Direct electro-synthesis of MnO2 nanoparticles over nickel foam from spent alkaline battery cathode and its supercapacitor performance

Abstract

Abstract This work reports the recovery of manganese ions from spent primary alkaline battery (PAB) cathode, subsequent anodic electro-synthesis of MnO2 nanoparticles on Ni foam (MnO2 NPs/Ni foam) for supercapacitors. The as-fabricated MnO2 NPs/Ni foam is characterized by common optical and surface analytical techniques. The X-ray diffraction (XRD) of MnO2 NPs/Ni foam matches well with γ-MnO2 NPs pattern and hence the synthesized MnO2 NPs mainly exist in γ-phase. The synthesized MnO2 NPs are mostly in spherical cluster shape with an average size of 15 nm, inferred from the scanning electron microscopic (SEM) images. The X-ray photoelectron spectroscopy (XPS) result reveals that, synthesized MnO2 NPs embraces with two different oxidation states such as 4+ (MnO2) and 3+ (MnOOH). The MnO2 NPs/Ni foam delivers a maximum specific capacity of 549 F/g at the scan rate of 5 mV/s in three electrodes aqueous K2SO4 system. Further, the two electrode asymmetric supercapacitor device is constructed with MnO2 NPs/Ni foam as a positive and commercial graphene nanoplatelets coated Ni foam (GNP/Ni foam) as a negative electrode. The assembled supercapacitor device yields a maximum specific capacitance of 105 F/g at 5 mV/s, which achieves a maximum energy density of 14.7 Wh/kg at the power density of 748.9 W/kg between 0 and 1.5 V of working potential. This effort may pave the way for recovery and utilization of spent PAB cathode materials for energy storage devices.