High-performance asymmetric supercapacitors based on core/shell cobalt oxide/carbon nanowire arrays with enhanced electrochemical energy storage

• We prepared a self-supported porous Co3O4/C core/shell nanowire array.
• Core/shell nanowire array showed high pseudo-capacitive properties.
• Core/shell array structure was favorable for fast ion and electron transfer.

High-reactivity electrode materials are indispensible for developing high-performance electrochemical energy storage devices. Herein, we report self-supported core/shell Co3O4/C nanowire arrays by using hydrothermal synthesis and chemical vapor deposition methods. A uniform and thin carbon shell is coated on the surface of Co3O4 nanowire forming core/shell nanowires with diameters of ∼100 nm. Asymmetric supercapacitors have been assembled with the core/shell Co3O4/C nanowire arrays as the positive electrode and activated carbon (AC) as the negative electrode. The core/shell Co3O4/C nanowire arrays exhibit a specific capacity of 116 mAh g−1 at the working current of 100 mA (4 A g−1), and a long cycle life along with ∼ 92% retention after 8000 cycles at 4 A g−1, higher than the unmodified Co3O4 nanowire arrays (81 mAh g−1 at 4 A g−1). The introduction of uniform carbon layer into the core/shell structure is favorable for the enhancement of supercapacitor due to the improved electrical conductivity and reaction kinetics.

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