阅读说明：本技术 具有安培级电流密度析氢性能的Mo/MoO2面内异质结的制备 (Mo/MoO with ampere-level current density hydrogen evolution performance2Preparation of in-plane heterojunctions ) 是由 刘友文 温群磊 翟天佑 于 2021-01-15 设计创作，主要内容包括：本发明公开了一种具有安培级电流密度析氢性能的Mo/MoO-2面内异质结的制备,包括以下步骤：(1)前驱体MoO-2纳米片的制备：将原料MoO-3粉末在氢气与惰性载气的混合气氛下于800～1000℃进行焙烧,得到前驱体MoO-2纳米片；(2)将前驱体MoO-2纳米片在混合气氛下于400～700℃进行焙烧,得到MoO-2/Mo面内结材料。本发明通过对制备方法的反应机理、整体流程工艺设计等进行改进,利用两步分阶段的焙烧还原,可以由商业MoO-3粉末原料制备得到MoO-2/Mo面内结材料,制备方法简单可控,得到的Mo/MoO-2面内异质结材料富有褶皱结构,作为电催化制氢催化剂应用时,具有安培级的电催化反应活性。(The invention discloses Mo/MoO with ampere-level current density hydrogen evolution performance 2 The preparation of the in-plane heterojunction comprises the following steps: (1) precursor MoO 2 Preparing a nano sheet: the raw material MoO 3 Roasting the powder at 800-1000 ℃ in a mixed atmosphere of hydrogen and inert carrier gas to obtain a precursor MoO 2 Nanosheets; (2) the precursor MoO is added 2 Roasting the nanosheets at 400-700 ℃ in a mixed atmosphere to obtain MoO 2 the/Mo in-plane junction material. The invention improves the reaction mechanism, the whole process design and the like of the preparation method, utilizes two-step staged roasting reduction and can prepare commercial MoO 3 Preparing MoO from powder raw material 2 The preparation method of the/Mo in-plane junction material is simple and controllable, and the obtained Mo/MoO 2 The in-plane heterojunction material is rich in a fold structure and has ampere level when being used as an electro-catalytic hydrogen production catalystElectrocatalytic reaction activity.)

1. Mo/MoO with ampere-level current density hydrogen evolution performance₂The preparation method of the in-plane heterojunction is characterized by comprising the following steps:

(1) precursor MoO₂Preparing a nano sheet: the raw material MoO₃Placing the powder into a porcelain boat, then placing the porcelain boat into a heating furnace, and roasting at 800-1000 ℃ in a mixed atmosphere of hydrogen and inert carrier gas to obtain a precursor MoO₂Nanosheets;

(2)MoO₂preparation of/Mo in-plane junction material: subjecting the precursor MoO obtained in the step (1) to₂Placing the nanosheets into a heating furnace, and roasting at 400-700 ℃ in a mixed atmosphere of hydrogen and inert carrier gas to obtain MoO₂a/Mo in-plane junction material; the MoO₂the/Mo in-plane junction material can provide more than 1A cm under the overpotential condition of 468mV^-2The current density of (1).

2. The method according to claim 1, wherein in the step (1), the flow ratio of the hydrogen gas and the inert carrier gas in the mixed atmosphere is 10: 1-1: 10; the flow rate of the mixed atmosphere is 50sccm to 600 sccm.

3. The method according to claim 1, wherein in the step (1), MoO is used as a raw material₃The mass of the powder does not exceed 10 g.

4. The method according to claim 1, wherein in the step (1), the calcination time is 10 to 120 min.

5. The preparation method according to claim 1, wherein in the step (1), the heating furnace is a slide rail tube furnace, and the roasting is carried out by moving a central temperature zone of the slide rail tube furnace to the MoO after the temperature of the slide rail tube furnace is raised to a preset roasting temperature₃The centre of the powder;

preferably, the heating rate of the sliding rail tube furnace is 5-30 ℃ min^-1。

6. The method according to claim 1, wherein in the step (2), the flow ratio of the hydrogen gas to the inert carrier gas in the mixed atmosphere is 10: 1-1: 10; the flow rate of the mixed atmosphere is 50sccm to 600 sccm.

7. The method according to claim 1, wherein in the step (2), the precursor MoO is₂The mass of the nanosheets does not exceed 9 g.

8. The method according to claim 1, wherein in the step (2), the roasting time is 10 to 300 min.

9. The preparation method according to claim 1, wherein in the step (2), the heating furnace is a slide rail tube furnace, and the baking is carried out by moving a central temperature zone of the slide rail tube furnace to the MoO precursor after the temperature of the slide rail tube furnace is raised to a preset baking temperature₂The center of the nanosheet is processed;

preferably, the heating rate of the sliding rail tube furnace is 5-30 ℃ min^-1。

Technical Field

The invention belongs to the technical field of electrocatalysis hydrogen evolution, and particularly relates to Mo/MoO with ampere-level current density hydrogen evolution performance₂And (4) preparing an in-plane heterojunction.

Background

The construction of a global sustainable energy storage and transformation system is currently one of the most central challenges for human survival and development. As the most potential clean energy, hydrogen energy is brought into the national energy strategy, and becomes an important choice for optimizing energy consumption structure and guaranteeing national energy supply safety. Among the numerous methods for producing hydrogen by electrolyzing water, the method for producing hydrogen by electrolyzing water has the advantages of stable hydrogen production amount, high hydrogen purity, simple device, relatively mature technology and the like, and is the most promising method for realizing large-scale hydrogen production. Currently, the key factor restricting the industrialization of hydrogen production by water electrolysis is the water electrolysis catalyst. Although noble metal catalysts such as platinum and the like have remarkable electrocatalytic hydrogen production reaction activity, the price is high, the reserves are extremely scarce, and the large-scale industrial utilization is difficult. Ampere-level hydrogen production (current density)>1000mA cm^-2) Long-foot challenges remain.

The field of electrocatalysis has made great progress in the search of numerous precursors of material chemistry. However, the current electrocatalytic hydrogen evolution material still has low current density (10mA cm)^-2Level) and the like. Metallic transition metal oxo compound MoO₂Due to the unique physical and chemical properties, the catalyst has potential application in the fields of electrocatalysis, energy storage and conversion and the like. The surface electronic structure is rich in MoO₂And the inherent properties of the two-dimensional material and the premise of widening the application of the two-dimensional material. Meanwhile, for heterogeneous catalytic reaction, the electric double layer structure of the local surface of the material is also important. The preparation of the in-plane junction material is in MoO₂The process of introducing a foreign phase lattice in the two-dimensional plane of the two-dimensional material provides a new degree of freedom for designing and regulating the material properties. Currently based on MoO₂The electrocatalytic hydrogen evolution material of (2) is mostly limited to MoO₂The two-dimensional plane of (2) is used as a substrate for anchoring and dispersing the active phase, the catalytic current of the two-dimensional plane is often low, the preparation of the two-dimensional plane is complicated, and an additional process is needed for introducing the active phase.

Therefore, a new solution is needed to be designed and developed to fully utilize the MoO₂The charge of the surface of the material can be modulated while the material has unique physical and chemical propertiesDistributed and localized electric double layer structure to design and develop new MoO-based₂The ampere-level electrocatalytic hydrogen evolution material.

Disclosure of Invention

In view of the above-mentioned drawbacks and needs of the prior art, it is an object of the present invention to provide a Mo/MoO with amperometric current density hydrogen evolution performance₂The preparation of the in-plane heterojunction, in which the reaction mechanism, the overall process design, etc. of the preparation method are improved, and the two-step calcination reduction reaction is utilized, the method can be prepared from commercial MoO₃Preparing MoO from powder raw material₂The preparation method of the/Mo in-plane junction material is simple and controllable, and the obtained Mo/MoO₂The in-plane heterojunction material is rich in a fold structure, has ampere-level electrocatalytic reaction activity when being used as an electrocatalytic hydrogen production catalyst, and can provide over 1A cm by only 468mV overpotential^-2The current density of (1). The MoO rich in folds and obtained based on the preparation method of the invention₂The content of the/Mo in-plane junction material is, for example, 0.5M H₂SO₄When the electrocatalyst is applied to the preparation of hydrogen from electrolyte, the catalyst has rich in-plane strain, the strain has a modulation effect on an electronic structure on the surface of the material and a local double electric layer structure, hydrogen ions are enriched on the surface of the catalyst and are promoted to be adsorbed and activated, rich active sites and high hydrogen ion concentration are provided for the electrocatalytic hydrogen evolution, and therefore the material shows the ampere-level current density hydrogen evolution activity. For an in-plane junction material, MoO₂The self-metal property can ensure rapid and sufficient electron supply in large-current catalysis, and simultaneously, due to the two-dimensional characteristic, the active surface area can be maximized after the nano-scale in-plane junction is constructed. After the in-plane junction is formed, the surface of the material may have locally unbalanced electric field distribution, and the double electric layer structure can be modulated. Meanwhile, the introduction of the in-plane junction is required to be safe and controllable, the cost is low, and the ampere-level catalytic current can be represented.

To achieve the above object, according to the present invention, there is provided a Mo/MoO having Ampere-level current density hydrogen evolution performance₂The preparation method of the in-plane heterojunction is characterized by comprising the following steps:

(1) front sideDriving body MoO₂Preparing a nano sheet: the raw material MoO₃Placing the powder into a porcelain boat, then placing the porcelain boat into a heating furnace, and roasting at 800-1000 ℃ in a mixed atmosphere of hydrogen and inert carrier gas to obtain a precursor MoO₂Nanosheets;

(2)MoO₂preparation of/Mo in-plane junction material: subjecting the precursor MoO obtained in the step (1) to₂Placing the nanosheets into a heating furnace, and roasting at 400-700 ℃ in a mixed atmosphere of hydrogen and inert carrier gas to obtain MoO₂a/Mo in-plane junction material; the MoO₂the/Mo in-plane junction material can provide more than 1A cm under the overpotential condition of 468mV^-2The current density of (1).

As a further preferred aspect of the present invention, in the step (1), the flow ratio of the hydrogen gas and the inert carrier gas in the mixed atmosphere is 10: 1-1: 10; the flow rate of the mixed atmosphere is 50sccm to 600 sccm.

As a further preferred aspect of the present invention, in the step (1), MoO as a raw material₃The mass of the powder does not exceed 10 g.

In a further preferred embodiment of the present invention, in the step (1), the calcination time is 10 to 120 min.

As a further preferable mode of the invention, in the step (1), the heating furnace is a slide rail tube furnace, and the baking is performed by moving a central temperature zone of the slide rail tube furnace to the MoO after the temperature of the slide rail tube furnace is raised to a preset baking temperature₃The centre of the powder;

preferably, the heating rate of the sliding rail tube furnace is 5-30 ℃ min^-1。

As a further preferred aspect of the present invention, in the step (2), the flow ratio of the hydrogen gas to the inert carrier gas in the mixed atmosphere is 10: 1-1: 10; the flow rate of the mixed atmosphere is 50sccm to 600 sccm.

As a further preferred aspect of the present invention, in the step (2), the precursor MoO is₂The mass of the nanosheets does not exceed 9 g.

In a further preferred embodiment of the present invention, in the step (2), the calcination time is 10 to 300 min.

As a further preferable mode of the invention, in the step (2), the heating furnace is a slide rail tube furnace, and the baking is performed by moving a central temperature region of the slide rail tube furnace to the precursor MoO after the temperature of the slide rail tube furnace is raised to a preset baking temperature₂The center of the nanosheet is processed;

preferably, the heating rate of the sliding rail tube furnace is 5-30 ℃ min^-1。

Through the technical scheme of the invention, compared with the prior art, the method can be used for preparing commercial MoO by using two-step roasting reduction reaction₃Preparing MoO from powder raw material₂The preparation method of the/Mo in-plane junction material is simple and controllable, and the obtained Mo/MoO₂The in-plane heterojunction material is rich in a fold structure, and has ampere-level electrocatalytic reaction activity when being used as an electrocatalytic hydrogen production catalyst.

The invention effectively realizes the precursor MoO₂Macro rapid preparation of nanosheet and Mo/MoO₂Controllable construction of in-plane heterojunctions. The commonly used liquid phase method or CVD method is often difficult to obtain two-dimensional MoO₂The pure-phase nanosheet has the problems of low yield, long preparation period, complicated preparation process and difficulty in amplification. In the two-step roasting reduction method adopted by the invention, commercial MoO is directly utilized firstly₃Powder as synthetic two-dimensional MoO₂And (3) raw materials of the nano sheets. MoO₃Is a layered material having a melting point of 795 c, and below which significant sublimation of the material can occur. Using MoO₃Due to special crystal structure and physical properties, the rapid reduction roasting adopted by the invention ensures that the commercial MoO is obtained₃The powder is shock-heated and subsequently sublimed into flaky MoO₃And (4) crystals. Sheet MoO₃The crystal is subjected to transient reduction reaction in the mixed atmosphere of flowing hydrogen and inert carrier gas to finally obtain equivalent two-dimensional MoO₂Nanosheets. It is easy to understand that only commercial MoO needs to be controlled₃The amount of the powder is proportional to the flow of the mixed atmosphere, so that the experiment can be amplified to a certain extent to obtain macroscopic quantity of two-dimensional MoO₂And (3) a nanosheet precursor.

The invention preferably adopts a slide rail tube furnace to ensure commercial MoO₃The powder can be suddenly heated and sublimated into flake MoO₃A crystal; the invention adopts a rapid reduction roasting method, and can avoid the byproduct Mo powder generated by roasting along with the furnace temperature rise. Considering the extremely short reaction time, it is easy to understand that the process can be realized by controlling the excessive hydrogen and the roasting temperature in theory. The invention then makes use of the MoO obtained₂The nanosheet is used as a precursor, the two-dimensional plane of the nanosheet is used as a template, the reducibility of hydrogen is utilized, and the oxygen content on the surface is regulated and controlled, so that Mo/MoO is introduced₂And (4) forming an in-plane junction. In order to introduce abundant surface wrinkles, the invention preferably adopts a rapid reduction roasting method to treat MoO₂Processing the precursor, and rapidly losing oxygen to induce local lattice mismatch and generate strain to finally obtain the MoO rich in wrinkles₂The catalyst is a/Mo in-plane junction catalyst. It is easy to understand that the oxygen content, namely Mo/MoO can be controlled by controlling any one of the parameters of the reaction time, the roasting temperature and the hydrogen content theoretically₂And regulating and controlling the content of the in-plane junction.

MoO that will be wrinkle-rich in this application₂The amount of the/Mo in-plane junction catalyst is 0.5M H₂SO₄The electrocatalyst for preparing hydrogen for the electrolyte has rich in-plane strain, and the strain has modulation effect on the electronic structure on the surface of the material and the local double electric layer structure, is favorable for enriching hydrogen ions on the surface of the catalyst and promoting the adsorption and activation of the hydrogen ions, and provides rich active sites and high hydrogen ion concentration for the electrocatalytic hydrogen evolution, so that the folded MoO is rich₂the/Mo in-plane junction catalyst has ampere-level current density hydrogen evolution activity. The experimental result shows that the catalyst can provide 1A cm only by 468mV overpotential^-2The catalytic hydrogen production current. Meanwhile, in the preparation process of the material, the operation is quick and convenient, and the reaction is simple and controllable.

In conclusion, the fold-rich MoO obtained based on the specific preparation method of the invention₂the/Mo surface junction material is an ampere-grade electro-catalytic hydrogen production material, and particularly can be used as a catalyst for electro-catalytic hydrogen production. Because the material has rich surface strain, rich active sites are provided for electrocatalytic hydrogen production, and simultaneously, the material can be used for preparing hydrogenThe surface enrichment of double-layer ions is modulated, so that the material shows ampere-level current density hydrogen evolution activity. The preparation method of the material is rapid and convenient, and the reaction is simple and controllable. Meanwhile, the catalyst is in a powder form, has strong environment adaptability, and is expected to be applied to special scenes such as proton exchange membrane fuel cells and the like.

Drawings

FIG. 1 shows a precursor MoO prepared according to the present invention₂Nanosheet and pleat-rich MoO₂Transmission electron microscopy images of different magnifications of the/Mo catalyst. Wherein, the precursor MoO before the second roasting of the preparation method is respectively corresponded from left to right in figure 1₂And the nano sheets and the samples with the second roasting time of 30min, 90min, 150min and 210 min. The morphological characteristics of the samples are observed under different magnifications, and the precursor MoO₂The nano sheet has a flat two-dimensional plane, and a sample after reduction roasting forms abundant surface wrinkles and nano holes due to the existence of surface strain.

FIG. 2 shows a precursor MoO prepared according to the present invention₂Nanosheet and pleat-rich MoO₂Atomic force microscope image of/Mo catalyst, wherein (a) in FIG. 2 corresponds to the precursor MoO₂Nanosheets, (b) in figure 2 corresponds to the fold-rich MoO obtained in the 2 nd step with the reduction roasting time of 90min₂A Mo catalyst.

FIG. 3 shows a precursor MoO prepared according to the present invention₂Nanosheet and pleat-rich MoO₂An X-ray powder diffraction spectrum of the/Mo catalyst, wherein (b) in fig. 3 is a partially enlarged view of (a) in fig. 3.

FIG. 4 shows a precursor MoO prepared according to the present invention₂Nanosheet and pleat-rich MoO₂A raman spectrum of the/Mo catalyst, wherein (b) in fig. 4 is a partially enlarged view of (a) in fig. 4.

FIG. 5 shows a precursor MoO prepared according to the present invention₂Nanosheet and pleat-rich MoO₂Linear voltammogram profiles of the/Mo catalyst and related control samples.

FIG. 6 shows a fold-rich MoO prepared according to the present invention₂Steady voltage test and Faraday efficiency of electro-catalysis hydrogen production of/Mo catalyst (taking 90min sample as example))。

FIG. 7 shows a fold-rich MoO prepared according to the present invention₂High-resolution transmission electron microscope images of the/Mo in-plane junction catalyst (taking 90min samples as examples); wherein a1 in fig. 7 and a2 in fig. 7 are enlarged views of corresponding regions indicated by a in fig. 7, respectively.

FIG. 8 shows the precursor MoO prepared under the preferred experimental parameters (900 deg.C for 30min)₂The nano-sheets and XRD diffraction patterns of samples prepared under corresponding boundary conditions. Wherein the XRD diffraction pattern index of the sample reacted at 800 ℃ for 120min and the sample reacted at 900 ℃ for 30min is pure phase MoO₂. The main phase of the sample is MoO after reacting for 10min at 1000 DEG C₂But in the presence of Mo_xO_yA multimeric impurity. Probably due to excessive reaction temperature, resulting in sublimed two-dimensional MoO₃Excessive crystals, partially two-dimensional MoO₃The crystals did not react completely.

FIG. 9 shows Mo/MoO prepared according to the preferred experimental parameters of the present invention (reaction at 550 ℃ C. for 90min)₂In-plane junctions and corresponding boundary conditions the XRD diffraction pattern of the sample was prepared. The diffraction patterns of all three samples contained MoO₂And diffraction signals of the two phases Mo. The sample reacted at 400 ℃ for 300 minutes contained only a very small amount of Mo, indicating that the boundary temperature at 400 ℃ is relatively low and the reduction reaction is particularly slow. The samples contained only a very small amount of MoO at 550 ℃ for 90 minutes and at 700 ℃ for 10 minutes₂The reduction reaction is relatively thorough. The temperature of 700 ℃ is used as the boundary temperature, and is a relatively high temperature, so that the reduction reaction rate is fast, and the reaction is relatively uncontrollable under the condition.

FIG. 10 shows Mo/MoO prepared according to the preferred experimental parameters of the present invention (reaction at 550 ℃ C. for 90 minutes)₂Preparing electrocatalysis hydrogen production performance of the sample by the aid of the in-plane junction and corresponding boundary conditions. The preferred samples exhibit optimal electrocatalytic hydrogen evolution performance relative to the two boundary condition samples.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example 1

The embodiment of the invention discloses an ampere-grade electrocatalytic hydrogen production material and a preparation method thereof, wherein the ampere-grade electrocatalytic hydrogen production material comprises the following steps:

precursor MoO₂Preparing a nano sheet: will be commercial MoO₃Placing the powder in a porcelain boat, then placing the porcelain boat in a slide rail tube furnace, and roasting at high temperature in a hydrogen-argon mixed atmosphere (of course, the mixed atmosphere of hydrogen and other inert carrier gases can also be used) to obtain a precursor MoO₂Nanosheets;

pleated MoO₂Preparation of/Mo in-plane junction material: the precursor MoO is added₂Placing the nano sheets in a porcelain boat, then placing the porcelain boat in a slide rail tube furnace, and roasting at high temperature in a hydrogen-argon mixed atmosphere to obtain the MoO rich in wrinkles₂the/Mo in-plane junction material.

The invention provides a fold-rich MoO₂the/Mo in-plane junction material can be used as an electrocatalyst for electrocatalytic hydrogen production, and due to the wrinkle-rich MoO₂the/Mo in-plane junction material has abundant surface strain, provides abundant active sites for electrocatalytic hydrogen production, and can modulate a local double electric layer structure to realize the surface enrichment of hydrogen ions, so that the material shows ampere-level current density hydrogen evolution activity. The preparation method of the material is rapid and convenient, and the reaction is simple and controllable.

In the process of electro-catalysis hydrogen production, the electro-catalyst adopted by the application is the MoO rich in folds₂The material has rich surface strain, the appearance characteristics of the material are represented by multiple cracks, protrusions and folds, the whole material is of a nanosheet structure, the size of the nanosheet is 200-1000 nm, and the thickness of the nanosheet is 2-10 nm. The wrinkle-rich MoO₂The preparation method of the/Mo in-plane junction material comprises a precursor MoO₂Preparation of nanosheets and wrinkled MoO₂Two processes for preparing the/Mo in-plane junction material, namely commercial MoO₃Placing the powder in a porcelain boat, then placing the porcelain boat in a sliding rail tube furnace, and mixing in hydrogen and argonRoasting at high temperature in a synthetic atmosphere to obtain a precursor MoO₂Nanosheets; then placing the precursor in a porcelain boat, then placing the porcelain boat in a slide rail tube furnace, roasting under hydrogen-argon mixed atmosphere, and performing chemical reduction topological conversion to obtain wrinkle-rich MoO₂the/Mo in-plane junction material. In particular, the wrinkle-rich MoO₂The preparation method of the/Mo in-plane junction material comprises the following steps:

precursor MoO₂Preparing a nano sheet: will be commercial MoO₃Placing the powder in a porcelain boat, then placing the porcelain boat in a slide rail tube furnace, and roasting at high temperature in a hydrogen-argon mixed atmosphere to obtain a precursor MoO₂Nanosheets;

pleated MoO₂Preparation of/Mo in-plane junction material: the precursor MoO is added₂Placing the nano sheets in a porcelain boat, then placing the porcelain boat in a slide rail tube furnace, and roasting at high temperature in a hydrogen-argon mixed atmosphere to obtain the MoO rich in wrinkles₂the/Mo in-plane junction material.

In the above-mentioned precursor MoO₂In the preparation process of the nanosheet, the commercial MoO₃The mass of the powder is 0.2-10 g, the adopted heating method is rapid annealing, and the heating rate is 5-30 ℃ for min^-1The roasting time is 10-120 min, and the precursor MoO is obtained₂The specific preparation process of the nano sheet comprises the following steps:

weighing commercial MoO₃Placing and stacking the powder in a porcelain boat, placing the porcelain boat in a proper position of a slide rail tube furnace, introducing a hydrogen-argon mixed atmosphere, heating, moving the slide rail furnace to a central temperature area and a commercial MoO after the heating process is finished₃The powder centers are superposed, the calcination is started, and the precursor MoO is obtained after the calcination is finished₂Nanosheets; in certain embodiments, the weighed commercial MoO₃The powder mass is 0.5g, the roasting temperature is 900 deg.C, the roasting time is 30min, and the heating rate is 20 deg.C for min^-1The ratio of the hydrogen-argon mixture gas to be roasted is 2: 8, the total volume of the mixed gas is 100 sccm.

The application will then obtain the precursor MoO₂Roasting the nanosheets, and obtaining the fold-rich MoO by utilizing chemical reduction topological transformation₂a/Mo in-plane junction material; the temperature of the roasting isRoasting at 400-700 deg.c for 10-300 min and at 5-30 deg.c for min^-1The ratio of the hydrogen-argon mixture gas to be roasted is 10: 1-1: 10, 50-600 sccm of the total mixed gas; in certain embodiments, the weighed precursor MoO₂The mass of the nano-sheets is 3mg, the roasting temperature is 550 ℃, the roasting time is 30min, 90min, 150min and 210min, and the heating rate is 20 ℃ for min^-1The ratio of the hydrogen-argon mixture gas to be roasted is 2: 8, the total volume of the mixed gas is 100 sccm.

In the preparation of fold-rich MoO₂When the material is a/Mo in-plane junction material, firstly, a precursor MoO is prepared₂Nanosheets, commercial MoO upon rapid reduction roasting₃Powder suddenly thermally sublimes and forms two-dimensional MoO₃Crystal steam which is subjected to reduction reaction under hydrogen-argon mixed reducing atmosphere to obtain precursor MoO₂Nanosheets; subsequently, under the hydrogen-argon mixed reducing atmosphere, the MoO is subjected to topological transformation by utilizing high-temperature chemical reduction₂Introducing second-phase Mo into the flat surface to obtain MoO rich in wrinkles₂the/Mo in-plane junction material.

To verify the MoO of the fold enrichment₂Ampere current density hydrogen evolution activity of/Mo in-plane junction material, as an example, the Pleated MoO prepared by the present application₂the/Mo in-plane junction material is used as an electrocatalyst and is in the range of 0.5M H₂SO₄Carrying out electrocatalytic hydrogen production reaction; i.e. first the ruffled MoO₂the/Mo in-plane junction material is dispersed in nafion ethanol solution to prepare dispersion liquid, and the dispersion liquid is dripped on a glassy carbon electrode for airing, and then the electrode is used as a working electrode for subsequent electrocatalytic hydrogen production reaction. To avoid introducing impurities, 0.5M H₂SO₄The water in (1) is preferably deionized water in general. The preparation process of the dispersion liquid comprises the following specific steps:

will wrinkle-rich MoO₂Adding the/Mo surface bonding material into an ethanol solution of nafion, and ultrasonically oscillating for 30 min. In particular, the dispersion is rich in folded MoO₂The concentration of the/Mo in-plane junction material is 2-10 mg ml^-1The volume fraction of nafion in the nafion ethanol solution is 0.2-1%. Using a liquid-transfering gun to transfer a proper quantity of dispersed liquid to coat on the glassy carbon electrodeAnd (5) drying. Specifically, the volume of the dispersion liquid transferred by the liquid transfer gun is 5-10 mu L, and the diameter of the glassy carbon electrode is 3 mm. In a specific example, the dispersion concentration is 5mg ml^-1The volume fraction of nafion was 0.5%, and the volume of the dispersion taken by the pipette was 7 uL. And finishing the preparation of the working electrode after air drying. Subsequent control of the MoO enriched with wrinkles₂The ampere-level current density hydrogen evolution activity of the/Mo in-plane junction material is verified, the working electrode, the saturated Ag/AgCl reference electrode and the graphite rod counter electrode form a three-electrode system, and a Chenghua CHI660e electrochemical workstation is used as a direct current power supply and is operated at 0.5M H₂SO₄Cyclic voltammetry tests were performed in solution while the faradaic efficiency was calculated using gas chromatography to detect the gaseous products.

As shown in FIGS. 4 and 5, it can be demonstrated that the MoO is wrinkle-rich₂the/Mo in-plane junction material has ampere-level current density hydrogen evolution activity, and can provide 1000mA cm by only 468mV overpotential^-2The current density of the catalytic hydrogen production is close to 100 percent.

As shown in FIG. 1, the precursor MoO₂The nanoplatelets have flat two-dimensional planes with lateral dimensions between hundreds of nanometers to several microns, the lower substrate indicating an ultra-thin thickness. The sample after reduction roasting basically maintains the precursor MoO₂The morphological characteristics of the nanosheets, and due to the surface strain, abundant surface wrinkles and nano holes are formed in the sample. Taking the sample as an example of a reaction 30min sample, the edges of partial nanosheets of the sample roll up, and nanoscale pores and nanoscale wrinkles (greater contrast) can also be observed, indicating the presence of in-plane strain.

As shown in FIG. 2, the precursor MoO₂The nano-sheet is an ultrathin two-dimensional nano-sheet, the surface of the nano-sheet is flat, and the thickness of the nano-sheet is about 6.1 nm. Taking a sample which is reacted for 90min as an example, the thickness of the sample is slightly reduced to 4.89nm, and obviously fluctuated folds exist on the surface, which is consistent with the observation and analysis results of the figure 1.

As shown in FIGS. 3 and 4, the precursor MoO₂The index of X-ray diffraction pattern of the nano-sheet is pure phase MoO₂. The Mo content of the treated sample gradually increased with the lapse of time, and the treatment conditions in this example were set to be as followsThe index of the X-ray diffraction pattern of the sample with the treatment time of more than 150min is a pure phase Mo simple substance. Illustrating that the oxygen content, i.e., Mo/MoO, can be adjusted by adjusting the treatment time₂And regulating and controlling the content of the in-plane junction. The right enlarged region is the characteristic peak of the Mo elementary substance X-ray diffraction pattern, and the peak position of the treated sample is shifted, which indicates that in-plane strain exists.

As shown in FIG. 5, the precursor MoO₂The polarized current density of the nanosheets and commercial Mo powder is very low, which indicates that the HER catalytic performance of the nanosheets and commercial Mo powder is very poor. The surface junction material treated by the embodiment rapidly increases the polarization current density along with the increase of the overpotential, and shows the hydrogen evolution performance of ampere-level current density. Taking a sample reacted for 90min as an example, when the overpotential is large: (>600mV) with performance comparable to commercial Pt/C.

As shown in fig. 6, taking a sample reacted for 90min as an example, the current-time curve of the sample under different polarization potentials is stable, which indicates that the cycling stability performance is excellent. The sample only needs 468mV overpotential to provide 1mA cm^-2Catalytic current density of (2). Meanwhile, the gas product is detected by gas chromatography, and the sample shows more than 85% of Faraday efficiency under different potentials.

As shown in FIG. 7, taking the sample reacted for 90min as an example, two phases were observed to exist in the atomic phase of the sample, and the phase index with a lattice spacing of 0.235nm was Mo (110), and the phase index with a lattice spacing of 0.220nm was MoO₂(021). This shows the successful introduction of Mo/MoO₂And (4) forming an in-plane junction. Compared with Mo (110) and MoO₂(021) The theoretical lattice spacings of 0.2247nm and 0.2171nm, respectively, the Mo (110) plane lattice spacing increases significantly, indicating the presence of in-plane strain. The obvious change of contrast brightness of the whole atomic phase indicates that abundant nano-scale folds exist.

Example 2

It is easy to understand that in the preparation of the precursor MoO₂In the process of nanosheet, the total flow rate of the mixed gas determines the sublimation two-dimensional MoO₃The residence time of the crystals, i.e. the reduction reaction time, the holding temperature and the partial pressure of the reducing hydrogen determine the rate of the reduction reaction, and the calcination time ensures commercial MoO₃The powder was fully sublimed and reduced. For macro scale experiment, the invention is suggested to be carried out in a quartz tube with larger diameter, and it is easy to understand that when the larger quartz tube is adopted, the flow rate of the mixed gas can be properly increased to ensure that the flow rate, namely the reduction reaction time is constant, and the heat preservation time is properly prolonged to ensure that the commercial MoO is kept constant₃The powder is fully sublimated and reacted. The same strategy applies when the firing temperature is low, such as 800 ℃. In order to guarantee the service life of the sliding track furnace, the application does not suggest to carry out the experiment at a higher temperature, such as above 1000 ℃. To ensure the reaction is controllable, in the specific embodiment, the reaction is performed by using a quartz tube with a diameter of 2.5cm, and the total flow rate of the mixed gas is controlled to be 100sccm to prepare the precursor MoO₂Nanosheets.

To illustrate the effect of the above parameters on the reaction, the present application designed the following experiments: 0.5g commercial MoO was weighed₃Placing the powder in a porcelain boat, reacting in a slide rail tube furnace at 1000 ℃ for 10min under the hydrogen-argon mixed atmosphere of 20/80sccm, and collecting a product; 0.5g commercial MoO was weighed₃Placing the powder in a porcelain boat, reacting in a slide rail tube furnace at 800 ℃ for 120min under the hydrogen-argon mixed atmosphere of 20/80sccm, and collecting a product; 0.5g commercial MoO was weighed₃The powder is placed in a porcelain boat and reacted for 30min in a slide rail tube furnace at 900 ℃ under the hydrogen-argon mixed atmosphere of 20/80sccm, and the product is collected. In the above control experiment, the XRD diffraction patterns of the latter two products are both indicated by MoO₂It is demonstrated that the experiment has better controllability. Wherein the main phase of the product after reaction for 10min at 1000 ℃ is MoO₂However, commercial MoO was too high due to this temperature₃The sublimation rate of the powder is too fast, resulting in partially sublimed two-dimensional MoO₃The crystals were not completely reacted. The temperature of 800 ℃ is relatively low, the sublimation speed is very low, although the reaction lasts for 120min, a large amount of powder remains in the porcelain boat, and a side reaction for generating Mo particles can occur, so that equivalent precursor MoO cannot be obtained₂Nanosheets.

Example 3

With the precursor MoO₂The preparation processes of the nano sheets are different, and Mo/MoO is prepared₂In the case of in-plane junction, precursor MoO₂Directly participate in the reaction as a reactant,therefore, the roasting time is the reduction reaction time, and the parameter directly influences the reduction degree. The influence of the mixed gas flow rate on the reaction is relatively small, and the reduction rate is determined by the partial pressure of the reducing hydrogen and the calcination temperature. Therefore, the final reduction effect can be regulated and controlled by cooperatively controlling three parameters of the roasting time, the hydrogen partial pressure and the roasting temperature. It is easy to understand that when the firing temperature is controlled to be low. In the macro scale-up experiment, the precursor MoO₂The ultra-high specific surface area of the nanosheets, and in order to ensure that the reducing hydrogen is in full contact with the nanosheets, the application suggests that a quartz tube with a large diameter is adopted to fully spread the precursor. To ensure that the reaction was controlled, in a specific example, the experiment was carried out using a quartz tube with a diameter of 2.5cm, the precursor MoO was controlled₂The mass of the precursor is 5mg, and the total flow rate of the mixed gas is 100sccm to prepare a precursor Mo/MoO₂And (4) forming an in-plane junction.

To illustrate the effect of the above parameters on the reaction, the present application designed the following experiments: weighing the precursor MoO₂Placing the nano-sheets in a porcelain boat, reacting for 300min in a slide rail tube furnace at 400 ℃ under the hydrogen and argon mixed atmosphere of 20/80sccm, and collecting a product; weighing the precursor MoO₂Placing the nano-sheets in a porcelain boat, reacting for 90min in a slide rail tube furnace at 550 ℃ under the hydrogen-argon mixed atmosphere of 20/80sccm, and collecting a product; weighing the precursor MoO₂Placing the nano-sheets in a porcelain boat, reacting for 10min in a slide rail tube furnace at 700 ℃ under the hydrogen-argon mixed atmosphere of 20/80sccm, and collecting the product. As shown in FIG. 9, the diffraction patterns of all three samples contained MoO₂And diffraction signals of the two phases Mo. The sample reacted at 400 ℃ for 300min contained only a very trace amount of Mo, which indicates that the boundary temperature at 400 ℃ is relatively low, the reduction reaction is particularly slow, and the sample only undergoes very light reduction. Due to the Mo/MoO obtained at this time₂The main phase of the in-plane nodule is MoO₂The electrocatalytic hydrogen production performance of the sample is only slightly improved. The reaction is controllable at moderate 550 ℃, the in-plane junction content can be controlled only by regulating and controlling the reaction time, and the optimal sample reacts at 550 ℃ for 90min to obtain the ideal Mo/MoO₂The in-plane junction material, in which the host phase is Mo, also exhibitsThe electro-catalytic hydrogen evolution performance of ampere level is provided. At the relatively high reaction temperature of 700 ℃, the reduction speed is high, the in-plane bonding material with the reduction degree equivalent to that of the optimal condition can be obtained only in 10min, and the performance improvement amplitude of the material is moderate. It is likely that the lattice of the sample will be reconstructed at high temperatures, resulting in less in-plane stress.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.