QDSJ012_车用燃料电池PEMFC_20页_1mb

PEMFC Summary

Definition and Characteristics

Proton Exchange Membrane Fuel Cells (PEMFCs) are a type of fuel cell that directly converts chemical energy from hydrogen fuel into electricity with high efficiency and low emissions. Unlike internal combustion engines, PEMFCs are not subject to the Carnot cycle efficiency limit. Key characteristics include fast start-up time, no electrolyte loss, high power and energy density, and long operational life.

Working Principle

PEMFCs consist of an anode, cathode, and a proton-exchange membrane. Hydrogen fuel is oxidized at the anode, releasing electrons that generate current through an external circuit. Protons migrate through the membrane to the cathode, where they combine with oxygen and electrons to form water. The membrane is typically made of perfluorosulfonic acid and uses platinum-carbon catalysts for efficient reactions.

History and Development

PEMFC technology originated in the 1960s with early applications in space flights, but issues like membrane degradation delayed its adoption. A breakthrough in the 1990s, driven by Canadian and US research, led to improvements in membrane conductivity, catalyst efficiency, and electrode design, resulting in higher performance and longer lifespans.

Characteristics and Applications

PEMFCs offer advantages such as room-temperature operation, quick response, and minimal environmental impact. They are used in various applications, including distributed power generation for homes and businesses, electric vehicles, mobile communication devices, and submarines, providing clean and reliable energy.

Main Components

• Electrodes: Gas diffusion layers and catalyst layers facilitate gas diffusion and electron transfer. Carbon-based materials are commonly used.
• Catalysts: Platinum-carbon is standard, but other catalysts like platinum-ruthenium are explored for cost-efficiency.
• Membrane: A perfluorosulfonic acid membrane allows proton conduction and must be properly hydrated for optimal performance.
• Bipolar Plates: Conduct electricity, distribute gases, and manage heat; typically graphite or metal-based.
• Flow Fields: Designated patterns (e.g., parallel grooves or serpentine) ensure uniform gas flow and water removal.

Design Considerations

PEMFC stack design involves optimizing cell voltage (typically 0.6–0.7 V per cell) for efficiency and power density. Water management is crucial to maintain membrane hydration, while thermal management uses cooling fluids like deionized water or ethylene glycol to dissipate heat. Failure modes include reversed polarity due to gas supply issues and membrane degradation from water fluctuations or mechanical stress, which can be mitigated through proper monitoring and control.

Failure Modes

Common failure causes include:

• Reversed polarity: Occurs when gas supply is uneven, leading to potential explosions.
• Membrane degradation: Due to temperature changes, mechanical damage, or rapid water loss, reducing cell performance. Proper humidification and operational protocols help prevent these issues.