Effects of Molybdenum to Sulfur Ratio in the Synthesis of Molybdenum Disulfide as an Electrocatalyst for Hydrogen Evolution Reaction

Electrochemical water splitting is a promising method for sustainable hydrogen production with low carbon emissions. Molybdenum disulfide (MoS₂), a two-dimensional transition metal dichalcogenide (TMD), has gained attention as a cost-effective alternative to noble metal-based electrocatalysts. This study investigates the effect of precursor molar ratios on the hydrogen evolution reaction (HER) performance of MoS₂ synthesized on 3D conductive carbon cloth using the hydrothermal method. MoS₂ was synthesized with varying molybdenum-to-sulfur molar ratios (1:4, 1:2, and 1:1), and characterization confirmed the formation of the 2H-MoS₂ phase, with an additional α-MoO₃ phase. Among the samples, MoS₂-14 (1:4 ratio) exhibited the highest HER activity, with a low onset potential of 155 mV, and a Tafel slope of 58 mV/dec. MoS₂-14 had the largest electrochemical active surface area (C dl = 251 mF/cm²) and the lowest charge transfer resistance (R ct = 1.28 Ω), indicating superior conductivity and catalytic performance. Morphological analysis showed that MoS₂-14 had a more amorphous structure further enhancing its HER efficiency. These findings demonstrate that precursor molar ratios significantly impact the structural, morphological and electrocatalytic properties of MoS₂, with a 1:4 molybdenum-to-sulfur ratio offering optimal performance, providing valuable insights for rational design of high-performance MoS₂-based electrocatalysts