Mechanism of Co3O4-TiO2 Nanocomposite Formation with Enhanced Photocatalytic Performance

Abstract

TiO₂ nanotubes are tubular structures that have garnered significant attention in materials science and engineering due to their unique properties and diverse applications. In this study, highly ordered and well aligned TiO₂ nanotubes were successfully synthesized through anodization of Ti foil in ethylene glycol (C₂H₆O₂) containing ammonium fluoride (NH₄F) and hydrogen peroxide (H₂O₂) at 60 V for 30 minutes. The effectiveness of TiO₂ as a photocatalyst under solar light is limited by its wide band gap and high recombination rate of charge carriers. To address these limitations, TiO₂ nanotubes were modified with cobalt oxide. The resulting Co₃O₄-TiO₂ nanocomposite was synthesized using a wet impregnation technique, aiming to enhance the photocatalytic performance of TiO₂ nanotubes across a broader range of the solar spectrum. The formation of Co₃O₄-TiO₂ nanocomposite is by immersing the TiO₂ nanotubes in the metal salt precursor solution of Co(NO₃)₂ for a certain soaking period. The soaking cycle was repeated a few times to ensure the deposition of cobalt oxide nanostructures on the TiO₂ nanotube samples. This diffusion interstitial process via wet impregnation was time dependent, which altered the amount of cobalt loaded on the nanotube's surface. The addition of cobalt significantly improved the photodegradation activity of the nanotubes under visible light, outperforming bare TiO₂ nanotubes. This enhancement is likely due to the cobalt acting as shallow traps, which effectively promote the separation of photogenerated charge carriers.