Lattice Strain Formation through Spin-Coupled Shells of MoS<inf>2</inf> on Mo<inf>2</inf>C for Bifunctional Oxygen Reduction and Oxygen Evolution Reaction Electrocatalysts

Abstract

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 E1/2 = 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.