阅读说明：本技术 三维氮掺杂的花型碳球负载超细氮掺杂碳化钼纳米粒子及制备方法和应用 (Three-dimensional nitrogen-doped flower-shaped carbon sphere loaded superfine nitrogen-doped molybdenum carbide nano particle, and preparation method and application thereof ) 是由 陈锡安 王佳慧 魏会方 于 2019-09-30 设计创作，主要内容包括：本发明公开了一种三维氮掺杂的花型碳球负载超细氮掺杂碳化钼纳米粒子及制备方法和,其技术方案主要为包括以下步骤：(1)将表面活性剂和花型碳球溶于水中超声分散,向其中加入钼酸盐超声分散至溶解；(2)将步骤(1)的混合溶液转入反应釜中,水热反应,然后抽滤洗涤烘干,在惰性气体氛围下高温退火处理,得到三维氮掺杂花型碳球负载超细氮掺杂碳化钼纳米粒子。这种设计结构具有超细纳米粒子、三维氮掺杂花状碳骨架、氮同时掺杂到碳化钼和碳骨架中,有利于催化位点暴露、快速传质、电子结构的优化,从而有效提升电催化剂催化析氢性能。(The invention discloses a three-dimensional nitrogen-doped flower-shaped carbon sphere loaded superfine nitrogen-doped molybdenum carbide nano particle and a preparation method thereof, and the technical scheme mainly comprises the following steps: (1) dissolving a surfactant and a flower-shaped carbon sphere in water for ultrasonic dispersion, and adding molybdate into the water for ultrasonic dispersion until the molybdate is dissolved; (2) and (2) transferring the mixed solution obtained in the step (1) into a reaction kettle, carrying out hydrothermal reaction, then carrying out suction filtration, washing and drying, and carrying out high-temperature annealing treatment in an inert gas atmosphere to obtain the three-dimensional nitrogen-doped flower-shaped carbon sphere loaded superfine nitrogen-doped molybdenum carbide nano particles. The designed structure has ultrafine nano particles, a three-dimensional nitrogen-doped flower-shaped carbon framework and nitrogen doped into molybdenum carbide and the carbon framework simultaneously, and is beneficial to exposure of catalytic sites, rapid mass transfer and optimization of electronic structures, so that the catalytic hydrogen evolution performance of the electrocatalyst is effectively improved.)

1. A preparation method of superfine nitrogen-doped molybdenum carbide nano particles loaded on three-dimensional nitrogen-doped flower-shaped carbon spheres is characterized by comprising the following steps:

(1) dissolving a surfactant and a flower-shaped carbon sphere in water for ultrasonic dispersion, and adding molybdate into the water for ultrasonic dispersion until the molybdate is dissolved;

(2) and (2) transferring the mixed solution obtained in the step (1) into a reaction kettle, carrying out hydrothermal reaction, then carrying out suction filtration, washing and drying, and carrying out high-temperature annealing treatment in an inert gas atmosphere to obtain the three-dimensional nitrogen-doped flower-shaped carbon sphere loaded superfine nitrogen-doped molybdenum carbide nano particles.

2. The preparation method of the three-dimensional nitrogen-doped flower-shaped carbon sphere-loaded ultrafine nitrogen-doped molybdenum carbide nanoparticles according to claim 1, which is characterized by comprising the following steps: the mass ratio of the surfactant to the molybdate to the flower-shaped carbon spheres in the step (1) is 1:3-1:2 and 1.5:1-3.5:1 respectively.

3. The preparation method of the three-dimensional nitrogen-doped flower-shaped carbon sphere-loaded superfine nitrogen-doped molybdenum carbide nano-particles according to claim 1, which is characterized by comprising the following steps: in the step (1), the molybdate is one or a combination of ammonium molybdate, sodium molybdate and potassium molybdate.

4. The preparation method of the three-dimensional nitrogen-doped flower-shaped carbon sphere-loaded superfine nitrogen-doped molybdenum carbide nano-particles according to claim 1, which is characterized by comprising the following steps: the ultrasonic dispersion time in the step (1) is 30-60 min.

5. The preparation method of the three-dimensional nitrogen-doped flower-shaped carbon sphere-loaded superfine nitrogen-doped molybdenum carbide nano-particles according to claim 1, which is characterized by comprising the following steps: and (3) in the step (2), the drying temperature is 60-120 ℃, and the drying time is 8-12 h.

6. The preparation method of the three-dimensional nitrogen-doped flower-shaped carbon sphere-loaded superfine nitrogen-doped molybdenum carbide nano-particles according to claim 1, which is characterized by comprising the following steps: in the step (2), the inert gas is a mixed gas of argon and ammonia, and the volume ratio of the ammonia is 5-15%.

7. The preparation method of the three-dimensional nitrogen-doped flower-shaped carbon sphere-loaded superfine nitrogen-doped molybdenum carbide nano-particles according to claim 1, which is characterized by comprising the following steps: in the step (2), the annealing temperature is 700-1000 ℃, the heating rate is 1-5 ℃/min, and the heat preservation time is 1-3 h.

8. The ultrafine nitrogen-doped molybdenum carbide nano-particles loaded on the three-dimensional nitrogen-doped flower-shaped carbon spheres prepared by the preparation method of any one of claims 1 to 7.

9. The application of the three-dimensional nitrogen-doped flower-shaped carbon sphere-supported ultrafine nitrogen-doped molybdenum carbide nanoparticles as claimed in claim 8 in an electrocatalyst for hydrogen evolution by water electrolysis.

Technical Field

The invention belongs to the field of catalytic materials, particularly belongs to the field of catalysts for hydrogen production by water electrolysis, and particularly relates to a three-dimensional nitrogen-doped flower-shaped carbon sphere loaded ultrafine nitrogen-doped molybdenum carbide nanoparticle electrocatalyst, a preparation method thereof and application thereof in hydrogen production by water electrolysis under an acidic condition.

Background

With the progress of the times, the consumption of a large amount of fossil fuels and the brought environmental problems, we are forced to seek a clean renewable energy source to replace the fossil fuels. Thus, the development of efficient clean sustainable hydrogen energy technologies has attracted increasing attention. Electrocatalytic cracking of water is one of the most efficient methods for producing hydrogen. Currently, platinum-based materials are the most effective hydrogen evolution electrocatalysts (HER), but their low abundance, high cost, poor durability, limit their large-scale application. Therefore, exploring an electrocatalyst with high efficiency and low cost to reduce energy consumption and improve HER efficiency, such as non-noble metal HER catalysts of cobalt, nickel, iron, tungsten, molybdenum-based materials, etc., has attracted great research interest.

So far, the electrocatalytic performance of Pt/C is the best and the stability is good. But Pt is not available on a large scale because of its small abundance on the earth and high price. The search for inexpensive and efficient non-platinum catalysts has become a focus of research for the scientists in the time. Among these catalysts, molybdenum carbide is considered a new class of HER electrocatalysts due to its platinum-like d-orbital. In the past decade, transition metal carbides, sulphides etc. have been reported as highly efficient electrocatalysts, especially transition metal carbides, such as molybdenum carbide (j. mater. chem.a,2017,5,4879), have significant catalytic activity due to its own unique electronic structure and platinoid properties. However, Mo obtained at high temperatures₂C will usually inevitably aggregate, resulting in less exposed active sites. In addition, the stronger Mo-H bond strength limits desorption of adsorbed H (hads) to H₂. These problems affect Mo₂Performance of C-based electrocatalysts. To overcome these disadvantages, reduction of nanocrystalline size or optimization of Mo is being carried out₂More effort has been made in the electronic structure of C. But molybdenum carbide also has many challenges as an electrocatalyst, such as low transmission efficiency of electrons and charges, high Mo-H bond energy which is not beneficial to hydrogen precipitation, easy agglomeration at high temperature and the like.

Disclosure of Invention

In order to solve the problems and the defects in the prior art, the first object of the invention is to provide a three-dimensional nitrogen-doped flower-shaped carbon sphere-loaded ultrafine nitrogen-doped molybdenum carbide nanoparticle electrocatalyst.

A second object of the present invention is to provide a method for preparing the above electrocatalyst.

The third purpose of the invention is to provide an application of the electrocatalyst in water electrolysis hydrogen production.

In order to achieve the first object of the invention, the technical scheme of the invention comprises the following steps:

(1) dissolving a surfactant and a flower-shaped carbon sphere in water for ultrasonic dispersion, and adding molybdate into the water for ultrasonic dispersion until the molybdate is dissolved;

(2) and (2) transferring the mixed solution obtained in the step (1) into a reaction kettle, carrying out hydrothermal reaction, then carrying out suction filtration, washing and drying, and carrying out high-temperature annealing treatment in an inert gas atmosphere to obtain the three-dimensional nitrogen-doped flower-shaped carbon sphere loaded superfine nitrogen-doped molybdenum carbide nano particles.

Further setting the mass ratio of the surfactant to the molybdate and the flower-shaped carbon spheres in the step (1)

1:3-1:2 and 1.5:1-3.5:1 respectively.

The molybdate in the step (1) is further set to be one or a combination of more of ammonium molybdate, sodium molybdate and potassium molybdate.

Further setting the ultrasonic dispersion time in the step (1) to be 30-60 min.

Further setting that the drying temperature in the step (2) is 60-120 ℃, and the drying time is 8-12 h.

Further setting is that the inert gas in the step (2) is a mixed gas of argon and ammonia, and the proportion of ammonia is 5-15%.

Further setting the annealing temperature in the step (2) to be 700-1000 ℃, the heating rate to be 1-5 ℃/min and the heat preservation to be 1-3 h.

The second purpose of the invention is to provide the three-dimensional nitrogen-doped flower-shaped carbon sphere-loaded ultrafine nitrogen-doped molybdenum carbide nanoparticle electrocatalyst prepared by the preparation method.

A third object of the invention is the use of an electrocatalyst as described as an electrocatalyst in the electrolysis of water for the production of hydrogen.

The invention has the following beneficial effects:

1. according to the invention, flower-type carbon spheres, surfactants and ammonium molybdate solution with different mass ratios are loaded with molybdenum carbide by a hydrothermal synthesis method, and the surfactants play roles of Qiaolian-type carbon spheres and ammonium molybdate, so that molybdenum carbide nanoparticles in a product are uniformly dispersed on the pieces of the flower-type carbon spheres, the agglomeration phenomenon caused by high temperature is avoided, the size of the molybdenum carbide is reduced, and more active sites are exposed.

2. The thin petal wall of the flower-shaped carbon ball is beneficial to the permeation of electrolyte, increases the contact sites of the molybdenum carbide nano particles and the electrolyte and is convenient for electron transfer and charge transfer.

3. The ammonia gas introduced into the invention contains abundant nitrogen elements, and the nitrogen atoms are doped with the composite material after high-temperature annealing, so that the adsorption energy of hydrogen on the surface of the active substance is reduced, and the hydrogen is favorably separated out in the water electrolysis process.

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 only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.

FIG. 1 is an XRD pattern of a three-dimensional nitrogen-doped flower-type carbon sphere-supported ultrafine nitrogen-doped molybdenum carbide nanoparticle electrocatalyst synthesized by the method of the present invention according to example 2 and comparative example three;

graph analysis: as can be seen from the figure, Mo is contained in the catalyst₂C；

FIG. 2 is a scanning electron microscope and a high resolution picture of three-dimensional nitrogen-doped flower-shaped carbon sphere-loaded ultrafine nitrogen-doped molybdenum carbide nanoparticle electrocatalyst;

graph analysis: the catalyst is a flower-shaped ball with the microscopic appearance of about 200 nm;

FIG. 3 is a schematic diagram of hydrogen evolution performance of three-dimensional nitrogen-doped flower-shaped carbon sphere-loaded ultrafine nitrogen-doped molybdenum carbide nanoparticle electrocatalyst. Wherein, 2.5Mo₂C/NFCNS-800 is the sample of example 2, N-2.5Mo₂C/NFCNS-800-10% is the sample of example 6;

graph analysis: left panel at 0.5M H₂SO₄In solution, commercial platinum/carbon catalyst (20% mass fraction), 2.5Mo in example 2₂C/NFCNS-800 catalyst, for N-2.5Mo in example 6₂Linear voltammetric testing of C/NFCNS-800-10% catalyst. It can be seen from the figure that N-2.5Mo is added to the alloy of example 6₂The C/NFCNS-800-10% catalyst has the highest performance of catalytic hydrogen evolution, the initial overpotential is close to that of a commercial platinum/carbon catalyst, and the current density is 10mA/cm²The overpotential was 60 mV. And 2.5Mo in example 2₂C/NFCNS-800 catalyst with current density of 10mA/cm²The overpotential was 82 mV.

The right graph is a tafel slope plot for the three catalysts described above (tafel formula: η ═ b log (j) + a where j is the current density and b is the tafel slope)^-12.5Mo in example 2₂The Tafel slope of the C/NFCNS-800 catalyst was 39mV dec^-1The hydrogen evolution principle is shown to be Volmer-Heyrovsky, for N-2.5Mo in example 6₂The Tafel slope of C/NFCNS-800-10% catalyst is 31mV dec^-1It shows that the hydrogen evolution principle is Volmer-Tafel similar to that of platinum/carbon catalyst;

FIG. 4 is a graph of stability testing of a three-dimensional nitrogen-doped flower-shaped carbon sphere-loaded ultrafine nitrogen-doped molybdenum carbide nanoparticle electrocatalyst;

graph analysis: at 0.5M H₂SO₄In solution at a voltage of between 0.05 and-0.45V at 100mV s^-1The cyclic voltammetry test was performed at the same rate. As can be seen from the figure, the cyclic voltammetry curves have little change after 10000 times and 12000 times of cycling, which indicates that the catalyst has extremely high stability. The lower right hand corner of the graph is the chronoamperometric test of the catalyst, from which it can be seen that the catalyst was tested within 40 hoursThe current density is almost unchanged, and the catalyst is also proved to have extremely high stability.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.