Hierarchical nanocomposite electrodes based on titanium nitride and carbon nanotubes for micro-supercapacitors

• Hierarchical TiN/CNT electrodes were fabricated.
• These electrodes bridge between EDLCs and pseudocapacitors.
• The electrochemical charge storage mechanism in TiN was proposed.

Electrochemical capacitors that can store high density of electrical energy with fast power delivering and long operating life time are important for many challenging applications. Tremendous research efforts aim at developing electrodes which gather the advantages of both electrochemical double layer capacitors (high power density, long cycling life) and pseudo-capacitors (high energy density). Here we highlight the design of hierarchically composite electrodes consisting of porous and nanostructured TiN grown on vertically aligned CNTs as high-performance electrode for micro-supercapacitors. The electrodes, which are deposited on silicon substrates, exhibit an areal capacitance as high as 18.3 mF cm−2 at 1 V s−1 that can be further enhanced by increasing the TiN layer thickness. Furthermore, this capacitance is maintained over 20,000 cycles. We propose that such high performance originates from the high surface area of the electrodes having a nanoporous structure, as well as to their specific surface chemistry, which contains large amount of oxygen vacancies as a result of nitrogen self-doping of anatase which forms at the TiN surface.

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