Inorganic Acid‐Impregnated Covalent Organic Gels as High‐Performance Proton‐Conductive Materials at Subzero Temperatures

Proton exchange membrane fuel cells usually suffer from severe power loss and even damage under subzero‐temperature working surroundings, which restricts their practical use in cold climates and in high‐altitude drones. One of the effective solutions to these issues is to develop new types of proton‐conductive materials at subzero temperature. This study presents a series of acylhydrazone‐based covalent organic gels (COGs). The COGs are stable in acidic media and show high proton conductivity over the temperature range of −40 to 60 °C under anhydrous conditions. Compared with other reported organic conductive materials, both a state‐of‐the‐art conductivity of 3.8 × 10 −4 S cm −1 at −40 °C and superior long‐term stability are demonstrated. Moreover, the COGs possess remarkable self‐sustainability, good processability, and superior mechanical properties, and may be processed and molded into any desirable shapes for practical applications. These advantages make COGs hold great promises as solid‐state electrolytes under subzero‐temperature operating conditions.