Enhancing O₂ adsorption and activation over porous S-doped g-C₃N₄ rod toward efficient photocatalytic rhodamine-B degradation

Photocatalytic oxygen molecular (O₂) activation to generate reactive oxygen species (ROS) is a promising strategy for the oxidative degradation of organic pollutants. Herein, a porous S-doped g-C₃N₄ rod (S-g-CN-rod) was synthesized and applied to photocatalytic superoxide radicals (·O₂^-) evolution and rhodamine-B (RhB) degradation. The morphological, structural, and optical properties of all samples were investigated. DFT calculation demonstrated that the carbon site adjacent to S was energetically favorable for O₂ adsorption, which was conducive to ·O₂^- evolution. The porous S-g-CN-rod exhibited an excellent photocatalytic ·O₂^- evolution rate of 268.2 μmol L⁻¹ h⁻¹, which was the main active species to degrade RhB. Conceivably, the porous S-g-CN-rod demonstrated exceptionally high efficiency of photocatalytic RhB degradation and achieved almost complete disposal of RhB (99.7 %) in only 30 min, which was higher than most reported photocatalysts. The experimental results and theoretical calculations demonstrated that the preeminent photocatalytic activities were ascribed to enhanced light-harvesting, improved migration and separation of photo-induced electrons, and the superior O₂ adsorption and activation induced by S doping.