Mn-Co Dual-Metal Single-Atom Catalytic Sites for Boosted Redox Kinetics in Aqueous Polysulfide/Ferricyanide Flow Batteries.

Zhang, Hong; Feng, Ziyu; Ding, Tianhang; Song, Bin; Lu, Ke; Yang, Chun Cheng; Jiang, Qing · Nano Lett · 2025

basic_science · Level V

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Abstract

The sluggish redox kinetics of Na<sub>2</sub>S<sub><i>x</i></sub>/Na<sub>2</sub>S and the uncontrollable crossover of polysulfides often result in limited reutilization of active materials, hindering the practical scalable application of polysulfide/ferricyanide flow batteries. By leveraging the bidirectional manipulation of redox kinetics of active species, diatomic Mn and Co sites anchored on nitrogen-doped carbon encapsulated graphite carbon felt was prepared. And a progressive "optimized d-band model" was revealed, in which the tunable d-band centers of Mn and Co were, respectively, regulated to enable facile electron extraction and injection during the Na<sub>2</sub>S<sub>2</sub>-Na<sub>2</sub>S redox; then the synergistic catalytic effect renders the matrix with bidirectional acceleration. The electrocatalytic capability was also witnessed within the catholyte chamber. The assembled polysulfide-ferricyanide flow cell exhibits high energy efficiency of 76.4% at 20 mA cm<sup>-2</sup>, and an impressively power density of 119.3 mW cm<sup>-2</sup>, along with a very low capacity decay rate of 0.0146% per cycle over 1000 cycles.