Photocatalytic performance and mechanism of oxygen-doped g-C3N4 and photoactivated peroxymonosulfate on rhodamine B

Organic pollutants such as dyes and pharmaceuticals pose serious threats to aquatic ecosystems and human health, highlighting the need for efficient advanced oxidation processes. Here, oxygen-doped graphitic carbon nitride was synthesized by co-calcination of melamine and cyanuric acid and applied to a photoactivated peroxymonosulfate system. Comprehensive characterizations combined with density functional theory calculations revealed that oxygen incorporation induces charge redistribution and improves the surface structure, leading to enhanced visible light absorption and charge separation. Under simulated sunlight, the catalyst achieved 99% degradation of rhodamine B (30 mg/L) within 6 min, with a reaction rate 14 times higher than that with pristine carbon nitride. Reactive species trapping and electron paramagnetic resonance analyses confirmed that singlet oxygen and superoxide radicals dominate the degradation process. The catalyst also exhibited good stability over five cycles. This work provides an effective strategy for designing metal-free photocatalysts for peroxymonosulfate activation and wastewater treatment.