Topic
Chemical state
About: Chemical state is a research topic. Over the lifetime, 2378 publications have been published within this topic receiving 78183 citations.
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TL;DR: In this paper, the chemical state of POM catalysts in situ was studied using near ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) and mass spectrometry.
Abstract: Near ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) is used to study the chemical state of methane oxidation catalysts in-situ. Al2O3–supported Pd catalysts are prepared with different particle sizes ranging from 4 to 10 nm. These catalysts were exposed to conditions similar to those used in the partial oxidation of methane (POM) to syn-gas and simultaneously monitored by NAP-XPS and mass spectrometry. NAP-XPS data show changes in the oxidation state of the palladium as the temperature increases, from metallic Pd0 to PdO, and back to Pd0. Mass spectrometry shows an increase in CO production whilst the Pd is in the oxide phase, and the metal is reduced back under presence of newly formed H2. A particle size effect is observed, such that CH4 conversion starts at lower temperatures with larger sized particles from 6 to 10 nm. We find that all nanoparticles begin CH4 conversion at lower temperatures than polycrystalline Pd foil.
25 citations
TL;DR: In this paper, an X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive x-ray microanalysis (EEM) were employed to study the surface chemical and electronic state, composition, morphology and structure of a biocompatible Zr-31Ti-18Nb (at%) alloy and modification of these characteristics as a result of ultrasonic impact treatment (UIT).
25 citations
TL;DR: In this paper, the chemical state of Si(111) surfaces upon anisotropic etching in concentrated NH4F solution was investigated and minute amounts of oxidized silicon were detected and attributed to the fast Si-H-OH formation at atomic steps.
Abstract: Synchrotron radiation photoelectron spectroscopy was employed to investigate the chemical state of Si(111) surfaces upon anisotropic etching in concentrated NH4F solution. Minute amounts of oxidized silicon were detected and attributed to the fast Si–H–OH formation at atomic steps. Combining in situ optical and scanning probe techniques, consecutive chemical treatments were developed to achieve optimized morphological and chemical surface properties. Native oxides and a stressed SiO2/Si layer are removed by a two-step NH4F treatment leading to a terraced surface without triangular etch pits; subsequently, silicon in the Si1+/2+/3+ valence states is dissolved by HF (50%) while the surface topography is preserved.
25 citations
TL;DR: In this article, the binding energy of the Ti 2p lines is consistent with only one chemical state, Ti 4+, and the presence of Pb 0 state on the surface of all samples was due to the reduction of lead ions caused by the preferential removal of the oxygen ions after sputtering.
25 citations
TL;DR: In situ X-ray photoelectron spectroscopy (XPS) was applied to investigate the valence-band spectrum and to analyze the local chemical states of Zr and O in thin (thickness 400 K) oxide films.
Abstract: In situ X-ray photoelectron spectroscopy (XPS) was applied to investigate the valence-band spectrum and to analyze the local chemical states of Zr and O in thin (thickness 400 K The resolved Zr 3d5/2 and O 1s photoelectron lines and the Zr M45N1N23, Zr M45N23N23, Zr M45N23V, and O KL23L23 Auger transitions were combined to construct Wagner plots for Zr and O in the oxide films The observed decreases of the Zr and O Auger-parameter values with increasing oxidation temperature evidence a lowering of the electronic polarizability around core-ionized Zr and O atom
25 citations