Advances in the strategies for enhancing the photocatalytic activity of TiO2: Conversion from UV-light active to visible-light active photocatalyst

Advanced oxidation process, a green method in contribution to betterment in environment has been emerged to a larger scale in past decades. Conventional wastewater strategies possess release of detrimental by-products. Hence, photocatalysis has been taken into account as an advanced oxidation, eco-friendly, cost effective, and non-detrimental strategy for wastewater treatment and enironmental remediation. It is now-a-days taken under consideration to utilize most of the solar energy for clean energy production in form of hydrogen gas as well as environmental remediation. Conventionally efficient photocatalyst, viz. TiO2 reported in literature is UV-active due to its larger band gap. However, solar light spectra consist of only approx. 5% UV and 45% visible light radiations. Therefore, the aim of this literature study is to enhance the activity of photocatalysts, employing distinct modifications strategies to decrease band gap and making the photocatalyst efficient to absorb visible light range. This review summons up photocatalytic mechanism, as well as several modulation techniques viz. variation in semiconducting material by metal/non-metal doping, sensitizer doping, heterojunction formation and semiconductor coupling, oxygen vacancies formation, cocatalyst loading, and effect of defect formation, for conversion of UV light active photocatalysts to visible light active as well as increment in visible light absorption. Modified titanium dioxide in visible spectrum had shown a highly advantageous applications including degradation of pollutants for waste-water treatment, hydrogen production, CO2 reduction and antibacterial activity; and established in this review.