Modification strategies of TiO2 based photocatalysts for enhanced visible light activity and energy storage ability: A review

Titanium dioxide (TiO2) as a photocatalyst received remarkable attention owing to its potential applications in environmental remediation and energy production. TiO2 owns an indirect band gap of ∼ 3.2 eV, chemical stability, photocorrosion resistant, low toxicity and the photocatalyst is sensitive to ultraviolet (UV) light, which is < 5.0% of the overall solar intensity this is why possesses low quantum efficiency and photocatalytic activity. To increase the photocatalytic performance in the visible light range and to enhance the number of active sites on the material surface to promote its adsorption capacity, also to retard the recombination rate of photoinduced charge carriers and to induce energy storage ability, various modification strategies are used to modify TiO2 structure. Therefore, this work comprehensively reviews the emergence of TiO2 photocatalysis, modification strategies to engineer its wide band gap for the UV-Vis-NIR light range response, the mechanism involved for the electron-hole pairs transport towards pollutant degradation, the photocatalysis process continuation in the absence of light, and the limitation of each of the discussed strategies is reviewed for future research. Lastly, the prospects of the TiO2 modification as a photocatalyst are also projected.