Room-temperature MXene-derived Ti3+ and rich oxygen vacancies in carbon-doped amorphous TiOx nanosheets for enhanced photocatalytic activity

Exploring efficient photocatalysts for photocatalytic degradation is of considerable importance for the long-term mitigation of environmental stress. Although defect engineering is an effective strategy to alter the electronic transport properties and light absorption capacity of TiO2, the synthesis of TiO2 rich in oxygen vacancies (OVs) via a green process at room temperature and with low energy consumption remains a challenge. Herein, amorphous TiO2 nanosheets rich in OVs were prepared by H2O2-assisted room-temperature oxidation of Ti3C2Tx MXene via a bottom-up approach. Notably, small amounts of C and Ti3+ were introduced during the preparation of carbon-doped TiO2 (C-TiOx), which was shown to possess abundant surface functional groups (e.g., –OH, –O, and –F) and two intermediate levels in its bandgap. Comparative experiments demonstrated that OVs play a key role in suppressing the recombination of photogenerated carriers and expanding the light absorption range of the photocatalyst. The unique quasi-two-dimensional structure of C-TiOx features a large number of exposed active sites, which are beneficial for improving its catalytic performance. Tetracycline (TC) was removed from the aqueous solution by the prepared photocatalysts C-TiOx and annealed-TiO2, and the former adsorbed 41.1% of TC. The TC removal efficiency of C-TiOx was 76%, which was higher than that of annealed-TiO2. This approach embodies a new strategy for introducing defects and doping in TiO2. Moreover, it is also thought that C-TiOx possesses promising characteristics suitable for a wide range of potential future applications.