Electrochemical fabrication of Ni or Ni(OH)2@Ni nanoparticle-decorated reduced graphene oxide for supercapacitor applications

Abstract

Electrochemical-reduced graphene oxide (ERGO) nanocomposites decorated with Ni or Ni(OH)2@Ni nanoparticles (NPs) were fabricated directly on Au electrodes by one-pot electrochemical approach. This facile, rapid, scalable, and green approach is based on the simultaneous co-reduction of GO and Ni2+ ions at ambient conditions from an aqueous solution without using specific reducing and any other protective agents. The as-prepared NiNP/ERGO could be easily converted into Ni(OH)2@NiNP/ERGO by electrochemical cycling in alkaline solutions. Characterization with field-emission scanning electron microscopy, transmission electron spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy illustrated that the GO were successfully reduced into wrinkled and scrambled ERGO structures and decorated homogenously by very stable and well-separated NiNPs. The electrochemical performances of the as-prepared NiNP/ERGO and the activated Ni(OH)2@NiNP/ERGO electrodes were evaluated via cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The as-prepared NiNP/ERGO electrodes exhibited a high specific capacity of 293 C g−1 at 4 A g−1. After cycling for 500 times, the surface of NiNPs on ERGO were converted into Ni(OH)2@NiNP/ERGO with a superior specific capacity of 785 C g−1 at 4 A g−1. A maximum capacity of 948 C g−1 was obtained at 4 A g−1 after 1500 cycles, and excellent cycling stability with 92% capacitiy retention was observed after more than 2000 additional cycles. The electrochemical performance of NiNP/ERGO and Ni(OH)2@NiNP/ERGO nanocomposites renders them as potential electrodes in supercapacitors. The present one-pot electrochemical strategy could also be used in the decoration of GO by other metal and metal hydroxides.