Ammonia plays an essential role in agriculture and next-generation energy systems but is currently synthesized industrially through the Haber–Bosh (HB) process under harsh conditions with high CO₂ emissions. Chemical looping ammonia synthesis (CLAS) is an attractive alternative to the traditional HB process as it can break the Brønsted–Evans–Polanyi (BEP) scaling relationship and circumvent the competitive adsorption of N₂ and H₂ on metal catalysts by decoupling ammonia production into multiple reaction steps. The realization of highly efficient CLAS relies on developing redox catalysts with high activity at low temperatures. This review describes recent theoretical and experimental progresses in CLAS. The rational design of redox catalysts underlines the advantages of combined numerical and experimental approaches for the development of efficient redox catalysts towards green and efficient CLAS processes. Redox catalysts and external field-assisted technologies for lowering the reaction temperature and accelerating the reaction kinetics of CLAS are spotlighted, and relevant reaction mechanisms are discussed. The feasibility of the CLAS process based on the techno-economic analysis is reviewed. The challenges and opportunities of redox catalysts and reaction systems for CLAS are further discussed.

中文翻译：

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迈向绿色高效的化学循环氨合成：设计原理和先进的氧化还原催化剂

氨在农业和下一代能源系统中发挥着重要作用，但目前工业上是通过哈伯-波什（HB）工艺在CO ₂排放量高的恶劣条件下合成的。化学循环氨合成 (CLAS) 是传统 HB 工艺的一种有吸引力的替代方案，因为它可以打破 Brønsted-Evans-Polanyi (BEP) 结垢关系，并通过将氨生产解耦来避免 N ₂和 H ₂在金属催化剂上的竞争吸附多个反应步骤。高效CLAS的实现依赖于开发在低温下具有高活性的氧化还原催化剂。这篇综述描述了 CLAS 的最新理论和实验进展。氧化还原催化剂的合理设计强调了结合数值和实验方法开发高效氧化还原催化剂以实现绿色高效 CLAS 工艺的优势。重点介绍了降低反应温度和加速 CLAS 反应动力学的氧化还原催化剂和外场辅助技术，并讨论了相关反应机理。回顾了基于技术经济分析的CLAS工艺的可行性。进一步讨论了 CLAS 氧化还原催化剂和反应系统的挑战和机遇。