Schottky barrier height mediated Ti3C2 MXene based heterostructure for rapid photocatalytic water disinfection: Antibacterial efficiency and reaction mechanism

Abstract

Schottky barrier plays a key role in determining the interface electron transfer of most Schottky junctions, but the relationship between schottky barrier height (SBH) and photocatalytic disinfection activity is not clearly revealed. Here, a well-designed tubular graphitic carbon nitride/hydroxyl terminated Ti3C2 MXene (TCN/TC(OH)) Schottky junction with controllable SBH was prepared as a model case for investigation. Experimental study and density functional theory calculation confirm that the surface hydroxyl termination of Ti3C2 can lower the SBH of TCN/TC(OH) by reducing its work function (0.23 eV). The lowered SBH ensures rapid interface transfer of photogenerated electron, which decreases the average surface recombination rate from 0.0077 s−1 (TCN/TC) to 0.0045 s−1 (TCN/TC(OH)-3) and increases the corresponding surface charge transfer efficiency from 48.2% to 53.2%. Rotating disk electrode measurement confirms that different from the two-step single-electron O2 reduction of TCN/TC (n = 1.54), TCN/TC(OH)-3 (n = 1.95) exhibits a one-step two-electron reduction route, which is more selective for the generation of the major antibacterial reactive oxygen species H2O2. Consequently, TCN/TC(OH)-3 presents much higher photocatalytic performance towards natural water disinfection, and can entirely inactivate 7 × 107 CFU/mL of Staphylococcus aureus even in complex water matrix (interfering ions, acidic solution and real water samples). Our work provides a feasible guidance for future natural water purification by interfacial engineering of the MXene-based Schottky junction.