Preparation and regulation of two-dimensional Ti3C2Tx MXene for enhanced adsorption–photocatalytic degradation of organic dyes in wastewater

Ti3C2 MXenes were constructed via different strategies using HF-forming etchants or HF as etchants and were subsequently modified through alkalization to replace –F with O-containing terminal functional groups. Various analytical techniques were used to fully characterize all fabricated materials for confirming the formation of species with the desired morphologies and properties. ML-Ti3C2, etched with HF, presented a multilayered structure that made it resemble an accordion, while DL-Ti3C2, prepared using HF-forming etchants, was not completely etched, with some amounts of the parent compound's Al remaining in unformed vague laminated structures. ML-Ti3C2 alkalization yielded ML-Ti3C2(OH)2, which was characterized by large amounts of O-containing functional groups and greatly enhanced porosity compared with that of ML-Ti3C2. Methylene blue (MB) adsorption and photocatalytic degradation tests were then conducted to evaluate the functionalities of ML-Ti3C2(OH)2 by putting it into direct application instead of being used as catalyst promoters. ML-Ti3C2(OH)2 achieved adsorption–desorption equilibrium using MB in the dark within 30 min and 81.2% of MB was then selectively degraded over 120 min under simulated visible light irradiation. A possible degradation mechanism was proposed on the basis of the results of radical quenching experiments. This study offers a unique mechanism for directly applying MXene to the adsorption–photocatalytic degradation of organics in wastewater.