Titanium dioxide (TiO
2) nanoparticles (NPs) are useful as a potential photocatalyst for the degradation of dyes such as methyl orange, rhodamine B, and methylene blue (MB). Understanding the mechanism of photocatalysis and the factors influencing photocatalysis is important for engineering TiO
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Titanium dioxide (TiO
2) nanoparticles (NPs) are useful as a potential photocatalyst for the degradation of dyes such as methyl orange, rhodamine B, and methylene blue (MB). Understanding the mechanism of photocatalysis and the factors influencing photocatalysis is important for engineering TiO
2 NPs to achieve an unprecedented photocatalysis rate. For TiO
2 NPs, their unique physicochemical qualities, such as small size, large surface area, optimum semiconductor bandgap, substantial oxidative potential, and outstanding chemical stability are factors which influence the MB degradation rate. The electron–hole pair separation in TiO
2 NPs allows for photocatalysis, which is not possible in their bulk form. The formation of reactive oxygen species (ROS) via photoinduced generation of electron–hole pairs under light irradiation is the starting point of the mechanism of photocatalysis for TiO
2 NPs. By generating ROS, TiO
2 NPs catalyze the degradation of MB. The photocatalytic performance of TiO
2 NPs is also different for different crystal phases, such as anatase, rutile, and brookite. The addition of metal or non-metal dopants into TiO
2 NPs enhances photocatalysis by enhancing light absorption, which enhances the generation of electron–hole pairs and of ROS. This review article will explain the mechanism of photocatalysis, the parameters influencing photocatalytic activity, active sites and recombination rates, disadvantages, and strategies to overcome these challenges that can improve TiO
2 NPs for a future wastewater treatment that is both efficient and sustainable.
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