Molybdenum diselenide/polymeric carbon nitride dual-homojunction photocatalyst with multi-step charge transfer for efficient catalytic carbon dioxide reduction.

Due to the high dissociation energy of carbon dioxide (CO) and sluggish charge transfer dynamics, photocatalytic CO reduction with high performance remains a huge challenge. Herein, we report a novel dual-homojunction photocatalyst comprising of cyano/cyanamide groups co-modified carbon nitride (CN-TH) intramolecular homojunction and 1 T/2H-MoSe homojunction (denoted as 1 T/2H-MoSe/CN-TH) for enhanced photocatalytic CO reduction. In this dual-homojunction photocatalyst, the intramolecular CN-TH homojunction could promote the intralayer charge separation and transfer owing to the strong electron-withdrawing capabilities of the two-type cyanamide, while the 1 T/2H-MoSe homojunction mainly contributes to a promote interlayer charge transport of CN-TH. This could consequently induce a tandem multi-step charge transfer and accelerate the charge transfer dynamics, resulting in enhanced CO reduction activities. Thanks to this tandem multi-step charge transfer, the optimized 1 T/2H-MoSe/CN-TH dual-homojunction photocatalyst presented a high CO yield of 27.36 μmol·g·h, which is 3.58 and 2.87 times higher than those of 1 T/2H-MoSe/CN and 2H-MoSe/CN-TH single homojunctions, respectively. This work provides a novel strategy for efficient CO reduction via achieving a tandem multi-step charge transfer through designing dual-homojunction photocatalyst.