Direct synthesis of hydrogen fluoride-free multilayered Ti₃C₂/TiO₂ composite and its applications in photocatalysis

Ti3C2/TiO2 hybrids are environment-friendly and exhibit excellent photocatalytic and hydrogen -generating power characteristics. Herein, a novel single-step method is proposed for fabricating multilayer structures in which TiO2, generated from (NH4)2TiF6, wraps the Ti3C2 MXene by etching Ti3AlC2 with (NH4)2TiF6. The optimal reaction conditions for the etching of Ti3AlC2 with (NH4)2TiF6 were systematically studied. The phase composition, morphology, and photophysical properties of the Ti3C2/TiO2 hybrids were investigated using X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron mi-croscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and UV-vis spectrophotom-etry. The thermal stability of the hybrids was investigated using thermogravimetric and differential thermal analyses. Along with the formation of Ti3C2 MXene, Ti3AlC2 reacted with (NH4)2TiF6 at 60 degrees C for 24 h to form hybrids surrounded by NH4TiOF3 crystals. Subsequent re-actions of these hybrids with H3BO3 resulted in the conversion of NH4TiOF3 crystals into TiO2 and eventually into Ti3C2/TiO2 hybrids. Furthermore, the photocatalytic activity of the Ti3C2/TiO2 hybrids was measured by monitoring the photodegradation of methylene blue under ultraviolet light, which showed that the photocatalytic activity of the Ti3C2/TiO2 hybrids was higher than that of the commercial anatase TiO2 nanoparticles.