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.
- 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.
PEM Fuel Cell: Chemical reaction
Anode : H2 → 2H+ + 2e-
Cathode : O2 + 4H+ + 2e-
→ 2H2O
Overall reaction : 2H2 + O2
→ 2H2O
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PEM Fuel Cell: 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
PEM Fuel Cell: Disadvantages
- Expensive catalysts
- Sensitive to fuel impurities
- Addition cost required for reactor to reduce carbon monoxide
PEM Fuel Cell: Applications
- Portable power
- Back up power
- Primarily used for transportation applications
- Some stationary applications
- Vehicles like cars, buses, and heavy-duty trucks
PEM Fuel Cell: Stack size
- Less than 1 to 100 kW
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