Fuel Cell Membrane Electrode (MEA)

Fuel Cell Membrane Electrode – Fuel Cell Catalyst Coatings – Cheersonic

The fuel cell stack is the “heart” of the fuel cell system, and the core component of the fuel cell is the MEA. The performance of the MEA directly affects the performance of the fuel cell stack and even the entire fuel cell system.

fuel cell structure

The process of converting chemical energy into electrical energy in a fuel cell is as follows:

1. The anode plate flow transports hydrogen to the anode, and the cathode plate flow channel transports oxygen to the cathode;
2. Hydrogen is catalytically oxidized, releasing electrons and forming hydrogen ions. The hydrogen ions pass through the wet proton exchange membrane to the cathode side, and the electrons are conducted to the cathode side through an external circuit;
3. Oxygen on the cathode side is reduced by electrons and reacts with hydrogen ions passing through the proton exchange membrane to generate water and discharge.

The membrane electrode (MEA), also known as the membrane electrode “three-in-one” or “five-in-one” component, is the core component of the proton exchange membrane fuel cell and the place for the internal energy conversion of the fuel cell. The membrane electrode is responsible for the transport of heterogeneous substances (liquid water, hydrogen, oxygen, protons and electrons) in the fuel cell, and is responsible for converting the chemical energy of hydrogen into electrical energy through electrochemical reactions.

The performance and cost of membrane electrodes determine the performance, life and cost of proton exchange membrane fuel cells. Membrane electrodes with efficient multiphase transport capabilities can greatly improve the performance of fuel cells.

MEA cost

The main cost components of fuel cell vehicles include traditional vehicle components such as fuel cell systems, on-board hydrogen supply systems, power batteries, and vehicle frames. Among them, the fuel cell system is the core component of the fuel cell vehicle, accounting for more than 60% of the vehicle cost. The fuel cell system includes a fuel cell stack, an air compressor, a hydrogen circulation pump, etc., of which the membrane electrode is the core component of the fuel cell, accounting for about 30% of the cost of the entire system.

Structural composition of MEA

The membrane electrode (MEA) is mainly composed of a proton exchange membrane, a catalytic layer and a gas diffusion layer.

proton exchange membrane
The main function of the proton exchange membrane in the fuel cell is to realize the rapid conduction of protons, and also to block the permeation of hydrogen, oxygen and nitrogen between the cathode and anode. The performance of the proton exchange membrane directly determines the performance and service life of the fuel cell. An ideal proton exchange membrane needs to have high proton conductivity, low electronic conductivity, low gas permeability, and good chemical, electrochemical, and thermal stability.

Proton exchange membranes are classified according to the fluorine content, mainly including perfluorosulfonic acid membranes, partially fluorinated polymer proton exchange membranes, composite proton exchange membranes and non-fluorinated polymer proton exchange membranes.

Among them, because the perfluorosulfonic acid polymer has a polytetrafluoroethylene structure, the bond energy of its carbon-fluorine bond is high, its mechanical properties, chemical stability, and thermal stability are good, and its service life is also better than that of other membrane materials. At the same time, due to the presence of hydrophilic sulfonic acid groups on the molecular branches, which have excellent ion conductivity, perfluorosulfonic acid membranes have become the mainstream proton exchange membrane solutions.

Proton exchange membrane technology solution catalyst

The catalytic layer is an important part of the membrane electrode. The anode uses a catalyst to promote the oxidation reaction of hydrogen, which involves various processes such as oxidation reaction, gas diffusion, electron movement, proton movement, and water migration. The cathode uses a catalyst to promote the reduction reaction of oxygen, which involves the reduction of oxygen, the diffusion of oxygen, the movement of electrons, the movement of protons, and the discharge of water produced by the reaction.

A good catalyst should have good catalytic activity, high proton conductivity, high electron conductivity, and good water management and gas diffusion capabilities.

catalyst preparation process

At present, the optimal catalysts are still Pt and Pt-based catalysts. The commonly used commercial catalysts are Pt/C, which is a supported catalyst composed of Pt nanoparticles dispersed on a carbon powder carrier. The use of Pt catalysts will be limited by resources and costs. How to reduce the platinum loading of catalysts or find low-cost catalysts with good performance is one of the current research hotspots.

Gas Diffusion Layer (GDL)

Two porous gas diffusion layers (GDL) sandwich the membrane-electrode assembly, and the main functions include supporting the catalytic layer, collecting current, conducting gas and discharging the reaction product water.

An ideal gas diffusion layer needs to have high electrical conductivity, porosity, proper hydrophilic/hydrophobic balance, high chemical stability, high thermal stability, and low cost.

The gas diffusion layer is composed of a support layer and a microporous layer. The materials of the support layer are mainly porous carbon fiber paper, carbon fiber woven cloth, carbon fiber non-woven fabric and carbon black paper. The microporous layer is usually composed of conductive carbon black and water repellent.

Preparation process of MEA

At present, the ultrasonic spraying method is widely used in the preparation of MEA. The catalyst is coated on both sides of the proton exchange membrane, and then the gas diffusion layer and the proton exchange membrane attached to the catalytic layer are combined by hot pressing.

The preparation process of ultrasonic spraying increases the contact area between the catalyst and the proton exchange membrane, reduces the impedance between the proton exchange membrane and the catalyst, and improves the performance of the membrane electrode.

Our company’s ultrasonic spraying equipment can be sprayed on a variety of different metal alloys, including the preparation of platinum, nickel, iridium and ruthenium-based fuel cell catalyst coatings, as well as PEMs, GDLs, DMFCs (direct methanol fuel cells) and SOFCs (solid Oxide fuel cell) manufacturing. The battery manufactured by this technology has the characteristics of high battery load and high battery efficiency.