The Origin of MoS_2 Significantly Influences Its Performance for the Hydrogen Evolution Reaction due to Differences in Phase Purity

摘要

Molybdenum disulfide (MoS_2) 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 MoS_2. Here we test the electrochemical performance of MoS_2 obtained from seven sources and we show that these sources provide MoS_2 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 mAcm~(-2) for MoS_2 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-MoS_2, the use of the top-down approach would usually involve the application of commercially available MoS_2. These commercially available MoS_2 are rarely characterized for composition and phase purity. These key parameters are responsible for large variance of reported catalytic properties of MoS_2.