Efficient Heterojunction Electrocatalysts for Polysulfide Conversion in Li-S Batteries via Dual-Geometric...

Constructing electrocatalysts with heterostructures has emerged as an efficient approach to cooperatively catalyze the conversion of lithium polysulfides (LiPSs) in lithium-sulfur (Li-S) batteries. However, it remains a formidable challenge to fundamentally understand the structure-activity relationship between the interfacial configuration and electrocatalytic performance, which is crucial for the rational design of electrocatalysts with heterojunctions. Herein, by leveraging molybdenum carbides (Mo_xC) with tunable crystal structures as model electrocatalysts, we systematically investigated the geometric-configuration-dependent catalytic activity for LiPS conversion. Experimental analyses confirmed that the cubic MoC with octahedrally coordinated Mo atoms (Mo_oct) is easily passivated because of its robust LiPS affinity, while the hexagonal Mo₂C with triangularly coordinated Mo atoms (Mo_tri) functions better in improving the interfacial charge transfer. Accordingly, the constructed heterointerfaces integrated with dual-geometric coordination endow MoC/Mo₂C with moderate LiPS adsorption and favorable charge transfer kinetics to cooperatively catalyze LiPS conversion. Benefiting from these advantages, the Li-S batteries assembled with MoC/Mo₂C demonstrate superior reversible specific capacities and cycling durability. This work highlights the critical role of interfacial geometric coordination in heterojunctions for LiPS retention and catalysis, offering a guiding approach for elevating the activity of heterojunction electrocatalysts.