CN105731463B - A kind of preparation method and application of molybdenum carbide micron ball - Google Patents

Abstract

The invention discloses a preparation method of molybdenum carbide microspheres, comprising the following steps: (1) adding a strong basic anion exchange resin into a molybdate solution, stirring and reacting at normal temperature, washing with water, and suction filtering to obtain molybdenum ion-resin The composite is dried to obtain ion-exchange resin microspheres containing molybdenum; (2) the ion-exchange resin microspheres containing molybdenum obtained in step (1) are placed in a ceramic crucible, under the protection of an inert gas, at 700 Roasting at ~1000°C for 1 to 4 hours, then cooling naturally to room temperature to obtain molybdenum carbide microspheres. The invention also discloses the application of the molybdenum carbide microspheres in electrolyzing water to produce hydrogen. The preparation condition of the present invention is low, the raw material is cheap and easy to obtain, and the prepared molybdenum carbide microsphere has electrochemical activity with low catalytic overpotential and good stability.

Description

A kind of preparation method and application of molybdenum carbide microsphere

technical field

The invention relates to the field of catalysts, in particular to a preparation method and application of molybdenum carbide microspheres.

Background technique

Due to the abundance of hydrogen energy resources, wide sources, high combustion calorific value of hydrogen, clean and pollution-free, it has attracted more and more attention from scientists from all over the world. Hydrogen production by electrolysis of water is currently the most mature, easy-to-industrialize, and environmentally friendly method. The traditional hydrogen production by electrolyzing water is to load the electrolytic water catalyst powder on the conductive electrode through the binder to electrolyze water to produce hydrogen. The problem with this mode is that the supported catalyst is easy to fall off, and the binder will also reduce the activity of the electrocatalyst, especially in the case of high loading. Molybdenum carbide is a highly efficient catalyst widely used in electrolysis of water to produce hydrogen and hydrodesulfurization and other fields. The traditional method of synthesizing molybdenum carbide requires a complex process, the size and shape of which are uncontrollable, and irregular molybdenum carbide powders are obtained, which need to be loaded on various carriers or pressed to form before they can be used in catalytic reactions.

Contents of the invention

In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the object of the present invention is to provide a preparation method of molybdenum carbide microspheres, the raw materials are cheap, the process is simple, porous molybdenum carbide microspheres with high catalytic activity are obtained, and powder catalyst loading is avoided. And subsequent molding and other shortcomings, to achieve the suspension electrocatalytic reaction.

The object of the present invention is achieved through the following technical solutions:

A preparation method of molybdenum carbide microspheres, comprising the following steps:

(1) Add the strong basic anion exchange resin into the molybdate solution, stir and react at room temperature for 12 to 48 hours, wash with water and filter with suction to obtain the molybdenum ion-resin complex, and obtain the ion exchange resin microparticles containing molybdenum after drying. ball;

(2) Place the molybdenum-containing ion-exchange resin microspheres obtained in step (1) into a ceramic crucible, and under the protection of an inert gas, bake at 700-1000° C. for 1-4 hours, and cool naturally to room temperature to obtain carbonized Molybdenum microspheres.

The mass ratio of the strongly basic anion exchange resin to the molybdate in the step (1) is 1-10.

The strongly basic anion exchange resin described in the step (1) is one of 201×4, 201×7, 202, 213, D201, and D202 type anion exchange resins.

The molybdate solution in step (1) is ammonium molybdate, potassium molybdate or sodium molybdate.

Step (2) roasting at 700-1000°C for 1-4 hours, specifically:

Raise the temperature to 700-1000° C. at a rate of 1-10° C./min and bake for 1-4 hours.

The application of the molybdenum carbide microspheres is for electrolyzing water to produce hydrogen.

The molybdenum carbide microspheres are used as a catalyst for suspending electrolysis of water to generate hydrogen, and are added to the electrolyte in the cathode chamber of the electrocatalytic water splitting device for hydrogen generation.

The suspended electrocatalytic water splitting hydrogen production device includes an electrolytic cell, the electrolytic cell is provided with a proton exchange membrane separating the electrolytic cell into an anode chamber and a cathode chamber; the proton exchange membrane is arranged obliquely, and the lower end is attached to the bottom of the electrolytic cell , the upper end is attached to the top of the electrolytic cell; the anode chamber is positioned above the proton exchange membrane, the side wall of the anode chamber is provided with an anode, and the top of the anode chamber is provided with an oxygen outlet; the cathode chamber is positioned below the proton exchange membrane, and the cathode A cathode is provided at the bottom of the chamber, and a hydrogen outlet is provided at the top of the cathode chamber.

In the application of the molybdenum carbide microspheres, the cathode is pasted on the bottom of the electrolytic cell.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The preparation method of the molybdenum carbide microspheres of the present invention requires low preparation conditions, and the raw materials are cheap and easy to obtain, which not only solves the problem of environmental pollution, but also obtains an electrocatalyst with high catalytic activity.

(2) The molybdenum carbide microspheres prepared by the method for preparing molybdenum carbide microspheres of the present invention have electrochemical activity with low catalytic overpotential and good stability.

(3) Apply the molybdenum carbide microspheres prepared by the present invention to electrolysis of water for hydrogen production, which can suspend electrocatalyzed water splitting reaction, solve the problem of electrocatalyst without binder loading and reuse, and realize high current in the process of electrolysis of water for hydrogen evolution reaction Technical goals of density, high stability and high catalytic efficiency.

Description of drawings

Fig. 1 is the XRD spectrum of the molybdenum carbide obtained by roasting at 900 degrees Celsius after the ion exchange reaction in Example 1 of the present invention.

2 is a scanning electron micrograph of molybdenum carbide microspheres obtained by roasting at 900 degrees Celsius in Example 1 of the present invention.

Fig. 3 is a partially enlarged scanning electron micrograph of molybdenum carbide microspheres obtained by roasting at 900 degrees Celsius in Example 1 of the present invention.

Fig. 4 is a schematic diagram of the suspended electrocatalytic water splitting device in Example 1 of the present invention.

Fig. 5 is a schematic diagram of hydrogen production by suspension electrolysis of water according to Embodiment 1 of the present invention.

Fig. 6 is a polarization curve diagram of molybdenum carbide microspheres as a catalyst in Example 1 of the present invention.

Fig. 7 is a time-current graph of the electrocatalytic hydrogen production reaction of molybdenum carbide microspheres in Example 1 of the present invention.

Fig. 8 is an X-ray diffraction diagram of molybdenum carbide synthesized at 1000 degrees Celsius in Example 2 of the present invention.

Fig. 9 is a scanning electron micrograph of molybdenum carbide synthesized at 1000 degrees Celsius in Example 2 of the present invention.

Fig. 10 is the polarization curve result of molybdenum carbide synthesized at 1000 degrees Celsius in Example 2 of the present invention.

Fig. 11 is a morphological diagram of the mixture of molybdenum carbide and molybdenum dioxide synthesized at 800 degrees Celsius in Example 4 of the present invention.

Fig. 12 is the X-ray powder diffraction result of the mixture of molybdenum carbide and molybdenum dioxide synthesized at 800 degrees Celsius in Example 4 of the present invention.

Fig. 13 is the specific surface area of molybdenum dioxide synthesized at 700 degrees Celsius in Example 3 of the present invention obtained through nitrogen adsorption and desorption tests.

Fig. 14 is a Raman spectrum of molybdenum carbide powder synthesized at 900 degrees Celsius in Example 5 of the present invention.

Fig. 15 is peak C of the X-ray photoelectron spectrum of molybdenum carbide powder synthesized at 900 degrees Celsius in Example 5 of the present invention.

Figure 16 is the Mo3d peak in the X-ray photoelectron spectrum of the molybdenum carbide powder synthesized at 900 degrees Celsius in Example 5 of the present invention.

Fig. 17 is the time-current curve of molybdenum carbide synthesized at 900 degrees Celsius in Example 5 of the present invention.

Fig. 18 is the impedance result of molybdenum carbide synthesized at 900 degrees Celsius in Example 5 of the present invention.

detailed description

The present invention will be described in further detail below in conjunction with the examples, but the embodiments of the present invention are not limited thereto.

Example 1

Weigh 5 grams of D201 type anion exchange resin and add to 20 milliliters, 0.5 mole per liter of sodium molybdate solution, add a stirring bar and stir for 24 hours at room temperature. Slowly add the solution into a suction filter bottle for suction filtration, and dry the obtained solid at 100° C. for 24 hours to obtain an ion exchange resin adsorbing molybdenum ions. Put the obtained powder into a ceramic crucible, place it in an atmosphere tube furnace, and under the protection of nitrogen gas, heat up to 900 °C at a heating rate of 5 °C per minute in the tube type furnace for 2 hours, and cool naturally to room temperature to obtain molybdenum carbide Microspheres. The microspheres are characterized by X-ray electron diffraction as a molybdenum carbide component, as shown in Figure 1; the microsphere shape is observed by a scanning electron microscope, with a diameter of 200-500 microns (as Figure 2), and the surface of the microspheres has a granular composition, with Porous structure (Figure 3).

As shown in Figure 4, the electrocatalytic water splitting device of this embodiment includes an electrolytic cell, which is a cylindrical structure, the body wall is made of glass, the bottom is sealed, the top is a plastic sleeve cap, and an oxygen outlet 1 and a hydrogen outlet 2 are provided; The electrolytic cell is provided with a proton exchange membrane 5 that separates the electrolytic cell into an anode chamber 3 and a cathode chamber 4; Pasted on the plastic cover cap; the anode chamber 3 is located above the proton exchange membrane 5, the anode 6 adopts square sheet carbon cloth, is arranged on the side wall of the anode chamber 3, and the hydrogen outlet 1 is located on the top of the anode chamber 3; The cathode chamber 4 is located below the proton exchange membrane 5, and the cathode 7 adopts a disc-type titanium sheet, which is identical in shape to the bottom of the electrolytic cell and attached to the bottom of the electrolytic cell. The hydrogen outlet 2 is located on the top of the cathode chamber 4. The electrocatalyst molybdenum carbide microspheres 8 are dispersed in the electrolyte solution.

Add 5 grams of the above-mentioned molybdenum carbide microspheres as the electrocatalyst into the cathode chamber of the above-mentioned electrocatalytic water splitting device, use the sulfuric acid aqueous solution with a concentration of 0.5 moles per liter as the electrolyte, and a circular titanium sheet with a diameter of 5 cm as the cathode. The 5 cm circular carbon cloth is the anode, the middle is the acidic proton exchange membrane, and the electrolytic cell is made of glass.

As shown in Figure 5, the principle of molybdenum carbide microsphere suspension electrocatalytic water splitting in this embodiment is as follows:

Strongly basic anion exchange resin itself contains strong basic functional groups, which can dissociate hydroxides in water, molybdate anions exchange with hydroxide anions, and adsorb and combine with positively charged groups in the resin to produce anion exchange. The resin obtained after the ion exchange reaction is calcined and carbonized at a high temperature to obtain molybdenum carbide microspheres maintaining a spherical structure. Then transfer the molybdenum carbide microspheres to a suspension type electrolysis water hydrogen evolution device using 0.5 mol per liter of sulfuric acid as the electrolyte, wherein the hydrogen production working electrode is at the bottom of the electrolytic cell. By applying an appropriate voltage, the molybdenum carbide microspheres have an upward buoyancy due to the adsorption of hydrogen generated by the catalytic reaction. When the gravity Fg and the buoyancy _Fb are equal in magnitude, they will be suspended; at the same time, the molybdenum carbide microspheres are in contact with each other Collisions between the electrodes make the hydrogen bubbles fall off and sink to the bottom electrode. There is no fixed load relationship between the molybdenum carbide microspheres and the electrode, which can realize simple electrocatalyst replacement. The two processes of molybdenum carbide microspheres floating and settling in the electrolyte are continuously converted to achieve efficient hydrogen production by suspending electrolyzed water.

Using linear voltammetry scanning to test its polarization curve as shown in Figure 6, it has a low electrolyzed water hydrogen production overpotential, and its value is 75 millivolts; using time-current method to test its catalytic current density with the change of reaction time, catalytic reaction 10 There is no decrease in the catalytic current density after 4 hours, showing good cycle stability (Figure 7).

Example 2

Weigh 2g of 201×4 type anion exchange resin and add it into 40 ml of sodium molybdate solution with 2 moles per liter, add a stirring bar and stir for 12 hours at normal temperature. The obtained solution was filtered with suction, and the obtained solid was dried at 100° C. for 48 hours. Under the protection of argon gas, the obtained solid was heated up to 1000°C at a heating rate of 5°C/min and roasted at a high temperature for 2 hours, and then cooled naturally to room temperature to obtain molybdenum carbide microspheres. The X-ray diffraction results are shown in Figure 8; molybdenum carbide was obtained by grinding and pulverizing The morphology is shown in Figure 9.

Using the molybdenum carbide prepared in this example as the electrocatalyst, the result of its polarization curve is shown in Figure 10, and the hydrogen production overpotential is 0.22 volts.

Example 3

The preparation steps are the same as in Example 1, except that the anion exchange resin is D202 type, and the temperature is raised to 800° C. for 2 hours in a tube furnace at a heating rate of 5° C. per minute. The morphology of the obtained molybdenum carbide microspheres is shown in Figure 11, and the X-ray powder diffraction results are shown in Figure 12. The specific surface area obtained by the nitrogen adsorption and desorption test is 42.8 square meters per gram (Figure 13), indicating that the molybdenum carbide microspheres are porous structures.

Example 4

The preparation steps are the same as in Example 1, except that the calcination temperature is changed to 900°C. It was confirmed by Raman characterization that the electrocatalyst consists of molybdenum carbide and crystalline carbon, as shown in Figure 14.

The powder prepared in this example is characterized by photoelectron spectroscopy, as shown in Figure 15 and Figure 16, it can be seen that the electrocatalyst is composed of tetravalent molybdenum and carbon, which confirms the successful synthesis of molybdenum carbide.

The molybdenum carbide prepared in this example was used as the electrocatalyst, and the time-current curve (as shown in Figure 17) was used to test and show that the molybdenum carbide had good hydrogen production stability.

Using the molybdenum carbide prepared in this example as the electrocatalyst, the electrochemical impedance results of the prepared molybdenum carbide are shown in Figure 18. The results show that the molybdenum carbide has a small impedance value, and the impedance gradually decreases as the voltage increases.

Above-mentioned embodiment is preferred embodiment of the present invention, but embodiment of the present invention is not limited by described embodiment, also can be 201 * 7, 202, 213 type as strong basic anion exchange resin of the present invention or Other anion exchange resins; Molybdate can also be other molybdates of potassium molybdate or ammonium molybdate; Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be Equivalent replacement methods are all included in the protection scope of the present invention.

Claims (7)

1. a kind of preparation method of molybdenum carbide micron ball, it is characterised in that comprise the following steps：

(1) strong-base anion-exchange resin is added in molybdate solution, stirring reaction 12~48 hours, pass through water under normal temperature Wash, filter and obtain molybdenum ion-resin complexes, the ion exchange resin beads containing molybdenum element are obtained after drying；

(2) ion exchange resin beads containing molybdenum element that step (1) obtains are placed in ceramic crucible, protected in inert gas Under shield, it is warming up to 700~1000 DEG C with 1~10 DEG C/min of programming rate and is calcined 1~4 hour, naturally cool to room temperature, obtain To the molybdenum carbide microballoon that homogeneous diameter is 200~500 microns；

The mass ratio of strong-base anion-exchange resin and molybdate described in step (1) is 1~10.

2. the preparation method of molybdenum carbide micron ball according to claim 1, it is characterised in that the highly basic described in step (1) Property anion exchange resin be 201 × 4,201 × 7,202,213, one kind in D201, D202 type anion exchange resin.

3. the preparation method of molybdenum carbide micron ball according to claim 1, it is characterised in that step (1) described molybdate Solution is ammonium molybdate, potassium molybdate or sodium molybdate.

4. the molybdenum carbide micron ball that the preparation method of any one of claims 1 to 3 molybdenum carbide micron ball is prepared is answered With, it is characterised in that for being electrolysed aquatic products hydrogen, the electro-catalysis Xie Shui that can suspend reactions.

5. the application of molybdenum carbide micron ball according to claim 4, it is characterised in that the molybdenum carbide micron ball is as electricity The catalyst of aquatic products hydrogen is solved, in the electrolyte for the cathode chamber for being added to electro-catalysis solution aquatic products hydrogen production device.

6. the application of molybdenum carbide micron ball according to claim 5, it is characterised in that the electro-catalysis solution aquatic products hydrogen production device Including electrolytic cell, the PEM that electrolytic cell is divided into anode chamber and cathode chamber is provided with the electrolytic cell；The proton Exchange membrane is obliquely installed, and lower end is affixed on the bottom of electrolytic cell, and upper end is affixed on the top of electrolytic cell；The anode chamber is located at proton friendship The top of film is changed, the side wall of anode chamber is provided with anode, and the top of anode chamber is provided with oxygen outlet；The cathode chamber is located at proton friendship The lower section of film is changed, the bottom of cathode chamber is provided with negative electrode, and the top of cathode chamber is provided with hydrogen outlet.

7. the application of molybdenum carbide micron ball according to claim 6, it is characterised in that the negative electrode is affixed on the bottom of electrolytic cell In portion.