阅读说明：本技术 一种膜电极中催化剂层的制备方法 (Preparation method of catalyst layer in membrane electrode ) 是由 刘征 陈孟杰 舒正龙 乔红艳 陈启章 于 2020-05-26 设计创作，主要内容包括：本发明涉及新能源材料与在燃料电池汽车的应用领域,特别涉及一种膜电极中催化剂层的制备方法。所述催化剂层包括聚酰胺-胺树形分子包裹的纳米贵金属催化剂和表面功能化导电碳黑,与现有技术相比,本发明的有益效果：聚酰胺-胺树形分子作为模板剂能更好地在原子、分子水平上控制催化剂的纳米粒子结构、大小及分布,可大大提高贵金属的利用率,从而提高燃料电池的性能和降低成本；表面功能化导电碳黑与PGM-DENC通过酰胺共价交联形成PGM(C)-DENC,提高了催化剂的导电性。(The invention relates to the field of new energy materials and application in fuel cell automobiles, in particular to a preparation method of a catalyst layer in a membrane electrode. Compared with the prior art, the catalyst layer comprises a polyamide-amine dendrimer coated nano noble metal catalyst and surface functionalized conductive carbon black, and the catalyst layer has the beneficial effects that: the polyamide-amine dendrimer is used as a template agent, so that the structure, size and distribution of the nano particles of the catalyst can be better controlled at the atomic and molecular levels, and the utilization rate of noble metal can be greatly improved, thereby improving the performance of the fuel cell and reducing the cost; the surface functionalized conductive carbon black and PGM-DENC are covalently cross-linked through amide to form PGM (C) -DENC, so that the conductivity of the catalyst is improved.)

1. The catalyst layer comprises a nano noble metal catalyst and conductive carbon black, and is characterized in that the mass ratio of the conductive carbon black to the nano noble metal catalyst is 0.01-1%, the nano noble metal catalyst is a nano noble metal catalyst wrapped by polyamide-amine dendrimer, and the conductive carbon black is surface functionalized conductive carbon black.

2. A catalyst layer according to claim 1, wherein the conductive carbon black is prepared by: adding conductive carbon black into an acid solution for acidification treatment, then carrying out esterification or anhydride modification on the conductive carbon black, separating, washing and filtering, and drying the obtained filtrate to obtain the surface functionalized conductive carbon black.

3. The slurry for preparing the catalyst layer is characterized by comprising a nano noble metal catalyst and conductive carbon black, and further comprising an ionic crosslinking polymer and isobutanol serving as a solvent.

4. A method of preparing a slurry according to claim 3, comprising the steps of: adding the polyamide-amine dendrimer coated nano noble metal catalyst and the surface functionalized conductive carbon black into an N-hydroxysuccinimide aqueous solution, stirring for reaction to obtain a carbon-modified polyamide-amine dendrimer coated nano noble metal catalyst, performing ultrasonic dispersion in deionized water, then dropwise adding the carbon-modified polyamide-amine dendrimer coated nano noble metal catalyst into the deionized water according to the sequence of firstly preparing an isobutanol solvent, then preparing an aqueous solution of an ionomer, and finally supplementing the isobutanol solvent, and stirring for reaction to obtain a catalyst layer slurry.

5. A method of preparing a slurry according to claim 3, comprising the steps of: ultrasonically dispersing a polyamide-amine dendrimer coated nano noble metal catalyst in deionized water, then adding the deionized water according to the sequence of firstly adding an isobutanol solvent and then an aqueous solution of an ionomer into the deionized water, uniformly stirring, adding an N-hydroxysuccinimide aqueous solution containing surface functionalized conductive carbon black, then supplementing the isobutanol solvent and stirring to obtain catalyst layer slurry.

6. The method for producing slurry according to claim 4 or 5, wherein the mass ratio of the ionomer to the surface-functionalized conductive carbon black particles is from 0.3 to 1: 1.

7. the method of producing a slurry according to claim 4 or 5, characterized in that the solid content of the catalyst layer slurry is 5 to 10%.

8. A catalysed membrane electrode comprising a catalyst layer according to claims 1 to 5.

9. The catalyzed membrane electrode of claim 8, wherein the catalyst layer comprises a cathode catalyst layer and an anode catalyst layer, the cathode catalyst layer having a precious metal loading of 0.1 ± 0.02mg/cm²The noble metal loading of the anode catalyst layer is 0.25 +/-0.02 mg/cm²。

Technical Field

The invention relates to the field of new energy materials and application in fuel cell automobiles, in particular to a preparation method of a catalyst layer in a membrane electrode.

Background

A fuel cell is a power generation device that directly converts chemical energy thereof into electric energy without a combustion process, electrochemical reactions occur at electrodes on both sides, and an electrocatalyst coated on the electrodes is used to promote an electrochemical oxidation reaction of fuel occurring at an anode and a reduction reaction of oxygen occurring at a cathode. Among the Fuel cells, Proton Exchange Membrane (PEM) Fuel cells (PEMFC) have recently received wide market attention due to their characteristics of high power density, fast start-up speed, low operating temperature, and environmental friendliness. The energy density is high, the starting speed is high, the low-temperature stable operation is realized, the operation temperature is low, the environment is friendly, and the like, so that the energy-saving power supply is very suitable for serving as a power source of an electric automobile, a portable small power supply, a power supply of an underwater power system, and the like. Therefore, since the nineties of the last century, the technology has been rapidly developed due to the wide attention of governments and energy sources, automobiles, household appliances, military industry and the like.

The Membrane Electrode Assembly (MEA) is the main part of the proton exchange membrane fuel cell, and comprises a five-layer structure, wherein the central layer is a proton exchange membrane, two catalyst layers separated by a membrane are arranged on two sides of the central layer to form a catalytic membrane electrode with a cathode and an anode, and the catalytic membrane electrode plays an important role in the process of converting the chemical energy of the fuel cell into the electric energy; there are two gas diffusion layers outside the catalytic membrane electrode, which are mainly used to transport reactants (fuel, air) to the membrane electrode and remove the product-water.

In the current commercial membrane electrode assembly, the catalyst layer is mostly made of the traditional precious metal (PGM) Pt/C electrocatalyst, but the precious metal has limited reserves on the earth, is expensive, has low utilization rate in the fuel cell, and hinders the commercialization process of the proton exchange membrane fuel cell. Over the past several decades, numerous researchers have been working on new generation membrane electrode assemblies and catalyzed membrane electrodes with high efficiency, low precious metal (PGM), high durability. Based on the aim, the invention provides a catalytic membrane electrode and a preparation method of a catalyst layer, which is a key component of the catalytic membrane electrode, through a novel high-efficiency catalyst synthesis technology, aims to improve the performance of the catalytic membrane electrode of the fuel cell and reduce the cost, and provides a novel process technical route for key parts of the fuel cell, the catalytic membrane electrode and the catalyst layer thereof.

Disclosure of Invention

The invention aims to overcome the defects of high consumption and low utilization rate of noble metals in a proton exchange membrane fuel cell in the prior art, and provides a catalyst layer, slurry, a preparation method and a catalytic membrane electrode (CCM) prepared by the catalyst layer and the slurry.

The invention provides the following technical scheme:

a catalyst layer comprises a nano noble metal catalyst and conductive carbon black, the mass ratio of the conductive carbon black to the nano noble metal catalyst is 0.01% -1%, preferably 0.1% -0.5%, the nano noble metal catalyst is a polyamide-amine dendrimer coated nano noble metal catalyst, and the conductive carbon black is surface functionalized conductive carbon black.

The purpose of the functionalization of the conductive carbon black is to more effectively bind with the catalyst, thereby increasing the conductivity of the catalyst.

According to the invention, the polyamide-amine dendrimer is used as a template agent and a stabilizer, the prepared catalyst layer has a controllable nano structure and particle size, and the utilization rate of noble metals is improved; the conductivity of the catalyst is improved by modifying the conductive carbon black.

Wherein, the nanometer noble metal catalyst is prepared by the following method: and (2) carrying out a complex reaction on the polyamide-amine dendrimer and a noble metal compound, adding a reducing agent for a reduction reaction, and separating, washing and drying to obtain the nano noble metal catalyst wrapped by the polyamide-amine dendrimer.

Specifically, according to the method reported in the literature, a commercial polyamidoamine dendrimer is subjected to pretreatment and then redispersed in deionized water to form an aqueous solution with a certain concentration, then a certain PGM/PAMAM molar ratio (the ratio is more than 40) and a certain concentration of noble metal acid or salt aqueous solution are added under stirring until metal ions are completely complexed by the PAMAM dendrimer to form metal ions wrapped in the PAMAM dendrimer, and then excessive NaBH is added dropwise under vigorous stirring at a certain temperature (0-25 ℃), so that the PAMAM dendrimer is dissolved in the aqueous solution₄(0.3-0.5M in 0.1-0.3M NaOH), and stirring until the noble metal ions are completely reduced, separating, washing and drying the obtained solution to finally obtain the Dendrimer-coated Nano metal Catalyst, which is defined as PGM-DENC (Dendrimer-Encapsulated-Nano-Catalyst), and repeating the above technical route to obtain the required particle size of the nanoparticles.

Preferably, the conductive carbon black is prepared by the following method: adding conductive carbon black into an acid solution for acidification treatment, then carrying out esterification or anhydride modification on the conductive carbon black, separating, washing and filtering, and drying the obtained filtrate to obtain the surface functionalized conductive carbon black.

A slurry for preparing a catalyst layer is characterized by comprising a nano noble metal catalyst and conductive carbon black, and further comprising an ion cross-linked polymer (Ionermer) and isobutanol serving as a solvent.

Preferably, the slurry for preparing the catalyst layer is prepared by the steps of:

PGM-DENC and surface functionalized conductive carbon black are added into N-hydroxysuccinimide (NHS) aqueous solution, and are stirred to react to obtain a carbon-modified polyamide-amine dendrimer coated nano noble metal catalyst, which is named PGM (C) -DENC, and the PGM-DENC is ultrasonically dispersed in deionized water, and then Isobutanol (IPA) solvent and ion cross-linked polymer (Ionermer) solution are added, wherein the ion cross-linked polymer used in the invention is 10 wt.% aqueous solution of perfluorosulfonic acid (Nafion), and finally the isobutanol solvent is supplemented and is sequentially added into the deionized water in a dropwise manner, and the catalyst layer slurry is stirred to react to obtain the catalyst layer slurry.

Preferably, another preparation method of the slurry for preparing the catalyst layer is as follows:

ultrasonically dispersing PGM-DENC in deionized water, then adding the deionized water in the order of firstly an isobutanol solvent and then a solution of an ionomer (Ionermer), uniformly stirring, adding an N-hydroxysuccinimide (NHS) aqueous solution containing surface functionalized conductive carbon black, then supplementing and adding the isobutanol solvent, and stirring to obtain catalyst layer slurry.

Preferably, the mass ratio of the ionomer (ionirmer) to the surface-functionalized conductive carbon black particles is 0.3-1: 1.

preferably, the solid content of the catalyst layer slurry is 5 to 10%.

The prepared fresh catalyst layer slurry can be directly used for preparing the catalytic membrane electrode, and can also be stored for 3-4 days at 0-20 ℃ for use.

A catalytic membrane electrode comprises the catalyst layer, wherein the catalyst layer is prepared in a form of slurry and sprayed on the catalytic membrane electrode, and specifically, the slurry is prepared in the two preferable modes.

Preferably, the catalyst layer comprises a cathode catalyst layer and an anode catalyst layer, and the noble metal loading of the cathode catalyst layer is 0.1 +/-0.02 mg/cm²The noble metal loading of the anode catalyst layer is 0.25 +/-0.02 mg/cm²。

Respectively and directly coating anode and cathode catalyst layers on two sides of a commercial Proton Exchange Membrane (PEM) by the catalyst layer slurry through an ultrasonic sprayer to prepare a catalytic membrane electrode; the PEM is a perfluorosulfonic acid ion exchange membrane, the catalyst slurry is ultrasonically sprayed and deposited on the proton exchange membrane layer by layer under stirring, and the catalytic membrane electrode (CCM) is finally prepared by drying and hot pressing.

Compared with the prior art, the invention has the beneficial effects that:

the polyamide-amine dendrimer is used as a template agent, the nano structure, the particle size and the distribution of the catalyst can be better controlled at the atom and molecule levels, and the utilization rate of noble metal can be greatly improved, so that the performance of the fuel cell is improved, and the cost is reduced.

The surface functionalized conductive carbon black and PGM-DENC are covalently cross-linked through amide to form PGM (C) -DENC, so that the conductivity of the catalyst is improved.

The catalyst slurry prepared by the slurry preparation process has good stability and fluidity.

Description of the drawings:

FIG. 1 is a synthesis scheme of PGM-DENC;

FIG. 2 is a synthesis scheme of modification of conductive carbon black particles and PGM (C) -DENC;

figure 3 is a graph of performance testing of single fuel cells of the catalyzed mea of examples 1-4.

Detailed Description

The present invention will be described in further detail with reference to test examples and specific embodiments. It should be understood that the scope of the above-described subject matter is not limited to the following examples, and any techniques implemented based on the disclosure of the present invention are within the scope of the present invention.

The conductive carbon Black used in the invention is Vulcan XC-72R, XC-72 (American CARBOTS CORPORATION), Black pearls 2000 (American CARBOTS CORPORATION), acetylene Black, Ketjen Black series conductive carbon Black (Japanese lion king company)

The polyamide-amine dendrimer used in the invention is the 4 th-10 th generation PAMAM;

abbreviations for reagents:

PAMAM, polyamidoamine;

PEMFCs, proton exchange membrane fuel cells;

PGM, noble metals;

PGM-DENC, a nano noble metal catalyst wrapped by polyamide-amine dendrimer;

pgm (c) -DENC, conductive carbon black coated noble metal electrocatalyst;

MES, 2- (N-morpholine) ethanesulfonic acid;

NHS, N-hydroxysuccinimide.