Large Scale Manufacture of Phase Pure Two-Dimensional Metallic MoS2 Nanosheets

TL;DR

This paper presents a rapid, large-scale microwave-assisted method for producing pure metallic 2D MoS2 nanosheets, significantly improving phase purity and enabling high-performance energy storage and catalysis applications.

Contribution

The authors develop a microwave irradiation technique for large-scale, rapid synthesis of phase-pure metallic 2D MoS2 nanosheets, overcoming limitations of existing methods.

Findings

Achieved >600 g/h production rate of pure metallic 2D MoS2 nanosheets.

Demonstrated record-high volumetric capacitance and specific capacity in energy devices.

Confirmed near 100% metallic phase with atomic resolution imaging and spectroscopy.

Abstract

Metallic monolayered [or two - dimensional (2D)] MoS2 nanosheets show tremendous promise for energy storage and catalysis applications. However, state-of-the-art chemical exfoliation methods require > 48 hours to produce milligrams of metallic 2D MoS2. Further, chemically exfoliated MoS2 nanosheets are a mixture of metallic (1T or 1T prime 50% to 70%) and semiconducting (2H 30% to 50%) phases. Here, we demonstrate large-scale and rapid (>600 grams per hour) production of purely metallic phase 2D MoS2 (and WS2, MoSe2) nanosheets using microwave irradiation. Atomic resolution imaging shows 1T or 1T prime metallic phase in basal plane - consistent with close to 100% metallic phase concentration measured by X-ray photoelectron spectroscopy. The high 1T phase concentration results in the highest exchange current density of 0.175 plus-minus 0.03 mA cm-2 and among the lowest Tafel slopes (39 - 43 mV dec-1) measured to date for the hydrogen evolution reaction. In supercapacitors and lithium-sulfur pouch cell batteries, record-high volumetric capacitance of 753 plus-minus 3.6 F cm-3 and specific capacity of 1245 plus-minus 16 mAh g-1 (at exceptionally low electrolyte to sulfur ratio = 2 microlitre g-1), respectively, are obtained. Our method provides a practical pathway for producing high quality purely metallic phase 2D materials for high performance energy devices.