Proton exchange membranes (PEMs) play a central role in determining the efficiency

durability

and operational flexibility of PEM fuel cells (PEMFCs). However

conventional PEMs exhibit strong temperature-dependent proton-transport behavior

which limits their ability to support both rapid start-up at low temperatures and stable operation at elevated temperatures. Water-mediated PEMs show excellent conductivity under low-temperature and high-humidity conditions but suffer from dehydration and structural instability in the high-temperature regime. In contrast

water-independent PEMs

particularly phosphoric-acid-doped systems

conduct protons efficiently under anhydrous high-temperature conditions yet experience acid leaching that hampers room-temperature start-up and long-term durability. This review summarizes the fundamental proton-transport mechanisms that govern temperature-dependent performance and discusses recent advances in materials design aimed at enabling wide-temperature-range PEM operation. For water-mediated membranes

strategies such as incorporating hydrophilic fillers

constructing confined hydrophilic domains

and introducing additional protontransfer sites have been developed to mitigate water loss and stabilize proton conduction.For water-independent membranes

approaches including strengthening polymer–acid interactions

engineering nanoscale confinement

designing multilayer architectures

and constructing multi–proton-carrier networks effectively improve acid retention and broaden operational temperature windows. Emerging fixedcarrier systems based on phosphonic-acid-grafted polymers

metal–organic frameworks

and covalent organic frameworks offer new pathways for stable anhydrous proton conduction across a wide temperature range.We conclude by outlining key challenges and future research opportunities

including reducing the dependence on volatile or leachable proton carriers

developing adaptive nanochannel architectures

improving anhydrous high-temperature conduction

and establishing scalable membrane fabrication methods. Continued innovation in these directions is expected to enable next-generation wide-temperature-range PEMs capable of flexible

high-efficiency operation from sub-zero to high-temperature conditions.