Hydrothermal synergistic reduction preparation method of high-ammoxidation-activity PtMoNi medium-entropy alloy catalyst
The preparation of PtMoNi medium-entropy alloy catalysts via a hydrothermal synergistic reduction method solves the problems of catalyst stability and precious metal resources in fuel cells, and achieves improved catalytic performance and enhanced stability of efficient ammonia oxidation reaction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-16
- Publication Date
- 2026-04-03
AI Technical Summary
Existing fuel cells suffer from low energy conversion efficiency, poor catalyst stability, and scarce precious metal resources that are easily poisoned by ammonia oxidation reaction intermediates, making it difficult to apply Pt-based catalysts on a large scale.
A PtMoNi medium-entropy alloy catalyst was prepared by a hydrothermal synergistic reduction method. By optimizing the adsorption energy of the reaction intermediate and forming a defect structure with high reactivity through electron redistribution and synergistic regulation among multiple metals, the catalytic performance was improved.
It significantly improves the ammonia oxidation activity and stability of the catalyst, reduces the risk of precious metal poisoning, simplifies the preparation process, and facilitates large-scale production.
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Figure CN121775868A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of new energy materials technology, specifically to a hydrothermal synergistic reduction preparation method for a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst. Background Technology
[0002] Against the backdrop of environmental pollution and the energy crisis, ammonia (NH3) is increasingly valued as a hydrocarbon-free carrier and direct fuel. Ammonia is a promising carbon-free fuel with high energy density (13 MJ / L), high hydrogen content (17.6 wt%), and mature existing infrastructure. The ammonia catalytic oxidation (AOR) reaction is a key process in the anode reaction of ammonia fuel cells. This reaction aims to efficiently and selectively oxidize NH3 to N2, releasing electrons and protons. However, AOR is a complex six-electron transfer process with extremely slow reaction kinetics and is subject to competing hydrogen evolution reaction (HER) and nitrogen oxide (NOx) reactions. x The generation pathways of byproducts such as fuel cells lead to low energy conversion efficiency and poor catalyst stability, which seriously restricts their further development.
[0003] Currently, catalysts used for AOR (Aluminum Oxide Reaction) primarily rely on noble metal-based materials such as platinum (Pt), iridium (Ir), and ruthenium (Ru). Although these catalysts exhibit high initial activity, their large-scale application is hindered by the scarcity and high cost of noble metal resources, and the susceptibility of noble metal surfaces to poisoning by AOR reaction intermediates (especially strongly adsorbed *N species), leading to the occupation of active sites or catalyst deactivation. To overcome these problems, those skilled in the art have explored alloying platinum with non-noble metal catalysts (such as Ni, Co, and Cu) or forming composite materials through interface engineering to optimize the inherent properties of platinum. Although these studies have yielded some improvements, their AOR performance is still inferior to that of hydroxide oxidase, highlighting the urgent need for further catalyst optimization.
[0004] In recent years, enhancing the activity and stability of catalysts through multi-metal synergistic regulation has become a research hotspot. Studies have shown that the electronic and lattice effects between metals can effectively modulate the d-orbital structure and surface adsorption energy of Pt, thereby significantly optimizing the adsorption-desorption behavior of reaction intermediates. This multi-metal electronic effect can not only regulate *NH4+... xThe adsorption strength of intermediates can prevent reaction hindrance caused by excessively strong or weak adsorption, and can also promote the formation of reactive defect structures around specific active sites in the alloy system, such as oxygen vacancies or low-coordination metal sites, thereby effectively reducing the reaction energy barrier of AOR and improving the reaction kinetics of key steps. Nevertheless, precise control of the element ratios in multi-metal systems and the controllable growth of nanostructures remain significant challenges. Therefore, developing a simple alloy preparation strategy that enables synergistic control of multiple metals is of great importance for constructing highly active and stable ammonia oxidation catalysts. Summary of the Invention
[0005] Technical problems solved: This application addresses the shortcomings of existing technologies by solving the following problems: low energy conversion efficiency of fuel cells, poor catalyst stability, scarcity and high price of precious metal resources, easy poisoning of precious metal surfaces by AOR reaction intermediates, high cost of precious metal Pt in ammonia oxidation applications, Pt susceptibility to poisoning by reaction intermediate *N, and poor long-term stability, which lead to the occupation of active sites or catalyst deactivation, making it difficult to apply on a large scale. This application provides a hydrothermal synergistic reduction preparation method for a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst.
[0006] Objective of the Invention: This application discloses a hydrothermal synergistic reduction method for preparing a high-ammonia oxidation activity PtMoNi medium-entropy alloy catalyst. Through the electron redistribution and synergistic regulation effect among multiple metals, the *NH4+ oxidation process is effectively optimized. x The adsorption energies of dehydrogenation intermediates and hydroxyl intermediates are optimized; at the same time, the synergistic effect of multiple elements can induce the formation of defect structures and local microenvironments with high reactivity, thereby reducing the energy barrier of AOR and improving charge transfer efficiency, which greatly enhances the catalytic performance of Pt4Mo4Ni1 / C; in addition, this strategy also provides a research basis for a deeper understanding of the structure-activity relationship of multi-metal structure regulation and interface electronic effects in AOR, and provides theoretical support and material design ideas for the subsequent development of efficient, stable and more resource-efficient ammonia oxidation catalysts.
[0007] To achieve the above objectives, this application provides the following technical solution: A hydrothermal synergistic reduction method for preparing a high ammonia oxidation activity PtMoNi medium-entropy alloy catalyst specifically includes the following steps: Step 1: Mix 2.3-2.7 parts platinum source, 1.7-2 parts molybdenum source, 0.3-0.5 parts nickel source, 4.8-5.2 parts glucose, 1.7-2 parts hexadecyltrimethylammonium chloride, and 0.1-0.2 parts carbon black in a 50 mL hydrothermal reactor to form system A. Step 2: Add 16 parts of N,N-dimethylformamide to system A to obtain solution B; Step 3: Place solution B in a magnetic stirrer and stir to obtain solution C; Step 4: Place the hydrothermal reactor containing solution C into an electric thermostatic drying oven and heat it to the required temperature; Step 5: After cooling, centrifuge and wash the sample, and place the sample in a vacuum drying oven. Dry it under vacuum at 60°C for 8 hours to finally obtain a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst.
[0008] Furthermore, in the first step, the platinum source is platinum acetylacetonate, the molybdenum source is molybdenum hexacarbonyl, and the nickel source is nickel acetylacetonate.
[0009] Furthermore, in the first step, the mass ratio of molybdenum hexacarbonyl, platinum acetylacetonate, and nickel acetylacetonate is molybdenum hexacarbonyl: platinum acetylacetonate: nickel acetylacetonate = 1.9: 2.5: 0.4.
[0010] Furthermore, in the first step, the glucose is glucose monohydrate with a concentration of 5 mg / mL.
[0011] Furthermore, in the first step, the concentration of hexadecyltrimethylammonium chloride is 1.875 mg / mL.
[0012] Furthermore, in the first step, the carbon black is XC-72 carbon black with a concentration of 0.125 mg / mL.
[0013] Furthermore, in the third step, the magnetic stirrer is used at a speed of 300-500 rpm, the stirring time is 3-6 hours, and the stirring temperature is 20-30℃.
[0014] Furthermore, the heating in the fourth step is a staged heating process. The first stage temperature is 75-85℃, and the temperature is maintained for 2.8-3.2 h. The second stage temperature is 145-155℃, and the temperature is maintained for 2.8-3.2 h.
[0015] Furthermore, in the fifth step, the solvent for centrifugal washing is a mixture of ethanol and acetone, with a volume ratio of ethanol to acetone of 1:1, and the washing is performed 3-4 times with the ethanol and acetone mixture.
[0016] Furthermore, the high ammonia oxidation activity PtMoNi medium entropy alloy catalyst in the fifth step is Pt4Mo4Ni1 / C.
[0017] Explanation of the principle: A dual reduction system is constructed using CO molecules released from the in-situ decomposition of molybdenum hexacarbonyl at high temperature and glucose. Under the micellar confinement of hexadecyltrimethylammonium chloride (CTAC), highly dispersed active sites of PtMoNi nanoalloys are achieved. MoO formed from the in-situ decomposition of Mo... xIt can be incorporated into the alloy lattice or distributed on the particle surface, providing electronic modulation capabilities and surface defect sites, enhancing electron transport efficiency and forming more active sites; this alloy structure effectively modulates the d-band center of Pt through the electron redistribution effect among multiple metals, optimizing *NH x The adsorption strength and desorption behavior of *OH promote the overall charge transfer rate and accelerate the ammonia oxidation reaction kinetics.
[0018] This application provides a hydrothermal synergistic reduction method for preparing a high-ammonia oxidation-active PtMoNi medium-entropy alloy catalyst, which has the following advantages compared with the prior art: 1. The catalyst prepared by the method described in this application is a Pt4Mo4Ni1 / C with a synergistic effect, which exhibits uniform distribution on XC-72 carbon black; 2. The catalyst Pt4Mo4Ni1 / C prepared by the method disclosed in this invention effectively optimizes the electronic structure and lattice parameters of Pt atoms through the synergistic effect of Pt, Mo, and Ni at the atomic scale, while also optimizing *NH4+. x The adsorption / desorption behavior of the *OH intermediate effectively reduces the adsorption energy of AOR kinetics, thereby achieving higher ammonia oxidation performance; 3. The catalyst prepared by the method disclosed in this invention has a PtMoNi ternary alloy structure, which can suppress the strong adsorption of *N on the Pt surface, reduce the risk of catalyst poisoning, and enhance the structural stability of the catalyst under long-term cycling or high-potential conditions. 4. The preparation method is simple and controllable. It adopts a hydrothermal stage heating method combined with organic precursors and reducing agents to make the multi-metal alloy uniformly distributed on the carbon support. The operating conditions are mild and easy to scale up, making it more practical and controllable. 5. During the experimental testing, the Pt4Mo4Ni1 / C ratio, measured by cyclic voltammetry (CV) in a 1 M KOH + 0.1 M NH3 electrolyte, reached 22.4 mA cm⁻¹. -2 The current density is higher than that of PtIr / C, which is 1.3 mA cm⁻¹. -2 . Attached Figure Description
[0019] Figure 1 This is a scanning electron microscope image of the Pt4Mo4Ni1 / C catalyst obtained in Example 1 of this application; Figure 2 The CV curves show the catalytic activity of the Pt4Mo4Ni1 / C catalyst obtained in Example 1 of this application for ammonia oxidation in alkaline 1 M KOH and alkaline 1 M KOH + 0.1 M NH3 solutions. Figure 3This is a performance comparison chart of the Pt4Mo4Ni1 / C catalyst obtained in Example 1 of this application and the commercial PtIr / C catalyst. Detailed Implementation
[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0021] Example 1: A hydrothermal synergistic reduction method for preparing a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst, comprising the following steps: Step 1: Mix 1.9 parts of molybdenum hexacarbonyl, 2.5 parts of platinum acetylacetonate, 0.4 parts of nickel acetylacetonate, 5 parts of glucose monohydrate, 1.9 parts of hexadecyltrimethylammonium chloride, and 0.1 parts of carbon black according to the mass ratio, and place them in a 50 mL hydrothermal reactor to prepare system A. The concentration of glucose monohydrate is 5 mg / mL, the concentration of hexadecyltrimethylammonium chloride is 1.875 mg / mL, and the carbon black is XC-72 carbon black with a concentration of 0.125 mg / mL. Step 2: Add 16 parts of N,N-dimethylformamide to system A to obtain solution B; Step 3: Place solution B in a magnetic stirrer and stir for 3 hours at 25°C and 400 rpm to obtain solution C; Step 4: Place solution C in an electric thermostatic drying oven and heat it in stages. The first stage temperature is 80-85℃, and the temperature is maintained for 3-3.2 hours. The second stage temperature is 150-155℃, and the temperature is maintained for 3-3.2 hours. Step 5: After the heating reaction is complete, wash the sample 3-4 times with a 1:1 mixture of ethanol and acetone, and then place the sample in a vacuum drying oven and dry it under vacuum at 60°C for 8 hours to finally obtain the high ammonia oxidation activity PtMoNi medium entropy alloy catalyst Pt4Mo4Ni1 / C.
[0022] The obtained Pt4Mo4Ni1 / C catalyst was observed by scanning electron microscopy (SEM), as follows: Figure 1 As shown, the obtained Pt4Mo4Ni1 / C has a good degree of alloying, and the Pt4Mo4Ni1 / C catalyst is uniformly deposited on carbon.
[0023] Electrochemical testing: (1) Preparation of catalytic electrode: Electrochemical tests were performed on a rotating disk apparatus. For AOR testing, this application used a standard three-electrode system, with the prepared sample used as the working electrode, a platinum mesh as the counter electrode, and a standard Hg / HgO electrode as the reference electrode. The electrolyte used was 1 M KOH + 0.1 M NH3, with the pH set at 14.
[0024] (2) AOR activity test: At 5 mV s -1 CV curves were obtained at the scan rate.
[0025] Figure 2 The Pt4Mo4Ni1 / C catalyst obtained in Example 1 of this invention exhibits a potential range of -0.8 V to 0.1 V (relative to a mercury oxide electrode) in 1 M KOH and 1 M KOH + 0.1 M NH3 at a scan rate of 5 mV s. -1 The CV curves are shown in the figure. The black line represents the CV curve in 1 M KOH, and the red line represents the CV curve in 1 M KOH + 0.1 M NH3. It can be seen from the figure that the Pt4Mo4Ni1 / C catalyst has excellent catalytic performance.
[0026] Figure 3 The Pt4Mo4Ni1 / C catalyst obtained in Example 1 of this invention was tested in 1 M KOH + 0.1 M NH3 at a potential range of -0.8 V to 0.1 V (relative to a mercury oxide electrode) with a scan rate of 5 mV s. -1 The CV curves show that the current density of the Pt4Mo4Ni1 / C catalyst is significantly higher than that of the commercial PtIr / C catalyst.
[0027] Example 2, a hydrothermal synergistic reduction preparation method for a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst, comprising the following steps: Step 1: Mix 1.8 parts of molybdenum hexacarbonyl, 2.5 parts of platinum acetylacetonate, 0.4 parts of nickel acetylacetonate, 5 parts of glucose monohydrate, 1.9 parts of hexadecyltrimethylammonium chloride, and 0.1 parts of carbon black according to the mass ratio and place them in a 50 mL hydrothermal reactor to prepare system A; Step 2: Add 16 parts of N,N-dimethylformamide to system A to obtain solution B; Step 3: Place solution B in a magnetic stirrer and stir for 3 h at 30 ℃ and 400 rpm to obtain solution C; Step 4: Place solution C in an electric thermostatic drying oven and heat it in stages. The first stage temperature is 80 ℃ and the temperature is maintained for 3 h; the second stage temperature is 150 ℃ and the temperature is maintained for 3 h. Step 5: After the heating reaction is complete, wash the sample 3-4 times with a 1:1 mixture of ethanol and acetone, and then place the sample in a vacuum drying oven and vacuum dry at 60 °C for 8 hours to finally obtain the high ammonia oxidation activity PtMoNi medium entropy alloy catalyst Pt4Mo4Ni1 / C.
[0028] Example 3, a hydrothermal synergistic reduction method for preparing a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst, comprising the following steps: Step 1: Mix 2 parts of molybdenum hexacarbonyl, 2.6 parts of platinum acetylacetonate, 0.4 parts of nickel acetylacetonate, 5 parts of glucose monohydrate, 1.9 parts of hexadecyltrimethylammonium chloride, and 0.2 parts of carbon black according to the mass ratio and place them in a 50 mL hydrothermal reactor to prepare system A; Step 2: Add 16 parts of N,N-dimethylformamide to system A to obtain solution B; Step 3: Place solution B in a magnetic stirrer and stir for 3 hours at 25 ℃ and 400 rpm to obtain solution C; Step 4: Place solution C in an electric thermostatic drying oven and heat it in stages. The first stage temperature is 78 ℃ and the temperature is maintained for 3.2 h; the second stage temperature is 155 ℃ and the temperature is maintained for 3 h. Step 5: After the heating reaction is complete, wash the sample 3-4 times with a 1:1 mixture of ethanol and acetone, and then place the sample in a vacuum drying oven and vacuum dry at 60 °C for 8 hours to finally obtain the high ammonia oxidation activity PtMoNi medium entropy alloy catalyst Pt4Mo4Ni1 / C.
[0029] In summary, the high ammonia oxidation activity PtMoNi medium entropy alloy catalyst Pt4Mo4Ni1 / C prepared by the method of the present invention has excellent ammonia oxidation reaction catalytic activity, that is, excellent ammonia oxidation reaction activity and good stability. The preparation process is simple, low cost and easy to industrial-scale production.
[0030] The foregoing description has fully disclosed the specific embodiments of the present invention. It should be noted that any modifications made to the specific embodiments of the present invention by those skilled in the art do not depart from the scope of the claims. Accordingly, the scope of the claims is not limited to the foregoing specific embodiments.
Claims
1. A method for preparing a high-ammonia oxidation-active PtMoNi medium-entropy alloy catalyst by hydrothermal synergistic reduction, characterized in that, Includes the following steps: Step 1: Mix 2.3-2.7 parts platinum source, 1.7-2 parts molybdenum source, 0.3-0.5 parts nickel source, 4.8-5.2 parts glucose, 1.7-2 parts hexadecyltrimethylammonium chloride, and 0.1-0.2 parts carbon black in a 50 mL hydrothermal reactor to form system A. Step 2: Add 16 parts of N,N-dimethylformamide to system A to obtain solution B; Step 3: Place solution B in a magnetic stirrer and stir to obtain solution C; Step 4: Place the hydrothermal reactor containing solution C into an electric thermostatic drying oven and heat it to the required temperature; Step 5: After cooling, centrifuge and wash the sample, and place the sample in a vacuum drying oven. Dry it under vacuum at 60°C for 8 hours to finally obtain a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst.
2. The hydrothermal synergistic reduction preparation method of a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst according to claim 1, characterized in that: In the first step, the platinum source is platinum acetylacetonate, the molybdenum source is molybdenum hexacarbonyl, and the nickel source is nickel acetylacetonate.
3. The hydrothermal synergistic reduction preparation method of a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst according to claim 2, characterized in that: In the first step, the mass ratio of molybdenum hexacarbonyl, platinum acetylacetonate, and nickel acetylacetonate is molybdenum hexacarbonyl: platinum acetylacetonate: nickel acetylacetonate = 1.9: 2.5: 0.
4.
4. The hydrothermal synergistic reduction preparation method of a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst according to claim 1, characterized in that: In the first step, the glucose is glucose monohydrate with a concentration of 5 mg / mL.
5. The hydrothermal synergistic reduction preparation method of a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst according to claim 1, characterized in that: In the first step, the concentration of hexadecyltrimethylammonium chloride is 1.875 mg / mL.
6. The hydrothermal synergistic reduction preparation method of a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst according to claim 1, characterized in that: The carbon black used in the first step is XC-72 carbon black, and the concentration of XC-72 carbon black is 0.125 mg / mL.
7. The hydrothermal synergistic reduction preparation method of a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst according to claim 1, characterized in that: In the third step, the magnetic stirrer is used at a speed of 300-500 rpm for 3-6 hours and at a temperature of 20-30℃.
8. The hydrothermal synergistic reduction preparation method of a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst according to claim 1, characterized in that: The heating in the fourth step is a staged heating process. The first stage temperature is 75-85℃, and the temperature is maintained for 2.8-3.2 hours. The second stage temperature is 145-155℃, and the temperature is maintained for 2.8-3.2 hours.
9. The hydrothermal synergistic reduction preparation method of a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst according to claim 1, characterized in that: In the fifth step, the solvent for centrifugal washing is a mixture of ethanol and acetone, with a volume ratio of ethanol to acetone of 1:1, and the washing is performed 3-4 times with the ethanol and acetone mixture.
10. The hydrothermal synergistic reduction preparation method of a high ammonia oxidation activity PtMoNi medium entropy alloy catalyst according to claim 1, characterized in that: The high ammonia oxidation activity PtMoNi medium entropy alloy catalyst in the fifth step is Pt4Mo4Ni1 / C.