阅读说明：本技术 一种多元合金电极材料的制备方法 (Preparation method of multi-element alloy electrode material ) 是由 魏世忠 潘昆明 赵阳 夏梁彬 吴宏辉 徐流杰 张玢 于华 张程 陈冲 毛丰 周 于 2020-12-30 设计创作，主要内容包括：本发明涉及一种多元合金电极材料的制备方法,先将钼酸铵和柠檬酸溶解于水中,然后再向其中缓慢加入硫脲,充分搅拌后得到溶液体系,将该溶液体系置于水浴锅中进行水浴加热,加热过程中持续搅拌；当水浴中的溶液体系开始变浑浊时将称好的金属粉末倒入其中持续水浴加热并搅拌；当混合体系继续变为粘滞胶状物时将该胶状物取出并置于马弗炉中煅烧,得到前驱体粉末,将该前驱体粉末装入石墨模具中置入放电离子烧结炉进行烧结,最终得到多元合金电极材料。本发明步骤简单、原料成本低,过程可控,所得成品电极兼具稳定的催化活性和良好的导电性,一定程度上可以完成机械加工制成各种形状,并且有望实现规模化生产。(The invention relates to a preparation method of a multi-element alloy electrode material, which comprises the steps of dissolving ammonium molybdate and citric acid in water, then slowly adding thiourea into the solution, fully stirring to obtain a solution system, placing the solution system in a water bath kettle for water bath heating, and continuously stirring in the heating process; when the solution system in the water bath becomes turbid, pouring the weighed metal powder into the solution system, and continuously heating the solution system in the water bath and stirring the solution system; and when the mixed system is continuously changed into viscous jelly, taking out the jelly, placing the jelly in a muffle furnace for calcining to obtain precursor powder, placing the precursor powder into a graphite mold, placing the graphite mold into an electric ion sintering furnace for sintering, and finally obtaining the multi-element alloy electrode material. The method has the advantages of simple steps, low raw material cost and controllable process, and the obtained finished electrode has stable catalytic activity and good conductivity, can be machined into various shapes to a certain extent, and is expected to realize large-scale production.)

1. The preparation method of the multi-element alloy electrode material is characterized by comprising the following steps:

step one, weighing ammonium molybdate and citric acid, dissolving the ammonium molybdate and the citric acid in distilled water, stirring uniformly, slowly adding thiourea, and fully stirring until the solution is clear to obtain a solution system;

step two, placing the solution system obtained in the step one in a water bath kettle for water bath heating, and continuously stirring in the heating process;

step three, weighing metal powder, slowly pouring the metal powder into the solution system when the solution system in the water bath kettle in the step two becomes turbid, and continuously heating the obtained mixed system in a water bath and continuously stirring;

step four, after the mixed system obtained in the step three is changed into viscous jelly, taking out the viscous jelly, placing the viscous jelly into a muffle furnace for calcining, and obtaining precursor powder after calcining;

and step five, filling the precursor powder obtained in the step four into a graphite mold, placing the graphite mold into a discharge plasma sintering furnace for sintering treatment, and obtaining a final product, namely the multi-element alloy electrode material after sintering.

2. The method for preparing the multi-element alloy electrode material according to claim 1, wherein the method comprises the following steps: the concentration range of ammonium molybdate in the solution system obtained in the first step is 0.1-0.5 mol/L, the concentration range of citric acid is 4-12 mol/L, and the concentration range of thiourea is 1.5-7.5 mol/L.

3. The method for preparing the multi-element alloy electrode material according to claim 1, wherein the method comprises the following steps: and the temperature of the water bath heating in the second step is 90-100 ℃.

4. The method for preparing the multi-element alloy electrode material according to claim 1, wherein the method comprises the following steps: and step three, mixing the metal powder with two or more of nickel powder, molybdenum powder, tungsten powder and steel powder, wherein the ratio of the total mass of the metal powder to the mass of ammonium molybdate is 2-5: 1.

5. the method for preparing the multi-element alloy electrode material according to claim 1, wherein the method comprises the following steps: and the temperature of the four-step muffle furnace calcination is 500-600 ℃, and the calcination time is 4-8 h.

6. The method for preparing the multi-element alloy electrode material according to claim 1, wherein the method comprises the following steps: and the sintering temperature of the discharge plasma sintering furnace in the fifth step is 800-1800 ℃, and the heating rate is 50-100 ℃/min.

7. The method for preparing the multi-element alloy electrode material according to claim 1, wherein the method comprises the following steps: the obtained multi-element alloy electrode material is used for water decomposition to prepare hydrogen.

8. The method for preparing a multi-element alloy electrode material according to claims 1-6, wherein: other substances with catalytic properties are loaded on the metal substrate by the method to prepare the electrode material with catalytic properties.

9. The method for preparing the multi-element alloy electrode material according to claim 8, wherein the method comprises the following steps: other materials with catalytic properties are tungsten sulphide, nickel sulphide, cobalt sulphide.

Technical Field

The invention relates to the technical field of preparation of catalytic materials, in particular to a preparation method of a multi-element alloy electrode material, and belongs to a technical application of preparing catalytic materials by a powder metallurgy method.

Background

With the gradual shortage of petroleum resources and the increasing serious environmental pollution, people pay more attention to new clean and sustainable energy. Among them, hydrogen energy is considered to have a wide prospect. Unfortunately, at present, the industrial hydrogen production still uses fossil fuels such as coal and petroleum as main methods, such as coke oven gas (hydrogen gas 55-60%, methane 23-27%, carbon monoxide 6-8% and the like) which belongs to a by-product for preparing coke; for example, light oil reacts with water at high temperature to produce hydrogen. Obviously, this is not a sustainable route, contrary to the original intention of reducing fossil energy consumption fundamentally. The hydrogen production by catalytic water decomposition is an old and mature technology, and has unique advantages: 1. the process is simple, the operation is convenient, and the automation can be realized; 2. the prepared hydrogen product has high purity; 3. the product impurities are mainly H₂O and O₂And has no harm to the environment. In theory, water electrolysis can be carried out at a voltage exceeding 1.23V, but in practice, higher voltage is required for water decomposition due to the presence of overpotential in the hydrogen and oxygen generation reaction, electrolyte resistance, and internal resistance of the electronic circuit. The catalyst can effectively improve the slow reaction kinetics of HER and OER, reduce overpotential, further reduce energy consumption and improve efficiency. However, the existing high-efficiency catalyst is mainly a noble metal material, so that the large-batch industrial application of the high-efficiency catalyst is severely restricted, and the development of a low-cost non-noble metal catalyst has important significance.

The main problems of the research on non-noble metal catalysts at home and abroad can be summarized as follows: 1. the conductivity was poor. The catalyst prepared in the laboratory is mainly powder, lacks the current collector of electricity, hardly gives full play to the catalytic performance of the material. The obtained performance is only small-scale performance, but if the method is applied to engineering, the large-scale catalytic effect cannot be quantitatively calculated based on the small scale; 2. the scale is small. The catalyst prepared in the laboratory is mainly prepared in small batches, the process is fine and complex, the dominant phase such as 1T phase is slightly interfered by external conditions, but the stability of the catalyst in the engineering production is difficult to ensure; 3. the mechanical strength is poor. Although the research on the self-supporting electrode is available at present, the adopted carrier is a carbon material or a flexible conductive material, so that the mechanical strength is poor, the operation and the processing are not facilitated, and the carrier is not suitable for engineering production.

Disclosure of Invention

In order to solve the technical problems, the invention provides a preparation method of a multi-element alloy electrode material, and the prepared multi-element alloy electrode material has high catalytic activity, good conductivity, certain mechanical property and processability, can be used as a catalyst and a current collector, especially can be directly used as an electrode for catalyzing water decomposition, and has wide industrial production prospect in large scale.

The invention provides a preparation method of a multi-element alloy electrode material, which comprises the following steps:

step one, weighing ammonium molybdate and citric acid, dissolving the ammonium molybdate and the citric acid in distilled water, stirring uniformly, slowly adding thiourea, and fully stirring until the solution is clear to obtain a solution system;

step two, placing the solution system obtained in the step one in a water bath kettle for water bath heating, and continuously stirring in the heating process;

step three, weighing a certain amount of metal powder, slowly pouring the metal powder into the solution system when the solution system in the water bath kettle in the step two becomes turbid, and continuously heating the obtained mixed system in a water bath and continuously stirring;

step four, after the mixed system obtained in the step three is changed into viscous jelly, taking out the viscous jelly, placing the viscous jelly into a muffle furnace for calcining, and obtaining precursor powder after calcining;

and step five, filling the precursor powder obtained in the step four into a graphite mold, placing the graphite mold into a discharge plasma sintering furnace for sintering treatment, and obtaining a final product, namely the multi-element alloy electrode material after sintering.

Preferably, the concentration range of ammonium molybdate in the solution system obtained in the step one is 0.1-0.5 mol/L, the concentration range of citric acid is 4-12 mol/L, and the concentration range of thiourea is 1.5-7.5 mol/L.

Preferably, the temperature of the water bath heating in the second step is 90-100 ℃.

Preferably, the metal powder in the third step is a quantitative mixture of two or more of nickel powder, molybdenum powder, tungsten powder and steel powder, and the mass ratio of the total mass of the metal powder to the mass of ammonium molybdate is 2-5: 1.

preferably, the temperature of the four-muffle furnace calcination is 500-600 ℃, and the calcination time is 4-8 h.

Preferably, the sintering temperature of the fifth discharge plasma sintering furnace is 800-1800 ℃, and the heating rate is 50-100 ℃/min.

Further, the obtained multi-element alloy electrode material can be used for hydrogen production through water decomposition.

Furthermore, the main body of the catalytic phase of the obtained multi-element alloy electrode material is molybdenum disulfide, but the electrode material prepared by loading other substances with catalytic properties (such as tungsten sulfide, nickel sulfide, cobalt sulfide and the like) on a metal substrate by the method disclosed by the invention is in the protection scope of the patent.

The reaction principle of the invention is as follows: firstly, the molybdenum source and the sulfur source are complexed and gathered under the action of citric acid, solute is slowly separated out along with the loss of the solvent in the heating and stirring processes, at the moment, metal powder is added, nucleation sites can be provided for chemical reaction products, and finally, molybdenum disulfide is generated in situ on the surfaces of metal powder particles. The molybdenum disulfide generated in situ can be firmly attached to the surface of the metal particles under the gelling effect of the citric acid. The citric acid is evenly doped in the mixed powder after being carbonized in the calcining process, and lays a foundation for the porosity of the subsequent sintering product. In the sintering process, because different types of metals have different thermal diffusion coefficients, porous and loose metal plates are easily formed, and the catalytic phase molybdenum disulfide exists in the metal plates in a uniformly doped form.

According to the invention, in the preparation process, through temperature control, time control, concentration control, calcination process and the like, the obtained multi-element metal electrode plate has a porous and loose microstructure, so that more catalyst attachment sites can be provided, the contact area of the material and the electrolyte can be greatly increased, and the catalytic reaction can be carried out more fully. In addition, hydrogen and oxygen which are water decomposition products easily escape from the pores of the material, so that the catalytic efficiency of the material is further optimized.

Compared with the existing smelting method and solid-phase ball milling method, the preparation process of the invention has the advantages of lower cost, more convenient operation and stronger applicability. The prepared multi-element alloy electrode material has high catalytic activity, good conductivity and certain mechanical property and processability, can be used as a catalyst and a current collector, can be particularly directly used as an electrode for catalyzing water decomposition, and has wide industrial production prospect.

Drawings

FIG. 1 is a photograph of a sample of the multi-alloy electrode material prepared in example 1;

FIG. 2 is an SEM electron micrograph of the multi-element alloy electrode material prepared in example 2;

FIG. 3 is an SEM electron micrograph (ten thousand times magnified) of the multi-alloy electrode material prepared in example 2;

FIG. 4 is an SEM electron micrograph of the multi-element alloy electrode material prepared in example 3;

FIG. 5 is a graph showing the performance of the multi-element alloy electrode material prepared in example 3 in the electrocatalytic water decomposition.

Detailed Description

The technical solution of the present invention will be further explained and explained in detail with reference to the drawings and the specific embodiments.

A preparation method of a multi-element alloy electrode material mainly comprises the following steps:

step one, weighing a certain amount of ammonium molybdate and citric acid, pouring the ammonium molybdate and the citric acid into a beaker, adding water to dissolve the ammonium molybdate and the citric acid, slowly adding a certain amount of thiourea into the beaker after uniformly stirring, and fully stirring until the solution is clear to obtain a solution system.

The concentration range of ammonium molybdate in the solution system obtained by the method is 0.1-0.5 mol/L, the concentration range of citric acid is 4-12 mol/L, and the concentration range of thiourea is 1.5-7.5 mol/L. Based on the reaction principle of ammonium molybdate and thiourea: (NH)₄)₂Mo₄O₁₃+15CS(NH₂)₂+9H₂O＝4MoS₂+(NH₄)₂SO₄+6NH₄SCN+18NH₃+9CO₂

The amount and concentration of the raw materials need to be strictly controlled, and if the concentration and amount are too small, the formed catalytic phase is too small, which is not beneficial to improving the catalytic effect. On the contrary, too high a concentration of the raw material leads to rapid precipitation and massive stacking of the product catalyst, which is already agglomerated in a large amount before the in-situ reaction on the metal surface. The dosage (concentration) of the citric acid is empirical data obtained by a large number of repeated experiments, and if the dosage is too small, the citric acid is not easy to gel, and if the dosage is too large, the citric acid is difficult to stir, so that the metal powder and the catalyst are difficult to uniformly fuse.

And step two, placing the solution system obtained in the step one in a water bath kettle for water bath heating, and continuously stirring in the heating process.

The temperature of the water bath heating is 90-100 ℃. Experimental data show that metal powder can sink into a bottom layer after entering a solution system, the temperature is lower than 90 ℃, solute is slowly separated out, and at the moment, in-situ separation of solute colloid on the surfaces of metal particles is difficult to realize even if the solution system is stirred. The temperature is higher than 100 ℃, water in the water bath kettle can be boiled violently, great difficulty is caused to the operation, and water in the water bath kettle is easy to boil into a solution system, so that unnecessary impurities are introduced into the whole system.

And step three, selecting and weighing a certain amount of metal powder, slowly pouring the weighed metal powder into the solution system when the solution system in the water bath kettle becomes turbid, and continuously heating the obtained mixed system in a water bath and continuously stirring. The mass of the metal powder required can be estimated based on the shape, size, density of the metal powder and the component content of each metal required.

The method belongs to the mixing of solid powder in a liquid phase, metal powder is added when a solution is going to become turbid or begins to become turbid, the metal powder is deposited at the bottom and is difficult to disperse uniformly when the metal powder is added too early, and the system is gelatinized when the metal powder is added too late, so that the aim of in-situ precipitation of a solute cannot be fulfilled. The metal powder can be selected from two or more of nickel powder, molybdenum powder, tungsten powder and steel powder which are quantitatively mixed and are used as the main raw material body of the multi-element alloy electrode. The ratio of the total mass of the metal powder to the mass of the molybdenum salt is 2-5: 1, if the amount of the metal powder is too small, the sintered sample is easy to crack or pulverize, and the mechanical property is influenced, and if the amount of the metal powder is too large, the catalytic phase is difficult to be uniformly doped with the metal powder and is precipitated in situ.

And step four, after the mixed system obtained in the step three is changed into viscous jelly, taking out the viscous jelly, placing the viscous jelly into a muffle furnace for calcining, and obtaining precursor powder after calcining.

The muffle furnace has the calcining temperature of 500-600 ℃ and the calcining time of 4-8 h. Aims to carbonize the citric acid into powder and uniformly dope the citric acid into precursor powder. And simultaneously eliminating residual (possibly existing unreacted) reaction raw materials of ammonium molybdate and thiourea. And removing all free water and crystal water molecules in the powder.

And step five, filling the precursor powder obtained in the step four into a graphite mold with a proper inner diameter, putting the mold into a Spark Plasma Sintering furnace (SPS) for Sintering treatment, and obtaining a final product, namely the multi-element alloy electrode material after Sintering.

The graphite mold can be selected to fit according to the shape and size parameters of the desired electrode.

The SPS sintering temperature is 800-1800 ℃ and the heating rate is 50-100 ℃/min. The temperature and the heating rate need to be strictly controlled, if the temperature is too low, the forming degree is poor, and the pulverization is easy; if the temperature is too high, the density of the formed sample is high, and the sample has no porous structure, so that the adhesion and the function of the catalyst are not favorably exerted. Similarly, the rate of temperature increase also affects the size of the product pores.

Example 1:

(1) weighing 1.235g of ammonium molybdate and 7.69g of citric acid, pouring the ammonium molybdate and the citric acid into a beaker, adding water to dissolve the ammonium molybdate and the citric acid, stirring uniformly, then slowly adding 1.14g of thiourea, and fully stirring until the solution is clear to obtain a solution system.

(2) And (3) putting the solution system obtained in the step one into a water bath kettle for water bath heating, wherein the water bath heating temperature is 90 ℃, and continuously stirring in the heating process.

(3) And (3) weighing 1g of nickel powder and 2g of tungsten powder, slowly pouring the nickel powder and the tungsten powder into a solution system when the solution in the water bath kettle in the step (2) becomes turbid, and continuously heating the obtained mixed system in a water bath and continuously stirring.

(4) And (4) when the mixed system obtained in the step (3) is changed into viscous jelly, taking out the viscous jelly, placing the viscous jelly into a muffle furnace, calcining for 4 hours at the calcining temperature of 500 ℃, and calcining to obtain precursor powder.

(5) And (3) filling the precursor powder obtained in the step (4) into a graphite mold with the diameter phi of 20mm, and placing the graphite mold into a Spark Plasma Sintering furnace (SPS) for Sintering treatment, wherein the Sintering temperature is 800 ℃, and the heating rate is 50 ℃/min. And sintering to obtain the final product, namely the multi-element alloy electrode material.

The finished electrode plate prepared in this example was macroscopically characterized, and the results are shown in fig. 1. As can be seen from fig. 1: the product obtained in this example is in the form of black small discs having a diameter of 20mm and a thickness of 2 mm.

Example 2:

(1) weighing 1.235g of ammonium molybdate and 13g of citric acid, pouring the ammonium molybdate and the citric acid into a beaker, adding water to dissolve the ammonium molybdate and the citric acid, stirring uniformly, then slowly adding 3g of thiourea, and fully stirring until the solution is clear to obtain a solution system.

(2) And (3) putting the solution system obtained in the step one into a water bath kettle for water bath heating, wherein the water bath heating temperature is kept, and the solution system is continuously stirred in the heating process.

(3) Weighing 2g of nickel powder and 1g of DT300 steel powder, slowly pouring the nickel powder and the steel powder into the solution system when the solution in the water bath kettle in the step (2) becomes turbid, and continuously heating the obtained mixed system in a water bath and continuously stirring.

(4) And (4) when the mixed system obtained in the step (3) is changed into viscous jelly, taking out the viscous jelly, placing the viscous jelly into a muffle furnace, calcining for 6 hours at 550 ℃, and calcining to obtain precursor powder.

(5) And (3) filling the precursor powder obtained in the step (4) into a graphite mold with the diameter phi of 20mm, and placing the graphite mold into a Spark Plasma Sintering furnace (SPS) for Sintering treatment, wherein the Sintering temperature is 800 ℃, and the heating rate is 50 ℃/min. And sintering to obtain the final product, namely the multi-element alloy electrode material.

The finished electrode plate prepared in this example was subjected to microscopic characterization, and the results are shown in fig. 2 and fig. 3. As can be seen from fig. 2: the microscopic appearance of the product is that irregular particles are uniformly distributed on the surface of the substrate in an uneven way. As can be seen from fig. 3: after the product obtained in this example was enlarged by 1 ten thousand times, it was observed that flaky particulate matter (molybdenum disulfide) was included between irregular particles, and the flaky particulate matter (molybdenum disulfide) was well bonded to surrounding particles and a matrix.

Example 3:

(1) weighing 1.235g of ammonium molybdate and 10g of citric acid, pouring the ammonium molybdate and the citric acid into a beaker, adding water to dissolve the ammonium molybdate and the citric acid, stirring uniformly, then slowly adding 5g of thiourea, and fully stirring until the solution is clear to obtain a solution system.

(2) And (3) putting the solution system obtained in the step one into a water bath kettle for water bath heating, wherein the water bath heating temperature is 100 ℃, and continuously stirring in the heating process.

(3) Weighing 2g of molybdenum powder and 1g of DT300 steel powder, uniformly mixing, slowly pouring the mixed metal powder into a solution system when the solution in the water bath kettle in the step (2) becomes turbid, and continuously heating the obtained mixed system in a water bath and continuously stirring.

(4) And (4) after the mixed system obtained in the step (3) is changed into viscous jelly, taking out the viscous jelly, placing the viscous jelly into a muffle furnace, calcining for 8 hours at the calcining temperature of 600 ℃, and calcining to obtain precursor powder.

(5) And (3) filling the precursor powder obtained in the step (4) into a graphite mold with the diameter phi of 20mm, and placing the graphite mold into a Spark Plasma Sintering furnace (SPS) for Sintering treatment, wherein the Sintering temperature is 1500 ℃, and the heating rate is 50 ℃/min. And sintering to obtain the final product, namely the multi-element alloy electrode material.

The finished electrode plate prepared in this example was characterized by SEM electron micrographs, and the results are shown in fig. 4. As can be seen from fig. 4: after the product prepared by the embodiment is amplified by 2 thousand times, irregular large particles are uniformly distributed on the surface of the product, obvious small lamellar particles (molybdenum disulfide) are included in the irregular large lamellar particles, and the porous loose surface is combined with lamellar molybdenum disulfide particles with different growth orientations, so that the high catalytic activity of the product is laid.

In order to test the performance of the product prepared by the invention in water electrocatalytic decomposition, an electrochemical workstation can be adopted to demonstrate through an experiment of testing a hydrogen evolution polarization curve by three electrodes. The electrolyte used in the experiment is 1mol/L KOH solution, the obtained alloy electrode plate can be directly used as a working electrode, a graphite rod is used as a counter electrode, and a calomel electrode is used as a reference electrode. And setting a voltage scanning interval to be-1.4-0V to obtain a polarization curve. The results are shown in FIG. 5. As can be seen from fig. 5: the starting potential of the hydrogen evolution catalytic reaction of the finished alloy electrode plate is eta 10-136 mV, and the current density is large. The material has excellent electrocatalytic hydrogen evolution performance.

The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention in any way, and any simple modification, equivalent change and modification made by those skilled in the art according to the technical spirit of the present invention are still within the technical scope of the present invention without departing from the technical scope of the present invention.