Template-Free, Solid-State Synthesis of Hierarchically Macroporous S-Doped TiO ₂ Nano-Photocatalysts for Efficient Water Remediation

Abstract

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 TiO ₂ (S-TiO ₂) 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-TiO ₂ 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 TiO ₂. Upon insertion of a sulfur atom into the TiO ₂ lattice, the band gap energy of S-TiO ₂ 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-TiO ₂ 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-TiO ₂ photocatalyst on a large scale for various environmental remediation and other myriad photochemical applications.