Schottky junction-mediated carrier separation in BiOBr/Ti3C2Tx van der Waals heterojunction photocatalyst for increased removal of Cr(VI) under visible-light

Abstract

The photocatalytic removal of pollutants can integrate efficient solar energy utilization with wastewater treatment. Herein, we report a simple strategy to construct BiOBr/Ti3C2Tx composite photocatalysts consisting of self-assembled van der Waals (vdw) heterojunction structures containing Schottky junctions. The vdW interaction between BiOBr and Ti3C2Tx and the structural stability of the catalysts were validated by density functional theory (DFT) calculations and an ab initio molecular dynamic simulation (AIMD). Compared to BiOBr, the BiOBr/Ti3C2Tx composites exhibited an enhanced light absorption capability and photocurrent response, along with a lower carrier recombination rate and charge-transfer resistance. The BiOBr/Ti3C2Tx activity for the photoreduction of hexavalent chromium (Cr(VI)) under visible-light irradiation considerably surpassed that of the original BiOBr (53.9 %). Using the BTC-0.8 catalyst (with a Ti3C2Tx: BiOBr mass ratio of 0.8 %) optimal reduction efficiency (94.0 %) for Cr(VI) with a reaction rate approximately 3.5 times that of pure BiOBr. The BTC-0.8 catalyst was viable over a wide pH range and maintained an 83.9 % photoreduction rate after four cycling experiments. The exceptional photocatalytic ability of BiOBr/Ti3C2Tx was achieved because Ti3C2Tx served as an electron injection layer that separated photogenerated carriers. The Schottky junction constructed within the BiOBr/Ti3C2Tx vdW heterojunctions suppressed electron backflow, promoting carrier separation. The excellent photocatalytic performance and strong cyclic stability of BiOBr/Ti3C2Tx demonstrated the considerable application potential of this photocatalyst.