https://www.surfacesciencewestern.com/wp-content/uploads/2012/01/ass11_biesinger.pdf

Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Sc, Ti, V, Cu and Zn

The generalization of the Local Density Approximation (LDA) method for the systems with strong Coulomb correlations is presented which gives a correct description of the Mott insulators. The LDA+U method is based on the model hamiltonian approach and allows to take into account the non-sphericity of the Coulomb and exchange interactions. parameters. Orbital-dependent LDA+U potential gives correct orbital polarization and corresponding Jahn-Teller distortion. To calculate the spectra of the strongly correlated systems the impurity Anderson model should be solved with a many-electron trial wave function. All parameters of the many-electron hamiltonian are taken from LDA+U calculations. The method was applied to NiO and has shown good agreement with experimental photoemission spectra and with the oxygen Kα X-ray emission spectrum.

https://iopscience.iop.org/article/10.1088/0953-8984/9/4/002/pdf

First-principles calculations of the electronic structure and spectra of strongly correlated systems: the LDA+ U method

Semiconductor photocatalysis has received much attention as a potential solution to the worldwide energy shortage and for counteracting environmental degradation. This article reviews state-of-the-art research activities in the field, focusing on the scientific and technological possibilities offered by photocatalytic materials. We begin with a survey of efforts to explore suitable materials and to optimize their energy band configurations for specific applications. We then examine the design and fabrication of advanced photocatalytic materials in the framework of nanotechnology. Many of the most recent advances in photocatalysis have been realized by selective control of the morphology of nanomaterials or by utilizing the collective properties of nano-assembly systems. Finally, we discuss the current theoretical understanding of key aspects of photocatalytic materials. This review also highlights crucial issues that should be addressed in future research activities.

Nano‐photocatalytic Materials: Possibilities and Challenges

We report new insights into the electrochemical reduction of CO2 on a metallic copper surface, enabled by the development of an experimental methodology with unprecedented sensitivity for the identification and quantification of CO2 electroreduction products. This involves a custom electrochemical cell designed to maximize product concentrations coupled to gas chromatography and nuclear magnetic resonance for the identification and quantification of gas and liquid products, respectively. We studied copper across a range of potentials and observed a total of 16 different CO2 reduction products, five of which are reported here for the first time, thus providing the most complete view of the reaction chemistry reported to date. Taking into account the chemical identities of the wide range of C1–C3 products generated and the potential-dependence of their turnover frequencies, mechanistic information is deduced. We discuss a scheme for the formation of multicarbon products involving enol-like surface intermediates as a possible pathway, accounting for the observed selectivity for eleven distinct C2+ oxygenated products including aldehydes, ketones, alcohols, and carboxylic acids.

New insights into the electrochemical reduction of carbon dioxide on metallic copper surfaces

The results of a systematic XPS study, under high controlled conditions, of different basic oxides of transition metals, alkali and alkaline-earth metals are presented; the XPS data of some hydroxides and peroxides are also reported. Variations of the O 1s binding energies are analysed and one point of interest is the large
 binding energy scale obtained for O 1s peaks all associated with a ‘‘2−
’’ formal charge. Through extended
 Huckel theory-tight binding (EHT-TB) calculations, attempts are made to rationalize the observed variations.
 The results illustrate
 the significant
 differences
 between real
 charges on oxygen atoms in transition metal and alkaline-earth oxides.

Systematic XPS studies of metal oxides, hydroxides and peroxides

The electronic structure of copper oxides has been investigated by photoelectron (x-ray photoemission, ultraviolet photoemission), Auger electron, and bremsstrahlung isochromat spectroscopies. The experimental results are compared with one-electron band-structure calculations as well as with a cluster configuration interaction model. It is demonstrated that the results for ${\mathrm{Cu}}_{2}$O agree well with band theory, whereas those for CuO clearly show strong deviations which we argue are due to electron-correlation effects in the open-shell $d$ bands. From the comparison to cluster calculations we extract values for the $\mathrm{Cu} d\ensuremath{-}d$ and $\mathrm{O} p\ensuremath{-}p$ Coulomb interactions, the O to Cu charge transfer energy, and the degree of $\mathrm{Cu} d\ensuremath{-}\mathrm{O} 2p$ hybridization. From this we demonstrate that CuO is a charge-transfer gap insulator.

Electronic structure of Cu2O and CuO

The electronic structure of ${\mathrm{Li}}_{\mathit{x}}$${\mathrm{Co}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$O (001\ensuremath{\le}x\ensuremath{\le}02), ${\mathrm{LiCoO}}_{2}$, and ${\mathrm{Co}}_{3}$${\mathrm{O}}_{4}$(1% Li) has been investigated using x-ray photoemission spectroscopy (XPS), bremsstrahlung isochromat spectroscopy (BIS), and x-ray-absorption spectroscopy The experimental results are compared with model cluster calculations We find that the CoO band gap is of an intermediate character, between Mott-Hubbard-like and charge-transfer-like The first ionization state of CoO is therefore of strongly mixed Co 3d and O 2p character Its local symmetry corresponds to $^{3}$${\mathit{T}}_{1\mathit{g}}$, similar to an intermediate-spin ${\mathrm{Co}}^{3+}$ state For x\ensuremath{\le}02 the local Co electronic structure is similar to that of CoO However, ${\mathrm{LiCoO}}_{2}$ has a strongly reduced Co-O interatomic distance, resulting in a ligand field strong enough to stabilize a ${\mathrm{Co}}^{3+}$ low-spin ground state ${\mathrm{LiCoO}}_{2}$ is an insulator with a gap of 27 eV From a comparison of the XPS and BIS CoO spectra to the cluster calculations, we find values for U (=53 eV), \ensuremath{\Delta} (=55 eV), and (pd\ensuremath{\sigma}) (=13 eV)

Electronic structure of CoO, Li-doped CoO, and LiCoO2

The electronic structure of ${\mathrm{Ag}}_{2}$O has been investigated by photoelectron, Auger-electron, and bremsstrahlung isochromat spectroscopy. The experimental results are compared with model one-particle band-structure and two-particle cluster calculations. We extract values for the on-site Ag 4d and O 2p energies, the Ag 4d--O 2p transfer integrals, as well as the on-site Coulomb Ag 4d-4d and O 2p-2p interactions. A comparison with ${\mathrm{Cu}}_{2}$O and CuO is made, and the differences are discussed in view of high-${T}_{c}$ superconductivity and the instability of AgO.

Electronic structure of Ag2O.

The electronic structure of ${\mathrm{Li}}_{\mathit{x}}$${\mathrm{Ni}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$O has been investigated using x-ray photoemission spectroscopy (XPS), bremsstrahlung isochromat spectroscopy (BIS), and model-Hamiltonian cluster calculations. The measurements support the conclusion that the Li-doped holes have mainly oxygen character. The unoccupied electronic structure as probed with BIS shows broad structures growing in the gap. By comparing the XPS valence band to the results of the cluster calculations, we determine values for the Racah A parameter (=6.6 eV), charge transfer \ensuremath{\Delta} (=6.2 eV), and hybridization transfer integral (pd\ensuremath{\sigma}) (=1.3 eV). The first ionization state in the NiO valence-band cluster calculation is of $^{2}$${\mathit{E}}_{\mathit{g}}$ symmetry, a state in which the doped hole is antiferromagnetically coupled to the Ni spins. Hole-doped cluster calculations explain, because of a different fractional parentage upon annihilating a Ni 3d or an O 2p hole, the difference between the O 1s XAS results and the BIS results of heavily Li-doped NiO.

Electronic structure of Li-doped NiO.

The electronic structure of MnO has been investigated using high-energy spectroscopies. An experimental gap of 3.9 eV is found. By comparing the experimental results to a configuration-interaction ...

J. van Elp

Papers

Electronic structure of Cu2O and CuO

Electronic structure of CoO, Li-doped CoO, and LiCoO2

Electronic structure of Ag2O.

Electronic structure of Li-doped NiO.

Electronic structure of MnO.