Squaraine dye/Ti₃C₂T_x MXene organic-inorganic hybrids for photocatalytic hydrogen evolution

MXenes, a new family of 2D nanostructured materials, have been widely studied in the field of artificial photosynthesis due to their outstanding physicochemical properties. In this work, a series of 2,4-bis[4-(N,N-dibutylamino)phenyl] squaraine (SQ) derivatives with different number of hydroxyl groups were hybridized with Ti₃C₂T_x MXene nanosheets, and the organic-inorganic hybrid photocatalysts were applied for water-splitting hydrogen evolution. The mass ratios of SQ@Ti₃C₂T_x were optimized to 4 wt% for each SQ, and the best hydrogen evolution reaction (HER) rate of 28.6 μmol h^-1 g^-1 was achieved by SQ-3 with four OH groups. The photocatalytic ability of the hybrid comes from the outstanding light harvesting of SQ dye, sufficient active sites of Ti₃C₂T_x, and efficient separation and transfer of the photogenerated charges via heterojunction between SQ aggregates and Ti₃C₂T_x. This work firstly demonstrates an example of SQ sensitizer combined with MXene for hydrogen generation, which provides a new insight to further explore the MXene-based hybrid nanomaterials for water splitting hydrogen evolution.