In-situ electrochemical exfoliation of Highly Oriented Pyrolytic Graphite as a new substrate for electrodeposition of flower like nickel hydroxide: application as a new high-performance supercapacitor

摘要

Demand for more efficient energy storage devices stimulates efforts to search and develop new materials and composites with promising properties. In this regard, composite materials, including carbonaceous materials and metal oxides have attracted a great attention due to better electrochemical performance as compared to their single material analogues. For the first time, herein, we report a new and simple procedure for preparing porous highly oriented pyrolytic graphiteickel hydroxide composite (P-HOPG/Ni(OH)(2)) via a fast and simple two-step electrochemical method including potentiostatic routes. In the first step, a low anodic potential (2 V) was applied to pristine HOPG in 0.5 M H2SO4 solution for 240 s to produce porous P-HOPG, followed by a cathodic potential (-1.5 V) in acetate buffer solution to reduce surface functional groups and increase conductivity of the electrode. In the next step, the resulting porous material composed of graphene-like sheets was used as a new binder-free substrate for electrodeposition of flower-like nickel hydroxide structures at a constant potential of -1.3 V for 300 s. This new procedure does not need any thermal treatment of the substrate at high temperatures. The resulting modified electrode afforded extremely high areal capacitance of 5.2 F cm(-2) at a current density of 2 mA cm(-2). FE-SEM results showed that nickel hydroxide nanoflower-like structures deposited on the graphene-like sheets in P-HOPG substrate. This new morphology facilitates electron transfer through the modified electrode. A good cycling stability was observed for the modified electrodes in alkaline media. EIS measurements showed low values of internal resistance (R-s) and charge transfer resistance (R-ct) for the modified electrodes, indicating that the prepared nanocomposite is appropriate for supercapacitor applications. (c) 2016 Elsevier Ltd. All rights reserved.