Tailoring a Transition Metal Dual-Atom Catalyst via a Screening Descriptor in Li-S Batteries

The adsorption-conversion paradigm of polysulfides during the sulfur reduction reaction (SRR) is appealing to tackle the shuttle effect in Li-S batteries, especially based upon atomically dispersed electrocatalysts. However, mechanistic insights into such catalytic systems remain ambiguous, limiting the understanding of sulfur electrochemistry and retarding the rational design of available catalysts. Herein, we systematically explore the polysulfide adsorption-conversion essence via a geminal-atom model system to understand the catalyst roles toward an expedited SRR. A descriptor involving an electronic structure index (I_ES) and electron affinity index (I_EA) is proposed, considering the geometric and electronic dictation within a Fe/M (M: 3d-block transition metal) atomic ensemble. With the aid of theoretical computation, we managed to identify the SRR thermodynamic/kinetic trends of Fe/M moieties. Guided by these findings, we in target design a Fe/V-NC dual-atom catalyst, which harvests a minimum I_ES and maximum I_EA, accordingly demonstrating enhanced polysulfide adsorption-conversion and improved full-cell performances. Such a consistency between a computational descriptor and experimental evidence highlights the importance of an atomic catalyst screen and selection for Li-S batteries.