skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: X-ray spectroscopic characterization of Co(IV) and metal–metal interactions in Co 4O 4: Electronic structure contributions to the formation of high-valent states relevant to the oxygen evolution reaction

Abstract

In this paper, the formation of high-valent states is a key factor in making highly active transition metal-based catalysts of the oxygen-evolving reaction (OER). These high oxidation states will be strongly influenced by the local geometric and electronic structures of the metal ion, which is difficult to study due to spectroscopically active and complex backgrounds, short lifetimes, and limited concentrations. Here, we use a wide range of complementary X-ray spectroscopies coupled to DFT calculations to study Co 4O 4 cubanes, which provide insight into the high-valent Co(IV) centers responsible for the activity of molecular and heterogeneous OER catalysts. The combination of X-ray absorption and 1s3p resonant inelastic X-ray scattering (Kβ RIXS) allow Co(IV) to be isolated and studied against a spectroscopically active Co(III) background. Co K- and L-edge X-ray absorption data allow for a detailed characterization of the 3d-manifold of effectively localized Co(IV) centers and provide a direct handle on the ligand field environment and covalency of the t 2g-based redox active molecular orbital. Kβ RIXS is also shown to provide a powerful probe of Co(IV), and specific spectral features are sensitive to the degree of oxo-mediated metal-metal coupling across Co 4O 4. Guided by the data, calculations show electron-holemore » delocalization can actually oppose Co(IV) formation. Computational extension of Co 4O 4 to CoM 3O 4 structures (M = redox-inactive metal) defines electronic structure contri-butions to Co(IV) formation. Redox activity is shown to be linearly related to covalency, and M(III) oxo inductive effects on Co(IV) oxo bonding can tune the covalency of high-valent sites over a large range and thereby tune E 0 over hundreds of mVs.« less

Authors:
 [1];  [1];  [2];  [2];  [1];  [1];  [2];  [3]
  1. Argonne National Lab. (ANL), Lemont, IL (United States)
  2. Harvard Univ., Cambridge, MA (United States)
  3. Argonne National Lab. (ANL), Lemont, IL (United States); Northwestern Univ., Evanston, IL (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1339577
DOE Contract Number:
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 138; Journal Issue: 34
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Hadt, Ryan G., Hayes, Dugan, Brodsky, Casey N., Ullman, Andrew M., Casa, Diego M., Upton, Mary H., Nocera, Daniel G., and Chen, Lin X. X-ray spectroscopic characterization of Co(IV) and metal–metal interactions in Co4O4: Electronic structure contributions to the formation of high-valent states relevant to the oxygen evolution reaction. United States: N. p., 2016. Web. doi:10.1021/jacs.6b04663.
Hadt, Ryan G., Hayes, Dugan, Brodsky, Casey N., Ullman, Andrew M., Casa, Diego M., Upton, Mary H., Nocera, Daniel G., & Chen, Lin X. X-ray spectroscopic characterization of Co(IV) and metal–metal interactions in Co4O4: Electronic structure contributions to the formation of high-valent states relevant to the oxygen evolution reaction. United States. doi:10.1021/jacs.6b04663.
Hadt, Ryan G., Hayes, Dugan, Brodsky, Casey N., Ullman, Andrew M., Casa, Diego M., Upton, Mary H., Nocera, Daniel G., and Chen, Lin X. 2016. "X-ray spectroscopic characterization of Co(IV) and metal–metal interactions in Co4O4: Electronic structure contributions to the formation of high-valent states relevant to the oxygen evolution reaction". United States. doi:10.1021/jacs.6b04663.
@article{osti_1339577,
title = {X-ray spectroscopic characterization of Co(IV) and metal–metal interactions in Co4O4: Electronic structure contributions to the formation of high-valent states relevant to the oxygen evolution reaction},
author = {Hadt, Ryan G. and Hayes, Dugan and Brodsky, Casey N. and Ullman, Andrew M. and Casa, Diego M. and Upton, Mary H. and Nocera, Daniel G. and Chen, Lin X.},
abstractNote = {In this paper, the formation of high-valent states is a key factor in making highly active transition metal-based catalysts of the oxygen-evolving reaction (OER). These high oxidation states will be strongly influenced by the local geometric and electronic structures of the metal ion, which is difficult to study due to spectroscopically active and complex backgrounds, short lifetimes, and limited concentrations. Here, we use a wide range of complementary X-ray spectroscopies coupled to DFT calculations to study Co4O4 cubanes, which provide insight into the high-valent Co(IV) centers responsible for the activity of molecular and heterogeneous OER catalysts. The combination of X-ray absorption and 1s3p resonant inelastic X-ray scattering (Kβ RIXS) allow Co(IV) to be isolated and studied against a spectroscopically active Co(III) background. Co K- and L-edge X-ray absorption data allow for a detailed characterization of the 3d-manifold of effectively localized Co(IV) centers and provide a direct handle on the ligand field environment and covalency of the t2g-based redox active molecular orbital. Kβ RIXS is also shown to provide a powerful probe of Co(IV), and specific spectral features are sensitive to the degree of oxo-mediated metal-metal coupling across Co4O4. Guided by the data, calculations show electron-hole delocalization can actually oppose Co(IV) formation. Computational extension of Co4O4 to CoM3O4 structures (M = redox-inactive metal) defines electronic structure contri-butions to Co(IV) formation. Redox activity is shown to be linearly related to covalency, and M(III) oxo inductive effects on Co(IV) oxo bonding can tune the covalency of high-valent sites over a large range and thereby tune E0 over hundreds of mVs.},
doi = {10.1021/jacs.6b04663},
journal = {Journal of the American Chemical Society},
number = 34,
volume = 138,
place = {United States},
year = 2016,
month = 8
}
  • The anodic O{sub 2} evolution reaction (OER) at noble-metal anodes provides an important case of electrocatalysis where the electrode surface on which the reaction proceeds depends on potential, through the state of the surface of a thin oxide film developed upon it. An essential but little examined aspect of electrocatalysis is the behavior of the kinetically involved intermediates of the reaction at the electrode's surface in relation to the potential dependence of the electrode reaction rate, characterized by the Tafel slope. Digitally recorded potential relaxation transients following current interruption are used, as in our previous studies on cathodic H{sub 2}more » evolution, to evaluate the pseudocapacitance (C{sub {var phi}}) of intermediates generated in the steady state of the OER at Pt and hence the potential dependence of coverage by the kinetically significant intermediate states in the reaction.« less
  • YBa/sub 2/Cu/sub 3/O/sub 7/..sqrt../sub delta/ is obtained over a wide range of stoichiometry (00.5) to the superconducting metallic state (deltaapprox. =0). On the basis of our experimental results, we argue that the superconducting state is obtained from a mixture of configurations chemically bond3d/sup 9/> and chemically bond3d/sup 9/Lk> in the ground state of copper (L stands for a hole in the O-Cu ligand and k for a conduction electron). We find that the ratio of the chemically bond3d/sup 9/Lk> configuration is directly related to the magnitude of T/sub c/. The charge-neutrality rule is approximatively followed, provided that the Cu/sup 3more » +/ state is identified as a chemically bond3d/sup 9/Lk> configuration. We discuss also the presence of the 3d/sup 10/ configuration (i.e., Cu/sup +/) in the ground state. A possible consequence of these Cu/sup +/ would be to increase the number of formal Cu/sup 3 +/ (here 3d/sup 9/Lk)« less
  • High resolution He I (584 A) photoelectron spectra of ZnCl{sub 2}, MnCl{sub 2}, and NiCl{sub 2} were measured using a high temperature supersonic molecular beam source. In ZnCl{sub 2}, vibrational structures were resolved, and spectroscopic constants were derived for the observed molecular ion states. A single {nu}{sub 1} vibrational progression was observed for the {ital C} {sup 2}{Sigma}{sup +}{sub {ital g}} state of ZnCl{sup +}{sub 2}. A Franck--Condon factor calculation allowed us to obtain a Zn--Cl equilibrium bond length increase of 0.095(5) A and a {nu}{sub 1} vibrational frequency of 290(8) cm{sup {minus}1}. For the open-shell molecules, MnCl{sub 2} andmore » NiCl{sub 2}, no vibrational structure could be resolved because of their very low bending frequencies. Transitions from the ligand orbital and metal {ital d} orbital ionizations were clearly resolved, with those of the {ital d} orbitals having considerably narrower band widths. Even though many final states are expected for ionization of the open-shell {ital d} orbitals, only a few states were observed. This was explained in MnCl{sub 2} by the one-electron spin selection rule: {ital S}{sub {ital f}}={ital S}{sub {ital i}} {plus minus}1/2. Besides the spin selection rule, a propensity toward high spin was proposed to account for the spectrum of NiCl{sub 2}. From the metal {ital d} orbital and ligand orbital splittings, the degree of covalent bonding was inferred to be in the order of: MnCl{sub 2}{gt}NiCl{sub 2}{gt}ZnCl{sub 2}.« less