Tandem Co–O dual sites on halloysite with promoted reaction kinetics for sulfur reduction

Facilitating sulfur reduction reaction (SRR) is a promising pathway to tackle the polysulfide shuttle effect and enhance the electrochemical performance of lithium-sulfur (Li-S) batteries. Catalysts with a solo active site can reduce a reaction barrier of a certain transition-intermediate, but the linear scaling relationship between multi-intermediates still obstructs overall SRR. Herein, we construct tandem Co–O dual sites with accelerating SRR kinetics by loading highly dispersed cobalt sulfide clusters on halloysite. This catalyst features Co with upshifted d -orbital and O with downshifted p-orbital, which cooperatively adsorb long-chain polysulfide and dissociate an S–S bond, thus achieving both optimal adsorption–desorption strength and reduced conversion energy barrier of multi-intermediates in SRR. The Li-S coin batteries using the electrocatalyst endows a high specific capacity of 1224.3 mAh g −1 at 0.2 C after 200 cycles, and enhances cycling stability with a low-capacity decay rate of 0.03% per cycle at 1 C after 1000 cycles. Moreover, the strategy of the tandem Co–O dual sites is further verified in a practical Li-S pouch battery that realizes 1014.1 mAh g −1 for 100 cycles, which opens up a novel avenue for designing electrocatalysts to accelerate multi-step reactions.