Titania-Supported Photocatalytic Coatings of Cu₂O Nanoparticles Synthesized via Heterogeneous Nucleation

Mesoporous TiO₂ sol-gel coatings with a thickness of 122 nm and a porosity of 49% were prepared by dip-coating, followed by Cu₂O nanoparticle deposition onto the surface using a simple, one-step method: the TiO₂ coating was immersed in the reaction mixture and Cu₂O particles formed on the surface in a heterogeneous nucleation process. The crystallinity, size, shape, and structure of the samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, and scanning electron microscopy. Optical properties, layer thickness, and porosity were determined by UV-vis spectroscopy and spectroscopic ellipsometry. Cu₂O nanoparticles with an oblate spheroidal shape and cubic crystal structure formed on the surface, with an average particle size of 326 nm, and the surface coverage could be controlled by the reaction time. Photoactivity of the TiO₂/Cu₂O coatings was studied in dye photodegradation tests under UV and visible light, using methyl orange dye as a model pollutant. The samples showed significant photoactivity; the amount of Cu₂O particles and their surface coverage on titania played an important role. High surface coverage could be achieved in a simple one-step deposition process using heterogeneous nucleation, resulting in enhanced photoactivity under visible light, making this method suitable to produce photoactive coatings for a variety of applications, such as air and water purification.