X-ray absorption spectroscopy of Ba- and Cs-promoted Ru/mesoporous carbon catalysts for long-term ammonia synthesis under intermittent operation conditions

2020 ◽  
Vol 4 (2) ◽  
pp. 832-842 ◽  
Author(s):  
Masayasu Nishi ◽  
Shih-Yuan Chen ◽  
Hideyuki Takagi
Keyword(s):  
Absorption Spectroscopy ◽  
Active Sites ◽  
Ammonia Synthesis ◽  
Mesoporous Carbons ◽  
X Ray ◽  
Operation Conditions ◽  
Intermittent Operation ◽  
Carbon Catalysts ◽  
X Ray Absorption

The active sites of Ba- and Cs-promoted Ru/mesoporous carbons were examined by advanced techniques, especially X-ray absorption spectroscopy, and correlated to their activities in long-term ammonia synthesis under intermittent operation conditions.

scholarly journals Partial methanol oxidation over copper: Active sites observed by means of in situ X-ray absorption spectroscopy

2000 ◽  
Vol 2 (15) ◽  
pp. 3473-3481 ◽  
Author(s):  
Th. Schedel-Niedrig ◽  
M. Hävecker ◽  
A. Knop-Gericke ◽  
R. Schlögl
Keyword(s):  
Methanol Oxidation ◽  
Absorption Spectroscopy ◽  
Active Sites ◽  
X Ray ◽  
X Ray Absorption

scholarly journals Unveiling the Degradation Nature of Pt/NbOx/C Catalysts for Oxygen Reduction Reaction via in situ X-ray Absorption Spectroscopy

2021 ◽  
Author(s):  
Ershuai Liu ◽  
Qingying Jia ◽  
Jun Yang ◽  
Kai Sun ◽  
Li Jiao ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Absorption Spectroscopy ◽  
Reduction Reaction ◽  
X Ray ◽  
Orr Activity ◽  
X Ray Absorption

Among various metal nanoparticles supported on metal oxide (MMO) catalysts, the Pt/NbOx/C system has promising oxygen reduction reaction (ORR) activity as cathode for proton exchange membrane fuel cells (PEMFCs). Herein, we study a series of Pt/NbOx/C catalysts with tunable structural and electronic properties via physical vapor deposition and unravel the nature of metal and metal oxide interaction (MMOI) by characterizing this system under reactive conditions. By conducting in situ X-ray absorption spectroscopy (XAS) experiments, we demonstrate the Pt preferably interacts with O but not Nb in the Pt/NbOx/C system and such Pt-O interaction benefits the ORR activity via electronic effect rather than strain effect. We also provide clear evidence for the formation of metallic Nb phase at the early stage of PEMFC operation and identify severe particle growth of Pt after long-term PEMFC operation. These findings deepen our understanding of the degradation mechanism of MMO catalysts during long-term PEMFC operation.

Probing Active Sites in CuxPdy Cluster Catalysts by Machine-Learning-Assisted X-ray Absorption Spectroscopy

2021 ◽  
Author(s):  
Yang Liu ◽  
Avik Halder ◽  
Soenke Seifert ◽  
Nicholas Marcella ◽  
Stefan Vajda ◽  
...  
Keyword(s):  
Machine Learning ◽  
Absorption Spectroscopy ◽  
Active Sites ◽  
X Ray ◽  
X Ray Absorption

scholarly journals Selenium Valence-to-Core X-ray Emission Spectroscopy and Kβ HERFD X-ray Absorption Spectroscopy as Complementary Probes of Chemical and Electronic Structure

2021 ◽  
Author(s):  
Justin T. Henthorn ◽  
Serena DeBeer
Keyword(s):  
Absorption Spectroscopy ◽  
Emission Spectroscopy ◽  
Active Sites ◽  
Structural Information ◽  
Oxidation States ◽  
Geochemical Processes ◽  
X Ray ◽  
Fe Oxidation ◽  
Experimental Resolution ◽  
X Ray Absorption

Selenium X-ray absorption spectroscopy (XAS) has found widespread use in investigations of Se-containing materials, geochemical processes, and biological active sites. In contrast to sulfur Kβ X-ray emission spectroscopy (XES), which has been found to contain electronic and structural information complementary to S XAS, Se Kβ XES remains comparatively under-explored. Herein, we present the first Se Valence-to-Core (VtC) XES studies of reduced Se-containing compounds and FeSe dimers. Se VtC XES is found to be sensitive to changes in covalent Se bonding interactions (Se–Se/Se–C/Se–H bonding) while relatively insensitive to changes in Fe oxidation states as selenide bridges in FeSe dimers ([Fe2Se2]2+ vs [Fe2Se2]+). Contrastingly, Se Kβ HERFD XAS is demonstrated to be quite sensitive to changes in Fe-oxidation state, with Se Kβ HERFD XAS demonstrating experimental resolution equivalent to K𝛼 HERFD XAS. Additionally, computational studies reveal both Se VtC XES and XAS to be sensitive to selenium protonation in FeSe complexes.

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