Spinel LiMn2O4 nanoparticles dispersed on nitrogen-doped reduced graphene oxide nanosheets as an efficient electrocatalyst for aluminium-air battery

Nitrogen-doped reduced graphene oxide nanosheets modified with LiMn2O4 (LMO) nanoparticles as low cost, nontoxic and efficient catalyst for oxygen reduction reaction (ORR) were synthesized by a simple two step hydrothermal method. The physical properties and the activity of the composites toward ORR were investigated using X-ray diffraction (XRD) spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray (EDX) spectra, and electrochemical measurements, including cyclic voltammograms (CV), steady state polarization curves and electrochemical impedance spectroscopy (EIS) in O2-saturated 0.1 M KOH electrolyte. The LiMn2O4 supported on nitrogen-doped reduced graphene oxide (LMO/N-rGO) showed more positive onset potential, half wave potential, faster charge transfer, and a higher cathodic peak current in alkaline media than that of LiMn2O4/rGO and N-rGO. Furthermore, air electrodes with hybrid catalysts were fabricated to test the discharged performance in Al-air batteries under ambient air condition. The batteries with LMO/N-rGO cathode displayed the higher energy density of 585 mAh g−1 and sluggish potential drop. The improved catalytic activity and battery performance of LMO/N-rGO can be attributed to the effect of active sites induced by nitrogen, and synergic covalent coupling between the nitrogen-doped graphene sheets and spinel lithium manganese oxide. These results confirm that LMO/N-rGO is a promising material for air cathodes with good activity and stability in aluminium-air battery.