Chemical looping ammonia synthesis (CLAS) is promising to achieve decentralized ammonia synthesis under ambient pressure. Here, we develop a highly selective composite nitrogen carrier for efficient CLAS based on transition metals (TMs=Co, Ni, Fe) decorated chromium nitride (CrN). Systematic studies indicate that the pristine CrN is extremely inert: only 4.5% lattice nitrogen can be consumed in reacting with H₂ (700 °C, 1 bar). Upon loading cobalt, the composite nitrogen carrier achieves lattice nitrogen conversion of 50.7% and ammonia selectivity up to 98.1%. Furthermore, Co-CrN exhibits excellent CLAS performance, attaining an average ammonia production rate of 466.1 μmol g⁻¹ h⁻¹ in 12 chemical loopings, which is ∼10 times that of the pristine CrN. Theoretical calculations reveal that the nitrogen vacancies generated in hydrogenation play a crucial role as activation centers for N₂ fixation through a Mars–van Krevelen mechanism. This work provides a novel strategy to optimize nitrogen carriers for enhanced CLAS.

化学循环氨合成（CLAS）有望在常压下实现分散氨合成。在这里，我们开发了一种基于过渡金属（TMs=Co、Ni、Fe）装饰氮化铬（CrN）的高效 CLAS 的高选择性复合氮载体。_{系统研究表明，原始CrN 具有极强的惰性：与H 2 (700 °C，1 bar)}反应时仅消耗4.5% 的晶格氮。负载钴后，复合氮载体的晶格氮转化率达到50.7%，氨​​选择性高达98.1%。此外，Co-CrN表现出优异的CLAS性能，平均氨生成率为466.1 μmol g ^-1 h ^-1共有 12 个化学环，是原始 CrN 的 10 倍。理论计算表明，氢化过程中产生的氮空位作为通过Mars-van Krevelen机制固定N ₂的活化中心发挥着至关重要的作用。这项工作提供了一种优化氮载体以增强 CLAS 的新策略。