The structural reversibility of the active S-Co-Co-S moieties was further elucidated by performing time-dependent XAS characterization of L-CoS after the electrolysis. The results reveal that after the electrolysis the active S-Co-Co-S moieties can dynamically convert into the S-Co-O-Co1-S moieties again (discussion and details in Figures ). We further investigated the pH-dependent HER performance of L-CoS at pH 12~ 14. Combination of the obtained pH-dependent results with KSCN poisoning experiments reveals that the generation of S-Co-Co-S moieties is crucial for the alkaline HER of L-CoS (discussion and details in Figure ). Taking into account all information from Raman, XPS, and operando XAS, an overall electrochemically driven restructuring process is depicted in Figure , whereas the release of H2 occurs atop the active S-Co-Co-S moieties. Importantly, due to the switching of catalytically active sites and the presence of different HER kinetics, namely (i) optimization of Co-S-Co moieties for triggering the acidic HER and (ii) multi-step restructuring into S-Co-Co-S moieties coupled with the participation of water dissociation for the alkaline HER, L-CoS exhibits a distinct HER performance under acidic and alkaline conditions, respectively (Figures ).