid solution was obtained by uniformly mixing chloroauric acid tetrahydrate with 0.1 mL of water at room temperature.

[0040] In the following examples, the ascorbic acid aqueous solution was obtained by uniformly mixing L-ascorbic acid with 0.3 mL of water at room temperature.

[0041] The washing in the following examples is as follows: centrifugation, removal of the supernatant, dissolution of the lower precipitate in a detergent, centrifugation, and removal of the supernatant again.

[0042] In the following examples, the glassy carbon electrodes were ultrasonically cleaned for 30 min in sequence with 2 mM dilute nitric acid, 2 mM sodium hydroxide aqueous solution, and ethanol aqueous solution (the mass fraction of ethanol was 42%) before use.

[0043] Examples 1 to 4

[0044] A preparation method of a bimetallic AuPd alloy porous material comprises: adding 0.1 mL of sodium tetrachloropalladate aqueous solution, 0.1 mL of chloroauric acid aqueous solution, 18 mg of cetylpyridinium chloride and 5 mL of H2O into a vial, mixing uniformly, rapidly adding 0.3 mL of freshly prepared ascorbic acid aqueous solution at 25°C and a stirring speed of 600 rpm, sealing the vial, continuously stirring at 35°C and a speed of 600 rpm for 4 hours until the liquid color changes from yellow transparent to gray black, centrifuging at a speed of 8000 rpm for 5 minutes to obtain a colloidal product, washing the colloidal product with water and ethanol twice each, drying it under a vacuum environment at 40°C for 5 hours to obtain a first precipitate, and separating 4 mg of the second precipitate from the first precipitate. A precipitate and 2 mL of solvent (ethanol) were mixed evenly to obtain a first solution, which was dropwise and evenly dripped onto a glassy carbon electrode, and soaked (completely immersed) in 2 mL of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane ethanol solution for 40 minutes, and dried under a vacuum environment at 40°C for 5 hours. A black solid was obtained on the glassy carbon electrode, which was a bimetallic AuPd alloy porous material, wherein the ratio of Pd in the sodium tetrachloropalladate aqueous solution to Au in the chloroauric acid aqueous solution was X, based on the amount of substance. The ratio of the mass fractions of cetylpyridinium chloride, the molar fractions of sodium tetrachloropalladate in the sodium tetrachloropalladate aqueous solution, the molar fractions of ascorbic acid in the ascorbic acid aqueous solution, and the volume fractions of water is Y, the unit of mass fractions is mg, the unit of volume fractions is mL, and the unit of molar fractions is mol. The concentration of sodium tetrachloropalladate in the sodium tetrachloropalladate aqueous solution is 10 mM, the concentration of chloroauric acid in the chloroauric acid aqueous solution is 10 mM, the concentration of ascorbic acid in the ascorbic acid aqueous solution is 100 mM, the ethanol solution of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane is a mixture of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane and ethanol, and the concentration of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane in the ethanol solution of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane is 0.45 mM.

[0045] The X, Y and A values are shown in Table 1.

[0046] Table 1

[0047] Example X Y A(mL) Example 1 2：1 18:2:30:5 0.2 Example 2 4：1 18:4:30:5 0.4 Example 3 1：1 18:1:30:5 0.1 Example 4 0.5：1 18:0.5:30:5 0.05

[0048] The average size of the bimetallic AuPd alloy porous material prepared in Example 1 is: (60.6±6.4) nm; the element diffraction peak shows that the atomic ratio of Au and Pd is 31:69; its diffraction peaks are: 39.9°, 46.4°, 68.0°, 81.8° and 86.4°; the water contact angle of the bimetallic AuPd alloy porous material is (153.9±0.6)°.

[0049] The average size of the bimetallic AuPd alloy porous material prepared in Example 2 is: (54.9±6.7) nm; the element diffraction peak shows that the atomic ratio of Au and Pd is 23:77; its diffraction peaks are: 39.9°, 46.4°, 68.0°, 81.8° and 86.4°; the water contact angle of the bimetallic AuPd alloy porous material is (155.6±1.6)°.

[0050] The average size of the bimetallic AuPd alloy porous material prepared in Example 3 is: (60.8±12.5) nm; the element diffraction peak shows that the atomic ratio of Au and Pd is 48:52; its diffraction peaks are: 39.9°, 46.4°, 68.0°, 81.8° and 86.4°; the water contact angle of the bimetallic AuPd alloy porous material is (159.7±0.4)°.

[0051] The average size of the bimetallic AuPd alloy porous material prepared in Example 4 is: (51.4±6.2) nm; the element diffraction peak shows that the atomic ratio of Au and Pd is 67:33; its diffraction peaks are: 39.9°, 46.4°, 68.0°, 81.8° and 86.4°; the water contact angle of the bimetallic AuPd alloy porous material is (164.9±0.8)°.

[0052] Comparative Example 1

[0053] A method for preparing a single metal Pd porous material comprises: mixing 0.4 mL of sodium tetrachloropalladate aqueous solution, 18 mg of cetylpyridinium chloride and 5 mL of Add H2O to the vial and mix well. Quickly add 0.3mL of freshly prepared ascorbic acid aqueous solution at 25°C with a stirring speed of 600rpm. Seal the vial and let it stand at 25°C for 3 hours (when synthesizing single metal Pd porous materials, in order to ensure the integrity and uniformity of the particle size, static synthesis is adopted) until the liquid color changes from yellow-brown transparent to gray-black. Centrifuge at 8000rpm for 5min to obtain a colloidal product. Wash the colloidal product with water and ethanol twice each, dry it under vacuum at 40°C for 5h to obtain a second precipitate. Mix 4mg of the second precipitate with 2mL of solvent (ethanol) to obtain a second solution. Drop the second solution evenly on the glassy carbon electrode and soak (completely immersed) in 2mL of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane ethanol solution for 40 minutes and dry it under vacuum at 40°C. 5h, the black solid obtained on the glassy carbon electrode is a single metal Pd porous material, wherein the mass fraction of cetylpyridinium chloride, the amount of sodium tetrachloropalladate in the sodium tetrachloropalladate aqueous solution, the amount of ascorbic acid in the ascorbic acid aqueous solution and the volume fraction of water are 18:4:30:5, the unit of mass fraction is mg, the unit of volume fraction is mL, the unit of amount of substance is mol, the amount of sodium tetrachloropalladate in the sodium tetrachloropalladate aqueous solution is 18:4:30:5, the unit of mass fraction is mg, the unit of volume fraction is mL, the unit of amount of substance is mol, the unit ... The concentration of sodium palladium is 20 mM, the concentration of ascorbic acid in the ascorbic acid aqueous solution is 100 mM, the 1H,1H,2H,2H-perfluorooctyltrimethoxysilane ethanol solution is a mixture of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane and ethanol, and the concentration of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane in the 1H,1H,2H,2H-perfluorooctyltrimethoxysilane ethanol solution is 0.45 mM.

[0054] The size of the single metal Pd porous material prepared in Comparative Example 1 is: (60.0±9.1) nm; its diffraction peaks are: 40.0°, 46.7°, 68.1°, 82.1° and 86.5°.

[0055] Comparative Example 2

[0056] A preparation method of a single-metal Au porous material comprises: adding 4.5 mL of a polyvinyl pyrrolidone (PVP) aqueous solution, 0.32 mL of a hydroquinone (HQ) aqueous solution, 0.06 mL of a silver nitrate aqueous solution, and 6.3 microliters of a chloroauric acid aqueous solution into a vial, wherein the concentration of the chloroauric acid in the chloroauric acid aqueous solution is 10 mM; stirring at 25° C. and 600 rpm for 3 minutes; standing for 30 minutes; washing with ammonia water for 1 minute at 600 rpm to remove silver; washing with acetone and ethanol three times; and drying under a vacuum environment at 40° C. for 5 hours to obtain a third precipitate; mixing 4 mg of the third precipitate with 2 mL of a solvent (ethanol) to obtain a third solution; dropping the third solution dropwise and evenly onto a glassy carbon electrode; and mixing in 2 mL of 1H, 1H, 2H, 2H- The sample was immersed (completely immersed) in an ethanol solution of perfluorooctyltrimethoxysilane for 40 minutes and dried under a vacuum environment at 40°C for 5 hours to obtain a brown solid on the glassy carbon electrode, which is a single metal Au porous material. The ratio of polyvinyl pyrrolidone in the polyvinyl pyrrolidone (PVP) aqueous solution, hydroquinone in the hydroquinone aqueous solution, silver nitrate in the silver nitrate aqueous solution, and chloroauric acid in the chloroauric acid aqueous solution is 405:8.96:0.6:0.063, based on the amount of substance, the ethanol solution of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane is a mixture of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane and ethanol, and the concentration of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane in the ethanol solution of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane is 0.45 mM.

[0057] The size of the single-metal Au porous material prepared in comparison 2 is: (185.6±35.7) nm; its diffraction peaks are: 38.3°, 44.5°, 64.7°, 77.7° and 81.8°.

[0058] The bimetallic AuPd alloy porous material obtained in Example 1 was further characterized:

[0059] 1 mg of the bimetallic AuPd alloy porous material prepared in Example 1 was dispersed in 1 mL of ethanol to obtain a first sample solution. 5 μL of the first sample solution was pipetted onto a copper mesh (available from an electron microscope company) and imaged using a Philips Tecnai F20 transmission electron microscope. Figure 1(a) shows a transmission electron microscopy (TEM) image of the bimetallic AuPd alloy porous material prepared in Example 1, illustrating its morphology and size.

[0060] As shown in Figure 1(a), transmission electron microscopy (TEM) images reveal the formation of numerous spherical nanoparticles with interconnected pores. Each bimetallic AuPd alloy porous material exhibits the porous characteristics of highly branched subunits. Vertical channels are formed between adjacent branches, and these channels are oriented in a branching pattern. Figure 1(b) shows the particle size distribution of the bimetallic AuPd alloy porous material prepared in Example 1. Figure 1(b) shows that the average size of the bimetallic AuPd alloy porous material is (60.6±6.4) nm.

[0061] The bimetallic AuPd alloy porous material prepared in Example 1 was dried at 60° C. for 12 hours. The dried bimetallic AuPd alloy porous material (0.5 mg) was dissolved in 3.5 mL of ethanol and tested by UV-visible spectroscopy (instrument model: Mapada V-1200). Figure 2 This is the UV-visible absorption spectrum of the bimetallic AuPd alloy porous material prepared in Example 1. Figure 2 As shown, the bimetallic AuPd alloy porous material exhibits its characteristic localized surface plasmon resonance peak at 620nm, proving that the bimetallic AuPd alloy porous material was successfully synthesized.

[0062] Figure 3 The X-ray powder diffraction characterization diagram of the bimetallic AuPd alloy porous material prepared in Example 1 (instrument model: Bruker GADDS XRD) is as follows: Figure 3 As shown, the X-ray diffraction (XRD) spectrum of the bimetallic AuPd alloy porous material shows typical peaks at 39.9°, 46.4°, 68.0°, 81.8°, and 86.4°, demonstrating the successful bonding of the bimetallic AuPd alloy porous material. This structural characterization provides assurance for the application of the bimetallic AuPd alloy porous material as an electrocatalyst.

[0063] Figure 4 This is a static water contact angle characterization diagram of the bimetallic AuPd alloy porous material prepared in Example 1. Figure 4 As shown, the water contact angle of the bimetallic AuPd alloy porous material is (153.9±0.6)°. 1H,1H,2H,2H-perfluorooctyltrimethoxysilane ethanol solution prevents hydrogen evolution in water, making the bimetallic AuPd alloy porous material have good hydrophobic properties. The hydrophobic surface can effectively suppress the HER and create abundant three-phase contact points for the reactants.

[0064] Figure 5 The element distribution diagram and element diffraction pattern of Au and Pd in the bimetallic AuPd alloy porous material prepared in Example 1 (instrument model: Tecnai F20) are as follows: Figure 5As shown, the corresponding elemental map obtained by high-angle annular dark-field scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (HAADF-STEM-EDS) clearly shows that Pd is uniformly distributed throughout the nanostructure, while Au is concentrated in the core of the nanostructure. This indicates the successful formation of the nanoporous structure. Energy-dispersive X-ray spectroscopy (EDS) analysis was used to determine the elemental composition of the bimetallic AuPd alloy porous material. By analyzing the EDS spectrum, the signals at 2.9, 9.7, and 11.5 eV were attributed to Pd-L, Au-Lα, and Au-Lβ, respectively, and the atomic ratio of Au to Pd was 31:69.

[0065] Constant current test: A glassy carbon electrode loaded with the bimetallic AuPd alloy porous material in Example 1 was used as the working electrode, Ag / AgCl (model: R0305, purchased from Tianjin Aida Hengsheng Technology Development Co., Ltd.) was used as the reference electrode, and a platinum sheet was used as the counter electrode. The working electrode, the reference electrode, and the counter electrode were placed in an electrode cell containing 200 mL of electrolyte (the electrolyte in the electrolyte was Na2SO4, the solvent was water, and the concentration of the electrolyte in the electrolyte was 0.1 M). The pH of the electrolyte was 7, and nitrogen was introduced for at least half an hour to remove impurity gases in the electrolyte, so that it was in a nitrogen saturated state, and finally the electrocatalytic reaction was started. The constant current method test was performed using an electrochemical workstation (HYFSim, JRT Chen, CSL Koh, et al., Angew. Chem. Int. Ed. 59 (2020) 16997-17003). The voltages applied in the constant current test were -0.8 V, -0.75 V, -0.7 V, -0.65 V, -0.6 V, and -0.55 V (reversible hydrogen electrode potential), respectively. The constant current test time was 2 hours, and nitrogen was maintained during the test. Among them, the voltage value conversion formula compared to the reversible hydrogen electrode is E (vs RHE) = E (vs Ag / AgCl) + 0.0592 * pH + 0.1976, E (vs RHE) is the relative voltage of the working electrode compared to the reversible hydrogen electrode, E (vs Ag / AgCl) is the relative voltage of the working electrode compared to the reference electrode Ag / AgCl, and pH is the acidity and alkalinity of the electrolyte. After the test, 2 mL of the electrolyte was taken for indigo blue spectrophotometry to measure the ammonia concentration and calculate the ammonia yield and ammonia production efficiency. The electrochemical workstation model was Shanghai Chenhua CHI760E.

[0066] Figure 6 The constant current test results of the glassy carbon electrode loaded with the bimetallic AuPd alloy porous material prepared in Example 1 are shown in FIG. Figure 6 It can be seen that during the 2-hour constant current test, the current remained basically constant, proving the stability of the bimetallic AuPd alloy porous material as an electrocatalyst, and the Faraday efficiency was further calculated based on this current value. Figure 7 The graphs are as follows: ammonia yield and ammonia production efficiency of the glassy carbon electrode loaded with the bimetallic AuPd alloy porous material prepared in Example 1. Figure 7 It can be seen that when the glassy carbon electrode loaded with the bimetallic AuPd alloy porous material in Example 1 is used as the working electrode, it has excellent ammonia production and high Faradaic efficiency, with an ammonia production of 43.67 μg·h -1 cm -2 , with a Faradaic efficiency of 43.83%. Furthermore, the bimetallic AuPd alloy porous material also exhibits satisfactory selectivity and good stability for long-term NRR. This demonstrates the feasibility of the bimetallic AuPd alloy porous material as an electrocatalyst for practical ammonia production.

[0067] The glassy carbon electrode loaded with the single metal Pd porous material in Comparative Example 1 and the glassy carbon electrode loaded with the single metal Au porous material in Comparative Example 2 were used as working electrodes to test ammonia production and Faraday efficiency, respectively. The test method was basically the same as the aforementioned "constant current test" method.

[0068] The glassy carbon electrode loaded with the single metal Pd porous material in Comparative Example 1 produced 6.8 μg·h of ammonia in a -0.6 V constant current test. -1 cm -2 , the Faraday efficiency is 0.5%. The glassy carbon electrode loaded with the single metal Au porous material in Comparative Example 2 produces 0.5 μg·h of ammonia in a -0.6 V constant current test. -1 cm -2 , the Faradaic efficiency is 1.8%.

[0069] The method for testing ammonia concentration using indigo blue spectrophotometry and calculating ammonia yield and ammonia production efficiency is as follows:

[0070] 1. Prepare solution A, solution B, and solution C. Solution A is a mixture of NaOH, salicylic acid, trisodium citrate, and water. The concentration of NaOH in solution A is 1 M, the concentration of salicylic acid is 5 wt%, and the concentration of trisodium citrate is 5 wt%. Solution B is an aqueous solution of NaClO with a concentration of 0.05 M. Solution C is an aqueous solution of sodium nitroprusside (C5FeN6Na2O) with a concentration of 1 wt%.

[0071] A standard curve of ammonia concentration-absorbance was established. 2 mL of ammonium chloride aqueous solution was added to each of 10 20 mL glass bottles. The concentrations of ammonium chloride in the aqueous solution were 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, and 0.10 mmol·L. -1, 2 mL of solution A, 1 mL of solution B, and 0.2 mL of solution C were added to each glass bottle in sequence, and the mixture was allowed to react at room temperature for two hours to obtain a first mixed solution. The absorption spectrum of the first mixed solution was measured using an ultraviolet-visible spectrometer. The concentrations of different ammonium chloride in the ammonium chloride aqueous solution (0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10 mmol·L -1 ) and the peak value (absorbance) of the absorption spectrum corresponding to each ammonium chloride concentration to establish a standard function curve: y = 0.06862 + 8.20634x (x: concentration of ammonium chloride in ammonium chloride aqueous solution, y: absorbance).

[0072] 2. In a 20 mL glass bottle, 2 mL of electrolyte after constant current reaction was added, and then 2 mL of solution A, 1 mL of solution B and 0.2 mL of solution C were added in sequence. The mixture was allowed to react at room temperature for two hours to obtain a second mixed solution. The absorption spectrum of the second mixed solution was measured using an ultraviolet-visible spectrometer. The peak value (absorbance) of the absorption spectrum was substituted into the above standard function curve as y. The measured x value was the concentration of ammonia, and then the formula was used. Calculate the yield of ammonia, Calculate the ammonia production efficiency, i.e., the Faraday efficiency. NH3 is the yield of ammonia, c NH3 is the concentration of ammonia obtained by the standard function curve, V is the volume of the electrolyte (200 mL), t is the constant current method test time (2 h), A cat . is the area of the bimetallic AuPd alloy porous material (0.07065cm 2 ), F is the Faraday constant, and I is the current value in the constant current method test.

[0073] The bimetallic AuPd alloy porous materials prepared in Examples 2 to 4 can achieve the same technical effects as the bimetallic AuPd alloy porous material prepared in Example 1.

[0074] The above is an exemplary description of the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by other skilled in the art without expending creative labor falls within the scope of protection of the present invention.

Claims

1. A method for preparing a bimetallic AuPd alloy porous material, characterized in that: include: A sodium tetrachloropalladate aqueous solution, a chloroauric acid aqueous solution, cetylpyridinium chloride, and water are uniformly mixed, an ascorbic acid aqueous solution is added under stirring, and the mixture is stirred and reacted until the color of the liquid changes from yellow transparent to grayish black, and the mixture is centrifuged to obtain a colloidal product. The colloidal product is washed to obtain a first precipitate, and the first precipitate and a solvent are uniformly mixed to obtain a first solution. The first solution is dropped onto an electrode, and the electrode is immersed in a 1H,1H,2H,2H-perfluorooctyltrimethoxysilane ethanol solution, and dried to obtain a bimetallic AuPd alloy porous material, wherein, based on the amount of substance, the ratio of Pd in the sodium tetrachloropalladate aqueous solution to Au in the chloroauric acid aqueous solution is (0.5-4):

1.

2. The preparation method according to claim 1, characterized in that The ratio of the mass fractions of the cetylpyridinium chloride, the amount of sodium tetrachloropalladate in the sodium tetrachloropalladate aqueous solution, the amount of ascorbic acid in the ascorbic acid aqueous solution, and the volume fractions of water is (18-20):(0.5-4):(25-30):(4-5), the unit of the mass fractions is mg, the unit of the volume fractions is mL, and the unit of the amount of substance is mol.

3. The preparation method according to claim 1, characterized in that The ratio of the mass fraction of the first precipitate to the volume fraction of the solvent is (4-5):(1-2), the unit of the mass fraction is mg, the unit of the volume fraction is mL, and the solvent is water.

4. The preparation method according to claim 1, characterized in that The concentration of sodium tetrachloropalladate in the sodium tetrachloropalladate aqueous solution is 8-10 mM; the concentration of chloroauric acid in the chloroauric acid aqueous solution is 8-10 mM; and the concentration of ascorbic acid in the ascorbic acid aqueous solution is 70-100 mM.

5. The preparation method according to claim 1, characterized in that The stirring reaction time is 2 to 4 hours.

6. The preparation method according to claim 1, characterized in that The 1H,1H,2H,2H-perfluorooctyltrimethoxysilane ethanol solution is a mixture of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane and ethanol, and the solvent is ethanol.

7. The bimetallic AuPd alloy porous material obtained by the preparation method according to any one of claims 1 to 6.

8. The bimetallic AuPd alloy porous material according to claim 7, characterized in that: The water contact angle of the bimetallic AuPd alloy porous material is 153-170 degrees, and the average size is 45-74 nm.

9. Use of the bimetallic AuPd alloy porous material as claimed in claim 7 as an electrocatalyst in nitrogen reduction to synthesize ammonia.

10. The use according to claim 9, characterized in that The maximum ammonia yield reached 43.67 μg·h -1 cm -2 , the Faraday efficiency reaches up to 43.83%.

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