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 degrees C under anhydrous conditions. Compared with other reported organic conductive materials, both a state-of-the-art conductivity of 3.8 x 10(-4) S cm(-1) at -40 degrees 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.