Electrochemical Modulation of MoS2 Structures to Boost Hydrogen Evolution Reaction Efficiency

The use of molybdenum disulfide (MoS₂) as a non-noble metal electrocatalyst for the hydrogen evolution reaction (HER) has gained significant attention due to its affordability and the ease of modifying factors such as voltage, current, duration, and the composition and concentration of the electrolyte solution using electrodeposition techniques. To increase the number of active sites on the surface of MoS₂, fine nanoscale tailoring of the crystalline phase is necessary. This can be accomplished using electrochemical phase formation. In this study, four types of MoS₂ nanoparticles are successfully electrodeposited on copper foil substrates using a mixture of Na₂MoO₄ and Na₂S electrolytes, namely fine nodular MoS₂ (FNMoS₂), small sheet MoS₂ (SSMoS₂), highly porous MoS₂ (HPMoS₂), and low porous MoS₂ (LPMoS₂), with nanoparticles of FNMoS₂, SSMoS₂, HPMoS₂, and LPMoS₂ being produced at potentials of −0.9, −1.0, −1.1, and −1.2, respectively. The electrochemical performance of these nanoparticles on HER is carefully investigated using techniques such as high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and energy dispersive spectroscopy. Linear sweep voltammetry, Tafel plot analysis, and electrochemical impedance spectroscopy are used to study the electrocatalytic performance of HER in a 0.5 M KOH electrolyte. HPMoS₂ electrodeposited at −1.1 V for 200 s had a HER current density of 10 mA cm⁻² at η = −270 mV and a Tafel slope (vs RHE) of 35.8 mV/dec, lower than that of FNMoS₂, SSMoS₂, and LPMoS₂. These results have significant implications for the development of low cost, affordable, and environmentally friendly electrochemical methods of producing hydrogen, and pave the way for further research in this field.