Nanoparticles of a Pt3Ni alloy on reduced graphene oxide (RGO) as an oxygen electrode catalyst in a rechargeable Li–O2 battery
Nanoparticles of a Pt3Ni alloy distributed on graphene sheets are studied as a catalyst for the oxygen reduction reaction in non-aqueous Li–O2 cells. The preparation involves simultaneous reduction of graphene oxide and Pt4+ and Ni2+ ions by hydrazine in an ethylene glycol medium. Pt nanoparticles are also prepared separately on reduced graphene oxide (RGO) sheets (Pt–RGO) in addition to Pt3Ni–RGO for studies of comparison. Samples are characterized with various physicochemical techniques. The oxygen reduction reaction (ORR) is studied in a non-aqueous electrolyte by using cyclic voltammetry and rotating disk electrode (RDE) techniques. Pt3Ni–RGO exhibits greater catalytic activity for the ORR when compared with Pt–RGO. O2 reduction follows a one e− pathway (O2 + e− = O2−) in a non-aqueous electrolyte. The catalytic performances of the samples are investigated in non-aqueous Li–O2 cells. The discharge plateau appears at 2.86 V with the Pt3Ni–RGO catalyst at 0.10 mA cm−2 current density, which is close to the theoretical value of 2.96 V. The overpotential of charging is lower with Pt3Ni–RGO, in comparison to that of Pt–RGO.