57Fe Mössbauer spectroscopy on disordered crystalline media with Ca-gallogermanate type structure. II. Below the magnetic ordering temperature

1995 ◽  
Vol 96 (1) ◽  
pp. 83-89 ◽  
Author(s):  
D. Barb ◽  
S. Constantinescu ◽  
D. Tarina
Keyword(s):  
Mössbauer Spectroscopy ◽  
Mossbauer Spectroscopy ◽  
57Fe Mössbauer Spectroscopy ◽  
Magnetic Ordering ◽  
Type Structure ◽  
57Fe Mössbauer ◽  
57Fe Mossbauer Spectroscopy ◽  
Mößbauer Spectroscopy ◽  
Magnetic Ordering Temperature

57Fe Mössbauer Spectroscopy Analysis of the System Ho2Fe14B-H*

1992 ◽  
Vol 1 (1) ◽  
pp. 461-469
Author(s):  
B. Malaman ◽  
R. Gérardin ◽  
G. Le Caer ◽  
S. Obbade ◽  
S. Miraglia ◽  
...  
Keyword(s):  
Mössbauer Spectroscopy ◽  
Mossbauer Spectroscopy ◽  
57Fe Mössbauer Spectroscopy ◽  
Spectroscopy Analysis ◽  
57Fe Mössbauer ◽  
57Fe Mossbauer Spectroscopy ◽  
Mößbauer Spectroscopy

scholarly journals Identification of Durable and Non-Durable FeNx Sites in Fe-N-C Materials for Proton Exchange Membrane Fuel Cells

2020 ◽  
Author(s):  
Jingkun Li ◽  
Moulay-Tahar Sougrati ◽  
andrea Zitolo ◽  
James Ablett ◽  
ismail can oguz ◽  
...  
Keyword(s):  
Mössbauer Spectroscopy ◽  
Fuel Cells ◽  
Proton Exchange Membrane ◽  
Mossbauer Spectroscopy ◽  
57Fe Mössbauer Spectroscopy ◽  
Proton Exchange ◽  
Promising Alternative ◽  
57Fe Mössbauer ◽  
57Fe Mossbauer Spectroscopy ◽  
Mößbauer Spectroscopy

While Fe-N-C materials are a promising alternative to platinum for catalyzing oxygen reduction in acidic polymer fuel cells, limited understanding of their operando degradation restricts rational approaches towards improved durability. Here we show that Fe-N-C catalysts initially comprising two distinct FeNx sites (S1 and S2) degrade via the transformation of S1 into iron oxides while the structure and number of S2 were unmodified. Structure-activity correlations drawn from end-of-test 57Fe Mössbauer spectroscopy reveal that both sites initially contribute to the ORR activity but only S2 significantly contributes after 50 h of operation. From in situ 57Fe Mössbauer spectroscopy in inert gas coupled to calculations of the Mössbauer signature of FeNx moieties in different electronic states, we identify S1 to be a high-spin FeN4C12 moiety and S2 a low- or intermediate spin FeN4C10 moiety. These insights lay the ground for rational approaches towards Fe-N-C cathodes with improved durability in acidic fuel cells.<br>

Sign in / Sign up

Export Citation Format

Share Document