Intercalation pseudocapacitance in chemically stable Au-α-Fe2O3-Mn3O4 composite nanorod: Towards highly efficient solid-state symmetric supercapacitor device

Abstract

Pseudocapacitance generally appears due to the surface or near-surface reversible Faradaic reactions. In this regard, 2D layered materials have gained substantial attention as a potential source for driving a myriad of energy storage applications owing to their unique surface-structure relationship. Here, we have demonstrated that a pseudocapacitive mechanism becomes increasingly operative when H+ ions are intercalated easily into the enhanced van der Waals gap of layered material α-Fe2O3 in Au-α-Fe2O3-Mn3O4 nanocomposite. Theoretical studies have shown an enhancement of van der Waals gap which is attributed to the intercalation of Au into the layers of α-Fe2O3. Structural and compositional characterizations have been carried out in detailed by different physical methods and are supported by theoretical studies. Electrochemical measurements show excellent specific capacitance of 580 F g−1 at 1 A g−1 along with improved capacity retention compared to the mother component α-Fe2O3 (205 F g−1 at 1 A g−1) in 0.5 M H2SO4 electrolyte in a potential window of 1.2 V. Further, electrokinetic measurements revealed that total charge stored in the nanocomposite is based on a dominant capacitive mechanism (70% of the total capacitance) along with diffusive mechanism (30% of the total capacitance) at scan rate 5 mV s−1 whereas, α-Fe2O3 exhibits 34% capacitive and 66% diffusive at same scan rate. The synthesized composite nanorod as an efficient electrode material in a solid-state symmetric supercapacitor device exhibits excellent energy density of 36.12 Wh kg−1 and power density of 1994 W kg−1 at 1 A g−1 and 10 A g−1, respectively with outstanding stability (89%) up to 2000 successive charge-discharge cycles at 10 A g−1. This work may offer a new scope for further development of intercalation pseudocapacitive nanomaterials towards achieving high energy storage supercapacitors. © 2019 Elsevier Ltd