A review on sulfonated poly (ether ether ketone) based-membrane in direct borohydride fuel cell applications

Direct borohydride fuel cell (DBFC) is a liquid fuel cell technology that has a number of advantages, including lower operating temperature as well as great cell voltage when compared with hydrogen as well as alcohol fuel cell. The utilisation of reagent in liquids, under room pressures as well as temperatures, facilitated the internal processes of the fuel cell system and its application. Polymer electrolyte membranes or proton exchange membrane are an important component of fuel cells. Commercial perfluorosulphonic acid type membranes such as Nafion are often used in DBFC systems. However, Nafion has some disadvantages such as high cost, low stability at high temperatures, and low conductivity at low humidity or high temperatures that limit its use in DBFC systems. Thus, this review accounts the cheaper alternative membrane than Nafion that applied for DBFC which is sulfonated poly ether ether ketone (SPEEK) based membrane. The mixing of SPEEK with other filler such as graphitic carbon nitride (g-C3N4), clay, silica, metal oxide, heteropoly acids, and carbon nanotube is being discussed. The properties of SPEEK membranes performance such as degree of sulfonation, water intake, ionic conductivity, BH4 crossover as well as mechanical strength in DBFC were studied.