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The initial step of photocatalytic water oxidation reaction at the metal oxide/aqueous interface involves intermediates formed by trapping photogenerated, valence band holes on different reactive sites of the oxide surface. In SrTiO3, these one-electron intermediates are radicals located in Ti–O• (oxyl) and Ti–O•–Ti (bridge) groups arranged perpendicular and parallel to the surface respectively, and form electronic states in the band gap of SrTiO3.

X-ray absorption studies of the geometric and electronic structure of primarily heterogeneous Co, Ni, and Mn based water oxidation catalysts are reviewed. The X-ray absorption near edge and extended X-ray absorption fine structure studies of the metal K-edge, characterize the metal oxidation state, metal–oxygen bond distance, metal–metal distance, and degree of disorder of the catalysts.

The Co 2p3/2 X-ray absorption spectroscopy and high-energy-resolution (∼0.09 eV fwhm) 2p3d resonant inelastic X-ray scattering (RIXS) spectra of the single-cobalt-centered polyoxometalate K5H[CoW12O40]·xH2O were measured. The low-energy dd transition features at 0.55 eV, unmeasurable with ultraviolet–visible (UV/vis) spectroscopy, were experimentally revealed in 2p3d RIXS spectra.

Although the water oxidation cycle involves the critical step of O–O bond formation, the transition metal oxide radical thought to be the catalytic intermediate for this step has eluded direct observation. The radical represents the transformation of charge into a nascent catalytic intermediate, which lacks a newly formed bond and is therefore inherently difficult to detect.

While charge transport and surface reactivity have thus far been treated as independent phenomena, the interfacial carrier mobility could be highly dependent on reaction intermediates that carry localized charge and can hop from site to site along the surface.

Facile and reversible deposition of metal layers would enhance power and energy densities of hybrid batteries. Here, we investigate Cu2+/Cu(0) deposition on a RuO2anode and soluble Fe2+/Fe3+ oxidation on a symmetric RuO2 cathode in aqueous electrolyte.

The excited state dynamics of a d0 vanadium(V) oxido ligand-to-metal charge transfer (LMCT) complex, VOLF, were investigated via a combination of static optical and X-ray absorption (XAS) spectroscopy, transient optical absorption spectroscopy, and time-dependent density functional theory (TD-DFT). Upon excitation of the LMCT in the visible region, transient absorption data reveal that internal conversion traps the excited carrier population into a long-lived charge transfer state of 3dxy electron character, S1(dxy).

We have performed cobalt L-edge X-ray absorption spectroscopy (XAS) on important materials for photoactive catalysis, namely nanoscale cobalt polyoxometalates (Co POM) and a Co3O4 thin film. A set of Co POM analogues were studied that vary according to the position and number of cobalts within the POM structure, metal valence state, oxygen ligand coordination geometry and heteroatom identity.

Interfacial hole transfer between n-SrTiO3 and OH– was investigated by surface sensitive transient optical spectroscopy of an in situ photoelectrochemical cell during water oxidation. The kinetics reveal a single rate constant with an exponential dependence on the surface hole potential, spanning time scales from 3 ns to 8 ps over a ≈1 V increase.

The spectrum and dynamics of excited carriers in a spinel-ordered transition metal oxide, Co3O4, were investigated by both selective photoexcitation of all major optical transitions and selectively filling electronic states through an applied voltage.