Nano-porous ternary intermetallic monatomic alloy catalyst for electrically synthesizing urea and preparation method of nano-porous ternary intermetallic monatomic alloy catalyst

Abstract

The invention discloses a nano-porous ternary intermetallic monatomic alloy catalyst for electrically synthesizing urea and a preparation method of the nano-porous ternary intermetallic monatomic alloy catalyst, and relates to the technical field of nano-materials. The prepared nano-porous ternary intermetallic monatomic alloy catalyst takes carbon dioxide as a carbon source and nitrate as a nitrogen source, and urea is synthesized through electrochemical reaction. The effect of high-selectivity and high-yield electro-catalytic synthesis of urea under mild conditions is achieved, and meanwhile the huge industrial application potential is shown. The preparation process of the nano-porous metal compound material is simple, efficient, low in cost, green and safe, large-scale and industrial production can be achieved, and meanwhile the nano-porous metal compound material is suitable for being popularized and applied to large-scale industrial electro-synthesis of urea.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterials, and particularly relates to a nanoporous ternary intermetallic single-atom alloy catalyst for electro-synthesizing urea and a preparation method thereof. Background Art

[0002] Urea is one of the most important nitrogen fertilizers, and the development of the urea industry is crucial for solving the global food crisis and meeting the needs of the growing population. At present, the industrial synthesis of urea relies on the Bosch-Meiser process, which involves the reaction of carbon dioxide and ammonia under extreme conditions (temperature: 150 - 200 °C; pressure: 150 - 250 bar). These processes are energy-intensive, consume a large amount of fossil energy, and emit a large amount of toxic and harmful gases, threatening the human living environment. Replacing the traditional process with an electrochemical process (electrocatalytic C-N coupling) driven by renewable electricity can achieve green and sustainable urea synthesis. Although many researchers have made great efforts in this field in recent years, the lack of efficient electrocatalysts remains the main obstacle restricting the development of this field. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a nanoporous intermetallic single-atom alloy catalyst for electro-synthesizing urea and a preparation method thereof.

[0004] In order to achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0005] A nanoporous ternary intermetallic single-atom alloy catalyst for electro-synthesizing urea and a preparation method thereof, characterized in that the preparation method of the catalyst is as follows:

[0006] S1. Select appropriate elements according to the target catalyst, and then select the required metal elements;

[0007] S2. Mix the metal elemental raw materials in a certain proportion, and then carry out vacuum high-frequency induction heating melting to prepare a precursor alloy ingot;

[0008] S3. Remelt the alloy ingot by using the melt spinning technology, and perform rapid quenching on the surface of a rapidly rotating copper roller to obtain a precursor alloy strip;

[0009] S4. Perform dealloying phase transformation treatment on the alloy strip obtained in S3 to obtain a nanoporous ternary intermetallic single-atom alloy catalyst; wherein, the dealloying treatment refers to chemical dealloying phase transformation or electrochemical dealloying phase transformation;

[0010] The nanoporous ternary intermetallic single-atom alloy catalyst according to claim 1 has a bicontinuous nanoporous structure; wherein, the ternary intermetallic single-atom alloy includes, but is not limited to, CuAuZn2 and CuPdZn2.

[0011] A nanoporous ternary intermetallic single-atom alloy catalyst for electro-synthesizing urea and a preparation method thereof, characterized in that the nanoporous intermetallic single-atom alloy is used as a catalyst, carbon dioxide is used as a carbon source, and nitrate is used as a nitrogen source.

[0012] The beneficial effects of the present invention are:

[0013] (1) The preparation process of the nanoporous metal compound material in the present invention is simple and efficient, low in cost, green and safe, and can achieve large-scale and industrial production.

[0014] (1) The present invention uses np / ISAA-CuAuZn2 and np / ISAA-CuPdZn2 catalysts to achieve efficient urea electro-synthesis in a three-electrode system.

[0015] (2) The present invention uses the np / ISAA-CuAuZn2 catalyst to achieve a urea Faraday efficiency of up to 85.5% and an energy conversion efficiency of 50.1% at a potential of 0 V vs. RHE in a three-electrode system.

[0016] (3) The present invention uses the np / ISAA-CuAuZn2 catalyst in a membrane electrode assembly electrolyzer, within a wide current density range (50 - 200 mA cm -2 ), the urea Faraday efficiency exceeds 50%, and the urea production rate is as high as 24.5 mg cm -2 h -1 (200 mAcm -2 ).

[0017] (4) The present invention uses the np / ISAA-CuAuZn2 catalyst in a membrane electrode assembly electrolyzer, and operates stably for 585 hours at 200 mA cm -2 , and the FE is stable at ~50%. The results of the present invention have good prospects in replacing the traditional urea synthesis industry and the field of green and efficient electro-synthesis of urea. Description of the Drawings

[0018] The present invention is further described with the accompanying drawings, but the embodiments in the drawings do not constitute any limitation to the present invention.

[0019] Figure 1 XRD patterns of np / ISAA-CuAuZn2 and np / ISAA-CuPdZn2 synthesized by the method of the present invention.

[0020] Figure 2 SEM image of np / ISAA-CuAuZn2.

[0021] Figure 3 SEM image of np / ISAA-CuPdZn2.

[0022] Figure 4 SEM-EDS image of np / ISAA-CuAuZn2 and np / ISAA-CuPdZn2.

[0023] Figure 5 Faraday efficiency and yield graphs for the electro-synthesis of urea using np / ISAA-CuAuZn2.

[0024] Figure 6 Electro-synthesis of urea performance graphs for np / ISAA-CuAuZn2 at different current densities.

[0025] Figure 7 Test results of the electro-synthesis of urea stability for the np / ISAA-CuAuZn2 catalyst.

[0026] Figure 8 Faraday efficiency and yield graphs for the electro-synthesis of urea using np / ISAA-CuPdZn2. Detailed implementation method

[0027] The following details the embodiments of the present invention. These embodiments are implemented on the premise of the technical solution of the present invention, and the detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0028] Embodiment 1

[0029] This example provides a preparation method for an np / ISAA-CuAuZn2 catalyst, including the following steps;

[0030] S1. Mix pure copper, pure gold, and pure zinc in a ratio of 7:7:86 by atomic percentage, and then perform arc melting to prepare a Cu7Au7Zn 84 alloy ingot.

[0031] S2. Remelt the alloy ingot using the melt spinning technique and perform rapid quenching on the surface of a rapidly rotating copper roller to obtain a Cu7Au7Zn 84 precursor alloy strip.

[0032] S3. Perform dealloying phase transformation treatment on the alloy strip obtained in S2 in a 1M acetic acid solution;

[0033] S4. Anneal the catalyst obtained in S3 in an atmosphere of H2 / Ar (with 10% H2) at 200°C for 2 hours to obtain the np / ISAA-CuAuZn2 catalyst;

[0034] Example 2

[0035] This example provides a preparation method of an np / ISAA-CuPdZn2 catalyst, including the following steps;

[0036] S1. Mix pure copper, pure palladium and pure zinc in a ratio of 7:7:86 by atomic percentage, and then carry out arc melting to prepare a Cu7Au7Zn 84 alloy ingot.

[0037] S2. Remelt the alloy ingot using the melt spinning technique and perform rapid quenching on the surface of a rapidly rotating copper roller to obtain a Cu7Au7Zn 84 precursor alloy strip.

[0038] S3. Perform dealloying phase transformation treatment on the alloy strip obtained in S2 in a 1M acetic acid solution to obtain the np / ISAA-CuPdZn2 catalyst;

[0039] Example 3

[0040] Electrocatalytic urea synthesis

[0041] The test uses a three-electrode system, with the nanoporous ternary intermetallic compound as the working electrode, a calibrated accurate Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode. The electrolytic cell uses an H-type electrolytic cell, and a mixed solution of 0.1mol / L potassium bicarbonate saturated with CO2 and 0.1mol / L potassium nitrate is used as the electrolyte.

[0042] Example 4

[0043] Electrocatalytic urea synthesis under membrane electrode assembly conditions

[0044] The test uses a two-electrode system. The experimental device consists of a customized membrane electrode electrolytic cell (1cm -2 ), a nanoporous ternary intermetallic single-atom alloy catalyst strip (cathode), a proton exchange membrane (Nafion117), and an IrO2-Ti mesh (cathode), and a mixed solution of 0.1mol / L potassium bicarbonate saturated with CO2 and 0.1mol / L potassium nitrate is used as the electrolyte.

[0045] The above description shows and describes several preferred embodiments of the invention. However, as mentioned above, it should be understood that the invention is not limited to the forms disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications, and environments, and can be changed within the scope of the inventive concept described herein through the above teachings or the technology or knowledge in the relevant field. And any changes and modifications made by those skilled in the art that do not depart from the spirit and scope of the invention shall fall within the protection scope of the appended claims of the invention.

Claims

1. A nanoporous ternary intermetallic single-atom alloy catalyst for electro-synthesizing urea and a preparation method thereof, characterized in that, The preparation method of the catalyst is as follows: S1. Select appropriate elements according to the target catalyst, and then select the required metal elements; S2. Mix the metal single-element raw materials in a certain proportion, and then carry out vacuum high-frequency induction heating and melting to prepare a precursor alloy ingot; S3. Remelt the precursor alloy ingot obtained in S2 by using the melt spinning technology, and rapidly quench on the surface of a high-speed rotating copper roller to obtain a precursor alloy strip; S4. Carry out dealloying phase transformation treatment on the alloy strip obtained in S3 to obtain a nanoporous ternary intermetallic single-atom alloy catalyst; wherein, the dealloying treatment refers to chemical dealloying phase transformation or electrochemical dealloying phase transformation.

2. The nano-porous ternary intermetallic single-atom alloy catalyst according to claim 1 has a bicontinuous nano-porous structure; wherein, The ternary intermetallic single-atom alloy includes but is not limited to CuAuZn2 and CuPdZn2.

3. A nanoporous ternary intermetallic single-atom alloy catalyst for electro-synthesizing urea and a preparation method thereof, characterized in that, Using the nanoporous intermetallic single-atom alloy as the catalyst, carbon dioxide as the carbon source, and nitrate as the nitrogen source.

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