Hydrogen evolution at MoS2: rationalising the reaction mechanism and outlook for electrocatalyst development

MoS₂ has seen decades of research into enhancing its electrocatalytic activity towards the Hydrogen Evolution Reaction; however, consistently, the literature has been undecided and often contradictory on the true nature of its active sites. Herein, the understanding of MoS₂ active sites has been reviewed, collating chemical evidence across the literature using techniques such as XPS, Raman, and electrochemical studies to deduce a more complete picture of the origins of its catalytic activity. A seemingly contradictory literature landscape has been rationalised, concluding that the most accurate data appears to back sulphur defects, and thus low-coordinate Mo sites, as the active sites of interest, alongside demonstrating how parsing the literature in this way can help locate agreement where only contradiction was thought to reside. Following this, learning from the various techniques used in their elucidation is not only beneficial for future work on this material but also for electrocatalyst development as a whole.