Catalysts at work: From integral to spatially resolved X-ray absorption spectroscopy

Grunwaldt, Jan‐Dierk; Kimmerle, Bertram; Baiker, Alfons; Boye, Pit; Schroer, Christian G.; Glatzel, Pieter; Borca, Camelia N.; Beckmann, Felix

doi:10.1016/j.cattod.2008.11.002

Cited by 87 publications

(109 citation statements)

References 81 publications

Supporting

Mentioning

105

Contrasting

Order By: Relevance

“…This extends the application of these techniques from minerals, 48,49 transition metal complexes, 50 sensing, 24-26 batteries 27 and working catalysts, [51][52][53][54] for which they have already been proven to be sensitive tools for determining the oxidation state and coordination.…”

Section: Discussionmentioning

confidence: 70%

The Effect of Electrical Polarization on Electronic Structure in LSM Electrodes: An Operando XAS, RIXS and XES Study

Traulsen

Carvalho

Zielke

et al. 2017

J. Electrochem. Soc.

View full text Add to dashboard Cite

The influence of electrical polarization on Mn in La 0.5 Sr 0.5 MnO 3±δ electrodes has been investigated by operando High Energy Resolved Fluorescence Detected X-Ray Absorption Near-Edge Structure (HERFD-XANES) spectroscopy, Kβ X-ray Emission Spectroscopy (XES) and Resonant Inelastic X-ray Scattering (RIXS) at the Mn K-edge. The study of polarization induced changes in the electronic properties and structure has been carried out at 500 • C in 10-20% O 2 with electrical polarization applied in the range from −850 mV to 800 mV. Cathodic polarizations in the range −600 mV to −850 mV induced a shift in the Mn K edge energy towards lower energies. The shift is assigned to a decrease in the average Mn oxidation state, which based on Kβ XES changes from 3.4 at open circuit voltage to 3.2 at −800 mV applied potential. Furthermore, RIXS rendered pronounced changes in the population of the Mn 3d orbitals, due to filling of the Mn d-orbitals during the cathodic polarization. Overall, the study experimentally links the electrical polarization of LSM electrodes to the structural and electronic properties of Mn -these properties are expected to be of major importance for the electrocatalytic performance of LSM electrode towards the oxygen reduction reaction. In high temperature solid oxide electrolysis and solid oxide fuel cells LSM has for decades been a common choice for application in the oxygen electrode.1 The popularity of LSM based electrodes is mainly due to the LSM's high electronic conductivity, the material's good chemical stability and thermal compatibility with other cell materials and last, but not least, the electrocatalytic activity of LSM towards the oxygen evolution reaction (OER) and the oxygen reduction reactions (ORR).1,2 The complex defect chemistry of LSM and the materials electrocatalytic properties has been investigated and discussed for long, and it is well-established that the interplay between the electrical polarization and the LSM's electronic structure strongly influences the electrocatalytic properties of the material. However, extensive experimental studies of this interplay at realistic operating conditions, i.e operando studies, have been scarce.From earlier experimental work it is known, that the creation of oxygen vacancies and accompanying charge compensation mechanism is relevant for the electrocatalytic properties of LSM electrodes, as oxygen vacancies are formed during the cathodic polarization of the electrodes. Hammouche et al.3 concluded from electrochemical characterization and thermogravimetry that the electrocatalytic properties of LSM for reduction of oxygen were closely related to the generation of oxide vacancies inside the material. Concordingly the highest electrocatalytic activity was observed for LSM50, which had the maximum level of Sr dopant, and thus the highest level of oxygen vacancies, of the investigated compounds.3 Lee et al. 4 used in situ XPS and electrochemical studies to prove that the cathodic polarization decreased the Mn oxidation state and led to formation o...

show abstract

Section: Discussionmentioning

confidence: 70%

The Effect of Electrical Polarization on Electronic Structure in LSM Electrodes: An Operando XAS, RIXS and XES Study

Traulsen

Carvalho

Zielke

et al. 2017

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…Once the conditioning is complete and the catalysts reach stable performance, the surface is still very likely undergoing repeated oxidation and reduction cycles, but without any further structure modification. Several authors clearly showed that under CPO reaction conditions, the catalyst surface switches between an oxidized and a reduced state, at least when a dry and steam reforming step follows a complete methane oxidation stage [19,[62][63][64]. Specifically, at the lower temperature, when no reaction or just the total methane oxidation occur, syngas concentration is negligible or small; at this conditions, we expect the metallic catalyst to be in an oxidized state.…”

Section: Comparison With Conditioning Resultsmentioning

confidence: 91%

Partial oxidation of methane on Rh/ZrO2 and Rh/Ce–ZrO2 on monoliths: Catalyst restructuring at reaction conditions

Scarabello

Nogare

Canu

et al. 2015

Applied Catalysis B: Environmental

View full text Add to dashboard Cite

“…Fluorescent m-XAS has also been used to image an individual NiO x /Ce 2 Zr 2 O y catalyst particle used in syngas production, enabling identification of the active Ni/Ce 2 Zr 2 O 7 phase, and its spatial discrimination from inactive NiO/Ce 2 Zr 2 O 8 . [76] Scanning XAS microtomography offers a complementary approach, [77] in which instead of scanning a (micro)focussed X-ray beam across the catalyst, a position sensitive detector provides simultaneous full-field imaging across a section of the entire reactor bed as the incident X-ray energy is varied. This method provides the local chemical/electronic environment of selected elements with ,100 nm resolution.…”

Section: Operando Liquid and Gas Phase Xasmentioning

confidence: 99%

Active Site Elucidation in Heterogeneous Catalysis via In Situ X-Ray Spectroscopies

Lee¹

2012

Aust. J. Chem.

View full text Add to dashboard Cite

Nanostructured heterogeneous catalysts will play a key role in the development of robust artificial photosynthetic systems for water photooxidation and CO 2 photoreduction. Identifying the active site responsible for driving these chemical transformations remains a significant barrier to the design of tailored catalysts, optimized for high activity, selectivity, and lifetime. This highlight reveals how select recent breakthroughs in the application of in situ surface and bulk X-ray spectroscopies are helping to identify the active catalytic sites in a range of liquid and gas phase chemistry.

show abstract

Catalysts at work: From integral to spatially resolved X-ray absorption spectroscopy

Cited by 87 publications

References 81 publications

The Effect of Electrical Polarization on Electronic Structure in LSM Electrodes: An Operando XAS, RIXS and XES Study

The Effect of Electrical Polarization on Electronic Structure in LSM Electrodes: An Operando XAS, RIXS and XES Study

Partial oxidation of methane on Rh/ZrO2 and Rh/Ce–ZrO2 on monoliths: Catalyst restructuring at reaction conditions

Active Site Elucidation in Heterogeneous Catalysis via In Situ X-Ray Spectroscopies

Contact Info

Product

Resources

About