Colloidal synthesis of MoSe2 nanonetworks and nanoflowers with efficient electrocatalytic hydrogen-evolution activity

MoSe 2 represents an important layered transition metal dichalcogenides (LTMDs) that have high electrocatalytic activity in hydrogen evolution reaction (HER). A key issue to achieve excellent electrochemical properties of MoSe 2 is to synthesize nanostructures that are composed of few-layer MoSe 2 with maximized exposure of active edge sites. In this study, we report the synthesis of MoSe 2 nanostructures with network-like and flower-like morphologies via an organic solution approach that utilizes molybdenum hexacarbonyl as Mo precursor and Se powders as Se source. The prepared MoSe 2 nanostructures consist of few-layer ultrathin nanosheets which can have different orientations. Depending on the volume ratio of oleylamine to oleic acid , the arrangement of ultrathin MoSe 2 nanosheets is adjustable and can form porous network-like or discrete flower-like nanostructure which has large specific surface area and a wealth of exposed edge sites. Excellent HER activities with low overpotentials, small Tafel slopes and long-term durability are observed on the as-synthesized MoSe 2 nanostructures. The acetic acid-washing step that may effectively remove the organic molecules capped on MoSe 2 surfaces is also found to be efficient in improving the HER activity of the synthesized MoSe 2 nanostructures.