Interfacial electronic perturbation and a proposed two-stage charge-transfer scenario in g-C3N4/rGO heterojunctions for photocatalysis

Abstract

A series of g-C₃N₄/reduced graphene oxide (CN/rGO) composites were synthesized via a facile ultrasonic-assisted approach to address the intrinsically high electron–hole recombination in g-C₃N₄. While most previous studies on CN/rGO systems have mainly emphasized the electron-sink role of rGO, the possible interfacial electronic redistribution occurring prior to illumination remains insufficiently clarified. In this work, a set of CN/rGO composites were systematically prepared and investigated using XRD, Raman, FTIR, XPS, UV–vis spectroscopy, PL, and photocatalytic decolorization tests to examine this hypothesis. The results reveal composition-dependent structural and local bonding perturbations in the composites, together with XPS binding-energy shifts consistent with an electronically perturbed interfacial environment within the g-C₃N₄ framework. Upon excitation, pronounced PL quenching indicates suppressed radiative recombination and is consistent with additional interfacial charge-transfer pathways involving rGO. Among the samples studied, CN/rGO-40/1 exhibits the best balance between interfacial interaction and structural integrity, achieving nearly complete RhB removal within 60 mins under natural sunlight and the highest mean apparent rate constant among the investigated compositions. Collectively, these observations are consistent with a proposed two-stage interfacial scenario in which heterojunction formation is associated with ground-state structural/electronic perturbations, followed by modified charge-transfer and recombination behavior under illumination.