Abstract
A hierarchical electrode structure, consisting of cobalt oxide and nitrogen-doped graphene foam (NGF), has been fabricated with the aim of achieving enhanced charge-storage performance. Characterization of the material via electron microscopy and Raman spectroscopy demonstrates that the Co3O4 nanosheets grow vertically on NGF and the nanosheets are mesoporous with pore diameters between 3 and 8 nm. The Co3O4/NGF electrode shows an enhanced charge-storage performance, attributed to the 3D hierarchical structure and the synergistic effect of Co3O4 and NGF. The present study shows that specific capacitances as high as 451 F g(-1) can be obtained, indicating that high-performance electrochemical capacitors can be made using electrode materials with advanced structures. The present electrode design can be readily extended to other electroactive materials and their composites.
Highlights
Supercapacitors (SCs, called electrochemical capacitors or ultracapacitors), represent a unique class of electrical energy storage devices, which have been extensively studied in recent years because of their high power density, fast charge− discharge rate, and long cycle life.[1]
In the 1970s, Conway and others recognized that reversible redox reactions occurring at or near the surface of an appropriate electrode material lead to EDLC-like electrochemical features but the redox processes lead to much greater charge storage.[1]
The above small separation of redox peaks is not strictly defined, and many literature reports consider the active electrode materials as supercapacitor, even though the separation of peaks is on the order of 0.1 V.7−11 The performance of PCs is mainly determined by the conductivity and surface area of the electrodes
Summary
Supercapacitors (SCs, called electrochemical capacitors or ultracapacitors), represent a unique class of electrical energy storage devices, which have been extensively studied in recent years because of their high power density, fast charge− discharge rate, and long cycle life.[1]. A novel bottom-up design of 3D highperformance electrodes, namely mesoporous vertical Co3O4 nanosheet arrays supported on CVD grown nitrogen-doped graphene foam, is demonstrated. Serving as a free-standing monolithic electrode, this material demonstrates improved performance compared to the previously sreuppoerrcteadpacCitoo3rOap[4] plaicnadtiognrsa.2p2h−e2n5eTocothmepboessitteosf, suggested for our knowledge, it is the first report of a cobalt oxide and nitrogen doped CVD graphene foam composite with this unique 3D hierarchical structure. Preparation of Mesoporous Vertical Co3O4 Nanosheet/ Nitrogen-Doped Graphene Foam (Co3O4/NGF) Composite. The electrodeposition was performed in a three-electrode cell consisting of NGF as working electrode, a platinum mesh (Aldrich, 52 mesh, surface area: 2 cm × 2 cm) counter electrode and saturated calomel electrode (SCE) reference electrode at room temperature. Working electrodes during the electrodeposition process, are named Co3O4/Ni foam and Co3O4/NGF, respectively. Where Idischarge is the discharge current, Δt is the discharge time, ΔV is the change of potential and m is the mass of cobalt oxide and graphene foam/Ni foam composite
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