Direct Z-scheme CeO2/TiO2 heterojunction derived from tobacco leaf vein biotemplate for visible-light photocatalytic degradation of tetracycline hydrochloride

Abstract

The development of visible-light-responsive biotemplated TiO2-based photocatalysts has been receiving much attention due to the pressing issue of antibiotic-residues in wastewater. In this work, tobacco leaf veins were utilized as a biotemplate to fabricate Z-scheme CeO2/TiO2 (GTS-CeO2/TiO2) photocatalysts via a solvothermal process followed by in situ calcination. Moreover, the microstructure units of the biotemplate-shaped photocatalysts can be regulated as required. Characterization and photocatalytic test results indicate that the biotemplated CeO2/TiO2 composites feature tight heterojunctions, which can effectively accelerate the separation and migration of photogenerated carriers for the degradation of tetracycline hydrochloride. The photodegradation efficiency of 20 ppm tetracycline hydrochloride under visible-light irradiation reaches 98.9 % over the GTS-CeO2/TiO2 in 120 min, with an apparent rate constant (Kappt) that is 2.9 times higher than that of CeO2/TiO2 synthesized without biotemplating. The enhanced photocatalytic performance is attributed to the construction of Z-scheme CeO2/TiO2 heterojunction, the presence of Ce4+/Ce3+, the unique morphology derived from the biotemplate, and the designed microstructure unit of the photocatalyst. The GTS-CeO2/TiO2 exhibits good stability and can be reused several times. The degradation pathways of TCH were primarily dominated by h+, ⋅OH, and ⋅O2-, leading to a reduction in the toxicity of intermediates. The degradation mechanism of tetracycline hydrochloride was also analyzed and proposed. This work provides a new inspiration for the preparation of visible-light photocatalysts to purify the environment in a more sustainable and environmentally friendly manner.