Antioxidant Sulfide‐Linked Polymer Membrane with Inherent Microporosity Enables Fuel Cells to Achieve Outstanding Power Density and Durability Over a Wide Temperature Range

Abstract Conventional phosphoric acid (PA) doped polybenzimidazole are regarded as the most promising materials for high‐temperature proton exchange membrane fuel cells (HT‐PEMFCs). Yet, their practical application has been hindered by their high production cost, poor oxidation stability, and loss of PA at low temperatures. Here, a polymer of intrinsic microporosity containing “sulfide‐linkage” radical‐sacrificial‐agent is designed with good solubility and high PA retention, which enables it to operate for long periods at 80–180 °C. Specifically, the “sulfide‐linkage” radical‐sacrificial‐agent enabled PSBI‐IM to be durable for 100 h with mass retention still higher than 90%, and the capillary effect of the micropores enabled PSBI‐IM/PA to retain more than 60% of PA under high humidity. After rational optimization, the cell assembled with PSBI‐IM/PA achieved a power density of 1.62 W cm −2 with a specific power of 2.7 W mg −1 and an operating time of more than 500 h (0.2/0.4 A cm −2 @160 °C). In addition, the voltage drop is only 5% even after 40 h of accelerated stress testing at 0.4 A cm −2 @ 80 °C. Therefore, the PSBI‐IM/PA can be stabilized over a wide temperature range from 80 to 160 °C, providing a new material for the HT‐PEMFCs with flexible operational temperature.