Unraveling Electronic Microenviroment of Iron Single Atom Modulated by Nitrogen‐Bridged Ligands in MBene Toward Bilateral Sulfur Redox Chemistry

Abstract

AbstractExploring functional substrates for single‐atom electrocatalysts and precisely modulating their electronic microenvironments are of significant importance for sulfur redox chemistry in lithium‐sulfur batteries (LSBs) with unsatisfactory shuttle effects and sluggish redox kinetic. Herein, the electronic microenvironment of atomic ion (Fe) is rationally unraveled and modulated by nitrogen (N)‐bridged ligands that are engineered by metallic vacancies in MoB spontaneously trapping atomic Fe by fluorine‐free organic molten salt in situ etching and self‐reduction strategy. Intriguingly, these atomic Fe can be coordinated with adjacent in‐plane boron (B), lattice oxygen (O) and axial bridged N‐doped carbon (NC) to construct the distinctive Fe configuration (FeB4‐O‐NC‐MoB). Theorical calculations and experimental investigations unveil the electronic microenvironment of Fe disturbed from axial bridged N to construct octahedra configuration that can reinforce adsorption energy and lower energy barrier by Fe‐S and N‐Li bonds to suppress shuttle effect and expedite bidirectional redox kinetics. Thus, FeB4‐O‐NC‐MoB modified separator in LSBs delivers impressive reversible capacities (765 mAh g−1 at 0.5 C after 500 cycles and 541.9 mAh g−1 at 2 C after 5000 cycles). This work affords a feasible strategy for modulating electronic microenvironment by manipulating coordination configuration of single‐atom electrocatalyst to boost the bilateral sulfur redox chemistry.