Dense MoS2/CoS2 Heterointerfaces with Optimized Electronic Structure for Efficient Alkaline Hydrogen Evolution Reaction

Molybdenum disulfide (MoS2) is considered as a promising electrochemical catalyst for hydrogen generation. However, insufficient exposed active sites and poor conductivity severely impede its large-scale applications. Herein, the heterogeneous MoS2/CoS2 electrocatalyst was grown in situ on carbon cloth. The synergistic interaction between CoS2 and MoS2 occurring at the dense heterointerfaces grants the hybrid higher catalytic activities than single components, thereby speeding up hydrogen production rates. After annealing, the composite exhibits an ultralow overpotential of 67 mV at 10 mA cm–2 and a small Tafel slope of 70 mV dec–1 in 1 M KOH due to the improved conductivity and intimate connection between MoS2 and CoS2. Furthermore, it maintains an excellent cycle durability of 65 h without obvious attenuation at 20 mA cm–2. In-situ shielding tests reveal the main active sites coming from MoS2 rather than CoS2. On the basis of experimental measurements and theoretical calculations, CoS2 should work as the electron donor in the HER process and improve not only H2O adsorption but also H2 emission behaviors. The excellent hydrogen evolution performance of annealed-MoS2/CoS2/CC composite indicates that the present design is a prospective option for developing low-cost and efficient HER electrocatalysts in alkaline electrolytes.