Reduced graphene/nanostructured cobalt oxide nanocomposite for enhanced electrochemical performance of supercapacitor applications Suresh Sagadevan a,⇑ , A.R. Marlinda a , Mohd. Rafie Johan a , Ahmad Umar b, * , H. Fouad c,d , Othman Y. Alothman e , Usama Khaled f,g , M.S. Akhtar h, * , M.M. Shahid i a Nanotechnology & Catalysis Research Centre, University of Malaya, Malaysia b Department of Chemistry, Faculty of Science and Arts and Promising Centre for Sensors and Electronic Devices, Najran University, Najran 11001, Saudi Arabia c Applied Medical Science Dept., Community College, King Saud University, Riyadh, Saudi Arabia d Department of Biomedical Engineering, Faculty of Engineering, Helwan University, Egypt e Department of Chemical Engineering, College of Engineering, King Saud University, Riyadh, Saudi Arabia f Department of Electrical Engineering, College of Engineering, King Saud University, Riyadh, Saudi Arabia g Department of Electrical Engineering, Faculty of Energy Engineering, Aswan University, Aswan 81528, Egypt h New and Renewable Energy Materials Development Center (NewREC), Chonbuk National University, Jeonbuk 56332, Republic of Korea i Higher Institution Centre of Excellence (HICoE), UM Power Energy Dedicated Advanced Centre (UMPEDAC), 59990 Kuala Lumpur, Malaysia graphical abstract article info Article history: Received 7 June 2019 Revised 19 September 2019 Accepted 21 September 2019 Available online 23 September 2019 Keywords: Co 3 O 4 rGO Nanocomposite Electrical properties Electrochemical and supercapacitor abstract We demonstrate the preparation of nanostructures cobalt oxide/reduced graphene oxide (Co 3 O 4 /rGO) nanocomposites by a simple one-step cost-effective hydrothermal technique for possible electrode mate- rials in supercapacitor application. The X-ray diffraction patterns were employed to confirm the nanocomposite crystal system of Co 3 O 4 /rGO by demonstrating the existence of normal cubic spinel struc- ture of Co 3 O 4 in the matrix of Co 3 O 4 /rGO nanocomposite. FTIR and FT-Raman studies manifested the structural behaviour and quality of prepared Co 3 O 4 /rGO nanocomposite. The optical properties of the nanocomposite Co 3 O 4 /rGO have been investigated by UV absorption spectra. The SEM/TEM images showed that the Co 3 O 4 nanoparticles in the Co 3 O 4 /rGO nanocomposites were covered over the surface of the rGO sheets. The electrical properties were analyzed in terms of real and imaginary permittivity, dielectric loss and AC conductivity. The electrocatalytic activities of synthesized Co 3 O 4 /rGO nanocompos- ites were determined by cyclic voltammetry and charge-discharge cycle to evaluate the supercapacitive performance. The specific capacitance of 754 Fg À1 was recorded for Co 3 O 4 /rGO nanocomposite based electrode in three electrode cell system. The electrode material exhibited an acceptable capability and excellent long-term cyclic stability by maintaining 96% after 1000 continuous cycles. These results showed that the prepared sample could be an ideal candidate for high-energy application as electrode https://doi.org/10.1016/j.jcis.2019.09.081 0021-9797/Ó 2019 Elsevier Inc. All rights reserved. ⇑ Corresponding authors. E-mail addresses: drsureshnano@gmail.com (S. Sagadevan), ahmadumar786@gmail.com (A. Umar), shaheerakhtar@jbnu.ac.kr (M.S. Akhtar). Journal of Colloid and Interface Science 558 (2020) 68–77 Contents lists available at ScienceDirect Journal of Colloid and Interface Science journal homepage: www.elsevier.com/locate/jcis