Electrostatic interaction mechanism of visible light absorption broadening in ion-doped graphitic carbon nitride

Broadening the light response of graphitic carbon nitride (CN) is helpful to improve its solar energy utilization efficiency in photocatalytic reaction. In this work, a facile synthesis method was developed via the treatment of potassium-doped CN (CN-K) with H₂O₂ in isopropanol solvent. Various characterizations indicate the basic structure of CN-K treated with H₂O₂ (CN-K-OOH) resembles that of CN-K, while it presents light absorption up to 650 nm. A series of control experiments and TGA-MS measurements suggest the weak electrostatic attraction between potassium ions and hydroperoxyl groups inside CN-K-OOH is responsible for its enhanced visible light absorption. As a consequence, compared to pristine CN, the photodegradation organic pollutant ability of CN-K-OOH is obviously improved under visible light irradiation (>470 nm). The current synthesis strategy might be universal and it could be applied to other cations.