Study on supercapacitance performance of TiO2 nanotube arrays modified by non-metal doping and Polyaniline electrodeposition methods

Highly ordered TiO2 nanotube arrays were synthesized by a two-step anodizing method. Although TiO2 nanotubes have excellent electrical and capacitive properties because they provide a unidirectional path for electron transfer. But these properties can be improved by effective methods such as non-metallic doping or by a conductive polymer. For this purpose, nitrogen and hydrogen doping methods and electrical deposition of polyaniline were used simultaneously to prepare the polyaniline-TiO2, polyaniline/N-TiO2, and polyaniline/H-TiO2 nanotube arrays samples. To evaluate the electrochemical and capacitive properties in more detail, cyclic voltammetry, electrochemical impedance spectroscopy, Matt-Schottky, and galvanostatic charge-discharge tests were performed. The results showed that the composite of TiO2 doped with hydrogen and deposited with polyaniline nanowires had the highest capacitance (5666 µF.Cm-2) at the current density of 100 µA/cm2, approximately 4.5 times more than polyaniline/TiO2 sample. It also has the lowest charge transfer resistance (0.008 Ωcm2) and the highest charge carrier density (1.63×1024cm-3). Increasing the density of charge carriers and decreasing the electrical resistance can be attributed to the fact that the hydrogen doping, the presence of oxygen vacancies, and conductive polymer increase the rate of separation of the charge carriers and decrease their recombination rate. Therefore, the electron transfer rate and the electric current increase.