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.