Fifteen commercial titania (titanium(IV) oxide; TiO₂) powders were modified with gold by photodeposition to prepare photocatalysts that work under irradiation with light in the visible range (vis). The gold-modified titania (Au/TiO₂) powders were characterized by diffuse reflectance spectroscopy (DRS), field-emission scanning electron microscopy (FE-SEM), scanning transmission microscopy (STEM) and X-ray powder diffraction (XRD). It was shown that all tested powders could absorb visible light with an absorption maximum at localized surface plasmon resonance (LSPR) wavelengths (530–600 nm) and that the size and shape of gold nanoparticles determined the absorption ranges. The photocatalytic activity of Au/TiO₂ powders was examined both under ultraviolet and vis irradiation (mainly >450 nm) for acetic acid and 2-propanol photooxidation. It was found that the activity depended strongly on gold and titania properties, such as particle size and shape, surface area and crystalline form. Under vis irradiation, large rutile particles loaded with gold particles of a wide range of sizes showed the highest level of photocatalytic activity, possibly due to greater light absorption ability in a wide wavelength range resulting from transverse and longitudinal LSPR of rod-like gold particles. Action spectrum analyses showed that visible-light-induced oxidation of organic compounds by aerated gold–titania suspensions was initiated by excitation of LSPR absorption of gold. Although photocatalytic activity of nanosized gold particles under vis irradiation with a wavelength of ca. 430 nm and catalytic activity of gold-modified titania during dark reactions were also found, it was shown that the activities of Au/TiO₂ particles originated from activation of LSPR of gold by light of wavelength of 530–650 nm. Participation of molecular oxygen as an electron acceptor and titania as a conductor of electrons is suggested by comparing with results obtained under deaerated conditions and results obtained using a system containing gold-deposited silica instead of gold–titania, respectively. On the basis of these results, the mechanism of visible-light-induced oxidation of organic compounds on gold–titania is proposed.

Action spectrum analyses showed that visible light-induced oxidation of 2-propanol by aerated gold-modified titanium(IV) oxide (titania) suspensions is initiated by excitation of gold surface plasmon, and polychromatic irradiation experiments revealed that the photocatalytic reaction rate depends strongly on properties of titania, such as particle size, surface area and crystalline form (anatase or rutile) and on properties of gold deposits, such as size and shape.

Modification of titania with copper is a promising way to enhance the photocatalytic performance of TiO₂. The enhancement means the significant retardation of charge carriers’ recombination ratio and the introduction of visible light activity. This review focuses on two main ways of performance enhancement by copper species—i.e., originated from plasmonic properties of zero-valent copper (plasmonic photocatalysis) and heterojunctions between semiconductors (titania and copper oxides). The photocatalytic performance of copper-modified titania is discussed for oxidative reaction systems due to their importance for prospective applications in environmental purification. The review consists of the correlation between copper species and corresponding variants of photocatalytic mechanisms including novel systems of cascade heterojunctions. The problem of stability of copper species on titania, and the methods of its improvement are also discussed as important factors for future applications. As a new trend in the preparation of copper-modified titania photocatalyst, the role of particle morphology (faceted particles, core-shell structures) is also described. Finally, in the conclusion section, perspectives, challenges and recommendations for future research on copper-modified titania are formulated.