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 TNTs( TiO2 nanotube arrays). In this study, different mechanisms for improving the electrochemical properties of TiO2 nanotubes are employed; Nitrogen doping of TNTs in different concentrations of ammonia solution (named N-TNTs), then conducting electrochemical reductive doping on optimized TNTs ( named N-R-TNTs). .Nitrogen doping of TNTs 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 TNTs and N-TNTs. The phase structure and surface morphologies of the as-prepared TNTs were identified by X-ray diffraction (XRD), Field Emission Electron Microscope (FESEM) and Fourier transformed infrared spectroscopy (FT-IR) measurements. The electrochemical response of the TNTs 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 TNTs with long-term stability (93% of its initial capacitance after 500 cycles).