TiO₂-Decorated MXenes for Efficient UV Light Photocatalysis: A Comparative Study of Few- and Multi-Layer Structures

Water contaminated by textile dyes is a tremendous risk to human health and the environment due to its toxic and carcinogenic nature, thus requiring advanced and efficient removal strategies. Therefore, this study aimed to investigate the photo-oxidation performance of few- and multi-layer Ti₃C₂T_x nanosheets (MXenes) decorated with TiO₂ nanoparticles for methyl orange removal from synthetic solutions. The quantification of photogenerated hydroxyl radicals by fluorescence revealed much higher OH^• production for TiO₂-decorated samples, especially for multi-layer MXene, in which it was 2.8 times higher than that of few-layer MXene. However, photocatalysis was morphology-controlled: despite lower OH^•, the few-layer MXene achieved the highest dye conversion (~45% after 5 h), attributed to shorter charge migration distances and more accessible TiO₂ active sites, enabling effective h⁺ and superoxide-driven pathways. Moreover, the detected -OH surface terminations verified on MXenes promoted a notable adsorption capacity, especially for the multi-layer samples (~31%) via interlayer trapping and H-bonding. Therefore, our results demonstrate that few-layer MXenes are promising candidates for the efficient removal of methyl orange and highlight the potential of TiO₂-decorated MXenes as promising photocatalysts for environmental remediation.