Because of the ever-growing world population and the burgeoning of economic advancements, solving both environmental and energy-driven challenges are of prime concern. In the view of the current scenario, photocatalyst as an environmentally friendly method has rapidly emerged due to its prominent function in the conversion of solar energy for overcoming two aforementioned serious challenges. Recently, numerous attempts have been carried out for enhancing the visible-light photoactivity by application of TiO2 as photocatalyst because of its extensive scope of employment in both environmental-related and energy regions. Nevertheless, the photocatalytic performance of TiO2 under visible-light illumination is seriously restricted by the absorption edge in the ultra-violet range and the rapid electron–hole recombination. Extensive research has been dedicated to bypassing the shortcomings of titanium dioxide and hence improving its photoactivity under visible light. To be more specific, some approaches for modification of TiO2 properties include tetragonal BaTiO3 nanoparticles, ultrasound-assisted preparation of rGO/TiO2 nanocomposite, BaTiO3/ZnO heterostructured photocatalyst, Sol pH-induced ZnO-TiO2 multi-phase composite, BaTiO3/g-C3N4 heterojunction, TiO2-zeolite nanocomposite, etc., were explored and developed. Moreover, in this review paper, the authors briefly evaluated various nano-TiO2 synthesis methods, such as sol-gel, hydrothermal, solvothermal, and mixed ones. Despite the excellent achievements and the improvements in this area, the probability of nano-TiO2 modification for highly efficacious photocatalyst systems has not been completely explored and its commercialisation still is problematic. As a result, still, intensive research efforts require to effectively overcome those challenges for reaching a bright future in the wastewater treatment process with minimum environmental adverse effects.
