Ir nanoparticles-anchored reduced graphene oxide as a catalyst for oxygen electrode in Li–O2 cells

Abstract

Iridium nanoparticles-anchored reduced graphene oxide (Ir-RGO) was prepared by simultaneous reduction of graphene oxide and Ir³⁺ ions and its catalytic activity for oxygen electrode in Li–O₂ cells was demonstrated. Ir particles with an average size of 3.9 nm were uniformly distributed on RGO sheets. The oxygen reduction reaction (ORR) was studied on an Ir-RGO catalyst in non-aqueous electrolytes using cyclic voltammetry and rotating disk electrode techniques. Li–O₂ cells with Ir-RGO as a bifunctional oxygen electrode catalyst were subjected to charge–discharge cycling at several current densities. A discharge capacity of 9529 mA h g⁻¹ (11.36 mA h cm⁻²) was obtained initially at a current density of 0.5 mA cm⁻² (393 mA g⁻¹). A decrease in capacity was observed on increasing the current density. Although there was a decrease in capacity on repeated discharge–charge cycling initially, a stable capacity was observed for about 30 cycles. The results suggest that Ir-RGO is a useful catalyst for rechargeable Li–O₂ cells.