Fig. 6

Density functional theory results and electrode reaction mechanism. a Optimized structures of Na2S4 cluster on carbon-supported Co6 cluster, and b on carbon support. Purple: Na; yellow: S; blue: Co; gray: C; white: H. c Energy profiles of Na2S4 adsorption on carbon-supported Co6 cluster (in blue) and carbon support (in red). d, e Schematic illustrations of electrode reaction mechanism of atomic cobalt-decorated hollow carbon sulfur host (S@Con-HC) and hollow carbon hosting sulfur (S@HC), respectively