Geometric and Electronic Structure of α-Oxygen Sites in Mn-ZSM-5 Zeolites

Radu, D. C.; Glatzel, Pieter; Gloter, Alexandre; Stéphan, Odile; Weckhuysen, Bert M.; Groot, Frank M. F. de

doi:10.1021/jp802915k

Cited by 26 publications

(19 citation statements)

References 58 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recently, the presence of an α-O site in Mn-ZSM-5 was suggested after N 2 O treatment, similar to Fe-ZSM-5. This so called α-O results in the formation of an absorption band in the UV-vis spectra around 18 500 cm −1 , and was suggested to be involved in the N 2 O decomposition in Mn-ZSM-5 141. No reactivity towards hydrocarbons is thus far reported for this species and as is the case for Fe-ZSM-5, the α-O in Mn-ZSM-5 cannot be formed with O 2 .…”

Section: Activated Oxygen On Tmi and Its Reactivitymentioning

confidence: 99%

Transition-Metal Ions in Zeolites: Coordination and Activation of Oxygen

et al. 2010

View full text Add to dashboard Cite

Zeolites containing transition metal ions (TMI) often show promising activity as heterogeneous catalysts in pollution abatement and selective oxidation reactions. In this paper, two aspects of research on the TMI Cu, Co and Fe in zeolites are discussed: (i) coordination to the lattice and (ii) activated oxygen species. At low loading, TMI preferably occupy exchange sites in six-membered oxygen rings (6MR) where the TMI preferentially coordinate with the oxygen atoms of Al tetrahedra. High TMI loadings result in a variety of TMI species formed at the zeolite surface. Removal of the extra-lattice oxygens during high temperature pretreatments can result in auto-reduction. Oxidation of reduced TMI sites often results in the formation of highly reactive oxygen species. In Cu-ZSM-5, calcination with O 2 results in the formation of a species, which was found to be a crucial intermediate in both the direct decomposition of NO and N 2 O and the selective oxidation of methane into methanol. An activated oxygen species, called α-oxygen, is formed in Fe-ZSM5 and reported to be the active site in the partial oxidation of methane and benzene into methanol and phenol, respectively. However, this reactive α-oxygen can only be formed with N 2 O, not with O 2 . O 2 activated Co intermediates in Faujasite (FAU) zeolites can selectively oxidize α-pinene and epoxidize styrene. In Co-FAU, Co III superoxo and peroxo complexes are suggested to be the active cores, whereas in Cu and Fe-ZSM-5 various monomeric and dimeric sites have been proposed, but no consensus has been obtained. Very recently, the active site in Cu-ZSM-5 was identified as a bent [Cu-O-Cu] 2+ core (Proc. Natl. Acad. Sci. USA 2009, 106, 18908-18913). Overall, O 2 activation depends on the interplay of structural factors such as type of zeolite, size of the channels and cages and chemical factors such as Si/Al ratio and the nature, charge and distribution of the charge balancing cations. The presence of several different TMI sites hinders the direct study of the spectroscopic features of the active site. Spectroscopic techniques capable of selectively probing these sites, even if they only constitute a minor fraction of the total amount of TMI sites, are thus required. Fundamental knowledge of the geometric and electronic structure of the reactive active site can help in the design of novel selective oxidation catalysts.

show abstract

Section: Activated Oxygen On Tmi and Its Reactivitymentioning

confidence: 99%

Transition-Metal Ions in Zeolites: Coordination and Activation of Oxygen

et al. 2010

View full text Add to dashboard Cite

show abstract

“…[16,17] A number of detailed L edge spectra and charge transfer multiplet analysis has been applied to catalytic systems, for example Fischer-Tropsch catalysts, [12] Fe/ZSM-5 systems [18] and Mn/ZSM-5 systems. [19]…”

Section: The Interpretation Of Soft Xas Spectra and Chemical Contrastmentioning

confidence: 99%

In‐situ Scanning Transmission X‐Ray Microscopy of Catalytic Solids and Related Nanomaterials

et al. 2010

Self Cite

View full text Add to dashboard Cite

The present status of in-situ scanning transmission X-ray microscopy (STXM) is reviewed, with an emphasis on the abilities of the STXM technique in comparison with electron microscopy. The experimental aspects and interpretation of X-ray absorption spectroscopy (XAS) are briefly introduced and the experimental boundary conditions that determine the potential applications for in-situ XAS and in-situ STXM studies are discussed. Nanoscale chemical imaging of catalysts under working conditions is outlined using cobalt and iron Fischer-Tropsch catalysts as showcases. In the discussion, we critically compare STXM-XAS and STEM-EELS (scanning transmission electron microscopy-electron energy loss spectroscopy) measurements and indicate some future directions of in-situ nanoscale imaging of catalytic solids and related nanomaterials.

show abstract

“…Furthermore, with the same experimental setup XES can be measured, which allows one to probe the occupied states within the valence band (12). In situ HERFD XAS or XES experiments have been previously carried out to study the catalytic reaction at the surface of noble metals (11,(13)(14)(15)(16), zeolites (17), and metal organic frameworks (18). Thus far, no such in situ experiments have been performed to directly track the changes of the electronic structure of a solid and its electrochemical activity toward CO 2 .…”

mentioning

confidence: 99%

High-energy resolution X-ray absorption and emission spectroscopy reveals insight into unique selectivity of La-based nanoparticles for CO₂

Hirsch

Kvashnina

Luo

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

The lanthanum-based materials, due to their layered structure and f-electron configuration, are relevant for electrochemical application. Particularly, La 2 O 2 CO 3 shows a prominent chemoresistive response to CO 2 . However, surprisingly less is known about its atomic and electronic structure and electrochemically significant sites and therefore, its structure-functions relationships have yet to be established. Here we determine the position of the different constituents within the unit cell of monoclinic La 2 O 2 CO 3 and use this information to interpret in situ high-energy resolution fluorescencedetected (HERFD) X-ray absorption near-edge structure (XANES) and valence-to-core X-ray emission spectroscopy (vtc XES). Compared with La(OH) 3 or previously known hexagonal La 2 O 2 CO 3 structures, La in the monoclinic unit cell has a much lower number of neighboring oxygen atoms, which is manifested in the whiteline broadening in XANES spectra. Such a superior sensitivity to subtle changes is given by HERFD method, which is essential for in situ studying of the interaction with CO 2 . Here, we study La 2 O 2 CO 3 -based sensors in real operando conditions at 250°C in the presence of oxygen and water vapors. We identify that the distribution of unoccupied La d-states and occupied O p-and La d-states changes during CO 2 chemoresistive sensing of La 2 O 2 CO 3 . The correlation between these spectroscopic findings with electrical resistance measurements leads to a more comprehensive understanding of the selective adsorption at La site and may enable the design of new materials for CO 2 electrochemical applications.C O 2 has become a challenge for our society and we have to develop new materials for its photo/electrocatalysis, chemoresistive sensing, and storage (1-8). Particularly, for the variety of electrochemical applications the selective interaction of CO 2 and charge transfer with solids is in the foreground. At the same time, the interaction of CO 2 with solids in the electrochemical cell or sensing device is rather complex, thus it remains challenging to experimentally identify the key elements determining their selectivity and efficiency. X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) provide complementary information on the electronic structure of materials (9, 10) and on the orbitals participating in the interaction with absorbing molecules (11). High-energy resolution fluorescence-detected (HERFD) XAS probes unoccupied states with a spectral resolution higher than regular XAS. Furthermore, with the same experimental setup XES can be measured, which allows one to probe the occupied states within the valence band (12). In situ HERFD XAS or XES experiments have been previously carried out to study the catalytic reaction at the surface of noble metals (11, 13-16), zeolites (17), and metal organic frameworks (18). Thus far, no such in situ experiments have been performed to directly track the changes of the electronic structure of a solid and its electrochemical activity toward CO 2...

show abstract

Geometric and Electronic Structure of α-Oxygen Sites in Mn-ZSM-5 Zeolites

Cited by 26 publications

References 58 publications

Transition-Metal Ions in Zeolites: Coordination and Activation of Oxygen

Transition-Metal Ions in Zeolites: Coordination and Activation of Oxygen

In‐situ Scanning Transmission X‐Ray Microscopy of Catalytic Solids and Related Nanomaterials

High-energy resolution X-ray absorption and emission spectroscopy reveals insight into unique selectivity of La-based nanoparticles for CO₂

Contact Info

Product

Resources

About

Geometric and Electronic Structure of α-Oxygen Sites in Mn-ZSM-5 Zeolites

Cited by 26 publications

References 58 publications

Transition-Metal Ions in Zeolites: Coordination and Activation of Oxygen

Transition-Metal Ions in Zeolites: Coordination and Activation of Oxygen

In‐situ Scanning Transmission X‐Ray Microscopy of Catalytic Solids and Related Nanomaterials

High-energy resolution X-ray absorption and emission spectroscopy reveals insight into unique selectivity of La-based nanoparticles for CO2

Contact Info

Product

Resources

About

High-energy resolution X-ray absorption and emission spectroscopy reveals insight into unique selectivity of La-based nanoparticles for CO₂