Plasma-Induced Fabrication and Straining of MoS₂ Films for the Hydrogen Evolution Reaction

We present a novel plasma conversion process to fabricate strained MoS₂ films for the hydrogen evolution reaction (HER). Materials characterization of the initially converted film shows a rippled surface morphology that consequently contains in-plane and out-of-plane tensile strain. Smoothening of the films and relaxation of the strain are demonstrated by postsynthesis thermal treatment. Only negligible sulfur vacancies are detected in both the initially converted and thermally treated films. Electrochemical characterization shows that our plasma-converted, strained MoS₂ films are as intrinsically HER active as those produced by generating sulfur vacancies via postsynthesis plasma treatment. The reduced number of processing steps and direct, transfer-free growth enable a simple and scalable approach for fabricating MoS₂-based catalysts.