<p>Friction is the central cause for about 1/3 of the primary energy dissipation, severely impacting the performance limits of micro and nanoscale mechanical devices. Especially in two-dimensional semiconductor devices, electronic friction energy dissipation becomes particularly pronounced. However, the dynamic mechanisms underlying electronic friction energy dissipation remain unclear due to the ultrafast timescales of electronic behavior. Here, the ultrafast dynamics of electronic friction energy dissipation in monolayer WS₂ is observed using femtosecond transient absorption spectroscopy. We find that friction exhibits a significant enhancement as the rate of electron energy dissipation increases. It is experimentally found to be closely related to the generation of atomic defects at the sliding interfaces. These defects capture electrons in picoseconds and provide a new energy dissipation channel, resulting in increased friction. This study reveals the dynamics of electronic friction energy dissipation, which is vital to understand the origin of friction and improve the performance of micro and nanoscale devices.</p>