Template-Free, Solid-State Synthesis of Hierarchically Macroporous S‑Doped TiO₂ Nano-Photocatalysts for Efficient Water Remediation

Nanosized sulfur-doped titanium dioxide emerged as an attractive photocatalyst in various environmental remediation applications, yet most synthesis methods require hazardous sulfurizing agents and intricate synthesis procedures. Herein, we present a facile, sustainable, and environmentally friendly preparation process for the production of visible-light-active meso–macroporous sulfur-doped anatase TiO₂ (S-TiO₂) nanoparticles for the first time. This strategy encompasses solventless mixing of titanium salt and surfeit yet nontoxic abundant elemental sulfur under continuous ball milling and moderate thermoannealing. The characterizations of as-obtained S-TiO₂ nanoparticles showed enhanced physicochemical properties including distinctive surface features composed of hierarchical hollow macroporous channels having nanostructured mesoporous core walls. The annealing temperature was observed to control the structure and extent of sulfur doping in TiO₂. Upon insertion of a sulfur atom into the TiO₂ lattice, the band gap energy of S-TiO₂ was significantly lowered, facilitating the enhanced photochemical activity. Owing to the effective S doping (1.7–2.8 atom %), and the interconnected hollow meso–macroporous nanostructure, the resulting nanosized S-TiO₂ exhibited unique adsorption properties and superior photocatalytic efficiency for the rapid degradation of hazardous organic dyes and phenols for water remediation. The presented strategy holds high potential to provide rapid production of a hierarchical and highly porous S-TiO₂ photocatalyst on a large scale for various environmental remediation and other myriad photochemical applications.