Facilitating Oriented Electron Transfer from Cu to MoC MXene for Weakened Mo─H Bond Toward Enhanced Photocatalytic H Generation.

MoC MXene (MoCT) is recognized as an excellent cocatalyst due to unique physicochemical properties and platinum-like d-band of Mo active sites. However, Mo sites of MoCT with high-density empty d-orbitals exhibit strong Mo─H bonds during photocatalytic hydrogen evolution, leading to easy adsorption of hydrogen ions from solution and unfavorable desorption of H from Mo sites. To weaken the Mo─H bond, a strategy of oriented electron transfer from Cu to MoCT to increase the antibonding orbital occupancy of Mo─H hybrid orbitals is implemented by introducing Cu into MoCT interlayers to form Cu-MoCT. The Cu-MoCT is synthesized from MoGaC and CuCl via a one-step molten salt method and combined with TiO to form Cu-MoCT/TiO photocatalyst through an ultrasound-assisted approach. Hydrogen production tests reveal that an exceptional performance of Cu-MoCT/TiO (6446 µmol h g, AQE = 18.3%) is 8.4 fold higher than that of MoCF/TiO (MoCF by the conventional etchant NHF+HCl). Density functional theory (DFT) calculations and characterization results corroborate that the oriented electron transfer from Cu to MoCT increases the Mo─H antibonding occupancy in Cu-MoCT, thereby weakening Mo─H bonds and accelerating the hydrogen evolution rate of TiO. This research offers valuable insights into optimizing H-adsorption capabilities at active sites on MXene materials.