Boosting TiO ₂ photocatalysis under visible light, doping, surface modification, and nanostructure design

Abstract The factors that have intensified the aggressiveness of environmental pollution and the necessity to possess clean energy all across the globe have contributed to intensifying the desire to possess solar-powered photocatalytic technology. Due to its non-toxicity and low cost, titanium dioxide (TiO 2 ) is one of the most investigated photocatalysts, which is chemically stable. However, because of its high bandgap (about 3.2 eV), photoactivation can only occur in the ultraviolet light (only a small fraction of the solar spectrum), so this limits its use in natural sunlight. To counter this weakness, the current research has been directed to the extension of the optical response of TiO 2 into the visible spectrum. The current efforts to enhance the TiO 2 photocatalytic performance are introduced in this review: non-metal doping, surface engineering, heterojunction design, incorporation of plasmonic/light-scattering nanostructures, and nanostructure design. These modifications improve the absorption in the visible-light region, decrease charge-carrier recombination, and improve interfacial charge transfer. The advances of synthesis techniques, which enable the composition and morphology to be controlled with high precision, are also stated. The developed TiO 2 -based photocatalysts are better in the application of degradation of environmental pollutants, photocatalytic hydrogen generation, and CO 2 conversion under a specified experimental setup. Finally, the review indicates the prevailing conditions or the way forward for the rational design of efficient TiO 2 photocatalysts for sustainable environmental and energy-relevant applications.