Hydrophilic TiO2 decorated carbon nanotubes/sulfonated poly(ether ether ketone) composite proton exchange membranes for fuel cells

Abstract

AbstractSulfonated poly(ether ether ketone) (SPEEK) is currently considered to be one of the most potential candidates of commercial perfluorinated sulfonic acid proton exchange membranes. To balance the proton conductivity and mechanical properties of SPEEK, nano TiO2 coated carbon nanotubes (TiO2@CNTs) were prepared using a benzyl alcohol‐assisted sol‐gel method and then used as a new nanofiller to modify SPEEK to prepare SPEEK/TiO2@CNTs composite membranes. The thick insulated TiO2 coating layer can effectively avoid the risk of electronic short‐circuiting formed by CNTs, while the hydrophilicity of TiO2 can also reduce the polar difference between CNTs and SPEEK matrix, thus promoting the homogeneous dispersion of CNTs in the composites. As a result, the composite membranes demonstrated simultaneously improved strength and proton conductivity. Incorporating 5 wt% of TiO2@CNTs exhibited 31% growth in mechanical strength when compared with pure SPEEK. Moreover, the maximum conductivity was 0.104 S cm−1 (80°C) for the composite membrane with 5 wt% of TiO2@CNTs, which was nearly twice as high as that of SPEEK membrane (0.052 S cm−1).