To completely eliminate S 0 , the MoS2 prepared in the presence of H2 was separated from the supernatant solution, dispersed in 50 mL of 1 M Na2S in a sealed glass vial (100 mL), sonicated for 1 hour, and rinsed with deaerated Milli-Q water on a PTFE membrane filter (pore size = 0.2 μm) with the eluate evacuated under vacuum. The rinsed MoS2 was dried under vacuum, stored inside an anaerobic chamber, and used for the methanethiol synthesis experiment.