阅读说明：本技术 一种普适性制备负载型金属单原子/金属纳米颗粒的方法 (Method for universally preparing load type metal monoatomic/metal nanoparticles ) 是由 王双印 陶李 张娜娜 于 2019-10-28 设计创作，主要内容包括：本发明公开了一种具有普适性的快速制备载体负载金属单原子/金属纳米颗粒的方法,通过浸渍法在载体表面吸附金属盐溶液,通过冷冻干燥的方法得到均匀负载金属盐的粉末,再利用等离子体处理快速处理得到载体负载的金属纳米颗粒材料。该方法适用于不同的金属成分,不同的金属载体,可用于制备各种载体负载的金属单原子,单质金属颗粒,及多成分的合金纳米颗粒甚至五种金属元素以上的高熵合金。该方法合成的金属单原子,金属纳米颗粒分布均匀,负载量易调控,简单易行,成本低,无污染,具有广泛的应用潜力。整个制备过程未引入任何有机溶剂物质,不需要高温条件,反应时长短,反应效率高,成本低,能耗少,无废弃物产生,无污染,方法经济简单。(The invention discloses a universal method for rapidly preparing carrier-loaded metal monatomic/metal nanoparticles, which is characterized in that a metal salt solution is adsorbed on the surface of a carrier by an impregnation method, powder of uniform loaded metal salt is obtained by a freeze-drying method, and then the metal nanoparticle material loaded on the carrier is obtained by rapid treatment by using plasma. The method is suitable for different metal components and different metal carriers, and can be used for preparing metal single atoms and single-substance metal particles loaded by various carriers, multi-component alloy nano particles and even high-entropy alloys with more than five metal elements. The metal monoatomic and metal nano-particles synthesized by the method are uniformly distributed, the loading capacity is easy to regulate and control, the method is simple and easy to implement, the cost is low, no pollution is caused, and the method has wide application potential. The whole preparation process does not introduce any organic solvent substance, does not need high temperature condition, has short reaction time, high reaction efficiency, low cost, less energy consumption, no waste generation, no pollution and economic and simple method.)

1. A universal preparation method of supported metal monoatomic/metal nanoparticles is characterized by comprising the following steps:

(1) dispersing a required carrier in pure water, utilizing ultrasonic wave to crush cells to obtain a uniformly dispersed carrier solution, and continuously stirring to prevent the carrier in the carrier solution from coagulating;

(2) preparing a metal salt solution, and dropwise adding the metal salt solution into the carrier solution obtained in the step (1) according to the requirement of loading capacity for stirring;

(3) introducing the solution obtained after stirring in the step (2) into a surface dish for freezing and icing, and then performing freeze drying to obtain carrier precursor powder uniformly adsorbing metal salt;

(4) and (4) carrying out radio frequency plasma treatment on the carrier precursor powder obtained in the step (3) under a vacuum condition to obtain the loaded metal monoatomic/metal nanoparticle.

2. The method according to claim 1, wherein in the step (1), the carrier comprises any one or more of graphene, carbon nanotubes, ketjen black, alumina, molecular sieves, titanium oxide, cerium oxide, tungsten oxide, carbon paper, carbon cloth, carbon fibers and nickel foam.

3. The method according to claim 1, wherein in the step (1), the time for the ultrasonic cell pulverization is 0.1h-0.5 h.

4. The method according to claim 1, wherein in the step (2), the metal salt solution contains metal elements including any one or more of platinum, palladium, ruthenium, iridium, gold, silver, rhodium, iron, cobalt, nickel, copper, zinc, molybdenum, tungsten, titanium, tin, cerium and gallium.

5. The method according to claim 4, wherein in the step (2), the metal salt solution contains any five or more metal elements, and the final product is high-entropy alloy nanoparticles.

6. The method according to claim 1, wherein in the step (2), the metal salt solution is a water-soluble metal salt solution, and the metal salt solution contains metal ions at a concentration of 0.1 to 1 mol/L.

7. The method according to claim 1, wherein in the step (2), when the supported metal monoatomic atoms are prepared, the mass loading of the metal monoatomic atoms contained in the supported metal monoatomic atoms is 0.01% to 5%; when preparing the supported metal nanoparticles, the mass loading of the metal nanoparticles contained in the supported metal nanoparticles is 5-60%; the stirring time is 1-24 h.

8. The method according to claim 1, wherein in step (3), the freezing time is at least 10 min.

9. The method of claim 1, wherein in the step (4), the radio frequency power frequency used by the radio frequency plasma is 13.56MHz, the time of the radio frequency plasma treatment is 5min-1h, and the power of the radio frequency plasma treatment is 100W-1000W.

10. The method according to any one of claims 1 to 9, wherein in the step (4), the plasma treatment is performed in an atmosphere of a pressure lower than 300Pa, wherein the atmosphere is argon, nitrogen, ammonia, helium or sulfur hexafluoride.

Technical Field

The invention belongs to the technical field of metal loading, and particularly relates to a universal preparation method of loaded metal monoatomic/metal nanoparticles.

Background

With the development of material disciplines and nano characterization technologies, metal monatomic materials have attracted wide attention in recent years. Due to the unique characteristics of metal monoatomic atoms, compared with metal nanoparticles, the metal monoatomic atoms have unique physicochemical properties due to high surface energy, quantum size effect and strong carrier interaction. Since the work of the composition of the academician subject is to prepare Pt/FeOx platinum-based monatomic, the monatomic catalyst has been widely applied to the fields of thermal catalysis, electrocatalysis and the like, and the results show that the monatomic material shows excellent catalytic performance. Each metal atom of the monatomic catalyst can be used as a catalytic site, and the monatomic catalyst has the characteristics of single active site of a homogeneous catalyst and easy separation of a heterogeneous catalyst, and provides new power for scientific research and practical application due to extremely high atom utilization rate and single active site.

Due to the higher surface free energy of the monatomic material, metal atoms are easy to agglomerate and grow to form nano particles or nano clusters, so that the monatomic effect is lost and the monatomic material is inactivated. Therefore, the preparation of the monatomic catalyst is crucial to enhance the interaction between metal atoms and a carrier in the synthesis process and prevent the agglomeration growth of metal monatomic. The existing methods for preparing the monoatomic compound mainly comprise an impregnation method, coprecipitation, high-temperature calcination and the like. Taking a carbon-based carrier as an example, in the process of preparing a monatomic catalyst, a metal organic framework or an organic matter adsorbing metal salt is usually taken as a precursor, and the monatomic catalyst is obtained by high-temperature carbonization and then acid washing to remove metal particles. However, due to the influence of the process cost and the stability of the monoatomic atoms, how to prepare the monoatomic atoms simply and efficiently in a large scale at low cost still has great challenges.

Many catalytic reactions still require metal nanoparticles to achieve, as opposed to metal monoatomic atoms. Due to the unique physical and chemical properties of the metal nano-particle material, the metal nano-particle material has wide application in various fields, such as common electrocatalysts, and has application in various electrocatalytic reactions and electrodes of new energy devices. In addition, the catalyst has wide application in the aspects of industrial catalysis, automobile exhaust treatment and the like. The metal nanoparticles are usually supported on various carriers, such as carbon materials, oxides, molecular sieve carriers. On one hand, the nano particles are loaded on the carrier, so that the utilization of the nano particles is improved, such as the conductivity of the nano particles is improved, the dispersity of the particles is improved, and the particles are prevented from being agglomerated and grown; on the other hand, the specific carrier-loaded metal nanoparticles can optimize the electronic structure characteristics of the metal nanoparticles due to different work functions, so that the performance of the metal nanoparticles is further improved.

The conventional method for loading metal nanoparticles on a carrier mainly comprises the steps of carrying out high-temperature reaction in a solvent by using various surfactants or organic solvents through a solvothermal method, and then carrying out suction filtration and centrifugation through a large amount of organic solvents and water to obtain a product through fine washing. The method has the disadvantages of complicated process, high cost, low material yield, poor repeatability, toxic effect on performance caused by residual organic solvent on the surface, and incapability of obtaining some metal particles by a solvothermal method. The other method is to reduce the carrier and the metal salt precursor at high temperature in a fixed special atmosphere, but the high temperature can improve the entropy value of the material to promote the growth of the nano particles, and the problems of high cost and difficult control are also faced. In the reduction process of the supported metal nanoparticles, a reducing agent or a reducing gas is required to reduce the particles, and the violent reaction can cause the agglomeration of the metal particles and influence the catalytic performance of the metal particles. In addition, the conventional methods usually take a long time, generate a large amount of waste water and waste gas and consume high energy. Meanwhile, the traditional method has high limitation and no universality.

Disclosure of Invention

The technical problem to be solved by the present invention is to overcome the above mentioned disadvantages and drawbacks in the background art, and to provide a method for directly synthesizing various carrier-supported nano metal particle materials by adsorbing a metal salt precursor in an aqueous solution with a carrier, obtaining a powder precursor through freeze-drying, and then directly synthesizing various carrier-supported nano metal particle materials under a vacuum condition (the air pressure is lower than 300Pa) with plasma. The method is economical and simple, generates no waste, and is suitable for synthesis of multiple metal monoatomic carriers and multi-component metal nanoparticles.

In order to solve the technical problems, the technical scheme provided by the invention is as follows:

a universal preparation method of loaded metal monoatomic/metal nanoparticles comprises the following steps:

(1) dispersing a required carrier in pure water, utilizing ultrasonic wave to crush cells to obtain a uniformly dispersed carrier solution, and continuously stirring to prevent the carrier in the carrier solution from coagulating;

(2) preparing a metal salt solution, and dropwise adding the metal salt solution into the carrier solution obtained in the step (1) according to the requirement of loading capacity for stirring;

(3) pouring the solution obtained after stirring in the step (2) into a surface dish for freezing and icing, and then performing freeze drying to obtain carrier precursor powder uniformly adsorbing metal salt;

(4) and (4) carrying out plasma treatment on the carrier precursor powder obtained in the step (3) under a vacuum condition to obtain the loaded metal monoatomic/metal nano-particles.

When the supported metal monoatomic/metal nano-particle is prepared, no organic solvent substance is introduced, so that the cost is reduced, and the problems that the organic solvent substance pollutes materials and reduces the catalytic activity of the materials during catalytic reaction are solved.

The freeze-drying technology is used in the preparation of carrier precursor powder, which is beneficial to the dispersion of metal salt and carrier, and the obtained material is more suitable for plasma treatment, so that the size of the material-loaded particles is more uniform.

In the method, preferably, in the step (1), the carrier includes any one or more of graphene, carbon nanotubes, ketjen black, alumina, molecular sieve, titanium oxide, cerium oxide, tungsten oxide, carbon paper, carbon cloth, carbon fibers, and nickel foam.

Preferably, in the step (1), the time for ultrasonic cell pulverization is 0.1h-0.5 h.

Preferably, in the step (2), the metal element contained in the metal salt solution includes any one or more of platinum, palladium, ruthenium, iridium, gold, silver, rhodium, iron, cobalt, nickel, copper, zinc, molybdenum, tungsten, titanium, tin, cerium and gallium. More preferably, the metal salt solution contains any five or more metal elements, and the finally prepared product is the high-entropy alloy nano-particles.

Preferably, in the step (2), the metal salt solution is a water-soluble metal salt solution, more preferably a nitrate, a chloride, a sulfate or an organic metal salt, and may also be other water-soluble metal salts, so as to avoid introducing organic solvent substances; the concentration of metal ions contained in the metal salt solution is 0.1-1mol/L, too low concentration and too large water amount influence the drying time, and too large concentration and too small water amount cause inaccurate addition amount control.

Preferably, in the step (2), when the supported metal monoatomic atom is prepared, the mass loading of the metal monoatomic atom contained in the supported metal monoatomic atom is 0.01-5%; when preparing the supported metal nanoparticles, the mass loading of the metal nanoparticles contained in the supported metal nanoparticles is 5-60%; the stirring time is 1-24 h. The mass loading capacity calculation method comprises the following steps: metal mass/(metal mass + support mass).

Preferably, in the step (3), the freezing time is at least 10 min.

Preferably, in the step (4), the frequency of the radio frequency power supply used by the radio frequency plasma is 13.56MHz, the time of the radio frequency plasma treatment is 5min-1h, and the power of the radio frequency plasma treatment is 100W-1000W. The radio frequency plasma adopted by the invention is generated by exciting gas in the reactor to ionize under the vacuum condition by using a high-frequency radio frequency power supply (13.56MHz), in the material treatment process, the reaction gas can enter the reaction cavity through gas inlet control, and meanwhile, by-products in the reaction process are timely discharged under the vacuum condition, the by-products are prevented from generating and polluting samples, and the obtained products do not need subsequent treatment.

In the step (4), the plasma treatment is performed in an atmosphere of less than 300Pa, wherein the atmosphere is argon, nitrogen, ammonia, helium or sulfur hexafluoride. The plasma technology is used under the environment condition that the air pressure is lower than 300Pa, the reduction by-products can be effectively eliminated, and the material purity is improved.

Compared with the prior art, the invention has the beneficial effects that: the method can be suitable for different metal components and different metal carriers, can select different modified atmospheres according to requirements, can be used for preparing metal single atoms and single-substance metal particles loaded by various carriers, multi-component alloy nano particles and even more than five high-entropy alloys, and has the advantages of adjustable metal components, adjustable atmosphere, adjustable power, adjustable time and good universality; the metal monoatomic and metal nano-particles synthesized by the method are uniformly distributed, the dispersibility is good, the loading capacity is easy to regulate, no organic solvent substance is introduced in the whole preparation process, high-temperature conditions are not needed, the reaction time is short, the reaction efficiency is high, the cost is low, the energy consumption is low, no waste is generated, no pollution is caused, the method is economical and simple, and the method has wide application potential.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a transmission electron microscope photograph of a cobalt metal single atom loaded with Ketjen black obtained in example 1;

FIG. 2 is a transmission electron microscopy energy spectrum of a cobalt metal single atom loaded on Ketjen black obtained in example 1;

FIG. 3 is an X-ray diffraction pattern of a cobalt metal monoatomic atom supported by Ketjen black obtained in example 1;

fig. 4 is a transmission electron microscope picture of the graphene-supported platinum metal nanoparticles obtained in example 2;

FIG. 5 is a transmission electron microscope picture of the molecular sieve loaded with platinum metal nanoparticles obtained in example 3;

FIG. 6 is a transmission electron microscope spectrum of the carbon nanotube supported multi-alloy (Pt, Fe, Co, Ni, Cu) nanoparticles obtained in example 4;

FIG. 7 is an X-ray diffraction chart of Ketjen black-supported platinum metal nanoparticles obtained in example 5;

fig. 8 is an X-ray diffraction pattern of ketjen black-supporting multi-element alloy (platinum, iron, cobalt, nickel, copper) nanoparticles obtained in example 6.

Detailed Description

In order to facilitate understanding of the invention, the invention will be described more fully and in detail with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.