2D/2D Ti3C2 MXene/HTiNbO5 nanosheets Schottky heterojunction for boosting photothermal-assisted solar-driven photodegradation of tetracycline hydrochloride

Developing high-efficiency photocatalysts for tetracycline hydrochloride (TCH) degradation is of great significance to ecosystems and human beings. In this work, a two-step process of exfoliation and re-stacking was performed to prepare re-stacked HTiNbO5 nanosheets (R-HTNS) and then coupled with Ti3C2 MXene to construct Ti3C2 MXene/R-HTNS (MX/RTS) with a 2D/2D Schottky heterojunction. These 2D/2D heterostructures between Ti3C2 MXene and R-HTNS can produce an internal electric field and provide maximum interface area for efficient charge transfer across the intimate interface. The photocatalytic performance of samples was evaluated by TCH degradation under simulated sunlight. The MX/RTS composites, with an optimal sample of 3-MX/RTS, show enhanced photocatalytic activity for TCH degradation compared with R-HTNS. The characterization results reveal that the introduction of Ti3C2 MXene can significantly increase specific surface area for providing more reactive sites and broaden the light absorption region. Besides, the incident light energy is absorbed by the Ti3C2 MXene component in MX/RTS composites to generate photothermal energy (heat), which facilitates the charge carrier separation and surface reaction kinetics. Thus, the enhanced TCH photodegradation activity for MX/RTS composites is due to the introduction of Ti3C2 MXene, which possesses the synergistic effect of the increased specific surface area, improved light-harvesting capacity, 2D/2D Schottky heterojunction, and photothermal energy effect. Additionally, the TCH photodegradation behavior is deliberated with a detailed discussion on various coexisting ions. During TCH photodegradation, the active radical species are determined for 3-MX/RTS. According to the characterization results, the possible TCH photodegradation pathway and mechanism over 3-MX/RTS are explored. This work may offer a novel insight for constructing MXene-based heterostructured photocatalysts with high efficiency.