Proton exchange membrane based on chitosan and solvent-free carbon nanotube fluids for fuel cells applications

Abstract

Poor dispersion and inert ionic conduction are two major obstacles towards using carbon nanotubes (CNTs) to modify polymer electrolyte membranes (PEMs) in energy conversion devices. In this work, solvent-free carbon nanotube fluids (CNT fluids) with liquid-like behavior are prepared through an ion exchange method and incorporated into a chitosan (CS) matrix to fabricate composite membranes. The electrostatic interactions between SO₃^- groups in the CNT fluids and NH₂ groups in the CS matrix, in addition to the unique flow properties of the CNT fluids, promote the uniform dispersion of CNT fluids in the CS matrix. Markedly, the CS/CNT fluid-3 composite membrane is simultaneously reinforced and toughened by 180% and 300% compared to pure CS membrane, respectively. Moreover, the SO₃^- groups in the CNT fluids facilitate the proton transfer such that the proton conductivity of CS/CNT fluid-3 composite membrane reaches a maximum value of 0.044 S cm^-1 at 80 °C.

Keywords: Chitosan; Fuel cells; Proton exchange membrane; Reinforcement and toughening; Solvent-free carbon nanotube fluids.