A plausible impact on the role of pulses in anodized TiO2 nanotube arrays enhancing Ti3+ defects

This paper presents a systematic investigation on the growth of TiO2 nanotubes (NTs) by modifying the continuity in the applied potential through conventional one-step electrochemical anodization (CEA), paused electrochemical anodization (PEA), two-step electrochemical anodization (TEA), and pulsed electrochemical anodization (PLA). The essence of this research pertains to understanding the significance of surface solid fraction factor (ψ) in relation to the density of surface defects. Additionally, in order to comprehend and incorporate the influence of cracks on surface defects and carrier transport, the reported ψ has been modified for the first time. Moreover, this attempt involves the use of H2O2 as an electrolytic oxidizer for the first time in PEA, TEA, and PLA techniques to explore the possibility in creating ripple free NTs. UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), photoluminescence, and X-ray photoelectron spectroscopy (XPS) provided insights into the band gap and quantification of surface defects for NTs anodized via continuous and pulsed modes. The effect of voltage continuity on % porosity of the TiO2 NT arrays was investigated. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques were also carried out to determine the electrical properties of the prepared TiO2 NT arrays.