Conducting MoS₂ Nanosheets as Catalysts for Hydrogen Evolution Reaction

TLDR

The study reports chemically exfoliated MoS₂ nanosheets rich in metallic 1T phase produced via a solvent‑free intercalation method. The authors prepared the nanosheets by solvent‑free intercalation, then neutralized surface charges to yield highly conducting 1T MoS₂ that shows excellent hydrogen evolution activity with a Tafel slope of 40 mV dec⁻¹. Partial oxidation suppresses the activity of 2H MoS₂ but leaves 1T MoS₂ unchanged, indicating that 1T edges are not the main active sites, while enhancing 2H conductivity with carbon nanotubes restores its activity.

Abstract

We report chemically exfoliated MoS2 nanosheets with a very high concentration of metallic 1T phase using a solvent free intercalation method. After removing the excess of negative charges from the surface of the nanosheets, highly conducting 1T phase MoS2 nanosheets exhibit excellent catalytic activity toward the evolution of hydrogen with a notably low Tafel slope of 40 mV/dec. By partially oxidizing MoS2, we found that the activity of 2H MoS2 is significantly reduced after oxidation, consistent with edge oxidation. On the other hand, 1T MoS2 remains unaffected after oxidation, suggesting that edges of the nanosheets are not the main active sites. The importance of electrical conductivity of the two phases on the hydrogen evolution reaction activity has been further confirmed by using carbon nanotubes to increase the conductivity of 2H MoS2.