Enhanced photocatalytic degradation of perfluorooctanoic acid by Ti3C2 MXene-derived heterojunction photocatalyst: Application of intercalation strategy in DESs

Abstract In-situ construction of heterojunction photocatalyst on two-dimensional (2D) Ti3C2 MXene substrate has been proved to be a feasible method to enhance the photocatalytic degradation of organic pollutants. However, the limited interlayer spacing of 2D Ti3C2 hinders the in-situ growth of TiO2 photocatalyst. Herein, the intercalation strategy was developed in deep eutectic solvents (DESs) method to achieve interlayer expansion of Ti3C2 and improve Ti3C2-derived photocatalyst performance. Because of the intercalation of choline cations, the DESs method synthesized Ti3C2 (Ti3C2-DES) had the larger c-lattice parameter than that of traditional HF method synthesized Ti3C2 (Ti3C2-HF). The interlayer space of Ti3C2-DES could be intercalated with more water molecule for oxidization of the Ti atoms, which remarkably promoted the in-situ growth of TiO2 crystals. The formed heterojunction between (001) and (101) facets enhanced carriers separation. The Ti3C2 substrate with excellent conductivity further promoted carriers transfer. As a result, Ti3C2/TiO2 photocatalyst exhibited superior perfluorooctanoic acid (PFOA) removal performance (almost 100% removal efficiency and 49% defluorination efficiency within 16 h) compared with the traditional Ti3C2-HF/TiO2 (22% removal efficiency and 12% defluorination efficiency within 16 h). This study provides a feasible strategy for enhancing photocatalytic degradation of PFOA by Ti3C2 MXene-derived heterojunction photocatalyst.