Mechanism and Improvement Scheme of Fuel Cell Attenuation
Mechanism and Improvement Scheme of Fuel Cell Attenuation – Cheersonic
With the continuous development of the fuel cell industry, the market has higher and higher requirements for the durability of fuel cell products. The current market demand for the durability of passenger vehicles is generally 120,000 kilometers in 8 years and 200,000 kilometers in 5 years for commercial vehicles. The competition of fuel cell products has expanded from performance to durability, and durability has a huge impact on the life cycle cost and product brand of the product.
Factors Affecting Fuel Cell Durability
The main influencing factors include material factors, design factors, control factors, process factors, road conditions and environmental factors. To improve the durability of products, it is necessary to deeply study the attenuation mechanism behind various influencing factors. These attenuation mechanisms are subdivided into dry and wet cycles, potential cycles, high potential, hydrogen-air interface, operating temperature, low temperature operation, vibration, gas impurities and undergassing, etc.
For different fuel cell products, the degree of influence of various attenuation factors on the product and the underlying attenuation mechanism are not the same. In product development, it is necessary to be able to accurately locate the main attenuation factors of the product and complete the quantification of the degree of attenuation, so that the durability solution can be proposed based on the attenuation mechanism. Completed durability development.
Common Attenuation Mechanisms in Fuel Cell Product Development
The decay mechanism of the hydrogen-air interface is easy to generate a hydrogen-air interface in the case of fuel cell power on and off, poor internal water management, uneven gas distribution, and system failure. membranes are severely affected.
Another decay mechanism that often occurs is the decay caused by potential alternation. The decay mechanism is different at different potentials. The following potential division is convenient for engineering understanding, not an absolute value. The decay mechanism is more likely to occur in the corresponding potential interval.
1. Ostwald ripening effect leads to the growth of Pt particles ( 0.6-1.1V )
Frequent acceleration and deceleration potential cycles will increase the surface free energy, resulting in the continuous growth of the catalyst. Small grains migrate to the large grains in the form of atoms/molecules and re-deposit, resulting in the growth of the particles and the reduction of the electrochemically active area.
2. Redeposit on the polymer phase after dissolution of Pt crystals (0.6-1.1V)
Water weakens the metal-carbon bond bond, which is conducive to grain migration. At low potential, the dissolution rate of Pt is accelerated, and the electrochemical reaction rate is fast.
3. Crystal migration and sintering lead to the growth of Pt particles (<0.6 V) 4. Corrosion of carbon support leads to detachment and aggregation of Pt nanoparticles (>1.2V)
5. Polymer phase decay leads to reduced ECA (low potential high current)
Fuel Cell Durability Improvement Scheme
Improving the durability of fuel cell products is a systematic and long-term work, and many institutions, scientific research institutions and companies have done a lot of work. This paper mainly proposes durability solutions from two aspects: material and system.
In terms of materials, in order to improve durability, catalyst platinum loading can be increased, catalyst structure, carrier structure, etc., although some solutions increase the cost, but also bring about the improvement of durability and power density, which is also an effective means of engineering improvement.
At the system level, such as the fake battery scheme that has been used, the voltage inspection that has been applied by most manufacturers, the strategy of avoiding high potential, and so on. Many solutions are currently being adopted by some manufacturers, and they have achieved good results in practical applications, and some solutions are still being verified. Engineering design is a series of trade-offs and trade-offs, and it is based on these trade-offs that the product characteristics of each fuel cell manufacturer come about.
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