ORIGINAL PAPER NiO@CuO@Cu bilayered electrode: two-step electrochemical synthesis supercapacitor properties Ahmed AL-Osta 1 & Bushra Saleh Samer 2 & Vijaykumar V. Jadhav 3 & Umesh T. Nakate 1 & Rajaram S. Mane 1 & Mu. Naushad 4 Received: 29 July 2016 /Revised: 19 September 2016 /Accepted: 19 December 2016 # Springer-Verlag Berlin Heidelberg 2017 Abstract Present work deals with a two-step synthesis and elec- trochemical properties of nickel oxide @copper oxide@copper (NiO@CuO@Cu) bilayered electrode. In the first step, anodiza- tion (40 V for 25 min) of Cu foil has been carried out for forming Cu-hydroxide@Cu which when annealed at 300 °C for 1 h pro- duces CuO@Cu. In the second step, Ni-hydroxide is deposited onto CuO@Cu by applying current density of 0.03 A/cm 2 for 3 min which when re-annealed at 300 °C for 1 h gives out NiO@CuO@Cu bilayered electrode. Obtained NiO@CuO@Cu bilayered electrode demonstrates separate CuO and NiO phases. The electrochemical properties have obtained using cyclic volt- ammetry, galvonostatic charge-discharge, and Nyquist plot mea- surements that reveal an importance of NiO@CuO@Cu as a potential electrode material in the electrochemical supercapacitor application with 58.14, 51.25, and 4.73 F g -1 values in 0.5 M, NaOH, KOH, and Na 2 SO 4 electrolytes, respectively, measured at 2 mVs -1 scan rate. Keywords Nanostructures . Electrochemical techniques . Thin films . Alloys . Electrochemical synthesis Introduction Anodization, a versatile solution-based method, has been used for synthesizing various nanostructures of various metal oxides like titanium dioxide (TiO 2 ), copper oxide (CuO, Cu 2 O), cobalt oxide (CoO), nickel oxide (NiO), aluminum oxide (Al 2 O 3 ), and tin oxide (SnO 2 ) which are being used in devices like batteries, dye-sensitized solar cells, and electrochemical supercapacitors (ESs) [1–3]. Basically, ESs have high energy and power den- sities compared with fuel cells and conventional batteries [4]. Based on their operation mechanisms, they are classified into two types: non-faradaic, the so-called electrical double-layer capacitors (EDLC), and faradaic, i.e., pseudocapacitors [5]. It is found that prior ESs exhibit smaller specific capacitance (SC) and long-term durability whereas the latter demonstrates higher SC and limited life time. The higher SC performance in the former is due to their higher conductivity and surface area and faster charging time [6]. Few materials like conducting poly- mers and metal oxides have exhibited considerable redox reac- tions with increased SC values [5, 7]. Electrode materials of transition metal oxides in pseudocapacitors are highly recom- mended as they reveal more than one oxidation states which, in turn, facilitate excess redox reactions [8]. Though ruthenium oxide is one of the master materials for this application, its cost is non-affordable and thereby is beyond the level of commer- cialization. Researchers are actively looking at alternative elec- trode materials which are cheap, eco-friendly, abundant, and easily available. As discussed above, Cu is in two oxide forms, i.e., cuprous oxide (Cu 2 O) and cupric oxide (CuO), with band gaps of 2.0 and 1.2 eV, respectively, which are good candidates for solar cells, catalysts, sensors, and optoelectrochemical de- vice applications [9, 10]. Due to Cu vacancies, CuO is a p-type semiconductor [11–13]. However, its poor electrochemical ac- tivity, as well as low discharge voltage in alkaline electrolyte (compared with CoO and NiO) has restricted its direct use in * Rajaram S. Mane rsmane_2000@yahoo.com * Mu. Naushad shad123@gmail.com 1 Center for Nanomaterials & Energy Devices, School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded, M.S. 431606, India 2 School of Chemical Sciences, Swami Ramanand Teerth Marathwada University, Nanded, M.S. 431606, India 3 Department of Physics, Shivaji Mahavidyalya, Udgir, Dist, Latur, M.S., India 4 Department of Chemistry, College of Science, King Saud University, Riyadh, Saudi Arabia J Solid State Electrochem DOI 10.1007/s10008-016-3489-8