Metal-organic chemical vapor deposition of anatase titania on multiwalled carbon nanotubes for electrochemical capacitors

In practice, the capacitance from the electrochemical double layer formation on porous carbon-based electrodes is still below preferred values, limiting their use in electrochemical capacitors. The current drive is to innovate ways that generate additional capacitance in the electrochemical double layer capacitive nature of carbon nanomaterials towards both a high specific energy density (Es) and power density (Ps). Herein we report the use of metal-organic chemical vapor deposition (MOCVD) to coat multiwalled carbon nanotubes (MWCNTs) with anatase titanium dioxide (TiO2) to induce pseudocapacitive charge storage characteristics on a carbon-based electrode. The study shows that MWCNTs were coated in bundles, and targeted TiO2 loadings were successfully attained, though the TiO2 agglomerates also increased with TiO2 wt.%. The 10 wt.% TiO2 TiO2-MWCNT material displayed the best capacitive behavior with associated specific discharge capacitance (Cd), Es, and Ps values of 907 F kg−1, 55.56 Wh kg−1, and 2.78 W kg−1 at 0.1 A g−1, respectively, due to the synergistic effect of the two components of the composite. Additionally, the integral capacitance (Cs) of the 20 wt.% TiO2 material was enhanced more than 5000-fold relative to that of the 5 wt.% TiO2 TiO2-MWCNT composite at higher scan speeds of 100 and 200 mV s−1. Electrochemical measurements further demonstrated the possible positive tuning of capacitive characteristics (charge/discharge rates, Cd and Cs) with TiO2 wt.% control. The MOCVD synthesis method imparted the TiO2-MWCNT composites with suitable traits that showed high potential in improving physicochemical processes favorable in electrical energy storage. © 2022 The Authors. Energy Science & Engineering published by the Society of Chemical Industry and John Wiley & Sons Ltd.