阅读说明：本技术 三元铁镍钼基复合材料电解水催化剂、其制备方法和应用 (Ternary iron-nickel-molybdenum-based composite material water electrolysis catalyst, and preparation method and application thereof ) 是由 李东阳 周海青 蔡凤明 廖礼玲 余芳 于 2021-06-24 设计创作，主要内容包括：本发明公开了一种三元铁镍钼基复合材料电解水催化剂、其制备方法和应用,将导电基底置于水热反应前驱体溶液中进行水热反应,得到NiMoO-(4)纳米阵列基底；将NiMoO-(4)纳米阵列基底浸泡于含Fe～(3+)离子的溶液中然后晾干；将浸泡后的NiMoO-(4)纳米阵列基底进行高温还原反应,得到三元铁镍钼基复合材料催化剂Fe/MoNi-(4)/MoO-(2)。在碱性环境中表现出非常优异的电催化活性和稳定性。纳米结构极大的暴露材料的电化学活性位点,加快氢离子吸附和氢原子脱附,增加水解过程中的能量转化效率。同时,铁元素的修饰改善了MoNi-(4)/MoO-(2)材料的析氧反应催化活性和稳定性,有效的降低析氧反应的过电位,从而降低电解水工艺的成本。(The invention discloses a ternary iron-nickel-molybdenum-based composite material water electrolysis catalyst, a preparation method and application thereof 4 A nano-array substrate; mixing NiMoO 4 Soaking the nano-array substrate in Fe-containing solution 3+ The ionic solution is dried; soaking the NiMoO 4 Performing high-temperature reduction reaction on the nano array substrate to obtain the ternary Fe-Ni-Mo-based composite material catalyst Fe/MoNi 4 /MoO 2 . The catalyst shows excellent electrocatalytic activity and stability in alkaline environment. The nanostructure greatly exposes the electrochemical active site of the material, accelerates hydrogen ion adsorption and hydrogen atom desorption, and increases the energy conversion efficiency in the hydrolysis process. Meanwhile, the modification of the iron element improves MoNi 4 /MoO 2 The catalytic activity and stability of the oxygen evolution reaction of the material effectively reduce the overpotential of the oxygen evolution reaction, thereby reducing the cost of the water electrolysis process.)

1. A preparation method of a ternary iron-nickel-molybdenum-based composite material water electrolysis catalyst is characterized by comprising the following steps:

placing the conductive substrate in a hydrothermal reaction precursor solution for hydrothermal reaction to obtain NiMoO₄A nano-array substrate;

mixing NiMoO₄Soaking the nano-array substrate in Fe-containing solution³⁺The ionic solution is dried;

soaking the NiMoO₄Performing high-temperature reduction reaction on the nano array substrate to obtain the ternary Fe-Ni-Mo-based composite material water electrolysis catalyst Fe/MoNi₄/MoO₂。

2. The method for preparing the ternary iron-nickel-molybdenum-based composite material water electrolysis catalyst according to claim 1, wherein the conductive substrate is foamed nickel or a porous conductive material.

3. The method for preparing the ternary iron-nickel-molybdenum-based composite material electrolytic water catalyst according to claim 1, wherein the hydrothermal reaction precursor solution contains Ni²⁺And Mo₇O₂₄ ^6-。

4. The preparation method of the ternary iron-nickel-molybdenum-based composite material electrolytic water catalyst according to claim 1 or 3, wherein the hydrothermal reaction temperature is 120-180 ℃ and the time is 4-8 hours.

5. The method for preparing the ternary Fe-Ni-Mo based composite material water electrolysis catalyst of claim 3, wherein Fe³⁺And Ni²⁺In a molar ratio of 8: 1-9: 1.

6. the method for preparing a ternary iron-nickel-molybdenum-based composite material water electrolysis catalyst according to claim 1, wherein the high-temperature reduction reaction is carried out in a mixed gas of an inert gas and hydrogen.

7. The preparation method of the ternary iron-nickel-molybdenum-based composite material water electrolysis catalyst according to claim 1 or 6, wherein the high-temperature reduction reaction temperature is 375-425 ℃ and the time is 1-3 h.

8. The preparation method of the ternary iron-nickel-molybdenum-based composite material water electrolysis catalyst according to claim 7, wherein the temperature rise rate of the high-temperature reduction reaction is 3-5 ℃/min.

9. A ternary Fe-Ni-Mo based composite material water electrolysis catalyst prepared by the method of any one of claims 1-8, which is grown on a conductive substrate and has a chemical composition expressed as Fe/MoNi₄/MoO₂The molar ratio of Fe to Ni is 1: 2.5-1: 3.5, the micro morphology is in MoNi₄/MoO₂Fe nano-particles are grown on the surfaces of the nano-rods.

10. The application of the ternary iron-nickel-molybdenum-based composite material electrolytic water catalyst prepared by the method of any one of claims 1 to 8 is characterized in that the ternary iron-nickel-molybdenum-based composite material electrolytic water catalyst is applied to electrolytic water hydrogen evolution reaction and/or oxygen evolution reaction in an alkaline environment.

Technical Field

The invention belongs to the technical field of hydrogen production by water electrolysis and new energy, and particularly relates to a ternary iron-nickel-molybdenum-based composite material bifunctional water electrolysis catalyst, a preparation method thereof and application thereof in the field of hydrogen production by water electrolysis.

Background

The current global environmental and energy issues are receiving much attention. Hydrogen energy is considered to be the most promising clean energy source because of its clean, environmental friendly, easy storage, and renewable nature. The methane reforming process, the water gas process and the electrolytic water process are the hydrogen production processes that are mainly used in industry. The method for preparing hydrogen by using electrolytic water is undoubtedly the most ideal way following the concept of cleanness, environmental protection and sustainability.

The electrolytic water technology can be classified into acid electrolytic water and alkaline electrolytic water according to the difference of electrolytes. Compared with alkaline electrolyzed water, the reaction rate of acidic electrolyzed water is 2 to 3 orders of magnitude higher, the byproducts are less, and the method is more favored by industrial production. However, the proton exchange membrane necessary for electrolysis in an acidic environment is not only expensive, but also generates a high-acidity environment, and a large amount of noble metal materials such as platinum and iridium are required to be used as catalysts, so that the production cost is greatly increased. The research on the hydrogen production process by alkaline electrolysis of water is very thorough, and the traditional alkaline electrolysis technology uses a potassium hydroxide solution as an electrolyte, transmits hydroxide ions through a porous membrane, and separates two half cells to effectively improve the rate of water decomposition and reduce byproducts. Because of different chemical environments of alkaline electrolysis, transition metal materials such as nickel, cobalt, iron and the like can be used for replacing expensive platinum catalysts, and the production cost is effectively reduced. The metallic nickel is abundant in resource, commercial foam nickel can effectively reduce the cost when being used as a catalyst for hydrolysis, but the catalytic performance of the commercial foam nickel is far lower than that of noble metal, and particularly when being used as an anode catalyst to participate in oxygen evolution reaction, the commercial foam nickel can generate large overpotential so as to reduce the energy conversion rate during water decomposition, and the overpotential is also a main bottleneck for restricting the development of an alkaline water decomposition hydrogen production technology.

The nickel atom is an excellent water cracking center, the molybdenum atom has good adsorption capacity to hydrogen, and the hydrogen evolution performance of the nickel-molybdenum metal material is generally very excellent, but the performance of the nickel-molybdenum metal material as an oxygen evolution catalyst is not ideal, so that the overpotential of the whole hydrolysis reaction is too high. A large number of researches show that the electrochemical activity of the material can be effectively improved by chemical methods such as morphology regulation, defect manufacturing, electronic structure optimization and the like.

Disclosure of Invention

The invention aims to solve the technical problem of overcoming the defects and shortcomings in the background technology and provides a ternary iron-nickel-molybdenum-based composite material water electrolysis catalyst, a preparation method and application thereof, so that the overpotential in an alkaline environment is reduced and the catalytic activity is improved.

In order to solve the technical problems, the technical scheme provided by the invention is as follows:

a preparation method of a ternary iron-nickel-molybdenum-based composite material water electrolysis catalyst comprises the following steps:

placing the conductive substrate in a hydrothermal reaction precursor solution for hydrothermal reaction to obtain NiMoO₄A nano-array substrate;

mixing NiMoO₄Soaking the nano-array substrate in Fe-containing solution³⁺The ionic solution is dried;

soaking the NiMoO₄Performing high-temperature reduction reaction on the nano array substrate to obtain the ternary Fe-Ni-Mo-based composite material catalyst Fe/MoNi₄/MoO₂。

Further, the conductive substrate is foamed nickel or a porous conductive material.

Further, the hydrothermal reaction precursor solution contains Ni²⁺And Mo₇O₂₄ ^6-。

Furthermore, the hydrothermal reaction temperature is 120-180 ℃ and the time is 4-8 hours.

Further, Fe³⁺And Ni²⁺In a molar ratio of 8: 1-9: 1.

further, the high-temperature reduction reaction is carried out in a mixed gas of an inert gas and hydrogen.

Furthermore, the high-temperature reduction reaction temperature is 375-425 ℃, and the time is 1-3 h.

Further, the heating rate of the high-temperature reduction reaction is 3-5 ℃/min.

The invention provides a ternary iron-nickel-molybdenum-based composite material water electrolysis catalyst which is prepared by the method and grows on a conductive substrate, and the chemical composition of the ternary iron-nickel-molybdenum-based composite material water electrolysis catalyst is expressed as Fe/MoNi₄/MoO₂The molar ratio of Fe to Ni is 1: 2.5-1: 3.5, the micro morphology is in MoNi₄/MoO₂Fe nano-particles are grown on the surfaces of the nano-rods.

The application of the ternary iron-nickel-molybdenum-based composite material electrolytic water catalyst prepared by the method provided by the invention is applied to electrolytic water hydrogen evolution reaction and/or oxygen evolution reaction in an alkaline environment.

The invention aims at the nickel-molybdenum material MoNi₄/MoO₂The nanometer array has the defects of poor oxygen evolution performance, instability and the like, and a strategy for improving the oxygen evolution performance of the nanometer array by modifying iron element in situ, namely Fe/MoNi is designed₄/MoO₂The main catalytic mechanism is from the growth on MoNi after iron modification₄/MoO₂The nano-particles on the nano-rods improve the performance and the stability of the material in the oxygen evolution reaction. Mixing Fe/MoNi₄/MoO₂The nano materials are respectively used as cathode and anode catalysts to build an alkaline electrolytic cell, so that the conversion efficiency of water electrolysis for hydrogen production can be effectively improved, and energy in other forms is converted into hydrogen energy to be stored.

Specifically, compared with the prior art, the invention has the beneficial effects that:

1. Fe/MoNi prepared by high-temperature reduction method₄/MoO₂Shows very excellent HER and OER catalytic activity in alkaline environment, and only requires overpotentials of 69mV and 285mV respectively to reach current density of 500mA/cm²The formed full-hydrolytic device generates 500mA/cm under the voltage of 1.581V²Current ofDensity. The superior performance benefits from the nanostructure of the material providing a large number of active sites for hydrogen ion adsorption and hydrogen atom desorption. The conductive substrate is combined with the nano structure, so that the conductivity of the material is effectively improved, the electron transfer resistance is reduced, the effective transfer of charges and ions is accelerated, and the overpotential generated in the reaction process is greatly reduced.

2. The invention is based on a dual-functional water electrolysis catalyst of ternary Fe-Ni-Mo based composite material, which is prepared by adding MoNi₄Modified with Fe element in MoNi₄/MoO₂A large amount of Fe nano particles grow on the surface of the nano rod, more active sites are provided for the oxygen evolution reaction, and the overpotential of the oxygen evolution reaction is effectively reduced.

3. The invention is based on a ternary iron-nickel-molybdenum-based composite material bifunctional electrolytic water catalyst, the preparation method is simple and controllable, the raw materials are low in price and rich in resources, and the preparation method is suitable for large-size batch preparation.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 shows Fe/MoNi at the beginning and after 250 CV cycles in example 1 of the present invention₄/MoO₂The current-potential polarization curve diagram of the hydrogen evolution reaction of the composite catalyst in an alkaline 1M KOH solution.

Fig. 2 is a graph of electrochemical stability testing of the catalyst material as a cathode catalyst in an alkaline electrolyte.

FIG. 3 shows Fe/MoNi at the beginning and after 500 CV cycles in example 1 of the present invention₄/MoO₂Current-potential polarization curve diagram of oxygen evolution reaction of the composite catalyst in alkaline 1M KOH solution.

Fig. 4 is a graph of electrochemical stability testing of the catalyst material as an anode catalyst in an alkaline electrolyte.

FIG. 5 is a graph of current-potential polarization for a perhydrolysis device made of the catalyst material of example 1 of the present invention in a 1M KOH solution initially and after 250 CV cycles.

Fig. 6 is a test curve of electrochemical stability of a perhydrolysis device in an alkaline electrolyte.

FIG. 7 is a surface topography of the catalyst material in example 1 of the present invention. The left and right images represent high and low power electron micrographs, respectively.

FIG. 8 shows Fe/MoNi in example 1 of the present invention₄/MoO₂The X-ray diffraction pattern of the composite material catalyst is obtained to obtain the main components of the catalyst.

FIG. 9 shows Fe/MoNi₄/MoO₂MoNi of catalyst and unmodified iron element₄/MoO₂HER catalyst performance comparisons.

FIG. 10 shows Fe/MoNi₄/MoO₂MoNi of catalyst and unmodified iron element₄/MoO₂And (5) comparing the performances of the catalysts.

FIG. 11 shows Fe/MoNi₄/MoO₂Full water decomposing device and MoNi₄/MoO₂And comparing the performances of the full water-decomposing device.

Detailed Description

In order to facilitate understanding of the invention, the invention will be described more fully and in detail with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

The preparation method of the ternary iron-nickel-molybdenum-based composite material water electrolysis catalyst in one specific embodiment of the invention comprises the following steps:

(1) adding proper amount of Ni (NO)₃)₂·6H₂O and (NH)₄)₆Mo₇O₂₄·4H₂Dissolving O in water to obtain a hydrothermal reaction precursor solution. Carrying out hydrothermal reaction on the cut conductive substrate (such as a foamed nickel substrate or a porous conductive material) and the precursor solution to obtain NiMoO₄A nanoarray substrate. Preferably, the hydrothermal reaction is carried out at a temperature of 120 to 180 ℃ and heated for 4 to 8 hours.

(2) Adding proper amount of Fe (NO)₃)₃·9H₂Dissolving O powder in solvent such as anhydrous ethanol, DMF, and water to obtain precursor solution, and mixing with NiMoO₄The substrate is soaked in the precursor solution for a few seconds and then dried.

Preferably, Fe (NO)₃)₃·9H₂O and Ni (NO)₃)₂·6H₂The molar ratio of O is 8: 1-9: 1. Fe/MoNi₄/MoO₂The modification amount of the Fe is as follows: the molar ratio of Fe to Ni is 1: 2.5-1: 3.5.

(3) the NiMoO soaked in the precursor solution is treated₄And carrying out high-temperature reduction reaction on the substrate, and cooling to room temperature after heating to obtain the ternary iron-nickel-molybdenum-based composite material catalyst. Preferably, the high temperature treatment uses a mixed gas of an inert gas (e.g., high purity argon) and hydrogen as a carrier gas and a shielding gas. Preferably, the high-temperature reduction reaction temperature is 375-425 ℃, and the constant temperature is kept for 1-3 hours. Preferably, the heating rate is 3-5 ℃/min. The step is that after iron modification, the iron is reduced under reducing gas, and elemental iron nano particles, NiMoO, are generated on the surface₄Is reduced into MoNi_4/MoO₂。

The invention is realized by adding MoNi₄/MoO₂Modifying iron element to obtain the tri-metal water electrolysis bifunctional catalyst Fe/MoNi with the nano array structure₄/MoO₂。

The invention discloses a preparation method of a ternary Fe-Ni-Mo-based composite catalyst based on elementary metal nickel foam or primary growth on the surface of a porous conductive material, and the application of the ternary Fe-Ni-Mo-based composite catalyst in the Hydrogen Evolution Reaction (HER) and the Oxygen Evolution Reaction (OER) of electrolysis water under an alkaline environment, which show excellent electrocatalysisActivity and stability. The catalyst obtained through a series of chemical processes such as hydrothermal reaction, vacuum reduction reaction and the like shows excellent electrocatalytic activity in alkaline electrolyte. For example, the ternary iron-nickel-molybdenum-based composite material catalyst synthesized by the invention greatly reduces the overpotential of the hydrolysis reaction. In an alkaline environment, only 69mV is needed as a cathode catalyst to reach 500mA/cm²Current density of up to 500mA/cm as anode catalyst²The current density also only generates an overpotential of 285mV (actual overpotential for oxygen evolution-1.23V), using Fe/MoNi₄/MoO₂The full-hydrolytic device consisting of the cathode catalyst and the anode catalyst which are respectively used for the hydrolysis reaction can generate 500mA/cm at the potential of 1.581V²The performance of the current density is superior to that of most non-noble metal electrolytic water catalysts.

The nanostructure is extremely large, and exposes the electrochemical active site (iron atom is used as the oxygen evolution active site of the material) of the material, so that hydrogen ion adsorption and hydrogen atom desorption are accelerated, and the energy conversion efficiency in the hydrolysis process is increased. Meanwhile, the modification of the iron element improves MoNi₄/MoO₂The catalytic activity and stability of the material in the oxygen evolution reaction effectively reduce the overpotential of the oxygen evolution reaction, thereby reducing the cost of the water electrolysis process and assisting the development of the hydrogen energy industry.

The electrocatalyst Fe/MoNi of the invention₄/MoO₂The nano material shows excellent hydrogen evolution and oxygen evolution activity under the alkaline environment and has the high current density of 300mA/cm²、1A/cm²Even 2A/cm²The stability and the corrosion resistance are kept for a long time.

Example 1

This example relates to Fe/MoNi₄/MoO₂The preparation of the trimetal composite material water electrolysis bifunctional catalyst and the performance test of the electrocatalytic hydrogen evolution, oxygen evolution and full water decomposition device in a 1M KOH environment.

Step 1: and cutting the foam nickel substrate, wherein the cutting area is 5cm long by 2cm wide.

Step 2: 0.2326g of Ni (NO)₃)₂·6H₂O and 0.2472g (NH)₄)₆Mo₇O₂₄·4H₂Dissolving O in 20ml deionized water, performing ultrasonic treatment for 15 minutes to obtain a hydrothermal reaction precursor solution, transferring the cut foam nickel substrate and the precursor solution into a reaction kettle, heating the reaction kettle in a drying box at the temperature of 150 ℃ for 6 hours, taking out a sample after the reaction kettle is cooled, cleaning the sample with the deionized water, and naturally airing the sample in a fume hood to obtain NiMoO₄A nanoarray substrate. The prepared NiMoO is added₄The nanoarray substrate was cut into rectangles 20mm long by 5mm wide.

And step 3: 1g of Fe (NO)₃)₃·9H₂Dissolving O powder in 5ml of alcohol solution, performing ultrasonic treatment for 15 minutes to obtain a precursor solution, and then preparing the prepared NiMoO₄The substrate was soaked in the precursor solution for a few seconds and then allowed to air dry naturally in a fume hood.

And 4, step 4: the NiMoO of the precursor solution soaked in the step 3 is treated₄The substrate is placed at the central position of the temperature zone of the double-temperature zone tubular furnace, and the mixed gas of high-purity argon and hydrogen is used as a carrier gas and a protective gas (Ar and H)₂The flow rates are respectively 92 sccm and 8sccm), the temperature of the temperature zone is set to be 400 ℃, the heating rate is 3 ℃/min, the temperature is kept for 2h, and the temperature is rapidly reduced to the room temperature after the heating is finished, so that the ternary iron-nickel-molybdenum-based composite material water electrolysis bifunctional catalyst is obtained.

The electrocatalytic hydrogen and oxygen evolution performance test mainly adopts an American GARY Reference 3000 electrochemical workstation and adopts a standard three-electrode system (a working electrode, a counter electrode and a Reference electrode) for testing. In alkaline environment, the three-electrode system has Fe/MoNi₄/MoO₂As a working electrode, an Hg/HgO electrode imported by Gamry manufacturers is used as a reference electrode, a graphite rod is used as a counter electrode, a 1M KOH solution is used as an electrolyte solution, and the results of electrocatalytic performance test are shown in figures 1, 2, 3 and 4. Under alkaline environment, Fe/MoNi₄/MoO₂Respectively used as cathode and anode catalysts to form Fe/MoNi₄/MoO₂The electrocatalytic performance test results of the total hydrolysis device are shown in FIGS. 5 and 6, and the Fe/MoNi₄/MoO₂The morphology is shown in FIG. 7, Fe/MoNi₄/MoO₂The main components of the composition are shown in figure 8.

From FIG. 7 can be seenIs in MoNi₄/MoO₂A large number of nano particles grow on the surface of the nano rod, and more active sites are provided for oxygen evolution reaction.

As can be seen from FIGS. 1, 3 and 5, Fe/MoNi prepared in the above examples₄/MoO₂Shows very excellent HER and OER catalytic activity in alkaline environment, and only requires overpotentials of 69mV and 285mV respectively to reach current density of 500mA/cm²The formed full-hydrolytic device generates 500mA/cm at the potential of 1.581V²The current density of (1).

From FIG. 2, it can be seen that the catalyst has a current density of 50mA/cm²And a large current of 500mA/cm²Has good stability. From FIG. 4, it can be seen that the catalyst has a current density of 50mA/cm²And a large current of 500mA/cm²Showing very excellent stability. From FIG. 6, it can be seen that the device is operated at a current density of 100mA/cm²、300mA/cm²、1000mA/cm²、2000mA/cm²Can maintain stability for at least 60 hr.

As can be seen from fig. 9, the modification of iron does not affect the HER activity of the material. As can be seen from fig. 10, the modification of the iron element greatly improves the OER performance of the material. As can be seen from FIG. 11, the modified iron element can improve the performance of the full-hydrolytic device. In which MoNi of the unmodified iron element is present₄/MoO₂Step 3 was omitted compared to example 1.

The foregoing is considered as illustrative of the preferred embodiments of the invention and is not to be construed as limiting the invention in any way. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention should fall within the protection scope of the technical scheme of the present invention, unless the technical spirit of the present invention departs from the content of the technical scheme of the present invention.