Vacancy-Mediated Oxygen Doping and Atomic-Level Interface Engineering Modulate Electron Transport Dynamics in Carbon Nitride: Multiscale Simulations and Experimental Synergy Unraveling Charge Transfer Mechanisms

In this study, graphitic-phase carbon nitride (O-Nv-CN) photocatalysts with synergistically engineered nitrogen vacancies and oxygen doping were synthesized via hydrothermal reduction followed by high-temperature calcination. The incorporation of nitrogen vacancies modulated the electronic structure and promoted the separation of photogenerated charge carriers, while oxygen doping optimized the band alignment and extended the visible-light absorption range. These modifications jointly contributed to significantly enhanced photocatalytic performance. Material characterization revealed that O-Nv-CN exhibited thinner nanosheets and a more developed porous architecture compared to pristine g-C 3 N 4 , resulting in a higher specific surface area and an increased density of active sites, thereby improving pollutant adsorption and catalytic reactivity. Photocatalytic experiments demonstrated that O-Nv-CN achieved 2.4-fold and 4.5-fold improvements in the degradation efficiency and reaction rate of tetracycline hydrochloride (TC-HCl), respectively, relative to g-C 3 N 4 . Reactive species trapping experiments and electron spin resonance (ESR) analyses confirmed that •O 2 ⁻ and •OH were the dominant reactive species. Density functional theory (DFT) calculations further revealed that nitrogen vacancies and oxygen dopants synergistically restructured the electronic band configuration, thereby enhancing the adsorption and activation of O 2 and TC-HCl molecules. The material optimization strategy proposed in this study provides both a theoretical basis and experimental support for the removal of antibiotic contaminants in complex aqueous environments.