Quantitative Interpretation of K-Edge NEXAFS Data for Various Nickel Hydroxides and the Charged Nickel Electrode

A quantitative interpretation of Ni K-edge NEXAFS spectral line shapes for β-Ni(OH)2, β-NiOOH, and BaNiO3 and of in situ data for a charged Ni electrode are reported. We have performed curve−wave multiple scattering calculations utilizing the FEFF6 code on clusters approximating these materials. These theoretical results reproduce the experimental line shape changes with oxidation remarkably well. Our interpretation of the NEXAFS line shape for the charged electrode indicates that large amounts of Ni coordinated with six oxygen atoms exist along with Ni coordinated with two OH and four oxygen atoms, giving an average oxidation state slightly greater than 3.5, consistent with that shown elsewhere from the edge shift data.