Comprehending the electronic configurations of single-atom catalysts (SACs) by fine-tuning the coordination microenvironment for reinforcing electrocatalytic activity for rechargeable lithium–sulfur batteries is of noteworthy significance for boosting sulfur-evolution kinetics, lowering reaction barriers, and alleviating lithium dendrite deterioration. Herein, an extraordinary electronic configuration of isolated Fe coordinated with unsaturated atoms in metallic vacancies derived from atomic arrangement driven by phase-restructured vanadium nitride MXenes was modulated by optimizing the coordination microenvironment during fluoride-free room-temperature organic molten salt in situ etching and using a self-reduced strategy. X-Ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses elucidated that isolated Fe was coordinated with in-plane nitrogen and oxygen atoms, with axial-bridged nitrogen-doped carbon encapsulated on the surface of phase-restructured vanadium nitride. Density functional theory calculations and experimental results comprehensively elucidated axial distortion originating from the bridged nitrogen reordering Fe d-orbital splitting manner to lower the d_z² level, which not only strengthened the adsorption energy to hamper the shuttle effect and decreased the activation energy barrier to boost redox kinetics but also engendered lithiophilicity to lower polarization and homogenize ion flux to suppress lithium dendrite growth. These merits of the Fe_N4-O-NC-VN-modified separator encourage the development of rechargeable lithium–sulfur batteries to promote a dramatic improvement in the reversible capacity on the cathode and a satisfactory cycling lifespan on the anode. This work offers a comprehensive understanding of the electronic configuration of SACs and its modulation by fine-tuning the coordination microenvironment to optimize electrocatalyst activity.

中文翻译：

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通过操纵相重构的二维氮化钒MXenes来触发与面内氮协调的特殊氮桥原子铁的电子微环境，从而增强锂硫电池的性能


通过微调配位微环境来理解单原子催化剂（SAC）的电子构型，以增强可充电锂硫电池的电催化活性，对于提高硫析出动力学、降低反应势垒和减轻锂枝晶劣化具有重要意义。在此，通过优化无氟化物室温有机熔盐原位蚀刻过程中的配位微环境，并利用相重构氮化钒MXenes驱动的原子排列衍生的金属空位中的不饱和原子与孤立的Fe配位的非凡电子构型进行了调制自我减少的策略。 X射线吸收近边缘结构（XANES）和扩展X射线吸收精细结构（EXAFS）分析表明，孤立的Fe与面内氮和氧原子配位，并在表面包封有轴向桥联的氮掺杂碳相重组氮化钒。密度泛函理论计算和实验结果全面阐明了桥氮重排Fe d轨道分裂方式产生的轴向畸变降低了d _{z ²}能级，不仅增强了吸附能以阻碍穿梭效应，而且降低了活化能垒以降低d z 2 能级。促进氧化还原动力学，但也产生亲锂性以降低极化并使离子通量均匀化以抑制锂枝晶生长。 Fe _N4-O-NC -VN改性隔膜的这些优点鼓励了可充电锂硫电池的发展，以促进阴极可逆容量的显着提高和阳极令人满意的循环寿命。这项工作通过微调配位微环境来优化电催化剂活性，全面了解 SAC 的电子配置及其调节。