Nano-tablets and rods-shaped Fe and Ni oxide/hydroxide encapsulated graphene for asymmetric supercapacitor and OER applications

Abstract

Ternary hybrid electrodes have been spotlighted in the energy storage and conversion domain due to their superior physicochemical and electrochemical attributes. Yet, elevating their electrochemical properties remains a challenge. Herein, gamma‑iron oxide nano-tablets and nickel hydroxide nano-rods encapsulated graphene sheets (γ-Fe2O3@Ni(OH)2@G/NF) nanocomposite (NC) electrodes are synthesized, using PVP as a surfactant by a simple, cost-effective and low-temperature synthesis procedure for supercapacitor (SC) and OER applications. These interconnected graphene sheets with γ-Fe2O3 and Ni(OH)2 are seen to enhance the electrical conductivity of NCs, leading to outstanding supercapacitive performances. The developed NC electrode displays the highest specific capacitance (Csp) of ∼937.5 F g−1 in the alkaline electrolyte. Moreover, Dunn's investigations, revealing the surface capacitive controlled contribution (77 %@10 mV s−1), predominates in the total capacitance, thus affirming the capacitor behavior of the electrodes. Using the NC electrode, an asymmetric supercapacitor (ASC) is constructed, and exhibits a maximum Csp of ∼120.3 F g−1 with an outstanding stability performance of 87.3 % capacitance retention. Moreover, the ASC displays an energy density of 22 Wh kg−1 under a power density of 1100 W kg−1. Overall, the results demonstrate that the developed ternary-hybrid composite shows promise as a worthy electrode for future energy demands.