Construction of hierarchical 2D/2D few-layered MoS ₂ /S-doped g-C ₃ N ₄ 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 <i>via</i> 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 <i>via</i> 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.