Efficient photofixation of nitrogen to ammonia over an S-scheme-based NiSnO₃-g-C₃N₄ heterojunction

A limited injection of photogenerated electrons in N₂ molecules is the core problem limiting the performance of heterojunction materials in photofixing N₂ to ammonia. In this study, an inexpensive Sn-based perovskite (NiSnO₃, NSO) was anchored over the g-C₃N₄ (gCN) sheets under mild reaction conditions to develop an S-scheme heterojunction for the photocatalytic nitrogen reduction reaction. The NSO-gCN heterojunction, utilizing methanol as a sacrificial agent, showed remarkable N₂ reduction capability with an impressive ammonia evolution of 566 µmolg⁻¹h⁻¹, surpassing that of gCN and NSO by the factor of 3.6 and 40, respectively, in visible light. The significantly improved performance of the material was attributed to the S-scheme charge transfer mechanism. The NSO-gCN photocatalyst showed good stability with only a marginal decrease measured in the activity over 3 cycles of the photocatalytic reaction. The study reveals a new strategy to design the highly efficient S-scheme-based heterojunctions by using Sn-based perovskite for sustainable ammonia synthesis.