Ultrathin membranes formation via the layer by layer self-assembly of carbon nanotubes-based inorganics as high temperature proton exchange membranes

Abstract

Layered membranes could be prepared with the layer by layer (LBL) self-assembly technique and they showed the wide application in the field of energy storage and transformation. The aim of this research is to develop high temperature proton exchange membranes (PEMs) through introducing carbon nanotube (CNT) and CNT-based inorganics into polymer systems of polyurethane (PU) and chitosan (CS). Successful formation of the ultrathin and conductive membranes through the alternate deposition of PU as polycations, CS and CNT-based inorganics as polyanions has been demonstrated by the identification of components and structural characterizations of fourier transform infrared spectra, scanning electron microscope, etc. Phosphoric acid (PA) molecules were combined with the formation of PA doped membranes while the prepared LBL membranes were immersed into PA solutions through the formed intermolecular hydrogen bonds. Besides PA conducting protons, the decreased proton conduction resistance owing to the multilayered structure could contribute to proton conductivity of PA doped membranes. Specifically, (PU/CNT-CdTe/PU/CS)150/60%PA membranes exhibited the maximum proton conductivity of 6.82 × 10−2 S/cm at 150 °C with an activation energy of 22.9 kJ/mol. The results revealed that CNT-based inorganics showed the potential to function as efficient proton carriers for the preparation of high temperature PEMs. Furthermore, the LBL self-assembly technique could provide a promising strategy to construct the ultrathin and layered membrane electrolytes.