Morphology-Controlled Electrocatalytic Performance of Two-Dimensional VSe2Nanoflakes for Hydrogen Evolution Reactions

Abstract

VSe2is a typical two-dimensional (2D) transition-metal dichalcogenide material with various physical properties, such as ultrahigh electrical conductivity, controversial magnetism, and active catalytic properties. However, controllable preparation of VSe22D structures poses many challenges, and their application has not yet been developed. Here, we controllably synthesize VSe22D flakes on highly oriented pyrolytic graphite (HOPG) using molecular beam epitaxy. By controlling the growth temperature and the evaporation rate of the source, we obtained various morphologies of VSe2flakes, including single- and multilayers with triangular and belt shapes. Compared with the triangular structures of the flakes, the one-dimensional nanobelt structures have a larger edge density and can provide more catalytic active sites. Hydrogen evolution reaction results indicate that the belt-shaped VSe2flakes exhibit superior catalytic performance. Due to the presence of plenty of edges, the overpotential of the belt-shaped VSe2is 543 mV at a current density of 1 mA/cm2, which is much lower than that in the triangular flakes. The VSe2flakes with a larger edge density are more conductive than the regular triangular flakes after loading metal atoms due to the efficient dispersion of the metal atoms. As a result, the multistructure of Co particle-decorated VSe2flakes achieves a high catalytic performance with 352 mV overpotential at a current density of 10 mA/cm2, demonstrating their potential applications in the catalyst field.