Phosphine-free synthesis and shape evolution of MoSe2 nanoflowers for electrocatalytic hydrogen evolution reactions

Abstract

MoSe₂ represents important layered transition metal dichalcogenides (TMDs) that have high electrocatalytic activity in the hydrogen evolution reaction (HER). A key issue to achieve excellent electrochemical properties of MoSe₂ is to synthesize nanostructures that are composed of few-layered MoSe₂ with abundant exposure of active edge sites. Nanoflowers of layered materials are promising building blocks for photocatalysis due to their large specific surface area and a wealth of exposed edge sites. In this work, free-standing colloidal MoSe₂ nanoflowers, with a size of 250 nm, were synthesized by employing a quick and nontoxic phosphine-free solution-processing approach. Oleic acid (OA), 1-octadecene (ODE) and 1-octylamine (OLA) were primarily used as solvents to control the morphology of MoSe₂ nanostructures. Experimental results revealed that the shape evolution of MoSe₂ nanostructures started with a first fast precipitation of amorphous materials followed by crystallization of a few layers of nanosheets. The prepared MoSe₂ nanoflowers demonstrated excellent HER activities with low overpotentials and small Tafel slopes, and the chronopotentiometry responses revealed good stability, making them promising materials for the electrocatalytic HER.