Co-doped ZnO/Ti3C2 MXene hybrids with synergistic interfacial engineering for superior tetracycline photodegradation: experiment and theory

Antibiotic pollution poses a significant public health threat by promoting antibiotic resistance and reducing the effectiveness of existing medications, highlighting the urgent need for advanced water treatment technologies. In this study, a Ti3C2 MXene-supported cobalt-doped zinc oxide (Co–ZnO/MX) hybrid photocatalyst was synthesized via a hydrothermal method that enabled simultaneous metal-ion doping, heterojunction formation, and band-gap modulation. The synthesized catalysts exhibited effective photocatalytic degradation of tetracycline in aqueous solution. Among them, Co–ZnO/MX-12% demonstrated the highest performance, achieving a degradation efficiency of 93.7%, compared with 81.2% for ZnO and 84.3% for Co–ZnO under identical conditions. The effects of adsorption time, catalyst dosage, and initial pH were systematically investigated to optimize the degradation process. Reactive species trapping experiments and electron spin resonance (ESR) analysis confirmed that superoxide (•O2⁻) and hydroxyl (•OH) radicals were the dominant active species responsible for tetracycline degradation. Density functional theory calculations were performed to analyze the work function, electronic density of states, band structure, and charge distribution of ZnO and Co–ZnO, elucidating the role of cobalt incorporation in modulating electronic properties. These findings provide insights into designing efficient MXene-based photocatalysts for wastewater remediation.