Harmonious K–I–O co-modification of g-C3N4 for improved charge separation and photocatalysis

Abstract

Co-modification of graphitic carbon nitride (g-C₃N₄) photocatalysts can maximally optimize their intrinsic photoelectric structures, but usually involves complex multistep reactions, and thus is challenging because structural collapse and active site decay usually happen due to the complex process, over-treatment or conflict of different modification strategies. In this work, potassium iodate (KIO₃), an edible salt additive, was used as a critical waste-free modifier in the thermal polymerization of g-C₃N₄, leading to a fast and coordinated co-modification of g-C₃N₄ photocatalysts. The final g-CN-KIO₃ photocatalyst demonstrated a superior and balanced optical absorption ability and semiconductor band structure. In visible-light-driven photocatalytic model tests, g-CN-KIO₃ showed a 3.25 times higher Cr(VI) photoreduction rate and five orders of magnitude lower residual bacteria in a photocatalytic sterilization within 120 min compared with raw g-C₃N₄. The photocatalytic performance of g-CN-KIO₃ also outperformed all of the controls without maximized K–I–O co-modification (CN-K, CN-I, CN-O, and CN-KI). Photocurrent and electrochemical impedance experiments suggest that the co-modified photocatalysts have a faster charge separation ability, which is attributed to the multiple K–I–O co-modifications inducing an optimized surface electronic structure and slower carrier recombination. This work provides a new way to simplify and coordinate complex multi-factor regulation of materials.