Nitrogen cycle on N-doped graphene loaded TiO₂ for efficient photocatalytic dinitrogen conversion

Photocatalytic dinitrogen conversion through artificial nitrogenase is known as the holy grail for ammonia production. The effective utilization of photogenerated charge carriers is essential for optimizing its photocatalytic performance, yet underlying charge carrier separation and dinitrogen conversion mechanisms steering such a reaction on a catalyst, especially a nitrogen-containing system, remains underdeveloped. Here, by integrating rutile TiO₂ with N-doped graphene, complete functions of natural nitrogenase are duplicated for overall photocatalytic dinitrogen conversion to generate ammonia and nitric oxide. More importantly, we demonstrate that N-dopant sites can serve as nitrogen carriers for sustaining the dinitrogen conversion via the N-cycle pathway, where the nitrogen element is detached from N-doped graphene and consumed for ammonia generation and then replenished by the atmospheric dinitrogen during the reaction. Our work not only offers a viable way to imitate the natural nitrogenase system, but also shines light on the dinitrogen conversion pathway for N-containing photocatalysts.