Fuel cells are attractive devices that convert chemical energy into electricity through the direct electrochemical reaction of hydrogen and oxygen. Intermediate temperature fuel cells operated at 200–300 °C can simplify water and thermal managements, enable the use of non-precious or low-loading precious metal catalysts and provide insensitivity toward fuel and air impurities such as carbon monoxide. However, the performance of current intermediate temperature fuel cells is poor due to a lack of highly-conductive membrane electrolytes and optimal electrodes designed for these fuel cells. Here, we demonstrate high-performing intermediate temperature fuel cells that use SnP2O7–polymer composite membranes and a quaternary ammonium-biphosphate ion-pair coordinated polymer electrolyte in the electrodes. The peak power density of the fuel cell under H2 and O2 reached 870 mW cm−2 at 240 °C with minimal performance loss under exposure to 25% carbon monoxide.
