Nanomaterial-incorporated sulfonated poly(ether ether ketone) (SPEEK) based proton-conducting membranes: properties and applications

Sulfonated poly(ether ether ketone) (SPEEK) based proton-conducting membranes are a promising alternative to Nafion and have been studied extensively in the last few decades for different fuel cells. It was observed that the pure SPEEK membrane suffers from excessive swelling, loss of water, and even degradation of functional groups during high-temperature operation. To improve the overall membrane performance, SPEEK has been blended with different polymers and also with micro- and nanostructured inorganic fillers. In recent years, nanofiller-incorporated SPEEK nanocomposite membranes have received much attention due to their improved properties and performances. These nanocomposite membranes showed improved water uptake and water retention, reduced fuel crossover, good mechanical properties, and higher proton conductivity. It was observed that nanomaterial size, shape, and functionality can affect the membrane properties. Normally nanomaterials have larger specific surface area and superior mechanical properties. When incorporated in SPEEK they influence its microstructure and improve the mechanical and thermal stability as well as water management and ion-exchange properties. Herein, we will highlight the important findings on SPEEK-based nanocomposite membranes and the influence of the nanofillers on the membrane properties.