support is verified by an apparent redshift from 465 to 453 cm -1 in the F2g peak of Pd1/CeO2 in the Raman spectra, originating from the defect-sensitive, symmetrical stretching vibration of O 2-around Ce 4+ . Notably, the F2g peak suddenly blueshifts to 461 cm -1 upon RT-CO treatment in 5 mins, which is attributed to rapid oxygen extraction and nucleation of PdOx clusters at the Pd/CeO2 interface. In separate work, a broad peak attributed to an I-H vibration band at 1460 cm -1 is seen in the in situ Raman for single-atom iodine stabilized on nickel hydroxide when the potential was more negative than the thermodynamic potential of HER. Finally, combining two (or more) operando methods is particularly powerful for an in-depth understanding of dynamic structural evolution, such as combined XAS/DRIFTS/NAP-XPS, XAS/TEM, , etc. Theoretical calculations based on DFT, MD, or finite element analysis also provide vital structural features on dynamic processes, which may not be accessible via operando techniques. A good example lies in the geminal-atom catalysis for the well-designed combination of experimental and theoretical approaches.