Liquid Phase Exfoliation of MoS₂ Assisted by Formamide Solvothermal Treatment and Enhanced Electrocatalytic Activity Based on (H₃Mo₁₂O₄₀P/MoS₂)_n Multilayer Structure

Abstract

In this work, MoS2 nanosheets were obtained successfully using the liquid phase exfoliation method assisted by formamide solvothermal treatment. The exfoliation efficiency in N-methyl-2-pyrrolidone (NMP) was enhanced by the synergetic effect of easier intercalation of polar solvent and higher repulsive force of the treated bulk MoS2. The exfoliated MoS2 nanosheets were assembled alternately with H3Mo12O40P (PMo12) into a multilayer heterostructure by the layer-by-layer (LBL) method, in which PMo12 with high electron mobility bridges the adjacent catalytically active MoS2 layers. Based on the heterostructure, the electrocatalytic performance for hydrogen evolution was substantially enhanced over multilayer MoS2 nanosheets alone. Moreover, it was found that the electrocatalytic performance was influenced by the layer number, indicating that an optimum balance between the mass transfer (MoS2 layer) and electron conductivity (PMo12 layer) was needed for the construction of efficient electrocatalysts. In addition, the electrocatalytic performance of the multilayers (MoS2)n and (PMo12/MoS2)n could be improved by oxygen plasma treatment, which might be ascribed to the increased number of edges and defects in MoS2 nanosheets. This work not only provides a facile method to exfoliate MoS2 with higher efficiency, but also offers a feasible strategy to build up high-performance electrocatalysts by rationally assembling nanosheets and polyoxometalate species at the nanoscale level.