阅读说明：本技术 铱钨合金纳米材料、其制备方法及作为酸性析氧反应电催化剂的应用 (Iridium-tungsten alloy nano material, preparation method thereof and application of iridium-tungsten alloy nano material as acidic oxygen evolution reaction electrocatalyst ) 是由 王功名 路正 裴志彬 牛淑文 刘馨苗 牛迪 孙达 于 2020-12-28 设计创作，主要内容包括：本发明公开了一种铱钨合金纳米材料及其制备方法和作为酸性析氧反应催化剂的应用,本发明通过水热反应将掺有铱的氧化钨纳米线中间体直接负载在碳布上,并通过高温还原得到了铱钨合金纳米材料。所获得的纳米材料负载在碳布上,可直接作为电解池的电极使用,避免了因粘结剂的使用造成的扩散速率慢和导电性差等问题。相较于传统IrO-2催化剂,本发明选用含量丰富,价格低廉同时抗酸腐蚀的金属钨作为主体结构,大幅减少了贵金属铱的用量,降低了成本。与商用IrO-2相比,该合金材料拥有更高的OER活性和稳定性,具有较高的工业应用前景。(The invention discloses an iridium-tungsten alloy nano material, a preparation method thereof and an acid oxygen evolution reactionThe invention relates to application of a catalyst, in particular to a tungsten oxide nanowire intermediate doped with iridium directly loaded on carbon cloth through hydrothermal reaction, and an iridium-tungsten alloy nano material is obtained through high-temperature reduction. The obtained nano material is loaded on carbon cloth and can be directly used as an electrode of an electrolytic cell, so that the problems of low diffusion rate, poor conductivity and the like caused by the use of a binder are avoided. Compared with the traditional IrO 2 The catalyst adopts the metal tungsten with rich content, low price and acid corrosion resistance as the main body structure, thereby greatly reducing the dosage of noble metal iridium and lowering the cost. And commercial IrO 2 Compared with the prior art, the alloy material has higher OER activity and stability and has higher industrial application prospect.)

1. A preparation method of an iridium-tungsten alloy nano material is characterized by comprising the following steps: the method comprises the following steps:

and (2) mixing the tungsten source solution with weak acid, an iridium source and ammonium salt uniformly in sequence, adding a carrier, preparing an oxide nanowire intermediate through a high-temperature high-pressure hydrothermal reaction, and reducing the obtained oxide nanowire intermediate at a high temperature in a reducing atmosphere to obtain the iridium-tungsten alloy nano material.

2. The preparation method according to claim 1, wherein the tungsten source compound in the tungsten source solution is selected from one or more of alkali metal salts, alkaline earth metal salts or ammonium salts including tungstate radicals;

wherein the concentration of the tungstate radical in the tungsten source solution is 0.01-0.03 mol/L;

wherein the pH value of the tungsten source solution is 1-4.

3. The method of claim 1, wherein: the weak acid is selected from one or more of acetic acid, oxalic acid and hypophosphorous acid;

wherein the concentration of the weak acid in the tungsten source solution is 0.03-0.1 mol/L.

4. The method of claim 1, wherein: the iridium source is selected from one or more of chloroiridate, ammonium chloroiridate and sodium chloroiridate;

wherein the molar ratio of the iridium source to the tungsten source in the solution is 1: 8.5-1: 19.

5. The method of claim 1, wherein: the ammonium salt is selected from one or more of ammonium sulfate, ammonium chloride and ammonium nitrate;

wherein the concentration of ammonium radicals in the ammonium salt in the tungsten source solution is 0.15-0.17 mol/L.

6. The method of claim 1, wherein: the carrier is selected from one or more of carbon cloth, carbon paper and conductive glass;

wherein the carbon cloth and the carbon paper are subjected to hydrophilic treatment before use;

the hydrophilic treatment comprises soaking in concentrated sulfuric acid and concentrated nitric acid.

7. The method of claim 1, wherein: the temperature of the hydrothermal reaction is 120-190 ℃; the time of the hydrothermal reaction is 10-20 h.

8. The method of claim 1, wherein: the temperature of the high-temperature reduction is 500-900 ℃; the high-temperature reduction time is 12-48 h;

wherein the reducing atmosphere is argon-hydrogen mixed gas or carbon monoxide mixed gas;

the hydrogen content is 3-20%.

9. The iridium-tungsten alloy nano material prepared by the preparation method of any one of claims 1 to 8, wherein the mass content of iridium is 3-10%.

10. The iridium-tungsten alloy nano material prepared by the preparation method of any one of claims 1 to 8 or the iridium-tungsten alloy nano material of claim 9 is applied as an acidic oxygen evolution reaction electrocatalyst.

Technical Field

The invention relates to the technical field of material chemistry and electrocatalysis, in particular to an iridium-tungsten alloy nano material, a preparation method thereof and application of the iridium-tungsten alloy nano material as an acidic oxygen evolution reaction electrocatalyst.

Background

Electrocatalysis is an energy conversion technology with wide prospect, and can convert electric energy which is difficult to store into energy in other forms, such as generating clean hydrogen energy by electrocatalysis water decomposition, and electrocatalysis carbon dioxide reduction (CO)₂RR) to generate carbon energy, etc. Among these reactions, Oxygen Evolution Reaction (OER) plays an important role. Taking the water splitting reaction as an example, the reaction can be divided into two half reactions of cathodic Hydrogen Evolution Reaction (HER) and anodic Oxygen Evolution Reaction (OER), wherein the OER process involves a four-electron transfer process, is slow in kinetics, and generally has a high overpotential, thus greatly limiting the efficiency of water splitting. In addition, the existing electrocatalysis system is basically a water system, so that an efficient and stable OER catalyst is developed, the method is beneficial to the carrying out of catalytic decomposition reaction of various water systems, and the efficient storage and clean conversion of energy are realized.

Among many water electrolysis technologies, proton exchange membrane systems (PEM) are widely used in electrocatalytic reactions due to their advantages of high mass transfer efficiency, high product purity, low pollution, etc., and are one of the currently available large-scale water electrolysis technologies, but proton exchange membranes are limited to use in acidic media. In addition, since the catalyst material in an acidic medium is corroded, resulting in a significant decrease in the stability and activity thereof, the research and technical development of the existing OER mainly focuses on the research of the catalyst in a basic medium. Therefore, the development of an efficient OER catalyst which stably works in an acid environment has great significance for the field of hydrogen production by PEM water electrolysis.

The current research shows that the only material capable of stably catalyzing and decomposing water in the acid OER catalyst is iridium dioxide (IrO)₂) And derivatives thereof. However, IrO₂The use of the system for acidic OER still presents significant drawbacks: the stability is strong, but the activity is relatively poor; meanwhile, iridium is a noble metal, which is expensive and not suitable for large-scale development. Therefore, for the development of iridium-based OER catalysts, it is of great significance to improve the catalyst activity and reduce the amount of iridium used, even to find a low-priced substitute for iridium.

Disclosure of Invention

In view of the above, the technical problem to be solved by the present invention is to provide an iridium-tungsten alloy nanomaterial, a preparation method thereof, and an application thereof as an acidic oxygen evolution reaction electrocatalyst, wherein the usage amount of noble metal iridium is reduced, and higher OER activity and stability are obtained.

In order to achieve the purpose, the technical scheme is as follows:

1. the invention provides a preparation method of an iridium-tungsten alloy nano material, which comprises the following steps:

and (2) mixing the tungsten source solution with weak acid, an iridium source and ammonium salt uniformly in sequence, adding a carrier, preparing an oxide nanowire intermediate through a high-temperature high-pressure hydrothermal reaction, and reducing the obtained oxide nanowire intermediate at a high temperature in a reducing atmosphere to obtain the iridium-tungsten alloy nano material.

Preferably, the tungsten source compound in the tungsten source solution is selected from one or more of alkali metal salt, alkaline earth metal salt or ammonium salt of tungstate radical; wherein the concentration of the tungstate radical in the tungsten source solution is 0.01-0.03 mol/L, and more preferably 0.012-0.013 mol/L.

Preferably, the tungsten source compound is selected from one or more of sodium tungstate, calcium tungstate and ammonium tungstate.

In the invention, the pH value of the tungsten source solution is preferably adjusted to 1-4, and more preferably 2.5-3.2.

Preferably, the weak acid is selected from one or more of acetic acid, oxalic acid and hypophosphorous acid. The concentration of the weak acid in the tungsten source solution is preferably 0.03-0.1 mol/L, and more preferably 0.035-0.045 mol/L; more preferably 0.035 to 0.04 mol/L.

Preferably, the iridium source is selected from one or more of chloroiridate, ammonium chloroiridate and sodium chloroiridate.

Preferably, the ammonium salt is one or more selected from ammonium sulfate, ammonium chloride and ammonium nitrate.

Wherein the concentration of ammonium radicals in the ammonium salt in the tungsten source solution is preferably 0.15-0.17 mol/L.

In the invention, the molar ratio of the iridium source to the tungsten source in the solution is preferably 1: 8.5-1: 19.

Preferably, the carrier is selected from one or more of carbon cloth, carbon paper and conductive glass; wherein, the carbon cloth and the carbon paper are preferably subjected to hydrophilic treatment before use.

The hydrophilic treatment preferably comprises soaking in concentrated sulfuric acid and concentrated nitric acid, and the like.

Preferably, the temperature of the hydrothermal reaction is 120-190 ℃; the time of the hydrothermal reaction is 10-20 h.

Preferably, the high-temperature reduction temperature is 500-900 ℃; the high-temperature reduction time is 12-48 h.

In the present invention, preferably, the reducing atmosphere is argon-hydrogen mixed gas or carbon monoxide mixed gas; among them, the hydrogen content is preferably 3% to 20%.

2. The invention provides an iridium-tungsten alloy nano material prepared by the preparation method, wherein the mass content of iridium is 3-10%.

The mass of the iridium is more preferably 7-10%; specifically, the content is 3%, 4%, 4.5%, 5%, 7%, 7.5%, 8%, 9%, 10%, or a range in which any of the above values is an upper limit value or a lower limit value.

3. The invention provides an iridium-tungsten alloy nano material prepared by the preparation method or an application of the iridium-tungsten alloy nano material as an acidic oxygen evolution reaction electrocatalyst.

Specifically, the invention provides an acidic oxygen evolution reaction working electrode, which is obtained by loading the iridium-tungsten alloy nano material on the surface of a carrier material.

Compared with the prior art, the iridium-doped tungsten oxide is directly loaded on the carbon cloth through hydrothermal reaction, and the iridium-tungsten alloy nano material is obtained through high-temperature reduction. The obtained nano material is loaded on carbon cloth and can be directly used as an electrode of an electrolytic cell, so that the problems of low diffusion rate, poor conductivity and the like caused by the use of a binder are avoided, and the electrode manufacturing process is simplified. Compared with the traditional IrO₂The catalyst takes noble metal Ir as a main structure, the defects of high price and low reserve volume greatly limit the large-scale development of the catalyst, and the invention selects metal tungsten with rich content, low price and acid corrosion resistance as the main structure, thereby greatly reducing the dosage of the iridium and reducing the cost. Meanwhile, the reduction of active sites improves the atom utilization rate of iridium, and accords with the green chemical concept. And commercial IrO₂Compared with the prior art, the alloy material has higher OER activity and stability and has higher industrial application prospect.

In addition, the acidic OER related to the present invention has a fatal defect that the non-noble metal catalyst is easily subjected to surface reconstruction and thus is deactivated in an acidic solution, and the currently known materials for stably catalyzing the acidic OER are limited to noble metal iridium-based catalysts. The material takes non-noble metal tungsten as a main material, so that the catalytic performance is greatly improved, and the material has excellent stability. Constant current (10 mA/cm) for 20 continuous hours²) After the test, the overpotential of the alloy is increased by only 20 mV.

Drawings

FIG. 1 is an XRD spectrum of IrW nano-alloy material prepared in example 1 of the present invention;

FIG. 2 is a scanning electron microscope photograph of IrW nm alloy material prepared in example 1 of the present invention;

FIG. 3 is a comparative LSV curve of IrW nm alloy material prepared in example 1 of the present invention before and after 20h test;

FIG. 4 shows Ir nanoalloy material and commercial IrO prepared in example 1 of the present invention₂The timing potential analysis comparison graph of (1);

FIG. 5 is a comparative LSV curve of IrW nm alloy materials prepared in examples 1-4 of the present invention.

Detailed Description

In order to further illustrate the present invention, the iridium tungsten alloy nanomaterial provided by the present invention, the preparation method thereof, and the application thereof as an acidic oxygen evolution reaction electrocatalyst are described in detail below with reference to examples.

Example 1

IrW preparation of alloy nano material:

weighing 4.123g of sodium tungstate dihydrate and 4.41g of oxalic acid, stirring and dissolving in 100ml of water, dropwise adding 1mol/L dilute sulfuric acid, detecting by using an acidic precise pH test paper, and adjusting the pH to 3.2 to serve as mother liquor for later use. Taking 20ml of mother liquor, weighing 1.586g of ammonium sulfate in the mother liquor, stirring for dissolving, weighing 0.25g of chloroiridic acid (with the effective content of 35%) in a beaker containing the solution after the solution is clarified, and quickly stirring until the chloroiridic acid is completely dissolved, wherein the solution is brown and transparent. The brown solution is transferred into a 25ml polytetrafluoroethylene hydrothermal reaction kettle, and a piece of hydrophilic carbon cloth (2 cm multiplied by 2cm and soaked by concentrated sulfuric acid and concentrated nitric acid for one week in advance) is placed in the reaction kettle and is leaned against the wall of the container to be kept vertical. Putting the precursor into a stainless steel reaction kettle shell, screwing a kettle cover, and reacting in an oven at 180 ℃ for 18h to obtain the iridium-doped tungsten trioxide nanowire precursor growing on the carbon cloth. And (3) oscillating and cleaning the carbon cloth, drying the carbon cloth in vacuum at 60 ℃, and finally reducing the carbon cloth in a tubular furnace in 3% argon-hydrogen mixed gas at 600 ℃ for 12 hours to obtain IrW alloy nanoparticles.

The IrW alloy nano-material prepared by the method is shown by an inductively coupled atomic absorption spectrometry (ICP-AES) test that: the iridium content was 7 wt%.

The crystal structure of the IrW alloy nano-material prepared in the above way is the same as that of W metal, and the X-ray diffraction spectrum (XRD) thereof is shown in figure 1.

The prepared IrW alloy nano material can be determined to be in a nano particle shape through a scanning electron microscope picture, and the scanning electron microscope picture is shown as 2.

The method for testing the acidic OER performance of the prepared IrW alloy nano material comprises the following steps:

data collection was performed using a chi660e electrochemical workstation. The test is carried out by adopting a three-electrode electrolytic cell, the working electrode is the prepared carbon cloth loaded with IrW alloy nano materials, the reference electrode is an Ag/AgCl electrode, the counter electrode is a platinum sheet electrode, and the electrolyte is 0.5mol/L H₂SO₄And (3) solution.

And (3) activity test: linear Sweep Voltammogram (LSV), test voltage range 0.6-1.6V vs. sce, sweep rate 5 mV/s. And testing for several times until the data is stable, and taking the last time.

And (3) stability testing: chronopotentiometric analysis (CP) with a test current density of 10mA/cm²And testing for 20h, and recording a voltage curve under constant current density for 20h continuously.

For commercial IrO under the same conditions₂OER performance testing was performed for comparison.

The experimental results are as follows:

the electrochemical results are shown in fig. 3, fig. 4 and table 1.

LSV results indicate commercial IrO₂At 10mA/cm²The overpotential at current density of (a) is 485mV, while the overpotential of the IrW alloy material of this example is only 261mV under the same test conditions.

CP results indicate commercial IrO₂Starting to decay until deactivation after 3h of the test, while the IrW alloy material of this example was stable after 20h under the same test conditions, the tested material was subjected to the LSV test and the overpotential was found to rise by only 20mV (10 mA/cm)²)。

In conclusion, the IrW alloy material prepared by the method can be applied to acidic OER catalysts, and the activity and stability of the IrW alloy material far exceed those of current commercial IrO₂。

Examples 2 to 4

The remaining conditions were the same as in example 1 except that only the amount of the Ir source added was changed (as shown in Table 1), and the OER catalytic performance is shown in Table 1.

The comparison of the different examples shows that the catalyst activity is optimized when the Ir content is 7 wt%, and the catalytic performance does not increase significantly when the Ir content is increased further.

TABLE 1 summary of Ir loadings and electrochemical properties in examples 1-4

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.