Fabrication of Durable Ordered Ta₂O₅ Nanotube Arrays Decorated with Bi₂S₃ Quantum Dots

One of the most important challenges in the fabrication of ordered tantalum pentaoxide (Ta₂O₅) nanotube arrays (NTs) via the electrochemical method is the formation of nanotubes that adhere well to the Ta substrate. In this paper, we propose a new protocol that allows tight-fitting Ta₂O₅ nanotubes to be obtained through the anodic oxidation of tantalum foil. Moreover, to enhance their activity in the photocatalytic reaction, in this study, they have been decorated by nontoxic bismuth sulfide (Bi₂S₃) quantum dots (QDs) via a simple successive ionic layer adsorption and reaction (SILAR) method. Transmission electron microscopy (TEM) analysis revealed that quantum dots with a size in the range of 6-11 nm were located both inside and on the external surfaces of the Ta₂O₅ NTs. The effect of the anodization time and annealing conditions, as well as the effect of cycle numbers in the SILAR method, on the surface properties and photoactivity of Ta₂O₅ nanotubes and Bi₂S₃/Ta₂O₅ composites have been investigated. The Ta₂O₅ nanotubes decorated with Bi₂S₃ QDs exhibit high photocatalytic activity in the toluene degradation reaction, i.e., 99% of toluene (C₀ = 200 ppm) was degraded after 5 min of UV-Vis irradiation. Therefore, the proposed anodic oxidation of tantalum (Ta) foil followed by SILAR decorating allows a photocatalytic surface, ready to use for pollutant degradation in the gas phase, to be obtained.