Membrane electrode catalyst layer with gradient pore structure as well as preparation method and application of membrane electrode catalyst layer

Abstract

The invention relates to a membrane electrode catalyst layer with a gradient pore structure and a preparation method and application thereof, the catalyst layer comprises a macroporous layer (11), a microporous layer (12) and a noble metal catalyst, and the microporous layer (12) is close to one side of a proton exchange membrane (2); the noble metal catalyst comprises a large catalyst and a small catalyst; the macroporous layer (11) comprises a large catalyst; and a small catalyst is contained in the small hole layer (12). At least one transition layer is arranged between the macroporous layer (11) and the microporous layer (12), and the transition layer comprises a large catalyst and a small catalyst. A plurality of transition layers are arranged, and the mass fraction of the large catalyst in each transition layer is gradually reduced layer by layer along the direction from the large hole layer (11) to the small hole layer (12). Compared with the prior art, the method has the advantages that the wetting of the catalyst layer and the proton conduction capability in the catalyst layer are ensured, and the battery performance is high.

Description

technical field [0001] The invention relates to the field of membrane electrode catalytic layers, in particular to a membrane electrode catalytic layer with a gradient pore structure and a preparation method and application thereof. Background technique [0002] As the core component of the fuel cell, the membrane electrode mainly consists of a proton exchange membrane, a catalytic layer and a diffusion layer. The catalytic layer is the place where the chemical reaction of the fuel occurs in the membrane electrode. The optimization of its structure and the improvement of its performance have always been research the key of. The catalytic layer is generally composed of Pt particles, carbon supports that can conduct electrons, ionomers that can conduct protons and adhesion (usually Nafion solution) and a large number of pores. [0003] The internal pore structure of the catalytic layer is an important parameter in determining gas transport and water management. The interior ...

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Problems solved by technology

For the CCM preparation process, optimizing the pore structure of the catalytic layer needs to start with the preparation materials of the catalytic layer. Carbon supports, ionomers, and solvents all affect the pores of the catalytic layer. Carbon supports such as Ketjen Black and Vulcan XC-72, The pore size distribution is similar, but the proportion of specific surface area and pore size is different; the addition of ionomer increases the electrochemical reaction active area of ​​the catalytic layer, and effectively conducts protons, improving the utilization rate of the catalyst, but the ionomer in the catalytic layer Too much content will not only cover a large amount of Pt / C particles, hinder electron conduction, but also may block the "primary pores" and "secondary pores" inside the catalytic layer, resulting in the obstruction of the internal water and reaction gas transmission channels, which will greatly weaken the The performance of the battery; the main function of the solvent is to disperse the catalyst layer material and promote the formation of the pore structure, which is related to its viscosity, solubility, volatility, dielectric constant and other properties

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