Effects of molybdenum to sulfur ratio in the synthesis of molybdenum disulfide as an electrocatalyst for hydrogen evolution reaction

Abstract Electrochemical water splitting is a promising method for sustainable hydrogen production with low carbon emissions. Molybdenum disulfide (MoS 2 ), a two-dimensional transition metal dichalcogenide, 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 MoS 2 synthesized on 3D conductive carbon cloth using the hydrothermal method. MoS 2 was synthesized with varying molybdenum-to-sulfur molar ratios (1:4, 1:2, and 1:1), and characterization confirmed the formation of the 2H-MoS 2 phase, with an additional α -MoO 3 phase. Among the samples, MoS 2 -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 −1 . MoS 2 -14 had the largest electrochemical active surface area ( C dl = 251 mF cm −2 ) and the lowest charge transfer resistance ( R ct = 1.28 Ω), indicating superior conductivity and catalytic performance. Morphological analysis showed that MoS 2 -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 MoS 2 , with a 1:4 molybdenum-to-sulfur ratio offering optimal performance, providing valuable insights for rational design of high-performance MoS 2 -based electrocatalysts.