Formation of thin catalytic WSex layer on graphite electrodes for activation of hydrogen evolution reaction in aqueous acid

Abstract

The possibility of obtaining new relatively inexpensive electrode materials to provide enhanced efficiency of hydrogen evolution reaction (HER) in an aqueous acid solution was investigated. For this purpose, the surface properties of cathodes made of microcrystalline graphite were modified by pulsed laser deposition of thin films of WSe_x. The structure, morphology, and chemical composition of the thin film coatings were varied by changing the deposition conditions and subsequent heat treatment. The compact and dense structure of the film in an amorphous and crystalline state did not result in a marked positive impact on the character of the HER process, which was investigated in 0.5 M H₂SO₄ solution at room temperature. Formation of thin layers consisting of nanocrystalline “petals” WSe₂ caused an increase in cathodic current by more than 6 times (at a voltage of–150 mV), and the Tafel slope of the voltage vs. current curve was reduced by about 80 mV/dec. The conditions were determined to produce on the surface of the graphite cathode a high density of new catalytically active sites that formed on edges of molecular planes forming a layered structure characteristic of WSe₂ nanocrystals.