Proton conduction in materials is an essential phenomenon in various systems, such as polymer electrolyte fuel cells (PEFCs), where the proton conductivity of the electrolyte plays a major role in determining the overall performance of the PEFC system. PEFC is an efficient electricity generator without CO2 emission in operation, mainly applied for the energy source of fuel cell vehicles (FCVs). Looking at the broad commercialization and cost reduction of FCVs, the operation under high temperature is essential for catalyst materials to enhance activity and eliminate poisoning by impurities in the fuel and for radiators and water management systems to be simplified. However, the proton conductivities severely diminish at low relative humidity (RH) conditions. At high temperatures, fast drying of the electrolyte results in decreased conductivity and a huge ohmic loss.