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Osaka Gas’ residential polymer electrolyte fuel cell (PEFC) cogeneration system
About Osaka Gas’cell evaluation technology

Main factors of voltage drop

Degradation of the electrolyteSintering of the air electrode catalyst
Degradation of the CO tolerance of the fuel electrode catalyst
Decrease in the gas diffusivity in the air electrode

Degradation of the electrolyte

Hydrogen (H2) in the fuel electrode and oxygen (O2) in the air electrode pass through the electrolyte membrane, although in minute amounts. (Cross leakage) When the membrane thickness reduces as a result of the degradation of the electrolyte membrane, the amount of cross leakage increases, which is one cause of the reduction in voltage.

Degradation of the electrolyte

Degradation of the CO tolerance of the fuel electrode catalyst

The fuel electrode uses not only platinum (Pt) but also an alloy catalyst consisting of ruthenium and platinum that is resistant to CO poisoning. However, this ruthenium dissolves in the course of the operation of the fuel cell, with the CO tolerance consequently degraded. The catalyst with degraded CO tolerance allows more and more CO to be adsorbed, which inhibits the activity of the catalyst and results in the voltage drop.

Degradation of the CO tolerance of the fuel electrode catalyst
  • ※3 Poisoning: Weakening of the catalytic activity due to a substance called a catalyst poison that hinders the catalyst reaction.

Sintering of the air electrode catalyst ※1

Nano-sized (※2) platinum (Pt) particles used in the catalyst grow gradually, reducing the effective electrode area, which is one cause of the voltage drop.

Sintering of the air electrode catalyst
  • ※1 Sintering: growth of a particle into a larger one
  • ※2 Nano-size: A nanometer is a billionth of a meter (a millionth of a millimeter).

Decrease in the gas diffusivity in the air electrode

In this phenomenon, as carbon present in the catalyst layer corrodes, it becomes more and more hydrophile, with generated water being accumulated in the catalyst layer to lower the diffusivity of the air.
This is generally called “flooding.”

Decrease in the gas diffusivity in the air electrode

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