阅读说明：本技术 一种高分散性燃料电池催化剂浆料及制备方法 (High-dispersity fuel cell catalyst slurry and preparation method thereof ) 是由 陈庆 廖健淞 于 2019-10-08 设计创作，主要内容包括：本发明提出一种高分散性燃料电池催化剂浆料及制备方法,所述催化剂浆料是先将聚乙烯醇溶解于去离子水中,然后加入活性炭并水浴加热搅拌,接着降低水浴温度并加入2,3-环氧丙基三甲基氯化铵继续搅拌,再用氢氧化钠溶液调节pH值后加入氯铂酸,混合均匀后继续使用氢氧化钠溶液调节pH值至中性,加入还原剂静置,接着离心分离得到固体产物,最后与丙二醇胺以质量比1：10分散得到。本发明提供的醚化改性的聚乙烯醇具有分散、增稠效应,并且对铂粒子的吸附能力强,将铂还原至碳载体表面,从而有效提高铂粒子在催化剂浆料中的分散性能,同时制备方法无高温高压,条件温和,适宜于工业化放大生产。(The invention provides a high-dispersibility fuel cell catalyst slurry and a preparation method thereof, wherein the catalyst slurry is prepared by dissolving polyvinyl alcohol in deionized water, adding activated carbon, heating and stirring in a water bath, reducing the temperature of the water bath, adding 2, 3-epoxypropyltrimethylammonium chloride, continuously stirring, adjusting the pH value with a sodium hydroxide solution, adding chloroplatinic acid, uniformly mixing, continuously adjusting the pH value to be neutral with the sodium hydroxide solution, adding a reducing agent, standing, centrifugally separating to obtain a solid product, and mixing with propylene glycol amine according to a mass ratio of 1: 10 are dispersed. The etherified modified polyvinyl alcohol provided by the invention has dispersing and thickening effects, has strong adsorption capacity to platinum particles, and reduces platinum to the surface of a carbon carrier, so that the dispersing performance of the platinum particles in catalyst slurry is effectively improved.)

1. The high-dispersity fuel cell catalyst slurry is characterized in that polyvinyl alcohol is dissolved in deionized water, then activated carbon is added, water bath heating and stirring are carried out, then the water bath temperature is reduced, 2, 3-epoxypropyltrimethylammonium chloride is added, stirring is continued, the pH value is adjusted by using a sodium hydroxide solution, chloroplatinic acid is added, after uniform mixing, the pH value is adjusted to be neutral by using the sodium hydroxide solution, a reducing agent is added, standing is carried out, centrifugal separation is carried out to obtain a solid product, and finally the solid product and propylene glycol are mixed according to the mass ratio of 12: 1 is obtained by dispersing.

2. The highly dispersible fuel cell catalyst slurry according to claim 1, wherein the sodium hydroxide solution has a mass concentration of 8-10%.

3. The highly dispersible fuel cell catalyst slurry according to claim 1, wherein the reducing agent is one of a formaldehyde solution, hydrazine hydrate, and a sodium borohydride solution, the mass concentration of the formaldehyde solution is 10-30%, and the mass concentration of the sodium borohydride solution is 15-25%.

4. The method for preparing a highly dispersible fuel cell catalyst slurry according to any one of claims 1 to 3, wherein the method comprises the following steps:

(1) dissolving polyvinyl alcohol (PVA) in deionized water, adding activated carbon, heating in water bath to 95 ℃, stirring for 15min, reducing the temperature of the water bath to 60 ℃, adding 2, 3-epoxypropyltrimethylammonium chloride (GTMAC), and continuously stirring for 15min to obtain a mixed solution;

(2) slowly dropwise adding a sodium hydroxide solution into the mixed solution, adjusting the pH value to 8-9, then stirring for 30min, then adding a proper amount of chloroplatinic acid, continuously stirring for 5min, uniformly mixing, adjusting the pH value to be neutral by using the sodium hydroxide solution, then standing for 24h, adding a reducing agent, standing for 12h, and finally centrifugally separating to remove a clear solution to obtain a solid product;

(3) mixing the obtained solid product with propylene glycol in a mass ratio of 1: 10, dispersing to obtain the required high-dispersity fuel cell catalyst slurry.

5. The method as claimed in claim 4, wherein the stirring speed in step (1) is 150-250 rpm.

6. The method as claimed in claim 4, wherein the stirring speed in step (2) is 150-200 rpm.

7. The method for preparing the highly dispersible fuel cell catalyst slurry according to claim 4, wherein in the step (2), the solid product is prepared by mixing polyvinyl alcohol, 2, 3-epoxypropyltrimethylammonium chloride, activated carbon, chloroplatinic acid and deionized water in a mass ratio of 0.1-3.5: 0.5-5: 5-10: 0.5-5: 100.

8. the method for preparing a highly dispersible fuel cell catalyst slurry according to claim 4, wherein the reducing agent is used in an excessive amount in the preparation of the catalyst slurry in the step (2).

Technical Field

The invention relates to the technical field of fuel cell catalysts, in particular to high-dispersity fuel cell catalyst slurry and a preparation method thereof.

Background

The fuel cell is a power generation device which directly converts chemical energy of fuel into electric energy in an electrochemical reaction mode without combustion, is a new technology which efficiently utilizes energy and does not pollute the environment, is widely applied to various fields of fuel cell power stations, electric automobiles, high-efficiency portable power supplies and the like, and has extremely wide application prospect.

The components of the fuel cell mainly comprise a catalyst, an electrolyte membrane, a gas diffusion layer, a membrane electrode assembly, a bipolar plate, a fuel cell stack and the like. The catalyst is one of the key materials of the fuel cell, and has the functions of reducing the activation energy of the reaction, promoting the oxidation-reduction process of hydrogen and oxygen on the electrode and improving the reaction rate. Most of the existing catalyst slurry is stirred in an organic solvent through Pt/C particles, and the phenomenon of catalyst particle agglomeration is difficult to avoid in the preparation process.

The slurry preparation process is often complicated, and agglomeration is easily caused in the slurry preparation process due to the small particle size of Pt/C particles, so that the catalytic performance is poor and Pt is wasted. In the prior art, the order of the added catalyst and the added auxiliary agent is controlled to stir at a high speed, so that hydrogen bonds and van der Waals forces among particles are destroyed, and the aim of dispersing slurry is fulfilled. However, the shearing and stirring force caused by the homogenizer and the emulsifier is not ideal for destroying the hydrogen bond effect among particles, especially when the particle size of the slurry is small, the slurry is difficult to be effectively dispersed and the secondary agglomeration and sedimentation of the slurry are inhibited, and the process is long in time consumption and high in energy consumption, so that the catalyst cost is not reduced. Therefore, further improvement and perfection are required for the problems of poor dispersing property of the catalyst slurry and serious agglomeration.

The Chinese patent application No. 201611063880.2 discloses a preparation method of a fuel cell membrane electrode catalyst slurry. The method comprises the following steps: (1) adding catalyst particles, water, a high molecular polymer proton conductor solution, a Teflon solution, alcohol and a thickening agent in sequence, and mixing; (2) firstly, stirring by using a magnetic stirrer; then continuously stirring by using a shearing emulsifying machine or a homogenizer; finally, oscillating by ultrasonic waves; catalyst slurry was obtained. The Chinese patent application No. 201210193830.1 discloses a fuel cell catalyst slurry and a preparation method thereof, wherein the catalyst slurry comprises the following raw materials in percentage by weight: 1-40% of solid particle catalyst, 0.1-30% of high molecular polymer proton conductor, 1-60% of water, 1-60% of C1-4 lower alcohol and 0.1-30% of high molecular polymer dispersant, wherein the high molecular polymer dispersant is one or a mixture of more than two of polyvinylpyrrolidone, polyvinyl alcohol, sodium carboxymethylcellulose, polyethylene oxide and polyacrylamide.

In order to solve the problems of poor material dispersibility and serious agglomeration in the fuel cell catalyst slurry, a novel fuel cell catalyst slurry is needed, and the dispersibility of the material in the fuel cell catalyst slurry is obviously improved.

Disclosure of Invention

Aiming at the problem that the current fuel cell catalyst material has poor dispersion performance, the invention provides the high-dispersion fuel cell catalyst slurry and the preparation method thereof, so that the dispersion and thickening effects of the catalyst slurry are effectively realized, and the platinum particles have good dispersion in the catalyst slurry.

In order to solve the problems, the invention adopts the following technical scheme:

a high-dispersity fuel cell catalyst slurry is prepared by dissolving polyvinyl alcohol in deionized water, adding activated carbon, heating in a water bath, stirring, reducing the temperature of the water bath, adding 2, 3-epoxypropyltrimethylammonium chloride, continuously stirring, adjusting the pH value with a sodium hydroxide solution, adding chloroplatinic acid, uniformly mixing, continuously adjusting the pH value to be neutral with the sodium hydroxide solution, adding a reducing agent, standing for 12 hours, carrying out centrifugal separation to obtain a solid product, and mixing the obtained solid product with propylene glycol in a mass ratio of 1: 10 are dispersed.

Preferably, the mass concentration of the sodium hydroxide solution is 8-10%.

Preferably, the reducing agent is one of formaldehyde solution, hydrazine hydrate and sodium borohydride solution.

Further preferably, the mass concentration of the formaldehyde solution is 10-30%, and the mass concentration of the sodium borohydride solution is 15-25%.

The invention also provides a preparation method of the high-dispersity fuel cell catalyst slurry, which comprises the following steps:

(1) dissolving polyvinyl alcohol (PVA) in deionized water, adding activated carbon, heating in water bath to 95 ℃, stirring for 15min, reducing the temperature of the water bath to 60 ℃, adding 2, 3-epoxypropyltrimethylammonium chloride (GTMAC), and continuously stirring for 15min to obtain a mixed solution;

(2) slowly dropwise adding a sodium hydroxide solution into the mixed solution, adjusting the pH value to 8-9, then stirring for 30min, then adding a proper amount of chloroplatinic acid, continuously stirring for 5min, uniformly mixing, adjusting the pH value to be neutral by using the sodium hydroxide solution, then standing for 24h, adding a reducing agent, standing for 12h, and finally centrifugally separating to remove a clear solution to obtain a solid product;

(3) mixing the obtained solid product with propylene glycol in a mass ratio of 1: 10, dispersing to obtain the required high-dispersity fuel cell catalyst slurry.

Preferably, the stirring speed in the step (1) is 150-250 rpm.

Preferably, the stirring speed in the step (2) is 150-200 rpm.

Preferably, in the preparation of the solid product in the step (2), the mass ratio of the polyvinyl alcohol, the 2, 3-epoxypropyltrimethylammonium chloride, the activated carbon, the chloroplatinic acid and the deionized water is 0.1-3.5: 0.5-5: 5-10: 0.5-5: 100.

preferably, in the preparation of the catalyst slurry in the step (3), the reducing agent is used in excess to ensure that chloroplatinic acid is sufficiently reduced.

The invention firstly carries out etherification modification on polyvinyl alcohol (PVA), and the principle of the etherification modification is mainly to introduce corresponding monomers to carry out etherification on hydroxyl by utilizing the chemical activity of PVA hydroxyl, and alkali liquor is generally selected as a catalyst. Under alkaline conditions, the etherification reaction of PVA is mainly beta-cracking reaction, and is a result of steric hindrance effect generated by hydroxyl newly generated after the etherification agent reacts with PVA and original ether bond of the etherification agent; simultaneously, the alpha-cracking side reaction is also carried out; in addition, there is no alcoholysis of-OCOCH in PVA₃Irreversible saponification reactions may occur; the hydroxyl groups on the side chains may undergo etherification crosslinking reaction with an etherifying agent. Modification of the PVA surface by etherification results in the formation of a more positively charged, para [ PtCl ]₆]^2-The particles have strong adsorption capacity, and the modified organic matter has dispersing and thickening effects. The invention selects sodium hydroxide with mass concentration of 8-10% and selects 2, 3-epoxypropyltrimethylammonium chloride (GTMAC) as a solid active cation etherifying agent.

Further, the etherified modified PVA is adsorbed on the surface of the carbon carrier in the aqueous solution by simple mechanical stirringA simple reducing agent reduces the platinum to the carbon support surface. Carbon surface grafted modified PVA (polyvinyl alcohol) pair [ PtCl ]₆]^2-The particles have stronger adsorption capacity, the charge density of the surface of the modified PVA is very high, so that the stability and the reaction rate in the adsorption process are improved, the adsorption process is shortened, and smaller particles are formed in the [ PtCl ]₆]After the 2-particles are reduced into the Pt nano particles, the Pt nano particles can more easily permeate into the pores of the activated carbon instead of being agglomerated on the surface, so that the coverage of the Pt on the inner surface of the activated carbon is effectively improved, and the effective dispersion of the Pt nano particles is realized. Meanwhile, the mutual exclusion capacity among the active carbon particles is improved due to the coating of the organic phase on the surface of the carbon powder, and the suspension capacity of the solid particles in the slurry is improved due to the thickening effect of the coating layer. Therefore, the dispersibility of the catalyst slurry can be effectively improved.

The existing fuel cell catalyst material has the defect of poor dispersion performance, and the application of the existing fuel cell catalyst material is limited. In view of the above, the invention provides a high-dispersibility fuel cell catalyst slurry and a preparation method thereof, PVA is dissolved in deionized water, activated carbon is added and heated in a water bath to 95 ℃ and stirred for 15min, the temperature of the water bath is reduced to 60 ℃, GTMAC is added and stirred for 15min again, then sodium hydroxide solution is slowly dripped to adjust the pH value to 8-9, stirring is carried out for 30min at the rotating speed of 150 plus materials and 200r/min, a proper amount of chloroplatinic acid is added and stirred for 5min and is uniformly mixed, and then the pH value is adjusted to be neutral by using the sodium hydroxide solution. Adding an excessive reducing agent for reduction, centrifugally separating to remove a clear liquid, and mixing the obtained solid product with propylene glycol in a mass ratio of 1: 10, and obtaining the required catalyst slurry. The etherified modified polyvinyl alcohol provided by the invention has dispersing and thickening effects, has strong adsorption capacity to platinum particles, and reduces platinum to the surface of a carbon carrier, so that the dispersing performance of the platinum particles in catalyst slurry is effectively improved.

Compared with the prior art, the invention provides the high-dispersity fuel cell catalyst slurry and the preparation method thereof, and the outstanding characteristics and excellent effects are as follows:

1. the invention carries out etherification reaction on PVA through GTMAC to ensure that modified organic matters are inHas dispersing and thickening effects and is simultaneously para [ PtCl6]^2-The particles have stronger adsorption effect, the etherified and modified PVA is adsorbed on the surface of the carbon carrier through simple mechanical stirring, and platinum is reduced to the surface of the carbon carrier by soaking the particles with a reducing agent, so that the dispersion performance of the platinum particles in the catalyst slurry is effectively improved.

2. The preparation method of the invention has no high temperature and high pressure and mild conditions, and is suitable for industrial scale-up production.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.