Modulating the HER-overpotential at the interface of nanostructured MoS₂ synthesized via hydrothermal route: An in-situ mass-spectroscopy approach

Hydrogen evolution reaction (HER) using a new exfoliated in-situ and amine-functionalized MoS₂ prepared via a hydrothermal method, assisted with sonication treatment, is reported. Techniques such as XRD, RAMAN, FTIR, XPS, N₂-physisorption and HRTEM, confirmed the production of different MoS₂ samples. Depending on the material, the overpotential for HER was modified; this was also observed for selected samples concerning the acid solution (HNO₃, H₂SO₄, HCl, and HClO₄), as demonstrated using linear sweep voltammetry and Tafel approach. The faradic current observed was in the order I_HCLO4 > I_HCl > I_H2SO4 > I_HNO3; whereas the charge-transfer resistance (ohms) was R_HNO3 (29816) > R_H2SO4 (311.5) > R_HCl (167.7) > R_HCLO4 (167.7). It was found (using DEMS) that protons (m/z = 1) modulated the generation of hydrogen (m/z = 2) at H₂SO₄, HCl, and HClO₄ solutions; conversely, at HNO₃ electrolyte, the reduction of NO₃⁻ to nitrogen was activated, delaying HER-kinetic.