An Atomic Force Microscopy Study of the Morphological Evolution of the MoO3 (010) Surface during Reduction Reactions
نویسندگان
چکیده
Atomic force microscopy was used to characterize the nanometerscale structural evolution of the MoO3 (010) surface during reaction with hydrogen at 400◦C. Two primary surface modifications were identified. First, water vapor, when present in the reactor either as an impurity or as an oxidation product, accelerates the volatilization of MoO3 and leads to the formation of surface voids. The presence of these voids increases the density of (100) and (h0l)-type surface sites on the basal planes. Second, oxygen removal leads to the formation of crystallographic shear planes. The intersection of these defects with the (010) surface creates 2 Å high steps along 〈001〉 and their presence indicates that the surface vacancy concentration has reached an upper limit. The mechanisms by which these structural changes might influence the reactivity of molybdenum oxide catalysts are discussed. c © 1996 Academic Press, Inc.
منابع مشابه
The Morphological Evolution of the MoO3(010) Surface during Reactions in Methanol–Air Mixtures
Atomic force microscopy has been used to characterize the evolution of MoO3(010) growth and cleavage surfaces during reactions with air–N2–MeOH mixtures between 200 and 300◦C. At reaction temperatures ≥250◦C, closed step loops, bounded by undercoordinated surface Mo sites, nucleate and grow as the (010) surface volatilizes in a nearly layer-by-layer fashion. The density and crystallography of t...
متن کاملThe Protonation of MoO3 during the Partial Oxidation of Alcohols
Atomic force microscopy and X-ray diffraction have been used to characterize the structural evolution of the MoO3(010) surface during gas phase reactions with nitrogen-alcohol (methanol, ethanol, and 2-propanol) mixtures between 200 and 400◦C. Our results demonstrate that MoO3 intercalates H during these reactions (T≥ 300◦C) and that protonation leads to the precipitation of a well known hydrog...
متن کاملThe Structure Sensitivity of HxMoO3 Precipitation on MoO3(010)during Reactions with Methanol
Atomic force microscopy has been used to examine the effect of surface morphology on the formation of HxMoO3 during the reaction of MoO3 with methanol. By heating MoO3 crystals in hydrous environments, pits can be formed on the (010) surface. We have found that pit formation is activated by elastic strain from extended defects and because of this, it is possible to exercise some degree of contr...
متن کاملExploring mechanism of xanthate adsorption on chalcopyrite surface: An atomic force microscopy study
In this work, adsorption of the potassium amyl xanthate collector on the pure chalcopyrite surface was studied by applying atomic force microscopy (AFM). The adsorption experiments were carried out at different concentrations of the collector and at diverse pH values in the presence or absence of exterior ions. The changes occurring in the surface morphology of chalcopyrite due to the collector...
متن کاملThermal Oxidation Times Effect on Structural and Morphological Properties of Molybdenum Oxide Thin Films Grown on Quartz Substrates
Molybdenum oxide (α-MoO)thin films were prepared on quartz and silicon substrates by thermal oxidation of Mo thin films deposited using DC magnetron sputtering method. The influence of thermal oxidation times ranging from 60-240 min on the structural and morphological properties of the preparedfilms was investigated using X-ray diffraction, Atomic force microscopy and Fourier transform infrared...
متن کامل