The Substrate Morphology Effect for Sulfur-Rich Amorphous Molybdenum Sulfide for Electrochemical Hydrogen Evolution Reaction
Marina Medina, Patricia Gon Corradini, Juliana Ferreira de Brito, Hugo L. S. Santos, Lúcia H. Mascaro
Abstract
Amorphous molybdenum sulfide (MoS x ) is a promising material for hydrogen evolution reaction (HER) due to its nearly zero hydrogen adsorption free energy at the sulfur (S) edge-sites. To prepare more efficient MoS x -based electrocatalysts, new attempts are required to increase the exposure of the MoS x lateral size and, therefore, increase the S atom’s contents. The majority of studies reported in the literature investigate MoS x over conductive substrates. However, MoS x can be electrodeposited over inexpensive and chemically stable platforms, such as semiconductors. This work presents the semiconductor substrate morphology effect for prepared sulfur-rich MoS x for electrochemical hydrogen evolution reaction. The electrodes are prepared by cyclic voltammetry with 25 cycles over TiO 2 film and TiO 2 nanotubes (TiO 2 NT) substrates. The MoS x deposit on TiO 2 NT presents an increase S atoms contents and exhibits excellent HER activity with a low overpotential of 93 ± 7.5 mV to reach −10 mA cm −2 and a higher exchange current density equal to 91 μ A cm −2 , and a smaller Tafel slope of 43 mV dec −1 .