Optimizing Microenvironment of Asymmetric N,S‐Coordinated Single‐Atom Fe via Axial Fifth Coordination toward Efficient Oxygen Electroreduction

Abstract

Single‐atom catalysts (SACs) are attractive candidates for oxygen reduction reaction (ORR). The catalytic performances of SACs are mainly determined by the surrounding microenvironment of single metal sites. Microenvironment engineering of SACs and understanding of the structure–activity relationship is critical, which remains challenging. Herein, a self‐sacrificing strategy is developed to synthesize asymmetric N,S‐coordinated single‐atom Fe with axial fifth hydroxy (OH) coordination (Fe−N3S1OH) embedded in N,S codoped porous carbon nanospheres (FeN/SC). Such unique penta‐coordination microenvironment is determined by cutting‐edge techonologies aiding of systematic simulations. The as‐obtained FeN/SC exhibits superior catalytic ORR activity, and showcases a half‐wave potential of 0.882 V surpassing the benchmark Pt/C. Moreover, theoretical calculations confirmed the axial OH in FeN3S1OH can optimize 3d orbitals of Fe center to strengthen O2 adsorption and enhance O2 activation on Fe site, thus reducing the ORR barrier and accelerating ORR dynamics. Furthermore, FeN/SC containing H2O2 fuel cell performs a high peak power density of 512 mW cm−2, and FeN/SC based Znair batteries show the peak power density of 203 and 49 mW cm−2 in liquid and flexible all‐solid‐state configurations, respectively. This study offers a new platform for fundamentally understand the axial fifth coordination in asymmetrical planar single‐atom metal sites for electrocatalysis.

Simultaneously Integrate Iron Single Atom and Nanocluster Triggered Tandem Effect for Boosting Oxygen Electroreduction

“…To date, two general pathways are developed to optimize the electronic structure of FeN 4 active sites. One is directly replacing partial coordinated N atoms in FeN 4 with other heteroatoms (e.g., S [ 24 ] and P [ 25 ] ) to construct an asymmetrically coordinated Fe active site. The other strategy is utilizing the long‐range interactions to modify the electronic structure of the FeN 4 active center.…”

Theoretical study of the effect of coordination environment on the activity of metal macrocyclic complexes as electrocatalysts for oxygen reduction

“…Meanwhile, the energy changes of the PDSs, namely desorption of ∗OH, decrease to 0.50 and 0.36 eV on Fe- and Co-complexes, related to improved oxygen reduction performance. In experiment, it has been also reported that the ultimate ORR performance is achieved by constructing a single atom catalyst with coordination number of five ( Han et al., 2018 ; Li et al., 2022 ). In contrast, Ni 2+ cation possesses d 8 electron configuration.…”

Experimental and Theoretical Advances on Single Atom and Atomic Cluster‐Decorated Low‐Dimensional Platforms towards Superior Electrocatalysts

“…The coordination environment of single atom and atomic cluster on LD materials can significantly alter the electronic properties of the active sites. Tuning the coordination environment of single atoms to achieve high activity and selectivity is becoming a hot topic in both theoretical [187,188] and experimental [189,190] parts. Ha et al employed the high-throughput computation and machine learning methods to explore the stability and activity of TM supported on nitrogen-doped graphene (TM-GN) for HER, OER, and ORR.…”