Mechanism of Co3O4-TiO2 Nanocomposite Formation with Enhanced Photocatalytic Performance

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.