Patent Application
20210146438
This invention relates to the field of preparation and modification of materials, in particular to a method for in-situ exsolution modification of a surface of a metal material to enhance the electrochemical performance of the metal material.
At present, noble metal catalysts have shown excellent electrochemical catalytic properties, but they are not suitable for large-scale applications due to cost problems. Traditional catalysts such as Fe, Co, Ni, Cu, etc. also have certain catalytic activities. Because of their large reserves and low cost, they are widely used in the catalytic industry. The catalyst industry is continuously evolving. Fuel cells, water electrolysis, organic catalysis and other technologies have increasing demands for catalyst activity. At the present stage, the use of a single, traditional catalyst can no longer meet the catalytic performance requirements in these technologies. It is thus necessary to modify materials to improve their performance. However, the modified particles prepared by conventional material modification methods such as electrodeposition, magnetron sputtering, and heteroatom substitution do not interact strongly with the base material. As a result, although the modified material has improved initial performance, its stability usually decreases. Some of the aforementioned modification methods are only suitable to carry out in the laboratory; they are not suitable for large-scale production. Therefore, there is an urgent need for a novel, stable metal surface modification method.
In-situ exsolution method is a new material modification method that is extremely stable and efficient. This method merely requires a small amount of noble metals to modify the traditional metal catalysts to improving the performance of these catalysts while maintaining their stability. Therefore, the in-situ exsolution method is anticipated to have a good application prospect in the field of material preparation and modification. At present, in China, there has been no report on metal surface modification by in-situ exsolution.
In view of the above, the objective of the present invention is to provide a method for in-situ exsolution modification of a surface of a metal material to enhance electrochemical performance. The method is aimed at the modification of traditional metal catalysts and can be applied to various fields of material processing and preparation. The modification can be accomplished through doping only a small amount of noble metals. The method is convenient to operate and is low in cost. It shows clear value in the laboratory and has good application prospects.
The design principle of the present invention is as follows: in-situ exsolution is a new method for material modification. It refers to the preparation of a metal material by mixing doped particles with a substrate under a non-equilibrium condition, followed by a change of conditions so that the metal material reaches equilibrium. Due to the different properties of the doped metal and the substrate, the doped phase is exsolved from the bulk phase to the surface to form a nano-island pinning structure. The exsolved nanoparticles are closely attached to the substrate and interact strongly with the substrate. As a result, the modified metal has a highly stable structure. Furthermore, the nanoparticle islands increase the surface roughness of the substrate and the specific surface area, thereby increases the number of catalytic active sites and the catalytic performance of the metal material.
Preferably, in step (1), the substrate metal is at least one selected from the group consisting of Mn, Fe, Co, Ni, Cu, and Zn.
Preferably, in step (1), the metal for modification is at least one selected from the group consisting of Mo, Ru, Rh, Pd, Ag, Ir, Pt, and Au.
Preferably, in step (1), a metal for modification in the raw material powder has a mass percentage of 0.1%-15%. When the amount is less than 0.1%, it is difficult to ensure the metal for modification will be exsolved out of the surface to achieve modification. When the amount is more than 15%, the cost will be high; furthermore, the particles are likely to accumulate at the surface, reducing modification quality.
Preferably, in step (2), the preparation method at the non-equilibrium condition is at least one selected from the group consisting of supersonic flame spraying, explosion spraying, atmospheric plasma spraying, supersonic plasma spraying, (ultra) low pressure plasma spraying, plasma spray—physical vapor deposition, electron beam deposition, cold spraying and laser 3D printing.
Preferably, in step (3), the heat treatment has a temperature of 500° C.-900° C., duration of the heat treatment is 1 hour-24 hours.
Preferably, in step (1), the mixing is mechanical mixing or spray granulation.
Preferably, in step (3), the heat treatment is under vacuum, in a protective atmosphere, or in a reducing atmosphere.
The present invention also provides a metal material prepared by the aforementioned modification method. The in-situ exsolution modified metal material of the present invention has a wide range of applications. It can be applied to improve the catalytic performance of metal catalysts in a number of aspects, including their hydrogen and oxygen evolution reactions, oxygen reduction reactions, hydrogen oxidation reactions, organic compound catalytic cracking reactions, and the like. The metal material has distinctive structural stability and high commercial value.
Preferably, a doped metal is pinned on the surface of the substrate metal; the doped metal has a nanostructure. The exsolved nanoparticles are closely attached to the substrate and interact strongly with the substrate. As a result, the modified metal has a highly stable structure. Furthermore, the nanoparticle islands increase the surface roughness of the substrate and the specific surface area, thereby increases the number of catalytic active sites and the catalytic performance of the metal material.
Compared with the prior art, the beneficial effects of the present invention are as follows:
(1) the modification method of the present invention is easy to perform: the modified metal catalyst can be obtained by doping and mixing only a small amount of metal for modification to prepare the raw material, followed by heat treatment.
(2) A wide range of preparation techniques can be used in the method of the present invention, including supersonic flame spraying, explosion spraying, atmospheric plasma spraying, supersonic plasma spraying, (ultra) low pressure plasma spraying, plasma spray—physical vapor deposition, electron beam deposition, cold spraying, laser 3D printing, etc. The method of the present invention is widely applicable.
(3) The in-situ exsolution modified metal material of the present invention has a wide range of applications. It can be applied to improve the catalytic performance of metal catalysts in a number of aspects, including their hydrogen and oxygen evolution reactions, oxygen reduction reactions, hydrogen oxidation reactions, organic compound catalytic cracking reactions, and the like. The metal material has distinctive structural stability and high commercial value.
In order to better illustrate the objective, technical solutions and advantages of the present invention, the present invention will be further described with reference to the drawings and embodiments.
As an embodiment of the metal material of the present invention, the metal material of this embodiment was prepared by the following method:
287.5 g Ni metal powder was weighed as a substrate metal powder, and 25 g Ag metal powder was weighed as a modification metal powder. The mass percentage of the modification metal powder was 8%. The powders weighed were transferred into a V-shaped mixer and mixed for 24 hours at a rotating speed of 10 r min−1. The fully mixed material will be used at a later stage as a raw material powder. A coated catalyst was prepared from the aforementioned raw material powder by an atmospheric plasma spraying equipment (APS). Under the protection of 20 ml min−1 of hydrogen, two batches of the coated catalyst prepared were heated to 800° C. and kept at this temperature for 4 hours and 8 hours respectively. After sintering was completed, a quartz tube was opened and samples were taken out; these samples are the metal materials modified by in-situ exsolution.
SEM tests were performed on surfaces of the original coated catalyst without heat treatment, the coated catalyst after the 4 h heat treatment and the coated catalyst after the 8 h heat treatment respectively. As shown in
As an embodiment of a metal material of the present invention, the metal material of this embodiment was prepared by the following method:
475 g Ni metal powder was weighed as substrate metal powders and 25 g Ag metal powder was weighed as a modification metal powder, and the mass percentage of the modification metal powder was 5%. The powders weighed were transferred into a ball milling tank and mixed with water, which acts as a dispersant, for 6 hours at a rotating speed of 400 r min−1 to allow thorough mixing. The mixture was then dried in an oven to produce a raw material powder for later use. A coated catalyst was prepared from the aforementioned raw material powders through adopting a cold spraying (CS) equipment. The coated catalyst prepared was sealed in a quartz tube, the quartz tube was vacuumized at room temperature and then refilled with 300 mbar argon. The sealed quartz tube was heated to 800° C. in a muffle furnace, followed by kept at this temperature for 4 hours and 8 hours respectively. After sintering was completed, the quartz tube was opened and samples were taken out; these samples are the metal materials modified by in-situ exsolution.
During the preparation process, SEM tests were performed on the surfaces of the original coated catalyst without heat treatment, the coated catalyst after the 4 h heat treatment and the coated catalyst after 8 h heat treatment respectively. As shown in
As an embodiment of a metal material of the present invention, the metal material of this embodiment was prepared by the following method:
499.5 g Fe metal powder was weighed as substrate metal powder and 0.5 g Au metal powder was weighed as modification metal powder, the percentage mass of modification metal powder was 0.1 mass %; the powder weighed was transferred into a ball milling tank and mixed with water, which acts as a dispersant, for 6 hours at a rotating speed of 400 r min−1 to allow thorough mixing. The mixture was then dried in an oven to produce a raw material powder for later use. A coated catalyst was prepared from the aforementioned raw material powders through adopting an atmospheric plasma spraying. The coated catalyst prepared was sealed in a quartz tube, the quartz tube was vacuumized at room temperature and then refilled with 300 mbar argon. The sealed quartz tube was heated to 500° C. in a muffle furnace, followed by kept at this temperature for 8 hours and 12 hours respectively. After sintering was completed, the quartz tube was opened and samples were taken out; these samples are the metal materials modified by in-situ exsolution.
The analysis of the surface morphology of the metal materials modified by in-situ exsolution prepared was the same as that of embodiment 1 and embodiment 2, and will not be repeated here.
According to an embodiment of a metal material of the present invention, the metal material in this embodiment was prepared by the following method:
425 g Co metal powder was weighed as substrate metal powder and 75 g Pt metal powder was weighed as modification metal powder, the percentage mass of modification metal powder was 15%; the powder weighed was transferred into a ball milling tank and mixed with water, which acts as a dispersant, for 6 hours at a rotating speed of 400 r min−1 to allow thorough mixing. The mixture was then dried in an oven to produce a raw material powder for later use. A coated catalyst was prepared from the aforementioned raw material powders by electron beam deposition; the coated catalyst prepared was sealed in a quartz tube, the quartz tube was vacuumized at room temperature and then refilled 300 mbar argon. The sealed quartz tube was heated to 900° C. in a muffle furnace, followed by kept at this temperature for 4 hours and 8 hours respectively. After sintering was completed, the quartz tube was opened and samples were taken out; these samples are the metal materials modified by in-situ exsolution.
The analysis of the surface morphology of the metal materials modified by in-situ exsolution prepared was the same as that of embodiment 1 and embodiment 2, and will not be repeated here.
It should be finally noted that the aforementioned embodiments merely illustrate the technical solutions of the present invention. They are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201910519553.0 | Jun 2019 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2020/080643 | 3/23/2020 | WO | 00 |
