2020同步年報

Energy Science 057 This report features the work of Hengxing Ji and his collab- orators published in Science 370 , 192 (2020), and the work of Yi-Chun Lu and his collaborators published in ACS Energ. Lett. 5 , 1355 (2020). TLS 16A1 BM – Tender X-ray Absorption, Diffraction TLS 20A1 BM – (H-SGM) XAS • XANES, EXAFS • Materials Science, Chemistry, Condensed-matter Physics, Environmental and Earth Science References 1. H. Jin, S. Xin, C. Chuang, W. Li, H. Wang, J. Zhu, H. Xie, T. Zhang, Y. Wan, Z. Qi, W. Yan, Y.-R. Lu, T.-S. Chan, X. Wu, J. B. Goodenough, H. Ji, X. Duan, Science 370 , 192 (2020). 2. Y. Wang, Y.-R. Lu, C.-L. Dong, Y.-C. Lu, ACS Energ. Lett. 5 , 1355 (2020). T he synthesis of ammonia (NH 3 ) from naturally abundant nitrogen (N 2 ) is meaningful for agricultural and industrial pro- duction, but NH 3 is predominantly synthesized with the traditional Haber-Bosch process in industry. This process involves high temperatures and pressures, and causes severe CO 2 emission because of the hydrogen feedstock from the steam refor- mation of natural gas. The electrochemical nitrogen reduction is regarded as an energy-saving and environmentally compati- ble process, which can synthesize NH 3 under ambient conditions utilizing renewable solar or wind energy. Unfortunately, the electrochemical nitrogen reduction reaction (NRR) generally suffers from small ammonia yields and poor Faradaic efficiency because of extremely weak N 2 adsorption and the sluggish cleavage of the strong N ≡ N bond. The rational design of active catalytic centers of efficient NRR electrocatalysts that can efficiently decrease the large activation barrier of N ≡ N and acceler- ate its dissociation is thus still a highly challenging but vitally important issue. Yongwen Tan (Hunan University, China) and his coworkers recently reported single-atomic Ru-modified Mo 2 CT X MXene nanosheets (denoted as SA Ru-Mo 2 CT X ) for efficient electrocatalytic NRR under ambient conditions. The SA Ru-Mo 2 CT X cat- alyst as prepared with an ultralow single-atom Ru loading exhibits high NRR activity with a great rate of NH 3 yield, Faradaic efficiency and excellent stability, out-performing most reported NRR catalysts. Employing operando X-ray absorption spectra (XAS) at TLS 01C1 , 1 simultaneously introducing single-atomic Ru into Mo 2 CT X MXene nanosheets plays a significant role as active sites for catalytic intermediate adsorption and electron back-donation centers, which can effectively promote N 2 acti- vation and decrease the thermodynamic energy barrier of the first hydrogenation step, thereby facilitating the further hydro- genation of absorbed N 2 . For example, the Ru K-edge operando XAS measurements of the SA Ru-Mo 2 CT X nanosheets were performed under NRR working conditions, as shown in Fig. 1 . It was proposed that a N 2 molecule preferentially adsorbs on Fig. 1 : Operando X-ray absorption spectra. (a) Normalized operando Ru K-edge XANES spectra for SA Ru-Mo 2 CT X under various conditions (applied voltage vs. RHE) in K 2 SO 4 solution (0.5 M); insert is a magnified image. (b) Corresponding FT-EXAFS spectra derived from (a). (c) Oxidation state of Ru and radial distance of the main signal under various conditions. [Reproduced from Ref. 1] Decreasing Emissions from Ammonia Production with Electrolysis Single‐atom ruthenium-modified Mo 2 CT X MXene serves as an efficient electrocatalyst to fix nitro- gen under ambient conditions.