阅读说明：本技术 一种具有高长径比的铱氧化物纳米线及其水电解膜电极的制备方法 (Iridium oxide nanowire with high length-diameter ratio and preparation method of water electrolysis membrane electrode of iridium oxide nanowire ) 是由 史言 闫常峰 麦奕朗 申丽莎 卢卓信 郭常青 王志达 谭弘毅 于 2021-07-12 设计创作，主要内容包括：本发明公开了一种具有高长径比的铱氧化物纳米线及其水电解膜电极的制备方法。一种具有高长径比的铱氧化物纳米线的制备方法,包括如下步骤：(1)将碳酸钾粉末与金属铱粉末混合研磨均匀得到混合粉末；(2)将步骤(1)得到的混合粉末进行热处理,得到黑色产物,黑色产物经酸洗和水洗后,得到铱氧化物纳米线。本发明所制备的铱氧化物纳米线长度达数十至数百微米,更适应水电解器中粗糙的多孔钛集电器,可提升纳米线电极的贵金属利用率以及在高电流密度下的稳定性。(The invention discloses an iridium oxide nanowire with a high length-diameter ratio and a preparation method of a water electrolysis membrane electrode of the iridium oxide nanowire. A preparation method of iridium oxide nanowires with high aspect ratio comprises the following steps: (1) mixing potassium carbonate powder and metal iridium powder, and uniformly grinding to obtain mixed powder; (2) and (2) carrying out heat treatment on the mixed powder obtained in the step (1) to obtain a black product, and carrying out acid washing and water washing on the black product to obtain the iridium oxide nanowire. The iridium oxide nanowire prepared by the method has the length of tens to hundreds of microns, is more suitable for a rough porous titanium current collector in a water electrolyzer, and can improve the utilization rate of noble metals of the nanowire electrode and the stability of the nanowire electrode under high current density.)

1. A preparation method of iridium oxide nanowires with high length-diameter ratio is characterized by comprising the following steps:

(1) mixing potassium carbonate powder and metal iridium powder, and uniformly grinding to obtain mixed powder;

(2) and (2) carrying out heat treatment on the mixed powder obtained in the step (1) to obtain a black product, and carrying out acid washing and water washing on the black product to obtain the iridium oxide nanowire.

2. The method for preparing iridium oxide nanowires with high aspect ratio according to claim 1, wherein the mass ratio of the potassium carbonate powder to the metallic iridium powder in step (1) is 1:1-1: 5.

3. The method for preparing iridium oxide nanowires with high aspect ratio according to claim 1, wherein the specific conditions of the heat treatment in the step (2) are 750 ℃ to 900 ℃ for 2 to 24 hours.

4. The method for preparing iridium oxide nanowires with high aspect ratio according to claim 1, wherein the black product obtained in step (2) is subjected to acid washing and water washing under the specific conditions: the black product was washed with 0.5M hydrochloric acid at 50 ℃ for 1-24 hours and then with deionized water.

5. The iridium oxide nanowire with high aspect ratio prepared by the preparation method of claim 1, wherein the aspect ratio of the nanowire is more than 1000, the length of the nanowire is 30-200 μm, and the diameter of the nanowire is 20-80 nm.

6. Use of the iridium oxide nanowires with high aspect ratio as claimed in claim 5 in water electrolyte membrane electrodes.

7. A water electrolysis membrane electrode, characterized by comprising a solid polymer water electrolysis nanowire anode, wherein the solid polymer water electrolysis nanowire anode consists of the iridium oxide nanowire with high aspect ratio, the solid polymer membrane and the porous titanium current collector, the iridium oxide nanowire is loaded on the surfaces of the solid polymer membrane and the porous titanium current collector, and the loading amount of the iridium oxide nanowire is 0.1-2mg/cm²。

8. The water electrolysis membrane electrode assembly according to claim 7, wherein the solid polymer water electrolysis nanowire anode is prepared by the following steps: and preparing the iridium oxide nanowires into catalyst ink by using isopropanol, and combining the catalyst ink with a solid polymer film or a porous titanium current collector by using a coating method, a spraying method or a transfer printing method to obtain the solid polymer water electrolysis nanowire anode.

9. The water electrolysis membrane electrode assembly according to claim 8, wherein the solid polymer water electrolysis nanowire anode is prepared by the following steps: adding isopropanol into the iridium oxide nanowire to prepare catalyst ink, wherein the mass ratio of the iridium oxide nanowire to the isopropanol is 1:10-1:40, then adding 5% by mass of Nafion emulsion or 6% by mass of PTFE emulsion to enable the mass fraction of Nafion or PTFE dry powder to be 2% -20%, carrying out ultrasonic mixing for 30 minutes in an ice water bath, loading the catalyst ink combined with a solid polymer film on the surface of a porous titanium current collector through coating, spraying or transferring, and drying to obtain the solid polymer water electrolysis nanowire anode.

Technical Field

The invention relates to the technical field of water electrolysis and electrocatalysis, in particular to an iridium oxide nanowire with a high length-diameter ratio and a preparation method of a water electrolysis membrane electrode thereof.

Background

The solid polymer water electrolysis technology has the advantages of high electrolysis efficiency, large current density, high reaction speed and suitability for fluctuating current, and can be combined with renewable energy sources to realize the efficient hydrogen production and energy storage of the renewable energy sources, so the technology has great application potential in the aspect of carbon neutralization. The current solid polymer water electrolyzer has the problem of high cost, and the commercial application of the solid polymer water electrolyzer is restricted. Therefore, the use amount of noble metals is greatly reduced, and the development of high-efficiency and low-cost membrane electrode materials is the current research focus.

The one-dimensional nanowire material has high stability and good electronic conductivity, so that the dosage of noble metals in the traditional membrane electrode is expected to be reduced. At the anode of the water electrolyzer, iridium oxide is the catalyst with the best comprehensive performance at present. At present, Free standing iridium oxide one-dimensional nanowires, namely, preparation methods of iridium oxide nanowires without matrix growth, mainly comprise an electrostatic spinning method and a hydrothermal method. The method has the defects of short length (several micrometers), low length-diameter ratio, high requirement on preparation equipment, low yield and unsuitability for large-scale preparation of the iridium oxide nanowires. Because the aperture of the anode current collector is generally in the range of 30-200 μm, the iridium oxide nanowires with short length easily enter the inner hole of the current collector along with gas products, and the nanowires are easy to gradually run off when the anode current collector runs for a long time or under high current density, so that the stability of the electrode is difficult to ensure. Increasing the length of the nanowires is therefore a better solution.

In addition, the anode current collector and anode catalytic layer interface can affect water electrolyzer performance. The flatness of the surface of the current collector is increased, and a leveling layer or a catalytic layer with a gas and water rapid channel is established, so that the performance of the water electrolyzer can be ensured under the condition of ultralow noble metal loading. Titanium plates formed by pressing titanium fibers or powdered titanium are mainly used as current collectors in current water electrolyzers. But because of the titanium processing technology, the diameter of the titanium fiber is more than 10 μm, so compared with the nanometer catalyst, the flatness is not enough, which is not beneficial to improving the utilization rate of the noble metal in the membrane electrode. And the use of one-dimensional iridium oxide nanowires is expected to solve the problem. When the iridium oxide nanowires are combined with the current collector, the nanowires with proper lengths can be intensively kept on the surface of the current collector without entering the inner hole, so that a flat surface is favorably formed, the contact area with a polymer film is enlarged under the condition of certain noble metal loading, and the performance of the membrane electrode is favorably improved.

Disclosure of Invention

The invention solves the problems of low utilization rate of noble metals restricting the anode of a water electrolyzer and lack of a practical anode leveling layer material in the prior art, and aims to provide an iridium oxide nanowire with high length-diameter ratio and a preparation method of a water electrolysis membrane electrode thereof.

In order to achieve the purpose, the invention adopts the technical scheme that: a preparation method of iridium oxide nanowires with high aspect ratio comprises the following steps:

(1) mixing potassium carbonate powder and metal iridium powder, and uniformly grinding to obtain mixed powder;

(2) and (2) carrying out heat treatment on the mixed powder obtained in the step (1) to obtain a black product, and carrying out acid washing and water washing on the black product to obtain the iridium oxide nanowire.

The iridium oxide nanowire with the length of tens to hundreds of micrometers and high length-diameter ratio can be obtained by using the preparation method of the iridium oxide nanowire.

Preferably, the mass ratio of the potassium carbonate powder to the metallic iridium powder in the step (1) is 1:1-1: 5.

Preferably, the specific conditions of the heat treatment described in the step (2) are a heat treatment at 750 ℃ to 900 ℃ for 2 to 24 hours.

Preferably, the specific conditions of acid washing and water washing of the black product in the step (2) are as follows: the black product was washed with 0.5M hydrochloric acid at 50 ℃ for 1-24 hours and then with deionized water.

The second purpose of the invention is to protect the iridium oxide nanowire with high length-diameter ratio, which is prepared by the preparation method, wherein the length-diameter ratio of the nanowire is more than 1000, the length of the nanowire is 30-200 mu m, and the diameter of the nanowire is 20-80 nm.

The third purpose of the invention is to protect the application of the iridium oxide nanowires with high aspect ratio in the water electrolysis membrane electrode.

The invention also protects a water electrolysis membrane electrode, which comprises a solid polymer water electrolysis nanowire anode, wherein the solid polymer water electrolysis nanowire anode consists of the iridium oxide nanowire with high length-diameter ratio, a solid polymer film and a porous titanium current collector (a porous titanium plate), and the loading capacity of the iridium oxide nanowire on the surfaces of the solid polymer film and the porous titanium current collector is 0.1-2mg/cm²。

The iridium oxide nanowires are positioned between the solid polymer film and the porous titanium current collector, and the iridium oxide nanowires are randomly stacked and can be combined with the solid polymer film and the porous titanium current collector.

The invention improves the interface of the catalyst layer/the current collector by constructing the anode nanowire catalyst layer (leveling layer) which is oxidation-resistant and has high electronic conductivity, improves the performance of the membrane electrode and reduces the consumption of noble metals, and solves the problems that the utilization rate of the noble metals for restricting the anode of the water electrolyzer is not high and the anode leveling layer material which can be used practically is lacked at present. Specifically, the iridium oxide nanowires with longer sizes are paved on the surface of an uneven porous titanium plate to form a flat anode leveling layer with gas and water transmission channels, so that the contact area between the flat surface and a solid polymer film is increased. The high length-diameter ratio also ensures the smaller diameter of the nanowire, is beneficial to improving the specific surface area of the catalyst, and simultaneously improves the oxidation resistance of the titanium current collector under high oxidation potential by utilizing the oxidation resistance of iridium oxide. In addition, the length of the iridium oxide nanowire exceeds the average pore diameter of the anode current collector of the water electrolyzer, and the iridium oxide nanowire can be directly prepared into a membrane electrode, so that the In-plane conductivity of the electrode is ensured, and the stability of the electrode is improved.

Preferably, the solid polymer water electrolysis nanowire anode is prepared by the following steps: and preparing the iridium oxide nanowires into catalyst ink by using isopropanol, and combining the catalyst ink with a solid polymer film or a porous titanium current collector by using a coating method, a spraying method or a transfer printing method to obtain the solid polymer water electrolysis nanowire anode.

Further preferably, the solid polymer water electrolysis nanowire anode is prepared by the following steps: adding isopropanol into the iridium oxide nanowire to prepare catalyst ink, wherein the mass ratio of the iridium oxide nanowire to the isopropanol is 1:10-1:40, then adding 5% by mass of Nafion emulsion or 6% by mass of PTFE emulsion to enable the mass fraction of Nafion or PTFE dry powder to be 2% -20%, carrying out ultrasonic mixing for 30 minutes in an ice water bath, loading the catalyst ink combined with a solid polymer film on the surface of a porous titanium current collector through coating, spraying or transferring, and drying to obtain the solid polymer water electrolysis nanowire anode.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention provides a preparation method of iridium oxide nanowires with longer length and high length-diameter ratio. The material can be used for preparing a membrane electrode of a water electrolyzer and an anode leveling layer, so that the performance of the membrane electrode is improved and the cost is reduced. The iridium oxide nanowire prepared by the method has longer length (tens to hundreds of microns), and is more suitable for rough porous titanium current collectors in water electrolyzers. The stability of the nanowire electrode under high current density can be improved.

2. The invention provides a preparation method of a solid polymer water electrolysis nanowire anode, which utilizes an iridium oxide nanowire with moderate length to be overhead on the surface of porous titanium to improve the surface flatness of the porous titanium, increase the contact area with a solid polymer film and provide enough gas and water transmission channels and an anti-oxidation protective layer. Compared with the traditional carbon and antimony doped tin oxide anode leveling layer, the method has higher oxidation resistance and flatness, and simultaneously ensures the necessary electronic conductivity.

3. The invention uses a simple high-temperature solid phase method to prepare Free standing iridium oxide nano-wire. According to the method, the high-yield nanowires can be obtained only by mixing and simply sintering the precursors, and the method is simpler and more convenient than the traditional hydrothermal method and electrostatic spinning method, has lower requirements on instruments, and is suitable for large-scale production.

Drawings

FIG. 1 is a schematic view of an iridium oxide nanowire membrane electrode and an anode sublayer in accordance with the present invention;

FIG. 2 is an electron microscope image of the iridium oxide nanowires prepared in example 1;

FIG. 3 Electron microscopy images of iridium oxide nanowire catalytic layers (sublayers) sprayed onto the surface of a porous titanium current collector in example 1;

fig. 4 is a water electrolysis polarization curve and stability graph of the membrane electrodes prepared by using the iridium oxide nanowires of example 1 and comparative example 1.

Detailed Description

The following examples are further illustrative of the present invention and are not intended to be limiting thereof. The equipment and reagents used in the present invention are, unless otherwise specified, conventional commercial products in the art.

As shown in fig. 1, a schematic diagram of the preparation of two membrane electrodes according to the present invention is shown. The first is that the iridium oxide nanowires can be directly combined with a membrane to form a membrane electrode, and then combined with a collector without a flattening layer to form a membrane electrode. The second is that the nano-wire material is sprayed on the surface of the porous current collector to form an anode leveling layer, and then the anode leveling layer is directly contacted with the solid polymer film to form the membrane electrode.

Example 1

A solid polymer water electrolysis nanowire anode is prepared by the following steps:

(1) taking potassium carbonate powder and metal iridium powder, uniformly mixing in a mortar, wherein the mass ratio of the potassium carbonate to the metal iridium is 1:3, and then placing in a muffle furnace under air atmosphere, and sintering at 800 ℃ for 4 hours to obtain a black product.

(2) And (2) adding the black product obtained in the step (1) into 0.5M dilute hydrochloric acid, and stirring and pickling at 50 ℃ for 12 hours. And then, washing for 3 times by using suction filtration, and heating and drying for 12 hours at the temperature of 80 ℃ to obtain the iridium oxide nanowire.

(3) And (3) taking 10mg of iridium oxide nanowires obtained in the step (2), adding 200mg of isopropanol, carrying out ultrasonic treatment for 15 minutes, adding 5% by mass of Nafion emulsion to enable the Nafion content to be 5%, carrying out ultrasonic treatment for 30 minutes in an ice water bath to obtain catalyst ink combined with a solid polymer film, spraying the catalyst ink combined with the solid polymer film on the surface of a porous titanium current collector, and drying to obtain the solid polymer water electrolysis nanowire anode.

The load capacity of the iridium oxide nanowire is determined by a gravimetric method, and the electrochemical active area of a single cell of the water electrolyzer is 8cm²The iridium loading capacity of the anode is 0.4mg/cm². The cathode catalyst is a traditional platinum-carbon catalyst, and the platinum loading capacity is 0.2mg/cm²And the solid polymer film is a Nafion117 film. The single cell performance test was conducted at 80 ℃ under atmospheric pressure.

Fig. 2 is an electron microscope image of the iridium oxide nanowire material prepared in this example, and it can be seen from fig. 2 that the surface pore diameter of the porous titanium current collector is significantly larger than 50 μm, and a leveling layer cannot be formed by spraying with the particle ink. The material prepared by the method has no particles basically, which shows that the method can obtain the nanowire material with high yield, and the nanowire can be arranged on the surface of the titanium current collector to form a leveling layer and ensure the water and gas transmission. In addition, the lengths of the nanowires are all more than 60 micrometers, which shows that the method can obtain the iridium oxide nanowires with the lengths of tens of micrometers, the diameters of the nanowires are about 60 micrometers, and the length-diameter ratio is more than 1000.

Fig. 3 is an electron microscope image of an iridium oxide nanowire catalytic layer (sublayer) sprayed onto the surface of a porous titanium current collector. As can be seen from FIG. 3, the porous layer formed by the iridium oxide nanowires can be suspended on the surface of the porous titanium, so that the contact area with the film can be increased, and good gas and water transmission channels can be provided.

Comparative example 1

Comparative example 1 differs from example 1 in that: preparing a membrane electrode by adopting commercially available iridium oxide powder, wherein the anode iridium loading is 0.9mg/cm²Other preparation processes and test conditions were exactly the same as in example 1.

Fig. 4 is a water electrolysis polarization curve and stability curve of a membrane electrode prepared by using an iridium oxide nanowire material. Iridium loading of 0.4mg/cm was used in example 1²The membrane electrode (supported on the surface of the current collector) was at 1A/cm²The lower single-cell voltage is 1.8V (curve 2), and the life test shows that the membrane electrode can still keep stable under a lower loading capacity. Curve 1 of fig. 4 is a polarization curve of the powdered iridium oxide film electrode of comparative example 1. It can be seen that the membrane electrode using powdered iridium oxide at high loading exhibited similar performance to that of example 1, indicating that the membrane electrode prepared using the method of the present invention also achieved electrical performance consistent with that of the high-loading powdered catalyst membrane electrode using lower loading.

Example 2

This example differs from example 1 in that: the mass ratio of potassium carbonate to iridium metal in the step (1) is 1:1, the sintering temperature is 750 ℃ for 24 hours. And (3) taking the iridium oxide nanowire with the mass of 20mg, and replacing the Nafion solution with PTFE emulsion with the mass fraction of 6% to ensure that the content of PTFE is 2%. The remaining steps and test methods were completely identical to those of example 1.

The length of the iridium oxide nanowire is 100-200 mu m, and the diameter is about 100 nm. The iridium loading capacity in the membrane electrode anode of the water electrolyzer is 2mg/cm²Single cell test 1A/cm²The lower cell voltage is 1.73V.

Example 3

This example differs from example 1 in that: the mass ratio of the potassium carbonate to the iridium metal in the step (1) is 1:5, the sintering temperature is 900 ℃ for 2 hours. And (3) taking the iridium oxide nanowire with the mass of 5mg, and replacing the Nafion solution with PTFE emulsion with the mass fraction of 6% to ensure that the content of PTFE is 5%. The remaining steps and test methods were completely identical to those of example 1.

The iridium oxide nanowire has a length of 50-80 μm and a diameter of about 60 nm. The iridium loading capacity in the membrane electrode anode of the water electrolyzer is 0.1mg/cm²Single cell test 1A/cm²The lower single-tank voltage is 1.85V.

Example 4

This example differs from example 1 in that: in the step (3), the Nafion solution is replaced by PTFE emulsion with the mass fraction of 6%, the content of PTFE is 20%, and the catalyst ink is sprayed on the surface of a Nafion117 membrane. The remaining steps and test methods were completely identical to those of example 1. Single-groove performance test 1A/cm²The lower single cell voltage is 1.76V.

The above is only a preferred embodiment of the present invention, and it should be noted that the above preferred embodiment should not be considered as limiting the present invention, and the protection scope of the present invention should be subject to the scope defined by the claims. It will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the spirit and scope of the invention, and these modifications and adaptations should be considered within the scope of the invention.