Proton Conducting Membranes with Molecular Self Assemblies and Ionic Channels for Efficient Proton Conduction

Abstract

Supramolecular assemblies are vital for biological systems. This phenomenon in artificial materials is directly related to their numerous properties and their performance. Here, a simple approach to supramolecular assemblies is employed to fabricate highly efficient proton conducting molecular wires for fuel cell applications. Small molecule-based molecular assembly leading to a discotic columnar architecture is achieved, simultaneously with proton conduction that can take place efficiently in the absence of water, which otherwise is very difficult to obtain in interconnected ionic channels. High boiling point proton facilitators are incorporated into these columns possessing central ionic channels, thereby increasing the conduction multifold. Larger and asymmetrical proton facilitators disintegrated the self-assembly, resulting in low proton conduction efficiency. The highest conductivity was found to be approaching 10−2 S/cm for the molecular wires in an anhydrous state, which is ascribed to the continuous network of hydrogen bonds in which protons can hop between with a lower energy barrier. The molecular wires with ionic channels presented here have potential as an alternative to proton conductors operating under anhydrous conditions at both low and high temperatures.

Keywords

• supramolecular assemblies
• molecular columns
• molecular wires
• ionic channels
• proton conductors
• fuel cells