Modifying TiO2 nanotube using N-doping and electrochemical reductive doping as a supercapacitor electrode

The relatively small specific capacitance along with poor electrochemical activity and weak electrical conductivity of TiO2 has resulted in several studies on the methods of modifying TiO2. In this study, a different mechanism for improving the electrochemical properties of TiO2 nanotubes is employed. Nitrogen doping of TiO2 nanotube arrays fabricated using two-step anodization was used to narrow the bandgap of TNTs as a non-metal doping technique. To better demonstrate the impact of the nitrogen content on enhancing the electrochemical activity, TNTs were immersed in 0.5, 1, 2, 4, and 8 molars of ammonia solution. Electrochemical reductive doping was implemented on TNT and N-TNT. The phase structure and surface morphologies of the as-prepared TiO2 nanotubes were identified by X-ray diffraction (XRD), field scanning electron microscope (FSEM) and Fourier transformed infrared spectroscopy (FT-IR) measurements. The electrochemical response of the TiO2 NTAs following nitrogen and electrochemical doping was evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge tests, and electrochemical impedance spectroscopy (EIS). The electrochemical measurements of the modified samples confirmed that a noticeable improvement was achieved in the electrochemical behavior and that the areal capacitance of R-N-TNT was roughly 400 orders of magnitude greater than that of TNT with long-term stability (93% of its initial capacitance after 500 cycles).