Synthesis and hydrogen-evolution activity of tungsten selenide thin films deposited on tungsten foils

Thin films of WSe₂ have been deposited onto a conductive substrate (tungsten foil) using a relatively simple chemical-vapor-transport technique. X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, X-ray powder diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy indicated that the films consisted of micron-sized single crystals of WSe₂ that were oriented perpendicular to the surface of the tungsten foil substrate. Linear sweep voltammetry was used to assess the ability of the WSe₂ films to catalyze the hydrogen-evolution reaction and chronopotentiometry was used to gauge the temporal stability of the catalytic performance of the films under cathodic conditions. A 350 mV overpotential (η) was required to drive the hydrogen-evolution reaction at a current density of -10 mA cm^-2 in aqueous 0.5 M H₂SO₄, representing a significant improvement in catalytic performance relative to the behavior of macroscopic WSe₂ single crystals. The WSe₂ thin films were relatively stable under catalytic conditions, with the overpotential changing by only ∼10 mV after one hour and exhibiting an additional change of ∼5 mV after another hour of operation.