The Origin of MoS₂ Significantly Influences Its Performance for the Hydrogen Evolution Reaction due to Differences in...

Molybdenum disulfide (MoS₂ ) is at the forefront of materials research. It shows great promise for electrochemical applications, especially for hydrogen evolution reaction (HER) catalysis. There is a significant discrepancy in the literature on the reported catalytic activity for HER catalysis on MoS₂ . Here we test the electrochemical performance of MoS₂ obtained from seven sources and we show that these sources provide MoS₂ of various phase purity (2H and 3R, and their mixtures) and composition, which is responsible for their different electrochemical properties. The overpotentials for HER at -10 mA cm^-2 for MoS₂ from seven different sources range from -0.59 V to -0.78 V vs. reversible hydrogen electrode (RHE). This is of very high importance as with much interest in 2D-MoS₂ , the use of the top-down approach would usually involve the application of commercially available MoS₂ . These commercially available MoS₂ are rarely characterized for composition and phase purity. These key parameters are responsible for large variance of reported catalytic properties of MoS₂ .