In situ fabrication of Bi2Se3/g-C3N4 S-scheme photocatalyst with improved photocatalytic activity

Bismuth selenide (Bi2Se3) is an attractive visible-light-responsive semiconductor that can absorb a full range of visible and near-infrared light. However, its poor redox capacity and rapid carrier recombination limit its application in photocatalytic oxidation. In this study, we adopted Bi2Se3 as the couple part of graphitic carbon nitride (g-C3N4) to construct a Bi2Se3/g-C3N4 composite photocatalyst. Through in situ fabrication, the self-developed Bi2O3/g-C3N4 precursor was transformed into a Bi2Se3/g-C3N4 heterojunction. The as-prepared Bi2Se3/g-C3N4 composite exhibited much higher visible-light-driven photocatalytic activity than pristine Bi2Se3 and g-C3N4 in the removal of phenol. The enhanced photocatalytic activity was ascribed to the S-scheme configuration of Bi2Se3/g-C3N4; this was confirmed by the energy-level shift, photoluminescence analysis, computational structure study, and reactive-radical testing. In the S-scheme heterojunction, photo-excited electrons in the conduction band of g-C3N4 migrate to the valence band of Bi2Se3 and combine with the excited holes therein. By consuming less reactive carriers, the S-scheme heterojunction can not only effectively promote charge separation, but also preserve more reactive photo-generated carriers. This property enhances the photocatalytic activity.