Effect of Tin+ defects on electrochemical properties of highly-ordered titania nanotube arrays

In this paper, highly-ordered TiO2 nanotube (TNT) electrodes fabricated by anodization at 20 V in 0.1 M F−-based solution were annealed in O2, N2 and CO respectively. The surface properties of the TiO2 electrodes after annealing treatment by different gases were studied by means of photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of the TNT electrodes were investigated by cyclic voltammetry, steady-state polarization and photocurrent response measurements. The results showed that Tin+ (n = 0–3) cations and oxygen vacancies existed in the TNT electrode after annealing in CO, leading to a very efficient electron transfer rate of 1.34 × 10− 3 cm/s. Steady-state polarization measurement and photocurrent response demonstrated that the electrode potential of oxygen evolution reaction (OER) reduced by 20% and the photocurrent response increased by 50% for CO-annealed TNT electrode compared with O2-annealed TNT electrode.