CuO nanorods grown vertically on graphene nanosheets as a battery-type material for high-performance supercapacitor electrodes.

Miaomiao Zhai,Jingbo Hu,Ang Li

doi:10.1039/d0ra06758j

Abstract

This work reports the preparation and characterization of the CuO nanorods grown vertically on graphene nanosheets, denoted as CuO/rGO@NF. Graphene is deposited by electrostatic attraction showing the morphology of folded nanosheets, which improves the electrical conductivity of the electrode, while CuO is modified by filtered cathodic vacuum arc technology and subsequent electrochemical oxidation presenting the morphology of nanorods, which increases the contact area of active sites and shortens the ion and electronic diffusion path. The results show that the CuO/rGO@NF electrode deliver an ultrahigh specific capacity (2.51 C cm−2 at 2 mA cm−2), remarkable rate performance (64.6%) and improved conductivity. A symmetrical supercapacitor is assembled by two identical electrodes, presenting the maximum energy density of 38.35 W h kg−1 at a power density of 187.5 W kg−1. Therefore, the CuO/rGO@NF electrode can be used as a prospective electrode for energy storage devices. In addition, the whole electrode preparation process is short in time, safe and environmentally friendly, which provides a new idea for the preparation of other electrode materials.

Highlights

The large demand for portable electronic equipment greatly promotes the development of energy storage devices with small size, exibility, fast charging and discharging rate, high energy and power density, and long cycle life.[1,2,3] Supercapacitors, as a new type of energy storage device that ll the gap of energy density and power density between traditional capacitors and batteries, have attracted great attention in industry and scienti c research.[4,5,6]The electrode material is an important factor in determining the performance of supercapacitors
The results showed that the morphology of nanorod-liked copper oxide growing vertically on the graphene nanosheets
The Ni foam was immersed in the hydrochloric acid so that Ni atoms on the surface reacted with H+ in to form positively charged Ni2+

Summary

Introduction

The large demand for portable electronic equipment greatly promotes the development of energy storage devices with small size, exibility, fast charging and discharging rate, high energy and power density, and long cycle life.[1,2,3] Supercapacitors, as a new type of energy storage device that ll the gap of energy density and power density between traditional capacitors and batteries, have attracted great attention in industry and scienti c research.[4,5,6]. Battery-type electrodes store charges through the Faraday redox process, and the active substances are transition metal compounds, for instance the oxides of copper consisting of CuO,[11,12,13] Cu(OH)[2,14] Cu2O,15 Cu2+1O,16 which have the advantages of simple preparation, low cost, abundant reserves, many valence states, high electrochemical activity and large capacity, but poor conductivity and stability. Based on the above considerations, the Ni foam electrode modi ed by graphene and copper oxide (CuO/rGO@NF) was prepared by electrostatic adsorption and ltered cathodic vacuum arc technology with subsequent electrochemical oxidation. The symmetrical supercapacitor assembled by two CuO/rGO@NF electrodes exhibits high energy density of 38.35 W h kgÀ1 at the power density of 187.5 W kgÀ1 This CuO/rGO@NF electrode is superior to similar materials reported in other literatures, and the preparation method is simple and time-saving

Materials

Characterization

Electrochemical measurements

Results and discussion

Conclusions