Nickel HERFD XAS and VtC XES Characterization of the Intermediates States in Ni,Fe-CO-dehydrogenase

We propose Ni K𝛼 high-energy resolution fluorescence-detected X-ray absorption spectroscopy (HERFD XAS) and Ni K𝛽 X-ray emission spectroscopy (XES) studies of Ni,Fe-CO-dehydrogenase (CODH). Ni HERFD XAS will enable assignment of the geometry and oxidation states of three distinct catalytic intermediates, while Ni K𝛽 XES mainline spectra will provide complementary information on oxidation and spin states. In addition, Ni valence-to-core (VtC) XES will yield critical insight into the bonding and degree of activation of a CO₂-bound intermediate. Together, these experiments will offer fundamental mechanistic understanding of CODH reactivity, informing the design of selective, low-overpotential CO₂-to-CO catalysts.