One-step synthesis of the reduced graphene oxide@NiO composites for supercapacitor electrodes by electrode-assisted plasma electrolysis

An electrode-assisted plasma electrolysis is developed to synthesize the reduced graphene oxide@NiO (rGO@ NiO) composites as supercapacitor electrode materials. The method is fast and efficient, realizing one-step synthesis for the rGO@NiO composites. The composition, morphologies, electrochemical properties, and deposition dynamics of rGO@NiO composites are systematically investigated in current work. The results of X-ray diffraction (XRD) and Raman spectra show that NiO is synthesized on the rGO. The weight ratio of NiO in the rGO@NiO composites is about 50.2% by thermo gravimetric analysis (TGA). Transmission electron microscope (TEM) exhibits that lots of nanoparticles distribute uniformly relatively on the rGO, and the diameter of nanoparticles is mostly in 30-80 nm. The as-prepared rGO@NiO composite displays a specific capacitance of 1093 F.g(-1) at 1 A.g(-1) current density. In addition, it exhibits an excellent cycle stability, and still keeps similar to 87% of the original capacitance and 90.6% coulombic efficiency after 5000 cycles. Based on the electrochemical theory, the electrode-assisted plasma electrolysis process is dominated by the electrochemical polarization, shortening the deposition process and realizing a fast synthesis for the rGO@NiO composites. The synthesis method, electrode-assisted plasma electrolysis, presents a promising route for the efficient and rapid preparation of rGO-metal oxide composites as energy storage materials. (c) 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).