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Vacancy-enabled N_2 activation for ammonia synthesis on an Ni-loaded catalyst

机译：在Ni负载催化剂上启用空位的N_2活化对氨合成的活化

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摘要

Ammonia (NH3) is pivotal to the fertilizer industry and one of the most commonly produced chemicals(1). The direct use of atmospheric nitrogen (N-2) had been challenging, owing to its large bond energy (945 kilojoules per mole)(2,3), until the development of the Haber-Bosch process. Subsequently, many strategies have been explored to reduce the activation barrier of the N equivalent to N bond and make the process more efficient. These include using alkali and alkaline earth metal oxides as promoters to boost the performance of traditional iron- and ruthenium-based catalysts(4-6)via electron transfer from the promoters to the antibonding bonds of N(2)through transition metals(7,8). An electride support further lowers the activation barrier because its low work function and high electron density enhance electron transfer to transition metals(9,10). This strategy has facilitated ammonia synthesis from N(2)dissociation(11)and enabled catalytic operation under mild conditions; however, it requires the use of ruthenium, which is expensive. Alternatively, it has been shown that nitrides containing surface nitrogen vacancies can activate N-2(refs.(12-15)). Here we report that nickel-loaded lanthanum nitride (LaN) enables stable and highly efficient ammonia synthesis, owing to a dual-site mechanism that avoids commonly encountered scaling relations. Kinetic and isotope-labelling experiments, as well as density functional theory calculations, confirm that nitrogen vacancies are generated on LaN with low formation energy, and efficiently bind and activate N-2. In addition, the nickel metal loaded onto the nitride dissociates H-2. The use of distinct sites for activating the two reactants, and the synergy between them, results in the nickel-loaded LaN catalyst exhibiting an activity that far exceeds that of more conventional cobalt- and nickel-based catalysts, and that is comparable to that of ruthenium-based catalysts. Our results illustrate the potential of using vacancy sites in reaction cycles, and introduce a design concept for catalysts for ammonia synthesis, using naturally abundant elements.Ammonia is synthesized using a dual-site approach, whereby nitrogen vacancies on LaN activate N-2, which then reacts with hydrogen atoms produced over the Ni metal to give ammonia.
机译：氨（NH3）对肥料工业的关键和最常用的化学品之一（1）。由于其大的债券能量（每摩尔945千钟）（2,3），直至哈斯博士工艺发展，直接使用大气氮（N-2）一直挑战。随后，已经探索了许多策略以减少相当于N键的N相当的激活屏障，并使该过程更有效。这些包括使用碱和碱土金属氧化物作为推动者，通过从促进剂到通过过渡金属的电子转移来提高传统铁和钌基催化剂（4-6）的性能（7， 8）。电极载体进一步降低激活屏障，因为其低功函数和高电子密度增强了电子转移到过渡金属（9,10）。该策略促进了N（2）解离（11）的氨合成，并在轻度条件下使催化作用能够;然而，它需要使用钌，这是昂贵的。或者，已经证明含有表面氮空位的氮化物可以活化N-2（参考文献（12-15））。在这里，我们报告称，由于避免了常见的缩放关系，避免了额外遇到的缩放关系的双场机制，镍载荷镧氮化物（LAN）能够实现稳定和高效的氨合成。动力学和同位素标记实验以及密度函数理论计算，证实氮空位在具有低形成能量的LAN上产生，有效地结合和激活N-2。另外，负载到氮化物上的镍金属解离H-2。使用不同的位点来激活两个反应物，以及它们之间的协同作用，导致镍加载的LAN催化剂，其具有远超过更常规的钴和镍基催化剂的活性，并且与其相当基于钌的催化剂。我们的结果说明了使用反应循环中空位位点的潜力，并引入氨合成催化剂的设计理念，使用天然丰富的元素。使用双位点方法合成，由此局部的氮空缺障碍率为N-2。然后与在Ni金属上产生的氢原子反应，得到氨。

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  • 来源
    《Nature》 |2020年第7816期|391-395|共5页
  • 作者

    Ye Tian-Nan; Park Sang-Won; Lu Yangfan; Li Jiang; Sasase Masato; Kitano Masaaki; Tada Tomofumi; Hosono Hideo;

  • 作者单位

    Tokyo Inst Technol Mat Res Ctr Element Strategy Yokohama Kanagawa Japan;

    Tokyo Inst Technol Mat Res Ctr Element Strategy Yokohama Kanagawa Japan;

    Tokyo Inst Technol Mat Res Ctr Element Strategy Yokohama Kanagawa Japan;

    Tokyo Inst Technol Mat Res Ctr Element Strategy Yokohama Kanagawa Japan;

    Tokyo Inst Technol Mat Res Ctr Element Strategy Yokohama Kanagawa Japan;

    Tokyo Inst Technol Mat Res Ctr Element Strategy Yokohama Kanagawa Japan|Japan Sci & Technol Agcy Precursory Res Embryon Sci & Technol PRESTO Saitama Japan;

    Tokyo Inst Technol Mat Res Ctr Element Strategy Yokohama Kanagawa Japan;

    Tokyo Inst Technol Mat Res Ctr Element Strategy Yokohama Kanagawa Japan;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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