Tuning the thermodynamic onset potential of electrocatalytic O2 reduction reaction by synthetic iron–porphyrin complexes

2015 ◽  
Vol 51 (49) ◽  
pp. 10010-10013 ◽  
Author(s):  
Sk Amanullah ◽  
Pradip Kumar Das ◽  
Subhra Samanta ◽  
Abhishek Dey
Keyword(s):  
Reduction Reaction ◽  
Iron Porphyrin ◽  
Onset Potential ◽  
Porphyrin Ligand ◽  
O2 Reduction ◽  
Iron Porphyrin Complexes

A porphyrin ligand with two β-pyrrolic electron withdrawing ester groups is synthesized and its Co complex is crystallographically characterized.

Effect of axial ligands on electronic structure and O2 reduction by iron porphyrin complexes: Towards a quantitative understanding of the "push effect"

2015 ◽  
Vol 19 (01-03) ◽  
pp. 92-108 ◽  
Author(s):  
Subhra Samanta ◽  
Pradip Kumar Das ◽  
Sudipta Chatterjee ◽  
Abhishek Dey
Keyword(s):  
Electronic Structure ◽  
Active Sites ◽  
Reduction Reaction ◽  
Axial Ligand ◽  
Iron Porphyrin ◽  
Axial Ligands ◽  
O2 Reduction ◽  
Thiolate Complexes ◽  
Quantitative Understanding ◽  
Iron Porphyrin Complexes

Axial ligands play a dominating role in determining the electronic structure and reactivity of iron porphyrin active sites and synthetic models. Several properties unique to the cysteine bound heme enzyme, cytochrome P450, is attributed to the "push effect" of the thiolate axial ligand. In this mini-review the ground state electronic structure of iron porphyrins with imidazole, phenolate and thiolate complexes, derived using a combination of spectroscopy and DFT calculations, are discussed. The differences in kinetics and selectivity of oxygen reduction reaction (ORR), catalyzed by these iron porphyrin complexes with different axial ligands, help elucidate the varying push effects of the different axial ligands on oxygen activation by ferrous porphyrin. The spectroscopic and kinetic data help to develop a quantitative understanding of the "push effect" and, in particular, the electrostatic and covalent contributions to it.

O2 Reduction Reaction by Biologically Relevant Anionic Ligand Bound Iron Porphyrin Complexes

2013 ◽  
Vol 52 (22) ◽  
pp. 12963-12971 ◽  
Author(s):  
Subhra Samanta ◽  
Pradip Kumar Das ◽  
Sudipta Chatterjee ◽  
Kushal Sengupta ◽  
Biswajit Mondal ◽  
...  
Keyword(s):  
Reduction Reaction ◽  
Iron Porphyrin ◽  
Biologically Relevant ◽  
Anionic Ligand ◽  
O2 Reduction ◽  
Iron Porphyrin Complexes

scholarly journals Hybrids of Reduced Graphene Oxide Aerogel and CNT for Electrochemical O2 Reduction

Catalysts ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1404
Author(s):  
Javier Hernández-Ferrer ◽  
Ana M. Benito ◽  
Wolfgang K. Maser ◽  
Enrique García-Bordejé
Keyword(s):  
Oxygen Reduction ◽  
Reduction Reaction ◽  
Onset Potential ◽  
Reduced Graphene ◽  
O2 Reduction ◽  
Electrocatalytic Oxygen Reduction ◽  
Fe Nanoparticles ◽  
Reduced Graphene Oxide Aerogel ◽  
Electron Reduction ◽  
Hybrid Carbon

Carbon nanotubes (CNTs), graphene aerogels (GAs), and their hybrid (CNT-GA) prepared by hydrothermal treatment were tested in the electrocatalytic oxygen reduction reaction (ORR). The importance of porous structure derived from the combination of mesoporosity coming from CNTs with macroporosity stemming from GAs was evidenced because the hybrid carbon material exhibited synergistic performance in terms of kinetic current and onset potential. Different electrocatalysts were prepared based on these hybrids doped with nitrogen using different precursors and also supporting Fe nanoparticles. N-doped carbon hybrids showed higher electrocatalytic activity than their undoped counterparts. Nevertheless, both doped and undoped materials provided a mixed two and four electron reduction. On the other hand, the addition of a Fe precursor and phenanthroline to the CNT-GA allowed preparing an N-doped hybrid containing Fe nanoparticles which favored the 4-electron oxygen reduction to water, thus being an excellent candidate as a structured cathode in fuel cells.

Concerted Proton–Electron Transfer in Electrocatalytic O2 Reduction by Iron Porphyrin Complexes: Axial Ligands Tuning H/D Isotope Effect

2015 ◽  
Vol 54 (5) ◽  
pp. 2383-2392 ◽  
Author(s):  
Sudipta Chatterjee ◽  
Kushal Sengupta ◽  
Subhra Samanta ◽  
Pradip Kumar Das ◽  
Abhishek Dey
Keyword(s):  
Electron Transfer ◽  
Isotope Effect ◽  
Iron Porphyrin ◽  
Axial Ligands ◽  
O2 Reduction ◽  
Iron Porphyrin Complexes

scholarly journals Influence of the distal guanidine group on the rate and selectivity of O2 reduction by iron porphyrin

2019 ◽  
Vol 10 (42) ◽  
pp. 9692-9698 ◽  
Author(s):  
Arnab Ghatak ◽  
Snehadri Bhakta ◽  
Sarmistha Bhunia ◽  
Abhishek Dey
Keyword(s):  
Reduction Reaction ◽  
Iron Porphyrin ◽  
Iron Porphyrins ◽  
Guanidine Group ◽  
O2 Reduction

The O2 reduction reaction (ORR) catalysed by iron porphyrins with covalently attached pendant guanidine groups is reported.

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>

Aliphatic hydroxylation catalyzed by iron porphyrin complexes

1983 ◽  
Vol 105 (20) ◽  
pp. 6243-6248 ◽  
Author(s):  
John T. Groves ◽  
Thomas E. Nemo
Keyword(s):  
Iron Porphyrin ◽  
Iron Porphyrin Complexes

scholarly journals Superior FexN electrocatalyst derived from 1,1′-diacetylferrocene for oxygen reduction reaction in alkaline and acidic media

2020 ◽  
Vol 9 (1) ◽  
pp. 843-852
Author(s):  
Hunan Jiang ◽  
Jinyang Li ◽  
Mengni Liang ◽  
Hanpeng Deng ◽  
Zuowan Zhou
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Current Density ◽  
Active Sites ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Acidic Media ◽  
Onset Potential ◽  
Acidic And Alkaline Media ◽  
The Stability

AbstractAlthough Fe–N/C catalysts have received increasing attention in recent years for oxygen reduction reaction (ORR), it is still challenging to precisely control the active sites during the preparation. Herein, we report FexN@RGO catalysts with the size of 2–6 nm derived from the pyrolysis of graphene oxide and 1,1′-diacetylferrocene as C and Fe precursors under the NH3/Ar atmosphere as N source. The 1,1′-diacetylferrocene transforms to Fe3O4 at 600°C and transforms to Fe3N and Fe2N at 700°C and 800°C, respectively. The as-prepared FexN@RGO catalysts exhibited superior electrocatalytic activities in acidic and alkaline media compared with the commercial 10% Pt/C, in terms of electrochemical surface area, onset potential, half-wave potential, number of electrons transferred, kinetic current density, and exchange current density. In addition, the stability of FGN-8 also outperformed commercial 10% Pt/C after 10000 cycles, which demonstrates the as-prepared FexN@RGO as durable and active ORR catalysts in acidic media.

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