Abstract
Cauliflower‐like Co3O4/three‐dimensional (3D) graphene nanocomposite material was synthesized by a facile two‐step synthesis route (heat reduction of graphite oxide (GO) and hydrothermal synthesis of Co3O4). The phase composition, morphology, and structure of the as‐obtained products were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), and X‐ray diffraction (XRD). Electrochemical properties as supercapacitor electrode materials were systematically investigated by cyclic voltammetry (CV) and constant current charge‐discharge tests. It was found that the Co3O4/3D graphene composite showed a maximum specific capacitance of 863 F g−1, which was obtained by means of CVs at a scan rate of 1 mV s−1 in 6 M KOH aqueous solution. Moreover, the composite exhibited improved cycling stability after 1,000 cycles. The good supercapacitor performance is ascribed to the combination of 3D graphene and cauliflower‐like Co3O4, which leads to a strong synergistic effect to remarkably boost the utilization ratio of Co3O4 and graphene for high capacitance.
Highlights
With the impending energy crisis, the concerns about the environment are increasing
The electrical double-layer capacitor (EDLC) roots in charge separation at the electrode/solution interface, whereas the Faradic pseudocapacitance arises from the reversible redox reactions occurring within the supercapacitor electrode material [10, 11]
For 3D graphene, a broad peak was observed at 25.6∘, which is attributed to the C (002) plane [31, 35]
Summary
With the impending energy crisis, the concerns about the environment are increasing. The research on alternative energy conversion and storage systems which have high efficiency, low cost, and environmental benignity is urgently called for. Supercapacitors, known as electrochemical capacitors or ultracapacitors, have been intensively investigated in the fields of energy storage and conversion [1, 2]. Compared with the conventional capacitors and secondary batteries, supercapacitors can provide high power density, strong cycle stability, and remarkable pulse charge-discharge properties [1,2,3,4,5]. They are being employed in different applications [1, 6,7,8], such as mobile electronic devices, backup power supplies, and hybrid electric vehicles. Tremendous attention has been focused on the development of new materials for supercapacitor electrodes with higher specific capacitance and better cyclic life whilst using environmentally benign materials in processable ways
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