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

The sluggish redox kinetics of Na 2 S x /Na 2 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 2 S 2 –Na 2 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 –2, and an impressively power density of 119.3 mW cm –2, along with a very low capacity decay rate of 0.0146% per cycle over 1000 cycles.