Electropolymerization ofp-phenylenediamine on Pt-electrode from aqueous acidic solution: Kinetics, mechanism, electrochemical studies, and characterization of the polymer obtained

2010 ◽  
Vol 117 (2) ◽  
pp. 943-952 ◽  
Author(s):  
S. M. Sayyah ◽  
S. S. Abd El-Rehim ◽  
M. M. El-Deeb ◽  
S. M. Kamal ◽  
R. E. Azooz
Keyword(s):  
Acidic Solution ◽  
Electrochemical Studies ◽  
Pt Electrode ◽  
Aqueous Acidic Solution ◽  
Solution Kinetics

A Pyridinic Fe-N4 Macrocycle Effectively Models the Active Sites in Fe/N-Doped Carbon Electrocatalysts

2020 ◽  
Author(s):  
Travis Marshall-Roth ◽  
Nicole J. Libretto ◽  
Alexandra T. Wrobel ◽  
Kevin Anderton ◽  
Nathan D. Ricke ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Catalytic Properties ◽  
Reduction Reaction ◽  
Iron Phthalocyanine ◽  
Electrochemical Studies ◽  
Onset Potential ◽  
Nitrogen Doped Carbon ◽  
Iron Active Sites

Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum in fuel cells, but their active site structures are poorly understood. A leading postulate is that iron active sites in this class of materials exist in an Fe-N<sub>4</sub> pyridinic ligation environment. Yet, molecular Fe-based catalysts for the oxygen reduction reaction (ORR) generally feature pyrrolic coordination and pyridinic Fe-N<sub>4</sub> catalysts are, to the best of our knowledge, non-existent. We report the synthesis and characterization of a molecular pyridinic hexaazacyclophane macrocycle, (phen<sub>2</sub>N<sub>2</sub>)Fe, and compare its spectroscopic, electrochemical, and catalytic properties for oxygen reduction to a prototypical Fe-N-C material, as well as iron phthalocyanine, (Pc)Fe, and iron octaethylporphyrin, (OEP)Fe, prototypical pyrrolic iron macrocycles. N 1s XPS signatures for coordinated N atoms in (phen<sub>2</sub>N<sub>2</sub>)Fe are positively shifted relative to (Pc)Fe and (OEP)Fe, and overlay with those of Fe-N-C. Likewise, spectroscopic XAS signatures of (phen<sub>2</sub>N<sub>2</sub>)Fe are distinct from those of both (Pc)Fe and (OEP)Fe, and are remarkably similar to those of Fe-N-C with compressed Fe–N bond lengths of 1.97 Å in (phen<sub>2</sub>N<sub>2</sub>)Fe that are close to the average 1.94 Å length in Fe-N-C. Electrochemical studies establish that both (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe have relatively high Fe(III/II) potentials at ~0.6 V, ~300 mV positive of (OEP)Fe. The ORR onset potential is found to directly correlate with the Fe(III/II) potential leading to a ~300 mV positive shift in the onset of ORR for (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe relative to (OEP)Fe. Consequently, the ORR onset for (phen<sub>2</sub>N<sub>2</sub>)Fe and (Pc)Fe is within 150 mV of Fe-N-C. Unlike (OEP)Fe and (Pc)Fe, (phen<sub>2</sub>N<sub>2</sub>)Fe displays excellent selectivity for 4-electron ORR with <4% maximum H<sub>2</sub>O<sub>2</sub> production, comparable to Fe-N-C materials. The aggregate spectroscopic and electrochemical data establish (phen<sub>2</sub>N<sub>2</sub>)Fe as a pyridinic iron macrocycle that effectively models Fe-N-C active sites, thereby providing a rich molecular platform for understanding this important class of catalytic materials.<p><b></b></p>

scholarly journals Achieving highly efficient and selective cesium extraction using 1,3-di-octyloxycalix[4]arene-crown-6 in n-octanol based solvent system: experimental and DFT investigation

RSC Advances ◽  
2021 ◽  
Vol 11 (35) ◽  
pp. 21323-21331
Author(s):  
Kankan Patra ◽  
Biswajit Sadhu ◽  
Arijit Sengupta ◽  
C. B. Patil ◽  
R. K. Mishra ◽  
...  
Keyword(s):  
Fission Product ◽  
Acidic Solution ◽  
Solvent System ◽  
Selective Extraction ◽  
Separation Scheme ◽  
Highly Efficient ◽  
Aqueous Acidic Solution

Separation scheme was developed for selective extraction of long-lived fission product 137Cs using substituted calix crown 6 ether from aqueous acidic solution.

Fine-grained weathering products in waste disposal from two sulphide mines in the northern Apennines, Italy

Clay Minerals ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 423-433 ◽  
Author(s):  
E. Dinelli ◽  
N. Morandi ◽  
F. Tateo
Keyword(s):  
Acidic Solution ◽  
Chemical Characterization ◽  
Northern Apennines ◽  
The Other ◽  
Blue Colour ◽  
Fine Grained ◽  
Surrounding Environment ◽  
Waste Rock Piles ◽  
Cu And Zn

AbstractFrom mineralogical and chemical characterization of two waste-rock piles from Vigonzano and Libiola sulphide mines in the northern Apennines, two types of fine-grained weathering products were recognized, One, from the Vigonzano mine, has a typical blue colour and consists of the Cu-Al sulphate of the woodwardite group. Its formation is related to an alkaline geochemical barrier, it is rather stable in acidic solution, and it controls Cu and Zn dispersion in the surrounding environment. The other group of sediments has a typical ochreous colour. Vigonzano samples consist mostly of goethite, whereas ferrihydrite is abundant in the Libiola sample. The ochreous sediments are enriched in Co, As, Mo, Se and Mn, thus significantly reducing the potential environmental hazard of the site, whereas solubility tests indicated possible problems due to AI dissolution at Libiola.

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