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

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 alpha-Fe2O3 in Au-alpha-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 alpha-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 alpha-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, alpha-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 10A g(-1). This work may offer a new scope for further development of intercalation pseudocapacitive nanomaterials towards achieving high energy storage supercapacitors. (C) 2019 Elsevier Ltd. All rights reserved.