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Methodologies and Advanced Characterizations of Photoelectrochemical Processes
Published in Anirban Das, Gyandshwar Kumar Rao, Kasinath Ojha, Photoelectrochemical Generation of Fuels, 2023
Camilla Tossi, Ornella Laouadi, Ilkka Tittonen, Aadesh P. Singh
X-ray photoelectron spectroscopy (XPS) is a technique for chemical analysis that exploits the energy emitted by electrons which, after being excited by X-ray photons, are ejected from the sample. The kinetic energy of the emitted electrons provides information on the chemical species present on the surface of the analyzed sample, with a depth of a few nanometers: this technique is of interest for analyzing the chemical and structural properties of the electrode. In particular, it can determine if there are dangling bonds on the surface of a metal oxide, which can easily attract solvated ions in the electrolyte, or if the material formed a native oxide that can protect the layer from corrosion, or if there is a space charge layer that favors the separation of photogenerated charge carriers of opposite sign. XPS is usually performed exsitu, to evaluate the chemical state of the working material both before use and after use: before use, it helps in predicting the behavior of the material at the interface with the electrolyte, while immediately after use it provides information on how the water and the dissolved ions have interacted with the WE: intermediate products may deposit on the surface, corrosion sites may reveal recrystallization or recomposition of the material, and the results can be invested immediately toward the improvement of the fabrication techniques and the engineering of the working materials [54].
Electrolytes for High-Voltage Lithium-Ion Battery
Published in Ming-Fa Lin, Wen-Dung Hsu, Jow-Lay Huang, Lithium-Ion Batteries and Solar Cells, 2021
Ming-Hsiu Wu, Chih-Ao Liao, Ngoc Thanh Thuy Tran, Wen-Dung Hsu
Candidate molecules can be synthesized and characterized by various techniques for electrochemical testing. It is worthwhile noting that the energy level of IE can be measured by ultraviolet photoelectron spectroscopy and inverse photoemission spectroscopy [28]. The main principle of photoelectron spectroscopy is that the source of radiation can eject molecular electrons from core orbitals or valence orbitals. The IE is obtained by subtracting the energy of the source radiation from the measured kinetic energy of the ejected electron. For the energy level of EA, it can be also measured by photoelectron spectroscopy and laser photodetachment [29]. Both methods directly measure threshold energy for the removal of an electron from the molecular anion. In addition, by using the voltammetric technique, the redox potentials (reduction/ oxidation potentials that are proportional to IE/EA values, respectively) can be verified by cyclically sweeping a potential between a working electrode and a reference electrode in the solution, while measuring the current response [30]. The experimental results can be compared with the density-functional theory calculation results.
Work Functions and Injection Barriers
Published in Juan Bisquert, The Physics of Solar Energy Conversion, 2020
In ultraviolet photoelectron spectroscopy (UPS), a sample in vacuum is irradiated with high-energy monochromatic light, and the energy distribution of emitted electrons is measured by a detector that has a common Fermi level with the sample. The source of photons often used is HeI (hν = 21.2 V) or HeII radiation (hν = 40.8 eV). These high-energy photons excite electrons from the valence band of the irradiated material. The sources of photons in x-ray photoelectron spectroscopy (XPS) are x-ray tubes that produce more energetic photons between 1.2 and 1.5 keV. XPS can access, in addition to the valence band region, deeply bound core-level electronic states that are characteristic of the specific chemical element.
Bayesian estimation for XPS spectral analysis at multiple core levels
Published in Science and Technology of Advanced Materials: Methods, 2021
Atsushi Machida, Kenji Nagata, Ryo Murakami, Hiroshi Shinotsuka, Hayaru Shouno, Hideki Yoshikawa, Masato Okada
X-ray photoelectron spectroscopy (XPS) is a technique to measure the kinetic energy distribution of photoelectrons emitted by X-ray irradiation and to obtain information on the type, amount and chemical bonding state of elements present on the surface of a sample, which is used in various surface analyses of materials. In the field of spectroscopy, reference spectrum databases are being rapidly constructed, and it is necessary to develop automated spectrum analysis methods using reference spectrum data. Previous studies developed a method to estimate parameters such as composition ratios, peak position adjustments and peak width adjustments of samples using genetic algorithms [1]. Additionally, this method makes it possible to identify the combinations of compounds in samples using Bayesian information criterion. The genetic algorithms, however, do not allow us to make statistical reliability assessments about the results of the estimation.
Effects of Gamma Irradiation on the Morphological, Physical, and Thermal Properties of B4C/CF/PI/AA6061 Hybrid Composite Laminates
Published in Nuclear Science and Engineering, 2020
Xuelong Fu, Jie Tao, Dunwen Zuo
X-ray photoelectron spectroscopy (XPS) is a powerful technique for analyzing the surface chemistry, primarily analyzing the chemical composition of materials with depths less than 10 nm. When an electron beam penetrates the specimens, the carrier will be released by a specific group owing to the presence of ionizing radiation and transported as a substance between the strands or groups. For the BCPAs, the influence of gamma irradiation on the polyimide resin group is analyzed; carbon as a main element in the polyimide chain is an important functional group; and the group includes a C-O band, C = O band, C-N band, and C-C band.30Figure 8 shows a full XPS spectrum of the BCPAs gamma-irradiated with different doses. It can be seen that the main elements in the full spectrum were C, O, and N. The peak intensity of C1s and O1s exhibited a slight difference with the irradiation dose, while the parameters of C1s and the corresponding state changes can be deduced. The irradiation defects and relative evolution mechanism are described. Therefore, the C1s spectra of the BCPAs after gamma irradiation are analyzed in this section.
Probing the nature of soil organic matter
Published in Critical Reviews in Environmental Science and Technology, 2022
Zhe (Han) Weng, Johannes Lehmann, Lukas Van Zwieten, Stephen Joseph, Braulio S. Archanjo, Bruce Cowie, Lars Thomsen, Mark J. Tobin, Jitraporn Vongsvivut, Annaleise Klein, Casey L. Doolette, Helen Hou, Carsten W. Mueller, Enzo Lombi, Peter M. Kopittke
Technical background: X-ray photoelectron spectroscopy (XPS) is a quantitative spectroscopic technique based on the photoelectric effect that can identify the elemental composition, chemical state, and the overall electron status of elements within a material or on its surface. In a manner similar to NEXAFS, for XPS the sample is irradiated with an incident photon (X-ray) beam. XPS analysis can be performed on both crushed and intact soil samples (Gerin et al., 2003; Mikutta et al., 2009).