Phosphoric acid fuel cells (PAFCs) consist of an anode and a cathode made of a finely dispersed platinum catalyst on carbon and a silicon carbide structure that holds the phosphoric acid electrolyte. They are quite resistant to poisoning by carbon monoxide but tend to have lower efficiency than other fuel cell types in producing electricity. However, these cells operate at moderately high temperatures of around 180ºC and overall efficiency can be over 80% if this process heat is harnessed for cogeneration.
This type of fuel cell is used in stationary power generators with output in the 100 kW to 400 kW range to power many commercial premises around the world, and they are also finding application in large vehicles such as buses. Most fuel cell units sold before 2001 used PAFC technology.