Nanoparticles of a Pt3Ni alloy on reduced graphene oxide (RGO) as an oxygen electrode catalyst in a rechargeable Li–O2 battery

Abstract

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.