<i>T-REX</i>: new software for advanced QEXAFS data analysis

Stötzel, Jan; Lützenkirchen‐Hecht, Dirk; Grunwaldt, Jan‐Dierk; Frahm, R.

doi:10.1107/s0909049512038599

Cited by 6 publications

(2 citation statements)

References 63 publications

(64 reference statements)

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“…QEXAFS allows for a fast data acquisition in the subsecond range under realistic in situ conditions. The application of MES on QEXAFS improves the signal-to-noise ratios without losing time or energy resolution, which makes this approach attractive for relatively fast reactions. − In that example, a principal component analysis (PCA) revealed two distinct regimes (heating and ignition) within the full modulation period . Later, Ferri and co-workers published phase-resolved spectra of noble-metal catalysts during the catalytic oxidation of CO and the reduction of NO by CO. − These studies showed the potential of MES for XAS as it drastically increased surface sensitivity and ultimately formed the basis to study working catalysts, even at low metal loading, that have been previously intractable for dynamic in situ studies.…”

Section: Mes Applicationsmentioning

confidence: 99%

Applications of Modulation Excitation Spectroscopy in Heterogeneous Catalysis

Müller

Hermans

2017

Ind. Eng. Chem. Res.

110

101

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In situ and operando spectroscopic techniques are crucial for our understanding of complex heterogeneously catalyzed reactions. Under actual reaction conditions, however, many phenomena such as adsorption, (by)-product formation, and desorption of various species in different phases occur simultaneously, leading to crowded spectra that are difficult to interpret. About 15 years ago, modulation excitation spectroscopy (MES) was introduced to the heterogeneous catalysis community and has been increasingly applied since then. The periodic perturbation of a given system, in combination with phase-sensitive detection (PSD) analysis, significantly reduces noise, distinguishes between active and spectator species, and enables extraction of kinetic information. In this review article, we discuss the origin and theory of MES, summarize different application examples (with an emphasis on heterogeneous catalysis), and suggest future developments of the technique.

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Section: Mes Applicationsmentioning

confidence: 99%

Applications of Modulation Excitation Spectroscopy in Heterogeneous Catalysis

Müller

Hermans

2017

Ind. Eng. Chem. Res.

110

101

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“…With third-generation synchrotrons, wigglers and undulators, numerous advanced XAFS beamlines can provide very high fluxes across central energy ranges. If samples are stable under this flux density and this is then complemented by very high detector linearity and very fast stable detectors (Stö tzel et al, 2012;Lutzenkirchen-Hecht & Frahm, 2001), then (intrinsic) standard errors can be reduced by a factor of ten or so, or alternatively the counting time can be reduced by 100 or 1000, whether for dynamic investigations or simple throughput.…”

Section: Q2xafs Workhopmentioning

confidence: 99%

A step toward standardization: development of accurate measurements of X-ray absorption and fluorescence

Chantler

Barnea

Tran

et al. 2012

J Synchrotron Radiat

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This paper explains how to take the counting precision available for XAFS (X-ray absorption fine structure) and attenuation measurements, of perhaps one part in 10(6) in special cases, to produce a local variance below 0.01% and an accuracy of attenuation of the order 0.01%, with an XAFS accuracy at a similar level leading to the determination of dynamical bond lengths to an accuracy similar to that obtained by standard and experienced crystallographic measurements. This includes the necessary corrections for the detector response to be linear, including a correction for dark current and air-path energy dependencies; a proper interpretation of the range of sample thicknesses for absorption experiments; developments of methods to measure and correct for harmonic contamination, especially at lower energies without mirrors; the significance of correcting for the actual bandwidth of the beam on target after monochromation, especially for the portability of results and edge structure from one beamline to another; definitions of precision, accuracy and XAFS accuracy suitable for theoretical model analysis; the role of additional and alternative high-accuracy procedures; and discusses some principles regarding data formats for XAFS and for the deposition of data sets with manuscripts or to a database. Increasingly, the insight of X-ray absorption and the standard of accuracy needed requires data with high intrinsic precision and therefore with allowance for a range of small but significant systematic effects. This is always crucial for absolute measurements of absorption, and is of equal importance but traditionally difficult for (usually relative) measurements of fluorescence XAFS or even absorption XAFS. Robust error analysis is crucial so that the significance of conclusions can be tested within the uncertainties of the measurements. Errors should not just include precision uncertainty but should attempt to include estimation of the most significant systematic error contributions to the results. This is essential if the results are to be subject to deposition in a central accessible reference database; it is also crucial for specifying a standard data format for portability and ease of use by depositors and users. In particular this will allow development of theoretical formulations to better serve the world-wide XAFS community, and a higher and more easily comparable standard of manuscripts.

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Exhaust Gas Aftertreatment in Mobile Systems: Status, Challenges, and Perspectives

Deutschmann

Grunwaldt

2013

Chemie Ingenieur Technik

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Exhaust Gas Aftertreatment in Mobile Systems: Status, Challenges, and PerspectivesLooking at exhaust-gas after-treatment systems in its entirety leads to further improvement of emission control devices and to the accomplishment of future challenges such as lower legislative emission limits, new fuels, and more efficient engine concepts. This article provides an overview on the state-of-the art mobile exhaust-gas after-treatment devices. Current and future challenges are discussed in the light of present approaches such as hierarchical modeling reaching from DFT computations of molecular processes to CFD simulation of entire lines of exhaust-gas cleaning devices, close-to-reality emission control test benches and aging procedures, on-board diagnostics, and catalyst characterization at operating conditions and preferentially all length scales. In future, knowledge-based robot-controlled preparation and dynamic models coupled with information from real operation will significantly support research and development.

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T-REX: new software for advanced QEXAFS data analysis

Cited by 6 publications

References 63 publications

Applications of Modulation Excitation Spectroscopy in Heterogeneous Catalysis

Applications of Modulation Excitation Spectroscopy in Heterogeneous Catalysis

A step toward standardization: development of accurate measurements of X-ray absorption and fluorescence

Exhaust Gas Aftertreatment in Mobile Systems: Status, Challenges, and Perspectives

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