Photo-self-Fenton system driven by ultrasmall Fe nanoparticles induced internal electric field toward efficient wastewater purification.

In photocatalytic water treatment processes, the production of hydrogen peroxide (HO) is often accompanied, which is difficult to extract from wastewater or increases costs. Additionally, adding iron ions to the wastewater to trigger the Fenton reaction further increases treatment costs and subsequent treatment difficulties. Herein, a photo-self-Fenton system, which does not require the addition of HO or iron ions, has been developed for efficient water treatment. Ultrasmall Fe nanoparticles (Fe NPs) are anchored onto a graphitic carbon nitride (g-CN) substrate to form a photo-self-Fenton catalyst (Fe-CN). The incorporation of Fe NPs introduces a doping level into the bandgap, significantly improving the catalyst's light absorption properties and carrier separation efficiency. Furthermore, the density functional theory (DFT) calculations and Kelvin probe force microscopy (KPFM) demonstrate that Fe NPs polarize the charge distribution on catalyst surface, which becomes a crucial driving force for the separation and transfer of photogenerated carriers. The optimized band structure and internal electric field jointly trigger the photo-self-Fenton reaction of dissolved O in water. The cooperative effect of hydroxyl radicals (•OH) and holes (h) achieved the rapid and efficient degradation and mineralization of emerging pollutants in water, and the Fe-CN system demonstrates exceptional resistance to interference and long-term stability in complex water conditions. This study provides a comprehensive understanding and framework for designing efficient photo-self-Fenton systems for environmental remediation.