The limitations of the Haber-Bosch reaction-particularly high-temperature operation-have ignited new interests in low-temperature ammonia-synthesis scenarios. Ambient N2 electroreduction is a compelling alternative, but is impeded by a low ammonia production rate (mostly <10 mmol gcat-1 h-1), small partial current density (<1 mA cm-2), and high-selectivity hydrogen-evolving side-reaction. Herein, we report that room-temperature nitrate electroreduction catalyzed by strained ruthenium nanoclusters generates ammonia at a higher rate (5.56 mol gcat-1 h-1) than the Haber-Bosch process. The primary contributor to such performance is hydrogen radicals, which are generated by suppressing hydrogen-hydrogen dimerization during water splitting enabled by the tensile lattice strains. The radicals expedite nitrate-to-ammonia conversion by hydrogenating intermediates of the rate-limiting steps at lower kinetic barriers. The strained nanostructures can maintain nearly 100% ammonia-evolving selectivity at >120 mA cm-2 current densities for 100 hours due to the robust subsurface Ru-O coordination. These findings highlight the potential of nitrate electroreduction in real-world, low-temperature ammonia synthesis.

中文翻译：

---

硝酸盐在应变钌纳米团簇上的高效电合成氨

Haber-Bosch 反应的局限性——尤其是高温操作——引发了人们对低温氨合成场景的新兴趣。环境 N2 电还原是一种引人注目的替代方法，但受到氨生成率低（大多数 <10 mmol gcat-1 h-1）、小部分电流密度（<1 mA cm-2）和高选择性析氢的阻碍副反应。在此，我们报告了由应变钌纳米团簇催化的室温硝酸盐电还原以比 Haber-Bosch 工艺更高的速率（5.56 mol gcat-1 h-1）产生氨。这种性能的主要贡献者是氢自由基，它是通过在拉伸晶格应变实现的水分解过程中抑制氢-氢二聚作用而产生的。自由基通过在较低的动力学势垒下氢化限速步骤的中间体来加速硝酸盐到氨的转化。由于强大的亚表面 Ru-O 配位，应变纳米结构可以在 >120 mA cm-2 电流密度下保持近 100% 的氨演化选择性 100 小时。这些发现突出了硝酸盐电还原在现实世界的低温氨合成中的潜力。