(158a) One-Step Fluorine-Free Synthesis of Delaminated, OH-Terminated Ti3C2: High Photocatalytic NOx Storage Selectivity Enabled By Coupling TiO2 and Ti3C2-OH

Difficulties associated with MXene fabrication typified by environmentally hazardous fluorine-based etching process followed by delamination and fluorine reduction steps create obstacles to its expansion and application in photocatalytic air purification. Herein, we demonstrate a one-step hydrothermal process that involves alkali (NaOH)-assisted aluminum etching in the presence of a delaminating agent (hydrazine) for the synthesis of delaminated, OH-terminated MXene (Ti₃C₂-OH). The process does not require fluorine-containing compounds and produces Ti₃C₂-OH sheets without post-synthesis treatment. Coupling Ti₃C₂-OH with TiO₂ shows a robust synergistic effect as a co-catalyst in the photocatalytic oxidation of NO_x. Excellent NO_x storage selectivity (91%) and a positive DeNO_x index (+ 0.30) were achieved at NO conversion of 54%. The photocatalytic activity of the hybrid shows high sensitivity to the surface chemistry of the co-catalyst as Ti₃C₂-OH outperforms delaminated, F-terminated Ti₃C₂ (fabricated via traditional process), which shows low NO_x storage selectivity (65%) and a negative DeNO_x index (-0.05) at NO conversion of 47%. These findings will benefit ongoing efforts to develop effective alternative methods for MXene synthesis and provide a pathway for the rational design of efficient NO_x abatement photocatalysts.