Difficulties associated with MXene fabrication, exemplified by the environmentally hazardous fluorine-based etching process followed by delamination and fluorine reduction steps, are impediments 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 the use of fluorine-containing compounds and produces Ti3C2-OH sheets without the need for post-synthesis treatment. Coupling Ti3C2-OH with TiO2 shows a strong synergistic effect as a co-catalyst in the photocatalytic oxidation of NOx. Excellent NOx storage selectivity (91%) and a positive DeNOx index (+ 0.30) were achieved at a NO conversion of 54%. The photocatalytic activity of the hybrid shows high sensitivity to the surface chemistry of the cocatalyst as Ti3C2-OH outperforms delaminated, F-terminated Ti3C2 (fabricated via traditional process), which shows low NOx storage selectivity (65%) and a negative DeNOx index (-0.05) at NO conversion of 47%. We envision that these findings will benefit ongoing efforts aimed at developing effective alternative methods for MXene synthesis and provide a pathway for the rational design of efficient NOx abatement photocatalysts.

Efficient and facile synthesis of delaminated, OH-terminated Ti3C2 as a cocatalyst in TiO2 photocatalysis

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