In this study, Prussian blue analogue (PBA) with high content of lattice water is synthesized by a simple aqueous phase method and introduced into the sulfonated polysulfone (SPSf) polymer matrix, to prepare composite proton exchange membranes (PEMs) by solution casting method. The successful synthesis of PBA and the features of lattice water are comprehensively studied via X-ray diffraction (XRD), as well as several other characterization, reflecting considerable potential to promote Grotthuss type proton transport. In terms of membrane structure, XRD tests show that the PBA could be well dispersed in the SPSf matrix with the filler loading of 0-1.5 wt%. Mechanical strength, swelling ratio and water uptake were reduced in SPSf/PBA composite membranes with increased filler loading, within the appropriate range for PEM usage. The proton conductivity of SPSf/PBA composite membranes show evident improvements over pristine SPSf membrane, especially when relative humidity (RH) decreases. This result shows that the SPSf/PBA composite membranes are promising for use at low RH conditions, owing to the PBA filler containing abundant lattice water which helps facilitate Grotthuss type proton transport.
Keywords Proton exchange membrane fuel cell, composite membrane, prussian blue analogue, low relative humidity, enhanced proton conductivity