Preparation method of superfine PtIr nanowire catalyst for ammoxidation

Abstract

The invention discloses a preparation method of a superfine PtIr nanowire catalyst for ammoxidation. The preparation method comprises the following steps: firstly, fully dissolving platinum acetylacetonate, iridium acetylacetonate, tungsten hexacarbonyl and dodecyl trimethyl ammonium bromide in oleylamine to obtain a light yellow solution; carrying out ultrasonic treatment on the obtained light yellow solution until the solution is fully dissolved; and heating the obtained uniform light yellow solution to 190 DEG C in an oil bath, keeping the temperature for 5 hours, centrifuging, washing and drying to obtain the superfine PtIr nanowire catalyst. The nanowire structure has a high specific surface area and abundant active sites, and is beneficial to effective quality and electron transmission. Through alloying of Ir and Pt, the electronic structure on the surface of the catalyst is changed, and the poisoning probability is effectively reduced. Meanwhile, the adsorption and activation process of ammonia molecules is optimized through the synergistic effect between Pt and Ir, the reaction activation energy is reduced, and the reaction rate is remarkably increased. The catalyst not only has remarkable ammonia oxidation catalytic performance, but also is good in stability and simple in preparation process.

Description

Technical Field

[0001] This invention relates to a method for preparing an ultrafine PtIr nanowire catalyst for ammonia oxidation, belonging to the field of novel functional nanomaterials. Background Technology

[0002] Driven by the global goal of carbon neutrality, the need for a low-carbon transformation of the fossil energy system is becoming increasingly urgent. Ammonia, as a carbon-free, high-energy-density hydrogen carrier, is becoming increasingly prominent in the energy transition due to its advantages such as high safety and low storage and transportation costs. Among them, ammonia oxidation (AOR), as the core technology for ammonia energy utilization, can serve as an independent energy carrier and release hydrogen through cracking technology at the application end, making it an ideal medium for the safe, efficient storage, transportation, and large-scale application of hydrogen energy, providing key technological support for building a zero-carbon energy society. Among many AOR catalysts, Pt-based nanowire catalysts are considered to be highly promising. However, in the AOR reaction process, the adsorption of nitrogen-containing intermediates on the Pt surface leads to severe poisoning, which not only slows down the AOR kinetics but also causes rapid catalyst deactivation. Therefore, designing highly active, poison-resistant Pt-based nanowire catalysts has become the core to overcome the technological bottleneck.

[0003] Traditional Pt-based nanowire catalysts suffer from insufficient reaction sites, which severely hinders mass transfer and negatively impacts catalytic activity. Ultrafine Pt-based nanowire catalysts, however, possess the unique advantages of nanowire structures, including high-index crystal facet exposure, axial electron mobility 2-3 orders of magnitude higher than conventional nanowires, and abundant active sites, resulting in significantly enhanced catalytic activity. Furthermore, to reduce Pt electrode poisoning, Ir, a metal with high lattice compatibility with Pt, was successfully alloyed with it, altering the electronic structure of the catalyst surface, weakening the binding energy between nitrogen-containing intermediates and the catalyst surface, and improving the catalyst's resistance to poisoning. Therefore, a simple and efficient method is urgently needed to develop and design ultrafine PtIr nanowire catalysts to meet the practical application requirements of AOR reactions.

[0004] Currently, the preparation methods for ultrafine PtIr nanowire catalysts have significant shortcomings, hindering both practical applications and research progress. These methods are extremely complex, involving numerous precise steps and demanding high standards for reaction conditions, equipment, and operators, significantly increasing preparation costs. Therefore, developing innovative and simple preparation methods to produce ultrafine PtIr nanowire catalysts with highly efficient AOR catalytic performance is crucial for advancing this field and its practical applications. Summary of the Invention

[0005] To avoid the shortcomings of the prior art, the present invention provides a method for preparing an ultrafine PtIr nanowire catalyst.

[0006] One of the objectives of this invention is to provide a novel ultrafine PtIr nanowire catalyst.

[0007] The second objective of this invention is to provide a simple and easy-to-implement one-step reduction method.

[0008] The third objective of this invention is to provide a catalyst with significantly high AOR catalytic activity.

[0009] The ultrafine PtIr nanowire catalyst prepared by this invention is prepared by a one-step reduction method using platinum acetylacetonate, iridium acetylacetonate, tungsten hexacarbonyl, dodecyltrimethylammonium bromide, and oleylamine as raw materials. The preparation process includes the following specific steps: 1. First, mix 10-30 mg of platinum acetylacetone, 0-20 mg of iridium acetylacetone, 20-50 mg of tungsten hexacarbonyl, and 150-200 mg of dodecyltrimethylammonium bromide in 8-15 mL of oleylamine to obtain a light yellow solution. 2. Sonicate the light yellow solution obtained in step 1 for 1-2 hours until fully dissolved; 3. Place the uniform light yellow solution obtained in step 2 in an oil bath at 160-200 ℃ for 3-7 hours to obtain a black solution; 4. Centrifuge the black solution obtained in step 3 at 10,000 rpm for 5 minutes using a high-speed centrifuge. Remove the supernatant from the centrifuge tube and wash to obtain the black precipitate. 5. Place the black precipitate obtained in step 4 in an oven at 40-80 ℃ and dry it for 4-10 hours to obtain the ultrafine PtIr nanowire catalyst.

[0010] The beneficial effects of this invention are: 1. This invention provides a method for preparing ultrafine PtIr nanowire catalysts for ammonia oxidation, characterized by using platinum acetylacetonate, iridium acetylacetonate, tungsten hexacarbonyl, dodecyltrimethylammonium bromide and oleylamine as raw materials, and preparing them by a one-step reduction method, requiring only common laboratory equipment and no special equipment, and the process is simple and easy to operate. 2. This method provides a novel ultrafine PtIr nanowire catalyst, which is a highly efficient catalyst for ammonia oxidation reaction; 3. The ultrafine PtIr nanowire catalyst obtained by this method exhibits performance at 5 mV s. -1 Under CV testing, the peak current density was 17.8 mA cm⁻¹. -2 The performance and stability of AOR are significantly better than those of ultrafine Pt2Ir nanowire catalysts, ultrafine Pt nanowire catalysts and commercial Pt / C catalysts; 4. The pharmaceuticals used in this invention are all non-toxic and harmless, and the preparation is simple and quick. After preparation, no complicated and tedious steps are required, making it particularly suitable for batch preparation and industrial-scale production and commercial application. Attached Figure Description

[0011] 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.

[0012] Figure 1 Transmission electron microscope image of the ultrafine PtIr nanowire catalyst prepared in this invention.

[0013] Figure 2 High-angle annular dark-field transmission electron microscope image and corresponding elemental analysis image of the ultrafine PtIr nanowire catalyst prepared for this invention.

[0014] Figure 3 X-ray photoelectron spectroscopy of the ultrafine PtIr and Pt nanowire catalysts prepared in this invention.

[0015] Figure 4 The AOR performance test results are shown for the ultrafine PtIr, Pt2Ir, Pt nanowire catalysts and commercial Pt / C catalysts prepared in this invention.

[0016] Figure 5 Stability test results for the ultrafine PtIr, Pt2Ir, and Pt nanowire catalysts prepared in this invention and the commercial Pt / C catalyst. Detailed Implementation

[0017] 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.

[0018] 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.

[0019] Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0020] Example 1: First, 12 mg of platinum acetylacetone, 15 mg of iridium acetylacetone, 35 mg of tungsten hexacarbonyl, and 150 mg of dodecyltrimethylammonium bromide were mixed in 10 mL of oleylamine to obtain a light yellow solution. The obtained light yellow solution was ultrasonically treated for 1 hour until fully dissolved. The obtained uniform light yellow solution was placed in an oil bath and heated to 170 °C and maintained for 4 hours to obtain a black solution. The black solution was centrifuged and washed to obtain a black precipitate. The black precipitate was placed in an oven at 60 °C and dried for 10 hours to obtain an ultrafine PtIr nanowire catalyst.

[0021] Example 2: First, 24 mg of platinum acetylacetone, 15 mg of iridium acetylacetone, 39 mg of tungsten hexacarbonyl, and 150 mg of dodecyltrimethylammonium bromide were mixed in 10 mL of oleylamine to obtain a light yellow solution. The obtained light yellow solution was ultrasonically treated for 1 hour until fully dissolved. The obtained uniform light yellow solution was placed in an oil bath and heated to 170 °C and maintained for 4 hours to obtain a black solution. The black solution was centrifuged and washed to obtain a black precipitate. The black precipitate was placed in an oven at 60 °C and dried for 10 hours to obtain an ultrafine Pt2Ir nanowire catalyst.

[0022] Example 3: First, 20 mg of platinum acetylacetonate, 35 mg of tungsten hexacarbonyl, and 150 mg of dodecyltrimethylammonium bromide were mixed in 10 mL of oleylamine to obtain a light yellow solution. The obtained light yellow solution was ultrasonically treated for 1 hour until fully dissolved. The obtained uniform light yellow solution was placed in an oil bath and heated to 160-200 °C and maintained for 4 hours to obtain a black solution. The black solution was centrifuged and washed to obtain a black precipitate. The black precipitate was placed in a 60 °C oven and dried for 10 hours to obtain an ultrafine Pt nanowire catalyst.

[0023] Figure 1 Transmission electron microscopy (TEM) image of the ultrafine PtIr nanowire catalyst prepared in Example 1. From... Figure 1 It can be seen that the synthesized ultrafine PtIr nanowire catalyst has a uniform, extremely fine nanowire structure.

[0024] Figure 2 High-angle annular dark-field transmission electron microscope images and corresponding elemental analysis images of the ultrafine PtIr nanowire catalyst prepared in Example 1. Figure 2 It can be seen that Pt and Ir elements are uniformly distributed in the ultrafine PtIr nanowires.

[0025] Figure 3 X-ray photoelectron spectroscopy (XPS) spectra of the ultrafine PtIr and Pt nanowire catalysts prepared in Examples 1 and 3. Figure 3It can be seen that the Pt4f of the ultrafine PtIr nanowires 7 / 2 The peak binding energy is located at 71.1 eV, which is lower than the binding energy of Pt nanowires (71.4 eV). This phenomenon demonstrates the electron transfer process from Ir atoms to Pt atoms. The Pt electronic structure of ultrafine PtIr nanowires is expected to improve the electron transfer rate and enhance catalytic activity.

[0026] Figure 4 The AOR performance test graphs are for the ultrafine PtIr, Pt2Ir, and Pt nanowire catalysts prepared in Examples 1-3, and the commercial Pt / C catalyst. Figure 4 It can be seen that at 5 mV s -1 Under the test conditions, the peak current density of the ultrafine PtIr nanowire catalyst prepared in Example 1 was 17.6 mA cm⁻¹. -2 The AOR performance was significantly higher than that of the ultrafine Pt2Ir, Pt nanowire catalysts prepared in Examples 2 and 3 and the commercial Pt / C catalyst, indicating that the ultrafine PtIr nanowire catalyst prepared in Example 1 has excellent AOR performance.

[0027] Figure 5 The graphs show the stability test results of the ultrafine PtIr and Pt2Ir nanowire catalysts prepared in Examples 1-3 and the commercial Pt / C catalyst. Figure 5 It can be seen that, under a constant voltage test condition of 0.71 V, after 500 s, the current density of the ultrafine PtIr nanowire catalyst prepared in Example 1 is 0.87 mA cm⁻¹. -2 The stability of the ultrafine Pt₂Ir and Pt nanowire catalysts prepared in Examples 2 and 3 is higher than that of the commercial Pt / C catalysts prepared in Examples 2 and 3. This indicates that the ultrafine PtIr nanowire catalyst prepared in Example 1 has excellent stability.

[0028] Obviously, those skilled in the art can make various modifications and variations to the preparation method of the ultrafine PtIr nanowire 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 an ultrafine PtIr nanowire catalyst for ammonia oxidation, comprising the following steps: First, mix 10-30 mg of platinum acetylacetone, 10-20 mg of iridium acetylacetone, 20-50 mg of tungsten hexacarbonyl, and 150-200 mg of dodecyltrimethylammonium bromide in 8-15 mL of oleylamine to obtain a light yellow precursor solution; ultrasonically disperse the obtained light yellow precursor solution for 1-2 hours until fully dissolved; place the obtained uniform light yellow solution in an oil bath at 160-200 ℃ for 3-7 hours to obtain a black solution; The black solution was centrifuged and washed to obtain a black precipitate; the black precipitate was placed in a 60 ℃ oven and dried for 4-10 hours to obtain an ultrafine PtIr nanowire catalyst.

2. The method for preparing the ultrafine PtIr nanowire catalyst according to claim 1, characterized in that, The dosage of acetylacetone platinum is 12 mg, and the dosage of acetylacetone iridium is 15 mg.

3. The method for preparing the ultrafine PtIr nanowire catalyst according to claim 1, characterized in that, The amount of hexacarbonyl tungsten used is 35 mL, the amount of dodecyltrimethylammonium bromide used is 150 mg, and the amount of oleylamine used is 10 mL.

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