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Recently, attention has been focused on the synthesis and application of nanocomposites for supercapacitors, which can have superior electrochemical performance than single structured materials. Here, we report a carbon-coated TiO2/Co3O4 ternary hybrid nanocomposite (TiO2@C/Co) electrode for supercapacitors. A carbon layer was directly introduced onto the TiO2 surface via thermal vapor deposition. The carbon layer provides anchoring sites for the deposition of Co3O4, which was introduced onto the carbon-coated TiO2 surface by hydrazine and the thermal oxidation method. The TiO2@C/Co electrode exhibits much higher charge storage capacity relative to pristine TiO2, carbon-coated TiO2, and pristine Co3O4, showing a specific capacitance of 392.4 F g(-1) at a scan rate of 5 mV s(-1) with 76.2% rate performance from 5 to 500 mV s(-1) in 1 M KOH aqueous solution electrolyte. This outstanding electrochemical performance can be attributed to the high conductivity and high pseudo-capacitive contributions of the nanoscale particles. To evaluate the capacitive performance of a supercapacitor device employing the TiO2@C/Co electrode, we have successfully assembled TiO2@C/Co//activated carbon (AC) asymmetric supercapacitors. The optimized TiO2@C/Co//AC supercapacitor could be cycled reversibly in the voltage range from 0 to 1.5 V, and it exhibits a specific capacitance of 59.35 F g(-1) at a scan rate of 5 mV s(-1) with a specific capacitance loss of 15.4% after 5000 charge-discharge cycles. These encouraging results show great potential in terms of developing high-capacitive energy storage devices for practical applications.

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