Bimetallic MPt (M: Co, Cu, Ni) alloy nanoparticles assembled on reduced graphene oxide as high performance cathode catalysts for rechargable lithium-oxygen batteries

In this work, the performance of bimetallic MPt (M: Co, Cu, Ni) alloy nanoparticles (NPs) assembled on reduced graphene oxide (rGO) as cathode catalysts for rechargable nonaqueous lithium-oxygen (Li-O2) batteries was investigated. Monodisperse MPt alloy NPs were prepared by using one-pot protocol comprising the thermal decomposition of metal acetylacetonates in the presence of oleylamine (OAm) serving as surfactant, reducing agent and solvent. As-synthesized MPt alloy NPs were then assembled on reduced graphene oxide (rGO) via liquid self-assembly method. Both colloidal MPt alloy NPs and rGO assembled ones were characterized by TEM, XRD and ICP-MS. Next, the cathode performance of rGO-MPt catalysts were evaluated by studying the galvanostatic discharge-charge profiles that were carried out in a Li-O2 cells using a solution of 0.5 M LiTFSI in DMSO as an electrolyte at an applied current density of 0.05 mA cm-2. The Li-O2 cells with rGO-MPt cathode catalysts provide the discharge capacities reaching up to about 9.0 mAh cm-2. Among three rGO-MPt catalysts tested for the Li-O2 battery, rGO-Co48Pt52 provided the highest discharge capacity of 9898 mAh g-1 and 80 cycles at the curtailed capacity of 0.75 mAh cm-2 whereas the rGO-Ni47Pt53 catalyst showed the most stable cycle-life.