D. Borgmann

Bio: D. Borgmann is an academic researcher from University of Erlangen-Nuremberg. The author has contributed to research in topics: X-ray photoelectron spectroscopy & Adsorption. The author has an hindex of 14, co-authored 37 publications receiving 833 citations.

New setup for in situ x-ray photoelectron spectroscopy from ultrahigh vacuum to 1 mbar

Abstract: In an effort to extend the pressure range for electron-based spectroscopies from ultrahigh vacuum into the so-called pressure gap region, we have built a new apparatus for in situ x-ray photoelectron spectroscopy up to 1mbar. The principle of the experimental setup is based on a modified hemispherical electron energy analyzer, a modified twin anode x-ray source, and several differential-pumping stages between sample region and electron detection. The reaction gas is provided in situ either by background dosing or, as a new feature, by beam dosing, using a directed gas beam from a small tube. The latter allows for higher local pressures. The performance of the new setup is discussed, deriving normalization procedures from the analysis of the attenuation of the substrate photoemission intensity by the increasing gas phase pressure. In addition, the change of the work function due to changes in surface composition can be evaluated in situ by analyzing the binding energy shift of the gas phase core-level peak...

Microscopic models of PdZn alloy catalysts: structure and reactivity in methanol decomposition.

Abstract: We review systematic experimental and theoretical efforts that explored formation, structure and reactivity of PdZn catalysts for methanol steam reforming, a material recently proposed to be superior to the industrially used Cu based catalysts. Experimentally, ordered surface alloys with a Pd : Zn ratio of ∼1 : 1 were prepared by deposition of thin Zn layers on a Pd(111) surface and characterized by photoelectron spectroscopy and low-energy electron diffraction. The valence band spectrum of the PdZn alloy resembles closely the spectrum of Cu(111), in good agreement with the calculated density of states for a PdZn alloy of 1 : 1 stoichiometry. Among the issues studied with the help of density functional calculations are surface structure and stability of PdZn alloys and effects of Zn segregation in them, and the nature of the most likely water-related surface species present under the conditions of methanol steam reforming. Furthermore, a series of elementary reactions starting with the decomposition of methoxide, CH3O, along both C–H and C–O bond scission channels, on various surfaces of the 1 : 1 PdZn alloy [planar (111), (100) and stepped (221)] were quantified in detail thermodynamically and kinetically in comparison with the corresponding reactions on the surfaces Pd(111) and Cu(111). The overall surface reactivity of PdZn alloy was found to be similar to that of metallic Cu. Reactive methanol adsorption was also investigated by in situ X-ray photoelectron spectroscopy for pressures between 3 × 10−8 and 0.3 mbar.

Adsorbent Materials for Carbon Dioxide Capture from Large Anthropogenic Point Sources

Abstract: Since the time of the industrial revolution, the atmospheric CO(2) concentration has risen by nearly 35 % to its current level of 383 ppm. The increased carbon dioxide concentration in the atmosphere has been suggested to be a leading contributor to global climate change. To slow the increase, reductions in anthropogenic CO(2) emissions are necessary. Large emission point sources, such as fossil-fuel-based power generation facilities, are the first targets for these reductions. A benchmark, mature technology for the separation of dilute CO(2) from gas streams is via absorption with aqueous amines. However, the use of solid adsorbents is now being widely considered as an alternative, potentially less-energy-intensive separation technology. This Review describes the CO(2) adsorption behavior of several different classes of solid carbon dioxide adsorbents, including zeolites, activated carbons, calcium oxides, hydrotalcites, organic-inorganic hybrids, and metal-organic frameworks. These adsorbents are evaluated in terms of their equilibrium CO(2) capacities as well as other important parameters such as adsorption-desorption kinetics, operating windows, stability, and regenerability. The scope of currently available CO(2) adsorbents and their critical properties that will ultimately affect their incorporation into large-scale separation processes is presented.