Scalable manufacture of nearly pure-phase metallic MoS2 nanosheets.

Abstract

Metallic, two-dimensional molybdenum disulfide (MoS2) nanosheets show promise for energy storage and catalysis applications. However, current chemical exfoliation methods require more than 48 h to produce milligrams of material, and result in an impure mixture of metallic (1T/1T', approximately 50%-70%) and semiconducting (2H) phases. Here we demonstrate large-scale and rapid (>600 g h-1) production of nearly pure-phase metallic two-dimensional MoS2 nanosheets using microwave irradiation. Atomic-resolution imaging and X-ray photoelectron spectroscopy show nearly 100% metallic phase in the basal plane. This high purity leads to a large exchange current density (0.175 ± 0.030 mA cm-2) and low Tafel slopes (39-47 mV dec-1) for hydrogen evolution reaction. In supercapacitors and lithium-sulfur pouch-cell batteries, the resulting nanosheets enable a high volumetric capacitance of 753.0 ± 3.6 F cm-3 and a specific capacity of 1,245 ± 16 mAh g-1 (electrolyte-to-sulfur ratio, 2 µl mg-1), respectively. Our method provides a practical pathway for producing high-quality metallic two-dimensional materials for high-performance energy devices.