Proton-Conducting Channels in Polybenzimidazole Nanocomposites

Abstract

The interfacial interactions of hybrid organic-inorganic nanocomposite membranes, when tuned appropriately, can replicate to some extent the conduction mechanism of Nafion where hydrophilic and hydrophobic regions are dispersed randomly and the proton conduction takes place via the conducting channels. A wide variety of functionalizing molecules can be used for tuning the interface. The dynamic physical interactions between the particles and the polymer chains, and the hydrogen-bonding interactions among the functionalized silica nanoparticles in polybenzimidazole (PBI) matrix manifest as self-assembled inorganic networks or domains of different sizes depending on the filler content. These domains can trap phosphoric acid via strong hydrogen bonding and can act as reservoirs of phosphoric acid thus creating an acid gradient in the matrix. This gradient morphology gives rise to directed and faster proton conduction process in the PBI matrix. Thus, these inorganic-organic hybrid materials can be tuned for controlled conductivity as well as mechanical and thermal stability of proton exchange membrane for the fuel-cell applications.