Small molecule π-conjugated electron acceptor for highly enhanced photocatalytic nitrogen reduction of BiOBr

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 pi 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 15 N-2 was used to confirm that the ammonia is formed form the fixation of N-2 . 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 N-2 reduction. (C) 2021 Published by Elsevier Ltd on behalf of Chinese Society for Metals.