TWI422431B - Preparation method of cobalt composite catalyst - Google Patents

Description

Preparation method of cobalt composite catalyst

The invention belongs to a preparation method of a catalyst, in particular to a method for catalytic hydrogen production by using a cobalt metal as a composite catalyst for chemical hydrogen storage materials.

Hydrogen energy is one of the most considerable alternative energy sources. It is the cleanest fuel in fuel cells. It does not produce greenhouse gases or other harmful substances in the conversion process. Zero emission is its most characteristic, so it is the most valuable energy. Several ways of storing hydrogen have been developed, among which the chemical hydrogen storage method has great development potential.

In the chemical hydrogen system, the material selection for practical application must consider four major parts: a. material price, b. safety, c. material efficiency, d. stability. The performance of sodium borohydride in all of them meets the requirements. The advantages of applying it to the fuel cell hydrogen supply system are as follows:

1. NaBH _{4 has} high solubility and is easy to prepare into a solution.

2. The NaBH ₄ solution is stable under alkaline conditions and can be stored for several months without deterioration.

3. The reaction of hydrogen in NaBH ₄ solution has higher hydrogen storage efficiency than the reaction of other chemical hydrogen, and the reaction rate of this reaction is easy to control.

4. The only by-product (NaBO ₂ ) of this reaction has high solubility and is easily soluble in water, so that clean hydrogen can be directly obtained, and NaBO ₂ can be recycled to form NaBH ₄ .

5. Under the specific catalyst reaction, NaBH ₄ can generate a large amount of hydrogen in a short time. The gas product is hydrogen and water vapor, and the hydrogen gas is in a wet state and can be directly supplied to the fuel cell for reaction.

6. Hydrogen can be produced even at 0 °C.

Sodium borohydride is the most widely studied chemical hydrogen since it is formulated into an alkaline solution with the above advantages. In 2002, Millennium Battery Company successfully developed sodium borohydride chemical hydrogen as raw material, and matched the design of the system to actually supply hydrogen to the fuel cell. Therefore, the development of methods and technologies for the use of catalytic materials to promote the reaction of sodium borohydride with water to produce hydrogen, the industrial value derived from it will be unlimited.

Hydrogen-catalyzed by nano-cobalt metal, as revealed by Qingdao University of Science and Technology, China [ Int. J. Hydrogen Energy 33 , 7731 (2008)], which uses activated carbon [HNO ₃ ] to modify activated carbon to make its surface hydrophilic. Functionality of sex. Next, the precursor cobalt nitrate solution is impregnated, and due to the increase of the hydrophilic functional group, the activated carbon can capture more metal cobalt, and the active position of the catalytic ability increases. However, since it requires the use of activated carbon, it is necessary to additionally use a carrier. Furthermore, the activated carbon still needs to be surface-modified functional groups to increase the amount of metal impregnated on the surface of the activated carbon, and there are still limitations in its process. However, the carrier iron of the present invention does not require surface modification to simplify the process of the catalyst. Furthermore, in [ Factor Cells 10 , 132 (2010)], it was first revealed that a nanocomposite catalyst synthesized from cobalt and an iron bimetal is used for the hydrogen production reaction of sodium borohydride. When the cobalt to iron molar ratio is 17 to 3, it has the maximum activity, and its price is reduced by the substitution of iron. However, the process simplification and price still have room for further decline. Thereby, the present invention synthesizes a nanocomposite catalyst which replaces cobalt metal with more iron, and achieves commercial value of cost reduction.

In view of the above disadvantages of the prior art, the main object of the present invention is to provide a method for preparing a cobalt composite catalyst, which utilizes an iron-containing compound, a cobalt-containing compound, and The reducing agent is made into a hydrogen-producing cobalt composite nanocatalyst to achieve process simplification and cost reduction.

In order to achieve the above object, the present invention provides a method for preparing a cobalt composite catalyst, which comprises the steps of providing an iron-containing compound and a cobalt-containing compound, adding the iron-containing compound to a reducing agent, and then adding the cobalt-containing compound to the iron-containing solution. An iron-cobalt mixture is obtained in the middle, and then a reducing agent is added to the iron-cobalt mixture to form a cobalt composite catalyst. The purpose of adding the reducing agent is mainly to reduce the metal ions in the catalyst to metal atoms to form nano-sized particles. The invention is characterized in that instead of using any precious metal, cobalt metal is used as an active center, and iron is used as a carrier to increase the active area of the cobalt particles, thereby further simplifying the process and reducing the cost.

In the examples of the present invention, the components of the hydrogen-producing catalyst and the preparation method thereof will also be explained. The catalyst is a composite nanoparticle supported on iron particles with cobalt as an active center, wherein the iron-containing compound is a ferric chloride (FeCl ₃ ‧6H ₂ O) as a precursor; the cobalt-containing compound is a cobalt chloride (CoCl ₂ ‧6H ₂ O) is a precursor and is synthesized using sodium borohydride (NaBH ₄ ) as a reducing agent.

The hydrogen production activity test uses hydrogen to have little solubility in water, and the hydrogen collection method can be used to collect hydrogen gas, and the amount of production and relative time can be measured to know the hydrogen production rate. This method can compare hydrogen production by different catalysts. rate. Since sodium borohydride is highly reactive with water, the addition of sodium hydroxide acts as a stabilizer in the solution, which slows the reaction rate of sodium borohydride with water and prolongs the storage life of the sodium borohydride solution.

The above summary and the following detailed description and drawings are for the purpose of The manner, means and efficacy of the present invention for achieving the intended purpose are explained in one step. Other objects and advantages of the present invention will be described in the following description and drawings.

The embodiments of the present invention are described below by way of specific examples, and those skilled in the art can readily appreciate the other advantages and advantages of the present invention.

Referring to Fig. 1, the present invention is a method for preparing a cobalt composite catalyst, the steps of which include: step (A): providing an iron-containing compound and a cobalt-containing compound (S101), using deionized water as The solvent is disposed as an aqueous solution containing iron and a solution containing cobalt; step (B): adding the iron-containing compound to a reducing agent (S102), the reducing environment is a neutral aqueous phase, and the reducing agent is added under rotation of the stirring device; (C): adding a cobalt-containing compound to the iron-containing solution to obtain a mixture of iron and cobalt (S103); and (D): providing a reducing agent to the iron-cobalt mixture to form a cobalt composite catalyst (S104), The reducing environment is a neutral aqueous phase, and the reducing agent is added while the stirring is rotating.

In order to take out the cobalt composite catalyst, another three steps are further proposed: step (E): using magnetic adsorption catalyst powder; step (F): filtering out the cobalt composite catalyst by filtration; step (G) The cobalt composite catalyst is dried and dried to remove unnecessary solvent, and the catalyst particles are ground to average particle size. Thereby, preparing a hydrogen catalyst for chemical hydrogen storage materials, using cobalt metal as an active center, and The use of iron as a carrier to increase the active area of the cobalt particles further simplifies the process and reduces the cost.

Embodiment 1:

100 ml of a 0.02 M ferric chloride (FeCl ₃ ‧6H ₂ O) solution was placed in a reaction flask, and the prepared reducing agent sodium borohydride (NaBH ₄ ) solution was added dropwise at 500 rpm with a stir bar. The solution in the reaction flask was gradually turned grayish black and allowed to stand for 24 hours. Another 100 ml of a 0.02 M cobalt chloride (CoCl ₂ ‧6H ₂ O) solution was added to the above reaction flask solution. The prepared reducing agent sodium borohydride (NaBH ₄ ) solution was dropped at a stirring speed of 500 rpm and allowed to stand for 24 hours. This solution was sucked by a magnet to the product gray-black powder, which was a catalyst powder. The catalyst powder was filtered five times with deionized water to ensure that the impurities were washed, dried and ground to obtain a fine black catalyst powder. The X-ray diffraction pattern (Fig. 2) shows that the catalyst synthesized is an amorphous phase structure.

The hydrogen production activity test method is as follows: a 5 wt% sodium borohydride (NaBH ₄ ) solution and a weight percent concentration of 5 wt% sodium hydroxide (NaOH) solution are prepared in deionized water, and a hydrogen production device is set up to set a constant temperature. The bath temperature was 298 K at room temperature. Weigh a suitable amount of about 10 mg of catalyst into a round bottom single-necked flask, then inject 5 wt% sodium borohydride (NaBH ₄ ) solution and 10 wt% sodium hydroxide (NaOH) solution into 10 ml, at which time a large number of bubbles generate this bubble. That is, hydrogen gas, the amount of production can be recorded on the graduated scale. It is found that the average hydrogen production rate of the iron-cobalt core-shell catalyst nanoparticles is 2200 (ml/g.min), and if compared with the hydrogen production rate of cobalt metal catalyst particles of 2500 (ml/g.min), The hydrogen production activity is comparable, as shown in Figure 3. However, if the price factor is considered, the nanoparticle catalyst supported on the iron of the cobalt of the present invention is cheaper than the conventional pure cobalt catalyst because it contains iron.

The above-described embodiments are merely illustrative of the features and functions of the present invention, and are not intended to limit the scope of the technical scope of the present invention. Modifications and variations of the above-described embodiments can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be as set forth in the scope of the claims described below.

S101~S104‧‧‧ is the process of cobalt composite catalyst

Fig. 1 is a schematic view showing the preparation process of the cobalt composite catalyst of the present invention.

Fig. 2 is a X-ray diffraction pattern before and after hydrogen production of the cobalt composite catalyst of the first embodiment of the present invention.

Fig. 3 is a graph comparing the hydrogen production rate activity of the cobalt composite catalyst and the cobalt metal particles according to the first embodiment of the present invention.

S101~S104‧‧‧ is the process of cobalt composite catalyst

Claims (7)

A method for preparing a cobalt composite catalyst, comprising the steps of: (A) providing an iron-containing compound and a cobalt-containing compound dissolved in water to form an iron-containing solution and a cobalt-containing solution; (B) adding the iron-containing solution a sodium borohydride solution; (C) adding the cobalt-containing solution to the iron-containing solution to obtain a mixed solution of iron and cobalt; (D) providing the sodium borohydride solution to the iron-cobalt mixed solution to form a metal cobalt support in the nanometer a composite catalyst on the metal iron particles; thereby controlling a concentration combination of the cobalt-containing solution, the iron-containing solution, and the sodium borohydride solution to achieve the active center of the metal cobalt, and using the nano-metal iron as a carrier The active area of the metal cobalt particles is increased to carry out a hydrogen production reaction. A method for preparing a cobalt composite catalyst according to the first aspect of the invention, wherein the iron-containing compound is one of a group of ferric chloride, iron nitrate, iron acetate or a combination thereof. A method for preparing a cobalt composite catalyst according to the first aspect of the invention, wherein the cobalt-containing compound is one of the group of cobalt chloride, cobalt nitrate, cobalt acetate or a combination thereof. A method for preparing a cobalt composite catalyst according to the first aspect of the invention, wherein the reducing agent concentration is from 1% by weight to 10% by weight. A method for preparing a cobalt composite catalyst according to the first aspect of the patent application, wherein the cobalt-containing compound has a concentration of 0.01 M to 0.05 M. A method for preparing a cobalt composite catalyst according to the first aspect of the patent application, wherein the concentration of the iron-containing compound is from 0.01 M to 0.05 M. For example, in the preparation method of the cobalt composite catalyst according to the first aspect of the patent application, in order to take out the cobalt composite catalyst, another three steps are further proposed: the step (E) is to utilize the magnetic adsorption catalyst powder; the step (F) is to use the filtration. The cobalt composite catalyst is filtered out; and the cobalt composite catalyst is dried and ground in step (G).