阅读说明：本技术 一种过渡金属掺杂富缺陷的二硫化钼及其制备方法和应用 (Transition metal doped defect-rich molybdenum disulfide and preparation method and application thereof ) 是由 尹双凤 胡彪 陈浪 申升 郭君康 谢庭亮 蒋诗扬 王丙昊 于 2021-01-11 设计创作，主要内容包括：本发明公开了一种过渡金属掺杂富缺陷的二硫化钼及其制备方法和应用,所述过渡金属掺杂富缺陷的二硫化钼的分子式为M/MoS-(2-x),具有纳米花状结构,式中M为Mn、Co、Fe和W中的一种。本发明以富缺陷的二硫化钼作为基体材料,通过引入过渡金属,二硫化钼结构中的S空位浓度急剧增加,而高浓度的S空位,作为一个电子陷阱中心,有利于氮气的吸附和活化,明显的提升了光催化固氮的活性,例如Mn掺杂的MoS-(2-x)催化剂,在可见光下不加任何牺牲剂,氨的生成速率达到了148.3μmol/g/h,这大约是纯MoS-(2-x)的4.85倍。(The invention discloses transition metal doped defect-rich molybdenum disulfide and a preparation method and application thereof, wherein the molecular formula of the transition metal doped defect-rich molybdenum disulfide is M/MoS 2‑x The material has a nanometer flower-shaped structure, wherein M is one of Mn, Co, Fe and W. The method takes the defect-rich molybdenum disulfide as a matrix material, the concentration of S vacancies in the molybdenum disulfide structure is increased rapidly by introducing transition metal, and the high-concentration S vacancies are used as an electron trap center, so that the method is favorable for adsorption and activation of nitrogen, and obviously improves the activity of photocatalytic nitrogen fixation, such as Mn-doped MoS 2‑x The catalyst, without adding any sacrificial agent under visible light, has the ammonia generation rate of 148.3 mu mol/g/h, which is about pure MoS 2‑x 4.85 times of the total weight of the powder.)

1. A transition metal doped defect-rich molybdenum disulfide is characterized in that: the molecular formula of the transition metal doped defect-rich molybdenum disulfide is M/MoS_2-xThe material has a nanometer flower-shaped structure, wherein M is one of Mn, Co, Fe and W.

2. The transition metal doped defect-rich molybdenum disulfide of claim 1, wherein: the M/MoS_2-xWherein the molar ratio of M to Mo is (0.005-0.1): 1.

3. the transition metal doped defect-rich molybdenum disulfide of claim 2, wherein: the M/MoS_2-xWherein the molar ratio of M to Mo is (0.02-0.04): 1.

4. a process for the preparation of transition metal doped defect-rich molybdenum disulphide according to any of claims 1 to 3, characterized in that: the method comprises the following steps of uniformly mixing ammonium molybdate tetrahydrate, thiourea, soluble salt of M and water to obtain a mixed solution, and carrying out hydrothermal treatment on the mixed solution to obtain the ammonium molybdate tetrahydrate.

5. The method of claim 4, wherein: the molar ratio of the ammonium molybdate tetrahydrate to the thiourea is 1: 2-2.15, and the concentration of the ammonium molybdate tetrahydrate in the mixed solution is 0.01-0.04 mol/L.

6. The method of claim 4, wherein: when M is Mn, the soluble salt of M is manganese chloride tetrahydrate; when M is Co, the soluble salt of M is cobalt chloride; when M is Fe, the soluble salt of M is ferric chloride; when M is W, the soluble salt of M is tungsten ethoxide.

7. The method of claim 4, wherein: the temperature of the hydrothermal treatment is 180-220 ℃, and the time is 12-24 h.

8. Use of transition metal doped defect-rich molybdenum disulphide according to any of the claims 1 to 3 or transition metal doped defect-rich molybdenum disulphide obtainable by the preparation process according to any of the claims 4 to 7, wherein: it is used for photocatalysis nitrogen fixation reaction.

Technical Field

The invention belongs to the field of preparation and technology of photocatalytic materials, and particularly relates to transition metal doped defect-rich molybdenum disulfide, a preparation method thereof and application thereof in photocatalytic nitrogen fixation.

Background

Nitrogen (N) in the atmosphere₂) Fixation to ammonia (NH)₃) Is one of the most fundamental natural processes for the survival of all living beings and humans. The source of ammonia depends mainly on biological nitrogen fixation and industrial synthesis of ammonia. Wherein the industrial synthetic ammonia (Haber-Bosch method) lays the foundation of modern agriculture and greatly promotes the progress of modern civilization. However, this method requires high temperature (400 ≡ 600 ℃), high pressure (20-50MPa) to achieve dissociation of N ≡ N. And the reaction process needs to consume H₂At the expense, this consumes 1-2% of the global energy costs. Therefore, in view of the concept of sustainable development, it is necessary to develop an eco-friendly synthesis method with low energy dependence to replace the Haber-Bosch method for ammonia synthesis. It is widely believed that the photochemical synthesis of ammonia by using solar energy as power has great potential. However, extensive studies have shown that photocatalytic NRR processes suffer from low photocatalytic quantum efficiency due to nonpolar N ≡ N bonds and higher bond energies (≈ 945 kJ/mol).

Disclosure of Invention

In order to solve the problems in the prior art, the invention aims to provide transition metal doped molybdenum disulfide with rich defects and a preparation method and application thereof.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

transition metal doped defect-rich molybdenum disulfide with molecular formula of M/MoS_2-xThe material has a nanometer flower-shaped structure, wherein M is one of Mn, Co, Fe and W.

Preferably, the M/MoS_2-xWherein the molar ratio of M to Mo is (0.005-0.1): 1; more preferably (0.02 to 0.04): 1.

the invention also provides a preparation method of the transition metal doped defect-rich molybdenum disulfide, which comprises the steps of uniformly mixing ammonium molybdate tetrahydrate, thiourea, soluble salt of M and water to obtain a mixed solution, and carrying out hydrothermal treatment on the mixed solution to obtain the defect-rich molybdenum disulfide.

Preferably, the molar ratio of ammonium molybdate tetrahydrate to thiourea is 1: 2-2.15, and the concentration of the ammonium molybdate tetrahydrate in the mixed solution is 0.01-0.04 mol/L.

Preferably, when M is Mn, the soluble salt of M is manganese chloride tetrahydrate; when M is Co, the soluble salt of M is cobalt chloride; when M is Fe, the soluble salt of M is ferric chloride; when M is W, the soluble salt of M is tungsten ethoxide.

Preferably, the temperature of the hydrothermal treatment is 180-220 ℃ and the time is 12-24 h.

The invention also provides application of the transition metal doped defect-rich molybdenum disulfide in photocatalysis nitrogen fixation.

Compared with the prior art, the invention has the advantages that:

the method takes the defect-rich molybdenum disulfide as a matrix material, the concentration of S vacancies in the molybdenum disulfide structure is increased rapidly by introducing transition metal, and the high-concentration S vacancies are used as an electron trap center, so that the method is favorable for adsorption and activation of nitrogen, and obviously improves the activity of photocatalytic nitrogen fixation, such as Mn-doped MoS_2-xThe catalyst, without adding any sacrificial agent under visible light, has the ammonia generation rate of 148.3 mu mol/g/h, which is about pure MoS_2-x4.85 times of the total weight of the powder.

Drawings

FIG. 1 is a SEM photograph and EDS analysis of MS prepared in comparative example 1 and Mn-MS-4 prepared in example 1;

FIG. 2 shows MS obtained in comparative example 1 and Mn-MoS obtained in example 1_2-xXRD pattern of (a);

FIG. 3 is an XPS spectrum of MS obtained in comparative example 1 and Mn-MS-4 obtained in example 1;

FIG. 4 shows MS obtained in comparative example 1 and Mn-MoS obtained in example 1_2-xESR analysis chart of (1).

Detailed Description

The present invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.

The experimental procedures used in the following examples are not specifically described. All are conventional methods; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.

The catalytic activity of the prepared sample is examined by taking a photocatalytic nitrogen fixation reaction as a model:

5mg of catalyst powder was weighed and added to a reaction tube, 10ml of ultrapure water was added, then nitrogen gas was introduced for 30min under stirring at a flow rate of 50ml/min, then the xenon lamp light source was turned on, and nitrogen gas was continuously introduced under irradiation of visible light for 4 hours. After the reaction, the catalyst was centrifuged, and the catalyst was filtered through a 0.22 μm filter, and the resulting ammonium ions were detected in the supernatant by an ion selective electrode and a color development method.

Example 1

0.58g of ammonium molybdate tetrahydrate, 0.532g of thiourea and a certain mass of manganese chloride tetrahydrate (molar ratio of Mn: Mo is 0.005, 0.01, 0.02, 0.04 and 0.08) are added into 35ml of deionized water, stirred for 30 minutes, then placed into a crystallization kettle and treated for 12 hours at 180 ℃. Cooling to room temperature, washing for multiple times, and vacuum drying at 60 ℃ to obtain Mn-MoS_2-xA catalyst.

Table 1 different Mn: photocatalytic nitrogen fixation results for Mo molar ratio samples

Comparative example 1

0.58g of ammonium molybdate tetrahydrate and thiourea of a certain mass (the mol ratio of S: Mo is 2.13, 3 and 4) are added into 35ml of deionized water, stirred for 30 minutes and then put into a crystallization kettle to be processed for 12 hours at 180 ℃. Cooling to room temperature, washing for multiple times, and vacuum drying at 60 ℃ to obtain MoS_2-xA catalyst.

Table 2 different S: photocatalytic nitrogen fixation results for Mo molar ratio samples

Example 2

0.58g of ammonium molybdate tetrahydrate, 0.532g of thiourea and a certain mass of cobalt chloride (molar ratio of Co: Mo is 0.005, 0.01, 0.02, 0.04 and 0.08) are added into 35ml of deionized water, stirred for 30 minutes, then placed into a crystallization kettle and treated for 12 hours at 180 ℃. Cooling to room temperature, washing for many times, and vacuum drying at 60 ℃ to obtain Co-MoS_2-xA catalyst.

Table 3 different Co: photocatalytic nitrogen fixation results for Mo molar ratio samples

Example 3

0.58g of ammonium molybdate tetrahydrate, 0.532g of thiourea and a certain mass of ferric chloride (Fe: Mo molar ratio is 0.005, 0.01, 0.02, 0.04 and 0.08) are added into 35ml of deionized water, stirred for 30 minutes, then placed into a crystallization kettle and treated for 12 hours at 180 ℃. Cooling to room temperature, washing for many times, and vacuum drying at 60 ℃ to obtain Fe-MoS_2-xA catalyst.

Table 4 different Fe: photocatalytic nitrogen fixation results for Mo molar ratio samples

Example 4

0.58g of ammonium molybdate tetrahydrate, 0.532g of thiourea and a certain mass of tungsten ethoxide (W: Mo molar ratio is 0.005, 0.01, 0.02, 0.04 and 0.08) are added into 35ml of deionized water, stirred for 30 minutes, then placed into a crystallization kettle and treated for 12 hours at 180 ℃. Cooling to room temperature, washing for many times, and vacuum drying at 60 ℃ to obtain W-MoS_2-xA catalyst.

Table 4 different W: photocatalytic nitrogen fixation results for Mo molar ratio samples

As shown in FIG. 1, after Mn doping, Mn-MoS_2-xThe appearance is not changed, the structure is a nanoflower structure, and the size is uniform.

As shown in FIG. 2, the XRD pattern illustrates MoS_2-xAnd Mn-MoS_2-xThe material is exposed to MoS₂Medium 002, 100, 110 crystal plane. And as the content of Mn element is increased, a new diffraction peak appears in an XRD pattern, which is probably caused by MoS due to excessive manganese_2-xThe material shows a phase separation phenomenon, and the MnS material is generated.

As shown in FIG. 3, a MoS is illustrated_2-xAnd Mn-MoS_2-xThe chemical environment of Mo and S in the material is changed. And FIG. 3a also demonstrates Mn-MoS_2-xMn element is present in the catalyst.

As shown in fig. 4, the ESR spectrum indicates that the vacancy concentration of the catalyst is enhanced with the doping of manganese, which is beneficial to the adsorption of nitrogen molecules to some extent.