The electron hole state (O hole) of oxygen is considered the key to balance the high specific capacity of positive electrode and high cycle stability. However, there is a great controversy about whether O hole is stable during the operation of electrode materials. This study combines the high resolution ability of soft X-ray absorption spectrum, emission spectrum, especially the soft X-ray resonance inelastic scattering method to demonstrate the stability of O hole after multiple cycles (in a specific material system).

With the help of RIXS measurement, the d-band structure of I-Ni@C and its contrast Ni@C and I-Ni have been studied. Finally, the energy required for the valence band electron of Ni@C, I-Ni@C, and I-Ni to transit to the unoccupied state increases in turn, That is, the d-band center of the three decreases in reduced, While the modest d-band energy level of I-Ni@C at the Ni site helps to balance the adsorption / desorption capacity of key intermediates, Further electrochemical tests demonstrated the excellent alkaline HER catalytic properties (activity, stability, etc.) of I-Ni@C, Beyond most of the reported transition metal-based basic HER catalysts. Journal of American Chemical Society, 2024