Construction of TiO2/BiOCl S-Scheme heterojunction and photocatalytic degradation of norfloxacin

[Display omitted] •The charge transfer behavior in TiO2/BiOCl heterostructures in the presence of an internal electric field is discussed;•Defective energy levels of oxygen vacancies were constructed and used as electron traps to accelerate the separation and utilization of photogenerated carriers;•The proposed S-Scheme mechanism for enhancing the photocatalytic activity of TiO2/BiOCl composites;•The synergistic interaction between the S-Scheme heterojunction and oxygen vacancies is proposed to enhance the light absorption capacity and improve the photocatalytic degradation efficiency. TiO2/BiOCl heterojunction photocatalysts with different Ti/Bi weight ratios were synthesized by hydrothermal method and used for the photodegradation of norfloxacin (NOF). The as-prepared photocatalysts were characterized. The influences of temperature, catalyst dosage, initial NOF concentration and pH on the photodegradation performance were examined. Based on the results of HPLC-MS, intermediates and possible degradation pathways for NOF degradation were proposed. Based on TOC and 3D EEMs analysis, the mineralization ability of TiO2/BiOCl composites on NOF molecules was investigated. Finally, the possible mechanism for the enhancement of photocatalytic activity of TiO2/BiOCl photocatalyst was presented based on the density functional theory (DFT) calculations, experimental results of radical trapping and analysis of the charge transfer scheme under the internal electric field (IEF) formed in the heterostructure.