阅读说明：本技术 一种过渡金属硫化物核壳纳米球析氢催化剂及其制备方法 (Transition metal sulfide core-shell nanosphere hydrogen evolution catalyst and preparation method thereof ) 是由 冀梁 申胜平 于 2020-07-27 设计创作，主要内容包括：本发明公开了一种过渡金属硫化物核壳纳米球析氢催化剂及其制备方法,该电化学析氢催化剂包括导电基底和通过脉冲激光沉积法在基底上生成的催化活性层；该制备方法利用高能脉冲激光束轰击实现靶材从固态—等离子态—固态的转变,从而可在不同基底上形成核壳型纳米球团聚而成的纳米多孔电化学析氢催化剂；通过调控靶基间距、基底转速、沉积温度等制备条件,可获得粒径可控的纳米球团聚型纳米多孔电化学析氢催化剂。通过引入核壳型纳米球使得过渡金属硫化物纳米片在金属单质纳米核上高度弯曲,从而暴露出更多的活性位点,此外还实现了催化活性层导电率与电化学活性反应面积的同步提升。(The invention discloses a transition metal sulfide core-shell nanosphere hydrogen evolution catalyst and a preparation method thereof, wherein the electrochemical hydrogen evolution catalyst comprises a conductive substrate and a catalytic active layer generated on the substrate by a pulse laser deposition method; the preparation method utilizes high-energy pulse laser beam bombardment to realize the conversion of the target material from a solid state to a plasma state to a solid state, thereby forming the nano-porous electrochemical hydrogen evolution catalyst formed by the agglomeration of the core-shell type nanospheres on different substrates; the nanosphere agglomeration type nano-porous electrochemical hydrogen evolution catalyst with controllable particle size can be obtained by regulating and controlling preparation conditions such as target base distance, substrate rotating speed, deposition temperature and the like. The core-shell nanospheres are introduced to enable the transition metal sulfide nanosheets to be highly bent on the metal simple substance nanocore, so that more active sites are exposed, and the synchronous improvement of the conductivity of the catalytic active layer and the electrochemical active reaction area is realized.)

1. A transition metal sulfide core-shell nanosphere hydrogen evolution catalyst is characterized in that the catalyst is of a double-layer film structure and comprises a conductive substrate and a catalytic active layer generated on the conductive substrate by a pulse laser deposition method; the catalytic active layer is formed by bending one or more transition metal sulfide nanosheets on a metal simple substance nano core to form core-shell type nanospheres, and the core-shell type nanospheres with different particle sizes are agglomerated to realize a three-dimensional nano porous structure; the thickness ratio of the catalytic active layer to the conductive substrate is (0.01-0.3): 1; in the electrochemical hydrogen evolution reaction, after hydrogen ions in the electrolyte are embedded into the catalytic active layer, the hydrogen ions are combined with electrons in the catalytic active layer to generate a hydrogen simple substance and water molecules, and the hydrogen simple substance is reacted with the uncombined hydrogen ions and the residual electrons to generate hydrogen and water molecules, so that the aim of water electrolysis and hydrogen evolution is fulfilled.

2. The transition metal sulfide core-shell nanosphere hydrogen evolution catalyst of claim 1, wherein the conductive substrate is a glassy carbon substrate, a metal foil or a polymer film plated with a conductive coating.

3. The transition metal sulfide core-shell nanosphere hydrogen evolution catalyst of claim 1, wherein the metal foil is aluminum foil, silver foil, gold foil, copper foil or tungsten foil.

4. The transition metal sulfide core-shell nanosphere hydrogen evolution catalyst of claim 1, wherein the one or more transition metal sulfide nanosheets are at least 10 times on the elemental metal nanocore^-2nm^-1The high curvature of the stage is bent to form core-shell nanospheres which are agglomerated.

5. The transition of any one of claims 1 to 4The preparation method of the metal sulfide core-shell nanosphere hydrogen evolution catalyst is characterized in that metal simple substance powder with the purity of 99.9-99.99% and the mesh of 80-150 and transition metal sulfide powder with the purity of 99.9-99.95% and the mesh of 80-120 are mixed according to the proportion of 1:2, and then ball milling is carried out for 24-32 hours in a nitrogen environment; filling the mixed powder after ball milling into a die, and pressing for 30-40 hours at 80-100 ℃ to prepare a target material; cold-pressing and rolling the conductive substrate which meets the thickness design requirement for multiple times by using a calender, then carrying out ultrasonic cleaning and vacuum drying on the conductive substrate for 24 hours, and directly carrying out cleaning and drying steps if a glassy carbon substrate is used; cutting the dried conductive substrate into a slender strip meeting the design requirement to be used as a substrate for a pulse laser deposition process, wherein the whole preparation process needs to be finished in a vacuum cavity, inversely fixing the deposition substrate on a heating table, and fixing a target under the heating table according to a preset target substrate interval; in order to make the prepared catalytic active layer more uniform, the heating table drives the deposition substrate to rotate at a certain rotating speed; in order to ensure the service life of the target material, the target material reversely rotates at a rotating speed 15-20 times higher than that of the heating table; then regulating the energy of garnet or krypton fluoride laser to be stable, setting the laser frequency to be 10Hz, carrying out scanning bombardment along the radial direction of the target, and using high-energy laser beam bombardment to realize the conversion of the target from a solid state to a plasma state to a solid state, thereby forming the three-dimensional nano-porous electrochemical hydrogen evolution catalyst formed by the agglomeration of the core-shell type nanospheres on the conductive substrate; before preparation, the air pressure in the vacuum cavity is pumped to 1 × 10^-8～5×10^-8And (3) controlling the temperature to be 25-100 ℃ during preparation, controlling the thickness of the catalytic active layer by controlling the deposition time, and regulating and controlling the target base distance, the substrate rotating speed and the deposition temperature to obtain the three-dimensional nano porous electrochemical hydrogen evolution catalyst with controllable particle size.

Technical Field

The invention relates to the technical field of catalysts, in particular to a transition metal sulfide core-shell nanosphere hydrogen evolution catalyst and a preparation method thereof.

Background

Transition metal sulfide is considered as a material most likely to replace noble metals such as platinum/iridium as an electrochemical hydrogen evolution catalyst due to characteristics of adjustable energy band, near-zero hydrogen adsorption Gibbs free energy, low cost and the like. As representative of transition metal sulfides, molybdenum disulfide and tungsten disulfide are completely different catalytic systems for electrochemical hydrogen evolution catalytic reactions, although they have similar electronic energy bands and structural properties. First, molybdenum disulfide is the most catalytically active in its amorphous state, whereas highly crystalline tungsten disulfide exhibits its optimal catalytic properties. Unlike molybdenum disulfide, tungsten disulfide does not have good catalytic ability in its 2H phase semiconductor state, but exhibits the most excellent catalytic performance in transition metal sulfides after being converted into a 1T phase metallic state. Therefore, further exploration of the electrochemical hydrogen evolution catalyst based on the transition metal sulfide becomes the key point for promoting the progress of the electrolytic water catalytic hydrogen evolution industry.

Nowadays, electrochemical hydrogen evolution catalysts based on transition metal sulphides face the following problems: firstly, the catalytic active layer itself has weak conductivity and poor electrical contact with the substrate; secondly, sparse active sites on the atomic basal plane; thirdly, the tiled and stacked structure of the nanosheets causes the ion-embedded blocking effect. In order to solve the above three problems, researchers have proposed three catalyst optimization projects, i.e., active site project, phase change project, and conductivity project, one after another. The three optimization projects are all used for enabling the electrochemical hydrogen evolution catalyst to have lower reaction potential, smaller Tafel slope, longer durability and larger current density. For active site engineering, in addition to creating atomic defects using argon plasma bombardment, mechanical factors such as strain and curvature have also been used in recent years to create atomic defects and sulfur vacancies. On the other hand, the phase change engineering and the conductivity engineering are often inseparable, for example, when the transition metal sulfide is converted from 2H phase to 1T phase, the conductivity is often increased greatly. Other synthetic means such as doping and hybridization are also used to enhance the electrochemical catalytic performance of transition metal sulfides. However, none of these efforts has been able to simultaneously enhance the conductivity of the catalytically active layer with the number of active sites therein.

Disclosure of Invention

The invention aims to provide a transition metal sulfide core-shell nanosphere hydrogen evolution catalyst and a preparation method thereof, and aims to solve the technical problems of poor conductivity and sparse active sites of a catalytic active layer in the background technology.

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

a transition metal sulfide core-shell nanosphere hydrogen evolution catalyst is of a double-layer film structure and comprises a conductive substrate and a catalytic active layer generated on the conductive substrate by a pulse laser deposition method; the catalytic active layer is formed by bending one or more transition metal sulfide nanosheets on a metal simple substance nano core to form core-shell type nanospheres, and the core-shell type nanospheres with different particle sizes are agglomerated to realize a three-dimensional nano porous structure; the thickness ratio of the catalytic active layer to the conductive substrate is (0.01-0.3): 1; in the electrochemical hydrogen evolution reaction, after hydrogen ions in the electrolyte are embedded into the catalytic active layer, the hydrogen ions are combined with electrons in the catalytic active layer to generate a hydrogen simple substance and water molecules; the simple substance of hydrogen reacts with the uncombined hydrogen ions and the residual electrons to generate hydrogen and water molecules, thereby realizing the aim of hydrogen evolution by electrolyzing water.

Furthermore, the conductive substrate is a glassy carbon substrate, an aluminum foil, a silver foil, a gold foil, a copper foil, a tungsten foil or a polymer film plated with a conductive coating.

The one or more transition metal sulfide nanosheets are arranged on the metal elementary substance nanometer core by 10^-2nm^-1The high curvature of the stage is bent to form core-shell nanospheres which are agglomerated.

The invention also provides a transition metal sulfideThe preparation method of the core-shell nanosphere hydrogen evolution catalyst comprises the steps of mixing metal simple substance powder with the purity of 99.9-99.99% and the mesh of 80-150 with transition metal sulfide powder with the purity of 99.9-99.95% and the mesh of 80-120 according to the proportion of 1:2, and then carrying out ball milling for 24-32 hours in a nitrogen environment; filling the mixed powder after ball milling into a die, and pressing for 30-40 hours at 80-100 ℃ to prepare a target material; cold-pressing and rolling the conductive substrate which meets the thickness design requirement for multiple times by using a calender, and then carrying out ultrasonic cleaning and vacuum drying on the conductive substrate for 24 hours (if a glassy carbon substrate is used, the steps of cleaning and drying are directly carried out); cutting the dried conductive substrate into a slender strip meeting the design requirement to be used as a substrate for a pulse laser deposition process, wherein the whole preparation process needs to be finished in a vacuum cavity, inversely fixing the deposition substrate on a heating table, and fixing a target under the heating table according to a preset target substrate interval; in order to make the prepared catalytic active layer more uniform, the heating table drives the deposition substrate to rotate at a certain rotating speed; in order to ensure the service life of the target material, the target material reversely rotates at a rotating speed 15-20 times higher than that of the heating table; then regulating the energy of garnet or krypton fluoride laser to be stable, setting the laser frequency to be 10Hz, carrying out scanning bombardment along the radial direction of the target, and using high-energy laser beam bombardment to realize the conversion of the target from a solid state to a plasma state to a solid state, thereby forming the three-dimensional nano-porous electrochemical hydrogen evolution catalyst formed by the agglomeration of the core-shell type nanospheres on the conductive substrate; before preparation, the air pressure in the vacuum cavity is pumped to 1 × 10^-8～5×10^-8And (3) controlling the temperature to be 25-100 ℃ during preparation, controlling the thickness of the catalytic active layer by controlling the deposition time, and regulating and controlling the target base distance, the substrate rotating speed and the deposition temperature to obtain the three-dimensional nano porous electrochemical hydrogen evolution catalyst with controllable particle size.

The invention introduces core-shell nanospheres and transition metal sulfide nanosheets of which the number is 10^-2nm^-1High curvature of the stage is curved; this will greatly increase the number of unbound sulfur vacancies and atomic defects. In addition, the conductivity of the catalytic active layer can be greatly improved by the metal elementary substance nano-core with ultrahigh conductivity inside.According to the invention, the three-dimensional nano porous structure is generated by agglomerating the core-shell type nanospheres, and the method is beneficial to solving the problem of site closure existing in the two-dimensional nano sheet stacked structure. Compared with the prior art, the invention has the advantages that:

(1) the nanosphere agglomeration type nano-porous electrochemical hydrogen evolution catalyst with controllable particle size can be obtained by regulating and controlling preparation conditions such as target base distance, substrate rotating speed, deposition temperature and the like. The problems of few active sites and poor conductivity of a catalytic active layer of the traditional transition metal sulfide electrochemical hydrogen evolution catalyst are solved; by introducing the core-shell nanospheres, the transition metal sulfide nanosheets are highly bent on the metal simple substance nanocore, so that more active sites are exposed; the conductivity of the catalytic active layer and the number of active sites are synchronously improved, and the electrochemical hydrogen evolution catalyst has larger active reaction area; the catalyst has wide application prospect in the fields of electrolytic water catalytic hydrogen evolution and the like;

(2) the electrochemical hydrogen evolution catalyst has the advantages of simple preparation process, strong catalytic performance of products, high stability and durability and low cost, and can promote transition metal sulfide to replace noble metals such as platinum, iridium and the like to be used as the electrochemical hydrogen evolution catalyst for large-scale use.

Drawings

Fig. 1 is a schematic diagram of preparation and an atomic structure diagram of a transition metal sulfide core-shell nanosphere hydrogen evolution catalyst.

FIG. 2 is a cross-sectional and surface scanning electron microscope image of a high-performance tungsten @ tungsten disulfide core-shell nanosphere hydrogen evolution catalyst.

Fig. 3a and fig. 3b are mercury intrusion test desorption curves and pore size distribution diagrams of the nano-porous hydrogen evolution catalyst formed by the agglomeration of the core-shell nanospheres respectively.

Fig. 4 is a high resolution transmission electron microscope image of a high performance tungsten @ tungsten disulfide core-shell nanosphere hydrogen evolution catalyst.

Fig. 5a is a transmission electron microscope image of a high-performance tungsten @ tungsten disulfide core-shell nanosphere hydrogen evolution catalyst, fig. 5b is a composition overlapping image of elemental sulfur and elemental tungsten, fig. 5c is a distribution diagram of elemental sulfur, and fig. 5d is a distribution diagram of elemental tungsten.

Fig. 6a, 6b, 6c and 6d are graphs of the X-ray diffraction, raman spectra and X-ray photoelectron spectroscopy analysis results of tungsten 4f and sulfur 2p regions, respectively, of the high performance tungsten @ tungsten disulfide core-shell nanosphere hydrogen evolution catalyst.

Figure 7 is a hydrogen evolution polarization curve for a tungsten disulfide based core shell nanosphere hydrogen evolution catalyst.

Figure 8 is a tafel plot of a tungsten disulfide based core shell nanosphere hydrogen evolution catalyst.

Fig. 9a and 9b are a plot of polarization curve contrast and a plot of chronoamperometric results for a highly durable molybdenum @ molybdenum disulfide core shell nanosphere hydrogen evolution catalyst, respectively.

Figure 10 is a nyquist plot of the electrochemical impedance spectrum of a highly conductive molybdenum @ molybdenum disulfide core shell nanosphere hydrogen evolution catalyst.

Fig. 11a and 11b are current-voltage curves and current density-scan rate curves, respectively, for highly capacitive tungsten @ tungsten disulfide core shell nanosphere hydrogen evolution catalysts.

Detailed Description

The present invention will now be described in detail with reference to the drawings and specific embodiments, wherein the exemplary embodiments and descriptions of the present invention are provided to explain the present invention without limiting the invention thereto.