A method for the preparation of a pt octahedral catalyst for the oxidation of ammonia modified with fluorine

Abstract

The application discloses a preparation method of a fluorine-modified Pt octahedral catalyst for ammonia oxidation, and the preparation method comprises the following steps: dissolving Pt(acac)2 in a mixed solution of dibenzyl ether and oleylamine to obtain a transparent light-yellow precursor solution, and preparing a chloroform injection solution of carbonyl manganese; placing the obtained precursor solution into an oil bath, rapidly injecting the prepared injection solution into the oil bath, and obtaining a black liquid through reaction; and placing the obtained black solid liquid and NH4F in a glass bottle, and obtaining the fluorine-modified Pt octahedral catalyst after heating. The fluorine-modified Pt octahedral catalyst for ammonia oxidation is synthesized through a simple high-temperature injection method and a solvent thermal method. The fluorine-modified Pt octahedral catalyst has the advantages of significant ammonia oxidation catalytic performance, good stability, rich raw materials, small amount of use, low energy consumption, high yield, and can realize low-cost large-scale production and preparation.

Description

Technical Field

[0001] This invention belongs to the field of novel functional nanomaterial preparation technology, specifically relating to a method for preparing a Pt octahedral catalyst for ammonia oxidative fluorine modification. Background Technology

[0002] In the process of large-scale implementation of the hydrogen energy industry, the high cost of hydrogen storage and transportation, and the difficulty of safety management, are hindering the widespread promotion of the hydrogen economy. Finding high-energy-density chemical hydrogen storage carriers has become a research hotspot in the energy field. Ammonia, relying on its mature and well-established industrial production, pipeline, and storage tank transportation system, and possessing the core advantages of ultra-high volumetric hydrogen storage density and zero carbon emissions across the entire chain, is gradually becoming an ideal alternative fuel to support the global low-carbon energy transition. Electrocatalytic ammonia oxidation (AOR) is the core reaction for achieving efficient electrochemical utilization of ammonia energy. It can be applied to direct ammonia fuel cells to convert chemical energy into electrical energy, and can also be used to achieve the resource recycling of ammonia, possessing extremely high scientific research value and industrialization prospects. Currently, platinum-based catalysts, due to their excellent intrinsic electrochemical activity, remain the mainstream catalytic materials with the best electrocatalytic ammonia oxidation performance in alkaline systems. However, during the catalytic reaction, the adsorbed nitrogen intermediates generated by the gradual dehydrogenation of ammonia are easily strongly chemisorbed on the surface of the platinum catalyst, permanently occupying the catalytic active sites, inducing irreversible catalyst poisoning, causing rapid decay of catalytic current and a significant decrease in long-term stability. Therefore, there is an urgent need to design atomic-level surface modification strategies to precisely optimize nitrogen-containing intermediates (N) by controlling the surface electronic structure of platinum-based materials. ads The adsorption strength of the platinum-based catalyst is optimized to maximize the retention of its excellent electrocatalytic ammonia oxidation activity while suppressing catalyst poisoning and deactivation.

[0003] Heteroatom modification is a common strategy for controlling the electronic structure of catalysts. However, heteroatoms such as N and S are easily lost in the alkaline AOR oxidation environment, leading to surface reconstruction and active site collapse, which is difficult to meet the requirements of long-term stability in industrial applications. In contrast, fluorine has high electronegativity, which can effectively enhance metal-ligand interactions, stabilize surface structures, and is not easily lost in oxidizing environments, making it an ideal modifying element for controlling the electronic structure of catalysts. Furthermore, fluorine atom modification can precisely control the electronic structure of Pt nano-octahedral surfaces and weaken the intermediate N in the AOR process. adsStrong adsorption at Pt active sites alleviates catalyst poisoning and deactivation. However, achieving stable regulation of the Pt surface electronic structure under strongly alkaline AOR conditions, while balancing high activity and long-term stability, remains a key scientific challenge in the design of Pt-based catalysts. Based on this, this study designed and prepared fluorine-modified Pt nano-octahedral catalysts, utilizing the electronegative electronic regulation effect induced by fluorine to optimize surface electron density and enhance AOR catalytic activity and stability. Therefore, developing a simple and controllable synthetic strategy to create fluorine-modified Pt octahedral catalysts with both high activity and high stability is of great significance for overcoming the Pt-based catalyst poisoning problem and promoting the development of ammonia oxidation electrocatalysis. Summary of the Invention

[0004] To avoid the shortcomings of the prior art, the present invention provides a method for preparing a Pt octahedral catalyst for ammonia oxidative fluorine modification.

[0005] One of the objectives of this invention is to provide a simple and easy-to-implement method for solvothermal doping of fluorine atoms.

[0006] The second objective of this invention is to provide a Pt octahedral catalyst for ammonia-fluorine oxidative modification.

[0007] The Pt octahedral catalyst for ammonia oxidative fluorine modification prepared in this invention is made from platinum acetylacetonate (Pt(acac)2), dibenzyl ether, oleylamine, manganese carbonyl, chloroform, and ammonium fluoride (NH4F) as raw materials via a high-temperature hot-injection method and a solvothermal method. The preparation process includes the following specific steps: 1. Dissolve 0.04-0.12 g Pt(acac)2 in a mixed solution of 5-15 mL dibenzyl ether and 3-9 mL oleylamine to obtain a transparent light yellow precursor solution, and prepare an injection solution of 0.04-0.12 g manganese carbonyl dissolved in 0.5-1.5 mL chloroform; 2. Place the precursor solution obtained in step 1 into an oil bath at 180-220 ℃, and quickly inject the prepared injection solution into it. React for 15-45 min to obtain a black liquid. 3. Place the black solid-liquid obtained in step 2 and 0.3-0.9 g of NH4F in a glass bottle, and heat at 30-60 °C for 2-4 h to obtain a fluorine-modified Pt octahedral catalyst.

[0008] The beneficial effects of this invention are: 1. This invention provides a method for preparing a Pt octahedral catalyst for ammonia oxidation with fluorine modification, namely, preparing a dispersed fluorine-modified Pt octahedral catalyst via a stepwise solvothermal method. The preparation method is simple and easy to operate, requires no special equipment, and eliminates the need for complex and cumbersome steps after preparation. It is particularly suitable for batch preparation and industrial-scale production and commercial applications. 2. The product prepared by this invention is a dispersed fluorine-modified Pt octahedral catalyst with uniform morphology and size, which can be prepared on a large scale and is easy to use. 3. The fluorine-modified Pt octahedral catalyst prepared in this invention exhibits performance at 10 mV s⁻¹. -1 At the scan rate, the peak current density is 20.89 mA cm⁻¹. -2 Its catalytic performance and stability are significantly better than those of commercial Pt / C catalysts, exhibiting excellent ammonia oxidation catalytic performance and good stability; 4. The preparation of this invention only requires common laboratory equipment and does not require special equipment. The process is simple and easy to carry out. Attached Figure Description

[0009] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings will be briefly introduced in the description of the embodiments or the prior art below. However, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 Transmission electron microscopy (TEM) image of the fluorine-modified Pt octahedral catalyst prepared in this invention.

[0011] Figure 2 The image shows the X-ray diffraction pattern of the fluorine-modified Pt octahedral catalyst prepared in this invention.

[0012] Figure 3 The X-ray photoelectron spectra of the fluorine-modified Pt octahedral catalysts Pt4f and F1s prepared in this invention are shown.

[0013] Figure 4 The graphs show the ammonia oxidation performance of the fluorine-modified Pt octahedral catalyst prepared in this invention and the commercial Pt / C catalyst.

[0014] Figure 5 This is a stability test diagram of the fluorine-modified Pt octahedral catalyst prepared in this invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0016] 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.

[0017] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0018] Example 1: 0.08 g of Pt(acac)₂ was dissolved in a mixed solution of 10 mL of dibenzyl ether and 6 mL of oleylamine to obtain a transparent, light yellow precursor solution. 0.08 g of manganese carbonyl was dissolved in 1 mL of chloroform for injection. The obtained precursor solution was placed in an oil bath at 200 °C, and the prepared injection solution was rapidly injected into it. After reacting for 30 min, a black liquid was obtained. The obtained black solid liquid was placed in a glass bottle with 0.6 g of NH₄F and heated at 45 °C for 3 h to obtain a fluorine-modified Pt octahedral catalyst.

[0019] Example 2: 0.04 g Pt(acac)2 was dissolved in a mixed solution of 15 mL dibenzyl ether and 3 mL oleylamine to obtain a transparent, light yellow precursor solution. 0.12 g manganese carbonyl was dissolved in 0.5 mL chloroform for injection. The obtained precursor solution was placed in an oil bath at 180 °C, and the prepared injection solution was rapidly injected into it. After reacting for 45 min, a black liquid was obtained. The obtained black solid liquid was placed in a glass bottle with 0.9 g NH4F and heated at 30 °C for 4 h to obtain a fluorine-modified Pt octahedral catalyst.

[0020] Example 3: 0.12 g Pt(acac)2 was dissolved in a mixed solution of 5 mL dibenzyl ether and 9 mL oleylamine to obtain a transparent, light yellow precursor solution. 0.04 g manganese carbonyl was dissolved in 1.5 mL chloroform for injection. The obtained precursor solution was placed in an oil bath at 220 °C, and the prepared injection solution was rapidly injected into it. After reacting for 15 min, a black liquid was obtained. The obtained black solid liquid was placed in a glass bottle with 0.3 g NH4F and heated at 60 °C for 2 h to obtain a fluorine-modified Pt octahedral catalyst.

[0021] Figure 1 This is a transmission electron microscope (TEM) image of the fluorine-modified Pt octahedral catalyst prepared in Example 1. From... Figure 1 It can be seen that the synthesized fluorine-modified Pt octahedral catalysts are uniform in size, with an average size of about 5-10 nm, and are evenly dispersed.

[0022] Figure 2 The image shows the X-ray diffraction pattern of the fluorine-modified Pt octahedral catalyst prepared in Example 1. Figure 2 It can be seen that the diffraction peaks of the fluorine-modified Pt octahedral catalyst correspond to the diffraction peaks of the metallic element Pt, and the strongest diffraction peak corresponds to the Pt (111) crystal plane.

[0023] Figure 3 (ab) are the X-ray photoelectron spectra of the fluorine-modified Pt octahedral catalysts Pt4f and F1s prepared in Example 1, respectively. Figure 3 It can be seen that the fluorine-modified Pt octahedral catalyst mainly exists in the form of Pt and F, with only a small portion of Pt inevitably being oxidized.

[0024] Figure 4 The graphs show the ammonia oxidation performance of the fluorine-modified Pt octahedral catalysts prepared in Examples 1-3 and the commercial Pt / C catalysts. Figure 4 It can be seen that at 10 mV s -1 Under the test conditions, the peak current density of the fluorine-modified Pt octahedral catalyst prepared in Example 1 was 20.89 mA cm⁻¹. -2 The performance was significantly higher than that of the Pt octahedral catalysts prepared in Examples 2 and 3 and the commercial Pt / C catalyst, indicating that the fluorine-modified Pt octahedral catalyst prepared in Example 1 has excellent ammonia oxidation performance.

[0025] Figure 5 This is a stability test graph of the fluorine-modified Pt octahedral catalyst prepared in Example 1. From... Figure 5 As can be seen, after a long-term test of 24 hours, the current density remained basically stable, only decreasing to 89.88%. This indicates that the fluorine-modified Pt octahedral catalyst prepared in Example 1 has excellent stability.

[0026] Obviously, those skilled in the art can make various modifications and variations to the method for preparing a fluorine-modified Pt octahedral catalyst described in this invention without departing from the spirit and scope of this invention. Therefore, if these modifications and variations of this invention fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a Pt octahedral catalyst for ammonia-fluorine oxidative modification, comprising the following steps: 0.08 g Pt(acac)2 was dissolved in a mixed solution of 10 mL dibenzyl ether and 6 mL oleylamine to obtain a transparent light yellow precursor solution. 0.08 g manganese carbonyl was dissolved in 1 mL chloroform for injection. The obtained precursor solution was placed in an oil bath at 200 °C, and the prepared injection solution was rapidly injected into it. After reacting for 30 min, a black liquid was obtained. The obtained black solid liquid was placed in a glass bottle with 0.6 g NH4F and heated at 45 °C for 3 h to obtain a fluorine-modified Pt octahedral catalyst.

2. The method for preparing the fluorine-modified Pt octahedral catalyst according to claim 1, characterized in that, The amount of Pt(acac)2 used is 0.08 g, the amount of carbonyl manganese used is 0.08 g, and the amount of NH4F used is 0.6 g.

3. The method for preparing the fluorine-modified Pt octahedral catalyst according to claim 1, characterized in that, The dosage of dibenzyl ether is 10 mL, the dosage of oleylamine is 6 mL, and the dosage of chloroform is 1 mL.

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