Six types of fuel cells have evolved in the past decades. They are called after their electrolyte, the substance that transports the ions. The electrolyte dictates the operating temperature of a fuel cell type. Depending on the operating temperature, a specific catalyst is chosen to oxidize the fuel. Fuel cell types therefore all have different catalysts. A brief summary of these six fuel cell types is given below.
| Fuel Cell Type | Common Electrolyte | Operating Temperature | System Output | Electrical Efficiency | Applications |
| Polymer Electrolyte Membrane (PEM) | Solid organic polymer poly-perfluorosulfonic acid | 50 – 100°C 122 – 212°F | <1kW – 250kW | 60% (direct) 25-40% (reformed) | Backup power Portable power Small distributed generation Transportation |
| Direct Methanol (DMFC) | Solid organic polymer poly-perfluorosulfonic acid | 50 – 100°C 122 – 212°F | Up to 1.5kW | 20 – 25% | Consumer goods Laptops Mobile phones |
| Alkaline (AFC) | Aqueous solution of potassium hydroxide soaked in a matrix | 90 – 100°C 194 – 212°F | 10kW – 100kW | 60% | Military Space |
| Phosphoric Acid (PAFC) | Liquid phosphoric acid soaked in a matrix | 150 – 200°C 302 – 392°F | 50kW – 1MW (250kW module typical) | 32-38% | Distributed generation |
| Molten Carbonate (MCFC) | Liquid solution of lithium, sodium, and/or potassium carbonates soaked in a matrix | 600 – 700°C 1112 – 1292°F | <1kW – 1MW (250kW module typical) | 45-47% | Electric utility Large distributed generation |
| Solid Oxide (SOFC) | Solid zirconium oxide to which a small amount of Yttria is added | 650 – 1000°C 1202 – 1832°F | 5kW – 3MW | 35-43% | Auxiliary power Electric utility Large distributed generation |
