Bio-Inspired Membranes for Advanced Polymer Electrolyte Fuel Cells. Anhydrous Proton-Conducting Membrane via Molecular Self-Assembly

Bio-inspired materials or natural biopolymers have attracted much attention for industrial applications as biocompatible materials. Although these materials have been discarded as industrial waste around the world, there is an increasing interest in environmental, engineering, and electrical applications of the biomaterials because of their well-controlled structures and superior conducting properties. The controlled structures of the hydrogen-bonding network in biomolecules, such as bioenergetic proteins, are essential for efficient energy transduction in living systems and application of a biomolecular mechanism could make it possible to prepare efficient electrolytes with superior conducting properties. We report here a recent investigation on the new class and new concept of electrolyte materials with bio-inspired molecular architectures of acid–base pairs for anhydrous proton conduction and its application in intermediate temperature (100–200 °C) polymer electrolyte fuel cells (PEFC). Although some membranes were composed from entirely biomolecular materials, they showed large anhydrous proton conductivities from room temperature to 160 °C, and fuel cells employing biomembranes as a polymer electrolyte produced electrical power under non-humidified H2/O2 condition at 160 °C. These bio-inspired materials may have many potential applications not only because of its superior ion conducting properties, in particular, under anhydrous (water-free) or extremely low-humidity conditions, but also because of its biocompatibility.