锕系-铀基单原子催化用于电化学氮气固定

锕系催化剂因其独特的5f轨道和灵活的氧化态而被认为是用于N2固定有希望的候选者。中国科学技术大学姚涛教授和西南科技大学竹文坤教授团队合作，首次报道了通过氧空位限域铀单原子锚定在TiO2纳米片上，用于N2电还原。铀单原子催化剂的NH3产率高达40.57 μg/(h mg)，法拉第效率高达25.77%，在已报道的无氮催化剂中名列前茅。同位素标记原位同步辐射红外光谱验证关键*N2Hy反应中间物种来自供给的N2。通过使用原位X射线吸收光谱，确定在工作条件下铀单原子和TiO2晶格之间形成更多U-Olatt配位，金属-载体相互作用明显增强。理论模拟表明，演化的1Oads-U-4Olatt模块充当关键的电子回馈中心，以降低N2解离和第一加氢步骤的热力学能垒。这项工作为定制金属活性位点与载体之间的相互作用提供了可能性，并为设计高性能的锕系单原子催化剂提供了支持。

Fig. 1. Synthesis and structural characterizations of U-SAs/TiO2. (a) Schematic illustration of synthesis procedure of U-SAs/TiO2. (b) TEM, and (c) HR-TEM images of U-SAs/TiO2. (d) The corresponding EDS mapping of U-SAs/TiO2. (e) HAADF-STEM, and (f) magnifications images of U-SAs/TiO2. (g) XPS spectra of O 1s for pristine TiO2, TiO2-x and USAs/TiO2 catalysts.

Fig. 2. Electrocatalytic performance toward eNRR. (a) LSV tests in Ar and N2 saturated environment under ambient conditions. (b) Ammonia yield rate and faradaic efficiency of the U-SAs/TiO2 at various potentials. (c) Ammonia yield rate and faradaic efficiency of the TiO2, TiO2-x, and U-SAs/TiO2 at -0.55 V vs. RHE. (d) 1H NMR analysis of the electrolyte fed by 14N2 and 15N2 gas after the electrolytic reaction. (e) Ammonia yield rate and faradaic efficiency of U-SAs/TiO2, with other reported nitrogen-free eNRR electrocatalysts.

Fig. 3. Operando X-ray absorption spectroscopy studies. (a) Operando XANES spectra recorded at the U L3-edge of U-SAs/TiO2, at different applied voltages during eNRR, and the XANES data of the reference standards of UO2(NO3)2, UO2, and U3O8. Inset, magnified preedge XANES region. (b) Corresponding k2-weighted Fourier transform (FT) spectra. The insets show the corresponding optimized geometric configurations based on DFT calculations. (c) Wavelet transforms for U-SAs/TiO2 under ex-situ, -0.10, -0.55 V, and after reaction. Note: the vertical dashed lines are provided to guide the eye.

Fig. 4. Operando SR-FTIR study. (a) Three-dimensional operando SR-FTIR spectra at various potentials for U-SAs/TiO2. (b) Operando SR-FTIR spectra at various potentials for USAs/TiO2 during the NRR process. (c) Isotope-labeling operando SR-FTIR spectra at various potentials for U-SAs/TiO2 during the NRR process. (d) Schematic diagram of the eNRR process occurring on the surface of U-SAs/TiO2.

Fig. 5. Theoretical investigations on eNRR activity. (a) Optimized reactant/catalysts vertical end-on and horizontal side-on configurations and free-energy diagrams for eNRR over TiO2 and U-SAs/TiO2 slab through distal, alternating, and enzymatic mechanisms as well as the corresponding structures of the reaction intermediates. (b) The PDOS of *NNH intermediate adsorbed on the TiO2 and U-SAs/TiO2 slabs. Electron density difference plot of the *NNH intermediate adsorption structure for pristine TiO2 (c), U3O8 (d) and U-SAs/TiO2 slab (e), yellow contours indicate electron accumulation and light green contours denote electron deletion. (f) The difference in limiting potentials for eNRR and HER on the pristine TiO2, U3O8, Ru (001) and U-SAs/TiO2 slab. The red, light blue, and gray balls represent O, Ti, U, and N atoms, respectively. * represents an adsorption site.

■ 原文信息 

Tao Chen, Tong Liu, Beibei Pang, Tao Ding, Wei Zhang, Xinyi Shen, Dan Wu, Lan Wang, Xiaokang Liu, Qiquan Luo, Wenkun Zhu, Tao Yao. Actinide-uranium single-atom catalysis for electrochemical nitrogen fixation. Science Bulletin, 2022, 67(19): 2001-2012【点击下方阅读原文】