Photogenerated electron transfer in Ni/NiO supported on g-C3N4 enables sustainable catalytic activation of peroxymonosulfate for emerging pollutant removal

Abstract

Emerging pollutants such as enrofloxacin (ENR), a widely used fluoroquinolone antibiotic, pose significant threats to aquatic ecosystems due to their persistence, bioaccumulation, and toxicity. This study reports the development of a stable and efficient Ni-NiO/g-C₃N₄ heterojunction photocatalyst for ENR degradation under visible light and in the presence of peroxymonosulfate (PMS). The catalyst, synthesized via a templated self-assembly and hydrothermal method, achieved 98.7 % ENR removal within 45 min. Mechanistic studies revealed that the charge transfer along lower energy bands in ternary heterojunctions enhances charge separation and promotes the generation of reactive oxygen species (ROS), including sulfate radicals (SO₄^•–), hydroxyl radicals (•OH), and singlet oxygen (¹O₂). Density functional theory calculations confirmed strong PMS adsorption on the heterojunction of metallic Ni and exposed Ni in NiO, facilitating efficient ROS production and bond polarization for pollutant degradation. The catalyst exhibited remarkable structural stability, maintaining consistent performance over six reuse cycles, attributed to the robust g-C₃N₄ matrix and dynamic redox cycling of Ni/NiO. Toxicity assessments showed significant detoxification of ENR into less harmful byproducts, emphasizing the environmental safety of the process. This work demonstrates the potential of the Ni-NiO/g-C₃N₄/PMS system as a sustainable and scalable approach to address the challenges posed by emerging pollutants in aquatic environments. The research highlights the significance of integrating photocatalysis and PMS activation for advanced oxidation processes, offering an effective pathway to mitigate antibiotic pollution and its ecological impact and can contribute to the development of next-generation catalysts for environmental remediation.