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.