Layered sphere-shaped TiO₂ capped with gold nanoparticles on structural defects and their catalysis of formaldehyde oxidation

We describe here a one-step method for the synthesis of Au/TiO₂ nanosphere materials, which were formed by layered deposition of multiple anatase TiO₂ nanosheets. The Au nanoparticles were stabilized by structural defects in each TiO₂ nanosheet, including crystal steps and edges, thereby fixing the Au-TiO₂ perimeter interface. Reactant transfer occurred along the gaps between these TiO₂ nanosheet layers and in contact with catalytically active sites at the Au-TiO₂ interface. The doped Au induced the formation of oxygen vacancies in the Au-TiO₂ interface. Such vacancies are essential for generating active oxygen species (*O^-) on the TiO₂ surface and Ti³⁺ ions in bulk TiO₂. These ions can then form Ti³⁺-O^--Ti⁴⁺ species, which are known to enhance the catalytic activity of formaldehyde (HCHO) oxidation. These studies on structural and oxygen vacancy defects in Au/TiO₂ samples provide a theoretical foundation for the catalytic mechanism of HCHO oxidation on oxide-supported Au materials.