Microwave-Assisted Hydrothermal Synthesis of Photocatalytic Truncated-Bipyramidal TiO₂/Ti₃CN Heterostructures Derived from Ti₃CN MXene

Abstract

TiO₂/MXene heterostructure has garnered significant interest as a photocatalyst due to its large surface area and efficient charge carrier separation at the interface. However, current synthesis methods produce TiO₂ without clear crystal faceting and often require complicated postprocessing step, limiting its practical applications. We demonstrate a facile and controlled microwave-assisted hydrothermal synthesis for transforming multilayered Ti₃CN MXene to a truncated-bipyramidal TiO₂/Ti₃CN heterostructure. The resulting TiO₂ nanocrystals at the Ti₃CN surface exhibited crystalline anatase truncated bipyramids, exposing {001} and {101} facets. We further tailored an indirect optical band gap of the TiO₂/Ti₃CN heterostructure in the range of 3.17-3.23 eV by varying the hydrothermal synthesis time from 15 min to 5 h at a fixed temperature of 160 °C. Efficient charge separation allowed us to decompose 97% of methylene blue (MB) within 30 min of ultraviolet (UV) light irradiation, ∼3.9-fold faster than the benchmark P25, higher than any other TiO₂/MXene heterostructures. With simulated white light, we achieved over 60% efficiency of the dye decomposition within 2 h of irradiation, which resulted in 1.5-fold faster kinetics than P25. We also observed a similar excellent performance of Ti₃CN-derived TiO₂ in decomposing various persistent synthetic dyes, including commercial textile dye, methyl orange, and rhodamine B. In conclusion, our study provides a strategy for utilizing MXene chemical reactivity to produce highly crystalline optically active TiO₂/Ti₃CN heterostructure. The developed heterostructure can serve as an efficient photocatalyst for the degradation of organic pollutants.