jp410644j_si_001.pdf (247.3 kB)
Estimating Hybridization of Transition Metal and Oxygen States in Perovskites from O K‑edge X‑ray Absorption Spectroscopy
journal contribution
posted on 2014-01-30, 00:00 authored by Jin Suntivich, Wesley T. Hong, Yueh-Lin Lee, James
M. Rondinelli, Wanli Yang, John B. Goodenough, Bogdan Dabrowski, John W. Freeland, Yang Shao-HornThe
interaction between the transition metal 3d and the
oxygen 2p states via hybridization underpins
many of the phenomena in transition metal oxide materials. We report
the empirical trend of this interaction using the pre-edge feature
of the O K-edge X-ray absorption spectrum. Our assessment
method is built on the dipole approximation and the configuration
interaction between the transition metal 3d and the
oxygen 2p states. We found that hybridization increases
with the number of 3d electrons, consistent with
the expected electronegativity trend. We support this analysis with
density functional calculations, which reveal a systematic increase
in the transition metal 3d and the oxygen 2p state mixing with increasing 3d-electron
number. Oxidation of the transition metal was also found to increase
hybridization, which we believe reflects the reduced transition metal
3d and oxygen 2p energy difference,
causing increased covalency. We compare the analysis from the surface-sensitive
electron-yield and the bulk-sensitive fluorescence-yield spectra,
revealing that either method can be used to study the hybridization
trend. We finally compare and discuss the influence of the lanthanide
ions and the influence of the covalency on oxygen electrocatalysis.
Our study describes an efficient and simple approach to understand
the hybridization trend in transition metal oxides, which has considerable
implications for electrochemical energy conversion processes.