Hierarchical spheres constructed by defect-rich MoS₂/carbon nanosheets for efficient electrocatalytic hydrogen evolution

Highlights: • Defect-rich MoS₂/carbon hierarchical spheres with more active sites were prepared by simple micro-emulsion method. • The C–MoS₂ hierarchical spheres exhibited a low onset potential of −103 mV (vs. RHE) with a Tafel slope of 56.1 mV dec⁻¹. • The "inverted molybdenum reaction" might provide a novel method to regulate the catalytic sites of MoS₂. Highly active and stable MoS₂/carbon hierarchical spheres with abundant active edge sites were fabricated by a simple micro-emulsion procedure where PVP was used as the carbon source, and carbon disulfide as the sulfur source and oil phase in micro-emulsion to control the morphology of MoS₂. Hierarchical spheres of MoS₂/carbon with a diameter of ca. 500 nm were obtained and characterized by scanning and transmission electron microscopic measurements. With a high electrochemically accessible surface area and defect-rich MoS₂ nanosheets, the MoS₂/carbon hierarchical spheres exhibited an excellent electrocatalytic activity for hydrogen evolution reaction with a low onset potential of −103 mV (vs. RHE), small Tafel of 56.1 mV dec⁻¹, as well as extraordinary catalytic stability. The results were accounted for by the "inverted molybdenum reaction" that served as a novel way of regulating Mo catalytic sites of MoS₂ electrocatalysts.