The electrolyte used in this fuel cell is 100% phosphoric acid, which is fixed in a matrix, such as asbestos, polybenzylimidazole. The operating temperature of these cells is 150–220 °C, and temperatures above 180°C have the advantage of shifting the equilibrium constant in favour of carbon dioxide, eliminating the problem of carbon monoxide poisoning. In this case, we can use gas directly from steam reforming.

Again, platinum is used as a catalyst, and hydrogen, which is generated from fossil fuels through steam reforming, is used as fuel. Air is used as an oxidizer. These fuel cells have found use in cogeneration units.