09/07/2022

Polymer Exchange Membrane ( PEM ) Fuel Cells

 

Polymer electrolyte membrane ( PEM ) fuel cells

  • It is also called as proton exchange membrane fuel cells. 
  • It uses solid polymer as electrolyte and porous carbon electrodes containing platinum or platinum alloy catalyst. 
  • The hydrogen supplied through hydrogen storage tank at the anode where electrons are separated from protons and it flows through external circuit towards cathode. 
  • The protons move towards cathode through electrolyte. 
  • At the cathode, protons and electrons combines with oxygen to produce pure water as by product. 
  • Oxygen can be supplied at the cathode side in its purified for. 
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  • The platinum catalyst produces carbon monoxide therefore additional reactor required to reduce carbon monoxide in the fuel gas. 
  • This reactor adds additional cost. 
  • It delivers high power density and offers low weight and volume as compared to other fuel cells. 
  • This type of fuel cell requires only hydrogen, oxygen from air and water to operate. 
  • It operates at low temperature at 80 degree C , low pressure operation allows them to quick warm up time. It will result in better durability and less wear on the system.

Chemical reaction

Anode : H2 → 2H+ + 2e-

Cathode : O2 + 4H+ + 2e- → 2H2O

Overall reaction : 2H2 + O2 → 2H2O

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Advantages

  • Low weight and volume
  • High power density
  • Low temperature operation
  • Solid electrolyte reduces corrosion and electrolyte management systems
  • Quick start up and load following
  • Low / zero emission when operating on hydrogen

Disadvantages

  • Expensive catalysts
  • Sensitive to fuel impurities
  • Addition cost required for reactor to reduce carbon monoxide

Applications

  • Portable power
  • Back up power
  • Primarily used for transportation applications
  • Some stationary applications
  • Vehicles like cars, buses, and heavy-duty trucks

Stack size

< 1 to 100 kW

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