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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 authors studied the correlation between the chemical state and the oxygen-sensing properties of an iron oxide thin film using a setup that allows simultaneous sensor resistance measurements and X-ray photoelectron spectroscopy (XPS) data acquisition.
62 citations
TL;DR: In this article, the behavior of Pd-based systems supported on alumina and ceria-zirconia and the complex Ceria-Zirconium-supported catalyst was investigated during light-off tests using a stoichiometric C3H6 + CO + NO + O2 mixture.
62 citations
TL;DR: In this paper, the chemical states of copper ions in various kinds of silicate glasses were investigated by X-ray photoelectron spectroscopy (XPS) and Xray-induced Auger electron spectrochamber (XAES).
62 citations
TL;DR: In this paper, a sacrificial anode electrosynthesis route was used to obtain catalysts made of Pd supported on ZrO2, which were tested for CH4 total combustion and for CO oxidation.
Abstract: Catalysts made of Pd supported on ZrO2 were prepared via a sacrificial anode electrosynthesis route. Tetragonal zirconia was added to an electrolytic cell assembled for the preparation of colloidal Pd nanoparticles. Several samples were prepared varying the electrolysis time and thus the Pd loading in the nanocomposite. XRD analysis showed the presence of the tetragonal ZrO2 mainly and some small reflections due to monoclinic ZrO2. BET surface areas were in the range 70–80 m2 g−1. The morphology and surface chemical composition of the nano-materials were, respectively, assessed by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses. From TEM evidence, the Pd-ZrO2 powders revealed to be composed of spherical Pd nanoparticles (average core diameter: 6.9 ± 1.8 nm) evenly dispersed on the surface of ZrO2 nano-grains (average grain size: 150 ± 70 nm, average size of crystallites composing each grain: 40 ± 10 nm). XPS allowed to quantify the surface elemental composition of the nanomaterials and to study the different chemical states of the nano-dispersed palladium. Catalysts were tested for CH4 total combustion and for CO oxidation. The conversion increased with Pd content in the CH4 combustion experiments whereas decreased with Pd content in the CO oxidation experiments. The apparent activation energies were about 25 and 9 kcal mol−1 for CH4 combustion and CO oxidation, respectively. Hypothesis was made that different reaction mechanisms and different active sites were probably involved in the two reactions.
62 citations
TL;DR: In this article, a series of Ce-TiO 2 /SiO 2 coatings on SiO 2 were prepared by the sol-gel process and characterized by TG-DTA, XRD, SEM, XPS and DRS.
Abstract: A series of Ce-TiO 2 /SiO 2 (Ce-TiO 2 coatings on SiO 2 ) were prepared by the sol–gel process and characterized by TG–DTA, XRD, SEM, XPS and DRS. The photocatalytic activities of Ce-TiO 2 /SiO 2 for the oxidation of formaldehyde irradiated by 250 W high-pressure mercury lamp were investigated. According to XPS investigation, the Ti element mainly existed as the chemical state of Ti 4+ , and Ce is present mainly in the +4 oxidation state and a little in the +3 oxidation state. The effect of cerium content on the photocatalytic activities was studied, and the result reveals that 0.10%Ce-TiO 2 /SiO 2 exhibits highest photoactivity. The light absorption of Ce-TiO 2 /SiO 2 increases with increasing cerium content, and cerium doping causes absorption spectra of Ce-TiO 2 /SiO 2 to shift to the visible region. The high photocatalytic activity of Ce-TiO 2 /SiO 2 can be explained by the effective separation of photogenerated electron–hole pairs, which are trapped by Ce 4+ and hydroxyl groups balancing the positive charge generated by the incorporation of Si in a Ti matrix, respectively.
61 citations