Thursday, 23 June 2016
Riverside Center (Hyatt Regency)
Li-air batteries are appealing as they offer much higher energy density than the current Li-ion batteries. However, the non–aqueous Li-air batteries suffer from poor cycle life due to electrolyte decomposition and clogging of the air electrode by insoluble discharge products. Efficient bifunctional catalysts could lower the overpotential and improve the stability of Li-air batteries, thus prolonging its cycle life. This study focuses on Iron phthalocyanines (FePc) supported on carbon materials as a solid electrocatalyst for lithium air batteries. Metal phthalocyanines were utilized mainly because of their structural analogy which could be fine- tuned by the metal being used, accessibility, and low cost. The carbon supports such as reduced graphene oxide (rGO) and carbon nanotubes (CNT) were utilized which rendered desirable surface properties like high surface area and high electronic conductivity. FePc/carbons delivered superior electrocatalytic performance for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) comparable and better than that of commercial Pt/C. The bifunctional catalysts were then applied as electrocatalysts in non-aqueous lithium air batteries. The air cells delivered better electrochemical performance mainly by reducing the large overpotential associated with ORR and OER. The cells exhibited better reversibility and cyclability as well. The improved electrocatalytic activity was mainly because of the π–π interaction between carbons and iron phthalocyanines. In addition, the effects of ball milling by ball milling the FePc, and the effects of nitrogen (N2) doping by doping the carbon supports with N2 were investigated. Ball milling has significantly improved the electrocatalytic properties of FePc and N2 doping further enhanced the overall performance.