Journal of Power Sources 436 (2019) 226826 0378-7753/© 2019 Elsevier B.V. All rights reserved. Vertically aligned nanostructured FeOOH@MnO 2 core shell electrode with better areal capacitance Rahul B. Pujari a , Swati J. Patil a , Jongsung Park a , Arunkumar Shanmugasundaram a , Dong-Weon Lee a, b, * a MEMS and Nanotechnology Laboratory, School of Mechanical System Engineering, Chonnam National University, Gwangju, 61186, Republic of Korea b Center for Next-generation Sensor Research and Development, Chonnam National University, Gwangju, 61186, Republic of Korea HIGHLIGHTS G R A P H I C A L ABSTRACT � 1-D FeOOH@MnO 2 core shell nano- structure is prepared by hydrothermal route. � FeOOH@MnO 2 applied for electro- chemical charge storage in 0–1 V/AgCl window. � Electro-active MnO 2 shell supplies elec- trons and FeOOH nanorods transfer them. � FeOOH@MnO 2 core shell nanostructure shows 0.252 Fcm 2 capacitance at 1 mAcm 2 . � FeOOH@MnO 2 //FeOOH@MnO 2 SC gives 0.05 mWhcm 2 energy and 1.5 mWcm 2 power. A R T I C L E INFO Keywords: Areal capacitance Cyclic voltammetry Supercapacitor Energy density FeOOH@MnO 2 Thin flm ABSTRACT Present work focuses on hydrothermal preparation of FeOOH@MnO 2 core shell as a vertically aligned 1-D nanostructure and improvement in electrochemical charge storage by utilizing MnO 2 nanostructure as an active electrode material and vertically aligned FeOOH nanorods for one dimensional electron transfer paths. A FeOOH@MnO 2 core shell thin flm electrode gives maximum capacitance of 0.252 Fcm 2 for the applied current density of 1 mAcm 2 and maintains 99.5% capacitance retention for 2000 charge discharge cycles at 5 mAcm 2 that attributes to better capacitive charge storage in the material. Assembled solid state symmetric electro- chemical capacitor of FeOOH@MnO 2 electrode yields maximum of 0.05 mWhcm 2 energy density with power delivery of 1.5 mWcm 2 . 1. Introduction Supercapacitors or electrochemical capacitors are modern energy storage devices with boosted energy density than dielectric capacitors and higher power density than secondary batteries [1–4]. Pseudocapacitors store higher energy density by the courtesy of higher redox activity metal oxide or conducting polymer electrode materials than electric double layer capacitors (EDLCs), which are formed with electrodes of carbon allotropes such as graphene oxide and carbon nanotubes [5,6]. However, the energy density of pseudocapacitors * Corresponding author. MEMS and Nanotechnology Laboratory, School of Mechanical System Engineering, Chonnam National University, Gwangju, 61186, Republic of Korea. E-mail address: mems@jnu.ac.kr (D.-W. Lee). Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour https://doi.org/10.1016/j.jpowsour.2019.226826 Received 13 March 2019; Received in revised form 24 June 2019; Accepted 27 June 2019