Electrochemical ammonia synthesis (EAS) presents an attractive alternative to the Haber–Bosch process due to the benefits of energy saving, low carbon emission, environmental friendliness, and so on. However, the competing hydrogen evolution reaction (HER) severely limits the yield, selectivity, and current efficiency of NH3. Although the accumulation and self‐aggregation of active hydrogen (H*) are the primary causes of the competing HER, it also serves as the critical active species and intermediate for the multistep hydrogenation and deoxygenation processes. Therefore, the sensible regulation of the H* generation and consumption are essential for enhancing EAS performance. And it is significant to thoroughly review the current strategies for H* control. Herein, a comprehensive introduction of H* to provide a fundamental understanding of its role in electrochemical reactions, including generation, conversion, identification, and quantification protocols is first proposed. In addition, the role and control strategies of H* in EAS are carefully summarized with a particular focus on regulating H* generation and consumption to enhance the activity, selectivity, and Faradaic efficiency. Finally, the remaining challenges and perspectives are discussed. This critical review is intended to offer a profound understanding of the regulation of H* in electrochemical reactions and the development of EAS technology.

中文翻译：

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电化学氨合成用活性氢

电化学氨合成（EAS）由于具有节能、低碳排放、环境友好等优点，成为哈伯-博世工艺的一种有吸引力的替代方案。然而，竞争性析氢反应 (HER) 严重限制了 NH 的产率、选择性和电流效率3。尽管活性氢（H*）的积累和自聚集是竞争HER的主要原因，但它也是多步氢化和脱氧过程的关键活性物质和中间体。因此，合理调节 H* 的产生和消耗对于提高 EAS 性能至关重要。彻底回顾当前的H*控制策略具有重要意义。在此，首次提出了对 H* 的全面介绍，以提供对其在电化学反应（包括生成、转化、识别和定量方案）中的作用的基本了解。此外，还仔细总结了 H* 在 EAS 中的作用和控制策略，特别关注调节 H* 的产生和消耗，以提高活性、选择性和法拉第效率。最后，讨论了剩余的挑战和前景。这篇批判性综述旨在加深对电化学反应中 H* 调控和 EAS 技术发展的理解。