MXene-Derived Oxide Nanoheterostructures for Photocatalytic Sulfamethoxazole Degradation

Herein, we report for the first time the use of ternary oxide nanoheterostructure photocatalysts derived from (Nb _y , Ti_1-y )₂CT _x MXene in the treatment of water. Three different compositions of binary MXenes, viz., (Ti_0.75Nb_0.25)₂CT _x , (Ti_0.5Nb_0.5)₂CT _x , and (Ti_0.25Nb_0.75)₂CT _x (with T _x = OH, F, and Cl), were used as single-source precursor to produce TiNbO _x -3:1, TiNbO _x -1:1, and TiNbO _x -1:3 by controlled-atmosphere thermal oxidation. Phase identification and Le Bail refinements confirmed the presence of a mixture of rutile TiO₂ and monoclinic Ti₂Nb₁₀O₂₉. Morphological investigations through scanning and transmission electron microscopies revealed the retention of layered nanostructures from the MXene precursors and the fusion of TiO₂ and Ti₂Nb₁₀O₂₉ nanoparticles in forming nanosheets. Among the three oxide nanoheterostructures, TiNbO _x -3:1 exhibited the best photocatalytic performance by the removal of 83% of sulfamethoxazole (SMX) after 2 h of reaction. Such a result is explained by a complex influence of structural, morphological, and electronic properties since TiNbO _x -3:1 consisted of small-sized crystallites (40-70 nm) and possessed a higher surface area. The suggested electronic band structure is a type-II heterojunction, where the recombination of electrons and holes is minimized during photocatalytic reactions. The photocatalytic degradation of SMX was promoted by the attack of ^•OH, as evidenced by the detection of 2.2 μM ^•OH, using coumarin as a probe. This study highlights the potential application of MXene-derived oxide nanoheterostructures in wastewater treatment.