Light-Induced Ammonia Generation over Defective Carbon Nitride Modified with Pyrite

Photocatalytic nitrogen fixation under ambient conditions is currently widely explored in an attempt to develop a sustainable alternative for the Haber-Bosch process. In this work, defect-rich carbon nitride, one of the most investigated photocatalysts reported in literature for ammonia generation, is combined with earth-abundant and bioinspired FeS2 to improve the activity for ammonia production. By this combination, an activity enhancement of approximate to 400% compared to unmodified carbon nitride is achieved. The optimal FeS2 loading is established to be 1 wt%, with ammonia yields of up to 800 mu g L-1 after irradiation for 7 h. By detailed material characterization of the electronic and material properties of the composites before and after the photocatalytic reaction, it is revealed that NH3 generation occurs not photocatalytically from N-2, but via a light-induced reduction of (sic)N-CN groups adjacent to nitrogen vacancies in the structure of defect-rich carbon nitride. FeS2 acts similar to a cocatalyst, enhancing the ammonia yield by pi-back-donation from Fe-centers to the imine nitrogen of the defect-rich carbon nitride, thereby activating the structure and boosting the ammonia generation from cyano groups.

Automated summary

Photocatalytic nitrogen fixation is explored as a sustainable alternative for the Haber-Bosch process. This study combines defect-rich carbon nitride with FeS2 to improve ammonia production. Detailed material characterization reveals that ammonia is generated via light-induced reduction of (sic)N-CN groups in the carbon nitride structure. FeS2 acts as a cocatalyst, enhancing ammonia yield by pi-back-donation from Fe-centers.