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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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4 citations
TL;DR: In this paper, a coprecipitation method was used to synthesize catalysts consisting of ultra-fine gold particles supported on iron oxide, and each sample was heat treated in air at four different temperatures, ranging from 473 K to 773 K.
Abstract: Catalysts consisting of ultra-fine gold particles supported on iron oxide have been synthesized by the coprecipitation method. Subsequent to preparation, each sample was heat treated in air at four different temperatures, ranging from 473 K to 773 K. Steady state carbon monoxide oxidation was carried out over each sample. Upon extended reaction, catalyst deactivation took place over three of the catalysts whose respective surface compositions (e.g., gold to iron atomic ratio) were altered appreciably from their initial state. Surface structure analyses performed on all the unreacted catalysts have revealed variations in physical properties (e.g., degree of crystallinity and particle size). In addition, lattice parameters of gold were observed to increase up to 20 % from the bulk value. In contrast, XPS showed both gold and iron to be in essentially the same chemical states for all catalysts, irrespective of heat treatment temperatures. The importance of surface sensitive parameters to catalytic function are discussed.
4 citations
31 Aug 2017
TL;DR: In this article, a strategy for design and preparing such kind of complex catalysts was proposed, by means of loading nano crystallites of La1-xYxCo1-yCuyO3 with perovskite phase on SiO2 and then reducing La 1-x yxCo 1-y CuyO 3/SiO2.
Abstract: Cu−Co based catalysts for ethanol synthesis (ES) directly from syngas requires that copper and cobalt should be in alloy state or in close contact with each other, the chemical state of the bimetallic Cu−Co should be tailored by more than one additives and the group composed of Cu−Co and the additives should be loaded on a support with high surface area. In this work, a strategy for design and preparing such kind of complex catalysts was proposed, by means of loading nano crystallites of La1-xYxCo1-yCuyO3 with perovskite phase on SiO2 and then reducing La1-xYxCo1-yCuyO3/SiO2. In a nano crystallite of La1-xYxCo1-yCuyO3, the ions of copper and cobalt are uniformly mixed at the atomic level and confined in the nano space, favoring the interaction between the reduced products of Cu, Co, La2O3 and Y2O3. Thus, prepared catalyst showed very good catalytic performance for ES. This preparation strategy should be extendable.
4 citations
TL;DR: McGrath et al. as discussed by the authors showed that the effect of acid on the aurocyanide adsorbed on activated carbon is to actually produce limited chain length oligomers such as the tetramer Au4(CN) 5 −.
Abstract: In a recent paper by McGrath et al. [Hyp. Interact. 139/140 (2002), 471] the authors appear to have overlooked a body of prior work on the aurocyanide activated carbon system based on X-ray photoelectron spectroscopy. Unlike Mossbauer spectroscopy, limited to chemical state interpretations for a single absorber, XPS is usually capable or both quantitative chemical state assignment and stoichiometry for most atoms within the system. This earlier work shows that rather than producing a mixture of Au(CN) 2 − and AuCN the effect of acid on the aurocyanide adsorbed on activated carbon is to actually produce limited chain length oligomers such as the tetramer Au4(CN) 5 − . It clearly demonstrates the evolution of bridging (Nb) and terminal (Nt) nitrogen atoms with the relative concentration (for both N : Au and Nb : Nt) terminating at a stoichiometric ratio indicative of the oligomer. Other shortcomings of the paper in question are discussed.
4 citations
TL;DR: In this article, the adsorption of benzene and water vapors on the surface of detonation nanodiamond powders that differed in particle size, degree of their strong aggregation, and chemical state of their surface was studied.
Abstract: The adsorption of benzene and water vapors on the surface of detonation nanodiamond powders that differed in particle size, degree of their strong aggregation, and chemical state of their surface was studied. Specific features of the processes of adsorption of polar and nonpolar molecules on chemically modified surfaces of nanodiamonds are analyzed.
4 citations