The authors report a scheme for enhancing the photodegradation properties of TiO₂ nanoparticles (TiO₂ NPs) by controlling their structural phases through cations doping (cobalt and Sulfur). Cobalt-sulfur co-doped TiO₂ nanoparticles were synthesized via a hydrothermal process, with sulfur content varying at levels of 0.69, 1.37, and 2.06 atomic percent (at. %), while maintaining a constant cobalt content of 0.2 at. %. Our finding shows that the methyl blue dye loaded with pure TiO₂ degraded marginally in 120 min (⁓ 10.5%) while in the presence of an optimally doped sample (Co: 0.2 at. %, S 2.06 at. %), it degraded almost 93% for the same duration. The study explores the underlying physical mechanisms that contribute to the varying levels of photoactivity, and these mechanisms are found to be influenced by the valency of the doping agents. The findings of this study demonstrate that precise control over the formation of the anatase phase through doping enables the production of a remarkably efficient TiO₂-based photocatalyst. Our results indicate great prospects in enhancing TiO₂-based photocatalyst development chemically, a suitable approach for large-scale nanoparticle production for industrial applications.