Regulation of the Electronic Structure and Charge Behaviors Derived from Single-Atom Iron for Photocatalytic Water Purification

Large-scale and sustainable photocatalytic water treatment requires semiconductors with appropriate band structures and efficient charge transfer properties. Motivated by this point, a facial method is reported for synthesizing an efficient single-atom photocatalyst (FeSA-PCN) consisting of polymeric graphitic carbon nitride (g-C3N4) rationally integrated with Fe single atoms (Fe SAs). Fe SAs not only enhance the oxidation ability of the holes on the valence band but also introduce a doping energy level directly into the band gap, significantly expanding the light absorption range of FeSA-PCN. The density functional theory (DFT) calculations and characterization results such as Kelvin probe force microscopy (KPFM) imply that a significant polarized distribution of surface charges is constructed owing to the electronic interaction between Fe SAs and g-C3N4. This enables the efficient separation and transfer of photogenerated charge carriers for surface reactions. Subsequently, high-oxidation-capability holes directly oxidize adsorbed pollutants, while electrons are captured by oxygen, reduced via a two-electron process to H2O2, and further activated into •OH for pollutant degradation. Consequently, FeSA-PCN demonstrates outstanding efficiency in pollutant degradation, resistance to interference, and stability, which proposes a promising strategy for developing g–C3N4–based photocatalysts for applications in environmental remediation.