Nitrogen-doped Graphene Interpenetrated 3-D Ni- Nanocage: Efficient and Stable Water-to- Dioxygen Electrocatalyst

Herein, we report synthesis of nitrogen-doped graphene (NGr) interpenetrated 3-D Ninanocage (Ni-NGr) electrocatalyst by simple water-in-oil (w/o) emulsion technique for oxidation of water-to-dioxygen. Correlation of adsorption of NGr and subsequent interpenetration through the specific surface plane of nickel particles as well as concomitant interaction of N, C, with Ni at a nano-regime have been investigated. Apart from the benefits of the synergistic interactions between Ni, N, and C, the overall integrity of the structure and its intra-molecular connectivity within the framework help to achieve better oxygen evolution characteristics at a significantly reduced overpotential. The engineered Ni-NGr nanocage displays a substantially low overpotential of ~290 mV at practical current density of 20 mA/cm in 0.1 M KOH. In comparison, NGr and Ni-particle as separate entities give overpotentials of ~570 and ~ 370 mV under similar conditions. Moreover, the long term stability of Ni-NGr has been investigated by anodic potential cycling for 500 cycles and observed an 8.5 % increment in the overpotential at 20 mA/cm . Additionally, chronoamperometric test has been performed for 15 h at 20 mA/cm , which highlight the better sustainability of Ni-NGr in the actual operating condition. Finally, the quantitative estimation of evolved oxygen has been monitored by gas chromatography and is found to be 70 mmol/h/g of oxygen, which is constant in second cycle as well.