Other than for the HER, we have also implemented ex situ XAS to characterize L-CoS after the OER systematically. As We further conducted ex situ XPS and in situ Raman characterizations (Figures ) to shed more light on the surface environments of L-CoS before and after the HER/OER in different media. The results again unravel distinct surface kinetics between alkaline and acidic conditions. High-resolution Co 2p, O 1s, and S 2p XP spectra confirm that Co-S bonds dominate the surface of fresh-prepared L-CoS. This coordination can be preserved after L-CoS catalyzed the HER in 0.5 M H2SO4. Under alkaline conditions, either for the HER or OER, the post-catalytic L-CoS exhibits an O-rich surface environment. In situ Raman characterizations corroborate that the surface environments of L-CoS remain almost unchanged during the acidic HER but experience local structural changes through sulfur-oxygen exchange reactions during the alkaline HER and OER (see discussion details in Figure ).