Recently, the research group of Prof. Jie Zeng from School of Chemistry and Materials Science & Hefei National Laboratory for Physical Sciences at the Microscale cooperated with Prof. Rui Si from Shanghai Institute of Applied Physics has made a breakthrough in NH₃ production from electrochemical reduction of N₂ by using Ru single-atom distributed on nitrogen-doped carbon (Ru SAs/N-C) as electrocatalysts. Ru SAs/N-C possessed a record-high yield rate for NH₃ production toward N₂ electrochemical reduction. This work was published onAdvanced Materials (Adv. Mater.2018, 30, 1803498) entitled as “Achieving a Record-High Yield Rate of 120.9 μg_NH3 mg^-1_cat. h^-1 for N₂ Electrochemical Reduction over Ru Single-atom Catalysts”. Dr. Zhigang Geng and graduate student Yan Liu were the co-first authors of this work.

 Nitrogen is nutritionally unavailable due to the highly stable N≡N covalent triple bond. As such, high pressure and temperature (150-350 atm, 350-550 ^oC) are required to convert N₂ to NH₃ through Haber-Bosch process in industry. The harsh condition of Haber-Bosch process results in 1-2% of the world’s annual energy supply consumption. Moreover, the NH₃ synthesis through Haber-Bosch process requires hydrogen gas as source, which is generated from the steam reforming of natural gas with a large concomitant emission of CO₂. In view of the fossil fuels shortage and global climate change, it is highly desired to explore a catalytic process that produces NH₃ under ambient conditions. As a strategy of NH₃ synthesis under the ambient reaction condition, electrochemical reduction of N₂ into NH₃ has attracted particular attention. However, to date, the highest NH₃ yield rate among the reported electrocatalysts was only 23.8 μg_NH3 mg^-1_cat. h^-1 towards N₂ electrochemical reduction. Therefore, the development of highly active electrocatalysts for NH₃ production is desirable but remains challenging.

 Herein, researchers prepared Ru SAs/N-C via pyrolyzing the Ru-containing derivative of zeolitic imidazolate frameworks (ZIF-8) which achieved record-high activity towards N₂ electrochemical reduction. At -0.2 V vs reversible hydrogen electrode, Ru SAs/N-C exhibited a Faradaic efficiency of 29.6% for NH₃ production with partial current density of -0.13 mA cm^-2. Notably, the yield rate of Ru SAs/N-C reached 120.9 μg_NH3 mg^-1_cat. h^-1, which was one order of magnitude higher than the highest value ever reported. Experimental result and theoretical calculation study further revealed that Ru SAs/N-C promoted N₂ dissociation, thereby resulting in enhanced activity. This work provides a guideline for the generation of atomically dispersed uniform single atomic materials and paves a new avenue for further research in the application of single atomic catalysts towards N₂ electrochemical reduction.

 This work was supported by CAS, MOST of China, National Natural Science Foundation of China, and Anhui Provincial Key Scientific and Technological Project.

 Source:https://onlinelibrary.wiley.com/doi/epdf/10.1002/adma.201803498