CN118326439A - Preparation method and application of ruthenium-doped high-entropy oxide - Google Patents

Abstract

The invention provides a preparation method of ruthenium doped high entropy oxide, which comprises the following steps: preparing a precursor solution by taking metal chloride salt as a solute, wherein the metal chloride salt comprises any 5 of ferric chloride, nickel chloride, cobalt chloride, copper chloride, cerium chloride and molybdenum chloride, and further comprises ruthenium chloride; loading the precursor solution on a substrate, and drying; and performing flash heat treatment on the substrate loaded with the precursor solution to obtain the ruthenium doped high-entropy oxide. The method can solve the technical problems of high production cost and poor stability in use in the preparation of the high-entropy oxide containing noble metal in the prior art.

Description

A preparation method and application of ruthenium-doped high entropy oxide

Technical Field

The present invention relates to the technical field of electrocatalytic material preparation, and in particular to a preparation method and application of a ruthenium-doped high-entropy oxide.

Background technique

High entropy oxide materials refer to materials whose lattices contain five or more equimolar elements randomly distributed in a single-phase lattice. Their preparation methods mainly include high-temperature solid-phase reaction method, magnetron sputtering method, wet chemical method, solution combustion synthesis method, etc.

When high entropy oxides are used as water splitting electrocatalysts, if they contain noble metals, they are considered to be one of the best candidates for the most promising water splitting electrocatalysts. Although noble metals have higher catalytic efficiency, on the one hand, the scarcity and high price of noble metals increase the production cost; on the other hand, the high entropy oxides containing noble metals prepared by existing technologies have poor stability in actual use.

Summary of the invention

In view of the shortcomings of the prior art, the present invention proposes a method for preparing a ruthenium-doped high-entropy oxide to solve the technical problems of high production cost and poor stability during use when preparing high-entropy oxides containing precious metals in the prior art.

The technical solution adopted by the present invention is as follows:

In a first aspect, a method for preparing a ruthenium-doped high entropy oxide is provided, comprising the following steps:

A precursor solution is prepared using a metal chloride salt as a solute, wherein the metal chloride salt includes any five of the six types of ferric chloride, nickel chloride, cobalt chloride, copper chloride, cerium chloride, and molybdenum chloride, and also includes ruthenium chloride;

Loading the precursor solution on a substrate and drying it;

The substrate loaded with the precursor solution is flash-heat treated to obtain a ruthenium-doped high-entropy oxide.

Furthermore, the precursor solution is prepared by ultrasonic dispersion method, and the concentration is 0.05-0.5 mol/L.

Further, the metal chloride salt includes ferric chloride, cobalt chloride, nickel chloride, copper chloride and cerium chloride in a molar ratio of 1:1:1:1:1.

Furthermore, the metal chloride salt includes ferric chloride, cobalt chloride, nickel chloride, copper chloride and molybdenum chloride in a molar ratio of 1:1:1:0.35:0.75.

Furthermore, the metal chloride salt includes ferric chloride, nickel chloride, copper chloride, molybdenum chloride and cerium chloride in a molar ratio of 1:1:0.3:0.3:0.4.

Furthermore, the concentration of ruthenium chloride is 0.001-0.02 mol/L.

Furthermore, the substrate includes carbon cloth, carbon paper or biomass carbon; the precursor solution is loaded on the substrate by immersion or dripping.

Furthermore, the discharge voltage of the flash heat treatment is 60-120V, and the discharge time is 50-1000ms.

In a second aspect, a ruthenium-doped high entropy oxide is provided, which is prepared by the method provided in the first aspect.

Furthermore, ruthenium-doped high entropy oxides were used as electrocatalysts.

It can be seen from the above technical solution that the beneficial technical effects of the present invention are as follows:

1. The time required to prepare high-entropy oxides doped with precious metals is extremely short, the process steps are few, and it is simple and easy; and no binder needs to be added when used for electrode performance testing, which improves production efficiency and reduces costs while ensuring that the active sites are fully exposed.

2. Not only can it be extended to different substrates, transient high temperature can also increase the mutual solubility of immiscible components, thereby broadening the selection range of components to suit different reaction scenarios, and can prepare a variety of different components of doped precious metal high entropy oxides.

3. While triggering the lattice oxygen to participate in the reaction, the stability of the structure can be maintained, and the electrocatalytic activity and stability of the material have been significantly improved.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

FIG1 is a flow chart of a preparation method according to an embodiment of the present invention;

FIG2 is a performance diagram of Ru-FeCoNiCuCe and FeCoNiCuCe loaded on carbon cloth in an embodiment of the present invention tested in 1M KOH for OER;

Figure 3 is a performance diagram of HER tested in 1M KOH in Ru-FeCoNiCuCe and FeCoNiCuCe loaded on carbon cloth;

Figure 4 shows the LSV curves of UOR tested on Ru-FeCoNiCuCe and FeCoNiCuCe loaded on carbon cloth in 1M KOH.

Figure 5 is a performance diagram of Ru-FeCoNiCu _0.35 Mo _0.75 loaded on carbon cloth in 1M KOH test of OER;

Figure 6 is a performance diagram of HER tested in 1M KOH for Ru-FeCoNiCu _0.35 Mo _0.75 loaded on carbon cloth;

Figure 7 is a performance diagram of Ru-FeNiCu _0.3 Mo _0.3 Ce _0.4 supported on carbon cloth tested in 1M KOH for OER;

Figure 8 is a performance diagram of HER tested in 1M KOH for Ru-FeNiCu _0.3 Mo _0.3 Ce _0.4 loaded on carbon cloth.

Detailed ways

The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

Example

This embodiment provides a method for preparing a ruthenium-doped high-entropy oxide. The raw materials required for preparing the ruthenium-doped high-entropy oxide include:

Substrate: In a specific embodiment, the substrate can be made of carbon-based materials such as carbon cloth, carbon paper, and biomass carbon;

Metal chloride salts. In this embodiment, the metal chloride salts are selected from 7 types: ferric chloride, nickel chloride, cobalt chloride, copper chloride, cerium chloride, molybdenum chloride and ruthenium chloride.

The preparation of high entropy oxides was carried out as follows:

1. Prepare precursor solution using metal chloride as solute

The metal chloride salt is a combination of 5+1, that is, any five of the six types of ferric chloride, nickel chloride, cobalt chloride, copper chloride, cerium chloride, and molybdenum chloride are selected, and ruthenium chloride is added at the same time.

The solvent of the precursor solution is not limited, as long as the metal chloride salt can be evenly dispersed, such as water, ethanol, hydrochloric acid, etc., preferably ethanol is used as the solvent. During preparation, the six metal chloride salts are added into the solvent together, regardless of the order.

The precursor solution can be prepared by any method of the prior art, preferably by ultrasonic dispersion. During ultrasonic dispersion, the equipment used is an ultrasonic cleaning machine, and the time is determined according to the solubility of the metal chloride salt until a uniform solution is formed. The ultrasonic dispersion time is 20 minutes; the concentration and proportion of the precursor solution are adjusted by controlling the solute mass, and the concentration is preferably 0.05-0.5 mol/L.

2. Load the precursor solution on the substrate and dry it

In some embodiments, a certain amount of precursor solution can be loaded on the substrate by soaking or dripping, and the amount of loaded solution is selected according to the area of the substrate; then the substrate loaded with the precursor solution is placed in an oven for drying. In a specific embodiment, the oven temperature is set to 60°C for drying for 3 hours.

This method enables the in-situ growth of materials on the substrate, avoiding the binders used in traditional electrode preparation methods.

3. Flash heat treatment of the substrate loaded with the precursor solution to obtain ruthenium-doped high entropy oxide

The substrate loaded with the precursor solution is placed in a flash heating device for heating, and the ruthenium-doped high entropy oxide is formed on the surface of the substrate by in-situ conversion of the precursor salt. In a specific embodiment, the flash heating treatment is flash Joule heating, and the discharge voltage of the flash heating device is preset to 60-120V, preferably 80V; the preset discharge time is 50-1000ms, preferably 400ms.

The above preparation method is used to introduce the precious metal ruthenium into a more stable high entropy oxide substrate in the form of doping sites, which has the following advantages:

(1) The high entropy effect of the substrate oxide can inhibit the dissolution and aggregation of ruthenium;

(2) The ruthenium doping strategy promotes charge transfer at the interface through the interface effect, optimizes the electronic structure of the active site, and can improve the electrocatalytic activity;

(3) It can greatly reduce the use of precious metal ruthenium and reduce production costs.

The following comparative test is used for analysis:

The first set of experiments: Preparation of ruthenium-doped high-entropy oxide using carbon cloth substrate

The carbon cloth substrate was made of commercial carbon cloth, and precursor solutions with different concentrations of 0.05 mol/L, 0.1 mol/L, 0.2 mol/L, 0.3 mol/L, 0.4 mol/L, and 0.5 mol/L were prepared respectively. The solution concentration and the molar ratio of different components were adjustable.

When preparing the precursor solution, any five of the six metal chloride salts of iron, nickel, cobalt, copper, molybdenum, and cerium can be selected in equal molar or different molar ratios; the following three have good test results:

Iron: cobalt: nickel: copper: cerium = 1:1:1:1:1;

Iron: cobalt: nickel: copper: molybdenum = 1:1:1:0.35:0.75;

Iron: nickel: copper: molybdenum: cerium = 1:1:0.3:0.3:0.4.

For ruthenium chloride, the concentration can be selected from 0.001 to 0.02 mol/L, preferably 0.01 mol/L.

After using the above-mentioned various combinations of metal chloride salts to prepare the precursor solution by ultrasonic dispersion, the precursor solution is dripped onto the carbon cloth substrate or the carbon cloth substrate is immersed in the precursor solution for 30 minutes, and then dried in an oven at 40°C. The dried carbon cloth is fixed on the sample stage in the flash heat device, and the sample is prepared at a discharge voltage of 80V and a discharge time of 400ms to obtain a variety of ruthenium-doped high-entropy oxides. For example:

Ru-FeCoNiCuCe, Ru-FeCoNiCuMo, Ru-FeNiCuMoCe.

The second set of experiments: Preparation of high entropy oxide without ruthenium doping using carbon cloth substrate

The second experiment was basically the same as the first experiment, except that no ruthenium chloride was added when preparing the precursor solution. The second experiment produced a variety of high entropy oxides without ruthenium doping, such as:

FeCoNiCuCe, FeCoNiCuMo, FeNiCuMoCe.

The performance tests of various high entropy oxides obtained from the above two groups of comparative tests were carried out: various high entropy oxides prepared with self-supporting materials such as carbon cloth and carbon paper as substrates can be directly used as working electrodes for electrochemical oxygen evolution performance tests, with Hg/HgO and graphite carbon rods as reference electrodes and counter electrodes respectively, and the electrolyte is 1M KOH. Cyclic voltammetry was used to activate the material until the CV curve was stable, and the number of activation cycles was 50-500. The experimental data curves of Ru-FeCoNiCuCe and FeCoNiCuCe are used as examples:

As shown in Figure 2, Figure 2 is a performance diagram of Ru-FeCoNiCuCe and FeCoNiCuCe loaded on carbon cloth in 1M KOH OER test, from left to right are LSV (linear sweep voltammetry) curve, Tafel slope (Tafel slope) curve; in 1M KOH electrolyte, the sweep rate is 5mV/s. From Figure 2, it can be seen that the overpotentials required for Ru-FeCoNiCuCe to achieve 10, 50 and 100mV cm ^-2 current densities are 279, 313 and 349mV respectively, and the Tafel slope is 66mV dec ^-1 ;

The overpotentials required for FeCoNiCuCe to achieve current densities of 10, 50 and 100 mV cm ^-2 are 279, 364 and 394 mV respectively, and the Tafel slope is 85 mV dec ^-1 .

As shown in Figure 3, Figure 3 is a performance diagram of Ru-FeCoNiCuCe and FeCoNiCuCe loaded on carbon cloth in 1M KOH for HER testing, from left to right are LSV curve and Tafel slope curve. In 1M KOH electrolyte, the scan rate is 5mV/s. From Figure 3, it can be seen that the overpotentials required for Ru-FeCoNiCuCe to achieve 10, 50 and 100mV cm ^-2 current densities are 148, 253 and 349mV respectively, and the Tafel slope is 153mV dec ^-1 ;

The overpotentials required for FeCoNiCuCe to achieve current densities of 10, 50 and 100 mV cm ^-2 are 279, 299 and 391 mV respectively, and the Tafel slope is 120 mV dec ^-1 .

As shown in Figure 4, Figure 4 is the LSV curve of Ru-FeCoNiCuCe and FeCoNiCuCe loaded on carbon cloth to test UOR in 1M KOH. In 1M KOH electrolyte, the scan rate is 5mV/s. From Figure 4, it can be seen that the voltages required for Ru-FeCoNiCuCe to achieve 10, 50 and 100mVcm ^-2 current densities are 1.439, 1.586 and 1.619V respectively; the voltages required for FeCoNiCuCe to achieve 10, 50 and 100mV cm ^-2 current densities are 1.44, 1.594 and 1.654V respectively.

The following is further explained by the experimental data of the above-mentioned ruthenium-doped high entropy oxides Ru-FeCoNiCuMo and Ru-FeNiCuMoCe with different molar ratios, which have better effects:

Figure 5 shows the performance of Ru-FeCoNiCu _0.35 Mo _0.75 loaded on carbon cloth in 1M KOH OER test, from left to right are LSV curve and Tafel slope curve. In 1M KOH electrolyte, the scan rate is 5mV/s. From Figure 5, it can be seen that the overpotentials required for Ru-FeCoNiCu _0.35 Mo _0.75 to achieve 10, 50 and 100mV cm ^-2 current densities are 290, 332 and 356mV respectively, and the Tafel slope is 57mV dec ^-1 .

Figure 6 shows the performance of Ru-FeCoNiCu _0.35 Mo _0.75 loaded on carbon cloth in 1M KOH test for HER, with LSV curve and Tafel slope curve from left to right. In 1M KOH electrolyte, the scan rate is 5mV/s. From Figure 6, it can be seen that the overpotentials required for Ru-FeCoNiCu _0.35 Mo _0.75 to achieve 10, 50 and 100mV cm ^-2 current densities are 198, 295 and 333mV respectively, and the Tafel slope is 153mV dec ^-1 .

Figure 7 is a performance diagram of Ru-FeNiCu _0.3 Mo _0.3 Ce _0.4 loaded on carbon cloth in 1M KOH OER test, from left to right are LSV curve and Tafel slope curve. In 1M KOH electrolyte, the scan rate is 5mV/s. From Figure 7, it can be seen that the overpotential required for Ru-FeNiCu _0.3 Mo _0.3 Ce _0.4 to achieve 10, 50 and 100mV cm ^-2 current density is 280, 318 and 339mV respectively, and the Tafel slope is 50mV dec ^-1 .

Figure 8 is a performance diagram of HER test of Ru-FeNiCu _0.3 Mo _0.3 Ce _0.4 loaded on carbon cloth in 1M KOH, from left to right are LSV curve and Tafel slope curve. In 1M KOH electrolyte, the scan rate is 5mV/s. From Figure 8, it can be seen that the overpotential required for Ru-FeNiCu _0.3 Mo _0.3 Ce _0.4 to achieve 10, 50 and 100mV cm ^-2 current density is 140, 246 and 311mV respectively, and the Tafel slope is 119mV dec ^-1 .

From the above experimental data, it can be seen that after the introduction of ruthenium doping, the overpotential required to achieve the same current density of the ruthenium-doped sample is lower, that is, the electrocatalytic activity is higher, and the Tafel slope value is lower, indicating that its electrochemical reaction kinetics is faster.

It should be noted that: using the preparation method of the present invention, the time required for preparing high entropy oxides doped with precious metals is extremely short. Taking the loading of ruthenium-doped high entropy oxides on a carbon cloth substrate as an example, the technical solution of this embodiment uses flash heating technology to prepare ruthenium-doped high entropy oxides on a self-supporting carbon substrate in a very short time. The time for preparing the material is only 400ms, while the time for preparing high entropy oxides by high-temperature solid-phase reaction is at least 2h. Flash heating technology can achieve rapid heating and quenching, and heteroatom-doped high entropy oxides can be formed in situ on different substrates; unlike existing technologies, the entire flash heating process is extremely short, with few steps and simple and easy operation; and no binder is required for performance testing of electrodes, which reduces costs while ensuring that the active sites are fully exposed. This method can not only be extended to different substrates, but transient high temperatures can also increase the mutual solubility of immiscible components, thereby broadening the range of component selection to suit different reaction scenarios.

The ruthenium-doped high-entropy oxide prepared by the preparation method of the present invention can achieve regulation of the electronic structure of the active site by adding doped ruthenium and selecting components with different electronegativity (the components include any 5 groups of 6 types of iron, nickel, cobalt, copper, molybdenum, and cerium) to activate its lattice oxygen to participate in the reaction; while triggering the lattice oxygen to participate in the reaction, the stability of the structure can be maintained, and the electrocatalytic activity and stability of the material are significantly improved.

The present invention provides a method for preparing an electrocatalytic material with high production efficiency, low cost and stable HER and OER dual functions. The preparation method can be applied to synthesize ruthenium-doped high entropy oxides (such as carbon paper, carbon cloth, biomass carbon, etc.) on a variety of different carbon substrates. The prepared high entropy oxides can be widely used in fuel cells, metal-air batteries and other scenarios.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims (10)

1. A method for preparing a ruthenium-doped high entropy oxide, comprising the following steps: A precursor solution is prepared using a metal chloride salt as a solute, wherein the metal chloride salt includes any five of the six types of ferric chloride, nickel chloride, cobalt chloride, copper chloride, cerium chloride, and molybdenum chloride, and also includes ruthenium chloride; Loading the precursor solution on a substrate and drying it; The substrate loaded with the precursor solution is flash-heat treated to obtain a ruthenium-doped high-entropy oxide. 2. The method for preparing ruthenium-doped high-entropy oxide according to claim 1 is characterized in that the precursor solution is prepared by ultrasonic dispersion method and has a concentration of 0.05 to 0.5 mol/L. 3. The method for preparing ruthenium-doped high entropy oxide according to claim 1, characterized in that the metal chloride salt comprises ferric chloride, cobalt chloride, nickel chloride, copper chloride and cerium chloride, and the molar ratio thereof is 1:1:1:1:1. 4. The method for preparing ruthenium-doped high entropy oxide according to claim 1, characterized in that the metal chloride salt comprises ferric chloride, cobalt chloride, nickel chloride, copper chloride and molybdenum chloride, and the molar ratio thereof is 1:1:1:0.35:0.75. 5. The method for preparing ruthenium-doped high entropy oxide according to claim 1, characterized in that the metal chloride salt comprises ferric chloride, nickel chloride, cupric chloride, molybdenum chloride and cerium chloride, and the molar ratio thereof is 1:1:0.3:0.3:0.4. 6. The method for preparing ruthenium-doped high entropy oxide according to claim 1, characterized in that the concentration of ruthenium chloride is 0.001 to 0.02 mol/L. 7. The method for preparing ruthenium-doped high-entropy oxide according to claim 1 is characterized in that the substrate comprises carbon cloth, carbon paper or biomass carbon; and the precursor solution is loaded on the substrate by immersion or dripping. 8. The method for preparing ruthenium-doped high entropy oxide according to claim 1, characterized in that the discharge voltage of the flash heat treatment is 60-120V and the discharge time is 50-1000ms. 9. A ruthenium-doped high entropy oxide, characterized in that it is prepared by the method described in any one of claims 1 to 9. 10. The ruthenium-doped high entropy oxide according to claim 9, characterized in that it is used as an electrocatalyst.