Abstract:

Artificial ammonia synthesis using solar energy is of great significance as it can help narrow the gap to the zero-net emission target. However, the current photocatalytic activity is generally too low for mass production. Herein, we report a novel bismuth bromide oxide (BiOBr)-Tetracyanoquinodimethane (TCNQ) photocatalyst prepared via a facile self-assembly method. Due to the well-match band structure of TCNQ and BiOBr, the separation and transfer of photogenerated electron-hole pairs were significantly boosted. More importantly, the abundant delocalized π electrons of TCNQ, and the electron-withdrawing property of TNCQ made electrons efficiently accumulated on the catalysts, which can strengthen the adsorption and cleavage of nitrogen molecules. As a result, the photocatalytic activity increased significantly. The highest ammonia yield of the optimized sample reached 2.617 mg/(h g_cat), which was 5.6-fold as that of pristine BiOBr and higher than the reported BiOBr-based photocatalysts. The isotope labeled ¹⁵N₂ was used to confirm that the ammonia is formed form the fixation of N₂. Meanwhile, the sample also had good stability. After 4-time usage, the photocatalysts still had about 81.8% as the fresh sample. The results of this work provide a new way for optimizing the electronic structure of photocatalysts to achieve highly efficient photochemical N₂ reduction.

Key words: BiOBr, TCNQ, Nitrogen reduction, Electron ccepter, Photocatalysis