PHYSICAL REVIEW APPLIED 14, 024067 (2020) Experimental and Theoretical Investigation of the Energy-Storage Behavior of a Polyaniline-Linked Reduced-Graphene-Oxide–SnO 2 Ternary Nanohybrid Electrode Manikandan Kandasamy, 1 Amreetha Seetharaman, 1 Brahmananda Chakraborty, 2,3, * Inbamani Manohara Babu, 4 J. Johnson William, 4 Gopalan Muralidharan, 4 Kandasamy Jothivenkatachalam, 5 and Dhanuskodi Sivasubramanian 1, † 1 Nonlinear Optical Materials Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli, Tamil Nadu 620024, India 2 High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India 3 Homi Bhabha National Institute, Mumbai 400094, India 4 Department of Physics, Gandhigram Rural Institute-Deemed University Gandhigram, Dindigul, Tamil Nadu 624302, India 5 Department of Chemistry, Anna University, BIT Campus, Tiruchirappalli, Tamil Nadu 620024, India (Received 30 March 2020; revised 20 June 2020; accepted 7 July 2020; published 24 August 2020) Hybrid capacitors are one type of emerging devices in the realm of energy storage. Here, we report the interactions of reduced graphene oxide (RGO) on SnO 2 and polyaniline (PANI) on RGO/SnO 2 , leading to improved electronic and structural properties and enhanced charge-storage performance for the ternary hybrid RGO/SnO 2 /polyaniline (GSP). The synthesized ternary hybrid exhibits an excellent specific capacitance of 340 F/g at 2 A/g (current density) with 98% capacitance retention for 1000 charge- discharge cycles. The constructed asymmetric GSP||RGO hybrid exhibits an energy density of 12 Wh/kg at a power density of 1.07 kW/kg. We present an insight into the physics behind the enhanced charge- storage performance using density functional theory simulations, along with an analysis of the structural and electronic properties of the hybrid structure and computation of quantum capacitance. There is charge transfer between PANI and RGO/SnO 2 , resulting in hydrogen bonding between graphene and PANI, which facilitates enhanced charge-storage performance for the ternary nanohybrid structure. Our experi- mental measurements and theoretical insight predict that the excellent electrochemical performance is due to the synergistic effect of rapid electron transportation between RGO/SnO 2 and PANI, and the system may be used as potential electrochemical charge-storage device. DOI: 10.1103/PhysRevApplied.14.024067 I. INTRODUCTION Nowadays, energy harvesting from solar and wind sources is an important task of the research community. Also, researchers are involved to develop an efficient device for storing this energy. Electrochemical capaci- tors or supercapacitors are considered to be promising energy-storage devices due to their high power density (10 kW/kg), long life cycles (10 6 ), and fast charge- discharge rate (1–30 s). These devices exhibit a high energy density (0.5–10 W h/kg) and power density com- pared with those of dielectric capacitors (<0.1 W h/kg) and batteries (<1000 W/kg) [1]. Supercapacitors are categorized based on the energy- storage principle, i.e., electric double-layer capacitors * brahma@barc.gov.in † dhanus2k3@yahoo.com (EDLCs) and pseudocapacitors. EDLCs store energy through the Helmholtz-double layer process. Pseudocapac- itors exhibit a high specific capacitance due to Faradaic reversible redox charge storage. Therefore, researchers have focused on the fabrication of pseudocapacitance elec- trode materials. It is well known that RuO 2 delivers a high pseudocapacitance (1400–2200 F/g). On the other hand, its high cost and toxicity limit its practical implementation in an energy-storage device. Hence, the thrust is towards other metal oxides, e.g., MnO 2 , ZnO, SnO 2 , and V 2 O 5 [2]. SnO 2 is a suitable electrode material, as a result of its high theoretical capacitance (782 mA/h), low cost, and high power density [3]. However, SnO 2 has a low conductivity, low cycling sta- bility, and poor transportation of electrolyte ions within the matrix. Substantial volume changes during the charge- discharge process degrade the SnO 2 life cycle, which impedes its practical usage. Carbon-based nanomaterials 2331-7019/20/14(2)/024067(18) 024067-1 © 2020 American Physical Society