Atomic Structure Modification of Fe‒N‒C Catalysts via Morphology Engineering of Graphene for Enhanced Conversion Kinetics of Lithium–Sulfur Batteries
Jiheon Kim, Seong‐Jun Kim, Euiyeon Jung, Dong Hyeon Mok, Vinod K. Paidi, Jae Wook Lee, Hyeon Seok Lee, Yunseo Jeoun, Wonjae Ko, Heejong Shin, Byoung‐Hoon Lee, Shin‐Yeong Kim, Hyunjoong Kim, Ji Hwan Kim, Sung‐Pyo Cho, Kug‐Seung Lee, Seoin Back, Seung‐Ho Yu, Yung‐Eun Sung, Taeghwan Hyeon
Abstract
Abstract Single‐atom M‒N‒C catalysts have attracted tremendous attention for their application to electrocatalysis. Nitrogen‐coordinated mononuclear metal moieties (MN x moities) are bio‐inspired active sites that are analogous to various metal‐porphyrin cofactors. Given that the functions of metal‐porphyrin cofactors are highly dependent on the local coordination environments around the mononuclear active site, engineering MN x active sites in heterogeneous M‒N‒C catalysts would provide an additional degree of freedom for boosting their electrocatalytic activity. This work presents a local coordination structure modification of FeN 4 moieties via morphological engineering of graphene support. Introducing highly wrinkled structure in graphene matrix induces nonplanar distortion of FeN 4 moieties, resulting in the modification of electronic structure of mononuclear Fe. Electrochemical analysis combined with first‐principles calculations reveal that enhanced electrocatalytic lithium polysulfide conversion, especially the Li 2 S redox step, is attributed to the local structure modified FeN 4 active sites, while increased specific surface area also contributes to improved performance at low C‐rates. Owing to the synergistic combination of atomic‐level modified FeN 4 active sites and morphological advantage of graphene support, Fe‒N‒C catalysts with wrinkled graphene morphology show superior lithium–sulfur battery performance at both low and high C‐rates (particularly 915.9 mAh g −1 at 5 C) with promising cycling stability.