Hydrophilic TiO₂@MXene membrane for direct generation of monodisperse submicron water-in-diesel emulsion and its microexplosion performance

Hydrophilic membrane interfaces, especially that of particle-packed ceramic membranes, are generally not suitable for use as emulsification media for generating monodisperse water-in-oil emulsions. This is because their short adjacent pore distances tend to cause droplet coalescence. In this study, a facile in situ oxidation strategy was proposed to develop ceramic-based hydrophilic TiO₂@MXene membranes for directly generating monodisperse submicron water-in-diesel emulsions using membrane emulsification technology at room temperature. Through the in situ oxidation process, numerous TiO₂ nanoparticles were grown on the surface of MXene nanosheets to form a novel TiO₂@MXene composite structure with a membrane pore size of 12.2 nm. This structure is characterized by abundant transport channels, remarkably robust stability, and high water permeance of 154.8 L m⁻² h⁻¹ bar⁻¹. Because of the long horizontal distance between adjacent nanosheets and the substantially reduced transport resistance, water droplets can roll smoothly along the TiO₂@MXene nanochannels and then converge with the diesel, thus reducing the risk of emulsion coalescence. The mean droplet size of the emulsions can be controlled from ∼100 to 500 nm by regulating the emulsification conditions. The optimal emulsions exhibited excellent monodispersity with an average droplet size of 157.2 nm and possessed relatively excellent long-term stability (up to 45 days). Moreover, the emulsions showed a positive microexplosion phenomenon during heating. The maximum microexplosion strength of the emulsions reached 6.31 m s⁻¹ (at 20% water content), which provides a reliable theoretical basis for research on emulsified diesel as an alternative to traditional fuels.