Synthesis of ultrathin, nano-sized Ti3C2Tx with abundant =O and –OH terminals and high transparency as a cocatalyst: Enabling design of high-performance Titania-Ti3C2Tx hybrid photocatalysts

Conventional Ti3C2Tx used in photocatalysis usually has properties that are detrimental to the process such as thick layers, a micro-sized structure with low transparency, and a high concentration of fluorine terminals. Herein, we demonstrate the synthesis of ultrathin, nano-sized Ti3C2Tx with abundant oxygen-containing groups (=O and –OH) and high transparency (designated as N–Ti3C2Tx) as an alternative cocatalyst in liquid and gas phase photocatalysis. N–Ti3C2Tx is prepared by a two-step process that involves etching Al from Ti3AlC2 via fluorine treatment followed by simultaneous exfoliation and fluorine reduction. N–Ti3C2Tx is then coupled with TiO2 via hydration and dehydration approaches to form a photocatalyst (TiO2–N–Ti3C2Tx) with distinct morphology and surface chemistry. The small size of N–Ti3C2Tx facilitates a strong interfacial contact with TiO2, thereby enhancing electron transport between TiO2 and N–Ti3C2Tx, and electron-hole separation; and (2) the high transparency of N–Ti3C2Tx facilitates photon-TiO2 interactions. As a consequence, the photocatalytic activity of TiO2–N–Ti3C2Tx is superior to that of pristine TiO2, TiO2 coupled with thin, micro-sized Ti3C2Tx that is characterized by low transparency and fluorine terminals, and the widely used Ti3C2Tx-based photocatalyst synthesized by thermal nucleation of TiO2 on Ti3C2Tx. The high photocatalytic activity of TiO2–N–Ti3C2Tx is also attributed to the presence of abundant = O and –OH terminals on N–Ti3C2Tx that boosts pollutant adsorption. The study provides a rational approach for coupling TiO2 and Ti3C2Tx to promote beneficial charge transfer properties and synergistic effects that have far-reaching applications in photocatalysis.