Insight into the mechanism of Bi modified MXene-derived TiO2 for efficient visible-light driven photocatalytic reduction of bromate

The photocatalytic reduction of bromate (BrO 3 - ) in drinking water shows great promise. However, current photocatalysts mainly depend on UV light for effective bromate transformation. In this study, we introduced a novel visible-light-active catalyst, TBR (a combination of Ti 3 C 2 MXene, Bi, and TiO 2 ), synthesized through a straightforward hydrothermal method. Batch experiments were carried out in the laboratory to evaluate the photocatalytic removal effect of bromate by TBR under visible light. TBR completely eliminated 200   µg/L of bromate within 60   minutes (first-order kinetic constant: 0.0509   min -1 ). By employing photoelectric properties, density functional theory (DFT) and scavenger experiments, an intrinsic mechanism of the photocatalytic breakdown of bromate over the TBR/visible-light system was elucidated. The introduction of Bi induces the surface plasmon resonance (SPR) effect, and reduced the effective mass of electrons, resulting in a narrower band gap (from 2.88   eV to 2.50   eV) of the photocatalyst, and enables it to respond to visible light. Additionally, Ti 3 C 2 acted as an "electron sink," facilitating carrier migration and accumulation on its surface, creating a Schottky barrier that promoted efficient electron transfer and the separation of electron-hole pairs. Generation of ·O 2 - and ·OH radicals fostered mutual conversion of Br - and ·Br, playing a vital role in bromate removal. Moreover, TBR showed excellent stability. This research expands the potential of non-precious-metal photocatalytic co-catalysts for water treatment.