MoSe<sub>2</sub> Dispersed in Stabilizing Surfactant Media: Effect of the Surfactant Type and Concentration on Electron Transfer and Catalytic Properties

Layered transition metal dichalcogenides (TMDs) have gained attention from the scientific community because of their extended range of applications. Molybdenum diselenide (MoSe<sub>2</sub>) has been proven to be an efficient catalyst for the hydrogen evolution reaction (HER), having implications in the research of new catalysts for clean energy production. One way to produce large quantities of these materials involves the use of surfactants for liquid exfoliation. Herein, we investigate the effects of cationic, anionic, and nonionic surfactants within a concentration range on the heterogeneous electron transfer rates, electrocatalytic efficiency toward the HER of MoSe<sub>2</sub>, and on the stability of the dispersions. We found that surfactants can have a detrimental effect on the electrocatalytic properties of the material when used above a concentration threshold. In some cases, high surfactant levels also had a negative effect on the stability of the material. This report serves to gain an understanding on how the way TMDs are prepared, processed, and stabilized can have dramatic effects on their efficiency toward HER, one of their most popular applications, and how choosing the appropriate surfactant type and concentration is crucial to gain in stability without compromising the intrinsic properties of the material.