Improved visible photocatalytic CO oxidation of CoTiO₃ nanotubes by surface engineering and Au nanoparticle loading

The tubular structure photocatalyst, known for its excellent light absorption and mass diffusion properties, represents an attractive class of photocatalytic materials for the removal of toxic gaseous pollutants. However, the availability of adsorption activation sites and the separation of photogenerated charges remain insufficient, making improvements in these aspects meaningful. In this study, CoTiO₃ nanotubes (denoted as CTO) are fabricated by a coaxial electrospinning technique followed by molten salt treatment. Subsequently, oxygen vacancies (Ovs) are created within the CTO by a vacuum-assisted hydrogen reduction strategy using NaBH₄. Meanwhile, ultrafine Au nanoparticles (NPs) are uniformly anchored onto the surface of CTOvs by an in situ frozen photodeposition strategy, producing Au-CTOvs. The optimized Au-CTOv photocatalyst exhibits 2.7-fold enhancement in CO photooxidation compared to pristine CTO and is superior to N-doped TiO₂. The experimental results confirm that the exceptional photoactivity can be attributed to three synergistic factors: the construction of the void and tubular structure accelerates mass transfer, the creation of Ovs on the nanotubes facilitates CO adsorption, and the anchoring of Au NPs improves charge separation and O₂ activation.