The electrocatalytic N₂ reduction reaction (NRR) offers an alternative to the traditional Haber–Bosch (H–B) process for the synthesis of ammonia (NH₃) and has received a surge of interest recently. However, as the prerequisite step for an efficient NRR, the N₂ activation process over an electrocatalyst is rather difficult to be realized under mild conditions due to the thermodynamic stability and chemical inertness of the N₂ molecule, which greatly limits the selectivity and activity of the NRR process, as well as the development of this renewable synthesis route for NH₃. To date, a variety of electrocatalysts have been developed for effective N₂ activation in the past five years, although the presented activation abilities for N₂ molecules remain unsatisfactory even on the laboratory scale, and the corresponding design concepts/principles are still at the trial-and-error stage. Instead of focusing on labeling and classifying NRR electrocatalysts that have been extensively reviewed elsewhere, we herein present a timely and comprehensive review of emerging strategies to activate the inert N₂ molecule for NH₃ electrosynthesis at the microscopic and macroscopic level on the basis of an in-depth understanding of the physicochemical properties and microelectronic structure of the N₂ molecule. We initially analyze the physicochemical properties and the microelectronic structure of the N₂ molecule from the perspective of molecular orbital theory. On the basis of this, we then emphasize the microscopic electronic effects of electrocatalysts for enhancing N₂ activation at length, typically covering σ-donation, π-backdonation, and σ-donation/π-backdonation effects, along with the design concepts/principles of electrocatalysts. Subsequently, the driving forces of macroscopic external fields (such as light, plasma, etc.) and the local microenvironment regulation-induced built-in electrostatic fields for assisting N₂ activation are introduced. In addition, the methodologies for studying the N₂ activation process over electrocatalyst surfaces are also presented from theoretical and experimental perspectives. Finally, we look at the future research directions and opportunities for improving N₂ activation and stimulating the practical application of NRR technology, covering electrocatalyst engineering, process intensification, and device architecture.

中文翻译：

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激活惰性氮分子以实现高效氨电合成的策略：现状、挑战和前景

电催化 N ₂还原反应 (NRR) 为合成氨 (NH ₃ ) 的传统 Haber-Bosch (H-B) 工艺提供了一种替代方法，并且最近受到了极大的关注。然而，作为高效NRR的先决条件，由于N 2 分子的热力学稳定性和化学惰性，电催化剂上的N ₂活化过程在温和条件下难以实现，这极大地限制了N ₂分子的选择性和活性。 NRR 工艺，以及这种可再生的 NH ₃合成路线的开发。迄今为止，已经开发了多种电催化剂来实现有效的 N _{2在过去的五年中，尽管N 2}分子的活化能力即使在实验室规模上仍不能令人满意，并且相应的设计概念/原理仍处于试错阶段。我们没有专注于标记和分类已在其他地方广泛审查过的 NRR 电催化剂，而是在本文中及时全面地回顾了在微观和宏观水平上激活惰性 N ₂分子用于 NH ₃电合成的新兴策略。 -深入了解N _{2的物理化学性质和微电子结构}分子。我们初步从分子轨道理论的角度分析了N ₂分子的物理化学性质和微电子结构。在此基础上，我们随后强调了电催化剂的微观电子效应以增强 N ₂活化，通常包括 σ-donation、π-backdonation 和 σ-donation/π-backdonation 效应，以及设计概念/原理的电催化剂。随后，介绍了宏观外场（如光、等离子体等）的驱动力和局部微环境调控诱导的内建静电场辅助N ₂活化。此外，研究 N _2的方法还从理论和实验的角度介绍了电催化剂表面的活化过程。_{最后，我们展望了改进 N 2}活化和激发 NRR 技术实际应用的未来研究方向和机遇，涵盖电催化剂工程、工艺强化和器件架构。