Application of organic/inorganic composite material for intermediate temperature anhydrous PEFC

Heteropolyacid, such as 12-tungstophosphoric acid (H₃PW ₁₂O₄₀; PWA), has been known to show the high proton conductivity under high-humidified condition. However, under the high temperature (>100°C) and anhydrous (water-free) conditions, heteropolyacid loses the hydration water and the proton conductivity abruptly decreases. Therefore, if the high proton conduction of heteropolyacid uses under anhydrous condition, this material will pave the way for new electrochemical devices including the electrolyte of fuel cell, electrochromic displays, chemical sensors, and others. In this report, we propose the new fast proton conducting structure and mechanism under high temperature and anhydrous conditions. The composite material of PWA and polystyrene sulfonic acid (PSS) construct the PWA-encapsulated material by the self-assembly of -SO₃H onto the PWA surface. As a result, the fast proton transfer occurred at the interface between the PWA and -SO₃H and this encapsulated-material indicated the high anhydrous proton conductivity of 1 × 10^-2 S cm^-1 at 180°C.