Actinide-uranium single-atom catalysis for electrochemical nitrogen fixation

锕系-铀基单原子催化用于电化学氮气固定

Actinide-based catalysts have been regarded as promising candidates for N_(2) fixation owing to their unique 5f orbital with flexible oxidation states.Herein,we report for the first time the dispersion of uranium(U)single atoms on TiO_(2) nanosheets via oxygen vacancy confinement for N_(2) electroreduction.The single-atom U catalyst exhibited a high NH_(3) yield of 40.57μg h^(-1) mg^(-1),with a reasonably high Faraday efficiency of 25.77%,ranking first among the reported nitrogen-free catalysts.Isotope-labeling operando synchrotron infrared spectroscopy verifies that the key*N_(2)H_(y) intermediate species was derived from the N_(2) gas of the feed.By using operando X-ray absorption spectroscopy,we found enhanced metal-support interaction between U single atoms and TiO_(2) lattice with more U-O_(latt) coordination under working conditions.Theoretical simulations suggest that the evolved 1O_(ads)-U-4O_(latt) moieties act as a critical electronfeedback center,lowering the thermodynamic energy barrier for the N_(2) dissociation and the first hydrogenation step.This work provides the possibility of tailoring the interaction between metal active sites and supports for designing high-performance actinide-based single-atom catalysts.

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N_(2)固定有希望的候选者.本文首次报道了通过氧空位限域铀单原子锚定在TiO_(2)纳米片上,用于N_(2)电还原.铀单原子催化剂的NH_(3)产率高达40.57μg h^(-1) mg^(-1),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*N_(2)H_(y)反应中间物种来自供给的N_(2).原位X射线吸收光谱研究表明,在工作条件下铀单原子和TiO_(2)晶格之间形成更多U-O_(latt)配位,金属-载体相互作用明显增强.理论模拟表明,演化的1O_(ads)-U-4O_(latt)模块充当关键的电子回馈中心,以降低N_(2)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.