Porous gas diffusion electrode for fuel battery and preparing method thereof

Abstract

Each component constituting electrode catalysis layer is in gradient distribution in Z direction of electrode (perpendicular to direction of catalysis layer). In macroscopy, electrode catalysis layer is in structure of multiple layers for example at least divided into two layers structure. First layer structure as partial hydrophobic catalysis layer composed of first catalytic activity metal, water repellent and conducting ionic polymer. Second layer structure as hydrophilic catalysis layer composed of second catalytic activity metal and conducting ionic polymer. Composite two layers constitute partial hydrophobic and partial hydrophilic composite electrode. Advantages of the structure of electrode are: enhancing capability of mass transfer of gas, especially when air as oxidant, meanwhile keeping enough capability of electron conduction and proton transfer; extending effective triphase interface of catalytic reaction; raising output power density.

Description

field of invention [0001] The invention relates to a fuel cell, in particular to a porous gas diffusion electrode for the fuel cell and a method for preparing the electrode. Background technique [0002] A fuel cell is a device that directly converts chemical energy into electrical energy. The electrode is an important part of it and the main place for electrochemical reactions; the electrode is generally composed of a diffusion layer and a catalytic layer. [0003] The characteristics of the fuel cell greatly depend on the structure of the gas diffusion electrode, especially the structure of the catalytic layer; since the electrochemical reaction is carried out on the three-phase interface on the surface of the electrocatalyst, the reaction point has the electrocatalyst, electrolyte and hydrogen or oxygen, and the electrocatalyst The three-phase interface of the chemical reaction is confined at the two-dimensional boundary of the electrocatalyst and the electrolyte, reducin...

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Problems solved by technology

The third method is that the catalyst is first mixed with PTFE to prepare a catalytic layer, and then sprayed on the above-mentioned catalytic layer with a conductive ionic resin to realize the three-dimensionalization of the catalytic layer (see US P-4876115 for details), which is a traditional hydrophobic electrode preparation process; this process The advantage is that the preparation process is simple and the repeatability is good. The disadvantages are that the contact surface between the conductive ion polymer and the electrochemical catalyst is small, the utilization rate of the electrochemical catalyst is low, and the proton conduction resistance is large, which restricts the performance of the fuel cell.

[0004] The biggest defect of the above-mentioned several processes is that under the condition of high current density operation, the mass transfer capacity of the gas, especially when air is used as the oxidant, is insufficient, which reduces the limiting current and power density of the fuel cell operation.

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