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

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. Origin is important to HER: A comparison study was carried out on various commercial and natural MoS2 samples, highlighting numerous differences in phase composition, purity, and particle size. These differences were evaluated for their impact on the rather variable performances the MoS2 samples showed as a catalyst for the hydrogen evolution reaction.