A structural study of size selected WSe2 nanoflakes prepared via liquid phase exfoliation: X-ray absorption to electrochemical application

Transition metal dichalcogenides (TMDs) have been recognised as a candidate material in many electrochemical applications including energy storage, and electrocatalyst. In the TMDs family, the molybdenum disulfide pro-duced via liquid phase exfoliation had received attracted attention for fabricating the electrode. This is due to a clear structural and electrochemical property shown in the literature. To further explore the applications of the electrode made from TMDs materials, the tungsten selenide (WSe2) with a variety of flake sizes, and its properties were produced through a traditional liquid phase exfoliation using iso-propanol/water as an exfoliation solvent. The cascade centrifugal techniques were then applied to obtain a finely-selected flake size of WSe2 for electro-chemical and physical chacterisation. In this work, we shed more light on the structural and electrocatalyst properties of the size selected WSe2. A variety of WSe2 flakes exhibit almost similar structure; however, we have found that the intensity of W L3-edge XANES spectra decreases with respect to the increase of flake dimension. This is due to the change in the electronic structure of those materials. The change directly affects the electro-catalytic performance in which, the tiny flake displayed an excellent catalytic property for hydrogen evolution reaction with the Tafel slope of 76.11 mV dec-1 and overpotential of-400 mV vs. RHE (at 10 mA cm-2). This work provides insight into the structural information, which should improve the understanding of TMDs ma-terials in various contexts, especially electrocatalyst and energy storage.