Phosphoric acid fuel cell

[1] Electrolyte is highly concentrated or pure liquid phosphoric acid (H3PO4) saturated in a silicon carbide (SiC) matrix.

The electrodes are made of carbon paper coated with a finely dispersed platinum catalyst.

[3] At lower temperatures phosphoric acid is a poor ionic conductor, and CO poisoning of the platinum electro-catalyst in the anode becomes severe.

Disadvantages include rather low power density and chemically aggressive electrolyte.

India's DRDO has developed PAFC based air-independent propulsion for integration into their Kalvari-class submarines.