2D/3D g-C₃N₄ Nanosheet/CeO₂ Shuttle Heterostructure with Type-II Band Alignment for Visible-Light-Driven Pollutant Degradation

Abstract

Persistent chlorophenolic pollutants require efficient and reusable photocatalysts for sustainable wastewater remediation. We hypothesized that coupling two-dimensional graphitic carbon nitride (g-C₃N₄) nanosheets with three-dimensional shuttle-like cerium dioxide (CeO₂) would create an extended heterointerface that promotes photogenerated charge separation and enhances visible-light photocatalytic activity. To test this hypothesis, morphology-engineered g-C₃N₄/CeO₂ heterojunctions were constructed through hydrothermal and wet-chemical methods. Microscopic observations and elemental mapping confirmed intimate interfacial contact and homogeneous dispersion of g-C₃N₄ nanosheets over the CeO₂ shuttles. X-ray photoelectron spectra revealed a shift of the O 1 s signal toward lower binding energy, indicating interfacial electron transfer and increased electron density around the oxygen atoms of CeO₂. Photoluminescence, photocurrent, and electrochemical impedance measurements further demonstrated suppressed electron–hole recombination, accelerated interfacial charge transport, and reduced charge-transfer resistance. Consequently, the optimized composite, prepared with 15% g-C₃N₄ relative to CeO₂ by mass, achieved 96.6% degradation of 2,4-dichlorophenol within 3 h under visible-light irradiation, compared with only 30% degradation using pristine CeO₂. The combined surface, optical, photoelectrochemical, and radical-trapping results supported a proposed Type-II charge-transfer pathway, in which CeO₂ acts as an electron acceptor and superoxide radicals (•O₂⁻) serve as the predominant reactive species. The optimized photocatalyst maintained nearly unchanged activity over four consecutive cycles. The novelty of this work lies in constructing a morphology-controlled two-dimensional/three-dimensional nanosheet–shuttle interface that provides extensive interfacial contact, efficient charge migration, high photocatalytic performance and reproducible cycling behaviour under constant catalyst-loading conditions.