Construction of hierarchical 2D/2D few-layered MoS2/S-doped g-C3N4 heterojunctions for enhanced photocatalytic formaldehyde removal.

Modification of graphitic carbon nitride (g-C3N4) with semiconductor nanomaterials has been widely investigated as an effective method to enhance its photocatalytic activity. However, the construction of efficient g-C3N4-based heterojunction photocatalysts via an environmentally benign method remains critical. Herein, a two-dimensional (2D) few-layered MoS2/S-doped g-C3N4 hierarchical heterojunction was successfully synthesized by a simple strategy via combining small molecule-assisted liquid exfoliation, calcination and hydrothermal strategy, which was subsequently utilized for photocatalytic formaldehyde removal. The evaluation of the photocatalytic degradation reaction showed that the as-prepared 2D/2D MoS2/S-doped g-C3N4 photocatalysts exhibited superior photocatalytic activity compared to pristine g-C3N4 and S-doped g-C3N4 alone, which was attributed to the intimate interface and rapid charge transfer pathways. This heterojunction structure suppresses the excited electron-hole pair recombination within g-C3N4, which optimally enhances the photodegradation activity owing to high electron-hole pair separation efficiency. The few-layer MoS2 nanosheets play an irreplaceable role due to their unique molybdenum-sulfur atomic arrangement, thereby displaying the superior electronic properties of few-layer or even monolayer nanosheets, which make them an important transfer medium for photoexcited electrons. Meanwhile, S doping effectively modulates the band gap of g-C3N4 and introduces sufficient structural defects to inhibit electron-hole recombination. Moreover, the synthesis employs efficient and non-hazardous reagents, and the resulting catalysts exhibit outstanding stability and recyclability for pollutant degradation.