Li Jie, Zhan Guangming, Yang Jianhua, Quan Fengjiao, Mao Chengliang, Liu Yang, Wang Bo, Lei Fengcai, Li Lejing, Chan Alice W M, Xu Liangpang, Shi Yanbiao, Du Yi, Hao Weichang, Wong Po Keung, Wang Jianfang, Dou Shi-Xue, Zhang Lizhi, Yu Jimmy C
Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Institute of Environmental & Applied Chemistry, College of Chemistry, Central China Normal University, 152 Luoyu Road, Wuhan 430079, China.
Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Wollongong, New South Wales 2500, Australia.
J Am Chem Soc. 2020 Apr 15;142(15):7036-7046. doi: 10.1021/jacs.0c00418. Epub 2020 Apr 6.
The limitations of the Haber-Bosch reaction, particularly high-temperature operation, have ignited new interests in low-temperature ammonia-synthesis scenarios. Ambient N electroreduction is a compelling alternative but is impeded by a low ammonia production rate (mostly <10 mmol g h), a small partial current density (<1 mA cm), and a 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 g h) 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 current densities for 100 h due to the robust subsurface Ru-O coordination. These findings highlight the potential of nitrate electroreduction in real-world, low-temperature ammonia synthesis.
哈伯-博施法的局限性，尤其是高温操作，引发了人们对低温氨合成方案的新兴趣。常温氮电还原是一种引人注目的替代方法，但受到氨产率低（大多<10 mmol g⁻¹ h⁻¹）、小的分电流密度（<1 mA cm⁻²）和高选择性析氢副反应的阻碍。在此，我们报道由应变钌纳米团簇催化的室温硝酸盐电还原产生氨的速率（5.56 mol g⁻¹ h⁻¹）高于哈伯-博施法。这种性能的主要贡献者是氢自由基，它们是通过在拉伸晶格应变使能的水分解过程中抑制氢-氢二聚化而产生的。这些自由基通过在较低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，应变纳米结构在>120 mA cm⁻²的电流密度下可保持近100%的析氨选择性达100小时。这些发现突出了硝酸盐电还原在实际低温氨合成中的潜力。
