Operando infrared spectroscopy in combination with a kinetic study is used to elucidate the role of potassium on the conversion of carbon monoxide over K-promoted MoS2 catalysts. More specifically, the initial break-in transient has been studied in detail. Stabilization of reaction intermediates, and effect of promoter on the intrinsic properties of MoS2 are discussed. Adsorbed alkoxy species were found to play an important intermediate role in the syngas to alcohol route, and it was found that potassium stabilizes these species. Moreover, the electronic properties of MoS2 change upon promotion, thereby allowing for a relatively easier activation of the CO molecule and a reduced hydrogenation activity toward alkanes.