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

Abstract

Thin films of WSe_2 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 WSe_2 that were oriented perpendicular to the surface of the tungsten foil substrate. Linear sweep voltammetry was used to assess the ability of the WSe_2 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 H_2SO_4, representing a significant improvement in catalytic performance relative to the behavior of macroscopic WSe_2 single crystals. The WSe_2 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 ∼5mV after another hour of operation.