Experimental and Theoretical Comparison of Potential-dependent Methylation on Chemically Exfoliated WS₂ and MoS₂

Abstract

Reductant-activated functionalization is shown to enhance the methylation of chemically exfoliated MoS₂ (ceMoS₂) and ceWS₂ by introducing excess negative charge to facilitate a nucleophilic attack reaction. Relative to methylation in the absence of a reductant, the reaction produces a twofold increase in coverage of ceWS₂, from 25 to 52% coverage per WS₂. However, at every potential, the methyl coverage on ceWS₂ was ∼20% lower than that on ceMoS₂. We applied grand canonical density functional theory to show that at constant potential, more negative charge is present on 1T′-MoS₂ than on 1T′-WS₂, making methylation both thermodynamically and kinetically more favorable for 1T′-MoS₂ than 1T′-WS₂. This effect was moderated when the reactions were compared at constant charge, emphasizing the importance of comparing the reactivity of materials at nominally identical electrode potentials.

Group Members

William A. Goddard III

Charles and Mary Ferkel Professor