Lattice Strain Formation through Spin-Coupled Shells of MoS₂ on Mo₂C for Bifunctional Oxygen Reduction and Oxygen Evolution Reaction Electrocatalysts

Identifying effective means to improve the electrocatalytic performance of transition metal dichalcogenides in alkaline electrolytes is a significant challenge. Herein, an advanced electrocatalyst possessing shells of molybdenum disulfide (MoS₂) on molybdenum carbide (Mo₂C) for efficient electrocatalytic activity in alkaline electrolytes is reported. The strained sheets of curved MoS₂ surround the surface of Mo₂C, turning the inactive basal planes of MoS₂ into highly active electrocatalytic sites in the alkaline electrolyte. The van der Waals layers, which even possess van der Waals epitaxy along (100) facets of MoS₂ and Mo₂C, enhance the spin coupling between MoS₂ and Mo₂C, providing an easy electron transfer path for excellent electrocatalytic activity in alkaline electrolytes and solving the stability issue. In addition, it is found that curved MoS₂ sheets on Mo₂C show 3.45% tensile strain in the lattice, producing excellent catalytic activity for both oxygen reduction reaction (ORR) (with E_½ = 0.60 V vs RHE) and oxygen evolution reaction (OER) (overpotential = 1.51 V vs RHE at 10 mA cm^-2) with 60 times higher electrochemical active area than pristine MoS₂. The unique structure and synthesis route outlined here provide a novel and efficient approach toward designing highly active, durable, and cost-effective ORR and OER electrocatalysts.