CN113782755A

CN113782755A - Bifunctional catalyst, preparation method thereof and metal-air battery

Info

Publication number: CN113782755A
Application number: CN202110939462.XA
Authority: CN
Inventors: 邱华军; 金泽宇; 林熹; 陈祖煌; 胡凯龙; 谢国强; 刘兴军
Original assignee: Shenzhen Graduate School Harbin Institute of Technology
Current assignee: Shenzhen Graduate School Harbin Institute of Technology
Priority date: 2021-08-16
Filing date: 2021-08-16
Publication date: 2021-12-10
Anticipated expiration: 2041-08-16
Also published as: CN113782755B

Abstract

The invention relates to the technical field of material preparation, and particularly discloses a bifunctional catalyst, a preparation method thereof and a metal-air battery. The preparation method of the bifunctional catalyst comprises the following steps of S1: smelting a plurality of metal materials in proportion to obtain an alloy body, wherein the plurality of metal materials comprise aluminum, cobalt, iron, X1 and X2, wherein the X1 is selected from any two or three of chromium, nickel and molybdenum, and the X2 is selected from one or more of platinum, palladium, gold, silver and copper; s2: rapidly cooling the alloy body; s3: and (3) placing the rapidly cooled alloy body in an alkaline solution for dealloying treatment to obtain the bifunctional catalyst.

Description

Bifunctional catalyst, preparation method thereof and metal-air battery

Technical Field

The invention relates to the technical field of material preparation, in particular to a bifunctional catalyst, a preparation method thereof and a metal-air battery containing the bifunctional catalyst.

Background

Metal-air batteries are widely studied and used because of their advantages such as high specific energy and stable performance. The design and fabrication of bifunctional electrocatalysts for Oxygen Reduction Reaction (ORR) and Oxygen Evolution Reaction (OER) are critical to the realization of high performance rechargeable metal-air batteries. Precious metals are often used as bifunctional electrocatalysts for metal-air batteries due to their good catalytic properties, e.g. Pt and ir (ru) based materials are the most efficient catalysts for oxygen reduction and oxygen evolution reactions, respectively, at present. However, the existing commonly used catalyst containing noble metal has high noble metal content, relatively expensive cost and poor catalytic cycle stability, and becomes a problem to be solved urgently in scientific research.

Disclosure of Invention

In view of the above, the present invention aims to provide a bifunctional catalyst which can solve the above problems or at least alleviate the above problems to some extent, a method for preparing the same, and a metal-air battery comprising the bifunctional catalyst.

To this end, in one aspect, the present invention provides a method for preparing a bifunctional catalyst, the method comprising the steps of: s1: smelting a plurality of metal materials in proportion to obtain an alloy body, wherein the plurality of metal materials comprise aluminum, cobalt, iron, X1 and X2, wherein the X1 is selected from any two or three of chromium, nickel and molybdenum, and the X2 is selected from one or more of platinum, palladium, gold, silver and copper; s2: rapidly cooling the alloy body; s3: and (3) placing the rapidly cooled alloy body in an alkaline solution for dealloying treatment to obtain the bifunctional catalyst.

Preferably, in step S1, the atomic number ratio of the aluminum, the cobalt, the iron, X1 and X2 is 95.8-95.9: 1:1:2: 0.1-0.2.

Preferably, in step S1, the plurality of metal materials are aluminum, cobalt, iron, molybdenum, chromium, and platinum in an atomic number ratio of 95.9:1:1:1:1: 0.1.

Preferably, in step S1, the plurality of metal materials are melted into a uniform alloy body in an arc melting furnace under an argon gas protection environment a plurality of times.

Preferably, in step S2, the alloy body is rapidly cooled by forming an alloy strip by a strip casting machine.

Preferably, in step S2, the tangential speed of the copper wheel of the belt slinger is 40-45 m/S.

Preferably, in step S2, the width of the alloy strip is 2-5mm, and the thickness is 15-25 um.

Preferably, in step S3, the alloy body is washed and dried after being dealloyed in 0.5-1.0 mol/L sodium hydroxide solution for 8-12 hours to obtain the bifunctional catalyst.

In another aspect, the present invention also provides a bifunctional catalyst, which is prepared according to the aforementioned method.

In yet another aspect, the present invention also provides a metal-air battery comprising a cathode, an anode, and an electrolyte, wherein the cathode comprises the aforementioned bifunctional catalyst.

The method for preparing the bifunctional catalyst is simple, a highly controllable top-down synthesis method is developed by combining the traditional metallurgy, rapid cooling and dealloying, the overall synthesis idea is ingenious, and the requirements on high-precision control of the technological process and high technical level of operators are reduced. In addition, the preparation method of the bifunctional catalyst provided by the invention introduces non-noble metal materials, greatly reduces the use of noble metals, reduces the expenditure of material cost, has adjustability and expandability, and is more suitable for large-scale production and popularization. The bifunctional catalyst prepared by the preparation method is a high-entropy alloy oxide loaded with noble metal nanoclusters, has a uniformly distributed nano-pore structure, comprises a nano-pore channel and a thin wall with a nano-pore structure, effectively exposes OER active sites, and is beneficial to improving performances in aspects of electrochemical catalysis, electrochemical durability and the like.

Drawings

Fig. 1 is a flow chart of a process for preparing a bifunctional catalyst (i.e., a high-entropy alloy oxide supporting noble metal Pt clusters) according to a first embodiment of the present invention.

Fig. 2 is an X-ray diffraction (XRD) image of a precursor alloy of a high-entropy alloy oxide supporting noble metal Pt clusters.

Fig. 3 is an X-ray diffraction (XRD) image of a high-entropy alloy oxide supporting noble metal Pt clusters.

Fig. 4 is a Scanning Electron Microscope (SEM) image of a high entropy alloy oxide supporting noble metal Pt clusters.

Fig. 5 is a scanning electron microscope-energy spectrometer (SEM-EDS) image of a high-entropy alloy oxide supporting noble metal Pt clusters.

Fig. 6 is a specific surface area (BET) test result of the high-entropy alloy oxide supporting the noble metal Pt cluster.

Fig. 7 is a scanning Transmission Electron Microscope (TEM) image of a high entropy alloy oxide supporting noble metal Pt clusters.

Fig. 8 is a scanning transmission electron microscope-energy spectrometer (STEM-EDS) image of a high entropy alloy oxide supporting noble metal Pt clusters.

Fig. 9 is a Linear Sweep Voltammetry (LSV) plot of Oxygen Evolution Reaction (OER) for high entropy alloy oxides supporting noble metal Pt clusters.

Fig. 10 is a graph of stability of Oxygen Evolution Reaction (OER) versus Linear Sweep Voltammetry (LSV) for high entropy alloy oxides supporting noble metal Pt clusters.

Fig. 11 is a Linear Sweep Voltammetry (LSV) plot of Oxygen Reduction Reaction (ORR) of high entropy alloy oxide supporting noble metal Pt clusters.

Fig. 12 is a graph of stability of Oxygen Reduction Reaction (ORR) versus Linear Sweep Voltammetry (LSV) for high entropy alloy oxides supporting noble metal Pt clusters.

Detailed Description

The invention will be described in detail with reference to the accompanying drawings and specific embodiments, so that the technical scheme and the beneficial effects of the invention are more clear. It is to be understood that the drawings are provided for purposes of illustration and description only and are not intended as a definition of the limits of the invention, but are drawn to scale.

Example 1

Referring to fig. 1, a first embodiment of the present invention provides a method for preparing a bifunctional catalyst, comprising the steps of:

s1: smelting a plurality of metal materials in proportion to obtain a homogeneous alloy body, wherein the plurality of metal materials comprise aluminum, cobalt, iron, X1 and X2, wherein the X1 is selected from any two or three of chromium, nickel and molybdenum, and the X2 is selected from one or more of platinum, palladium, gold, silver and copper; preferably, the atomic number ratio of the aluminum to the cobalt to the iron to the X1 to the X2 is

95.8-95.9: 1:1:2: 0.1-0.2; most preferably, the X1 is chromium and molybdenum;

s2: rapidly cooling the alloy body;

s3: and (3) placing the rapidly cooled alloy body in an alkaline solution for dealloying treatment to obtain the bifunctional catalyst.

In this embodiment, in step S1, the plurality of metal materials to be melted are aluminum, cobalt, iron, molybdenum, chromium, and platinum metal particles having an atomic number ratio of 95.9:1:1:1: 0.1, and the purity of each metal particle is preferably 99.99 wt% higher. Specifically, the metal particles are subjected to multiple turn-over melting in an arc melting furnace under an argon gas protection environment to obtain uniform alloy blocks or alloy balls, and the alloy blocks are taken as an example in the embodiment for explanation.

In this embodiment, in step S2, the homogeneous alloy ingot is melted and spun by a tape-spinning machine to be rapidly cooled, wherein the heating current of the tape-spinning machine is about 300A, and the tangential velocity of the copper wheel is about 40 to 45m/S, preferably 40m/S or 45 m/S. The width of an alloy strip prepared by the alloy block through a melt spinning machine is 2-5mm, and the thickness of the alloy strip is 15-25 um, for example, about 20 um.

In this embodiment, in step S3, the obtained alloy strip is subjected to dealloying treatment in a sodium hydroxide solution of 0.5 to 1.0mol/L, for example, 0.5mol/L, for 8 to 12 hours, for example, about 12 hours, and then is cleaned and dried, so as to obtain a high-entropy alloy oxide (HEO) loaded with noble metal nanoclusters.

The characterization of the materials and the electrochemical test results of the present example will be described below.

FIG. 2 shows the operation in step S2X-ray diffraction (XRD) pattern of the resulting alloy strip (i.e. the precursor alloy). It can be seen from fig. 2 that the alloy strip produced is predominantly pure aluminum due to the high aluminum content used, whereas the doped Pt is predominantly bound to Al₃(CoFeCrMo) phase.

Fig. 3 is an X-ray diffraction (XRD) pattern of the high-entropy alloy oxide supporting noble metal Pt clusters after the alloy strip obtained in the foregoing step S3 is dealloyed. As can be seen from FIG. 3, the pure aluminum phase has been substantially completely removed, while the broader XRD peaks newly formed at 35.7 degrees and 62.4 degrees are mainly due to spinel high entropy oxide (AlCoFeMoCr)₃O₄Is present. No Pt diffraction peak of face-centered cubic structure was observed, indicating that ultra-small Pt clusters may be formed.

In addition, from the XRD results, it can be seen that the addition of a small amount of Pt does not affect the phase structure of the precursor alloy and the spinel high-entropy oxide formed after dealloying.

Fig. 4 is a Scanning Electron Microscope (SEM) image of the high-entropy alloy oxide supporting noble metal Pt clusters after the dealloying of the alloy strip obtained in the foregoing step S3. Fig. 5 is a scanning electron microscope-energy spectrometer (SEM-EDS) image of the high-entropy alloy oxide supporting noble metal Pt clusters after dealloying of the alloy strip produced in the foregoing step S3, which further confirms that most of the aluminum was selectively removed.

The obtained high-entropy oxide has a nano-porous structure, and comprises primary holes and secondary holes, wherein the pore size of the primary holes is about 200-300nm, the pore size of the secondary holes is within about 10nm, part of the holes are formed due to the removal of pure aluminum phase, and the holes in the thin wall are due to Al₃The formation of the (CoFeCrMo) phase effectively exposes the OER active sites. Furthermore, this material had an extraordinary specific surface area, as shown in fig. 6, which is the result of the specific surface area (BET) test of the high-entropy alloy oxide supporting noble metal Pt clusters after dealloying of the alloy strip produced in the aforementioned step S3, which was shown to be as high as 243m²Specific surface area in g. In addition, the ultra small spherical Pt clusters having a narrow size distribution are uniformly distributed on the HEO scaffold as shown in fig. 7, which is the complex prepared in the foregoing step S3Scanning Transmission Electron Microscope (TEM) images of high entropy alloy oxides loaded with noble metal Pt clusters after dealloying of gold strips further confirm that bright Pt nanoclusters with narrow size distribution are uniformly decorated on the HEO scaffold. Fig. 8 is a scanning transmission electron microscope-energy spectrometer (STEM-EDS) image of the high-entropy alloy oxide loaded with noble metal Pt clusters after dealloying of the alloy strip prepared in the aforementioned step S3, which shows that the five active components AlCoFeMoCr and noble metal Pt are uniformly distributed in the nanoporous AlCoFeMoCr/Pt composite.

During the dealloying process, the phase separation and synthesis of the spinel high entropy oxide/Pt composite is due to metallic differences of the elements in the precursor. When aluminum is etched in an alkaline sodium hydroxide solution, high-activity transition metals Co, Fe, Cr and Mo are naturally oxidized to be in an oxidation state to form a mixed high-entropy oxide, and a noble metal Pt keeps the metal state, so that the high-entropy oxide/metal composite material is formed.

In order to obtain high OER activity, the present inventors also investigated the OER activity of each spinel oxide without supporting Pt. Research shows that the quaternary spinel oxide of AlCoFeNi formed by adding Ni has higher OER activity than the ternary spinel oxide of AlCoFe, and the high-entropy oxide (the alloy material with five or more elements forming a solid solution structure according to an equimolar ratio or a nearly equimolar ratio) can be formed by further adding a fifth element. However, the addition of the fifth element, Mn, to form the AlCoFeNiMn spinel oxide, rather reduces the OER activity, and then the addition of the fifth element, Cr or Mo, to form the five-membered high-entropy oxide, significantly improves the OER activity. By screening different element combinations, the inventor finds that the OER activity of the high-entropy oxide of AlCoFeMoCr is the highest, and the Tafel slope is as low as 52.4 mV/dec.

It is well known that Pt is an ORR catalyst and is not active for catalyzing OER. However, the inventor finds that after Pt is modified to form the HEO/Pt composite material, the OER activity is slightly enhanced, and the Tafel slope is also obviously reduced, which indicates that the OER activity of the HEO carrier is improved to some extent by adding the Pt cluster. Drawing (A)And 9 is a Linear Sweep Voltammetry (LSV) graph of Oxygen Evolution Reaction (OER) of the high-entropy alloy oxide supporting the noble metal Pt clusters after the dealloying of the alloy strip prepared in the step S3. As can be seen from the figure, the AlCoFeMoCr/Pt catalyst of the present example is more specific than the conventional IrO₂The OER activity of (a) is much higher.

In addition, the inventors further investigated the OER activity of the AlCoFeMoCr/Pt catalyst of this example after 10000 cycles, and as shown in fig. 10, the stability of Oxygen Evolution Reaction (OER) of the high entropy alloy oxide loaded with noble metal Pt clusters after dealloying the alloy strip prepared in the foregoing step S3 versus the Linear Sweep Voltammetry (LSV) curve shows that the change of the OER activity of the AlCoFeMoCr/Pt catalyst of this example is very small even after 10000 cycles, and is basically ignored, which indicates that the cyclic durability of the AlCoFeMoCr/Pt catalyst of this example is long.

Similarly, the inventors also investigated the ORR activity of the AlCoFeMoCr/Pt catalyst of this example. As shown in fig. 11, a Linear Sweep Voltammetry (LSV) graph of Oxygen Reduction Reaction (ORR) of the high entropy alloy oxide supporting noble metal Pt clusters after dealloying of the alloy strip prepared in the foregoing step S3. As can be seen from the figure, the AlCoFeMoCr/Pt catalyst of this example has higher ORR activity than the existing Pt/C, which indicates that the HEO support enhances the durability of the ORR activity of Pt.

In addition, the inventors further investigated the ORR activity of the alcofepocr/Pt catalyst of this example after 15000 cycles, as shown in fig. 12, the graph of the stability of Oxygen Reduction Reaction (ORR) of the high-entropy alloy oxide supporting noble metal Pt clusters after dealloying the alloy strip prepared in the foregoing step S3 versus Linear Sweep Voltammetry (LSV), which shows that the change of the ORR activity of the alcofepocr/Pt catalyst of this example is very small and almost negligible even after 15000 cycles, indicating that the cycle durability of the alcofepocr/Pt catalyst of this example is long.

The inventor innovatively loads the noble metal nanoclusters on the high-entropy oxide substrate, so that the usage amount of noble metals is greatly reduced, the use cost is reduced, and the high-entropy alloy has a high-entropy effect, a structural lattice distortion effect, a kinetic delayed diffusion effect and the like, so that the noble metal nanoclusters are influenced mutually, the catalytic performance of the material is improved, the cycling stability of the material is improved, the cost of the material is reduced, and the preparation method is an extensible preparation method.

Example 2

This embodiment is substantially similar to embodiment 1, and the same points are not described herein again, and the main differences between them are: the types and proportions of the plurality of metal materials to be smelted are different. In this example, the plurality of metal materials to be melted are particles of aluminum, cobalt, iron, molybdenum, chromium, platinum, palladium, gold, silver, and copper with an atomic number ratio of 95.8:1:1:1:1:0.04:0.04:0.04: 0.04.

Example 3

This embodiment is substantially similar to embodiment 1, and the same points are not described herein again, and the main differences between them are: the types and proportions of the plurality of metal materials to be smelted are different. In this embodiment, the plurality of metal materials to be smelted are aluminum, cobalt, iron, nickel, chromium, and platinum metal particles with an atomic number ratio of 95.9:1:1:1:1: 0.1.

Example 4

This embodiment is substantially similar to embodiment 1, and the same points are not described herein again, and the main differences between them are: the types and proportions of the plurality of metal materials to be smelted are different. In this embodiment, the plurality of metal materials to be smelted are aluminum, cobalt, iron, nickel, chromium, and palladium metal particles with an atomic number ratio of 95.9:1:1:1:1: 0.1.

Example 5

This embodiment is substantially similar to embodiment 1, and the same points are not described herein again, and the main differences between them are: the types and proportions of the plurality of metal materials to be smelted are different. In this embodiment, the plurality of metal materials to be smelted are metal particles of aluminum, cobalt, iron, nickel, molybdenum, and gold in an atomic number ratio of 95.9:1:1:1:1: 0.1.

Example 6

The invention further provides in embodiment 6 a metal-air cell comprising a cathode, an anode, and an electrolyte, the cathode comprising the bifunctional catalyst of any of the preceding embodiments.

In particular, the cathode is an air cathode made of carbon cloth modified with the bifunctional catalyst. Preferably, the loading of the bifunctional catalyst is 0.5mg/cm². The anode is made of zinc foil, preferably 0.1mm thick. The electrolyte is made of a mixed solution of zinc acetate and potassium hydroxide solution, preferably, the concentration of the zinc acetate is 0.2M, and the concentration of the potassium hydroxide is 6.0M.

The open-circuit voltage of the zinc-air battery of the embodiment is 1.49V, and the maximum power density is 132mW/cm²This is compared with the existing Pt/C-IrO₂(open circuit voltage 1.45V, maximum power density 87mW/cm²) The battery is more excellent. And when the current is at 20mA/cm²During discharging, the voltage of the zinc-air battery of the embodiment is 1.12V, the energy density is 821Wh/kg, and the energy density is higher than that of the conventional Pt/C-IrO₂(Voltage: 1.09V, energy density: 751 Wh/kg).

The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-listed embodiments, and any simple changes or equivalent substitutions of technical solutions that can be obviously obtained by those skilled in the art within the technical scope of the present invention are within the protection scope of the present invention.

Claims

1. A method for preparing a bifunctional catalyst, characterized in that it comprises the following steps:

s1: smelting a plurality of metal materials in proportion to obtain an alloy body, wherein the plurality of metal materials comprise aluminum, cobalt, iron, X1 and X2, wherein the X1 is selected from any two or three of chromium, nickel and molybdenum, and the X2 is selected from one or more of platinum, palladium, gold, silver and copper;

s2: rapidly cooling the alloy body;

2. The method according to claim 1, wherein in step S1, the atomic number ratio of the aluminum, the cobalt, the iron, X1 and X2 is 95.8-95.9: 1:1:2: 0.1-0.2.

3. The production method according to claim 1 or 2, wherein in step S1, the plurality of metal materials are aluminum, cobalt, iron, molybdenum, chromium, and platinum in an atomic number ratio of 95.9:1:1:1:1: 0.1.

4. The production method according to claim 1 or 2, wherein in step S1, the plurality of metal materials are melted into a uniform alloy body a plurality of times in an arc melting furnace under an argon-protected atmosphere.

5. The production method according to claim 1, wherein in step S2, the alloy body is rapidly cooled by forming an alloy strip by a strip thrower.

6. The preparation method according to claim 5, wherein in the step S2, the tangential speed of the copper wheel of the belt slinger is 40-45 m/S.

7. The method according to claim 5, wherein in step S2, the alloy strip has a width of 2-5mm and a thickness of 15-25 um.

8. The method according to claim 1, wherein in step S3, the alloy body is cleaned and dried after being dealloyed in 0.5-1.0 mol/L NaOH solution for 8-12 hours to obtain the bifunctional catalyst.

9. A bifunctional catalyst, characterized in that it is prepared according to the process of any one of claims 1 to 8.

10. A metal-air cell comprising a cathode, an anode, and an electrolyte, the cathode comprising the bifunctional catalyst of claim 9.