MXene/TiO₂ Photocatalyst: The Key Role of MXene Electron Trapping in Water and Air Treatment

The photocatalytic activity of TiO₂ can be increased by incorporating it into a composite with an electron-trapping co-catalyst. MXene can perform this task as an electron-conducting material. In addition to trapping electrons, it also affects the defects in TiO₂ near the interface. To screen for the best photocatalytic performance, three types of composites were prepared: by physical mixing, chemical deposition, and ALD. During characterization, the structural, optical, and photoelectrochemical properties were determined. Photocatalytic activity was examined in suspension (phenol conversion) and on a layer (gas phase ethanol conversion). It was found that the composite containing the lowest proportion of cocatalyst (1 wt.%) had the highest photocatalytic activity. According to the results of photocatalytic activity measured in suspension, the physical mixtures were proven to be more effective than neat TiO₂, with the composites converting approximately the total amount of phenol in ~40 min, while TiO₂ required ~80-90 min to do so under the same conditions. Thus, the electron-trapping role of MXene is clearly demonstrated in suspension applications, which is also confirmed by other characterization methods (photoluminescence, photocurrent density). TiO₂ performed best during ethanol conversion, as it has the highest ethanol adsorption capacity (33.41%). During ethanol conversion tests, the MXene electron-trapping property was most effectively demonstrated in composites formed using the ALD method.