Ammonia (NH₃) is an essential chemical in agriculture and industry, which plays a crucial role in human life and sustainable development. To date, ammonia production mainly relies on the energy-intensive Haber-Bosch process, resulting in significant energy consumption and CO₂ emissions. Electrocatalytic nitrogen reduction reaction (NRR) that can produce NH₃ under ambient conditions is considered as a potential alternative to Haber-Bosch. However, electrocatalytic NRR has various limitations, including low ammonia yield, inferior selectivity due to competing hydrogen evolution reactions, and sluggish reaction kinetics. By virtue of maximum metal atom utilization and tunable electronic structure, atomically dispersed metal catalysts (ADMCs) offer great opportunities for NRR performance optimization, and thus being the most promising NRR catalysts. In this review, we summarize the developmental evolution of ADMCs from homogeneous to heterogeneous phases. We start with a fundamental understanding of the reaction mechanism, detection methods, and key evaluation parameters of NRR. Following this, atomically dispersed homogeneous metal catalysts, including noble metal-based, transition metal-based, and titanium chloride-based, are presented with their advantages and disadvantages analyzed in detail. To conquer the shortcomings of homogenous catalysts, heterogenous catalysts with various supports are more appealing and their recent progress is documented as well. Finally, we present the challenges and perspectives of the ADMCs catalysts for NRR, aiming to provide guidance for advanced NRR catalyst design.

氨（NH ₃）是农业和工业中必不可少的化学物质，对人类生活和可持续发展起着至关重要的作用。迄今为止，合成氨生产主要依赖于能源密集型Haber-Bosch工艺，导致大量的能源消耗和CO ₂排放。可产生NH _{3的电催化氮还原反应（NRR）}在环境条件下被认为是 Haber-Bosch 的潜在替代品。然而，电催化 NRR 具有各种局限性，包括氨产率低、由于竞争性析氢反应导致的选择性差以及反应动力学缓慢。凭借最大的金属原子利用率和可调电子结构，原子分散金属催化剂（ADMC）为NRR性能优化提供了巨大的机会，因此是最有前途的NRR催化剂。在这篇综述中，我们总结了 ADMC 从同质相到异质相的发展演变。我们从对 NRR 的反应机制、检测方法和关键评估参数的基本了解开始。在此之后，原子分散的均相金属催化剂，包括贵金属基、过渡金属基、和氯化钛基，详细分析了它们的优缺点。为了克服均相催化剂的缺点，具有各种载体的多相催化剂更具吸引力，并且也记录了它们的最新进展。最后，我们介绍了用于 NRR 的 ADMCs 催化剂的挑战和前景，旨在为先进的 NRR 催化剂设计提供指导。