Caution needs to be taken that the aforementioned ex situ characterizations fail to capture the kinetics of structural evolution and to unravel the true reaction mechanisms due to their limited spatial/time resolutions. Moreover, sulfide compounds generally suffer from irreversible surface oxidation during sample handling and transportation processes. The critical question "What is the role of sulphur-oxygen exchange in the catalytic process?" remains to be explored. In this sense, time-resolved monitoring based on advanced operando characterizations is far more suitable to access the real catalytically active centers and to capture the active species at the atomic level.